Re: Re: MachMotion vs. DIY for a Bridgeport

Although the system suggested below would work fine on a Taig-sized machine, I don't think you'd get very good performance on a Bridgeport with the G540 and 23-frame 200 oz-in motors. If you geared them down to have enough torque to move those heavy stages without losing steps, rapid traverse rates would be extremely slow. At very least, you'd want 34-frame stepper motors with 600 oz-in holding torque or better, and if you wanted to use Gecko drives the G203V, which can handle higher voltage, would be a better choice to run them. A step up from that would be the G320 drives and brush-type servo motors, with some timing-belt and pulley reduction to trade some of their speed for more torque. The Mitsubishi AC servo/drive combos or Danaher brushless system that Machmotion sells would probably perform even better, but of course they cost a lot more.

Andrew Werby
www.computersculpture.com



"Danny Miller" dannym@... oznog2002
Date: Tue Feb 17, 2009 10:32 pm ((PST))

Well, I haven't seen the Bridgeport, but after having gone through this...

(See previous answer for the Taig guy)
A single Gecko G540
48v 7.3A power supply from eBay

>200oz square-bodied steppers. NEMA23 type.

Desktop PC with a parallel port, one with a video card not just on-board
video (though you can get around this by adding a video card). Mach3
software to control it.

The ONLY real tricky part here is you need NEMA23-sized motor mounts
that specifically fit the Bridgeport. I can't help you there, if nobody
here knows and eBay gets you nowhere go to CNCZone forum.

I'm not sure what shortfalls in steppers you're referring to. Servos
CAN be faster, but probably not for a mill. The G540 can drive already
steppers faster far faster than many types of commonly milled stock
could ever even be machined at, and it's beside the point because the
steppers can already meet or exceed the maximum recommended speed for a
lot of milling machines. The big routers which have high-speed transit
capabilities, and use wood stock which can (and generally should) be
routed at >100ipm are where the servos become useful. A Geckodrive
seems to get around all the hardware problems and pains that would cause
steppers to stall or lose steps.

This setup is pretty much guaranteed to not only work without
complications, it'll actually deliver some top-notch performance. It
will also be surprisingly cheap. That setup should be under $500 in
parts, not including motor mounts which I can't estimate.

Danny

danieltmedlin wrote:

> I have a Bridgeport Interact CNC mill.