Re: [Emc-users] What Would You Suggest?

[John Dammeyer]

Sigh...  A web link or two would be more helpful than just a comment.

> From: Robin Szemeti via Emc-users [mailto:emc-users@lists.sourceforge.net]
> 
> Sigh ...
> 
> " Perhaps you can find some and post those that do show flat torque up to a
> 'corner speed'?"  ... all ... every single one,  when connected to a
> current limited driver.
> 
> On Sun, 6 Feb 2022 at 00:45, John Dammeyer  wrote:
> 
> > No.  The motors are designed to handle N amperes although they get quite
> > warm that should be a 24/7 rating. Because they get so warm many drivers
> > back the current off when the motors have been idle for a period of time.
> >
> > Let's take a step backwards with a long explanation.   When I first sized
> > the motor for the knee mill I tested how much torque was required to
> > overcome 'static' friction by attaching a bar and adding weight until it
> > started turning.  The 'kinetic' friction is always less so as a rule of
> > thumb using twice that experimentally determined torque value was a good
> > starting point.
> >
> > But you can also use math if you know the weight of the table you are
> > lifting.  I didn't but if I guess at 325 lbs with a 1" lead 4 TPI ACME
> > leadscrew with Bronze nut
> > https://daycounter.com/Calculators/Lead-Screw-Force-Torque-Calculator.phtml
> > I get pretty close to the value I determined experimentally which is 600
> > oz-in
> >
> > So choosing a 600 oz-in motor for roughly 600 oz-in torque determined
> > experimentally looked like it would work.  Then looking at the torque curve
> > I determined that to get that 600 oz-in torque at the desired speed would
> > require a 3:1 reduction belt drive to get the 600 oz-in at target speed.
> >  I used a Gecko Drive with a 60VDC power supply and a motor with 6.5A,
> > 2.2mH rating.  The calculator here
> > https://daycounter.com/Calculators/Stepper-Motor-Calculator.phtml
> > shows max 10.5 RPS or 630 RPM and therefore with 3:1 reduction I'd be
> > looking at 210 RPM into the lead screw drive.
> >
> > With a 4 TPI drive that means 52 ipm of table motion.  In reality the best
> > I got was 15 ipm before the motor locked up.   Click on the torque curve
> > and at 630RPM it's about 1.5NM which is 33% of the 4.5NM rating (640 oz-in).
> >
> > https://www.automationtechnologiesinc.com/products-page/nema-34/nema-34-640-oz-in-stepper-motor-kl34h280-45-8b-dual-
> shaft
> >
> > Long story short is that I updated to a 1200 oz-in motor and had reliable
> > motion with a Gecko Drive and 60VDC at 25 ipm from LCNC or MACH3.  This
> > moved the torque up but not really the top speed since now this motor has
> > 6mH rather than 2.2mH with a 6A drive rating.  I might have been better to
> > have changed the reduction belt drive to 2:1 or less.
> >
> > Back to that pesky power rating.  At 60V the motor calculator suggests
> > it's drawing 380W.  Change the voltage to 120VDC and with the same current
> > we get twice the RPM and twice the power 750W.  So then theoretically I
> > should be able to get 50 ipm reliably if I had a driver that could handle
> > 120VDC and if the motor winding insulation was rated for that voltage.
> >
> > Instead I ball-parked an AC Servo motor, 750W, 3000 RPM, 3.5NM (495 oz-in)
> > and max 2000 RPM as the solution.  This drive runs off 220VAC and is rated
> > at 3A with a peak torque of 10.5NM.  With 3:1 and that 495 oz-in torque
> > value all the way up to 2000 RPM (667 shaft RPM or 167 ipm) I can
> > comfortably run this motor at 150 ipm without it ever faulting.  That's 6x
> > the stepper motor speed.
> >
> > What that suggests is what everyone already knows is that stepper torque
> > falls off badly at higher RPM even with a higher voltage but they are
> > really good at low speeds.  Change things to get more torque and if the
> > inductance goes up the torque at low RPM is there but not at the high RPM.
> > Unless your driver and motor can handle a correspondingly higher voltage.
> >
> > But look around and most drivers for steppers are in the 24V to 80V range
> > so with steppers,  motor power in watts means nothing if you can't get the
> > voltage up.   Now if you go 1:1 then 0.25"/200 results in a resolution of
> > 0.00125".  Torque falls off to 50% with half stepping and micro-stepping
> > results in a 70.7% reduction in max torque.  And Micro-stepping also can
> > require as many as 4 steps before static torque is overcome and the motor
> > shaft turning.  That's just due to the nature of the current waveform so
> > for accuracy you must design for full st

Re: [Emc-users] What Would You Suggest?

[John Dammeyer]

 pulse width.  And that's 
because too much winding current and induced magnetic field will damage the 
magnets in the motor.

So I stand by my original position that the torque curve verses RPM is way more 
important that power which no one publishes because it's not useful.

John






> -Original Message-
> From: Thaddeus Waldner [mailto:thadw...@gmail.com]
> Sent: February-05-22 8:26 PM
> To: Enhanced Machine Controller (EMC)
> Subject: Re: [Emc-users] What Would You Suggest?
> 
> 
> 
> > On Feb 5, 2022, at 6:48 PM, John Dammeyer  wrote:
> >
> > No.  The motors are designed to handle N amperes although they get quite 
> > warm that should be a 24/7 rating. Because they get so
> warm many drivers back the current off when the motors have been idle for a 
> period of time.
> 
> Yes, N amperes.  Is that not the flat part of the graph?
> 
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Re: [Emc-users] What Would You Suggest?

[Thaddeus Waldner]

> On Feb 5, 2022, at 6:48 PM, John Dammeyer  wrote:
> 
> No.  The motors are designed to handle N amperes although they get quite warm 
> that should be a 24/7 rating. Because they get so warm many drivers back the 
> current off when the motors have been idle for a period of time. 

Yes, N amperes.  Is that not the flat part of the graph? 

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Re: [Emc-users] What Would You Suggest?

[Robin Szemeti via Emc-users]

Sigh ...

" Perhaps you can find some and post those that do show flat torque up to a
'corner speed'?"  ... all ... every single one,  when connected to a
current limited driver.

On Sun, 6 Feb 2022 at 00:45, John Dammeyer  wrote:

> No.  The motors are designed to handle N amperes although they get quite
> warm that should be a 24/7 rating. Because they get so warm many drivers
> back the current off when the motors have been idle for a period of time.
>
> Let's take a step backwards with a long explanation.   When I first sized
> the motor for the knee mill I tested how much torque was required to
> overcome 'static' friction by attaching a bar and adding weight until it
> started turning.  The 'kinetic' friction is always less so as a rule of
> thumb using twice that experimentally determined torque value was a good
> starting point.
>
> But you can also use math if you know the weight of the table you are
> lifting.  I didn't but if I guess at 325 lbs with a 1" lead 4 TPI ACME
> leadscrew with Bronze nut
> https://daycounter.com/Calculators/Lead-Screw-Force-Torque-Calculator.phtml
> I get pretty close to the value I determined experimentally which is 600
> oz-in
>
> So choosing a 600 oz-in motor for roughly 600 oz-in torque determined
> experimentally looked like it would work.  Then looking at the torque curve
> I determined that to get that 600 oz-in torque at the desired speed would
> require a 3:1 reduction belt drive to get the 600 oz-in at target speed.
>  I used a Gecko Drive with a 60VDC power supply and a motor with 6.5A,
> 2.2mH rating.  The calculator here
> https://daycounter.com/Calculators/Stepper-Motor-Calculator.phtml
> shows max 10.5 RPS or 630 RPM and therefore with 3:1 reduction I'd be
> looking at 210 RPM into the lead screw drive.
>
> With a 4 TPI drive that means 52 ipm of table motion.  In reality the best
> I got was 15 ipm before the motor locked up.   Click on the torque curve
> and at 630RPM it's about 1.5NM which is 33% of the 4.5NM rating (640 oz-in).
>
> https://www.automationtechnologiesinc.com/products-page/nema-34/nema-34-640-oz-in-stepper-motor-kl34h280-45-8b-dual-shaft
>
> Long story short is that I updated to a 1200 oz-in motor and had reliable
> motion with a Gecko Drive and 60VDC at 25 ipm from LCNC or MACH3.  This
> moved the torque up but not really the top speed since now this motor has
> 6mH rather than 2.2mH with a 6A drive rating.  I might have been better to
> have changed the reduction belt drive to 2:1 or less.
>
> Back to that pesky power rating.  At 60V the motor calculator suggests
> it's drawing 380W.  Change the voltage to 120VDC and with the same current
> we get twice the RPM and twice the power 750W.  So then theoretically I
> should be able to get 50 ipm reliably if I had a driver that could handle
> 120VDC and if the motor winding insulation was rated for that voltage.
>
> Instead I ball-parked an AC Servo motor, 750W, 3000 RPM, 3.5NM (495 oz-in)
> and max 2000 RPM as the solution.  This drive runs off 220VAC and is rated
> at 3A with a peak torque of 10.5NM.  With 3:1 and that 495 oz-in torque
> value all the way up to 2000 RPM (667 shaft RPM or 167 ipm) I can
> comfortably run this motor at 150 ipm without it ever faulting.  That's 6x
> the stepper motor speed.
>
> What that suggests is what everyone already knows is that stepper torque
> falls off badly at higher RPM even with a higher voltage but they are
> really good at low speeds.  Change things to get more torque and if the
> inductance goes up the torque at low RPM is there but not at the high RPM.
> Unless your driver and motor can handle a correspondingly higher voltage.
>
> But look around and most drivers for steppers are in the 24V to 80V range
> so with steppers,  motor power in watts means nothing if you can't get the
> voltage up.   Now if you go 1:1 then 0.25"/200 results in a resolution of
> 0.00125".  Torque falls off to 50% with half stepping and micro-stepping
> results in a 70.7% reduction in max torque.  And Micro-stepping also can
> require as many as 4 steps before static torque is overcome and the motor
> shaft turning.  That's just due to the nature of the current waveform so
> for accuracy you must design for full step resolution.
>
> John
>
>
> > -Original Message-
> > From: Thaddeus Waldner [mailto:thadw...@gmail.com]
> > Sent: February-05-22 12:40 PM
> > To: Enhanced Machine Controller (EMC)
> > Subject: Re: [Emc-users] What Would You Suggest?
> >
> > I believe the flat part of the curve is defined by the motor thermal
> limits. Is this correct?
> >
> > > On Feb 5, 2022, at 11:44 AM, John Dammeyer 
> wrote:
> > >
> > > ?All fine and good but

Re: [Emc-users] What Would You Suggest?

[John Dammeyer]

No.  The motors are designed to handle N amperes although they get quite warm 
that should be a 24/7 rating. Because they get so warm many drivers back the 
current off when the motors have been idle for a period of time.  

Let's take a step backwards with a long explanation.   When I first sized the 
motor for the knee mill I tested how much torque was required to overcome 
'static' friction by attaching a bar and adding weight until it started 
turning.  The 'kinetic' friction is always less so as a rule of thumb using 
twice that experimentally determined torque value was a good starting point.  

But you can also use math if you know the weight of the table you are lifting.  
I didn't but if I guess at 325 lbs with a 1" lead 4 TPI ACME leadscrew with 
Bronze nut
https://daycounter.com/Calculators/Lead-Screw-Force-Torque-Calculator.phtml
I get pretty close to the value I determined experimentally which is 600 oz-in

So choosing a 600 oz-in motor for roughly 600 oz-in torque determined 
experimentally looked like it would work.  Then looking at the torque curve I 
determined that to get that 600 oz-in torque at the desired speed would require 
a 3:1 reduction belt drive to get the 600 oz-in at target speed.   I used a 
Gecko Drive with a 60VDC power supply and a motor with 6.5A, 2.2mH rating.  The 
calculator here
https://daycounter.com/Calculators/Stepper-Motor-Calculator.phtml
shows max 10.5 RPS or 630 RPM and therefore with 3:1 reduction I'd be looking 
at 210 RPM into the lead screw drive.  

With a 4 TPI drive that means 52 ipm of table motion.  In reality the best I 
got was 15 ipm before the motor locked up.   Click on the torque curve and at 
630RPM it's about 1.5NM which is 33% of the 4.5NM rating (640 oz-in).
https://www.automationtechnologiesinc.com/products-page/nema-34/nema-34-640-oz-in-stepper-motor-kl34h280-45-8b-dual-shaft

Long story short is that I updated to a 1200 oz-in motor and had reliable 
motion with a Gecko Drive and 60VDC at 25 ipm from LCNC or MACH3.  This moved 
the torque up but not really the top speed since now this motor has 6mH rather 
than 2.2mH with a 6A drive rating.  I might have been better to have changed 
the reduction belt drive to 2:1 or less.

Back to that pesky power rating.  At 60V the motor calculator suggests it's 
drawing 380W.  Change the voltage to 120VDC and with the same current we get 
twice the RPM and twice the power 750W.  So then theoretically I should be able 
to get 50 ipm reliably if I had a driver that could handle 120VDC and if the 
motor winding insulation was rated for that voltage.

Instead I ball-parked an AC Servo motor, 750W, 3000 RPM, 3.5NM (495 oz-in) and 
max 2000 RPM as the solution.  This drive runs off 220VAC and is rated at 3A 
with a peak torque of 10.5NM.  With 3:1 and that 495 oz-in torque value all the 
way up to 2000 RPM (667 shaft RPM or 167 ipm) I can comfortably run this motor 
at 150 ipm without it ever faulting.  That's 6x the stepper motor speed.

What that suggests is what everyone already knows is that stepper torque falls 
off badly at higher RPM even with a higher voltage but they are really good at 
low speeds.  Change things to get more torque and if the inductance goes up the 
torque at low RPM is there but not at the high RPM.  Unless your driver and 
motor can handle a correspondingly higher voltage.

But look around and most drivers for steppers are in the 24V to 80V range so 
with steppers,  motor power in watts means nothing if you can't get the voltage 
up.   Now if you go 1:1 then 0.25"/200 results in a resolution of 0.00125".  
Torque falls off to 50% with half stepping and micro-stepping results in a 
70.7% reduction in max torque.  And Micro-stepping also can require as many as 
4 steps before static torque is overcome and the motor shaft turning.  That's 
just due to the nature of the current waveform so for accuracy you must design 
for full step resolution.

John


> -Original Message-
> From: Thaddeus Waldner [mailto:thadw...@gmail.com]
> Sent: February-05-22 12:40 PM
> To: Enhanced Machine Controller (EMC)
> Subject: Re: [Emc-users] What Would You Suggest?
> 
> I believe the flat part of the curve is defined by the motor thermal limits. 
> Is this correct?
> 
> > On Feb 5, 2022, at 11:44 AM, John Dammeyer  wrote:
> >
> > ?All fine and good but doesn't help anyone choose a stepper motor.  For 
> > example:
> > https://www.geckodrive.com/support/step-motor-basics.html
> > tries to explain corner speed but fakes the curves by showing that the 
> > torque of a stepper motor is constant up to a certain speed.
> I've yet to see any curves of real motors that look like that.
> >
> > Perhaps you can find some and post those that do show flat torque up to a 
> > 'corner speed'?
> >
> > In either case that doesn't really help anyone choose a motor so that Gecko 
> > article

Re: [Emc-users] What Would You Suggest?

[Thaddeus Waldner]

>>> You described it correctly.  But I think what Robin meant by "Corner
>>>>> Frequency" might be the peak of the power vs. RPM graph.  Basically, the
>>>>> frequency where power output starts to fall with RPM.
>>>>> 
>>>>> But now it can get worse, or really better but more complex.   We have
>>>>> these so-called "closed loop stepper drivers and also a few people are
>>>>> running the steppers as if they were many-pole BLDC analog (continuous,
>>>>> non-stepping) mortors
>>>>> 
>>>>> On Fri, Feb 4, 2022 at 2:39 PM John Dammeyer 
>>>> wrote:
>>>>> 
>>>>>> I disagree.  The physics of the motor, which include inductance along
>>>> with
>>>>>> the generated back emf from the motor spinning in the magnetic field,
>>>> is
>>>>>> what cause the torque of the motor to drop off the faster it goes.
>>>>>> 
>>>>>> The problem is to spin a stepper motor you have to not just change to
>>>> a
>>>>>> new winding like a DC motor does but completely reverse the direction
>>>> of
>>>>>> the current through the winding.  In order to do that you have to
>>>> deal with
>>>>>> the collapsing magnetic field and counter the resulting generated
>>>> voltage
>>>>>> which is based on the inductance of the windings.
>>>>>> 
>>>>>> That's why the winding voltage of a stepper motor might be only 2V to
>>>> get
>>>>>> the rated 3A but you need 48V to make it turn quickly.  And because
>>>> of  the
>>>>>> inductance and collapsing field,  time is required to change the
>>>> direction
>>>>>> of the current through the winding.  If that time is longer than the
>>>> next
>>>>>> direction change then you never reach max current through the
>>>> windings and
>>>>>> you don't develop full torque.  That's why a stepper motor with a 24V
>>>> power
>>>>>> supply has the same holding torque as one with a 48V power supply.
>>>> The
>>>>>> current limiting of the drive holds the winding current at 3A.  But
>>>> run it
>>>>>> at 24V or at 48V you get a totally different torque curve.
>>>>>> 
>>>>>> If you are going to mention something called the corner frequency of a
>>>>>> stepper motor+drive please show us the graphs and specifications.  I
>>>>>> haven't been able to find that rating on any stepper motor.
>>>>>> 
>>>>>> Perhaps you can point it for this one?
>>>>>> http://www.automationtechnologiesinc.com/download/9259/
>>>>>> 
>>>>>> And explain how you determined that corner frequency?
>>>>>> John
>>>>>> 
>>>>>> 
>>>>>> 
>>>>>> 
>>>>>> 
>>>>>> 
>>>>>> 
>>>>>>> -Original Message-
>>>>>>> From: Robin Szemeti via Emc-users [mailto:
>>>>>> emc-users@lists.sourceforge.net]
>>>>>>> Sent: February-04-22 2:01 PM
>>>>>>> To: Enhanced Machine Controller (EMC)
>>>>>>> Cc: Robin Szemeti
>>>>>>> Subject: Re: [Emc-users] What Would You Suggest?
>>>>>>> 
>>>>>>> What people continually get totally wrong with steppers is failing
>>>> to
>>>>>>> understand that the maximum power is delivered at the corner
>>>> frequency,
>>>>>> and
>>>>>>> power output is constant above that.
>>>>>>> 
>>>>>>> If you have an application that needs to move at say 2m a minute
>>>> and your
>>>>>>> stepper stalls, there seems to be some crazy logic that says to
>>>> people
>>>>>> "Oh,
>>>>>>> the stepper stalled because it was going too fast, I need to change
>>>> the
>>>>>>> gearing so the motor spins more slowly" .. which is of course ass
>>>>>> backwards.
>>>>>>> 
>>>>>>> The stepper stalled because the power output of the motor was less
>>>> than
>>>>>> the
>>>

Re: [Emc-users] What Would You Suggest?

[Jérémie Tarot]

Le sam. 5 févr. 2022 à 18:44, John Dammeyer  a
écrit :

> All fine and good but doesn't help anyone choose a stepper motor.
> ..
> Perhaps explain how _you_ choose a stepper motor for a given axis?  What
> process do you go through to do this?


Earlier today reading this thread, I thought such a stepper selection how
to would be a priceless addition to our implementor documentation! Same for
other kinds of motors, btw.

Any of yall would be willing to contribute, even in part, or just with good
actionnable references, to this document(s)?

TY
Jérémie

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Re: [Emc-users] What Would You Suggest?

[John Dammeyer]

ppers as if they were many-pole BLDC analog (continuous,
> >> > non-stepping) mortors
> >> >
> >> > On Fri, Feb 4, 2022 at 2:39 PM John Dammeyer 
> >> wrote:
> >> >
> >> > > I disagree.  The physics of the motor, which include inductance along
> >> with
> >> > > the generated back emf from the motor spinning in the magnetic field,
> >> is
> >> > > what cause the torque of the motor to drop off the faster it goes.
> >> > >
> >> > > The problem is to spin a stepper motor you have to not just change to
> >> a
> >> > > new winding like a DC motor does but completely reverse the direction
> >> of
> >> > > the current through the winding.  In order to do that you have to
> >> deal with
> >> > > the collapsing magnetic field and counter the resulting generated
> >> voltage
> >> > > which is based on the inductance of the windings.
> >> > >
> >> > > That's why the winding voltage of a stepper motor might be only 2V to
> >> get
> >> > > the rated 3A but you need 48V to make it turn quickly.  And because
> >> of  the
> >> > > inductance and collapsing field,  time is required to change the
> >> direction
> >> > > of the current through the winding.  If that time is longer than the
> >> next
> >> > > direction change then you never reach max current through the
> >> windings and
> >> > > you don't develop full torque.  That's why a stepper motor with a 24V
> >> power
> >> > > supply has the same holding torque as one with a 48V power supply.
> >> The
> >> > > current limiting of the drive holds the winding current at 3A.  But
> >> run it
> >> > > at 24V or at 48V you get a totally different torque curve.
> >> > >
> >> > > If you are going to mention something called the corner frequency of a
> >> > > stepper motor+drive please show us the graphs and specifications.  I
> >> > > haven't been able to find that rating on any stepper motor.
> >> > >
> >> > > Perhaps you can point it for this one?
> >> > > http://www.automationtechnologiesinc.com/download/9259/
> >> > >
> >> > > And explain how you determined that corner frequency?
> >> > > John
> >> > >
> >> > >
> >> > >
> >> > >
> >> > >
> >> > >
> >> > >
> >> > > > -Original Message-
> >> > > > From: Robin Szemeti via Emc-users [mailto:
> >> > > emc-users@lists.sourceforge.net]
> >> > > > Sent: February-04-22 2:01 PM
> >> > > > To: Enhanced Machine Controller (EMC)
> >> > > > Cc: Robin Szemeti
> >> > > > Subject: Re: [Emc-users] What Would You Suggest?
> >> > > >
> >> > > > What people continually get totally wrong with steppers is failing
> >> to
> >> > > > understand that the maximum power is delivered at the corner
> >> frequency,
> >> > > and
> >> > > > power output is constant above that.
> >> > > >
> >> > > > If you have an application that needs to move at say 2m a minute
> >> and your
> >> > > > stepper stalls, there seems to be some crazy logic that says to
> >> people
> >> > > "Oh,
> >> > > > the stepper stalled because it was going too fast, I need to change
> >> the
> >> > > > gearing so the motor spins more slowly" .. which is of course ass
> >> > > backwards.
> >> > > >
> >> > > > The stepper stalled because the power output of the motor was less
> >> than
> >> > > the
> >> > > > power requirement of the machine ... to increase the power output
> >> of the
> >> > > > motor, you need to spin it faster, not slower.  Steppers motors are
> >> > > capable
> >> > > > of excellent performance but they do need to be used correctly ...
> >> sadly,
> >> > > > in most amateur applications they are not.
> >> > > >
> >> > > > If the corner frequency with your drive and voltage is at around
> >> 2000
> >> > > steps
> >> > > > per second and you are only ever de

Re: [Emc-users] What Would You Suggest?

[andy pugh]

On Sat, 5 Feb 2022 at 12:34, Stuart Stevenson  wrote:
>
> Guys,
> Causing me to 'think' this early hurts my head but I need to express this
> thought. It may be totally crazy but is there a way to 'double wind' a
> motor to cancel/use the back emf?

Yes, absolutely.
Unfortunately this also cancels out all the torque :-)

(In fact this is the way to identify the pole pairs and pole
directions on an 8-wire motor, by working out what combinations make
the rotor hard to turn, and which not, when the wires are shorted in
various combinations.)

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1912


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Re: [Emc-users] What Would You Suggest?

[Stuart Stevenson]

e a DC motor does but completely reverse the
> direction
> >> of
> >> > > the current through the winding.  In order to do that you have to
> >> deal with
> >> > > the collapsing magnetic field and counter the resulting generated
> >> voltage
> >> > > which is based on the inductance of the windings.
> >> > >
> >> > > That's why the winding voltage of a stepper motor might be only 2V
> to
> >> get
> >> > > the rated 3A but you need 48V to make it turn quickly.  And because
> >> of  the
> >> > > inductance and collapsing field,  time is required to change the
> >> direction
> >> > > of the current through the winding.  If that time is longer than the
> >> next
> >> > > direction change then you never reach max current through the
> >> windings and
> >> > > you don't develop full torque.  That's why a stepper motor with a
> 24V
> >> power
> >> > > supply has the same holding torque as one with a 48V power supply.
> >> The
> >> > > current limiting of the drive holds the winding current at 3A.  But
> >> run it
> >> > > at 24V or at 48V you get a totally different torque curve.
> >> > >
> >> > > If you are going to mention something called the corner frequency
> of a
> >> > > stepper motor+drive please show us the graphs and specifications.  I
> >> > > haven't been able to find that rating on any stepper motor.
> >> > >
> >> > > Perhaps you can point it for this one?
> >> > > http://www.automationtechnologiesinc.com/download/9259/
> >> > >
> >> > > And explain how you determined that corner frequency?
> >> > > John
> >> > >
> >> > >
> >> > >
> >> > >
> >> > >
> >> > >
> >> > >
> >> > > > -Original Message-
> >> > > > From: Robin Szemeti via Emc-users [mailto:
> >> > > emc-users@lists.sourceforge.net]
> >> > > > Sent: February-04-22 2:01 PM
> >> > > > To: Enhanced Machine Controller (EMC)
> >> > > > Cc: Robin Szemeti
> >> > > > Subject: Re: [Emc-users] What Would You Suggest?
> >> > > >
> >> > > > What people continually get totally wrong with steppers is failing
> >> to
> >> > > > understand that the maximum power is delivered at the corner
> >> frequency,
> >> > > and
> >> > > > power output is constant above that.
> >> > > >
> >> > > > If you have an application that needs to move at say 2m a minute
> >> and your
> >> > > > stepper stalls, there seems to be some crazy logic that says to
> >> people
> >> > > "Oh,
> >> > > > the stepper stalled because it was going too fast, I need to
> change
> >> the
> >> > > > gearing so the motor spins more slowly" .. which is of course ass
> >> > > backwards.
> >> > > >
> >> > > > The stepper stalled because the power output of the motor was less
> >> than
> >> > > the
> >> > > > power requirement of the machine ... to increase the power output
> >> of the
> >> > > > motor, you need to spin it faster, not slower.  Steppers motors
> are
> >> > > capable
> >> > > > of excellent performance but they do need to be used correctly ...
> >> sadly,
> >> > > > in most amateur applications they are not.
> >> > > >
> >> > > > If the corner frequency with your drive and voltage is at around
> >> 2000
> >> > > steps
> >> > > > per second and you are only ever delivering 1000 steps per second,
> >> you
> >> > > can
> >> > > > never got more than half the mechanical power out that the motor
> is
> >> > > capable
> >> > > > of.
> >> > > >
> >> > > > On Fri, 4 Feb 2022 at 17:13, John Dammeyer <
> jo...@autoartisans.com>
> >> > > wrote:
> >> > > >
> >> > > > >
> >> > > > >
> >> > > > > > From: Kenneth Lerman [mailto:ler...@se-ltd.com]
> >> > > > > > The longitudin

Re: [Emc-users] What Would You Suggest?

[Robin Szemeti via Emc-users]

en you never reach max current through the
>> windings and
>> > > you don't develop full torque.  That's why a stepper motor with a 24V
>> power
>> > > supply has the same holding torque as one with a 48V power supply.
>> The
>> > > current limiting of the drive holds the winding current at 3A.  But
>> run it
>> > > at 24V or at 48V you get a totally different torque curve.
>> > >
>> > > If you are going to mention something called the corner frequency of a
>> > > stepper motor+drive please show us the graphs and specifications.  I
>> > > haven't been able to find that rating on any stepper motor.
>> > >
>> > > Perhaps you can point it for this one?
>> > > http://www.automationtechnologiesinc.com/download/9259/
>> > >
>> > > And explain how you determined that corner frequency?
>> > > John
>> > >
>> > >
>> > >
>> > >
>> > >
>> > >
>> > >
>> > > > -Original Message-
>> > > > From: Robin Szemeti via Emc-users [mailto:
>> > > emc-users@lists.sourceforge.net]
>> > > > Sent: February-04-22 2:01 PM
>> > > > To: Enhanced Machine Controller (EMC)
>> > > > Cc: Robin Szemeti
>> > > > Subject: Re: [Emc-users] What Would You Suggest?
>> > > >
>> > > > What people continually get totally wrong with steppers is failing
>> to
>> > > > understand that the maximum power is delivered at the corner
>> frequency,
>> > > and
>> > > > power output is constant above that.
>> > > >
>> > > > If you have an application that needs to move at say 2m a minute
>> and your
>> > > > stepper stalls, there seems to be some crazy logic that says to
>> people
>> > > "Oh,
>> > > > the stepper stalled because it was going too fast, I need to change
>> the
>> > > > gearing so the motor spins more slowly" .. which is of course ass
>> > > backwards.
>> > > >
>> > > > The stepper stalled because the power output of the motor was less
>> than
>> > > the
>> > > > power requirement of the machine ... to increase the power output
>> of the
>> > > > motor, you need to spin it faster, not slower.  Steppers motors are
>> > > capable
>> > > > of excellent performance but they do need to be used correctly ...
>> sadly,
>> > > > in most amateur applications they are not.
>> > > >
>> > > > If the corner frequency with your drive and voltage is at around
>> 2000
>> > > steps
>> > > > per second and you are only ever delivering 1000 steps per second,
>> you
>> > > can
>> > > > never got more than half the mechanical power out that the motor is
>> > > capable
>> > > > of.
>> > > >
>> > > > On Fri, 4 Feb 2022 at 17:13, John Dammeyer 
>> > > wrote:
>> > > >
>> > > > >
>> > > > >
>> > > > > > From: Kenneth Lerman [mailto:ler...@se-ltd.com]
>> > > > > > The longitudinal travel is just over a foot, and it takes about
>> 3-1/2
>> > > > > turns
>> > > > > > of the crank to go that distance. I'm thinking around  a second
>> per
>> > > turn
>> > > > > > would be about the maximum. So, that's 60 RPM. I'm thinking of
>> a 1:6
>> > > > > ratio
>> > > > > > on the timing belt pulleys, so that's 360 RPM at the stepper
>> which is
>> > > > > > pretty slow. A full stepping rate would be 200 * 360/60 => 200
>> * 6
>> > > which
>> > > > > is
>> > > > > > only 1200 steps per second.
>> > > > >
>> > > > > You won't want to run full step.  A minimum should be 8
>> > > micro-steps/step
>> > > > > to avoid resonance and loss of position or lockup.   I'd measure
>> the
>> > > torque
>> > > > > required to move the table by attaching a lever to the hand wheel
>> that
>> > > is
>> > > > > say 1' long.  Set it horizontal and start hanging weight onto the
>> end
>> > > to
>> > > > > get ft-lbs or ft-in until it turns. That's the torque requ

Re: [Emc-users] What Would You Suggest?

[Robin Szemeti via Emc-users]

John,

You are fundamentally incorrect when you state " the torque of the motor to
drop off the faster it goes" .. although the back EMF is correct, with a
modern current limited drive, the torque is flat until the corner
frequency, then drops off  ... up to the corner frequency the torque is
constant with a good current-limited drive, above the corner frequency the
torque drops off, power is constant.  You are perhaps confusing the raw
torque/speed curve of a motor fed from a constant voltage source, which is
useful but is not how they are typically used in practice.

https://res.cloudinary.com/engineering-com/image/upload/w_640,h_640,c_limit,q_auto,f_auto/image002_bezhrr.jpg

On Sat, 5 Feb 2022 at 09:00, John Dammeyer  wrote:

> Hi Chris,
> My issue is that a comment about corner frequency with stepper motors
> _might_ well be valid as long as the maximum current for each step is
> reached before or at the end of the step.  But the motor is turning pretty
> slowly there compared to how they are used in real life.
>
> However the comment about corner frequency with respect to steppers
> perhaps is only backed by alternative facts?
>
> I must admit I've not investigated in detail the closed loop steppers.
> The price of an industrial version I worked with was more than the price of
> an AC servo and at higher speeds I could stop the pulley with my fingers.
> Yes. It faulted.  But that isn't really the point.  The DC and AC servos at
> higher speeds just work better.
>
> Stepper motors work great at low speeds usually directly coupled.
> Contrary to popular belief the micro-stepping doesn't improve resolution
> but gets rid of resonance and gives the appearance of better resolution.
> But it doesn't change the fact that the current still has to reverse every
> full step.  I believe that in fact Gecko drives improve high speed torque
> by switching back to full step mode above the resonance velocity.
>
> Now instead of 0.707 x max current in both windings (at the most) we're
> back to 100% in both with an increase in torque.  Absolutely nothing to do
> with corner frequencies whatever they might be or how they are determined.
>
> John
>
>
>
>
>
> > From: Chris Albertson [mailto:albertson.ch...@gmail.com]
> >
> > John,
> >
> > You described it correctly.  But I think what Robin meant by "Corner
> > Frequency" might be the peak of the power vs. RPM graph.  Basically, the
> > frequency where power output starts to fall with RPM.
> >
> > But now it can get worse, or really better but more complex.   We have
> > these so-called "closed loop stepper drivers and also a few people are
> > running the steppers as if they were many-pole BLDC analog (continuous,
> > non-stepping) mortors
> >
> > On Fri, Feb 4, 2022 at 2:39 PM John Dammeyer 
> wrote:
> >
> > > I disagree.  The physics of the motor, which include inductance along
> with
> > > the generated back emf from the motor spinning in the magnetic field,
> is
> > > what cause the torque of the motor to drop off the faster it goes.
> > >
> > > The problem is to spin a stepper motor you have to not just change to a
> > > new winding like a DC motor does but completely reverse the direction
> of
> > > the current through the winding.  In order to do that you have to deal
> with
> > > the collapsing magnetic field and counter the resulting generated
> voltage
> > > which is based on the inductance of the windings.
> > >
> > > That's why the winding voltage of a stepper motor might be only 2V to
> get
> > > the rated 3A but you need 48V to make it turn quickly.  And because
> of  the
> > > inductance and collapsing field,  time is required to change the
> direction
> > > of the current through the winding.  If that time is longer than the
> next
> > > direction change then you never reach max current through the windings
> and
> > > you don't develop full torque.  That's why a stepper motor with a 24V
> power
> > > supply has the same holding torque as one with a 48V power supply.  The
> > > current limiting of the drive holds the winding current at 3A.  But
> run it
> > > at 24V or at 48V you get a totally different torque curve.
> > >
> > > If you are going to mention something called the corner frequency of a
> > > stepper motor+drive please show us the graphs and specifications.  I
> > > haven't been able to find that rating on any stepper motor.
> > >
> > > Perhaps you can point it for this one?
> > > http://www.automationtechnologiesinc.com/download/9259/
> > >
> > > 

Re: [Emc-users] What Would You Suggest?

[John Dammeyer]

Hi Chris,
My issue is that a comment about corner frequency with stepper motors _might_ 
well be valid as long as the maximum current for each step is reached before or 
at the end of the step.  But the motor is turning pretty slowly there compared 
to how they are used in real life.

However the comment about corner frequency with respect to steppers perhaps is 
only backed by alternative facts?

I must admit I've not investigated in detail the closed loop steppers.  The 
price of an industrial version I worked with was more than the price of an AC 
servo and at higher speeds I could stop the pulley with my fingers.  Yes. It 
faulted.  But that isn't really the point.  The DC and AC servos at higher 
speeds just work better.

Stepper motors work great at low speeds usually directly coupled.  Contrary to 
popular belief the micro-stepping doesn't improve resolution but gets rid of 
resonance and gives the appearance of better resolution.  But it doesn't change 
the fact that the current still has to reverse every full step.  I believe that 
in fact Gecko drives improve high speed torque by switching back to full step 
mode above the resonance velocity.  

Now instead of 0.707 x max current in both windings (at the most) we're back to 
100% in both with an increase in torque.  Absolutely nothing to do with corner 
frequencies whatever they might be or how they are determined.

John





> From: Chris Albertson [mailto:albertson.ch...@gmail.com]
> 
> John,
> 
> You described it correctly.  But I think what Robin meant by "Corner
> Frequency" might be the peak of the power vs. RPM graph.  Basically, the
> frequency where power output starts to fall with RPM.
> 
> But now it can get worse, or really better but more complex.   We have
> these so-called "closed loop stepper drivers and also a few people are
> running the steppers as if they were many-pole BLDC analog (continuous,
> non-stepping) mortors
> 
> On Fri, Feb 4, 2022 at 2:39 PM John Dammeyer  wrote:
> 
> > I disagree.  The physics of the motor, which include inductance along with
> > the generated back emf from the motor spinning in the magnetic field, is
> > what cause the torque of the motor to drop off the faster it goes.
> >
> > The problem is to spin a stepper motor you have to not just change to a
> > new winding like a DC motor does but completely reverse the direction of
> > the current through the winding.  In order to do that you have to deal with
> > the collapsing magnetic field and counter the resulting generated voltage
> > which is based on the inductance of the windings.
> >
> > That's why the winding voltage of a stepper motor might be only 2V to get
> > the rated 3A but you need 48V to make it turn quickly.  And because of  the
> > inductance and collapsing field,  time is required to change the direction
> > of the current through the winding.  If that time is longer than the next
> > direction change then you never reach max current through the windings and
> > you don't develop full torque.  That's why a stepper motor with a 24V power
> > supply has the same holding torque as one with a 48V power supply.  The
> > current limiting of the drive holds the winding current at 3A.  But run it
> > at 24V or at 48V you get a totally different torque curve.
> >
> > If you are going to mention something called the corner frequency of a
> > stepper motor+drive please show us the graphs and specifications.  I
> > haven't been able to find that rating on any stepper motor.
> >
> > Perhaps you can point it for this one?
> > http://www.automationtechnologiesinc.com/download/9259/
> >
> > And explain how you determined that corner frequency?
> > John
> >
> >
> >
> >
> >
> >
> >
> > > -Original Message-
> > > From: Robin Szemeti via Emc-users [mailto:
> > emc-users@lists.sourceforge.net]
> > > Sent: February-04-22 2:01 PM
> > > To: Enhanced Machine Controller (EMC)
> > > Cc: Robin Szemeti
> > > Subject: Re: [Emc-users] What Would You Suggest?
> > >
> > > What people continually get totally wrong with steppers is failing to
> > > understand that the maximum power is delivered at the corner frequency,
> > and
> > > power output is constant above that.
> > >
> > > If you have an application that needs to move at say 2m a minute and your
> > > stepper stalls, there seems to be some crazy logic that says to people
> > "Oh,
> > > the stepper stalled because it was going too fast, I need to change the
> > > gearing so the motor spins more slowly" .. which is of course ass
> > backwards.
> > >
> &g

Re: [Emc-users] What Would You Suggest?

[Gregg Eshelman via Emc-users]

What motor driven surface grinder with power feed *doesn't have* automatic 
reversing in X and adjustable auto feed step in Y? Even ones 100 or so years 
old had features like adjustable X travel stops. I'd bet there were grinders 
with Y travel stops so an operator could set it and forget it, then come back 
later to crank the table back on the Y axis, turn the spindle down a bit then 
set it off on making the next pass.


   On Friday, February 4, 2022, 02:07:48 PM MST, John Figie 
 wrote:  
 
 On Fri, Feb 4, 2022, 2:55 PM dave engvall  wrote:

> Hi,
> I seem to remember a crank as in crankshaft lashup to drive the table.
> Personally I think the hydraulic setup is better but harder to achieve.
> The free lunch is hard to find.
> Dave
>
>
> Hmm

I have a Covel hydraulic automatic surface grinder. I would rather have
motors - maybe a retrofit someday. The issues with hydraulic are power
consumption but the pump and leaking oil because it's old.  
___
Emc-users mailing list
Emc-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-users

Re: [Emc-users] What Would You Suggest?

[Chris Albertson]

John,

You described it correctly.  But I think what Robin meant by "Corner
Frequency" might be the peak of the power vs. RPM graph.  Basically, the
frequency where power output starts to fall with RPM.

But now it can get worse, or really better but more complex.   We have
these so-called "closed loop stepper drivers and also a few people are
running the steppers as if they were many-pole BLDC analog (continuous,
non-stepping) mortors

On Fri, Feb 4, 2022 at 2:39 PM John Dammeyer  wrote:

> I disagree.  The physics of the motor, which include inductance along with
> the generated back emf from the motor spinning in the magnetic field, is
> what cause the torque of the motor to drop off the faster it goes.
>
> The problem is to spin a stepper motor you have to not just change to a
> new winding like a DC motor does but completely reverse the direction of
> the current through the winding.  In order to do that you have to deal with
> the collapsing magnetic field and counter the resulting generated voltage
> which is based on the inductance of the windings.
>
> That's why the winding voltage of a stepper motor might be only 2V to get
> the rated 3A but you need 48V to make it turn quickly.  And because of  the
> inductance and collapsing field,  time is required to change the direction
> of the current through the winding.  If that time is longer than the next
> direction change then you never reach max current through the windings and
> you don't develop full torque.  That's why a stepper motor with a 24V power
> supply has the same holding torque as one with a 48V power supply.  The
> current limiting of the drive holds the winding current at 3A.  But run it
> at 24V or at 48V you get a totally different torque curve.
>
> If you are going to mention something called the corner frequency of a
> stepper motor+drive please show us the graphs and specifications.  I
> haven't been able to find that rating on any stepper motor.
>
> Perhaps you can point it for this one?
> http://www.automationtechnologiesinc.com/download/9259/
>
> And explain how you determined that corner frequency?
> John
>
>
>
>
>
>
>
> > -Original Message-
> > From: Robin Szemeti via Emc-users [mailto:
> emc-users@lists.sourceforge.net]
> > Sent: February-04-22 2:01 PM
> > To: Enhanced Machine Controller (EMC)
> > Cc: Robin Szemeti
> > Subject: Re: [Emc-users] What Would You Suggest?
> >
> > What people continually get totally wrong with steppers is failing to
> > understand that the maximum power is delivered at the corner frequency,
> and
> > power output is constant above that.
> >
> > If you have an application that needs to move at say 2m a minute and your
> > stepper stalls, there seems to be some crazy logic that says to people
> "Oh,
> > the stepper stalled because it was going too fast, I need to change the
> > gearing so the motor spins more slowly" .. which is of course ass
> backwards.
> >
> > The stepper stalled because the power output of the motor was less than
> the
> > power requirement of the machine ... to increase the power output of the
> > motor, you need to spin it faster, not slower.  Steppers motors are
> capable
> > of excellent performance but they do need to be used correctly ... sadly,
> > in most amateur applications they are not.
> >
> > If the corner frequency with your drive and voltage is at around 2000
> steps
> > per second and you are only ever delivering 1000 steps per second, you
> can
> > never got more than half the mechanical power out that the motor is
> capable
> > of.
> >
> > On Fri, 4 Feb 2022 at 17:13, John Dammeyer 
> wrote:
> >
> > >
> > >
> > > > From: Kenneth Lerman [mailto:ler...@se-ltd.com]
> > > > The longitudinal travel is just over a foot, and it takes about 3-1/2
> > > turns
> > > > of the crank to go that distance. I'm thinking around  a second per
> turn
> > > > would be about the maximum. So, that's 60 RPM. I'm thinking of a 1:6
> > > ratio
> > > > on the timing belt pulleys, so that's 360 RPM at the stepper which is
> > > > pretty slow. A full stepping rate would be 200 * 360/60 => 200 * 6
> which
> > > is
> > > > only 1200 steps per second.
> > >
> > > You won't want to run full step.  A minimum should be 8
> micro-steps/step
> > > to avoid resonance and loss of position or lockup.   I'd measure the
> torque
> > > required to move the table by attaching a lever to the hand wheel that
> is
> > > say 1' long.  Set it horizontal and start hanging weight o

Re: [Emc-users] What Would You Suggest?

[John Dammeyer]

I disagree.  The physics of the motor, which include inductance along with the 
generated back emf from the motor spinning in the magnetic field, is what cause 
the torque of the motor to drop off the faster it goes.

The problem is to spin a stepper motor you have to not just change to a new 
winding like a DC motor does but completely reverse the direction of the 
current through the winding.  In order to do that you have to deal with the 
collapsing magnetic field and counter the resulting generated voltage which is 
based on the inductance of the windings.

That's why the winding voltage of a stepper motor might be only 2V to get the 
rated 3A but you need 48V to make it turn quickly.  And because of  the 
inductance and collapsing field,  time is required to change the direction of 
the current through the winding.  If that time is longer than the next 
direction change then you never reach max current through the windings and you 
don't develop full torque.  That's why a stepper motor with a 24V power supply 
has the same holding torque as one with a 48V power supply.  The current 
limiting of the drive holds the winding current at 3A.  But run it at 24V or at 
48V you get a totally different torque curve.

If you are going to mention something called the corner frequency of a stepper 
motor+drive please show us the graphs and specifications.  I haven't been able 
to find that rating on any stepper motor.  

Perhaps you can point it for this one?
http://www.automationtechnologiesinc.com/download/9259/

And explain how you determined that corner frequency?
John







> -Original Message-
> From: Robin Szemeti via Emc-users [mailto:emc-users@lists.sourceforge.net]
> Sent: February-04-22 2:01 PM
> To: Enhanced Machine Controller (EMC)
> Cc: Robin Szemeti
> Subject: Re: [Emc-users] What Would You Suggest?
> 
> What people continually get totally wrong with steppers is failing to
> understand that the maximum power is delivered at the corner frequency, and
> power output is constant above that.
> 
> If you have an application that needs to move at say 2m a minute and your
> stepper stalls, there seems to be some crazy logic that says to people "Oh,
> the stepper stalled because it was going too fast, I need to change the
> gearing so the motor spins more slowly" .. which is of course ass backwards.
> 
> The stepper stalled because the power output of the motor was less than the
> power requirement of the machine ... to increase the power output of the
> motor, you need to spin it faster, not slower.  Steppers motors are capable
> of excellent performance but they do need to be used correctly ... sadly,
> in most amateur applications they are not.
> 
> If the corner frequency with your drive and voltage is at around 2000 steps
> per second and you are only ever delivering 1000 steps per second, you can
> never got more than half the mechanical power out that the motor is capable
> of.
> 
> On Fri, 4 Feb 2022 at 17:13, John Dammeyer  wrote:
> 
> >
> >
> > > From: Kenneth Lerman [mailto:ler...@se-ltd.com]
> > > The longitudinal travel is just over a foot, and it takes about 3-1/2
> > turns
> > > of the crank to go that distance. I'm thinking around  a second per turn
> > > would be about the maximum. So, that's 60 RPM. I'm thinking of a 1:6
> > ratio
> > > on the timing belt pulleys, so that's 360 RPM at the stepper which is
> > > pretty slow. A full stepping rate would be 200 * 360/60 => 200 * 6 which
> > is
> > > only 1200 steps per second.
> >
> > You won't want to run full step.  A minimum should be 8 micro-steps/step
> > to avoid resonance and loss of position or lockup.   I'd measure the torque
> > required to move the table by attaching a lever to the hand wheel that is
> > say 1' long.  Set it horizontal and start hanging weight onto the end to
> > get ft-lbs or ft-in until it turns. That's the torque required to overcome
> > static friction.  Double that to choose your motor.
> >
> > Say that is 1 ft-lb or 192 oz-in.If you choose 3:1 for your reduction
> > ratio you get 600 oz-in.  Look at the motor torque curve (they are all
> > different and if the supplier can't give you that buy one somewhere else)
> > and see where the torque drops below 400 oz-in.  Say that's 180 RPM.
> > That's 3 RPS which multiplied by 2000 steps per rev for micro-stepping is
> > 6000 steps/second which achieves your 1 RPS on the handle.
> >
> > Or if you find it's 2 ft-lb or 400 oz-in choose a much larger motor like
> > 1200 oz-in
> > http://www.automationtechnologiesinc.com/download/9259/
> > Notice the curve at 3000 half steps per second is about 3.2NM.  That's
> > 12,000 steps per second (7.5RPS) 

Re: [Emc-users] What Would You Suggest?

[Robin Szemeti via Emc-users]

What people continually get totally wrong with steppers is failing to
understand that the maximum power is delivered at the corner frequency, and
power output is constant above that.

If you have an application that needs to move at say 2m a minute and your
stepper stalls, there seems to be some crazy logic that says to people "Oh,
the stepper stalled because it was going too fast, I need to change the
gearing so the motor spins more slowly" .. which is of course ass backwards.

The stepper stalled because the power output of the motor was less than the
power requirement of the machine ... to increase the power output of the
motor, you need to spin it faster, not slower.  Steppers motors are capable
of excellent performance but they do need to be used correctly ... sadly,
in most amateur applications they are not.

If the corner frequency with your drive and voltage is at around 2000 steps
per second and you are only ever delivering 1000 steps per second, you can
never got more than half the mechanical power out that the motor is capable
of.

On Fri, 4 Feb 2022 at 17:13, John Dammeyer  wrote:

>
>
> > From: Kenneth Lerman [mailto:ler...@se-ltd.com]
> > The longitudinal travel is just over a foot, and it takes about 3-1/2
> turns
> > of the crank to go that distance. I'm thinking around  a second per turn
> > would be about the maximum. So, that's 60 RPM. I'm thinking of a 1:6
> ratio
> > on the timing belt pulleys, so that's 360 RPM at the stepper which is
> > pretty slow. A full stepping rate would be 200 * 360/60 => 200 * 6 which
> is
> > only 1200 steps per second.
>
> You won't want to run full step.  A minimum should be 8 micro-steps/step
> to avoid resonance and loss of position or lockup.   I'd measure the torque
> required to move the table by attaching a lever to the hand wheel that is
> say 1' long.  Set it horizontal and start hanging weight onto the end to
> get ft-lbs or ft-in until it turns. That's the torque required to overcome
> static friction.  Double that to choose your motor.
>
> Say that is 1 ft-lb or 192 oz-in.If you choose 3:1 for your reduction
> ratio you get 600 oz-in.  Look at the motor torque curve (they are all
> different and if the supplier can't give you that buy one somewhere else)
> and see where the torque drops below 400 oz-in.  Say that's 180 RPM.
> That's 3 RPS which multiplied by 2000 steps per rev for micro-stepping is
> 6000 steps/second which achieves your 1 RPS on the handle.
>
> Or if you find it's 2 ft-lb or 400 oz-in choose a much larger motor like
> 1200 oz-in
> http://www.automationtechnologiesinc.com/download/9259/
> Notice the curve at 3000 half steps per second is about 3.2NM.  That's
> 12,000 steps per second (7.5RPS)  with 8 micro-steps per step well within
> the reach of even a parallel port controller and 450 oz-in.  That's well
> above the 1 RPS you need and even just 3:1 still gives you 1600 oz-in.
>
> My two cents...
> John Dammeyer
> >
> > An alternative would be to provide more gearing, but I don't think it's
> > practical to get more than about a six to one ratio in a single belt
> > reduction and I'd like to avoid mechanical complexity if I can.
> >
> > Thoughts?
> >
> > Ken
> >
> > Kenneth Lerman
> > 55 Main Street
> > Newtown, CT 06470
> >
> >
> >
> > On Fri, Feb 4, 2022 at 7:13 AM Chris Albertson <
> albertson.ch...@gmail.com>
> > wrote:
> >
> > > If looking for lowest cost solution you can us the old "Atom" computer
> to
> > > control the grinder as long as you do not  need to run the mill and
> > > grider at the same time.  Get an Eiternet interface Mesa card for the
> new
> > > machine,  You need two config files, just load the one for the mill or
> the
> > > one for the grinder.
> > >
> > > Then someday you buy a second computer you only have to move the
> Ethernet
> > > cable over.   The best option is a newer version of the Atom.  They
> seem to
> > > sell for just under $200.   Finally Newegg.com always has many used oe
> > > refurb PCs   Used PCs sourced locally can be a cheap as "free"
> > >
> > > But 9ld PCs tend to burn up a lot of power.  I am trying to get mone
> to do
> > > "wake on LAN" so it can not use power until I need to log onto it
> > >
> > > On Thu, Feb 3, 2022 at 6:52 PM Kenneth Lerman 
> wrote:
> > >
> > > > I'm considering converting a surface grinder to CNC. To start, I'll
> > > > probably just convert the longitudinal and transverse axes.
> > > >
> > > > I'll go with steppers for this -- I'm thinking NEMA-42 motors.
> > > >
> > > > My current Bridgeport clone uses servos and Jon Elson's hardware on a
> > > > little Intel Atom Box. I'm thinking of using a Rpi for this. It will
> > > need a
> > > > minimal display/control panel when completed, but initially will
> need a
> > > > display with touchscreen or mouse and possibly a keyboard. In the
> long
> > > run,
> > > > some buttons. and perhaps an mpg might be useful.
> > > >
> > > > I'd like to use a raw Rpi without adding special hardware directly.
> That
> > 

Re: [Emc-users] What Would You Suggest?

[John Dammeyer]

Hi Ken,
I just went down to the shop and set up my ELS on the Gingery Lathe to simulate 
this.  Since you don't have control over the height it does a move out of the 
way of the work to return at high speed to the BEGIN position.  It's configured 
I BROACH mode so doesn't need to have the spindle turning.

On each pass it moves out (towards me in this example) by 0.25" with the 
assumption the stone is slightly wider for a bit of overlap.   I set total 
depth of 'thread' to 2" but I'd run out of room on the cross slide before that. 
 

I can make a quick video of that if you want to see it.
John


> -Original Message-
> From: Kenneth Lerman [mailto:ler...@se-ltd.com]
> Sent: February-04-22 1:08 PM
> To: Enhanced Machine Controller (EMC)
> Subject: Re: [Emc-users] What Would You Suggest?
> 
> Hi John,
> 
> I'm planning on controlling two axes. The third axis (vertical) would
> require a lot more gearing and my general experience is machine a surface,
> measure, drop down, machine some more, repeat.
> 
> The ELS type of thing is about what I have in mind. Jog to set the xmin,
> xmax, ymin, ymax. Set a mode. Select a stepover. Hit go.
> 
> Martin pointed me at the teensy computers. They have a 3.2 inch touch
> screen that might be just the thing to control this. The stepper library
> should do the job very nicely.
> 
> Ken
> 
> Kenneth Lerman
> 55 Main Street
> Newtown, CT 06470
> 
> 
> 
> On Fri, Feb 4, 2022 at 3:22 PM John Dammeyer  wrote:
> 
> > In wanting to automate this grinder exactly how many axis do you want to
> > control.
> > I can see the movement of the table back and forth at that 1 RPM.  I can
> > see the cross slide at the end of each pass or pass and return?
> > Finally I guess depth might also be desired to a total depth?
> >
> > If depth was adjusted manually then my ELS can be configured to do
> > something like this:
> > http://www.autoartisans.com/ELS/
> > I'd set it up to turn the Z axis for BEGIN, END positions to move the
> > table in the X axis directions.
> > I'd set the X axis for the 'depth' of each pass so it would move the table
> > across using some of the parameters to fool it into not retracting but
> > either moving further in for the pass in the other direction or moving the
> > stone out of the way for the return.
> >
> > But then that's just as easy with some simple G-Code and one of those far
> > east CNC control boxes like this:
> > https://www.aliexpress.com/item/1005003646128482.html
> > For $140 Cdn with free shipping it's almost worth the risk to buy it and
> > try it.  You need stepper motor drivers, power supply, motors and pulleys
> > anyway.
> >
> > > -Original Message-
> > > From: Martin Dobbins [mailto:tu...@hotmail.com]
> > > Sent: February-04-22 10:47 AM
> > > To: Enhanced Machine Controller (EMC)
> > > Subject: Re: [Emc-users] What Would You Suggest?
> > >
> > > Hi Kenneth,
> > >
> > > I don't know if this will be any use to you at all, and it's not
> > Linuxcnc at least not yet.
> > >
> > > I an effort to emulate this:
> > >
> > > https://www.youtube.com/watch?v=z4t8pmsnYow
> > >
> > > Which is all powered by a PIC
> > >
> > > I liked this but didn't want to use a PIC.  Tried first with an Arduino
> > because I had one on hand, but that just wasn't going to work.
> > > So, I moved to one of these and got the 3.2 version:
> > >
> > > https://www.pjrc.com/teensy/
> > >
> > > Partly because it has an excellent library for controlling steppers:
> > >
> > > https://luni64.github.io/TeensyStep/
> > >
> > > It's driving a NEMA 34 1805 oz/in through one of these
> > >
> > > http://www.leadshine.com/uploadfile/down/ma860hm.pdf
> > >
> > > which will work with AC or DC
> > >
> > > So, one of these:
> > >
> > > https://www.ebay.com/itm/194282558090
> > >
> > > On the back of which is a jumper to set input voltage 240, 220, 200,
> > 110.  With outputs on the back for 110v and 220v.  It's intended
> > > to be a travel item so your 110 volt stuff will work on 220v and vice
> > versa. A step up step down transformer.  If you lie to it you can
> > > feed it 118v to 120v (what comes out of my wall sockets) and get it to
> > supply lesser AC volts to the stepper driver.
> > >
> > > If you're still awake?
> > >
> > > I can get 2000 rpm plus out of that big stepper, but I don't need speed
> > like that, I need torque, so

Re: [Emc-users] What Would You Suggest?

[Kenneth Lerman]

Hi John,

I'm planning on controlling two axes. The third axis (vertical) would
require a lot more gearing and my general experience is machine a surface,
measure, drop down, machine some more, repeat.

The ELS type of thing is about what I have in mind. Jog to set the xmin,
xmax, ymin, ymax. Set a mode. Select a stepover. Hit go.

Martin pointed me at the teensy computers. They have a 3.2 inch touch
screen that might be just the thing to control this. The stepper library
should do the job very nicely.

Ken

Kenneth Lerman
55 Main Street
Newtown, CT 06470



On Fri, Feb 4, 2022 at 3:22 PM John Dammeyer  wrote:

> In wanting to automate this grinder exactly how many axis do you want to
> control.
> I can see the movement of the table back and forth at that 1 RPM.  I can
> see the cross slide at the end of each pass or pass and return?
> Finally I guess depth might also be desired to a total depth?
>
> If depth was adjusted manually then my ELS can be configured to do
> something like this:
> http://www.autoartisans.com/ELS/
> I'd set it up to turn the Z axis for BEGIN, END positions to move the
> table in the X axis directions.
> I'd set the X axis for the 'depth' of each pass so it would move the table
> across using some of the parameters to fool it into not retracting but
> either moving further in for the pass in the other direction or moving the
> stone out of the way for the return.
>
> But then that's just as easy with some simple G-Code and one of those far
> east CNC control boxes like this:
> https://www.aliexpress.com/item/1005003646128482.html
> For $140 Cdn with free shipping it's almost worth the risk to buy it and
> try it.  You need stepper motor drivers, power supply, motors and pulleys
> anyway.
>
> > -Original Message-
> > From: Martin Dobbins [mailto:tu...@hotmail.com]
> > Sent: February-04-22 10:47 AM
> > To: Enhanced Machine Controller (EMC)
> > Subject: Re: [Emc-users] What Would You Suggest?
> >
> > Hi Kenneth,
> >
> > I don't know if this will be any use to you at all, and it's not
> Linuxcnc at least not yet.
> >
> > I an effort to emulate this:
> >
> > https://www.youtube.com/watch?v=z4t8pmsnYow
> >
> > Which is all powered by a PIC
> >
> > I liked this but didn't want to use a PIC.  Tried first with an Arduino
> because I had one on hand, but that just wasn't going to work.
> > So, I moved to one of these and got the 3.2 version:
> >
> > https://www.pjrc.com/teensy/
> >
> > Partly because it has an excellent library for controlling steppers:
> >
> > https://luni64.github.io/TeensyStep/
> >
> > It's driving a NEMA 34 1805 oz/in through one of these
> >
> > http://www.leadshine.com/uploadfile/down/ma860hm.pdf
> >
> > which will work with AC or DC
> >
> > So, one of these:
> >
> > https://www.ebay.com/itm/194282558090
> >
> > On the back of which is a jumper to set input voltage 240, 220, 200,
> 110.  With outputs on the back for 110v and 220v.  It's intended
> > to be a travel item so your 110 volt stuff will work on 220v and vice
> versa. A step up step down transformer.  If you lie to it you can
> > feed it 118v to 120v (what comes out of my wall sockets) and get it to
> supply lesser AC volts to the stepper driver.
> >
> > If you're still awake?
> >
> > I can get 2000 rpm plus out of that big stepper, but I don't need speed
> like that, I need torque, so it's geared down 4:1 with the
> > spindle it's driving (when the stepper's rotating at a leisurely 25 rpm
> the spindle is turning at 100 rpm).  It's still an unfinished project.
> >
> > I'm envious of that grinder.
> >
> > Martin
> >
> > 
> > Kenneth Lerman wrote:
> >
> >
> > Chris -- At my house, computers are all over the place. I think I have a
> > spare atom floating around. Also a couple of other machines.
> > Gene -- The grinder is here.
> > <
> https://drive.google.com/file/d/1L8JiX0rtDZO99rVnQKNjUH7m-ZgFz2Un/view?usp=sharing
> >
> > The
> > ways look pretty clean. The only accessory I have is a magnetic chuck.
> >
> > I don't really need a surface grinder, but no shop is complete without
> one.
> > Once I started to use it, I realized that my right arm and shoulder
> really
> > aren't suited to this type of manual work.
> >
> > The longitudinal travel is just over a foot, and it takes about 3-1/2
> turns
> > of the crank to go that distance. I'm thinking around  a second per turn
> > would be about the maximum. So, that's 60 RPM. I'm thinking of a 1:6
> ratio
> > on the tim

Re: [Emc-users] What Would You Suggest?

[John Figie]

On Fri, Feb 4, 2022, 2:55 PM dave engvall  wrote:

> Hi,
> I seem to remember a crank as in crankshaft lashup to drive the table.
> Personally I think the hydraulic setup is better but harder to achieve.
> The free lunch is hard to find.
> Dave
>
>
> Hmm

I have a Covel hydraulic automatic surface grinder. I would rather have
motors - maybe a retrofit someday. The issues with hydraulic are power
consumption but the pump and leaking oil because it's old.

>

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Re: [Emc-users] What Would You Suggest?

[dave engvall]

Hi,
I seem to remember a crank as in crankshaft lashup to drive the table. 
Personally I think the hydraulic setup is better but harder to achieve. 
The free lunch is hard to find.

Dave

On 2/4/22 9:11 AM, John Dammeyer wrote:



From: Kenneth Lerman [mailto:ler...@se-ltd.com]
The longitudinal travel is just over a foot, and it takes about 3-1/2 turns
of the crank to go that distance. I'm thinking around  a second per turn
would be about the maximum. So, that's 60 RPM. I'm thinking of a 1:6 ratio
on the timing belt pulleys, so that's 360 RPM at the stepper which is
pretty slow. A full stepping rate would be 200 * 360/60 => 200 * 6 which is
only 1200 steps per second.

You won't want to run full step.  A minimum should be 8 micro-steps/step to 
avoid resonance and loss of position or lockup.   I'd measure the torque 
required to move the table by attaching a lever to the hand wheel that is say 
1' long.  Set it horizontal and start hanging weight onto the end to get ft-lbs 
or ft-in until it turns. That's the torque required to overcome static 
friction.  Double that to choose your motor.

Say that is 1 ft-lb or 192 oz-in.If you choose 3:1 for your reduction ratio 
you get 600 oz-in.  Look at the motor torque curve (they are all different and 
if the supplier can't give you that buy one somewhere else) and see where the 
torque drops below 400 oz-in.  Say that's 180 RPM.  That's 3 RPS which 
multiplied by 2000 steps per rev for micro-stepping is 6000 steps/second which 
achieves your 1 RPS on the handle.

Or if you find it's 2 ft-lb or 400 oz-in choose a much larger motor like 1200 
oz-in
http://www.automationtechnologiesinc.com/download/9259/
Notice the curve at 3000 half steps per second is about 3.2NM.  That's 12,000 
steps per second (7.5RPS)  with 8 micro-steps per step well within the reach of 
even a parallel port controller and 450 oz-in.  That's well above the 1 RPS you 
need and even just 3:1 still gives you 1600 oz-in.

My two cents...
John Dammeyer

An alternative would be to provide more gearing, but I don't think it's
practical to get more than about a six to one ratio in a single belt
reduction and I'd like to avoid mechanical complexity if I can.

Thoughts?

Ken

Kenneth Lerman
55 Main Street
Newtown, CT 06470



On Fri, Feb 4, 2022 at 7:13 AM Chris Albertson 
wrote:


If looking for lowest cost solution you can us the old "Atom" computer to
control the grinder as long as you do not  need to run the mill and
grider at the same time.  Get an Eiternet interface Mesa card for the new
machine,  You need two config files, just load the one for the mill or the
one for the grinder.

Then someday you buy a second computer you only have to move the Ethernet
cable over.   The best option is a newer version of the Atom.  They seem to
sell for just under $200.   Finally Newegg.com always has many used oe
refurb PCs   Used PCs sourced locally can be a cheap as "free"

But 9ld PCs tend to burn up a lot of power.  I am trying to get mone to do
"wake on LAN" so it can not use power until I need to log onto it

On Thu, Feb 3, 2022 at 6:52 PM Kenneth Lerman  wrote:


I'm considering converting a surface grinder to CNC. To start, I'll
probably just convert the longitudinal and transverse axes.

I'll go with steppers for this -- I'm thinking NEMA-42 motors.

My current Bridgeport clone uses servos and Jon Elson's hardware on a
little Intel Atom Box. I'm thinking of using a Rpi for this. It will

need a

minimal display/control panel when completed, but initially will need a
display with touchscreen or mouse and possibly a keyboard. In the long

run,

some buttons. and perhaps an mpg might be useful.

I'd like to use a raw Rpi without adding special hardware directly. That
probably means using a USB or ethernet interface to control the steppers.
I'm thinking of using Mesa hardware.

Can someone suggest the most cost effective way to do this? (Although I
have to admit, that after buying the timing belts and pulleys, the
steppers, power supply, stepper drivers, ..., it's too late to be really
cost effective.). And the surface grinder only cost me $300.

Thanks,
Ken



Kenneth Lerman
55 Main Street
Newtown, CT 06470

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--

Chris Albertson
Redondo Beach, California

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Re: [Emc-users] What Would You Suggest?

[John Dammeyer]

In wanting to automate this grinder exactly how many axis do you want to 
control.
I can see the movement of the table back and forth at that 1 RPM.  I can see 
the cross slide at the end of each pass or pass and return?
Finally I guess depth might also be desired to a total depth?

If depth was adjusted manually then my ELS can be configured to do something 
like this:
http://www.autoartisans.com/ELS/
I'd set it up to turn the Z axis for BEGIN, END positions to move the table in 
the X axis directions.
I'd set the X axis for the 'depth' of each pass so it would move the table 
across using some of the parameters to fool it into not retracting but either 
moving further in for the pass in the other direction or moving the stone out 
of the way for the return.

But then that's just as easy with some simple G-Code and one of those far east 
CNC control boxes like this:
https://www.aliexpress.com/item/1005003646128482.html
For $140 Cdn with free shipping it's almost worth the risk to buy it and try 
it.  You need stepper motor drivers, power supply, motors and pulleys anyway.

> -Original Message-
> From: Martin Dobbins [mailto:tu...@hotmail.com]
> Sent: February-04-22 10:47 AM
> To: Enhanced Machine Controller (EMC)
> Subject: Re: [Emc-users] What Would You Suggest?
> 
> Hi Kenneth,
> 
> I don't know if this will be any use to you at all, and it's not Linuxcnc at 
> least not yet.
> 
> I an effort to emulate this:
> 
> https://www.youtube.com/watch?v=z4t8pmsnYow
> 
> Which is all powered by a PIC
> 
> I liked this but didn't want to use a PIC.  Tried first with an Arduino 
> because I had one on hand, but that just wasn't going to work.
> So, I moved to one of these and got the 3.2 version:
> 
> https://www.pjrc.com/teensy/
> 
> Partly because it has an excellent library for controlling steppers:
> 
> https://luni64.github.io/TeensyStep/
> 
> It's driving a NEMA 34 1805 oz/in through one of these
> 
> http://www.leadshine.com/uploadfile/down/ma860hm.pdf
> 
> which will work with AC or DC
> 
> So, one of these:
> 
> https://www.ebay.com/itm/194282558090
> 
> On the back of which is a jumper to set input voltage 240, 220, 200, 110.  
> With outputs on the back for 110v and 220v.  It's intended
> to be a travel item so your 110 volt stuff will work on 220v and vice versa. 
> A step up step down transformer.  If you lie to it you can
> feed it 118v to 120v (what comes out of my wall sockets) and get it to supply 
> lesser AC volts to the stepper driver.
> 
> If you're still awake?
> 
> I can get 2000 rpm plus out of that big stepper, but I don't need speed like 
> that, I need torque, so it's geared down 4:1 with the
> spindle it's driving (when the stepper's rotating at a leisurely 25 rpm the 
> spindle is turning at 100 rpm).  It's still an unfinished project.
> 
> I'm envious of that grinder.
> 
> Martin
> 
> 
> Kenneth Lerman wrote:
> 
> 
> Chris -- At my house, computers are all over the place. I think I have a
> spare atom floating around. Also a couple of other machines.
> Gene -- The grinder is here.
> <https://drive.google.com/file/d/1L8JiX0rtDZO99rVnQKNjUH7m-ZgFz2Un/view?usp=sharing>
> The
> ways look pretty clean. The only accessory I have is a magnetic chuck.
> 
> I don't really need a surface grinder, but no shop is complete without one.
> Once I started to use it, I realized that my right arm and shoulder really
> aren't suited to this type of manual work.
> 
> The longitudinal travel is just over a foot, and it takes about 3-1/2 turns
> of the crank to go that distance. I'm thinking around  a second per turn
> would be about the maximum. So, that's 60 RPM. I'm thinking of a 1:6 ratio
> on the timing belt pulleys, so that's 360 RPM at the stepper which is
> pretty slow. A full stepping rate would be 200 * 360/60 => 200 * 6 which is
> only 1200 steps per second.
> 
> An alternative would be to provide more gearing, but I don't think it's
> practical to get more than about a six to one ratio in a single belt
> reduction and I'd like to avoid mechanical complexity if I can.
> 
> Thoughts?
> 
> Ken
> 
> Kenneth Lerman
> 55 Main Street
> Newtown, CT 06470
> 
> 
> 
> On Fri, Feb 4, 2022 at 7:13 AM Chris Albertson 
> wrote:
> 
> > If looking for lowest cost solution you can us the old "Atom" computer to
> > control the grinder as long as you do not  need to run the mill and
> > grider at the same time.  Get an Eiternet interface Mesa card for the new
> > machine,  You need two config files, just load the one for the mill or the
> > one for the grinder.
> >
> > Then someday you buy a second computer you only have to move th

Re: [Emc-users] What Would You Suggest?

[gene heskett]

On Friday, February 4, 2022 12:47:30 PM EST Kenneth Lerman wrote:
> I don't think I'm ready for yet another hobby (3-D printing), so I
> think I'll just put an oversized motor and pulley.
> 
> Gene -- What stepper family are you using for the lathe? (A link,
> please.)
> 
> Regards,
> 
> Ken

The stepper motor and its drive are a combo that work together, itsd a 3 
phase motor that step only 1.2 degrees for a full step. The motor 
contains an an encoder that is only connected to the driver, not to 
LinuxCNC, so the driver knows the motors position error, which it uses to 
both keep the motor in step, and also track how hard it is working, which 
if the motor hit the immovable object, will in about 3 steps





   
, issue an alarm that you can use in you .hal file as an e-stop, which in 
my configs, also disables ALL machine power, and even reporting which 
axis faulted. That of course loses home. That's the programmers fault of 
course, so fix your program, hit f2 to re-enable the machine power, pull 
the tool holder off the post, rehome the machine, replace the tool 
holder, and restart the program. The driver also uses the error to 
control motor current. so the motor runs a bunch cooler in normal 
operation too.
ebay thinks they are being cute a 2 kilobyte links, but here's the first 
3nm kit I could find, 2nm and 1nm using the same driver is even less per 
axis,


Which may or may not work, search for "3 phase stepper servo"

They are now available clear up to nema 52, so the motor makers are 
getting right with it these days, a month back the link above to 3NM plus 
1 and 2's too, was all that was available.

Big motors still take your house payment though. But these are nice, and 
the 3nm should be big enough. Scan down the search results till you see a 
gold controller as part of the kit. Perhaps the blue one is ok, but I've 
no experience with that puppy.

You'll need a 42 volt psu for these, about $75 for one big enough to run 
both motors as these, at full song, need 3.5 amps/phase throttling down 
to an amp or less at light loads. The 15 amp version s/b enough, with a 
bit of headroom leftover.

Take care and stay well.

Cheers, Gene Heskett.
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis
Genes Web page 





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Re: [Emc-users] What Would You Suggest?

[Martin Dobbins]

Hi Kenneth,

I don't know if this will be any use to you at all, and it's not Linuxcnc at 
least not yet.

I an effort to emulate this:

https://www.youtube.com/watch?v=z4t8pmsnYow

Which is all powered by a PIC

I liked this but didn't want to use a PIC.  Tried first with an Arduino because 
I had one on hand, but that just wasn't going to work.  So, I moved to one of 
these and got the 3.2 version:

https://www.pjrc.com/teensy/

Partly because it has an excellent library for controlling steppers:

https://luni64.github.io/TeensyStep/

It's driving a NEMA 34 1805 oz/in through one of these

http://www.leadshine.com/uploadfile/down/ma860hm.pdf

which will work with AC or DC

So, one of these:

https://www.ebay.com/itm/194282558090

On the back of which is a jumper to set input voltage 240, 220, 200, 110.  With 
outputs on the back for 110v and 220v.  It's intended to be a travel item so 
your 110 volt stuff will work on 220v and vice versa. A step up step down 
transformer.  If you lie to it you can feed it 118v to 120v (what comes out of 
my wall sockets) and get it to supply lesser AC volts to the stepper driver.

If you're still awake?

I can get 2000 rpm plus out of that big stepper, but I don't need speed like 
that, I need torque, so it's geared down 4:1 with the spindle it's driving 
(when the stepper's rotating at a leisurely 25 rpm the spindle is turning at 
100 rpm).  It's still an unfinished project.

I'm envious of that grinder.

Martin


Kenneth Lerman wrote:


Chris -- At my house, computers are all over the place. I think I have a
spare atom floating around. Also a couple of other machines.
Gene -- The grinder is here.

The
ways look pretty clean. The only accessory I have is a magnetic chuck.

I don't really need a surface grinder, but no shop is complete without one.
Once I started to use it, I realized that my right arm and shoulder really
aren't suited to this type of manual work.

The longitudinal travel is just over a foot, and it takes about 3-1/2 turns
of the crank to go that distance. I'm thinking around  a second per turn
would be about the maximum. So, that's 60 RPM. I'm thinking of a 1:6 ratio
on the timing belt pulleys, so that's 360 RPM at the stepper which is
pretty slow. A full stepping rate would be 200 * 360/60 => 200 * 6 which is
only 1200 steps per second.

An alternative would be to provide more gearing, but I don't think it's
practical to get more than about a six to one ratio in a single belt
reduction and I'd like to avoid mechanical complexity if I can.

Thoughts?

Ken

Kenneth Lerman
55 Main Street
Newtown, CT 06470



On Fri, Feb 4, 2022 at 7:13 AM Chris Albertson 
wrote:

> If looking for lowest cost solution you can us the old "Atom" computer to
> control the grinder as long as you do not  need to run the mill and
> grider at the same time.  Get an Eiternet interface Mesa card for the new
> machine,  You need two config files, just load the one for the mill or the
> one for the grinder.
>
> Then someday you buy a second computer you only have to move the Ethernet
> cable over.   The best option is a newer version of the Atom.  They seem to
> sell for just under $200.   Finally Newegg.com always has many used oe
> refurb PCs   Used PCs sourced locally can be a cheap as "free"
>
> But 9ld PCs tend to burn up a lot of power.  I am trying to get mone to do
> "wake on LAN" so it can not use power until I need to log onto it
>
> On Thu, Feb 3, 2022 at 6:52 PM Kenneth Lerman  wrote:
>
> > I'm considering converting a surface grinder to CNC. To start, I'll
> > probably just convert the longitudinal and transverse axes.
> >
> > I'll go with steppers for this -- I'm thinking NEMA-42 motors.
> >
> > My current Bridgeport clone uses servos and Jon Elson's hardware on a
> > little Intel Atom Box. I'm thinking of using a Rpi for this. It will
> need a
> > minimal display/control panel when completed, but initially will need a
> > display with touchscreen or mouse and possibly a keyboard. In the long
> run,
> > some buttons. and perhaps an mpg might be useful.
> >
> > I'd like to use a raw Rpi without adding special hardware directly. That
> > probably means using a USB or ethernet interface to control the steppers.
> > I'm thinking of using Mesa hardware.
> >
> > Can someone suggest the most cost effective way to do this? (Although I
> > have to admit, that after buying the timing belts and pulleys, the
> > steppers, power supply, stepper drivers, ..., it's too late to be really
> > cost effective.). And the surface grinder only cost me $300.
> >
> > Thanks,
> > Ken
> >
> >
> >
> > Kenneth Lerman
> > 55 Main Street
> > Newtown, CT 06470
> >
> > ___
> > Emc-users mailing list
> > Emc-users@lists.sourceforge.net
> > https://lists.sourceforge.net/lists/listinfo/emc-users
> >
>
>
> --
>
> Chris Albertson
> Redondo Beach, 

Re: [Emc-users] What Would You Suggest?

[Kenneth Lerman]

I don't think I'm ready for yet another hobby (3-D printing), so I think
I'll just put an oversized motor and pulley.

Gene -- What stepper family are you using for the lathe? (A link, please.)

Regards,

Ken


Kenneth Lerman
55 Main Street
Newtown, CT 06470



On Fri, Feb 4, 2022 at 12:25 PM gene heskett  wrote:

> On Friday, February 4, 2022 10:31:23 AM EST Kenneth Lerman wrote:
> > Chris -- At my house, computers are all over the place. I think I have
> > a spare atom floating around. Also a couple of other machines.
> > Gene -- The grinder is here.
> >  > ?usp=sharing> The
> > ways look pretty clean. The only accessory I have is a magnetic chuck.
> >
> Cute little thing Ken. And with a mag chuck, you stole it.
>
> > I don't really need a surface grinder, but no shop is complete without
> > one. Once I started to use it, I realized that my right arm and
> > shoulder really aren't suited to this type of manual work.
>
> As the senior member here, I get to complain first :) But you're excused
> ;o)
> As to you gear ratio problems, I agree, which is why I designed a small
> variation of a harmonic drive for use on the A axis of my 6040 mill. But
> its too small I think for what you want to do. But the 3d slicer "cura"
> can scale, and if you've a 3d printer that can handle PETG, one of the
> higher temp plastics, on an everyday basis, this thing scaled up 200%
> should do the job for you ok. Gear ratio, about as high as it can go at
> the native size is 50/1 but could be as low as 30/1.
>
> I'm driving it with a 1NM version of the new 3 phase stepper/servo's, but
> that family of servo's can be had at 3NM or about 425 oz/in, as all have
> an 8mm diameter d-flated shaft, which I put on my milling machine, power
> up to lock it and make the flat bigger, so the measurement from flat to
> back of the round is 6.5mm. With a printed armature hub that grips the
> whole shaft its strong enough in PETG that no hard to machine metal hub
> insert is needed. In my size, I can make 2 of them out of a $20 kilo of
> PETG, and a small bottle of crosman bb's, or about 15$ a drive. At a
> scaleup for what you need, about 200%, will x4 the amount of filament,
> and probably x4 the print time too but I don't see why it won't work if
> you wanted to try it. My whole idea is cheap, if it breaks, print
> another.
>
> > The longitudinal travel is just over a foot, and it takes about 3-1/2
> > turns of the crank to go that distance. I'm thinking around  a second
> > per turn would be about the maximum. So, that's 60 RPM. I'm thinking
> > of a 1:6 ratio on the timing belt pulleys, so that's 360 RPM at the
> > stepper which is pretty slow. A full stepping rate would be 200 *
> > 360/60 => 200 * 6 which is only 1200 steps per second.
> >
> > An alternative would be to provide more gearing, but I don't think it's
> > practical to get more than about a six to one ratio in a single belt
> > reduction and I'd like to avoid mechanical complexity if I can.
>
> OpenSCAD, which I used to design this, is quite capable of doing any part
> that fits on the bed of your 3d printer. And if at 87 I can learn it, I'm
> convinced you could too.
>
> Two OpenSCAD master files, are text files, and this drive and the driver
> sprocket to replace the alu crap that came on this A drive originally,
> total about 1400 LOC, several hundred of which is comments so I can
> figure out a month from now, what the heck I was doing. Lots of it is
> from thingiverse, and modified by me. But the final version hasn't made
> it to my web site, yet... Something about the only time a program is
> finished is when someone shoots the programmer.
>
> I am also driving my converted 11x54 Sheldon lathe with the 3NM and 2NM
> versions of this motor/driver stepper/servo. And driven by LinuxCNC
> running on a rpi4, its doing dance steps that it could not do 80 years
> ago when it was shipped to the navy. Including correcting for the 13 thou
> of bed wear right in front of the chuck. This lathe has been rode hard,
> thrown across the truck bed going around a corner too fast and put away
> wet long before it followed me home in a cargo van.
>
> If interested, give me you PM address and I'll email the .scad to you.
>
> > Thoughts?
>
> Take care and stay well.
>
> > Ken
> >
> > Kenneth Lerman
> > 55 Main Street
> > Newtown, CT 06470
> >
> Cheers, Gene Heskett.
> --
> "There are four boxes to be used in defense of liberty:
>  soap, ballot, jury, and ammo. Please use in that order."
> -Ed Howdershelt (Author, 1940)
> If we desire respect for the law, we must first make the law respectable.
>  - Louis D. Brandeis
> Genes Web page 
>
>
>
>
>
> ___
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>

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Re: [Emc-users] What Would You Suggest?

[Rafael Skodlar]

Hi Ken,

On 2/3/22 16:54, Kenneth Lerman wrote:

I'm considering converting a surface grinder to CNC. To start, I'll
probably just convert the longitudinal and transverse axes.

I'll go with steppers for this -- I'm thinking NEMA-42 motors.

My current Bridgeport clone uses servos and Jon Elson's hardware on a
little Intel Atom Box. I'm thinking of using a Rpi for this. It will need a
minimal display/control panel when completed, but initially will need a
display with touchscreen or mouse and possibly a keyboard. In the long run,
some buttons. and perhaps an mpg might be useful.





I'd like to use a raw Rpi without adding special hardware directly. That
probably means using a USB or ethernet interface to control the steppers.
I'm thinking of using Mesa hardware.

Can someone suggest the most cost effective way to do this? (Although I


Control steppers with Arduino and appropriate size drivers 
https://dronebotworkshop.com/stepper-motors-with-arduino/


and Rpi for GUI part and connections over the network for file sharing, 
backups and GUI as needed.


While these two are NOT industrial grade, they should be able to handle 
your project.



have to admit, that after buying the timing belts and pulleys, the
steppers, power supply, stepper drivers, ..., it's too late to be really
cost effective.). And the surface grinder only cost me $300.

Thanks,
Ken


Recommended reading:
https://openbuilds.com/
https://www.openplcproject.com/runtime/raspberry-pi/
https://www.openhardware.io/

Modern PC motherboards and freaking parallel port are a total waste for 
CNC (retrofit) in 202x! Using multicore CPUs with GBs of RAM to spin 
stepper motors with obsolete G-code is nuts!


Good luck,

Rafael Skodlar
Exclusive Linux user and Open Source Software supporter since Feb 1994


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Re: [Emc-users] What Would You Suggest?

[gene heskett]

On Friday, February 4, 2022 10:31:23 AM EST Kenneth Lerman wrote:
> Chris -- At my house, computers are all over the place. I think I have
> a spare atom floating around. Also a couple of other machines.
> Gene -- The grinder is here.
>  ?usp=sharing> The
> ways look pretty clean. The only accessory I have is a magnetic chuck.
> 
Cute little thing Ken. And with a mag chuck, you stole it.

> I don't really need a surface grinder, but no shop is complete without
> one. Once I started to use it, I realized that my right arm and
> shoulder really aren't suited to this type of manual work.

As the senior member here, I get to complain first :) But you're excused 
;o)
As to you gear ratio problems, I agree, which is why I designed a small 
variation of a harmonic drive for use on the A axis of my 6040 mill. But 
its too small I think for what you want to do. But the 3d slicer "cura" 
can scale, and if you've a 3d printer that can handle PETG, one of the 
higher temp plastics, on an everyday basis, this thing scaled up 200% 
should do the job for you ok. Gear ratio, about as high as it can go at 
the native size is 50/1 but could be as low as 30/1.

I'm driving it with a 1NM version of the new 3 phase stepper/servo's, but 
that family of servo's can be had at 3NM or about 425 oz/in, as all have 
an 8mm diameter d-flated shaft, which I put on my milling machine, power 
up to lock it and make the flat bigger, so the measurement from flat to 
back of the round is 6.5mm. With a printed armature hub that grips the 
whole shaft its strong enough in PETG that no hard to machine metal hub 
insert is needed. In my size, I can make 2 of them out of a $20 kilo of 
PETG, and a small bottle of crosman bb's, or about 15$ a drive. At a 
scaleup for what you need, about 200%, will x4 the amount of filament, 
and probably x4 the print time too but I don't see why it won't work if 
you wanted to try it. My whole idea is cheap, if it breaks, print 
another.

> The longitudinal travel is just over a foot, and it takes about 3-1/2
> turns of the crank to go that distance. I'm thinking around  a second
> per turn would be about the maximum. So, that's 60 RPM. I'm thinking
> of a 1:6 ratio on the timing belt pulleys, so that's 360 RPM at the
> stepper which is pretty slow. A full stepping rate would be 200 *
> 360/60 => 200 * 6 which is only 1200 steps per second.
> 
> An alternative would be to provide more gearing, but I don't think it's
> practical to get more than about a six to one ratio in a single belt
> reduction and I'd like to avoid mechanical complexity if I can.

OpenSCAD, which I used to design this, is quite capable of doing any part 
that fits on the bed of your 3d printer. And if at 87 I can learn it, I'm 
convinced you could too.

Two OpenSCAD master files, are text files, and this drive and the driver 
sprocket to replace the alu crap that came on this A drive originally, 
total about 1400 LOC, several hundred of which is comments so I can 
figure out a month from now, what the heck I was doing. Lots of it is 
from thingiverse, and modified by me. But the final version hasn't made 
it to my web site, yet... Something about the only time a program is 
finished is when someone shoots the programmer.

I am also driving my converted 11x54 Sheldon lathe with the 3NM and 2NM 
versions of this motor/driver stepper/servo. And driven by LinuxCNC 
running on a rpi4, its doing dance steps that it could not do 80 years 
ago when it was shipped to the navy. Including correcting for the 13 thou 
of bed wear right in front of the chuck. This lathe has been rode hard, 
thrown across the truck bed going around a corner too fast and put away 
wet long before it followed me home in a cargo van.

If interested, give me you PM address and I'll email the .scad to you.

> Thoughts?

Take care and stay well.
 
> Ken
> 
> Kenneth Lerman
> 55 Main Street
> Newtown, CT 06470
> 
Cheers, Gene Heskett.
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis
Genes Web page 





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Re: [Emc-users] What Would You Suggest?

[John Dammeyer]

> From: Kenneth Lerman [mailto:ler...@se-ltd.com]
> The longitudinal travel is just over a foot, and it takes about 3-1/2 turns
> of the crank to go that distance. I'm thinking around  a second per turn
> would be about the maximum. So, that's 60 RPM. I'm thinking of a 1:6 ratio
> on the timing belt pulleys, so that's 360 RPM at the stepper which is
> pretty slow. A full stepping rate would be 200 * 360/60 => 200 * 6 which is
> only 1200 steps per second.

You won't want to run full step.  A minimum should be 8 micro-steps/step to 
avoid resonance and loss of position or lockup.   I'd measure the torque 
required to move the table by attaching a lever to the hand wheel that is say 
1' long.  Set it horizontal and start hanging weight onto the end to get ft-lbs 
or ft-in until it turns. That's the torque required to overcome static 
friction.  Double that to choose your motor.

Say that is 1 ft-lb or 192 oz-in.If you choose 3:1 for your reduction ratio 
you get 600 oz-in.  Look at the motor torque curve (they are all different and 
if the supplier can't give you that buy one somewhere else) and see where the 
torque drops below 400 oz-in.  Say that's 180 RPM.  That's 3 RPS which 
multiplied by 2000 steps per rev for micro-stepping is 6000 steps/second which 
achieves your 1 RPS on the handle.

Or if you find it's 2 ft-lb or 400 oz-in choose a much larger motor like 1200 
oz-in
http://www.automationtechnologiesinc.com/download/9259/
Notice the curve at 3000 half steps per second is about 3.2NM.  That's 12,000 
steps per second (7.5RPS)  with 8 micro-steps per step well within the reach of 
even a parallel port controller and 450 oz-in.  That's well above the 1 RPS you 
need and even just 3:1 still gives you 1600 oz-in.

My two cents...
John Dammeyer
> 
> An alternative would be to provide more gearing, but I don't think it's
> practical to get more than about a six to one ratio in a single belt
> reduction and I'd like to avoid mechanical complexity if I can.
> 
> Thoughts?
> 
> Ken
> 
> Kenneth Lerman
> 55 Main Street
> Newtown, CT 06470
> 
> 
> 
> On Fri, Feb 4, 2022 at 7:13 AM Chris Albertson 
> wrote:
> 
> > If looking for lowest cost solution you can us the old "Atom" computer to
> > control the grinder as long as you do not  need to run the mill and
> > grider at the same time.  Get an Eiternet interface Mesa card for the new
> > machine,  You need two config files, just load the one for the mill or the
> > one for the grinder.
> >
> > Then someday you buy a second computer you only have to move the Ethernet
> > cable over.   The best option is a newer version of the Atom.  They seem to
> > sell for just under $200.   Finally Newegg.com always has many used oe
> > refurb PCs   Used PCs sourced locally can be a cheap as "free"
> >
> > But 9ld PCs tend to burn up a lot of power.  I am trying to get mone to do
> > "wake on LAN" so it can not use power until I need to log onto it
> >
> > On Thu, Feb 3, 2022 at 6:52 PM Kenneth Lerman  wrote:
> >
> > > I'm considering converting a surface grinder to CNC. To start, I'll
> > > probably just convert the longitudinal and transverse axes.
> > >
> > > I'll go with steppers for this -- I'm thinking NEMA-42 motors.
> > >
> > > My current Bridgeport clone uses servos and Jon Elson's hardware on a
> > > little Intel Atom Box. I'm thinking of using a Rpi for this. It will
> > need a
> > > minimal display/control panel when completed, but initially will need a
> > > display with touchscreen or mouse and possibly a keyboard. In the long
> > run,
> > > some buttons. and perhaps an mpg might be useful.
> > >
> > > I'd like to use a raw Rpi without adding special hardware directly. That
> > > probably means using a USB or ethernet interface to control the steppers.
> > > I'm thinking of using Mesa hardware.
> > >
> > > Can someone suggest the most cost effective way to do this? (Although I
> > > have to admit, that after buying the timing belts and pulleys, the
> > > steppers, power supply, stepper drivers, ..., it's too late to be really
> > > cost effective.). And the surface grinder only cost me $300.
> > >
> > > Thanks,
> > > Ken
> > >
> > >
> > >
> > > Kenneth Lerman
> > > 55 Main Street
> > > Newtown, CT 06470
> > >
> > > ___
> > > Emc-users mailing list
> > > Emc-users@lists.sourceforge.net
> > > https://lists.sourceforge.net/lists/listinfo/emc-users
> > >
> >
> >
> > --
> >
> > Chris Albertson
> > Redondo Beach, California
> >
> > ___
> > Emc-users mailing list
> > Emc-users@lists.sourceforge.net
> > https://lists.sourceforge.net/lists/listinfo/emc-users
> >
> 
> ___
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Re: [Emc-users] What Would You Suggest?

[Kenneth Lerman]

Chris -- At my house, computers are all over the place. I think I have a
spare atom floating around. Also a couple of other machines.
Gene -- The grinder is here.

The
ways look pretty clean. The only accessory I have is a magnetic chuck.

I don't really need a surface grinder, but no shop is complete without one.
Once I started to use it, I realized that my right arm and shoulder really
aren't suited to this type of manual work.

The longitudinal travel is just over a foot, and it takes about 3-1/2 turns
of the crank to go that distance. I'm thinking around  a second per turn
would be about the maximum. So, that's 60 RPM. I'm thinking of a 1:6 ratio
on the timing belt pulleys, so that's 360 RPM at the stepper which is
pretty slow. A full stepping rate would be 200 * 360/60 => 200 * 6 which is
only 1200 steps per second.

An alternative would be to provide more gearing, but I don't think it's
practical to get more than about a six to one ratio in a single belt
reduction and I'd like to avoid mechanical complexity if I can.

Thoughts?

Ken

Kenneth Lerman
55 Main Street
Newtown, CT 06470



On Fri, Feb 4, 2022 at 7:13 AM Chris Albertson 
wrote:

> If looking for lowest cost solution you can us the old "Atom" computer to
> control the grinder as long as you do not  need to run the mill and
> grider at the same time.  Get an Eiternet interface Mesa card for the new
> machine,  You need two config files, just load the one for the mill or the
> one for the grinder.
>
> Then someday you buy a second computer you only have to move the Ethernet
> cable over.   The best option is a newer version of the Atom.  They seem to
> sell for just under $200.   Finally Newegg.com always has many used oe
> refurb PCs   Used PCs sourced locally can be a cheap as "free"
>
> But 9ld PCs tend to burn up a lot of power.  I am trying to get mone to do
> "wake on LAN" so it can not use power until I need to log onto it
>
> On Thu, Feb 3, 2022 at 6:52 PM Kenneth Lerman  wrote:
>
> > I'm considering converting a surface grinder to CNC. To start, I'll
> > probably just convert the longitudinal and transverse axes.
> >
> > I'll go with steppers for this -- I'm thinking NEMA-42 motors.
> >
> > My current Bridgeport clone uses servos and Jon Elson's hardware on a
> > little Intel Atom Box. I'm thinking of using a Rpi for this. It will
> need a
> > minimal display/control panel when completed, but initially will need a
> > display with touchscreen or mouse and possibly a keyboard. In the long
> run,
> > some buttons. and perhaps an mpg might be useful.
> >
> > I'd like to use a raw Rpi without adding special hardware directly. That
> > probably means using a USB or ethernet interface to control the steppers.
> > I'm thinking of using Mesa hardware.
> >
> > Can someone suggest the most cost effective way to do this? (Although I
> > have to admit, that after buying the timing belts and pulleys, the
> > steppers, power supply, stepper drivers, ..., it's too late to be really
> > cost effective.). And the surface grinder only cost me $300.
> >
> > Thanks,
> > Ken
> >
> >
> >
> > Kenneth Lerman
> > 55 Main Street
> > Newtown, CT 06470
> >
> > ___
> > Emc-users mailing list
> > Emc-users@lists.sourceforge.net
> > https://lists.sourceforge.net/lists/listinfo/emc-users
> >
>
>
> --
>
> Chris Albertson
> Redondo Beach, California
>
> ___
> Emc-users mailing list
> Emc-users@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/emc-users
>

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Re: [Emc-users] What Would You Suggest?

[Chris Albertson]

If looking for lowest cost solution you can us the old "Atom" computer to
control the grinder as long as you do not  need to run the mill and
grider at the same time.  Get an Eiternet interface Mesa card for the new
machine,  You need two config files, just load the one for the mill or the
one for the grinder.

Then someday you buy a second computer you only have to move the Ethernet
cable over.   The best option is a newer version of the Atom.  They seem to
sell for just under $200.   Finally Newegg.com always has many used oe
refurb PCs   Used PCs sourced locally can be a cheap as "free"

But 9ld PCs tend to burn up a lot of power.  I am trying to get mone to do
"wake on LAN" so it can not use power until I need to log onto it

On Thu, Feb 3, 2022 at 6:52 PM Kenneth Lerman  wrote:

> I'm considering converting a surface grinder to CNC. To start, I'll
> probably just convert the longitudinal and transverse axes.
>
> I'll go with steppers for this -- I'm thinking NEMA-42 motors.
>
> My current Bridgeport clone uses servos and Jon Elson's hardware on a
> little Intel Atom Box. I'm thinking of using a Rpi for this. It will need a
> minimal display/control panel when completed, but initially will need a
> display with touchscreen or mouse and possibly a keyboard. In the long run,
> some buttons. and perhaps an mpg might be useful.
>
> I'd like to use a raw Rpi without adding special hardware directly. That
> probably means using a USB or ethernet interface to control the steppers.
> I'm thinking of using Mesa hardware.
>
> Can someone suggest the most cost effective way to do this? (Although I
> have to admit, that after buying the timing belts and pulleys, the
> steppers, power supply, stepper drivers, ..., it's too late to be really
> cost effective.). And the surface grinder only cost me $300.
>
> Thanks,
> Ken
>
>
>
> Kenneth Lerman
> 55 Main Street
> Newtown, CT 06470
>
> ___
> Emc-users mailing list
> Emc-users@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/emc-users
>


-- 

Chris Albertson
Redondo Beach, California

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Re: [Emc-users] What Would You Suggest?

[gene heskett]

On Thursday, February 3, 2022 10:08:54 PM EST Robin Szemeti via Emc-users 
wrote:
> If using microstepping drives, you will struggle to get fast enough
> pulses out without external pulsgen ... you need around 20kHz to get
> the motors up to corner speed .. below that, you are not getting max
> power from the motors, so I think you will struggle.
> 
> On Fri, 4 Feb 2022 at 02:49, Kenneth Lerman  wrote:
> > I'm considering converting a surface grinder to CNC. To start, I'll
> > probably just convert the longitudinal and transverse axes.
> > 
> > I'll go with steppers for this -- I'm thinking NEMA-42 motors.
> > 
nema 42's available are too high inductance, an old 1600 inch nema 34 was 
only able to get to 29 ipm microstepped at /8 on my g0704's 50+ lb z 
axis, but a 940 now drives it at 120 ipm with a dedicated AC powered 
stepper driver making around 130 volts.

It takes voltage to drive a big stepper fast.

And that is limited by the cost of that higher voltage driver. Using an 
rpi implies using a mesa card, which removes the step rate limit, but 
bigger motors with their higher inductance implies $200+ per axis self 
powered drivers.

> > My current Bridgeport clone uses servos and Jon Elson's hardware on a
> > little Intel Atom Box. I'm thinking of using a Rpi for this. It will
> > need a minimal display/control panel when completed, but initially
> > will need a display with touchscreen or mouse and possibly a
> > keyboard. In the long run, some buttons. and perhaps an mpg might be
> > useful.
> > 
> > I'd like to use a raw Rpi without adding special hardware directly.
> > That probably means using a USB or ethernet interface to control the
> > steppers. I'm thinking of using Mesa hardware.
> > 
> > Can someone suggest the most cost effective way to do this? (Although
> > I have to admit, that after buying the timing belts and pulleys, the
> > steppers, power supply, stepper drivers, ..., it's too late to be
> > really cost effective.). And the surface grinder only cost me $300.

Is its bed still flat and true? If, it was a steal at $300.

> > Thanks,
> > Ken
> > 
> > 
> > 
> > Kenneth Lerman
> > 55 Main Street
> > Newtown, CT 06470
> > 
> > ___
> > Emc-users mailing list
> > Emc-users@lists.sourceforge.net
> > https://lists.sourceforge.net/lists/listinfo/emc-users
> 
> ___
> Emc-users mailing list
> Emc-users@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/emc-users
> .


Cheers, Gene Heskett.
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis
Genes Web page 





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Re: [Emc-users] What Would You Suggest?

[Robin Szemeti via Emc-users]

If using microstepping drives, you will struggle to get fast enough pulses
out without external pulsgen ... you need around 20kHz to get the motors up
to corner speed .. below that, you are not getting max power from the
motors, so I think you will struggle.

On Fri, 4 Feb 2022 at 02:49, Kenneth Lerman  wrote:

> I'm considering converting a surface grinder to CNC. To start, I'll
> probably just convert the longitudinal and transverse axes.
>
> I'll go with steppers for this -- I'm thinking NEMA-42 motors.
>
> My current Bridgeport clone uses servos and Jon Elson's hardware on a
> little Intel Atom Box. I'm thinking of using a Rpi for this. It will need a
> minimal display/control panel when completed, but initially will need a
> display with touchscreen or mouse and possibly a keyboard. In the long run,
> some buttons. and perhaps an mpg might be useful.
>
> I'd like to use a raw Rpi without adding special hardware directly. That
> probably means using a USB or ethernet interface to control the steppers.
> I'm thinking of using Mesa hardware.
>
> Can someone suggest the most cost effective way to do this? (Although I
> have to admit, that after buying the timing belts and pulleys, the
> steppers, power supply, stepper drivers, ..., it's too late to be really
> cost effective.). And the surface grinder only cost me $300.
>
> Thanks,
> Ken
>
>
>
> Kenneth Lerman
> 55 Main Street
> Newtown, CT 06470
>
> ___
> Emc-users mailing list
> Emc-users@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/emc-users
>

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[Emc-users] What Would You Suggest?

[Kenneth Lerman]

I'm considering converting a surface grinder to CNC. To start, I'll
probably just convert the longitudinal and transverse axes.

I'll go with steppers for this -- I'm thinking NEMA-42 motors.

My current Bridgeport clone uses servos and Jon Elson's hardware on a
little Intel Atom Box. I'm thinking of using a Rpi for this. It will need a
minimal display/control panel when completed, but initially will need a
display with touchscreen or mouse and possibly a keyboard. In the long run,
some buttons. and perhaps an mpg might be useful.

I'd like to use a raw Rpi without adding special hardware directly. That
probably means using a USB or ethernet interface to control the steppers.
I'm thinking of using Mesa hardware.

Can someone suggest the most cost effective way to do this? (Although I
have to admit, that after buying the timing belts and pulleys, the
steppers, power supply, stepper drivers, ..., it's too late to be really
cost effective.). And the surface grinder only cost me $300.

Thanks,
Ken



Kenneth Lerman
55 Main Street
Newtown, CT 06470

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