PCNC770 4th Axis w/ Clear Path Servo & PathPilot

We slapped a giant Clear Path Servo from Technik on the 4th axis of our PCNC770. All was well while under Mach3 control but with the path pilot upgrade I can't seem to make the deceleration work quite right with interpolated moves and it's causing our 4th axis work to come out twisted. See video for details. Anyone have any idea what parameters I need to tweak? I'm not familiar with LinuxCNC or PathPilot yet so this one has me stumped.



also have a thread over at CNC Zone. you can see what I've already tried in this link.

http://http://www.cnczone.com/forums/tormach-personal-cnc-mill/309278-pcnc770-4th-axis-clear-path-servo-pathpilot.html#post1891948

Since the video was take we have set P = 50 and max_error=0 that has the decell issue solved but we are still getting twisted part.

thanks in advance,

charlie

The PID is used to make the step generation more insensitive to real-time thread jitter.

Do you know what the servo-thread period is in that setup? I would assume a 2kHz serv-thread if the PGAIN is 500.

Given that this is a servo motor being sent position commands by step-dir I would be very tempted to remove the PID from that axis.
ie, connect axis.3.motor-position-cmd directly to the stepgen (this would be in the HAL file).

I was thinking it might be something related to the PID as there is already an encoder and controller built in to the clearpath system. i'll see if I can't figure out how to work the HAL file changes. (total noob when it comes to linuxcnc)

Why dont you try setting the ferror limits to something reasonable first as I suggested in the CNCZone thread
This will tell you if you have a following problem or theres something else like Gcode differences, step polarity issues so steps are lost on reversals etc etc

i'll try that. hadn't been back over to CNC Zone to see your reply yet. but honestly I haven't changed the ferror values those are stock tormach numbers. i'll check the CNC Zone thread now and test it out.

alright ran the settings you specified over at cnc zone

looks like I am getting a following error on joint 3 as soon as the axis starts to spin I've attached my .ini and .hal files.

The thread order in the hal file is wrong

addf hm2_5i25.0.write servo-thread

should be the last thing done (so the last addf)

moved that line to the end of the servo thread. will run and report back.

by the way, not sure it I said this yet but, thanks for all the help.

no bueno. updated the .hal file, still get a joint following error as soon as the a axis starts to rotate. this is still using this pid tuning set up

I would now try setting the max_error to 0