Do we need a Plasma Touch Off HAL component ?

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01 Feb 2018 05:58 #105268 by rodw
No I have not yet. But I have done a lot of thinking about plasma cutters!

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01 Feb 2018 06:06 #105270 by grijalvap
Nice
Maybe you can share these ideas, I'm working on a new plasma table, and I want to make it as good as possible, do you know if there is any Modbus component to communicate with the Hypertherm powermax85
I'm using mesa 7i25+ 7i65 card.
thanks.

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01 Feb 2018 06:37 #105273 by rodw
I saw your question on the other thread but thought PCW would be better qualified to answer. I think you will need a different bit file to talk to the Mesa UART. I don't believe anybody has used this approach and using mesa UART seems to be the best way as the communications part is done, just not the MODBUS protocol. There are some modbus emulators so my plan was to use that to see if I could talk to a yet to be purchased Hypertherm using one of these emulators and replicate the examples in the Hypertherm documentation. Once that was done, I was going to use the emulator to connect to the Mesa card

With that in mind I purchased a 4 wire USB to RS485/RS422 interface from ebay which cost about $12 but I've not played with it at all.

I think though you will be pretty much on your own. Andy wrote the code and somebody used it so there is some example code somewhere.

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01 Feb 2018 14:42 #105282 by tommylight
I have been following this since the begining, and i think i already pointed the fact that a touchoff HAL exists in linuxcnc and functions properly as proven by several plasma cutters using it on daily basis for production work.
It is not a comp file, it is a magnificent piece of hal code writen by whoever made the THC300 configuration, with every function needed for touchoff implemented in hal. It does not use any ngc file for touch off, it needs just an M3 command and does the rest flawlesly, namely: move the torch down until it finds the material and trips the floating switch, moves the torch up to an adjustable height set on the right side pannel, fires the torch and waits for the ArcOK signal, delays motion for an adjustable time set on the delay pannel, moves the torch down to cut height after the delay expires, starts motion and takes control of Z axis movement for corrections during cutting. If the cuting proces is interupted it will stop the torch and move torch up to an adjustable height set on the pannel as rapid height. It will stop movement and torch if the floating switch is tripped during cutting.
There is also a version that has adjustable voltage and feedback, i think it was named VLCDTHC, it is also on this forum.
From my point of view, it has everything needed for operating a plasma cutter, as far as touchoff goes, without the need af adding any gcode and works perfectly with gcode output from inkscape. Been using it for several years on several machines.
About a year ago i started to modify said code to work with servo motors and loop closed in linuxcnc ( PID loop anyone? ), but due to time restrictions never got ot finish it.
There is also a PDF file for the THC300 config with everything visualised and full functioning diagram so it can be used to implement that functionality into a comp file, if someone has the time to do so.
It also has setable firing retry in case it missfires.
I am sorry for not doing that myself, but i am pressed for time so much so that i can barely get 4 to 5 hours of sleep.
With utmost respect,
Tom.

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