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Author Topic: Mach3 Plasma Z axis move after firing torch M03  (Read 1544 times)

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Mach3 Plasma Z axis move after firing torch M03
« on: February 16, 2022, 04:58:04 AM »
Hi all,

We have a self built plasma cutter. It uses a PoKeys57CNC Ethernet controller as well as their PlasmaSens unit for THC. We are using a Hypertherm Powermax 45XP source. I'm creating the toolpaths in Fusion360.
Today I was tweaking our machine and noticed that the machine seems to ignore a Z move after firing the torch, below is the sequence that I noted:
  • Z probe executes.
  • Moves to piece height and fires the torch.
  • Waits for the pierce delay, but skips the Z movement to cut height of 1.5mm.
  • Machine begins X,Y movements from pierce height and does not first lower to cut height, the height is corrected after moving around 5mm, I assume from the THC input.
When I dry run the machine with THC disabled it functions as expected. If I dry run the machine with THC enabled then it pauses at the M03 command. If I toggle the Torch ON/OFF button it continues and lowers the Z as expected.

Here is a snippet of the G-Code. If you are wondering why there is a 1 second delay before probing we were having issues that the Z axis would frequently move up instead of down when the probe command was executed. Not sure if it is EMF from the motors stopping suddenly, but the 1 second delay solved it.

Code: [Select]
G90
G71

(2D Profile2)
G0 X72.53 Y82.5
G4 P1.
G31 Z-100. F500.
G92 Z-1.7
G0 Z17.3
G0 Z3.8
M3
G4 P1.
G1 Z1.5 F4000.
G1 X68.2 Y80.
G3 X91.8 I11.8 J0.
G3 X68.2 I-11.8 J0.
G1 X72.53 Y77.5
M5

I'm not sure if the THC is somehow interfering with the instructed Z movement once the torch has been fired, not sure how to get around this. I also noticed that I can't really change the Z feedrate without using the 'Lead in' and 'Lead out' feedrates in Fusion360. This also affects the short distance when entering the cut and not the Z movements alone.
Thank you for any help in advance and hopefully I am posting this in the correct section!

Re: Mach3 Plasma Z axis move after firing torch M03
« Reply #1 on: February 21, 2022, 08:24:32 AM »
I'm going to try using StartTHC() in M666 and EndTHC in M667 to see if it will do the Z moves. I have added M667 just after M3 and then M666 after the Z move to the cut height. Will update once I've cut something.
Re: Mach3 Plasma Z axis move after firing torch M03
« Reply #2 on: February 23, 2022, 12:04:54 AM »
Adding the StartTHC() and EndTHC() seems to work for allowing the machine to first move to cut height before THC is active