Re: [Emc-users] nema 24 motors.

2017-01-24 Thread Jon Elson 
On 01/24/2017 02:31 PM, Gene Heskett wrote:
> On Tuesday 24 January 2017 12:47:01 Jon Elson wrote:
>   Note that
> stepper motors are rated on holding torque, and they will
> not even produce that much when running at low speeds.
> Servos draw no current at no load, and can stay cool so they
> have a reserve or peak torque available.  The torque peak
> can often be 4 - 6 X the continuous rated torque.  So, a
> motor rated at 100 Oz-In continuous could easily deliver 400
> Oz-In peak for a few seconds.
>
> Jon
> Thats a consideration I hadn't plugged into my train of thought Jon,
> thanks.
>
>
But, this is one of the most IMPORTANT features of servo 
motor systems!

Jon

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Re: [Emc-users] nema 24 motors.

2017-01-24 Thread Jon Elson 
On 01/24/2017 02:23 PM, Gene Heskett wrote:
>
> Thats the first time in a decade or more that anybody ever talked about
> how that works, thanks.
>
> In the advertising, it reads like salesman-speak. And I always take 2
> steps back when I read that language.  Part of my personal spam filter I
> guess. :)  That and a wee bit of Missouri in my DNA. :)
>
>
Well, the first time I converted my minimill, I put some old 
NEMA 34 steppers on it and was able to get 90 IPM with the 
motors spinning at 1440 RPM.  It was quite impressive.  That 
was with the original Gecko 201.  I'd never seen a stepper 
move like THAT!  But, I don't like the idea of flying blind, 
so I did it over with servos.

Jon

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Re: [Emc-users] nema 24 motors.

2017-01-24 Thread Jon Elson 
On 01/24/2017 01:04 PM, Gene Heskett wrote:
> On Tuesday 24 January 2017 09:49:12 Ed wrote:
>
>>
>> RANT MODE ON
>>
>> Why in this day of cheap encoders, small ebay servo motors, and good
>> inexpensive servo drives does any one even use stepper motors?
>>
>> Dampers, resonance issues, lost steps, stalls, only 30 IPM? Why?
>>
>> Gene, don't stay on the dark side! Go to servo's and don't look back,
>> you will never regret it.
>>
>> RANT MODE OFF
>>
> Because the stepper motor at up to 470 oz/in can be had for under a $40
> bill, and a suitable driver for the mid $30's (nema 23), or mid $60's
> for a nema 34 if you don't need 3k revs and a suitable psu for less than
> $40 for either, less than $150 an axis worst case.
Yes, and now you've proven they DON'T work, and you are 
having to come up with all sorts of Rube Goldberg hacks to 
try to make it work for you.
> The only servo drive I am familiar with is $120, and motors with encoders
> are around $250 and up to $2500 on ebay right now (and obviously too
> long as I only have about 118 mm for the x motors depth) , and the
> interfaces giving the analog voltages the servo driver's need are about
> $20 an axis more? Although the vfd I find is happier that that famous
> hog being fed by a pdm signal at a 10 khz pulse rate)
Automation technologies Inc (formerly Kelinginc) has some 
VERY affordable brush and brushless motors.
I've used their brushless motors with my servo amps and they 
work quite well.
> So here's a challenge Ed, find me a 2 axis kit that can move this 11x36
> with as much torque at working speeds as these steppers can make, for a
> $300 bill,
Well, you can keep picking up items on eBay and trying to 
get lucky, but you may end up with a lot more of the same 
trouble.

Jon

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Re: [Emc-users] nema 24 motors.

2017-01-24 Thread N. Christopher Perry 
I saw a similar idea for a damper years ago, except a square section copper 
ring was used in leu of the balls.

N. Christopher Perry

> On Jan 24, 2017, at 12:45 AM, Gene Heskett  wrote:
> 
> Greetings all;
> 
> I see some "Nema 24" motors at quite reasonable prices showing up on 
> fleabay, in fairly high torque ratings, so I bought one 10 days back, 
> since I need a stronger one, with perhaps a damper on it on my x axis. I 
> bought the 8 wire model so I can drive it in parallel where I ought to 
> be able to get 3k rpms out of it. The mount bolt pattern appears to be a 
> duplicated of nema 23, but the body is just a wee bit fatter, the shaft 
> is double ended 8mm, and the whole thing looks like it will fit behind 
> the new apron with about 5mm of clearance between the back shaft end and 
> the face of the bed.  So its perhaps 5mm longer than the double ended 
> nema 23 rated at 235 oz/in in there now.
> 
> So I need to locate a 20 tooth, 8m bore pulley before I make the swap.
> 
> Now, I don't believe this is going to help with the resonance stalls I am 
> getting at about 30 ipm, so I'm thinking of building a viscous damper to 
> fit on the rear of this puppy.  But unlike the ones on my hf micromill, 
> which are long steel spools carrying a 2+ inch stack of heavy fender 
> washers with elastomer sheets between the washers, which are true shock 
> absorbers as the resonance is killed by the frictional losses as the 
> washers walk on the talcum covered elastomer, but I don't have room for 
> a 2+" stack of fender washers in this spot. 5/8" axially at best.
> 
> I do have room for a larger diameter assembly on the back, so I am 
> thinking in terms of a 1/2" thick by maybe 4" in diameter alu wheel, 
> drilling in from the side at a low angle to put a couple set screws in 
> to clamp it to the motor shaft, and knock down 1 or 2 of my 00 buck 12 
> gauge rounds, measure them, and bore as many pockets in the rim as I can 
> fit leaving about 20 to 30 thou for the balls to move within the pockets 
> filled with grease, and sealed over. A thin gasket to contain the 
> grease, and a 1/8" thick cap ring with a pair of 0-80 cap screws into 
> the fillets between the pockets should make a good torsional vibration 
> damper.  Or plow a groove for a 1/16" o-ring on the outside of the cap, 
> and the inside radius of the cap ring on one side of it. Useing the 
> o-rings would tend to make the grease self distributing, and the small 
> clearance might even aid in the damping if I intentionally plow a 
> shallow 3rd groove between the grooves for the sealing o-rings would 
> further enhance the viscous losses of the grease moving back and forth 
> between pockets thru that narrow passage.
> 
> What do the vibration engineers in this crowd think of this idea?
> 
> 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)
> Genes Web page 
> 
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Re: [Emc-users] nema 24 motors.

2017-01-24 Thread Gene Heskett 
On Tuesday 24 January 2017 12:47:01 Jon Elson wrote:

> On 01/24/2017 10:03 AM, dan...@austin.rr.com wrote:
> > Don't servos need a lot of reduction to get the torque up? 
> > Gearboxes always bring backlash into the system.  Low backlash boxes
> > are lots of $$$.
>
> Toothed belt drives don't add backlash, until the belts are
> badly worn.  (On a hobby system, you will NEVER wear them
> out.)  No, you don't need much reduction, and with a
> suitably-sized motor, no reduction is needed.  Note that
> stepper motors are rated on holding torque, and they will
> not even produce that much when running at low speeds.
> Servos draw no current at no load, and can stay cool so they
> have a reserve or peak torque available.  The torque peak
> can often be 4 - 6 X the continuous rated torque.  So, a
> motor rated at 100 Oz-In continuous could easily deliver 400
> Oz-In peak for a few seconds.
>
> Jon

Thats a consideration I hadn't plugged into my train of thought Jon, 
thanks.

Cheers, Gene Heskett
-- 
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 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page 

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Re: [Emc-users] nema 24 motors.

2017-01-24 Thread Gene Heskett 
On Tuesday 24 January 2017 12:37:19 Jon Elson wrote:

> On 01/23/2017 11:45 PM, Gene Heskett wrote:
> > Greetings all;
> >
> > I see some "Nema 24" motors at quite reasonable prices showing up on
> > fleabay, in fairly high torque ratings, so I bought one 10 days
> > back, since I need a stronger one, with perhaps a damper on it on my
> > x axis. I bought the 8 wire model so I can drive it in parallel
> > where I ought to be able to get 3k rpms out of it.
>
> 3K RPM from a stepper?  Why are you doing this?  That sounds
> like servo territory.
>
> > What do the vibration engineers in this crowd think of this idea?
>
> Your damper pretty much has to work. 

Thanks, given time & raw materials, I'll probably make it.
[...]
Thanks Jon. I, like everybody else here, appreciate a vote of confidence 
now & then.

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)
Genes Web page 

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Re: [Emc-users] nema 24 motors.

2017-01-24 Thread Gene Heskett 
On Tuesday 24 January 2017 12:37:19 Jon Elson wrote:

> On 01/23/2017 11:45 PM, Gene Heskett wrote:
> > Greetings all;
> >
> > I see some "Nema 24" motors at quite reasonable prices showing up on
> > fleabay, in fairly high torque ratings, so I bought one 10 days
> > back, since I need a stronger one, with perhaps a damper on it on my
> > x axis. I bought the 8 wire model so I can drive it in parallel
> > where I ought to be able to get 3k rpms out of it.
>
> 3K RPM from a stepper?  Why are you doing this?  That sounds
> like servo territory.
>
> > What do the vibration engineers in this crowd think of this idea?
>
> Your damper pretty much has to work.  Some steppers don't
> need very much damping at all to kill the resonance.
> Or, a properly adjusted Gecko 201 driver will pretty much
> get rid of all resonance issues.  They have a pot you tune
> for minimum hum at a certain speed, and it compensates out
> the residual excitation of the resonance.
>
> Jon

Thats the first time in a decade or more that anybody ever talked about 
how that works, thanks.

In the advertising, it reads like salesman-speak. And I always take 2 
steps back when I read that language.  Part of my personal spam filter I 
guess. :)  That and a wee bit of Missouri in my DNA. :) 

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)
Genes Web page 

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Re: [Emc-users] nema 24 motors.

2017-01-24 Thread Gene Heskett 
On Tuesday 24 January 2017 11:03:49 andy pugh wrote:

> On 24 January 2017 at 15:51, dragon  wrote:
> > After having worked with both, I knew that I wouldn't be happy with
> > a stepper system even for my little home machines.
>
> Do you think my Z-servo is big enough?
> https://goo.gl/photos/TkxsaDgcPFoBqpXV9
>
> (Bought because it was cheap, £50 from eBay. 1kW and with Resolver
> feedback)

That sounds like a good price, but the pix is too dark to see it well in 
that shot. But I do see that you were even more cramped for x motor 
space behind the apron than I am. When I made the new apron face, I 
mounted it to the front face of the saddle, gaining about an inch there 
because the apron is 1/2" thick. Then I made some steel runners to let 
an 1/8" alu sled on the front face of the apron move to tension the belt 
by sliding the motor up and down. So I have nominally room for a motor 
up to 119 mm's long

I need to take some pix I guess.

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)
Genes Web page 

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Re: [Emc-users] nema 24 motors.

2017-01-24 Thread Gene Heskett 
On Tuesday 24 January 2017 10:48:46 Todd Zuercher wrote:

> - Original Message -
>
> > From: "Ed" 
> > To: emc-users@lists.sourceforge.net
> > Sent: Tuesday, January 24, 2017 9:49:12 AM
> > Subject: Re: [Emc-users] nema 24 motors.
> >
> > On 01/23/2017 11:45 PM, Gene Heskett wrote:
> > > Greetings all;
> > >
> > > I see some "Nema 24" motors at quite reasonable prices showing up
> > > on
> > > fleabay,
> >
> > SNIP
> >
> > > Now, I don't believe this is going to help with the resonance
> > > stalls I am
> > > getting at about 30 ipm, so I'm thinking of building a viscous
> > > damper to
> > > fit on the rear of this puppy.  But unlike the ones on my hf
> > > micromill,
> > > which are long steel spools carrying a 2+ inch stack of heavy
> > > fender
> > > washers with elastomer sheets between the washers, which are true
> > > shock
> > > absorbers as the resonance is killed by the frictional losses as
> > > the
> > > washers walk on the talcum covered elastomer, but I don't have
> > > room for
> > > a 2+" stack of fender washers in this spot. 5/8" axially at best.
> >
> > SNIP
> >
> > > Cheers, Gene Heskett
> >
> > RANT MODE ON
> >
> > Why in this day of cheap encoders, small ebay servo motors, and good
> > inexpensive servo drives does any one even use stepper motors?
> >
> > Dampers, resonance issues, lost steps, stalls, only 30 IPM? Why?
> >
> > Gene, don't stay on the dark side! Go to servo's and don't look
> > back, you will never regret it.
> >
> > RANT MODE OFF
> >
> > deflates-
> >
> > Ed.
>
> That's easy to answer, because Gene doesn't like to do things the easy
> way, if he isn't cutting corners and scrambling like mad to make
> things work he isn't happy. If he had bought every thing and all it
> went together and all worked right the first time, he'd probably have
> to sell it all and start over.
>

Now now Todd, be nice, its not quite that bad. :) I'm practical in that 
it would only be sold if there was enough profit to build another just 
like it for less, kay? ;-)

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)
Genes Web page <http://geneslinuxbox.net:6309/gene>

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Re: [Emc-users] nema 24 motors.

2017-01-24 Thread Gene Heskett 
On Tuesday 24 January 2017 09:49:12 Ed wrote:

> On 01/23/2017 11:45 PM, Gene Heskett wrote:
> > Greetings all;
> >
> > I see some "Nema 24" motors at quite reasonable prices showing up on
> > fleabay,
>
> SNIP
>
> > Now, I don't believe this is going to help with the resonance stalls
> > I am getting at about 30 ipm, so I'm thinking of building a viscous
> > damper to fit on the rear of this puppy.  But unlike the ones on my
> > hf micromill, which are long steel spools carrying a 2+ inch stack
> > of heavy fender washers with elastomer sheets between the washers,
> > which are true shock absorbers as the resonance is killed by the
> > frictional losses as the washers walk on the talcum covered
> > elastomer, but I don't have room for a 2+" stack of fender washers
> > in this spot. 5/8" axially at best.
>
> SNIP
>
> > Cheers, Gene Heskett
>
> RANT MODE ON
>
> Why in this day of cheap encoders, small ebay servo motors, and good
> inexpensive servo drives does any one even use stepper motors?
>
> Dampers, resonance issues, lost steps, stalls, only 30 IPM? Why?
>
> Gene, don't stay on the dark side! Go to servo's and don't look back,
> you will never regret it.
>
> RANT MODE OFF
>
> deflates-
>
> Ed.
Because the stepper motor at up to 470 oz/in can be had for under a $40 
bill, and a suitable driver for the mid $30's (nema 23), or mid $60's 
for a nema 34 if you don't need 3k revs and a suitable psu for less than 
$40 for either, less than $150 an axis worst case.

The only servo drive I am familiar with is $120, and motors with encoders 
are around $250 and up to $2500 on ebay right now (and obviously too 
long as I only have about 118 mm for the x motors depth) , and the 
interfaces giving the analog voltages the servo driver's need are about 
$20 an axis more? Although the vfd I find is happier that that famous 
hog being fed by a pdm signal at a 10 khz pulse rate)

So here's a challenge Ed, find me a 2 axis kit that can move this 11x36 
with as much torque at working speeds as these steppers can make, for a 
$300 bill, thats w/o the interface card as the pi doesn't have a 
parport, so I'm stuck either reverting to 1 or more 5i25's in an old 
Dell, or making the pi work. But this spi bus's noise sensitivity is 
killing me. There seems to be NO EXPOSED PLACE on eithers pcb where I 
could tie them together with a 2" piece of 5/16" wide braid using 3% 
silver eutectic solder, so they truly had a common ground. I may yet 
sacrifice a usb port on the pi (the guts look like plastic that would 
melt and be destroyed), and make up a 10 pair header with the top 
trimmed back enough to expose the tops of 10 female crimp terminals, so 
I can make a ground, a REAL ground, between the pi and the 7i90.

If price really was no object, sure, but this is the real world, and I'm 
on SS since mid 2002.  This is a hobby project to keep me out of the 
bars. I rest my case.

There is point triple ought zero chance of this thing ever paying for 
itself in my remaining time. I am 82, a type 2 diabetic, and 2 collapsed 
disks in my back they refuse to consider doing any more for than write 
painkiller scripts for.  And the only one that helps is about to become 
a scheduled narcotic in WV. It seems the overdose cadavers are testing 
positive for it.

>
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Cheers, Gene Heskett
-- 
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 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page 

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Re: [Emc-users] nema 24 motors.

2017-01-24 Thread Jon Elson 
On 01/24/2017 10:03 AM, dan...@austin.rr.com wrote:
> Don't servos need a lot of reduction to get the torque up?  Gearboxes always 
> bring backlash into the system.  Low backlash boxes are lots of $$$.
>
Toothed belt drives don't add backlash, until the belts are 
badly worn.  (On a hobby system, you will NEVER wear them 
out.)  No, you don't need much reduction, and with a 
suitably-sized motor, no reduction is needed.  Note that 
stepper motors are rated on holding torque, and they will 
not even produce that much when running at low speeds.  
Servos draw no current at no load, and can stay cool so they 
have a reserve or peak torque available.  The torque peak 
can often be 4 - 6 X the continuous rated torque.  So, a 
motor rated at 100 Oz-In continuous could easily deliver 400 
Oz-In peak for a few seconds.

Jon

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Re: [Emc-users] nema 24 motors.

2017-01-24 Thread Jon Elson 
On 01/23/2017 11:45 PM, Gene Heskett wrote:
> Greetings all;
>
> I see some "Nema 24" motors at quite reasonable prices showing up on
> fleabay, in fairly high torque ratings, so I bought one 10 days back,
> since I need a stronger one, with perhaps a damper on it on my x axis. I
> bought the 8 wire model so I can drive it in parallel where I ought to
> be able to get 3k rpms out of it.
3K RPM from a stepper?  Why are you doing this?  That sounds 
like servo territory.
> What do the vibration engineers in this crowd think of this idea?
>
>
Your damper pretty much has to work.  Some steppers don't 
need very much damping at all to kill the resonance.
Or, a properly adjusted Gecko 201 driver will pretty much 
get rid of all resonance issues.  They have a pot you tune 
for minimum hum at a certain speed, and it compensates out 
the residual excitation of the resonance.

Jon

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Re: [Emc-users] nema 24 motors.

2017-01-24 Thread andy pugh 
On 24 January 2017 at 16:19, dragon  wrote:
> Is your Z ballscrew floating on the far end?

It was at that point of the construction, it isn't now:
https://goo.gl/photos/jaYvGDbYH51oLJS28


-- 
atp
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designed for the especial use of mechanical geniuses, daredevils and
lunatics."
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Re: [Emc-users] nema 24 motors.

2017-01-24 Thread dragon 
Andy... you must need a lot of reduction for that one :P Is your Z
ballscrew floating on the far end?

Danny... usually you see a toothed (timing) belt as they have no
backlash and are inexpensive. Then you can set whatever reduction you
need by changing the ratios. If the servos are big enough or the load
small enough they can be direct drive depending on your system voltage.


On 01/24/2017 10:03 AM, dan...@austin.rr.com wrote:
> Don't servos need a lot of reduction to get the torque up?  Gearboxes always 
> bring backlash into the system.  Low backlash boxes are lots of $$$.
> 
> 
> 
> Danny
> 
>  dragon  wrote: 
>> I hate to say it but I'm with Ed on this one. I just paid $32 each for
>> e661 servos WITH encoders to put on my 10x24 lathe and Jet 626 mill.
>> Grab a free thrown out PC and get rid of the noise problems from that
>> SPI bus on the rPi. Analog input drives can be had on ebay for $35,
>> especially if you run under 80vDC. With my 96v supply I hope to be up
>> around 150ipm.
>>
>> While 3 phase steppers are MUCH better than two phase for all of the
>> reasons that Danny listed, you can spend the same amount or less for a
>> servo setup if you don't mind some used components.
>>
>> After having worked with both, I knew that I wouldn't be happy with a
>> stepper system even for my little home machines.
>>
>> Just my opinion...
>>
>> On 01/24/2017 08:49 AM, Ed wrote:
>>> On 01/23/2017 11:45 PM, Gene Heskett wrote:
 Greetings all;

 I see some "Nema 24" motors at quite reasonable prices showing up on
 fleabay,
>>>
>>> SNIP
 Now, I don't believe this is going to help with the resonance stalls I am
 getting at about 30 ipm, so I'm thinking of building a viscous damper to
 fit on the rear of this puppy.  But unlike the ones on my hf micromill,
 which are long steel spools carrying a 2+ inch stack of heavy fender
 washers with elastomer sheets between the washers, which are true shock
 absorbers as the resonance is killed by the frictional losses as the
 washers walk on the talcum covered elastomer, but I don't have room for
 a 2+" stack of fender washers in this spot. 5/8" axially at best.
>>>
>>> SNIP
 Cheers, Gene Heskett
>>>
>>>
>>> RANT MODE ON
>>>
>>> Why in this day of cheap encoders, small ebay servo motors, and good 
>>> inexpensive servo drives does any one even use stepper motors?
>>>
>>> Dampers, resonance issues, lost steps, stalls, only 30 IPM? Why?
>>>
>>> Gene, don't stay on the dark side! Go to servo's and don't look back, 
>>> you will never regret it.
>>>
>>> RANT MODE OFF
>>>
>>> deflates-
>>>
>>> Ed.
>>>
>>>
>>> --
>>> Check out the vibrant tech community on one of the world's most
>>> engaging tech sites, SlashDot.org! http://sdm.link/slashdot
>>> ___
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>>>
>>
> 
> 
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Re: [Emc-users] nema 24 motors.

2017-01-24 Thread andy pugh 
On 24 January 2017 at 16:03,   wrote:
> Don't servos need a lot of reduction to get the torque up?

Not always. It depends on leadscrew lead and servo size,

> Gearboxes always bring backlash into the system.  Low backlash boxes are lots 
> of $$$.

But backlash-free timing belts exist, and are very inexpensive.
Or, you can (apparently) use inverted-tooth chains (experiment
ongoing, but looking good so far)


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Re: [Emc-users] nema 24 motors.

2017-01-24 Thread John Thornton 
The servos on my BP knee mill with an Anilam 1100M conversion have 
timing belt reduction to the ball screw... and so does my CHNC.

JT


On 1/24/2017 10:03 AM, dan...@austin.rr.com wrote:
> Don't servos need a lot of reduction to get the torque up?  Gearboxes always 
> bring backlash into the system.  Low backlash boxes are lots of $$$.
>
>
>
> Danny
>
>  dragon  wrote:
>> I hate to say it but I'm with Ed on this one. I just paid $32 each for
>> e661 servos WITH encoders to put on my 10x24 lathe and Jet 626 mill.
>> Grab a free thrown out PC and get rid of the noise problems from that
>> SPI bus on the rPi. Analog input drives can be had on ebay for $35,
>> especially if you run under 80vDC. With my 96v supply I hope to be up
>> around 150ipm.
>>
>> While 3 phase steppers are MUCH better than two phase for all of the
>> reasons that Danny listed, you can spend the same amount or less for a
>> servo setup if you don't mind some used components.
>>
>> After having worked with both, I knew that I wouldn't be happy with a
>> stepper system even for my little home machines.
>>
>> Just my opinion...
>>
>> On 01/24/2017 08:49 AM, Ed wrote:
>>> On 01/23/2017 11:45 PM, Gene Heskett wrote:
 Greetings all;

 I see some "Nema 24" motors at quite reasonable prices showing up on
 fleabay,
>>> SNIP
 Now, I don't believe this is going to help with the resonance stalls I am
 getting at about 30 ipm, so I'm thinking of building a viscous damper to
 fit on the rear of this puppy.  But unlike the ones on my hf micromill,
 which are long steel spools carrying a 2+ inch stack of heavy fender
 washers with elastomer sheets between the washers, which are true shock
 absorbers as the resonance is killed by the frictional losses as the
 washers walk on the talcum covered elastomer, but I don't have room for
 a 2+" stack of fender washers in this spot. 5/8" axially at best.
>>> SNIP
 Cheers, Gene Heskett
>>>
>>> RANT MODE ON
>>>
>>> Why in this day of cheap encoders, small ebay servo motors, and good
>>> inexpensive servo drives does any one even use stepper motors?
>>>
>>> Dampers, resonance issues, lost steps, stalls, only 30 IPM? Why?
>>>
>>> Gene, don't stay on the dark side! Go to servo's and don't look back,
>>> you will never regret it.
>>>
>>> RANT MODE OFF
>>>
>>> deflates-
>>>
>>> Ed.
>>>
>>>
>>> --
>>> Check out the vibrant tech community on one of the world's most
>>> engaging tech sites, SlashDot.org! http://sdm.link/slashdot
>>> ___
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>>> https://lists.sourceforge.net/lists/listinfo/emc-users
>>>
>
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Re: [Emc-users] nema 24 motors.

2017-01-24 Thread dannym 
Don't servos need a lot of reduction to get the torque up?  Gearboxes always 
bring backlash into the system.  Low backlash boxes are lots of $$$.



Danny

 dragon  wrote: 
> I hate to say it but I'm with Ed on this one. I just paid $32 each for
> e661 servos WITH encoders to put on my 10x24 lathe and Jet 626 mill.
> Grab a free thrown out PC and get rid of the noise problems from that
> SPI bus on the rPi. Analog input drives can be had on ebay for $35,
> especially if you run under 80vDC. With my 96v supply I hope to be up
> around 150ipm.
> 
> While 3 phase steppers are MUCH better than two phase for all of the
> reasons that Danny listed, you can spend the same amount or less for a
> servo setup if you don't mind some used components.
> 
> After having worked with both, I knew that I wouldn't be happy with a
> stepper system even for my little home machines.
> 
> Just my opinion...
> 
> On 01/24/2017 08:49 AM, Ed wrote:
> > On 01/23/2017 11:45 PM, Gene Heskett wrote:
> >> Greetings all;
> >>
> >> I see some "Nema 24" motors at quite reasonable prices showing up on
> >> fleabay,
> > 
> > SNIP
> >> Now, I don't believe this is going to help with the resonance stalls I am
> >> getting at about 30 ipm, so I'm thinking of building a viscous damper to
> >> fit on the rear of this puppy.  But unlike the ones on my hf micromill,
> >> which are long steel spools carrying a 2+ inch stack of heavy fender
> >> washers with elastomer sheets between the washers, which are true shock
> >> absorbers as the resonance is killed by the frictional losses as the
> >> washers walk on the talcum covered elastomer, but I don't have room for
> >> a 2+" stack of fender washers in this spot. 5/8" axially at best.
> > 
> > SNIP
> >> Cheers, Gene Heskett
> > 
> > 
> > RANT MODE ON
> > 
> > Why in this day of cheap encoders, small ebay servo motors, and good 
> > inexpensive servo drives does any one even use stepper motors?
> > 
> > Dampers, resonance issues, lost steps, stalls, only 30 IPM? Why?
> > 
> > Gene, don't stay on the dark side! Go to servo's and don't look back, 
> > you will never regret it.
> > 
> > RANT MODE OFF
> > 
> > deflates-
> > 
> > Ed.
> > 
> > 
> > --
> > Check out the vibrant tech community on one of the world's most
> > engaging tech sites, SlashDot.org! http://sdm.link/slashdot
> > ___
> > Emc-users mailing list
> > Emc-users@lists.sourceforge.net
> > https://lists.sourceforge.net/lists/listinfo/emc-users
> > 
> 


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Re: [Emc-users] nema 24 motors.

2017-01-24 Thread andy pugh 
On 24 January 2017 at 15:51, dragon  wrote:
> After having worked with both, I knew that I wouldn't be happy with a
> stepper system even for my little home machines.

Do you think my Z-servo is big enough?
https://goo.gl/photos/TkxsaDgcPFoBqpXV9

(Bought because it was cheap, £50 from eBay. 1kW and with Resolver feedback)

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Re: [Emc-users] nema 24 motors.

2017-01-24 Thread dragon 
I hate to say it but I'm with Ed on this one. I just paid $32 each for
e661 servos WITH encoders to put on my 10x24 lathe and Jet 626 mill.
Grab a free thrown out PC and get rid of the noise problems from that
SPI bus on the rPi. Analog input drives can be had on ebay for $35,
especially if you run under 80vDC. With my 96v supply I hope to be up
around 150ipm.

While 3 phase steppers are MUCH better than two phase for all of the
reasons that Danny listed, you can spend the same amount or less for a
servo setup if you don't mind some used components.

After having worked with both, I knew that I wouldn't be happy with a
stepper system even for my little home machines.

Just my opinion...

On 01/24/2017 08:49 AM, Ed wrote:
> On 01/23/2017 11:45 PM, Gene Heskett wrote:
>> Greetings all;
>>
>> I see some "Nema 24" motors at quite reasonable prices showing up on
>> fleabay,
> 
> SNIP
>> Now, I don't believe this is going to help with the resonance stalls I am
>> getting at about 30 ipm, so I'm thinking of building a viscous damper to
>> fit on the rear of this puppy.  But unlike the ones on my hf micromill,
>> which are long steel spools carrying a 2+ inch stack of heavy fender
>> washers with elastomer sheets between the washers, which are true shock
>> absorbers as the resonance is killed by the frictional losses as the
>> washers walk on the talcum covered elastomer, but I don't have room for
>> a 2+" stack of fender washers in this spot. 5/8" axially at best.
> 
> SNIP
>> Cheers, Gene Heskett
> 
> 
> RANT MODE ON
> 
> Why in this day of cheap encoders, small ebay servo motors, and good 
> inexpensive servo drives does any one even use stepper motors?
> 
> Dampers, resonance issues, lost steps, stalls, only 30 IPM? Why?
> 
> Gene, don't stay on the dark side! Go to servo's and don't look back, 
> you will never regret it.
> 
> RANT MODE OFF
> 
> deflates-
> 
> Ed.
> 
> 
> --
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> engaging tech sites, SlashDot.org! http://sdm.link/slashdot
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> 



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Re: [Emc-users] nema 24 motors.

2017-01-24 Thread hubert 
I see all the concern about resonance stalls with steppers.  When I 
switched to Gecko 250 drivers I stopped having these problems. I see 60 
ipm with no problems on direct drive and 5 tpi ball screws.  They were a 
little more expensive but a lot less trouble.  I can't remember the 
stated solution for the resonance solution but in my experience it works.

Hubert


On 1/24/17 8:49 AM, Ed wrote:
> On 01/23/2017 11:45 PM, Gene Heskett wrote:
>> Greetings all;
>>
>> I see some "Nema 24" motors at quite reasonable prices showing up on
>> fleabay,
> SNIP
>> Now, I don't believe this is going to help with the resonance stalls I am
>> getting at about 30 ipm, so I'm thinking of building a viscous damper to
>> fit on the rear of this puppy.  But unlike the ones on my hf micromill,
>> which are long steel spools carrying a 2+ inch stack of heavy fender
>> washers with elastomer sheets between the washers, which are true shock
>> absorbers as the resonance is killed by the frictional losses as the
>> washers walk on the talcum covered elastomer, but I don't have room for
>> a 2+" stack of fender washers in this spot. 5/8" axially at best.
> SNIP
>> Cheers, Gene Heskett
>
> RANT MODE ON
>
> Why in this day of cheap encoders, small ebay servo motors, and good
> inexpensive servo drives does any one even use stepper motors?
>
> Dampers, resonance issues, lost steps, stalls, only 30 IPM? Why?
>
> Gene, don't stay on the dark side! Go to servo's and don't look back,
> you will never regret it.
>
> RANT MODE OFF
>
> deflates-
>
> Ed.
>
>
> --
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> engaging tech sites, SlashDot.org! http://sdm.link/slashdot
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> https://lists.sourceforge.net/lists/listinfo/emc-users
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Re: [Emc-users] nema 24 motors.

2017-01-24 Thread Todd Zuercher 

- Original Message -
> From: "Ed" 
> To: emc-users@lists.sourceforge.net
> Sent: Tuesday, January 24, 2017 9:49:12 AM
> Subject: Re: [Emc-users] nema 24 motors.
> 
> On 01/23/2017 11:45 PM, Gene Heskett wrote:
> > Greetings all;
> >
> > I see some "Nema 24" motors at quite reasonable prices showing up
> > on
> > fleabay,
> 
> SNIP
> > Now, I don't believe this is going to help with the resonance
> > stalls I am
> > getting at about 30 ipm, so I'm thinking of building a viscous
> > damper to
> > fit on the rear of this puppy.  But unlike the ones on my hf
> > micromill,
> > which are long steel spools carrying a 2+ inch stack of heavy
> > fender
> > washers with elastomer sheets between the washers, which are true
> > shock
> > absorbers as the resonance is killed by the frictional losses as
> > the
> > washers walk on the talcum covered elastomer, but I don't have room
> > for
> > a 2+" stack of fender washers in this spot. 5/8" axially at best.
> 
> SNIP
> > Cheers, Gene Heskett
> 
> 
> RANT MODE ON
> 
> Why in this day of cheap encoders, small ebay servo motors, and good
> inexpensive servo drives does any one even use stepper motors?
> 
> Dampers, resonance issues, lost steps, stalls, only 30 IPM? Why?
> 
> Gene, don't stay on the dark side! Go to servo's and don't look back,
> you will never regret it.
> 
> RANT MODE OFF
> 
> deflates-
> 
> Ed.
> 

That's easy to answer, because Gene doesn't like to do things the easy way, 
if he isn't cutting corners and scrambling like mad to make things work he 
isn't happy.
If he had bought every thing and all it went together and all worked right the 
first time, 
he'd probably have to sell it all and start over.

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Re: [Emc-users] nema 24 motors.

2017-01-24 Thread Ed 
On 01/23/2017 11:45 PM, Gene Heskett wrote:
> Greetings all;
>
> I see some "Nema 24" motors at quite reasonable prices showing up on
> fleabay,

SNIP
> Now, I don't believe this is going to help with the resonance stalls I am
> getting at about 30 ipm, so I'm thinking of building a viscous damper to
> fit on the rear of this puppy.  But unlike the ones on my hf micromill,
> which are long steel spools carrying a 2+ inch stack of heavy fender
> washers with elastomer sheets between the washers, which are true shock
> absorbers as the resonance is killed by the frictional losses as the
> washers walk on the talcum covered elastomer, but I don't have room for
> a 2+" stack of fender washers in this spot. 5/8" axially at best.

SNIP
> Cheers, Gene Heskett


RANT MODE ON

Why in this day of cheap encoders, small ebay servo motors, and good 
inexpensive servo drives does any one even use stepper motors?

Dampers, resonance issues, lost steps, stalls, only 30 IPM? Why?

Gene, don't stay on the dark side! Go to servo's and don't look back, 
you will never regret it.

RANT MODE OFF

deflates-

Ed.


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Re: [Emc-users] nema 24 motors.

2017-01-24 Thread Gene Heskett 
On Tuesday 24 January 2017 02:10:53 Danny Miller wrote:

> What drive and system voltage are you using here?

An M542T for x drive, and a DM860 for Z drive, with an 8 wire 230 oz 
motor for x, 20 tooth pulley to 40 tooth on the x drive, which is a 
probably too small ball screw. Z drive is a nema 34, 1600 oz, 30 teeth 
on the motor, 40 one the end of a 1450mm x 25mm ball screw, moves the 
carriage at nearly 80 ipm. 46 volts powers the M542T, and about 68 volts 
powers the DM860.

> Toroids don't make any sense anymore.  Switching power supplies DO
> perform great, unless you  overload 'em with BEMF, but a toroid is
> vulnerable to that too.  Specifically Meanwell switching supplies
> perform reliably.

I have a stack of 4 of them currently sitting on my chopsaw

The spi bus is extremely susceptable to noise pickup. The switching 
noises from the supplies I bought could not be tolerated. I didn't use 
the little pcb from OHSPARK because its only traces were the ones for 
the source termed connections. No ground continuity at all in the .brd 
images I downloaded and printed letter sized images of that I used to 
count pin numbers when I made this spi cable.. So I cut a 40 pin drive 
cable off the end of an old ide drive cable, leaveing about 3/4", 
terminated that into about an inch wide pcd cut from a rat shack project 
board, putting the term R's needed, 3 of them, on this board and 
connected all the ground pins of the 40 pin side to the grounds on the  
26 pin side going to the 7i90, and because of all the other cables that 
connect to the pi, this plugs into the pi, and this little pcb comes 
across the top of it, and runs down across the top of the pi to 7i90 
until its folded at a 45 degree angle and points at the 26 pin plug 
about an inch away, a 26 pin plug then folds the cable down about 3/8" 
and plugs into the 7i90. Because this spi bus is fast, running at 32 
mhz, and the switching noises ring like the liberty bell with harmonics 
in the 100 mhz range, theres nothing even remotely close to a real 
ground even if everything is grounded at a single bolt in the bottom of 
the box this is all in.  With my scope on an isolating plug adapter and 
grounded to this bolt, the switching noises 6" away on a flat braided 
ground bus exceed 5 v p-p. I've about half a pound of ferrite chokes at 
the drivers power and output cables. I can clip onto the edge of a usb 
port on the pi's board, and 3" of air away, theres nearly 2 volts of 
this noise on most any ground pin on the 7i90.

I have the error voltage range set for a bit over 1 volt in the ini file, 
but even 10 volts doesn't fix it, I get joint errors when they aren't 
moving in 30 seconds, and if I move a motor at 10% of its speed 
capability, the motors run, but are randomly "skipping a beat" and you 
can see the drive belt stop for a few milliseconds. I've had the motors 
take off and run 3" from these noise induced bus errors on several 
occasions while I was standing there contemplating my sins of years 
past. The on-screen dro often does not show these movements. Or the dro 
may show a 3 foot movement, which of course is when it throws joint 
errors in both joints.

I have samples of an isolator chip ti makes requested, which are supposed 
to be able to handle digital data at 100 to 150 mhz, but they've not 
materialized in my mailbox yet. One of them would be ideal, a 4 bit 
model, with 3 sending data to the 7i90, and one bit going back the the 
pi, just what doctor Gene ordered. That "might" solve the problem.

So at the end of the day I have two problems. Errors in the spi bus out 
the yang, and those errors then cause errors in the step timing that 
will stall the motor at 1/2 the speed its capable of. All caused by the 
noise from the drivers switching activity even when the drivers are 
powered by analog supplies. The cables to the motors are foil shielded, 
and that shielding is grounded to the common bolt as the cable goes by 
it on its way to the motor. Ditto the cable from the encoder, which is 
not grounded to the lathe except going by that star ground bolt.

> Resonance seems to be resolved AFAIK like 10 yrs ago with GeckoDrive,
> then GeckoDrive rendered obsolete by this DSP stuff, then THAT was
> rendered obsolete by DSP+3phase.  Of course this doesn't mean a
> stepper can do 10K RPM, but the torque does perform to the spec
> profile at least.
>
> Mechanical dampeners are obsolete, unless you want a retro "steampunk"
> aesthetic.

At this point I could care less what it looks like as long as it works.

This is a run what I had on the shelf unless it won't do the job. Those 
were the last 2 motors I had. This motor, a Nema 24, is one of two 
slightly different birds I ordered 2 weeks ago. All the torque I could 
get, fitting in the space I had.

> There's one exception that DSP drives can't tolerate a 4th order
> system, i.e. a springy connection between the motor and load. Unless
> the motor has its own dampening.   But no one does

Re: [Emc-users] nema 24 motors.

2017-01-23 Thread Danny Miller 
What drive and system voltage are you using here?

Toroids don't make any sense anymore.  Switching power supplies DO 
perform great, unless you  overload 'em with BEMF, but a toroid is 
vulnerable to that too.  Specifically Meanwell switching supplies 
perform reliably.

Resonance seems to be resolved AFAIK like 10 yrs ago with GeckoDrive, 
then GeckoDrive rendered obsolete by this DSP stuff, then THAT was 
rendered obsolete by DSP+3phase.  Of course this doesn't mean a stepper 
can do 10K RPM, but the torque does perform to the spec profile at least.

Mechanical dampeners are obsolete, unless you want a retro "steampunk" 
aesthetic.

There's one exception that DSP drives can't tolerate a 4th order system, 
i.e. a springy connection between the motor and load. Unless the motor 
has its own dampening.   But no one does a springy thing like that.  
Ordinary spring couplers don't count as springy for this purpose.

Yep full disclosure I drank one too many at the moment, but I'm 
instinctively compelled to get right to the point and help you with your 
resonance thing.  Get some 3ph and the 3DM683 and I think you'll start 
to cry.

Danny

> Its amazing the papers one can come across from a google search.  For
> instance, this one bears testing out:
>
> 
>
> Look at the last wiring diagram.  I may try this tomorrow with the small
> motor just for S&G.  The theory is that it rotates the resting position
> by 1/2 of whatever the microstep angle is, with the real effect coming
> from there never being a condition where one winding is completely off.
>
> This should result in a smoother step whose absolute movement angle is
> more consistent from step to step regardless of the current setting,
> where with the upper two configurations, smoothness and equal angle per
> step performance is much more dependent on the current mapping in the
> driver matching the magnetic characteristics of the motor. I am going to
> put the nema 24 motor in but that depends on whether I had the great
> good sense to buy two of those 20 tooth pulleys, so I can bore the 2nd
> one to 8mm. It will be a bit under driven, the m542T driver does 4.2
> amps peak at full song, but this motor says 4.5 amp rms for max twist.
>
> Might have to buy a heavier driver & toroid power tranny to feed it.
> This one is heating some feeding the M542T 46 volts at its full current
> of 4.2 amps peak.
>
> News tomorrow night maybe.
>
>
> Thanks Danny.
>
> Cheers, Gene Heskett


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Re: [Emc-users] nema 24 motors.

2017-01-23 Thread Gene Heskett 
On Tuesday 24 January 2017 01:11:40 Danny Miller wrote:

> Dude, drop the 2-phase bipolar stuff and move to 3 phase!  Or at least
> DSP drives.
>
> http://www.ebay.com/itm/Nema-23-3phase-1-8N-m-255ozf-in-stepper-Motor-
>57mm-frame-8mm-shaft-57J1285-658-/262562493149?hash=item3d21f1b2dd:g:fM
>sAAOSwCfdXor7F
>
> http://www.ebay.com/itm/LeadShine-3DM683-3-Phase-Digital-Stepper-Motor
>-Driver-20-60VDC-0-5-8-3A-NEW-/222183145504?hash=item33bb25c020:g:JU4AA
>OSw0kNXg2ZV
>
> That's a programmable DSP drive.  That's a great combo.  3 phase's
> torque does not drop off until significantly later than 2-phase.  They
> run smoother and don't need dampening.  Torque numbers are not
> entirely equivalent since the 2-phase is typically limited by where
> the high-speed torque drops off, not the base torque.  There are
> larger ones available.
>
> But programmable DSP drives alone do great things with 2-phase:
>
> http://www.ebay.com/itm/1PC-Leadshine-AM882-Digital-Stepper-motor-Driv
>e-80VDC-0-1-8-2A-protect-function-/252635288934?hash=item3ad23c9566:g:M
>UQAAOSwT6pVmTam
>
> You go through a setup, tell it to auto-tune for that specific motor,
> and it's unlikely you'll ever have vibration issues.
>
> Danny
>
> On 1/23/2017 11:45 PM, Gene Heskett wrote:
> > Greetings all;
> >
> > I see some "Nema 24" motors at quite reasonable prices showing up on
> > fleabay, in fairly high torque ratings, so I bought one 10 days
> > back, since I need a stronger one, with perhaps a damper on it on my
> > x axis. I bought the 8 wire model so I can drive it in parallel
> > where I ought to be able to get 3k rpms out of it. The mount bolt
> > pattern appears to be a duplicated of nema 23, but the body is just
> > a wee bit fatter, the shaft is double ended 8mm, and the whole thing
> > looks like it will fit behind the new apron with about 5mm of
> > clearance between the back shaft end and the face of the bed.  So
> > its perhaps 5mm longer than the double ended nema 23 rated at 235
> > oz/in in there now.
> >
> > So I need to locate a 20 tooth, 8m bore pulley before I make the
> > swap.
> >
> > Now, I don't believe this is going to help with the resonance stalls
> > I am getting at about 30 ipm, so I'm thinking of building a viscous
> > damper to fit on the rear of this puppy.  But unlike the ones on my
> > hf micromill, which are long steel spools carrying a 2+ inch stack
> > of heavy fender washers with elastomer sheets between the washers,
> > which are true shock absorbers as the resonance is killed by the
> > frictional losses as the washers walk on the talcum covered
> > elastomer, but I don't have room for a 2+" stack of fender washers
> > in this spot. 5/8" axially at best.
> >
> > I do have room for a larger diameter assembly on the back, so I am
> > thinking in terms of a 1/2" thick by maybe 4" in diameter alu wheel,
> > drilling in from the side at a low angle to put a couple set screws
> > in to clamp it to the motor shaft, and knock down 1 or 2 of my 00
> > buck 12 gauge rounds, measure them, and bore as many pockets in the
> > rim as I can fit leaving about 20 to 30 thou for the balls to move
> > within the pockets filled with grease, and sealed over. A thin
> > gasket to contain the grease, and a 1/8" thick cap ring with a pair
> > of 0-80 cap screws into the fillets between the pockets should make
> > a good torsional vibration damper.  Or plow a groove for a 1/16"
> > o-ring on the outside of the cap, and the inside radius of the cap
> > ring on one side of it. Useing the o-rings would tend to make the
> > grease self distributing, and the small clearance might even aid in
> > the damping if I intentionally plow a shallow 3rd groove between the
> > grooves for the sealing o-rings would further enhance the viscous
> > losses of the grease moving back and forth between pockets thru that
> > narrow passage.
> >
> > What do the vibration engineers in this crowd think of this idea?
> >
> > Cheers, Gene Heskett
>
Its amazing the papers one can come across from a google search.  For 
instance, this one bears testing out:



Look at the last wiring diagram.  I may try this tomorrow with the small 
motor just for S&G.  The theory is that it rotates the resting position 
by 1/2 of whatever the microstep angle is, with the real effect coming 
from there never being a condition where one winding is completely off. 

This should result in a smoother step whose absolute movement angle is 
more consistent from step to step regardless of the current setting, 
where with the upper two configurations, smoothness and equal angle per 
step performance is much more dependent on the current mapping in the 
driver matching the magnetic characteristics of the motor. I am going to 
put the nema 24 motor in but that depends on whether I had the great 
good sense to buy two of those 20 tooth pulleys, so I can bore the 2nd 
one to 8mm. It will be a bit under driven, the m542T driver d

Re: [Emc-users] nema 24 motors.

2017-01-23 Thread Danny Miller 
Dude, drop the 2-phase bipolar stuff and move to 3 phase!  Or at least 
DSP drives.

http://www.ebay.com/itm/Nema-23-3phase-1-8N-m-255ozf-in-stepper-Motor-57mm-frame-8mm-shaft-57J1285-658-/262562493149?hash=item3d21f1b2dd:g:fMsAAOSwCfdXor7F

http://www.ebay.com/itm/LeadShine-3DM683-3-Phase-Digital-Stepper-Motor-Driver-20-60VDC-0-5-8-3A-NEW-/222183145504?hash=item33bb25c020:g:JU4AAOSw0kNXg2ZV

That's a programmable DSP drive.  That's a great combo.  3 phase's 
torque does not drop off until significantly later than 2-phase.  They 
run smoother and don't need dampening.  Torque numbers are not entirely 
equivalent since the 2-phase is typically limited by where the 
high-speed torque drops off, not the base torque.  There are larger ones 
available.

But programmable DSP drives alone do great things with 2-phase:

http://www.ebay.com/itm/1PC-Leadshine-AM882-Digital-Stepper-motor-Drive-80VDC-0-1-8-2A-protect-function-/252635288934?hash=item3ad23c9566:g:MUQAAOSwT6pVmTam

You go through a setup, tell it to auto-tune for that specific motor, 
and it's unlikely you'll ever have vibration issues.

Danny

On 1/23/2017 11:45 PM, Gene Heskett wrote:
> Greetings all;
>
> I see some "Nema 24" motors at quite reasonable prices showing up on
> fleabay, in fairly high torque ratings, so I bought one 10 days back,
> since I need a stronger one, with perhaps a damper on it on my x axis. I
> bought the 8 wire model so I can drive it in parallel where I ought to
> be able to get 3k rpms out of it. The mount bolt pattern appears to be a
> duplicated of nema 23, but the body is just a wee bit fatter, the shaft
> is double ended 8mm, and the whole thing looks like it will fit behind
> the new apron with about 5mm of clearance between the back shaft end and
> the face of the bed.  So its perhaps 5mm longer than the double ended
> nema 23 rated at 235 oz/in in there now.
>
> So I need to locate a 20 tooth, 8m bore pulley before I make the swap.
>
> Now, I don't believe this is going to help with the resonance stalls I am
> getting at about 30 ipm, so I'm thinking of building a viscous damper to
> fit on the rear of this puppy.  But unlike the ones on my hf micromill,
> which are long steel spools carrying a 2+ inch stack of heavy fender
> washers with elastomer sheets between the washers, which are true shock
> absorbers as the resonance is killed by the frictional losses as the
> washers walk on the talcum covered elastomer, but I don't have room for
> a 2+" stack of fender washers in this spot. 5/8" axially at best.
>
> I do have room for a larger diameter assembly on the back, so I am
> thinking in terms of a 1/2" thick by maybe 4" in diameter alu wheel,
> drilling in from the side at a low angle to put a couple set screws in
> to clamp it to the motor shaft, and knock down 1 or 2 of my 00 buck 12
> gauge rounds, measure them, and bore as many pockets in the rim as I can
> fit leaving about 20 to 30 thou for the balls to move within the pockets
> filled with grease, and sealed over. A thin gasket to contain the
> grease, and a 1/8" thick cap ring with a pair of 0-80 cap screws into
> the fillets between the pockets should make a good torsional vibration
> damper.  Or plow a groove for a 1/16" o-ring on the outside of the cap,
> and the inside radius of the cap ring on one side of it. Useing the
> o-rings would tend to make the grease self distributing, and the small
> clearance might even aid in the damping if I intentionally plow a
> shallow 3rd groove between the grooves for the sealing o-rings would
> further enhance the viscous losses of the grease moving back and forth
> between pockets thru that narrow passage.
>
> What do the vibration engineers in this crowd think of this idea?
>
> Cheers, Gene Heskett


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[Emc-users] nema 24 motors.

2017-01-23 Thread Gene Heskett 
Greetings all;

I see some "Nema 24" motors at quite reasonable prices showing up on 
fleabay, in fairly high torque ratings, so I bought one 10 days back, 
since I need a stronger one, with perhaps a damper on it on my x axis. I 
bought the 8 wire model so I can drive it in parallel where I ought to 
be able to get 3k rpms out of it. The mount bolt pattern appears to be a 
duplicated of nema 23, but the body is just a wee bit fatter, the shaft 
is double ended 8mm, and the whole thing looks like it will fit behind 
the new apron with about 5mm of clearance between the back shaft end and 
the face of the bed.  So its perhaps 5mm longer than the double ended 
nema 23 rated at 235 oz/in in there now.

So I need to locate a 20 tooth, 8m bore pulley before I make the swap.

Now, I don't believe this is going to help with the resonance stalls I am 
getting at about 30 ipm, so I'm thinking of building a viscous damper to 
fit on the rear of this puppy.  But unlike the ones on my hf micromill, 
which are long steel spools carrying a 2+ inch stack of heavy fender 
washers with elastomer sheets between the washers, which are true shock 
absorbers as the resonance is killed by the frictional losses as the 
washers walk on the talcum covered elastomer, but I don't have room for 
a 2+" stack of fender washers in this spot. 5/8" axially at best.

I do have room for a larger diameter assembly on the back, so I am 
thinking in terms of a 1/2" thick by maybe 4" in diameter alu wheel, 
drilling in from the side at a low angle to put a couple set screws in 
to clamp it to the motor shaft, and knock down 1 or 2 of my 00 buck 12 
gauge rounds, measure them, and bore as many pockets in the rim as I can 
fit leaving about 20 to 30 thou for the balls to move within the pockets 
filled with grease, and sealed over. A thin gasket to contain the 
grease, and a 1/8" thick cap ring with a pair of 0-80 cap screws into 
the fillets between the pockets should make a good torsional vibration 
damper.  Or plow a groove for a 1/16" o-ring on the outside of the cap, 
and the inside radius of the cap ring on one side of it. Useing the 
o-rings would tend to make the grease self distributing, and the small 
clearance might even aid in the damping if I intentionally plow a 
shallow 3rd groove between the grooves for the sealing o-rings would 
further enhance the viscous losses of the grease moving back and forth 
between pockets thru that narrow passage.

What do the vibration engineers in this crowd think of this idea?

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)
Genes Web page 

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