Some thoughts and some findings using PlasmaC

phillc54 wrote: Tom is it possible that the material buckled up enough so the the top of the material was above the Probe Height. Remember that Probe Height is measured from the MIN_LIMIT rather than the material.

Yes, yes it was as i had just changed the Z axis limits but was still using old heights.

DenkBrettl wrote:

Franklin wrote: One more note for pierce/cut mode. When in the Gcode is present the spotting function and turn on the "Pierce only" mode the plasmac makes piercing instead of spotting.
It would be great to ignore spotting when "Pierce only" mode.

I had exactly the same problem today. So I fixed it

My fork can be found here: github.com/DenkBrettl/linuxcnc - I've opened a pull request as well.

Klaus

Thanks for the contribution, it looks good and has been merged.

Home work :
-Do some cutting of whatever
-during cutting trigger a limit switch
-press F2 and resume by using "run from here"
=Result=
-probing will ignore probe speed
-torch will move to high hitting the limit switch at the end of the cut, not always
-THC will not follow the material properly usually lowering the torch to much---subjective/not confirmed !!

Please let me know if anyone else can reproduce this.
Thank you.
Last 2 days did some cutting on 3mm mild steel plate with 386 probe/pierce per 2x1m plate, 6 plates total so the issue of Z axis moving past limit was still there at 3m/m setup speed, but it was bearable, roughly once per 100 cuts.

Tommy,

I will try to reproduce in the next day or two. One question I had... are you on the latest version? I had a similar issue and I thought I was on the latest version but was not :blush:... I hadn't seen it again after updating (doesn't mean it's not there).. but just wanted to make sure we are all on the same sheet of music.

I have been trying on a sim but don't see the issue. I tripped joint0 and joint3 limits and both seemed to behave ok.

Definitely can reproduce it on my machine (haven't tried on sim).

It's exactly like Tommy described, but I would add some detail as to how I got it to hose up:

Start program
After first probe, trip a limit switch (I've been doing Joint_2 (the Y next to me as I can put metal in front of it easily)
F2
Click G0 positional move before M3 command and do Run From Here
Let the torch probe again, let it go until after it probes the next M3 command
When it starts cutting, stop it
Restart the program
Let it probe and start to cut
Press stop

At this point I got a Joint_3 following error, my table sounds like Z ran into a hard stop (just a terribly sudden Z move command I am guessing with no acceleration). Everything past that caused Z to behave badly. I ran the torch to near the top, but the next time I pressed cycle start, it slow probed from the top to the metal and at the next retract ran UP into the hard stop and crashed (and gives me a joint on limit switch error). Since I had to manually move the Z off the limit, I had to restart linuxcnc (or rehome) to keep going.

Another note, I got it to do this 2 times. Once as above, and another that just gave me a joint following error and did not crash after that.

Things to note:

1. I think this is highlighting that there is still something going on with the Z offsets and movement timing. At times, Z movements from when under the control of PlasmaC are still causing Joint_3 (Z) following errors, it sounds as though the acceleration is not accounted for. Like it's commanding too big a move too fast.
2. From what I see of what Tommy described, he's using bad practice. The user shouldn't start a program with the torch so far down (almost touching the material) near the soft limit (I'm guessing). It would be better practice to jog the torch near the top before doing "run from here" to recover from an error of this magnitude (Phill, please correct me if I am wrong). I am guessing this happens because he is starting the program near the lower soft limit. I suspect I've not seen this error because I added a Z movement to my XY zero button and I try to start 5mm from the top (per the user guide ).