Difficulties in probing

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12 Oct 2021 05:20 #222899 by Jflesburg
I'm brand new here and have been reading lots, and understanding some.  I built a plasma table, and have most of it set up.  I have linuxcnc set up, have done a couple of configurations starting with the Pncconf wizard.  I'm using (for better or worse) a mesa 7i96, I'm using an XXYZ configuration gantry.  I have limit switches on both ends X1, X2, and Y.  I have a home limit at the top of Z, and a float switch at the bottom of Z.  The machine moves, and homes.

I then followed the instructions to set up plasmac, after unsuccessfully attempting to integrate toma_thc into my earlier configurations.

Plasmac seems to work better for me so far, but I'm still missing some things. 
  • When I try to set up probing (following along in 5.2 of the manual), it mentions manually jogging z down until it stops at the Z axis MINIMUM_LIMIT, then click Touch Off with the z axis selected and 0 offset.  I don't have a Z axis MINIMUM_LIMIT switch.  Do I need one?
  • When I do the "Probe Test", I set the "Probe Height" until I just make the limit switch and it holds there, but it does not lift back up to "Pierce Height".  I've tried increasing the values of "Pierce Height" and also the "Float Travel", but so far it doesn't move up off the float switch.
Any and all suggestions would be helpful.

Thank you,

 

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12 Oct 2021 10:32 #222915 by snowgoer540
Replied by snowgoer540 on topic Difficulties in probing

I'm using (for better or worse) a mesa 7i96

I cant think of better hardware than Mesa, so I'd say it's for the better.

I then followed the instructions to set up plasmac, after unsuccessfully attempting to integrate toma_thc into my earlier configurations.

I think even Tommy would say toma_thc is pretty dated, it was "replaced" by PlasmaC, which has now been replaced by QtPlasmaC. PlasmaC certainly works, but it's not receiving any updates short of critical bug fixes.

When I try to set up probing (following along in 5.2 of the manual), it mentions manually jogging z down until it stops at the Z axis MINIMUM_LIMIT, then click Touch Off with the z axis selected and 0 offset.  I don't have a Z axis MINIMUM_LIMIT switch.  Do I need one?

Nope, if you have one at the top of travel, that's plenty. LinuxCNC will stop machine motion when it reaches the Min Limit provided that you have everything set right and it doesn't mechanically bottom out first. This is referred to as a "soft limit".

When I do the "Probe Test", I set the "Probe Height" until I just make the limit switch and it holds there, but it does not lift back up to "Pierce Height".  I've tried increasing the values of "Pierce Height" and also the "Float Travel", but so far it doesn't move up off the float switch.

Without pictures of your setup, seeing your config files, etc., it's difficult to say. However, you might benefit from checking out the diagram that was recently added to the following section of the QtPlasmaC user guide as it applies to PlasmaC as well.

linuxcnc.org/docs/devel/html/plasma/qtpl...tml#qt_initial-setup

The following verbiage was also added to make the purpose of the touch off more apparent:
To set the Z axis DRO relative to the Z axis MINIMUM_LIMIT, the user should perform the following steps. It is important to understand that in QtPlasmaC, touching off the Z axis DRO has no effect on the Z axis position while running a G-Code program. These steps simply allow the user to more easily set the probe height as after performing the steps, the displayed Z axis DRO value will be relative to Z axis MINIMUM_LIMIT.

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12 Oct 2021 17:51 #222955 by Jflesburg
Replied by Jflesburg on topic Difficulties in probing
Thanks for the reply and the picture. This morning, thinking about it and more reading the probing section 5.2, I ended up drawing just about the same diagram, but I included my HOME switch at the upper limit (z axis max in the diagram you referred to). I came to the conclusion that I need to check my lower limit so I don't run out of travel.

Currently, mine will travel downward, lift the floating head, trip the Float limit switch, and stops until it times out and raises to the starting point.

It would seem that several are migrating toward QTplasmaC. Should I be looking into changing to that?

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12 Oct 2021 23:16 #222987 by snowgoer540
Replied by snowgoer540 on topic Difficulties in probing

It would seem that several are migrating toward QTplasmaC. Should I be looking into changing to that?


I think so, but I am probably pretty biased. :)

I am not sure what distribution of Linux you're running, but it might also be a good time to change if you are running the regular buster distribution .iso.

I put together an installation guide that should make it pretty easy for you to have something a little easier to work with as well as walk you through the necessary steps: forum.linuxcnc.org/9-installing-linuxcnc...indows-users?start=0

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13 Oct 2021 02:28 #222994 by Jflesburg
Replied by Jflesburg on topic Difficulties in probing
I just recently installed it. It was the iso with Debian 10 and linuxcnc. I think I downloaded it in September. Linux is completely new to me. It feels a bit like learning DOS all over again.

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13 Oct 2021 05:17 #223000 by Jflesburg
Replied by Jflesburg on topic Difficulties in probing
I may have to give it a try. Not getting too far along, but I'm trying.

By altering velocities and accelerations, here is where it is at:

I have the soft limits set at -0 MIN, and 70 MAX
I have the probe height set to 53

With the z axis homed (approx 2mm off the limit), when I press "Probe Test" the z axis travels downward. Confirmed with the DRO, the float switch activates at 50.

When the float switch activates, the axis slows down presumably to the probe speed (50), and continues to travel down to 68. When the test times out, the z axis raises back up to the start height.

Reading the documentation, I thought this was supposed to probe down until the limit is actuated, lift back up by the "Float Travel" and then an additional "Pierce Height.

How is the probe sequence supposed to work?

I'm thinking that I might have the speeds set too low, but I'm not sure how to tell.

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13 Oct 2021 11:00 #223017 by tommylight
Replied by tommylight on topic Difficulties in probing
Not sure what is going on but when the float switch trips the torch/probe should stop and move up, not down?????

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13 Oct 2021 12:03 #223019 by snowgoer540
Replied by snowgoer540 on topic Difficulties in probing
It may be easier for us to help you with some video of what’s going on.  

It may also be helpful if you posted a backup of your config.

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13 Oct 2021 15:53 #223031 by tommylight
Replied by tommylight on topic Difficulties in probing
The float switch is not wired properly/not in the input set in hal/not properly connected in hal !
Check the float LED on screen while moving the torch by hand up and down, it should go on and off, i bet it is not.

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13 Oct 2021 19:26 #223036 by Jflesburg
Replied by Jflesburg on topic Difficulties in probing
Yes, the input light on the 7i96 comes on, as does the yellow indicator on screen.

I thought it would be green on screen, but it and the torch on indicators on screen show up yellow when the input or the output is on.

I’ll post a backup of my config when I get home from work.

Thanks for the replies.

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