Z axis height at end of cut

rodw wrote:

Why do we have two different conditions/methods?

Why not.
No, there is a reason, some folk don't have enough float movement to account for overrun if they probe at Setup Speed.

Which is faster the one triggered above probe height or the one where probe height is reached?

I haven't done any proper timing but for most cases it appears that 'fast' probing is quicker. It would really depend on what the relationship is between Probe Height and the top of the material. Probe Speed would also come into play.


This may show 'fast' probing better.

2 things
1 did you ever use that machine as it is way to clean
2 why does yours retract so fast, mine takes nearly 6 seconds ?????

That red light goes on when the switch is tripped and off when released, 5.5 seconds.

tommylight wrote:

2 things
1 did you ever use that machine as it is way to clean

Nowhere near as much as I would like, I seem to spend a lot of my typing fighting with a keyboard.

2 why does yours retract so fast, mine takes nearly 6 seconds ?????
That red light goes on when the switch is tripped and off when released, 5.5 seconds.

That is something I don't understand as well, the retraction time should only be long enough to cover the switch hysteresis.

This is my switch arrangement.

Same thing, just mine is a bit shorter on the move !
forum.linuxcnc.org/show-your-stuff/38547...uild?start=60#167665
Beginning to think you are doing this on purpose to me in retaliation for building a faster machine than yours !
Did some tests today regarding probing speed, so i set the probe height to 50mm, probe speed to 2000mm/m and that improved the overall results of cutting that complicated drawing twice by nearly 6 %. Will do a test tomorrow at 1m/m and report the results.

tommylight wrote:

Same thing, just mine is a bit shorter on the move !
Beginning to think you are doing this on purpose to me in retaliation for building a faster machine than yours !

Damn, you caught me out.

Yeah, same principle, strange. What is the accelleration of your Z axis and you were probing at 40000mm/min for the slow retract?

Z accel is at 1000mm/s/s and yes i was probing at 4m/m.

phillc54 wrote:

....... and you were probing at 40000mm/min for the slow retract?

Nooooo
Just saw that, nah i newer tested the Z axis over 12m/m, but since it has a drive powered by 45V and a 8mm pitch lead-screw, i bet it can do twice that easily, maybe more.

By my calculations...

If you had Setup Speed at 4000 (mm/min) and Probe Speed 400 (mm/min) and Probe Height below the top of material then it would move down at 4000, sense the material then overun by 2.22mm. It would take 222mS to retract the overun then XmS to retract the switch hysteresis then it would probe down at 400 and overun by 0.022mm. It would take 22.2mS to retract the overrun then XmS to retract the hysteresis. Then it would move to Pierce Height at 4000.
Total retract time = 244.2mS + hysteresis time

If you had Setup Speed at 4000 (mm/min) and Probe Speed 4000 (mm/min) and Probe Height above the top of material then it would move down at 4000, reach probe height then probe down at 4000, sense the material then overun by 2.22mm. It would take 2222mS to retract the overun then XmS to retract the switch hysteresis then it would move to Pierce Height at 4000.
Total retract time = 2222mS + hysteresis time

I hope that make sense.

EDIT: I guess I should ask what version of PlasmaC you are using.

I have been confused about probing since day one.