Modifying stepper motor shafts

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Modifying stepper motor shafts

This topic has 12 replies, 8 voices, and was last updated 4 April 2014 at 21:28 by Michael Gilligan.

Viewing 13 posts - 1 through 13 (of 13 total)

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2 April 2014 at 00:23 #148664
AndyP
Participant
@andyp13730
I have resurrected the cnc conversion of my x1 mill and want to turn down the end of some nema 23 stepper motor shafts from 8mm to 6mm and thread it for the handwheel – double ended motors you see.

I had in mind just to chuck the other end of the shaft in the lathe and keep the motor casing still but will this kill the motor?

I've cut the keyways already.

Cheers

Andy
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2 April 2014 at 00:23 #15039
AndyP
Participant
@andyp13730
2 April 2014 at 08:42 #148672
Les Jones 1
Participant
@lesjones1
Hi Andy,
I can see no reason why this should cause a problem. I think it would be wise to support the motor casing and use a centre in the tailstock end. (Assuming it has a centre drilling.) I would keep the speed fairly slow. I was going to say below the motors maximum speed rating but a quick look at the specifications on ArcEuro's website does not give a maximum speed or stepping frequency. I would guess at below about 400 rpm. (This is just a guess. I have no information to base it on.) Make sure the wires are not shorted together as it will be acting as an alternator. They seem to use small stepper motors in this way in wind up torches.

Les.
2 April 2014 at 09:00 #148673
Douglas Johnston
Participant
@douglasjohnston98463
Might be easier to keep the 8mm diameter and modify the handwheel, although that may not always be possible.

Doug
2 April 2014 at 09:33 #148674
Russell Eberhardt
Participant
@russelleberhardt48058
Posted by Douglas Johnston on 02/04/2014 09:00:57:

Might be easier to keep the 8mm diameter and modify the handwheel, although that may not always be possible.

Doug

Or even make a new handwheel?

Russell.
2 April 2014 at 10:49 #148680
Michael Gilligan
Participant
@michaelgilligan61133
Posted by Russell Eberhardt on 02/04/2014 09:33:53:

Posted by Douglas Johnston on 02/04/2014 09:00:57:

Might be easier to keep the 8mm diameter and modify the handwheel, although that may not always be possible.

Doug

Or even make a new handwheel?

Russell.

.

Or, better yet … use these

They are flexible in bending, but stiff in torsion.

MichaelG.
2 April 2014 at 19:25 #148727
AndyP
Participant
@andyp13730
Thanks for all the good ideas guys, turned down no problem, tailstock support and motor lightly held in the fixed steady, 200rpm on the Boxford and a sharp hss tool.

I had thought of but discounted an adapter because the damn things are going to stick out an awfully long way anyway but John's advice to "modify the cheapest bit" makes excellent sense – I must try and remember that bit.

Andy
2 April 2014 at 19:48 #148729
jason udall
Participant
@jasonudall57142
A thought.
Have a care with the wires of the stepper…
The motor will (if a hybrid stepper)..generate quite large voltages…
Don’t short them as this will cause the motor body try to turn with shaft
..ideally add resistors..or low wattage light bulbs ..or better still neons .. “shorting” the coils. .the motor will still try to turn with the shaft but the voltage won’t get chance to flash over the coils.
Well that’s what I would do..
2 April 2014 at 21:45 #148751
John Haine
Participant
@johnhaine32865
If you have the motor connected to a driver, even if the power is off it will be quite hard to turn the handwheel as the stepper charges capacitors in the driver. If you want manual control best unplug from the driver. Even better, use a manual pulse generator (MPG) to drive the stepper via Mach 3. I'm looking at "stepperature" which uses small steppers as encoders for just this.
2 April 2014 at 21:58 #148753
Michael Gilligan
Participant
@michaelgilligan61133
John,

Thanks for your lead to stepperature

… I was unaware of it … Looks very promising!!

MichaelG.
3 April 2014 at 09:53 #148786
Douglas Johnston
Participant
@douglasjohnston98463
I have a stepper motor drive connected to the right hand end of the leadscrew of my Myford speed 10 lathe and use the enable input of the driver to disable the motor when it is not running.This arrangement has worked fine for some time but I do sometimes feel uneasy when I use my mandrel handle for screwcutting.

The turning of the mandrel handle rotates the stepper motor (incidently there is very little resistance caused by the motor&nbsp and I do worry about the back emf generated by the motor and the effect this might have on the well-being of the driver electronics. I presume that modern drivers have protection built in to prevent damage of this kind, but I still worry.

Doug
4 April 2014 at 21:20 #148930
Ian P
Participant
@ianp
Posted by Michael Gilligan on 02/04/2014 21:58:47:

John,

Thanks for your lead to stepperature

… I was unaware of it … Looks very promising!!

MichaelG.

I wonder why the designer used a stepper motor for the basis of his design, he admits it can miss pulses at slow speed. Surely it would be better to use an optical encoder from an old computer mouse (or even an optical mouse)?

The only thing I can see the stepper being used for here is to provide a well engineered spindle with some detent action.

Ian P
4 April 2014 at 21:28 #148933
Michael Gilligan
Participant
@michaelgilligan61133
Ian,

Yes, on further consideration I'm inclined to agree.

MichaelG.
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