Pierce height would exceed Z axis maximum safe height condition found while...

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27 Apr 2022 06:42 #241354 by Daddio
Good evening,

I am running QtPlasmaC 2.9.0.

I have been banging my head on this Operator Error with no luck and hope you all can help:
  
pierce height would exceed Z axis maximum safe height condition found while float switch probing

Attached is my INI file..

This error pops up every time on the first probe of a cycle start, including imperial_wrench.ngc.  This all started after I added a top of Z home switch so I can properly home the Z axis. 
I am, however, able to home seemingly fine. The torch runs to top (+Z direction) taps the switch and backs off according to home offset and home, in the ini, and displays the -0.375 in DRO box which is the HOME value in joint 3. 
I then load a program, set my G54, and hit cycle start and the first move is to just below Z MAX, which it should based on the gcode. But what seems odd is that the Probe Height now seems skewed up from the move it just made to a little below Z MAX.  Additionally, probing does not work if it is not started from the Home position.  If I move Z down, and do a probe test, the torch runs into the material at full speed which then throws this error:

pierce height would exceed Z axis maximum limit condition found while moving to probe height during float switch probe testing

What does that mean?  The torch is touching the material well away from the Z axis maximum limit switch (which is my Z home switch).

In a  nutshell, the problem seems to be that after cycle start the torch begins its probe routine, the probing height is now skewed, it contacts the material, the float switch is seen in Halshow and the LED on the main screen, it then pauses the program and pulls up and throws the first operator above.  What am I missing?

 
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27 Apr 2022 06:59 - 27 Apr 2022 07:02 #241355 by phillc54
What are the settings for Pierce Height and Probe Height?
If you jog Z down until it hits the limit, how far below the top of the slats is the torch tip?
What is the thickness of the sheet you are probing.

This should be 0.5 but I don't think that it would cause any probing issues.
[AXIS_Z]OFFSET_AV_RATIO = 0.75

Edit: you also have [JOINT_3]MAX_LIMIT = 0.25 and [AXIS_Z]MAX_LIMIT = -0.25
Last edit: 27 Apr 2022 07:02 by phillc54.

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27 Apr 2022 07:13 #241356 by Daddio
Pierce height: 0.120"
Probe height: 1.0"
I've tried a variety of heights with no joy.

Jogging z down to min Lim the tip goes about 0.25" below the slats. I'm trying to cut 3/16" plate.

I've tried both positive and negative without success for [JOINT_3]MAX_LIMIT = 0.25 and [AXIS_Z]MAX_LIMIT = -0.25.

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27 Apr 2022 07:17 - 27 Apr 2022 07:18 #241357 by phillc54
Weird, can you post a backup of your config, there is a backup button on the parameters or settings tab.

Is the behaviour the same for a gcode probe and a probe test.

I've tried both positive and negative without success for [JOINT_3]MAX_LIMIT = 0.25 and [AXIS_Z]MAX_LIMIT = -0.25.

They need to be the same and they need to suit your machine
Last edit: 27 Apr 2022 07:18 by phillc54.

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27 Apr 2022 15:34 #241382 by Daddio
Backup config attached..
I made  [JOINT_3]MAX_LIMIT = -0.25 and [AXIS_Z]MAX_LIMIT = -0.25 , ran it and got the same error.  How do I run a gcode probe command from MDI? 
The in-program probing looks the same except it's probe height is skewed based on Z MAX.  Because of this skew I had to reduce MAX_LIMIT to -0.25 so the torch tip could actually get to the material.   Shouldn't I be able to probe from any height and have the torch return to its initial probing start point after it touches off the material?  What would cause probing to be limited to only its home positions?
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28 Apr 2022 02:23 #241425 by phillc54
I made a sim from your config and everything works as it should with the settings that you have.
Probe test needed more time added as it runs out of time due to the very slow Setup Speed you have in the parameters. Increasing the Setup Speed also fixes that.
I had zero issues with probing from a gcode file, I used the imperial wrench from the sample gcodes.
You still need to change OFFSET_AV_RATIO = 0.75 to OFFSET_AV_RATIO = 0.50 as it incorrectly reports the maximum setup speed allowed.

How do I run a gcode probe command from MDI?

Probing cannot be run from code, only from a Probe Test or a running cut file.

Shouldn't I be able to probe from any height and have the torch return to its initial probing start point after it touches off the material?

For a probe test yes, it will wait at Pierce Height until the timer finishes then it will move to the starting Z height.
For a probe during a cut it will always start at Z Max minus 5mm (0.197")
It does both of these correctly in the sim.

Have you set up the Z axis so it conforms to the following (you can disregard the -L and +L switches as you don't use them):
linuxcnc.org/docs/devel/html/config/ini-...witch_example_layout
linuxcnc.org/docs/devel/html/plasma/qtpl...tml#qt_initial-setup

 

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28 Apr 2022 06:20 #241435 by Daddio
Speeding up the probe and tweaking the limits has moved me past the "pierce height would exceed Z axis maximum safe height.." error and I'm now able to dry run the imperial wrench - thank you.

There seem to be a few issues remaining:
1. When it probes in-program I have it move quickly down to probe height, it then finds the material, but then very very slowly moves back up to pierce height. Is there a way to speed up the movement from when it finds the float switch to when it settles at pierce height?

2. It now keeps throwing a "safe traverse height has been reduced to 0.30in" error. I tried increasing Float Travel to clear this error, but if I increase it too much it reverts back to throwing the "pierce height would exceed z axis maximum.." error.

3. In between cuts the torch only moves up slightly to rapid over to the next start of cut rather than pulling up to the Safe Height.

On the Homing Configuration page in section 4. Shared Limit/Home Switch Example Layout, the picture shows the homing routine happening on the Z- end of travel, and since a top-of-Z-axis home switch is on the Z+ end of travel, does that diagram still work? I guess I'm still a bit confused on how to set up a top-of-Z home switch.

Current INI limits:
MIN_LIMIT = -6.0
MAX_LIMIT = 0.501
HOME = -0.750
HOME_OFFSET = 0.501

And THANK YOU!

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28 Apr 2022 06:53 - 28 Apr 2022 06:54 #241438 by phillc54

When it probes in-program I have it move quickly down to probe height, it then finds the material, but then very very slowly moves back up to pierce height. Is there a way to speed up the movement from when it finds the float switch to when it settles at pierce height?

When it senses the material it will back off at a slow rate until it no longer senses the material, this is the top of material setting, then it will move at Setup Speed (Parameters Tab) to Pierce Height. If you have a large hysteresis on the float switch then it could take quite a while. The slower the backoff the more accurate the top of material height will be. The best option is to reduce the hysteresis, a workaround is to change the probe final speed value.
linuxcnc.org/docs/devel/html/plasma/qtplasmac.html#qt_probing

It now keeps throwing a "safe traverse height has been reduced to 0.30in" error. I tried increasing Float Travel to clear this error, but if I increase it too much it reverts back to throwing the "pierce height would exceed z axis maximum.." error.

Float Travel is used to set the correct Pierce Height after a Probe Test as described in the second lot of numbered steps (1~10) here:
linuxcnc.org/docs/devel/html/plasma/qtpl...tml#qt_initial-setup

Once set to the correct position it should never need changing.

In between cuts the torch only moves up slightly to rapid over to the next start of cut rather than pulling up to the Safe Height.

I think you should run through the above steps and then see were this is at.

MIN_LIMIT = -6.0
MAX_LIMIT = 0.501
HOME = -0.750
HOME_OFFSET = 0.501

HOME_OFFSET is the switch position so when your machine homes it moves up to the switch then moves down 0.249" to the HOME position. If you jog down after homing and the torch tip goes just below the top of the slats then all is good.[/quote]
Last edit: 28 Apr 2022 06:54 by phillc54.

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01 May 2022 09:47 #241782 by RNJFAB
I wonder if its the same issues I was having Phil? 

Check the Hal/Ini files.

From my thread. 
forum.linuxcnc.org/show-your-stuff/42411...cnc?start=230#237060 
The following user(s) said Thank You: phillc54, Daddio

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01 May 2022 09:55 #241783 by phillc54

I wonder if its the same issues I was having Phil? 


Good find, I totally missed it...

The current hal file:
addf db_arc-ok    servo-thread

# ---JOINT ASSOCIATED WITH THE Z AXIS---

# ---PLASMA INPUTS---
# ---all modes---
net plasmac:float-switch   => db_float.in

It should be:
addf db_arc-ok    servo-thread

# ---JOINT ASSOCIATED WITH THE Z AXIS---
net plasmac:axis-position joint.3.pos-fb => plasmac.axis-z-position

# ---PLASMA INPUTS---
# ---all modes---
net plasmac:float-switch   => db_float.in
The following user(s) said Thank You: RNJFAB, Daddio

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