I am building a 4'x8' CNC router table for a school project. The router has to be able to cut 3/4 in plywood. I am looking into purchasing the following motors:

http://cgi.ebay.ca/ws/eBayISAPI.dll?ViewItem&category=12577&item=3860595205&rd=1&ssPageName=WDVW#ebayphotohosting

My gantry will be driven by belts and will approximately weigh around 60-70lbs. Does anyone have an opinion on if these motors will be able to do the job? Is the torque enough?

Another question I have is how do you know if you should step your motos down and if you should how do you know by how much?

Thanks

Hello Dowling...

They look nice motors. For the size of your machine (8*4) I think you will be underpowered. I am also building an 8 * 4.. (see Project log... New Obsession) and I am also using a Belt Drive for the X Axis.

I will be using Servos (880 oz.in) geared down 9:1. on the X.. Even with this size I am a little concerned I may need a larger motor for the X Belt Drive. Gearing should provide about 3HP at the belt.

The motors you are looking at are Steppers which have their torque at low RPM's. This may mean you would be looking at no gearing to obtain enough torque.

Your gantry is not too heavy and depending on your bearing system will determine how much power is needed to drive it.

If you are going to use steppers I would recommend using a stepper over the 1,000 oz.in for the X drive. Even for your Y axis you would be wise to find something more powerful...

Happy building

I have a belt driven axis of around 48" travel. It is driven by only a 110 Oz/In stepper, rated 1.3A @ 5.1V. It will push my 2-1/4 HP Makita router around at about 80 IPM and thats at only 5V to the stepper, as my current drivers aren't the chopper type. Unfortunately my Y axis (ballscrew) will only do ~17 IPM.
I'm not saying that the motors you point out will work well, just that you may be surprised at how well a stepper works for belt drive. With steppers you'll still need some gearing to increase resolution. Belt drive is inherently low resolution. Increasing resolution by gearing will also increase torque.
Do some more research, that's alot to spend if you're not sure it's going to work.

Regards Terry.....
http://www.terry-is.f2s.com/