A Dumb Idea? Stepper Motors As Power Feeds.

Thanks Jim.
That PWM driver for the dc motor looks like a great idea for the price. Would be much more efficient than a simple voltage divider.
I had considered using a more sophisticated voltage control but initially thought it would be too expensive to be worth it for the limited time the motor would run - still amazes me how cheap you can get electronics out of China these days.
 
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MozamPete,
I've had the same idea for awhile.
I priced dedicated power feeds fom my mill and for the price it looked like I can buy a 3 axis CNC conversion kit for the price of one or two power feeds.
I haven't started on mine yet so I'll be watching to see which way you go and how it works out.
So I hope you post the good with the bad and if there ends up being anything you'd wished you'd done different or lack of certain functionality.
Good luck with the project.
 
They will work great! Just make sure the motor is sized large enough to provide the needed torque.
Jim can you please elaborate on how one can actually determine what is the minimum size stepper that is needed for a particular mill. I assume larger mills require larger steppers but I would like to keep the stepper I select for my X& Y axis as compact as possible.
Thanks
Ron
 
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Ron, I fixed your post above, you had your text inside the quotes;)

That is a really good question. My theory on CNC is to go as big as possible, then cut back the power on the drive if needed. Consider that a 1200 oz/in NEMA 34 steppers would run any axis full size knee mill just fine. That motor is about 5 inches long and about 3 inches square, so pretty small. Many of the mini mill conversions are using 400 oz/in NEMA 23 steppers, a little shorter and about 2.5 inches square. It also depends on if you are using ball screws or the original screws. It takes a lot more torque to turn the Acme screws.
 
Ron, I fixed your post above, you had your text inside the quotes;)

Thanks Jim
I saw what had happened but didn't know how to fix it.
With regard to the stepper size I think I will try the larger torque NEMA 23's for the X&Y but probably use a NEMA 34 to raise and lower the head
Ron
 
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Ya did it again:grin: That's OK, I fixed it again. Note where your cursor is at before you start typing.

With regard to the stepper size I think I will try the larger torque NEMA 23's for the X&Y but probably use a NEMA 34 to raise and lower the head

That is the common arrangement on the small mills.
 
Hi Jim
Sorry but I am not sure what I am doing wrong.
I am writing on an iPhone and I am unsure how to reply such that my message is outside the quote. My first message required the first part of the quote because your post was somewhere up the thread.
Will try better next time.
Anyway thanks for your help
Ron
 
Hi Jim
Sorry but I am not sure what I am doing wrong.
I am writing on an iPhone and I am unsure how to reply such that my message is outside the quote. My first message required the first part of the quote because your post was somewhere up the thread.
Will try better next time.
Anyway thanks for your help
Ron
Ron,
Using the iPhone, the quoted text will be terminated with "[/QUOTE]"
You want to be sure that your new text come after that.


Steve Shannon, P.E.
 
You don't need a PC to run a stepper, just the motor, a drive, and a pulse generator. I have a couple on the shelf that I use for testing systems.

From my post above:

You can use one of these to run the stepper manually http://www.ebay.com/itm/Stepper-Mot...d87660&pid=100338&rk=6&rkt=26&sd=281570110066

Or a little more sophisticated, with drive,
http://www.ebay.com/itm/Reversible-...d=100338&rk=8&rkt=26&mehot=pp&sd=281570110066

Or even with remote control,

http://www.ebay.com/itm/Adjustable-...87660&pid=100338&rk=11&rkt=26&sd=281570110066

And this controller will give you almost 100% torque at zero RPM with a DC motor
http://www.ebay.com/itm/MAX-10-50V-...689235?hash=item2ee45b6013:g:w1kAAOSwHnFVvr2I


Hi Jim,

I found myself here thinking about a similar solution, but i am out of my normal zone. How would this setup handle manual turning of the leadscrew handle? I assume one wouldnt have to overcome the holding torque as power would be off the motor, but arent there issues with turning over steppers and it driving a voltage back towards its drive? Is this somehow accounted for here? Apologies if that is a stupid question, as i mentioned i'm (as yet) out of my depth on this.

Thanks,
Kevin
 
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