On Tuesday 05 April 2016 21:53:21 Gene Heskett wrote: > Greetings all; > > Background: Del Dimension 745 using our wheezy iso install, with a > 5i25 card, driving 3 axis's of steppers, one of the Pico PWM-Servo > amps running the 1 hp pm-dc OEM spindle. > > Having a few to play after getting back from din-din, I went thru the > ini file and raised the Pgain of the steppers PID's to 4000, set the > servo thread down to 250 microseconds and fired up LCNC. Then ran the > G33.1 peck cycle for about 15 minutes, 3 times, while I attempted to > get halscope to show me the data for one plunge, but didn't fare that > well, one plunge takes more time than the halscope can watch in 1 > sweep. > > What I did see indicated that once the moves had started, it was quite > stable. So I let that run and hit a couple news sites with iceweasel, > that, and LCNC seemed not to be suffering because the machine was too > busy while I watched a news video or 3. > > I think I'll leave it that way. ;-) > > Cheers, Gene Heskett
However, i do see one point that could be troublesome. The Z turnaround at the bottom of the stroke. It has developed a backlash in the .00675" area, the source of which I haven't located yet but am suspecting the Z axis thrust bearing as its nut for that is not double nutted. I do have a limit3 in the spindle drive path intended to soften the stress on the motor, and I can further limit the ramp speed presented to the PID.S.command input with that, giving Z time to make its backlash move without losing a count. When this occurs, it does not seem to affect the end position of the upstroke, but has resulted in its moving relative to the soft limit, so that if the g33.1 peck is position 50 thou below the up soft limit, some time after it has made 20 pecks, each time hitting the home switch an indentical amount, but somehow the machine counts have been lost and it thinks it has hit the upper soft limit while still physically up to .1" below it. While I can slow the ramp in the ini file and have done so, this also expands the overtravel, so what I'd like to do is, just as the spindle reverses, I'd like to freeze the output of that limit3 for the few milliseconds it takes Z to accomplish its backlash takeup move. This is not directly doable for 2 reasons, first being that limit3 has no "freeze" input, effectively removing it from the servo-thread execute loop, And motion has no backlash move in progress output pin. I can probably cobble up something to generate a slight pause in the ramp at that reversal point, but it really seems like it should only be effective until the backlash move has been completed. Hints on developing that "backlash move in progress" signal from what we do have would be much appreciated. Thanks all. 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 [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
