Fast probing not so fast.

I finally got around to upgrading to the latest Plasmac version (0.177) a week ago and have given it a good workout since cutting 4 sheets of material. I had issues today so I recompiled from 2.8 branch today but subsequently realised I should also have done a plasmac upgrade but the version history does not seem to say anything has changed about probing.

So the probing always started from Max Z height and while having a probe height set, It always went to top of travel on every probe. I was not able to change this. So when I threw a nest of some 1200 + pierces at it, the run time was certainly quite a bit longer.
So:
What is expected behaviour?
How do we keep the start of probing low?
How do we speed things up?

I did get a crazy loop at one stage with unstoppable up/down motion on the Z axis that could not be stopped without forcibly terminating Linuxcnc but I can't recall the exact specifics leading up to it so will wait until I upgrade to the latest Plasmac version before worrying about it.

rodw wrote:

So the probing always started from Max Z height and while having a probe height set, It always went to top of travel on every probe. I was not able to change this. So when I threw a nest of some 1200 + pierces at it, the run time was certainly quite a bit longer.
So:
What is expected behaviour?

The first probe on a job starts from where the Z axis currently is, it alway has.
It moves at Setup Speed to Probe Height.
It then moves at Probe Speed until is senses the material.
If it detects material before reaching Probe Height it then backs off a fraction and reprobes at Probe Speed.
After a cut Z moves to Safe Height, then X/Y move to new cut and probe begins at safe height.
Rinse and repeat

How do we keep the start of probing low?

Start the job with Z low and set your Safe Height low.

How do we speed things up?

What things?

phillc54 wrote:

After a cut Z moves to Safe Height, then X/Y move to new cut and probe begins at safe height.

That was not what we were experiencing. It always went to max Z. I'll review when next on site.

Well it definitely works here.

Ok, I finally worked this out. Previously my probe height must have been at or below the material height.

My Recommendation for fastest cycle time.
Assuming you have a float switch slide that can soak up overtravel, set your probe height at or just above the material height. Ideally set the probe speed at or near the maximum velocity of your Z axis.

With some testing, set it so that there is minimum (preferably no) overtravel on the float switch. You basically want to get to probe height as fast as possible and then enter the probing cycle with the torch almost kissing the material.

If you get some material warpage, let plasmac sort it out.. You may need to adjust the probe height if warpage is excessive.

Happy now!