Yes.. I agree. Though my favorite thing to setup on a linuxcnc machine is an encoder wheel for jogging and overrides... What I use the most is maximum velocity over ride.. allows you to sneak up on part...
On Sun, Sep 19, 2021, 2:53 PM John Dammeyer <jo...@autoartisans.com> wrote: > Hi Sam, > I must admit there's a certain amount of fear every time I press the go > button for a CNC program. Especially when I started mucking around with > tool #'s and offsets. My hand now overs over ESTOP when I press start. > Watching a tool that appears too low scream over to the part held in the > vise at a G0 180 ipm is not for the faint of heart. > > But then the first time I apply power to a newly assembled power supply my > heart is also in my throat. For one product, if the Pick and Place people > didn't use enough solder under the ground pad of the regulator chip (the > only ground connection too), it would fry and take out the 8 SMD power > transistors for the dual supply. Very difficult to repair. > > On the servo side, the caps are 200V rated as are the 50A transistors so > theoretically I could run one with 115VAC as the 165VDC supply. That > would certainly provide the force to drive more current into the motor > windings and create the speed desired. With 105V the motor can reach 3000 > RPM with a lighter load, otherwise it would never work on the X axis but > the torque might also just be on the edge during acceleration in one > direction and not the other. > > Or build up a small circuit so I can measure the instantaneous DC current > with the scope (don't have a current probe) and see how much current the > motors are really drawing. Torque is Amps x Turns and if the voltage > isn't there to push the amps then following errors are likely. > > John > > > > > -----Original Message----- > > From: Sam Sokolik [mailto:samco...@gmail.com] > > Sent: September-19-21 12:11 PM > > To: Enhanced Machine Controller (EMC) > > Subject: Re: [Emc-users] DC Servo issues > > > > Lol.. I certainly love the electrics part more than the machining most > of > > the time... > > > > On Sun, Sep 19, 2021, 2:07 PM John Dammeyer <jo...@autoartisans.com> > wrote: > > > > > 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 > > > > > > > _______________________________________________ > > 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
