Re: [Emc-users] Connecting thin gears to shafts

[Dave Cole]

So basically you made your own taperlock setup?
Very nice.

Dave

On 1/25/2017 5:48 PM, andy pugh wrote:
> (As discussed on IRC a few days back).
> I had a bit of a puzzle about how to mount some thin gears to coaxial
> shafts. I came up with something that seems to work, and wrote it up
> on Blogger so that future folk might get more Goolg-luck than I got.
> http://bodgesoc.blogspot.co.uk/2017/01/gears.html
>

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Re: [Emc-users] Voltage/Motor RPM Relationship with Brushless Drives

[Stephen Dubovsky]

On Wed, Jan 25, 2017 at 10:25 PM, Jon Elson  wrote:

> Field weakening is not possible on permanent magnet
> brushless motors.
>
>
It actually is.  Apply current in the D axis will oppose and reduce the net
flux in the gap.  Move a coil in between two N poles permanent magnets
facing each other and you will get no voltage as the field is zero at the
center.  You risk demagnetizing the magnets at high temp.  You also risk a
fault in the drive shutting off all the fets/igbts while running near top
speed, loosing the field weakening, back emf goes to full strength, and
rectified voltage back through the bridge becomes MUCH higher than the DC
bus can handle.  Been there done that w/ a eurocopter APU starter we
designed w/ Kollmorgen. They had to add an output contactor that opens for
a drive fault.
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Re: [Emc-users] Voltage/Motor RPM Relationship with Brushless Drives

[Jon Elson]

On 01/25/2017 11:22 AM, Nicklas Karlsson wrote:
> For permanent magnet motors there is a rather linear correlation between RPM 
> and voltage although field weakening might be possible to lower voltage then 
> loaded below rated torque.
>
>
Field weakening is not possible on permanent magnet 
brushless motors.

Jon

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[Emc-users] Connecting thin gears to shafts

[andy pugh]

(As discussed on IRC a few days back).
I had a bit of a puzzle about how to mount some thin gears to coaxial
shafts. I came up with something that seems to work, and wrote it up
on Blogger so that future folk might get more Goolg-luck than I got.
http://bodgesoc.blogspot.co.uk/2017/01/gears.html

-- 
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designed for the especial use of mechanical geniuses, daredevils and
lunatics."
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Re: [Emc-users] Leadshine closed loop steppers

[Gene Heskett]

On Wednesday 25 January 2017 12:56:34 Jon Elson wrote:

> On 01/25/2017 03:07 AM, Klemen Živkovič wrote:
> > I just checked:
> > http://www.automationtechnologiesinc.com/products-page/ac-servo-moto
> >rs/the-ac-servo-driver-ac-servo-motor-400w-set
> >
> > to replace my 12Nm steppers - the torque on this motor is 1.27 Nm
> > (they rate is as high torque servos) - and is not near 12Nm, that my
> > nema42 steppers now provide.
> > Guess I need gearbox but this would introduce backlash  - or there
> > are some brushless servos with around 12Nm torque available?
>
> Peak torque is 3.8 nm.
>
> > Any ideas who can provide 12Nm servos if they exist at all?
>
> You can look for Fanuc motors. The old 1-0SP is rated at 15
> nm peak. The (alpha)M6/3000 is rated at 6 nm continuous
> stall, so should do 12 nm peak easily. The (alpha)6/2000 and
> (alpha)6/3000 have similar ratings.
>
> And, your NEMA42 steppers may have 12 nm HOLDING TORQUE, but
> they rapidly lost torque as the speed increases. Depending
> on the driver, you may only have 6 nm torque available at
> somewhere between 100 - 300 RPM.
>
> Jon
> Jon

Thats the problem I had with that 1600oz/in on top of the G0704.  
Replaced it with a shorter nema34 that claimed in the mid-900 oz/in 
territory, and went from 28 ipm to 90 something ipm up and down if the 
post is freshly oiled. But I changed the drive to one of the line 
powered gizmos the said it was a bit higher powered than the DM860 drive 
at 60 volts, but the DM860 can run it just short of 3k revs sitting 
loose on the table. And it is now running the carriage on the Sheldon 
with a 30/40 geardown at 90 ipm, happy as a clam...

===

Now I need the next higher current step up from an M542T, something that 
can shove 5+ amps steady at just north of 45 volts into the nema23 
version of these motors I just bought.

The smaller, 8 wire nema24 motor has an 8mm shaft, whereas the bigger 
nema23 has a 10mm shaft. and my spare 20 tooth has a 10mm hub.  But no 
tailshaft for a damper, or room for one if it did have a tailshaft.

So I guess I'm going shopping on fleabay again. Get me a 20 tooth pulley 
with an 8m hub too.

I did get a tachometer dial, and 3 tally leds under it running. One tally 
turns green when a signal is sent out to turn on two of the chinese 40 
amp SSR's, the vfd will be across the full 254 when they are on, and the 
psu's for the xy motors will be on just one leg. The idea being to have 
a way I can park things for the night without leaving the motors powered 
up. Triggered by motion.motion-enable.  The fwd/reverse leds are 
switched by the encoder output.

Cheers, Gene Heskett
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-Ed Howdershelt (Author)
Genes Web page 

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Re: [Emc-users] Voltage/Motor RPM Relationship with Brushless Drives

[Jon Elson]

On 01/25/2017 06:10 AM, Steve from Tube Gauge wrote:
> Hi:
>   
> I have a CNC mill that I am considering replacing the control with LinuxCNC.  
> The motors are the red cap Fanuc units.  I have enquired on this mailing list 
> about using the existing servo amps and motors.  From all the replies and 
> help (thank you very much)  I haved concluded that a good solution for me is 
> to remove the Fanuc encoders and amps  and replace them with suitable units 
> that can communicate on an industry standard format.  To that end I am 
> considering using some AMT31 programmable encoders by CUI (or other encoder 
> suitable for 8 pole motors) and some BE40A8 AMC amps that I have sitting on 
> my shelf.
>   
> I am aware of the rpm/voltage relationship with brush DC motors.  Generally, 
> as the voltage rises the motor rpm increases a proportional amount.  How does 
> the voltage influence the performance of the brushless motor?  The Fanuc 
> motors are 5S models, 126 V (DC?), 5.8A stall.  The BE40A8 have a maximum 
> running voltage of 80 VDC.  Will running the motors at the lower voltage 
> result in dramatically reduced performance?  Will it cause other electrical 
> problems like an excessive rise in current demand by the motor?
>   
>
Supply voltage limits speed, current limits torque.  So, 
running a 126 V motor on 80 V will limit you to 80/126 of 
the rated speed. So, if the motor is rated for 2000 RPM at 
126 V, you will only get 1250 RPM.  Directly driving a 5 TPI 
leadscrew, you would get 250 IPM linear traverse.

It will not increase the current demand of the motor at 
all.  (That would apply to an induction motor, only.)

Jon

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Re: [Emc-users] Leadshine closed loop steppers

[Jon Elson]

On 01/25/2017 03:07 AM, Klemen Živkovič wrote:
> I just checked:
> http://www.automationtechnologiesinc.com/products-page/ac-servo-motors/the-ac-servo-driver-ac-servo-motor-400w-set
>
> to replace my 12Nm steppers - the torque on this motor is 1.27 Nm (they
> rate is as high torque servos) - and is not near 12Nm, that my nema42
> steppers now provide.
> Guess I need gearbox but this would introduce backlash  - or there are some
> brushless servos with around 12Nm torque available?
Peak torque is 3.8 nm.
> Any ideas who can provide 12Nm servos if they exist at all?
>
>
You can look for Fanuc motors. The old 1-0SP is rated at 15 
nm peak. The (alpha)M6/3000 is rated at 6 nm continuous 
stall, so should do 12 nm peak easily. The (alpha)6/2000 and 
(alpha)6/3000 have similar ratings.

And, your NEMA42 steppers may have 12 nm HOLDING TORQUE, but 
they rapidly lost torque as the speed increases. Depending 
on the driver, you may only have 6 nm torque available at 
somewhere between 100 - 300 RPM.

Jon
Jon

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Re: [Emc-users] Emco lathe conversion to servos..

[Les Newell]

Several years ago I modified a Compact5 with a step/dir servo for Z and 
the original stepper for X, running Mach3. I also fitted a different 
motor in the tool changer as the original was painfully slow. There is a 
very poor quality video here 

If I remember correctly I used an IM Service drive for the servo 
. The drive is tiny but works 
quite well.

Les

On 25/01/2017 15:09, sam sokolik wrote:
> I am a control freak - and this helps my affliction...  I don't what to
> assume that the step/dir servo is following the path - I want to know
> for sure.  IIRC atleast the older gecko drives won't error until 128
> encoder counts.   Yikes!  I agree with everything said below...  :)
>
> Also - the buying cheap ebay stuff with generic drives (amc, copley and
> such) makes this hobby pretty inexpensive for the quality system you can
> build.


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Re: [Emc-users] Voltage/Motor RPM Relationship with Brushless Drives

[Nicklas Karlsson]

For permanent magnet motors there is a rather linear correlation between RPM 
and voltage although field weakening might be possible to lower voltage then 
loaded below rated torque.

On Wed, 25 Jan 2017 07:10:05 -0500
"Steve from Tube Gauge"  wrote:

> Hi:
>  
> I have a CNC mill that I am considering replacing the control with LinuxCNC.  
> The motors are the red cap Fanuc units.  I have enquired on this mailing list 
> about using the existing servo amps and motors.  From all the replies and 
> help (thank you very much)  I haved concluded that a good solution for me is 
> to remove the Fanuc encoders and amps  and replace them with suitable units 
> that can communicate on an industry standard format.  To that end I am 
> considering using some AMT31 programmable encoders by CUI (or other encoder 
> suitable for 8 pole motors) and some BE40A8 AMC amps that I have sitting on 
> my shelf. 
>  
> I am aware of the rpm/voltage relationship with brush DC motors.  Generally, 
> as the voltage rises the motor rpm increases a proportional amount.  How does 
> the voltage influence the performance of the brushless motor?  The Fanuc 
> motors are 5S models, 126 V (DC?), 5.8A stall.  The BE40A8 have a maximum 
> running voltage of 80 VDC.  Will running the motors at the lower voltage 
> result in dramatically reduced performance?  Will it cause other electrical 
> problems like an excessive rise in current demand by the motor?
>  
> Thanks for your help - Steve V
> 
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Re: [Emc-users] Emco lathe conversion to servos..

[sam sokolik]

I am a control freak - and this helps my affliction...  I don't what to 
assume that the step/dir servo is following the path - I want to know 
for sure.  IIRC atleast the older gecko drives won't error until 128 
encoder counts.   Yikes!  I agree with everything said below...  :)

Also - the buying cheap ebay stuff with generic drives (amc, copley and 
such) makes this hobby pretty inexpensive for the quality system you can 
build.

On 1/25/2017 6:03 AM, Les Newell wrote:
> Using analog should be more accurate. With step/dir the drive has to
> estimate the commanded speed and position based on the steps. LCNC has
> much more accurate commanded position and velocity figures. It can also
> use tricks like feed forward.
>
> IMHO using step/dir negates some of the advantages of using servos. If
> your machine is moved with the drives off LCNC has no way of detecting
> this. That means you have to home each time you disable the drives. I
> have also found setting up and fault finding step/dir servo systems is
> more difficult than if the loop is in LCNC. For example the scope
> function in LCNC beats every servo drive equivalent I have used. Even a
> little thing like an error message on the screen saying 'Following error
> on X axis' is a lot clearer than a drive flashing 'E42' when you can't
> find the drive manual. Having the loop in LCNC also allows you to do
> tricks like varying the following error limit depending on what you are
> doing. For instance on my lathe I have very tight limits for when the
> machine is stationary but looser limits when it is moving. This allows
> it to detect problems such as a broken encoder cable very quickly. As I
> often use the machine in combined CNC/manual mode (it has two jog wheels
> in place of the traditional hand wheels) I am often working a lot closer
> to the machine than you would in pure CNC mode so it is very important
> to detect a runaway quickly.
>
> Les
>
> On 25/01/2017 11:17, Andrew wrote:
>> Nice! The ferror might be larger when machining, though.
>> Since we're talking about following error, one question has been puzzling
>> me for some time.
>> Say, we have some (pretty advanced) servo drives like Yaskawa or similar,
>> with analog and step/dir input, so we can connect them either way (to 7i76
>> or 7i77). What is the best way to minimise ferror - use LinuxCNC pid with
>> analog control or servo drive's internal pid with step/dir? I guess some
>> cheaper Chinese servos can be tuned better with LinuxCNC, but what about
>> more advanced servo drives like Sigma 5 or 7?
>
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>


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Re: [Emc-users] Voltage/Motor RPM Relationship with Brushless Drives

[dragon]

Steve,

From my, albeit somewhat limited, experience I don't think that you will
be that happy with the performance of running the drives at that
voltage. I have some experience with running brushed motors at just over
half voltage and then later going to full voltage on the same machines.
Running with a maximum of 80v means a 37% drop in voltage. The biggest
place that I think you would see it is in poor acceleration and
deceleration. You would likely be limited to about 1/3 the IPM that you
would running full voltage because you need to have enough reserve to
decelerate without causing a following error. This might be even worse
with a brushless but I just don't have experience with them.

You could certainly try with those amps while you look around for
different ones. You won't hurt the motors.



On 01/25/2017 06:10 AM, Steve from Tube Gauge wrote:
> Hi:
>  
> I have a CNC mill that I am considering replacing the control with LinuxCNC.  
> The motors are the red cap Fanuc units.  I have enquired on this mailing list 
> about using the existing servo amps and motors.  From all the replies and 
> help (thank you very much)  I haved concluded that a good solution for me is 
> to remove the Fanuc encoders and amps  and replace them with suitable units 
> that can communicate on an industry standard format.  To that end I am 
> considering using some AMT31 programmable encoders by CUI (or other encoder 
> suitable for 8 pole motors) and some BE40A8 AMC amps that I have sitting on 
> my shelf. 
>  
> I am aware of the rpm/voltage relationship with brush DC motors.  Generally, 
> as the voltage rises the motor rpm increases a proportional amount.  How does 
> the voltage influence the performance of the brushless motor?  The Fanuc 
> motors are 5S models, 126 V (DC?), 5.8A stall.  The BE40A8 have a maximum 
> running voltage of 80 VDC.  Will running the motors at the lower voltage 
> result in dramatically reduced performance?  Will it cause other electrical 
> problems like an excessive rise in current demand by the motor?
>  
> Thanks for your help - Steve V
> 
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> engaging tech sites, SlashDot.org! http://sdm.link/slashdot
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Re: [Emc-users] Voltage/Motor RPM Relationship with Brushless Drives

[Andrew]

2017-01-25 14:10 GMT+02:00 Steve from Tube Gauge :

> Hi:
>
> I have a CNC mill that I am considering replacing the control with
> LinuxCNC.  The motors are the red cap Fanuc units.  I have enquired on this
> mailing list about using the existing servo amps and motors.  From all the
> replies and help (thank you very much)  I haved concluded that a good
> solution for me is to remove the Fanuc encoders and amps  and replace them
> with suitable units that can communicate on an industry standard format.
> To that end I am considering using some AMT31 programmable encoders by CUI
> (or other encoder suitable for 8 pole motors) and some BE40A8 AMC amps that
> I have sitting on my shelf.
>
> I am aware of the rpm/voltage relationship with brush DC motors.
> Generally, as the voltage rises the motor rpm increases a
> proportional amount.  How does the voltage influence the performance of the
> brushless motor?  The Fanuc motors are 5S models, 126 V (DC?), 5.8A stall.
> The BE40A8 have a maximum running voltage of 80 VDC.  Will running the
> motors at the lower voltage result in dramatically reduced performance?
> Will it cause other electrical problems like an excessive rise in current
> demand by the motor?
>
>
AFAIK motor torque at higher rpm will be seriously decreased at lower
voltage.
I.e. if the nominal is 3000 rpm, you'll have 3000 * 80 / 127 = 1890 rpm max
But probably they require 127V for 4500 rpm, then it's better: 4500 * 80 /
127 = 2830 rpm

Andrew
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[Emc-users] Voltage/Motor RPM Relationship with Brushless Drives

[Steve from Tube Gauge]

Hi:
 
I have a CNC mill that I am considering replacing the control with LinuxCNC.  
The motors are the red cap Fanuc units.  I have enquired on this mailing list 
about using the existing servo amps and motors.  From all the replies and help 
(thank you very much)  I haved concluded that a good solution for me is to 
remove the Fanuc encoders and amps  and replace them with suitable units that 
can communicate on an industry standard format.  To that end I am considering 
using some AMT31 programmable encoders by CUI (or other encoder suitable for 8 
pole motors) and some BE40A8 AMC amps that I have sitting on my shelf. 
 
I am aware of the rpm/voltage relationship with brush DC motors.  Generally, as 
the voltage rises the motor rpm increases a proportional amount.  How does the 
voltage influence the performance of the brushless motor?  The Fanuc motors are 
5S models, 126 V (DC?), 5.8A stall.  The BE40A8 have a maximum running voltage 
of 80 VDC.  Will running the motors at the lower voltage result in dramatically 
reduced performance?  Will it cause other electrical problems like an excessive 
rise in current demand by the motor?
 
Thanks for your help - Steve V

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Re: [Emc-users] Emco lathe conversion to servos..

[Les Newell]

Using analog should be more accurate. With step/dir the drive has to 
estimate the commanded speed and position based on the steps. LCNC has 
much more accurate commanded position and velocity figures. It can also 
use tricks like feed forward.

IMHO using step/dir negates some of the advantages of using servos. If 
your machine is moved with the drives off LCNC has no way of detecting 
this. That means you have to home each time you disable the drives. I 
have also found setting up and fault finding step/dir servo systems is 
more difficult than if the loop is in LCNC. For example the scope 
function in LCNC beats every servo drive equivalent I have used. Even a 
little thing like an error message on the screen saying 'Following error 
on X axis' is a lot clearer than a drive flashing 'E42' when you can't 
find the drive manual. Having the loop in LCNC also allows you to do 
tricks like varying the following error limit depending on what you are 
doing. For instance on my lathe I have very tight limits for when the 
machine is stationary but looser limits when it is moving. This allows 
it to detect problems such as a broken encoder cable very quickly. As I 
often use the machine in combined CNC/manual mode (it has two jog wheels 
in place of the traditional hand wheels) I am often working a lot closer 
to the machine than you would in pure CNC mode so it is very important 
to detect a runaway quickly.

Les

On 25/01/2017 11:17, Andrew wrote:
> Nice! The ferror might be larger when machining, though.
> Since we're talking about following error, one question has been puzzling
> me for some time.
> Say, we have some (pretty advanced) servo drives like Yaskawa or similar,
> with analog and step/dir input, so we can connect them either way (to 7i76
> or 7i77). What is the best way to minimise ferror - use LinuxCNC pid with
> analog control or servo drive's internal pid with step/dir? I guess some
> cheaper Chinese servos can be tuned better with LinuxCNC, but what about
> more advanced servo drives like Sigma 5 or 7?


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Re: [Emc-users] Emco lathe conversion to servos..

[Andrew]

2017-01-25 1:26 GMT+02:00 sam sokolik:

> down to .0001 following error.  Linuxcnc keeps on amazing me...
>

Nice! The ferror might be larger when machining, though.

Since we're talking about following error, one question has been puzzling
me for some time.
Say, we have some (pretty advanced) servo drives like Yaskawa or similar,
with analog and step/dir input, so we can connect them either way (to 7i76
or 7i77). What is the best way to minimise ferror - use LinuxCNC pid with
analog control or servo drive's internal pid with step/dir? I guess some
cheaper Chinese servos can be tuned better with LinuxCNC, but what about
more advanced servo drives like Sigma 5 or 7?

Andrew
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Re: [Emc-users] ECM (Electrochemical Machining)

[Nicklas Karlsson]

H2 sounds interesting, you should it well ventilated or combusted as soon
as possible to avoid an explosion? Or maybe both, open light and good
ventilation? To avoid sparcs is also a solution but it have a catastrophic
failure mode.

It is most often used for circuit boards. But how do they do here, a fluid
jet?

2017-01-25 2:43 GMT+01:00 TJoseph Powderly :

> Hello
> I have not used ecm myself, i use edm a lot.
> I've seen ecm machines working on blisks at factories working for engine
> manufacturers
>
> I know about high current discharges, but ecm is different.
> edm is efficient up to 4"^2 work area at up to 350/400 amperes,
> ecm can handle much larger areas and much larger currents
>
> the gap control strategies are similar from what i've read
>
> theres not a lot of info for DIY
>
> this may be of use (old US gov work at MIT )
> http://www.dtic.mil/dtic/tr/fulltext/u2/659004.pdf
>
> and I'd suggest beginning with a used machine and viewing running machines
> if you can get a scope on one it would be really help your understanding
>
> from academia ( yes you have to sign up but they havent been a spammer
> for me )
> http://www.academia.edu/1407899/Development_of_Electrochemical_
> Micromachining_Table_Top_Machine_Set_Up
> in the paper he does document a small avr based ecm machine (stepper
> driven, 555 pulse timing... ), so
> its not a commercial quality but a good beginner system example
>
> the actual docs and prints or a commercial machine may be very hard to
> get, and very hard to interpret.
> all manufactures directly or indirectly obfuscate the how-to part.
> their intent was never to let you build your own ;-)
>
> a service man from emag could tell you a lot!
> http://www.emag.com/technologies/ecm-electro-chemical-machining.html
>
> regards
> tomp tjtr33
> .
>
>
> a
> On 01/25/17 05:35, Peter Weuta wrote:
> > Dear all,
> >
> > I did follow the interesting discussion about retrofitting EDM machines
> > closely .
> >
> > Is there anybody out there having experience with retrofitting of ECM
> > machines (Electrochemical Maching) ?
> > This processing technology does seem to be alot less common compared to
> > EDM, some basics of the process are mentioned here:
> > https://en.wikipedia.org/wiki/Electrochemical_machining
> > http://electrochemicalmachining.com/technology/process-overview
> >
> > Compared to EDM there are quite some advantages:
> > - very low surface roughness achievable
> > - no recast layer or heat affected zone
> > Therefore a nice technology to process advanced alloys as for example
> > Inconel 718 or alike .
> >
> > We are developing high performance gas turbines. In order to keep BLISK
> > (/Blade on a disc/) manufacturing in house we are planning to acquire
> > and retrofit an ECM machine.
> > My questions:
> > - has this been done by anybody on this list so far ?
> > - any recommondation concerning potential machines to choose from ?
> > (Machines should have an obsolete control system in order to follow the
> > usual justification for conducting a retrofit.)
> > - an alternative might be using an EBM machine as the basis and
> > converting this to ECM. However this would involve quite significant
> > modifications in the field of electrolyte processing, gas cleaning and
> > safety issues (H2 is formed during the process)
> >
> >
> >
> > Thanks alot for your comments in advance + Best Regards,
> > Peter
> >
> > Am 14.01.2017 um 11:58 schrieb Nicklas Karlsson:
> >> It would be good with links like this on the linuxcnc home page and of
> course even better with files themselves if there are no copyright
> restrictions.
> >>
> >> I have attachad a pdf-file which is interesting.
> >>
> >> On Sat, 14 Jan 2017 09:08:03 +0700
> >> TJoseph Powderly  wrote:
> >>
> >>> Nicklas, Sarah and all interested in EDM
> >>> i found this resource
> >>> unlike most tech sites , the papers are free :-)
> >>> http://www.sciencedirect.com/science/journal/22128271/42/supp/C
> >>> regards, tomp tjtr33
> >>>
> >>> btw: lots more than edm here!
> >>>
> >>> 
> --
> >>> Developer Access Program for Intel Xeon Phi Processors
> >>> Access to Intel Xeon Phi processor-based developer platforms.
> >>> With one year of Intel Parallel Studio XE.
> >>> Training and support from Colfax.
> >>> Order your platform today. http://sdm.link/xeonphi
> >>> ___
> >>> Emc-users mailing list
> >>> Emc-users@lists.sourceforge.net
> >>> https://lists.sourceforge.net/lists/listinfo/emc-users
> >>>
> >>>
> >>> 
> --
> >>> Developer Access Program for Intel Xeon Phi Processors
> >>> Access to Intel Xeon Phi processor-based developer platforms.
> >>> With one year of Intel Parallel Studio XE.
> >>> Training and support from Colfax.
> >>> Order your platform today. http://sdm.link/xeonphi
> 

Re: [Emc-users] Leadshine closed loop steppers

[Les Newell]

That isn't a particularly big servo. Much bigger servos are available. 
For example the brushed DC servos on my router are rated at 8.5NM 
continuous at 10A, 50NM peak at 60A (ISTR the drives are limited to 
around 30A). They are 1:1 drive onto 25mm pitch screws. Brushed DC 
servos tend to be lower revving/higher torque than brushless servos. 
They also usually have a higher peak torque. For instance those motors 
you linked have a peak of 3x continuous while my router's servos have a 
peak of 6x continuous. I have worked on machines with servos rated for 
10kW or more (used as lathe spindle drives).

To replace steppers you can usually get away with a servo having a peak 
torque around 3/4 the stepper's holding torque. This is because stepper 
running torque is a lot less than it's holding torque and you can never 
run a stepper near it's maximum torque without risking lost steps. NEMA 
42 steppers generally can't run very fast so doing a 1:1 replacement 
will require an over sized servo for the application, unless you want 
your machine to move much faster. Those servos are rated at 3000rpm. 
Work out how fast your steppers spin at max speed and work out the 
ratio. For example a 3:1 single stage belt reduction would give plenty 
of torque from those motors with a max speed of 1000rpm. Belts have 
negligible backlash and are fine for all but the most precision 
applications. Trapezoidal belts have slightly less backlash than HTD types.

Les

On 25/01/2017 09:07, Klemen Živkovič wrote:
> I just checked:
> http://www.automationtechnologiesinc.com/products-page/ac-servo-motors/the-ac-servo-driver-ac-servo-motor-400w-set
>
> to replace my 12Nm steppers - the torque on this motor is 1.27 Nm (they
> rate is as high torque servos) - and is not near 12Nm, that my nema42
> steppers now provide.
> Guess I need gearbox but this would introduce backlash  - or there are some
> brushless servos with around 12Nm torque available?
>
> Any ideas who can provide 12Nm servos if they exist at all?


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Re: [Emc-users] Leadshine closed loop steppers

[Klemen Živkovič]

I just checked:
http://www.automationtechnologiesinc.com/products-page/ac-servo-motors/the-ac-servo-driver-ac-servo-motor-400w-set

to replace my 12Nm steppers - the torque on this motor is 1.27 Nm (they
rate is as high torque servos) - and is not near 12Nm, that my nema42
steppers now provide.
Guess I need gearbox but this would introduce backlash  - or there are some
brushless servos with around 12Nm torque available?

Any ideas who can provide 12Nm servos if they exist at all?


On Wed, Jan 25, 2017 at 4:31 AM, Jon Elson  wrote:

> On 01/24/2017 03:54 PM, Greg Bernard wrote:
> > Seeing the discussion of servo vs. stepper solutions come up once again
> I wonder if anyone has had experience with these: http://www.
> automationtechnologiesinc.com/products-page/nema34-closed-
> loop-stepper-motor-system-hybrid-servo-kit/nema-34-
> hybrid-servo-motor-kl34-8n-1000-rated-torque-1128-oz-in
> > They are only step/dir but they are being used in both Tormach and
> Shopbot machines which leads me to believe they are a cost-effective
> middle-ground.Any thoughts?
> >
> Well, if you are going to go the whole closed-loop route,
> why do it with a high pole-count stepper motor?
> A 2-phase stepper needs 8 transistors, and you need high
> driving frequencies to spin it fast.  A 3-phase brushless
> motor typically has 4-8 poles, so the frequencies are much
> lower.  (200 full step/rev steppers have 50 poles.)
> And, the 3-phase drive only needs 6 transistors.  The
> stepper motor still has the resonance issue, even though the
> drives are set up to not excite it, the resonance is still
> there.  The lower pole-count brushless motor moves it down
> to a point where it is rarely a problem.
>
> So, I really don't see the advantage to the closed-loop
> stepper. Automation technologies has quite affordable
> brushless servo motors, too.
>
> Jon
>
> 
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