On Mon, 12 Oct 2015, Gene Heskett wrote: > Date: Mon, 12 Oct 2015 15:56:07 -0400 > From: Gene Heskett <ghesk...@wdtv.com> > Reply-To: "Enhanced Machine Controller (EMC)" > <emc-users@lists.sourceforge.net> > To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net> > Subject: [Emc-users] To PCW: retuning for inches > > Greetings Peter; > > In getting a decent rapids w/o following error, I wound up with all the > pid.Pgains at 2000, and while I played with the FF2 setting, couldn't > detect that is was affecting anything I'm smart enough to detect.
PGain should really be 1/period, more _will_ cause overshoot/oscillations > > However, after a move of one of the axis's I can hear a faint tone at the > servo-thread frequency from the motors. Firing up halscope and looking > at the x,y,x outputs, when its singing I can see this tone at all the > pid.outputs, at from 15 to 50 milivolts peak to peak. Move an axis a > couple thou and it may stop. This is most likely the step driver (or excessive Pgain, see above) > > However, when its doing it, the z, being tasked with supporting the > weight of the head, can be seen to move, perhaps as much as 5 thou in a > minute or less. I have twice added half a microsecond to the dirsetup > and dirhold settings, and a quarter to the step widths which seems to > have helped. This particular driver is a DM860 since thats a nema34 > motor, running on 60 volts. And 60 is NOT enough for that high of an > inductance motor. 120 would be about right, and should put its speeds > up there with the 450 oz x&y motors, but no one makes a stepper driver > rated for that high a voltage. The DM860 is also noisey as can be as it > switches from the microstep chosen to lower values as the speeds > requested rises. 3IPM is silent, 30 IPM positively howls, its like a 16 > speed road ranger truck transmission, taking the engine thru its optimum > power rpm range from the traffic light till its out of sight and > hearing. > > So my guess is that the oscillation may be confusing its internal > gearshift. > > What has been the pulse timing settings a DM860 needs in your experience, > and is there something in the pid settings that will dampen that 1 > kiloihertz oscillation out, without lowering the Pgain, which seems to > be required to get any real rapids speeds above 20 ipm. > If you cannnot get rapids above 20 IPM without a Pgain of 2000 you have something badly broken in the PID ( _is_ FF1 1.000? ) I would set the pulse timimg as long as the maximum step rate will allow (with about a 20% margin) > Clues will be gleefully applied at this point. Thanks Peter. > > Cheers, Gene Heskett > -- > "There are four boxes to be used in defense of liberty: > soap, ballot, jury, and ammo. Please use in that order." > -Ed Howdershelt (Author) > Genes Web page <http://geneslinuxbox.net:6309/gene> > > ------------------------------------------------------------------------------ > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > Peter Wallace Mesa Electronics (\__/) (='.'=) This is Bunny. Copy and paste bunny into your (")_(") signature to help him gain world domination. ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
