On Thu, 2011-02-10 at 11:34 -0600, James Louis wrote: > Wallace, > > On the other hand if your servo drives require a +/- 10VDC analog > input then it is hard to beat this combination in my opinion: a Pico > Systems PPMC motherboard with a DAC, ENC, and DIO running off of an > Intel D510MO. > I am delighted with mine. > > Jim
I agree. It just depends on what the budget is and the expected performance. I'm just exploring the options and issues. Personally, on a machine with existing servos, I would not use step/dir drives. But the original Mach doesn't support analog amps(?), so I understand why this machine has them. An option is to sell the step/dir drivers and use a hardware signal generator and PWM input amps, which is what I have on my HNC lathe. I think it would be harder to use the hand wheels this way (DRO mode). Two separate configs might be needed. I haven't tried it yet, but I would prefer to remove the hand wheels and make MPG's for each axis for "manual" hand wheel mode. Theoretically, it should be the same as real hand wheels, but with benefits. This requires the integrator to be fairly creative and might not be worth the effort. Oops, I just realized, in my last post, to use the hand wheels the drives will have to be disabled. This may make the drives lose there position or there might be issues when they are re-enabled (big difference between encoder position and step/dir input position). Hopefully someone with first hand experience will shed light on this. Thinking aloud -- with the position loop in EMC2, EMC2 would fight the change or would produce a following error. With MPG hand wheels, the hand wheel position, commanded position, and encoder position would normally be in sync in auto and manual modes. With a step/dir servo, if one tries to move the hand wheels the drive will try to correct the position back to the original position. The drive might alarm, or if EMC2 reads the encoders, EMC2 might alarm. Either way, in order to use the manual hand wheels manually, the loss of position will need to be considered. Another thought, I believe some resolution could be gained by going to a hardware signal generator/encoder counter. It depends on the current step/dir configuration. A step input might invoke a move of, let's say ten encoder counts. With a PWM (analogish) system the position could be controlled down to an encoder count or two, a least doubling resolution. Of course it would be better if the mechanical system were tight enough to take advantage of the increased resolution. -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/index.html California, USA ------------------------------------------------------------------------------ The ultimate all-in-one performance toolkit: Intel(R) Parallel Studio XE: Pinpoint memory and threading errors before they happen. Find and fix more than 250 security defects in the development cycle. Locate bottlenecks in serial and parallel code that limit performance. http://p.sf.net/sfu/intel-dev2devfeb _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
