Plasma THC preset voltage

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nbenezan
Posts: 3
Joined: Sat Apr 17, 2021 1:35 pm

Plasma THC preset voltage

Post by nbenezan »

The Jet Tool dialog lets me set the feedrate, pierce delay, height and cut height. But where can I enter the preset voltage for the THC? Somebody has sent me a screenshot which looks like Sheetcam and includes a voltage input field. Is there some secret option somewhere which enables this feature? I can't find it.
Sheetcam-Voltage.jpg
Sheetcam-Voltage.jpg (86.13 KiB) Viewed 2105 times
If it's not possible to specify a voltage the I could probably modify the post processor so that if the cut height is >10 then it's interpreted as voltage and if it's <10 it's the actual height in mm. But that's probably more confusing than neccessary.
robertspark
Posts: 257
Joined: Thu Feb 26, 2015 12:11 am

Re: Plasma THC preset voltage

Post by robertspark »

what are you going to use the thc voltage for within the gcode?

go and have a look at the CandCNC postprocessor as it stores the thc voltage (and uses it too), and other settings for the rs485 interface

I keep the voltage settings in mine but I have always used them to set the voltage via miscellaneous (m) codes.... otherwise there is no point.
nbenezan
Posts: 3
Joined: Sat Apr 17, 2021 1:35 pm

Re: Plasma THC preset voltage

Post by nbenezan »

I don't know exactly what you mean. How does the THC know what so set as nominal voltage if it's not specified in the G-code? I know there is an "auto volts" option in LinuxCNC. It samples the actual voltage after moving Z down to cut height and after the first acceleration ramp of X/Y and takes that sample as nominal voltage. But I'm not using LinuxCNC.

But the hint to look at the CandCNC postprocessor was helpful.

Code: Select all

post.DefineCustomToolParam("PlasmaTool", "Preset volts", "presetVolts", sc.unit0DECPLACE, 49, 0, 200)
seems to extend the list of tool parameters. Interesting that Sheetcam parses the postprocessor and adjusts it's GUI accordingly as that is not mentioned anywhere in the documentation.
mancavedweller
Posts: 161
Joined: Tue Feb 25, 2014 6:53 am

Re: Plasma THC preset voltage

Post by mancavedweller »

nbenezan wrote: Mon Apr 19, 2021 9:12 am But I'm not using LinuxCNC.
What system are you using. I haven't noticed you specify that yet.
mancavedweller
Posts: 161
Joined: Tue Feb 25, 2014 6:53 am

Re: Plasma THC preset voltage

Post by mancavedweller »

nbenezan wrote: Mon Apr 19, 2021 9:12 am How does the THC know what so set as nominal voltage if it's not specified in the G-code?
Depends on the type of THC. Many THCs are completely external to the controller (Mach3, etc) and thus the voltage is set on the THC itself.

Some THCs are built into the controller and you can set on the screen. Whether you can also set via gcode I don't know, you'd have to read the documentation for your individual system.

I had an external THC but with communication to the controller, so I would set the THC parameters on screen and the controller would send that info to the external THC.

So do you not have any documentation for your system explaining how to use the THC ?
robertspark
Posts: 257
Joined: Thu Feb 26, 2015 12:11 am

Re: Plasma THC preset voltage

Post by robertspark »

mancavedweller wrote: Mon Apr 19, 2021 10:00 pm
nbenezan wrote: Mon Apr 19, 2021 9:12 am But I'm not using LinuxCNC.
What system are you using. I haven't noticed you specify that yet.
I just gave you an example of a working post processor file that I know had a lot of other features built into it that most will not need.

THC voltage is not really something that the CNC machine NEEDS to know, it is normally (most of the time) just set on the front of the THC unless you have and advanced THC then you will need to please provide a bit more information (manufacturer & model & link)
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djreiswig
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Location: SE Nebraska

Re: Plasma THC preset voltage

Post by djreiswig »

You can make SheetCam ask for the thc voltage, and output it in the gcode. The important part of the equation is that you need to have a controller that knows what to do with the setting in the gcode. Just having it in the gcode won't do anything.
nbenezan
Posts: 3
Joined: Sat Apr 17, 2021 1:35 pm

Re: Plasma THC preset voltage

Post by nbenezan »

mancavedweller wrote: Mon Apr 19, 2021 10:00 pm What system are you using. I haven't noticed you specify that yet.
Hehe, I haven't specified that, because it doesn't exist, yet. :mrgreen: I'm building it myself. And I don't want to copy something that has more historical reasons (Mach3 can't do it internally) but make it as easy and convenient as possible for the operator. The THC will be integrated into the motion controller. That has the advantage that it can switch any time from Z coordinate driven motion to voltage controlled THC mode and back and always display both values on the PC screen.

I think the best way would be to use the auto-volts sampling for the first time so you don't have to guess a starting value for the voltage. But I wouldn't use auto sampling all the time but instead remember the first voltage sample and use it for all further cuts while allowing the user to fine adjust it with the override wheel.

So yes, after all I agree that it's not neccessary to set a voltage in the G-code or in sheetcam. (unless you have an external THC that communicates with the PC)
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