Modify gcode to suit plasma cutting

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07 Oct 2020 16:04 #185266 by raggielyle@gmail.com
hi There,
This is my first post so please forgive if I've not followed protocol.
I am using QCad with dfx2gcode to generate gcode from dxf files.
Unfortunately, dfx2gcode does not cater for plasma cutting.
I have therefore developed a Bash script to modify the gcode files generated with dfx2gcode to make them suitable for plasma cutting.
The program sets the values for feed rates, safe height for rapids, cut height, probing, pierce height and pierce delay. Default values can be changed for easier usage.
I'd like to make the program available for those out there looking for a solution to create plasma suitable gcode from dxf files without going to the expense of buying software.
Sorry but I'm new to this so please would somebody tell me how to go about this.
This forum has been a great help to me so here's my contribution in return.
Thank you.
Kind regards
Bruce
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07 Oct 2020 16:09 #185268 by AgentWD40
First of all thanks you very much for your contribution.

Are you familiar with the PlasmaC component in linuxcnc? Is this intended to work in conjunction with it or in place of it? I ask because the settings you mentioned are what PlasmaC is intended to handle.

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08 Oct 2020 07:15 #185334 by raggielyle@gmail.com
Thanks for your response.
I'm embarrassed to say that I did not know about the PlasmaC component. I'll certainly investigate.
kind regards
Bruce

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08 Oct 2020 10:49 #185345 by raggielyle@gmail.com
Thank you for your pointing me towards PlasmaC.
I’m a hobbyist and am using the “stand alone” torch height controller by Proma. It works well but with one caveat – there is no way to stop the torch from diving when it things slow down for small shapes. My gantry is aluminium so I’ve got good acceleration and one can always adjust the settings to mitigate the problem so this is not too much of a concern for me. I’ll admit that this is not the best solution but its fine for us small time guys!
Do you feel that there's merit in my making further improvements available?
My table is multi-purpose for milling, plotting, laser etc so to change to PlasmaC will be a huge mission so I’ll give it a miss. I've just completed another table to do cake and biscuit icing/frosting by pneumatic extrustion. Great fun!
Thanks again to everybody for such great software.
Kind regards
Bruce

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08 Oct 2020 14:14 - 08 Oct 2020 14:18 #185357 by AgentWD40
PlasmaC has been under active development over the past year (or two?), I'd say check it out.

I haven't used the Proma, but you can definitely use it with PlasmaC. The Mesa THCAD is very popular for THC and fully integrates with PlasmaC to let linuxCNC handle height control. It's relatively low cost too. Because it's fully integrated it's smart enough to avoid those dives you're talking about and temporarily disable THC on small radius/low speed cuts. I don't know if that's possible with the proma, does it have a disable pin/signal? There are dozens of more knowledgeable folks on the forum that can tell you all about it, hopefully someone will see this and chime in.

Regarding the multipurpose table, you can just use a different linuxcnc config when milling or plotting. To setup the PlasmaC component all you need to do is get a basic working linuxcnc config, like for milling, then run that basic configuration through a tool called the configurator and it will add the necessary config files/settings to get plasmac setup for you, it's really not a huge mission. The PlasmaC user guide will walk you through it and there's tones of help here on the forum.

Do you feel that there's merit in my making further improvements available?

There's always room for improvement! But you may want to make sure you aren't reinventing the wheel.
Last edit: 08 Oct 2020 14:18 by AgentWD40.

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08 Oct 2020 14:19 #185359 by tommylight
Proma THC150 = works with PlasmaC or thc_toma configs
Proma THC SD = overtakes the step/dir Z axis control and does require just a simple 3 axis config.

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09 Oct 2020 07:01 #185434 by raggielyle@gmail.com
Tommylight is correct but I'll nevertheless contact Proma to see if there's a way around the problem. It's a polish company and their communication is not the best.]
I'll continue to make improvements available because there will be others out there with the Proma SD "stand alone" version.
Thank you both for your kind help.
Kind regards
Bruce

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09 Oct 2020 07:19 #185437 by raggielyle@gmail.com
Do you think it would be possible to temporarily disable the Proma SD signals for the z axis by disconnecting the ground wire by means of an external relay (normally closed) triggered through the the 0-10v spindle speed output on my cheap Chinese bob using M4?

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09 Oct 2020 08:25 #185443 by tommylight
If you disconnect the ground wire while the plasma is on the Z axis will start vibrating violently and risk destroying the Z axis drive as that would leave the drive inputs open to interference.
It might be better to use the step and dir outputs from the Proma SD as encoder counter, something like :
Z axis wired to BOB not to PromaSD, PromaSD step and dir outputs to BOB inputs, use step pin as encoder pin in hal, use dir pin to change the counting up or down in hal.
A simpler or more complicated version ( depending on how good you are with electronics ), is to use two XOR (7486) and two FLIPFLOPS to have the step dir signals converted to up down.
Also using a charge pump for the step pin should work, again using the dir pin to change the direction up or down.

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12 Oct 2020 06:30 #185800 by raggielyle@gmail.com
Thank you Tommylight. I'll have to give the matter some thought and will et back once I've done so.
Regards
Bruce

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