True floating head control?

[JerryP]

I have a Langmuir crossfire, and really like it, but I want to add a torch height control, and not sure what to look for.
What I want is a stand-alone that simply floats the torch at a constant height.
I do not need probe, pierce etc... just want it float about 1/8” or so above the sheet.
I do not want to hook it into the Z axis. What I want would be a simply on/off switch, independent of the crossfire itself.
Other than a linear rail to mount the torch head to, I am not sure what I would need. Something to constantly measure the distance, and I guess a stepper motor, and some sort of circuit board run whatever it is I measure to get the floating height.
When turned on, it would start floating at the set distance, and simply do that until turned off

[Rodw]

I do not need probe, pierce etc... just want it float about 1/8” or so above the sheet.

Herein lies your problem. You need to probe to the surface to set that 1/8" height at the start of your cut.
There are 100% stand alone controllers that control everything and you set those heights in their independent control panel. Have a look at the Robot3t or the Proma SD. But you will still need to probe to find the surface... so you can set that cut height.

The most cost effective method to control torch height is to use torch voltage as a process control variable as there is a near perfect linear relationship between the voltage and torch height as this plot I did of 16,000 readings demonstrates (cut height in mm).


There is more background info about plasma here http://linuxcnc.org/docs/devel/html/pla ... rimer.html

So in summary, that circuit board you are looking for is called a THC

[acourtjester]

Rodw is correct with the THC but do your research before putting your money down. Google your table to see if other have modified their with what you want. I know either here or weldingweb site there is info about this.
The other thing is the Proma SD many seem to have problems with them, again research (Google fo info)

[JerryP]

Thanks guys. Very much appreciate the info.
You cleared up a lot for me
I am new to CNC and it is daunting trying to learn everything.
I can do my own designs start to finish now, but the electronics end of it is a lot to learn.

[acourtjester]

the membership is very wide so ask questions most likely a member will be able to answer, just be clear with your info to help getting an answer.

[Rodw]

Rodw is correct with the THC but do your research before putting your money down. (Google for info)

Absolutely. I've never bought a THC in my life. I leave that to Linuxcnc which makes the concept of an external THC obsolete.

[robertspark]

i personally don't think that a crossfire is suitable for THC or zaxis control.

this is just one observers opinion

with a cantilevered gantry I don't think it would like the weight.....

this fella thinks differently.....

https://www.plasmaspider.com/viewtopic. ... re#p179560

I'd suggest using it to make the components for your own table that has a working z axis and a dual axis gantry drive arrangement and then selling it as a working machine to build your own and recoup the costs.

[JerryP]

Langmuir is releasing a Z axis thc in a month or so for it.
And plenty of people have added them.
I will not build a 4x4 until I understand my Crossfire

[Jgorm]

I'll find out soon enough with my heavy z axis. The have a small z axis thc retrofit kit coming out soon or maybe even now. I probably should have bought that, but I'm trying to make sure that can be upgraded when needed and eventually I'll probably sell the crossfire.

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