Adding Plasma THC to GRBL system.

[CutOnce]

I'm having trouble finding a THC add-on for an Arduino GRBL v1.1 system. Ideas appreciated.

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[CutOnce]

I am not interested in sales talks at this time. I want to discuss what cncZone users know.

[rodw]

I love playing with Arduinos but I think GRBL is a very poor choice for a plasma machine. Stay in the open source movement but consider migrating to LinuxCNC. Thats what I've done.

[CutOnce]

So in other words, nobody has done it. Could under-water cutting prevent the need for THC by preventing warping? Thoughts?

[Torchhead]

Metal warps for several reasons. 1. heat at the cut . Even under water the arc still melts the metal . 2. Stress relief from the mill process (worse on some metal and finishing processes than others. Kee pin mind you need to be able to hold + or - .01 moving at high spped across the entire area of the cut. 3, Typical air plasma torches are not made to cut under water. You either have to have control software that has THC logic built in OR a THC that is stand alone. Cheapest thing that MIGHT work is the Promo SD. Good luck.

[CutOnce]

I will check that one out, thanks. Why is it critical to maintain +/- 0.01" with a CNC when the plasma cutter is traditionally hand-held?

[rodw]

I will check that one out, thanks. Why is it critical to maintain +/- 0.01" with a CNC when the plasma cutter is traditionally hand-held?

Often hand held tips are designed to be dragged along the material. CNC plasma has been around almost as long as hand held and has different parameters. You want minimum clean up and minimum angularity in the cut so tolerances are finer and you need the accuracy to keep the arc voltage stable so the height remains in the desired range. The heat from plasma can easily see flat material to warp by an inch or more.

If you really want to stay on grbl, then the THC could be on a second Arduino. There are plenty of examples of that out there. I kinda think that the CPU processing power of grbl will bite you by limiting velocity and acceleration you can get out of your motion hardware well before you get to optimum cutting speeds, particularly on the Z axis.

I've not used Grbl, but using my own high performance interrupt driven Arduino code, I could get about 400-450 rpm out of a stepper motor. On linuxCNC, the same motor/driver combo is doing over 1300 rpm and achieving > 0.2g acceleration. That is where you need to be.

[CutOnce]

Thanks.