Over 10 years ago I bought two of these for the XY axis of the mill. https://www.automationtechnologiesinc.com/products-page/dc-servo-motor/nema34-1125ozin-dual-shaft-servo-motor
Also from US Digital the 250 line encoders. I had assembled HP_UHU kits and had on standby the Henrik Olsson replacement PIC processor modules although this photo shows the original processor. http://www.autoartisans.com/mill/HP_UHU_Modified.jpg One of the things that showed up right away was that with identical drives one motor ran hotter than the other. Further investigation showed the resistance of the windings was different with the warmer motor having the lower resistance and inductance which matched the spec sheet. By then it was too late to return the high resistance one so I decided to put what appeared to be the on spec motor on the Y axis since it had to carry more weight. The X axis got the cooler and higher resistance motor. When I finally got it all together I had a lot of position errors and Henrik convinced me to trash the US Digital encoders which appeared to be losing counts and replace them with the CUI. Changing to Henrik's module improved things and positioning was now reasonably accurate. Until a short while ago on the X axis. I pulled the encoder off remounted things and the problem seemed to go away. Well last week, after the center drilled holes were off from where the 1/4" drill bit went down I realized the problem had returned. After much mucking around it seems that the real issue is still with that X axis out of spec motor. What I did is swap motor+encoder from X <=> Y. The cumulative position errors on X are now gone so that shows the HP_UHU drive was not the issue. What's really interesting is the heavier Y axis now regularly faults at 140 ipm where before the other motor could do 150 ipm. Also interesting when I drop the speeds to below 130 it doesn't fault but I started seeing position errors. The G-Code test program G01 X0 Y0 F60 X-4 Y-1.1 Y0 X0 Y-1.1 Y0 X5 And so on for about 5 cycles. Now the X axis returns to 0 every single time from either side of 0. But the Y axis accumulates -0.020 or so error every time the program runs just like X used to with that motor. Always only negative values. So strange. Also when that motor was on the X axis the sound of the system when changing direction was clunky sounding in one direction and not the other under G-Code. The change direction with jogging keys wasn't like that. I don't think it's worthwhile to spend the time to figure out what's wrong. Seems pointless to continue to use a motor that isn't up to spec. Probably better to just install one of the Bergerda AC Servos I have here that I was saving for the Ball Screw upgrade. Especially since AutomationTechnologies wouldn't replace the motor even though it was clearly out of spec. Not about to buy anything else from them. John Dammeyer _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
