dc servo spindle anyone?

[jed102]

Hello,

I'm just wondering if anyone is using Deskcnc or Mach3 and a servo drive to control a dc servo spindle on their cnc setup. If so, I would really like to hear how well it works for you and how easy it was to implement.

I have several cnc projects on the go right now and this seems to be an area not well covered. There is a lot about 220v 3 phase variable frequency drives, but this however is not an option for me at present, and also I think it would be great to be able to position a lathe spindle and drill bolt hole patterns with live tooling etc.

Thanks,

Frank

[BobWarfield]

Yahoo, a man after my own heart. I've been talking about this for awhile, trying to get some takers.

Now for the bad news. You're the first one I've come across who was particularly interested. There are mysterious issues with Mach and using a servo as spindle. I know it won't work at all with GRex until the firmware is rewritten. GRex will also insist on an encoder on the spindle, so it may as well be a servo. No threading with GRex until the firmware rewrite.

Do you have a suitable servo motor yet? If so, I would just try to experiment with it. Also, you'll need to get onto the Yahoo Group for Mach where Art lives to make real progress here.

If you don't have such a motor, I have been interested in adding an encoder to the DC treadmill motor many use on small lathes. I have heard varying opinions about this. I came across a fellow who did this for a Bridgeport conversion and swears by it. I came across others who say that without a true servo motor, you're going to get unpleasant cogging effects. The experts are not in agreement about all this. Anyway, the guy who has done it is here:

http://www.truetex.com/servomod.htm

I do agree though, live tooling would be the cat's meow. It would also be real nice for someone that has a 3-in-1 machine to be able to index the spindle so it can act as a 4th axis.

Best,

BW

[jed102]

Hi Bob,

I'm glad that there is at least one other person interested in this concept. I really don't want to have to wait forever for Mach/grex to get something happening. I understand that Deskcnc has provision for an encoder feedback servo spindle, but haven't heard much from users about how well it works etc.

I actually have converted a larger 2.5 hp version of the same motor shown in the link you provided to a servo by adding a 200 count US digital encoder. It is already mounted on my large mill retrofit and Rutex has given me the go ahead to drive it with their large servo driver if I limit the voltage to 116 v. I also have a shorter 2 hp version on my Hardinge lathe conversion.

I sure agree that it would be excellent to have a servo spindle for a 3 in 1 machine also. Never really thought about that. Of coarse there are other advantages over ac variable frequency drives like being able to use lower hp motors and still have great torque at very low rpms.

I hope a few more people like us reply to this in order to, maybe, at least stir up a little demand for something.

Frank

[BobWarfield]

I am starting to see some good news on the GRex front. I dinged them over on the Gecko Yahoo Group about the firmware and Steve Hardy now says January. That's actually not all that far away from my perspective. I'm going to keep monitoring the situation, but I think it helps if folks weigh in about wanting to do this sort of thing. Art, Steve, and Mariss may simply not be thinking anyone cares.

Best,

BW

[jed102]

Yes, I guess I should say something over at the yahoo group also. I'll check it out!

Thanks,

Frank