Hi Sam, See below. > From: Sam Sokolik [mailto:samco...@gmail.com] > > I have never used servo drives that close the loop.. I have always had > great luck with normal closed loop within linuxcnc. (cheap used amc > drives) > > (Actually - I take that back - I have used the stmbl drives. so far only > for a spindle..) > > This is of course using mesa analog interface hardware. > > The only time I had issues with encoder counting was when I thought I could > get by with single ended encoders going over 8 ft... > > Look at something like this.. 20000 counts per rev, 2 axis with 4000? > counts per rev... (and the encoders came installed on the servo, single > ended and I think they are us-digital) > If I was missing counts during these complicated sync moves - you would > certainly see it. > > https://www.youtube.com/watch?v=-4sKHBh6rDk > > (plus no 3rd party software to tune...) - Granted you have the drives and > are familiar with them - at what point do you give up? > > sam
That's the question. One possibility to try is to grab 110VAC line voltage. Put a bridge and caps on it and drive that motor with more than the 105VDC power supply. I'll have to check if my transistors are rated for the 165VDC rectified voltage and I really would rather have them be 250V transitors. And then there's the filters on the board too. The UHU circuit was originally for up to about 75V. The HP_UHU came about for higher voltage drives; Just don't know if I built mine for more than 125VDC although the circuit design parts are for 11A. I _have_ tried one these motors with the STMBL but could never get it tuned and support from the designers was inadequate to help me so I gave up. I'd rather be machining... John > > On Sun, Sep 19, 2021 at 12:59 PM John Dammeyer <jo...@autoartisans.com> > wrote: > > > Hi Rick, > > It may also have something to do with the DC Servo drive electronics. > > Although it's differential encoder signalling the design may have internal > > issues that are somewhat corrected by the Henk Olsson module. I had both a > > small electrolytic and ceramic capacitors right by the US Digital encoders, > > which BTW, have been discontinued for a few years. Perhaps that's why? > > Issues? > > > > I swapped the X and Y motor/encoder pair and sure enough the problem moved > > to the Y axis along with now only 120 IPM instead of 150 IPM. Above that I > > get following errors. Given that this motor has a higher winding > > resistance I'm going to guess it's not a 90VDC motor but is more likely a > > 180VDC motor that was shipped as a 90VDC. Maybe the loading introduces > > noise in one direction that fools the quadrature encoder. It's very > > strange that the following errors are only in one direction. > > > > At $145US plus shipping, since Automation Technologies won't replace it, > > I'm going to cast a new mounting plate for one of the slightly smaller > > 1.27NM Bergerda AC servos. They were destined for the ball screw upgrade > > (and I'd ordered the wrong size thinking they were the same torque as the > > DC ones). So we'll see. If the Bergerda does well on the heavier Y axis > > then problem solved. > > > > More as it unfolds. > > > > Oh I swapped motor/encoder sets between X and Y,and with the Y motor > > running the X axis the test program that runs the table back and forth no > > longer has a slightly different sound between changing direction CW > > compared to CCW. So it appears that's also on the motor and not LinuxCNC > > nor the MESA. And absolutely no errors in position on X. Only now on the > > Y instead. That lets the HP_UHU servo drive off the hook too. > > > > John > > > > > -----Original Message----- > > > From: Rick Moscoloni [mailto:rmoscol...@gmail.com] > > > Sent: September-19-21 10:12 AM > > > To: Enhanced Machine Controller (EMC) > > > Subject: Re: [Emc-users] DC Servo issues > > > > > > us digital encoders with a capacitor across dc+and- works without a > > > fault.... > > > > > > El dom, 19 sept 2021 a las 2:49, John Dammeyer (<jo...@autoartisans.com > > >) > > > escribi?: > > > > > > > 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 > > > > Emc-users@lists.sourceforge.net > > > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > > > > > > > _______________________________________________ > > > Emc-users mailing list > > > Emc-users@lists.sourceforge.net > > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > > > > > _______________________________________________ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
