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Anonymous Poster

Power Requirements and Stepper Motors

01/15/2009 8:41 AM

Hello, Im design a CNC router for a college project, but im getting a bit stuck with the calculations.

I've done an experiment to try and calculate the force required to cut a groove though a sheet of MDF at a depth of 6mm with a woodworking router, this showed that with a mass of 8kg attached to the router with a piece of string would pull the router at said depth at a rate of 0.02m/s.

So, the question is, how can I use this information to calculate the power required to move that router in watts, instead of kg. And then use that to calculate the stepp

I'd really appreciate any information you can give me on this, I'm really struggling to get my head around it.
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JohnDG
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#1

Re: power requirments and stepper motor confusion

01/15/2009 8:51 AM

Ignore the power in watts.

You know the force and speed. Choose a drive system (ballscrew, belt & pulley or whatever). Calculate the torque you'll need to turn the screw/pulley etc, and the rate you'll have to turn it at. Now look at stepper motor torque/speed characteristics, and find the smallest motor/gearbox combination that will drive your router with the required speed & force. Remember to allow for the losses in your drive & gearbox. Go for about 2 to 3 times the torque you've calculated that you'll need (safety margin).

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Andy Germany
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#3
In reply to #1

Re: power requirments and stepper motor confusion

01/16/2009 6:49 AM

GA from me.

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Hendrik
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#2

Re: Power Requirements and Stepper Motors

01/15/2009 10:55 AM

Just a tip. Instead of cutting all the way at once rather investigate using 2 or more passes and increase the feed rate. this usually reduces sideways force on the spindle motor bearings.

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Andy Germany
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#4

Re: Power Requirements and Stepper Motors

01/16/2009 6:51 AM

Not quite your question, but have you investigated the software and the electronics needed? If not, I could help you "Offline" if you wish.....

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Anonymous Poster
#5
In reply to #4

Re: Power Requirements and Stepper Motors

01/27/2009 8:49 AM

Hi, thanks for getting back to me.

Sorry I should have mentioned I will be using a belt drive system.

So supposing I will be using a 20mm diameter pulley, with a belt going between 2 of those, and it takes 8kg of weight to move the belt at a speed of 0.02m/s, how can I work that out as a torque?

Thanks

ps, Andy German, I would really, really appreciate help with the electronics when I come to it in a few weeks, i'll let you know.
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JohnDG
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#6
In reply to #5

Re: Power Requirements and Stepper Motors

01/27/2009 10:06 AM

If you register & send me a private (CR4) mail with your e-mail address, I can send you a pdf describing all the calculations you need. Unfortunately, can't send attachments within CR4.

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jwest22
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#7
In reply to #6

Re: Power Requirements and Stepper Motors

01/27/2009 10:40 AM

Hi, I've regestered, and sent you a message.

Thanks
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JohnDG
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#9
In reply to #7

Re: Power Requirements and Stepper Motors

01/27/2009 6:22 PM

Hope it helped. If it's still unclear, come back - I'll try to find some time to work on it.

Right now, I've got to sleep - early start & long drive tomorrow.

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Andy Germany
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#8
In reply to #5

Re: Power Requirements and Stepper Motors

01/27/2009 1:54 PM

I'll do my best, I know a few good places where you can either buy kits or finished PCBs.

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Previous in Forum: where can i find list of stand. size of pipes?   Next in Forum: Turbine Hunting 1000 KW Backpressure
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