DC Servo motors

[osdhillon]

hi,

I am looking for DC servo motors (With encoders) which are compatible with Gecko G320 Drives. Also I am looking for the ACME or Ball scres with nuts. Can anybody guide me to the right supplier/direction. The work area for CNC router is about 4'X4'. Any comments on which motor and screw I should use is appreciated.

thanks
Onkar

[jcc3inc]

Dear Sir:

DC servomotors are of higher quality than regular DC motors. However often regular DC motors like those used on treadmills are used. If you can get a suitable motor without encoders, you can purchase separate encoders from US Digital, mount them on the opposite end of the motor (assuming the shaft projects out), and you have what you need. Manufacturers of servomotors are (were) Electrocraft now Reliance Electric, Dynetic Systems in Minnesota and try Servo Systems Co (used or surplus) and Pittman (they make a small 2" diameter motor). I believe I M Service sells the Pittman motor with encoders on them, or is it gearboxes??

For Acme nuts and screws, try Green Bay Manufacturing, 920-793-2411 in Two Rivers, WI. Ballscrews are made by Rockford Ballscrew, BSA, Nook, and Saginaw as I recall. Rolled thread screws are more economical.

If I were making a 4 foot router, I would use rack and pinion. When I was in business making CNC plasma cutting machines, we used rack and pinion exclusively. Rack and pinion is more tolerant of dirt, has 250 IPM + speed capability, and can be readily setup as dual side drive by means of a cross shaft. You will have no "whip" problems which leadscrews experience above the critical speed. Rack with 20 degree pressure angle is preferred to 14-1/2 degree pressure angle. In fact, my test table is 32" x 36" and uses rack and pinion; I use it as a test table for the controller which I am making and for wood routing. If you Email me. I can send you pix of it.

Regards,
Jack C.

[osdhillon]

Jack

Thanks for your valuable info. It really did help a lot. As i am building this CNC router for home use so my cost considerations are limited (Within $ 2000 max). I found motors and the ball screws. I am using gecko servo drive. In near future I will be building 6'X8' table made out of aluminum and tubes (I will try to keep the table as light as possible). I will have to recalculate the motors and drives probably, but I am selecting Rack and pinion for sure. Nexen group make a nice one and surprisingly the tol of the backlash is 3.2 micro meters (±0.00013 in.). Thanks again for your input and further suggestions are welcomed. There is no limit to the CNC and the power of sharing the ideas.
Cheers,
Onkar

[osdhillon]

Hi,
Jack
I Can you please suggest more on the rack and pinion. Pics will be nice. How did you take out the backlash.

thanks
Onkar

[coherent]

Your original post mentioned a supplier for ballscrews/nuts. I priced them everywhere and chose Roton.. (http://www.roton.com) and am very pleased with the product. I couln't beat their prices anywhere. As far as drivers for either Servo or sterppers, I'd recommend Gecko's. For those try Industrial Hobbies, they offer good package prices with heatsinks and fan.
-marc