Gene, Are you happy with the MM-542 stepper drivers?
Dave > To stick my oar in this water, I agree. Concise is nice, but when there > are considerable variables to fine tune, the newbee can easily get lost, > blinded by the seemingly endless joint errors. > > For instance, I just switched from a 4 axis xylotex card to a 4 pack of > MM-542's. The xylotex don't do reduced currents when stopped, but the > MM-542's can be set to drop to 50% current when idle. I found I had to > reduce my MAX_ACCEL's about 30% all around, while maintaining a healthy > headroom cushion of over 30% between the TRAJ settings (slower) and the > AXIS settings (faster) in order to get rid of the stalls on reverse > direction startups after an idle period. > > I came to the conclusion that the ramp back to full current was taking more > than a step, and of course if the first step is missed, a stall is going to > happen. So I had to slow down the accels as if the motors weren't getting > full power. This was based on the fact that I could tap the keys after an > idle period for a half second and get a stall, but a quickly repeated tap > always ran normally regardless of which direction the tap was. On a per > axis basis. Moving a different axis was a cold start and stall. > > I also found that microstepping at 16x ran much quieter but gave more joint > errors compared to 8x, but again, reducing the ACCEL's fixed that. I can > now run the logo in nearly the same time, and no joint errors are > encountered at 150% feed rate of 22.5 IPM (same as before) so the slowdowns > didn't seem to seriously hurt that. > > But the docs need to explain this in more detail for the newbee just > bringing a machine to life for the first time. And it should include a > sentence or so about drivers that do reduced idle currents and their effect > on MAX_ACCEL headroom. > > I don't think I will turn the reduced current feature off as the motors > reduced temps can be easily felt. > > As the driver enclosure is largely sealed (its heavy 1/8" and 3/16" alu > plate) the heat buildup there is going to need a larger, say 8", fan > blowing on the box to maintain a safe temp inside the box, but this should > suffice for cooling as there is a big 120 volt, ball bearing "rotron" fan > circulating the air within the box to encourage the heat transfer to the > box panels, so the whole box gets warm without noticeable hot spots. At 2 > hours uptime, I'd guess 15F above ambient without the exterior fan. > > Cheers, gene > ------------------------------------------------------------------------------ Doing More with Less: The Next Generation Virtual Desktop What are the key obstacles that have prevented many mid-market businesses from deploying virtual desktops? How do next-generation virtual desktops provide companies an easier-to-deploy, easier-to-manage and more affordable virtual desktop model.http://www.accelacomm.com/jaw/sfnl/114/51426474/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
