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Plasma on a Shapeoko, feasible?

Posted: Tue Dec 01, 2015 8:05 pm
by oskanaan
Hi,

I saw this post about using a plasma cutter with a Shapeoko but was wondering if it has been done by anyone and still operational with no issues? I saw this youtube vid showing one which uses a plasma cutter but nothing else, it doesnt seem to be a popular option. I think the belts wont go well with all the sparks and stuff, but do you guys think there are other reasons for not using a plasma cutter with a shapeoko?

Thanks!

Re: Plasma on a Shapeoko, feasible?

Posted: Tue Dec 01, 2015 9:37 pm
by WillAdams

Re: Plasma on a Shapeoko, feasible?

Posted: Tue Dec 01, 2015 10:29 pm
by oskanaan
WillAdams wrote:http://www.shapeoko.com/wiki/index.php/ ... sma_Cutter
The shop they are referring to is closed :), maybe that is my answer right there.

Re: Plasma on a Shapeoko, feasible?

Posted: Thu Feb 25, 2016 6:50 pm
by Gamble
I have a plasma CNC table. You need something to turn the plasma on and off with every cut
I suppose you can sit there by hand and hit a button but that would suck for results

Most of my sparks are on the I it's pierce. If you cut at the correct speed and height and have good consumables all sparks will be under the metal

Re: Plasma on a Shapeoko, feasible?

Posted: Thu Feb 25, 2016 7:02 pm
by RoguePirin
Gamble wrote:You need something to turn the plasma on and off with every cut I suppose you can sit there by hand and hit a button but that would suck for results
You can get this using the PWM signal output on the Carbide Motion controller board to indicate on/off. It will give a solid +5V if set to full speed with the M3S### command (I think it is 10000 by default). Of course, you would need to send an M5 after each cut to turn it off again. I would hope CAM software for plasma cutters would issue this for you??

Re: Plasma on a Shapeoko, feasible?

Posted: Thu Feb 25, 2016 9:03 pm
by jacob32123
My experience attempting this was that the plasma cutter could be easily controlled using the spindle on/off signals, but that without torch height control cut quality was so bad the parts were useless.

Re: Plasma on a Shapeoko, feasible?

Posted: Thu Feb 25, 2016 10:38 pm
by Gamble
RoguePirin wrote:
Gamble wrote:You need something to turn the plasma on and off with every cut I suppose you can sit there by hand and hit a button but that would suck for results
You can get this using the PWM signal output on the Carbide Motion controller board to indicate on/off. It will give a solid +5V if set to full speed with the M3S### command (I think it is 10000 by default). Of course, you would need to send an M5 after each cut to turn it off again. I would hope CAM software for plasma cutters would issue this for you??
It's not a voltage switch it's a simple open/closed circuit so yes you can probably use a PWM or something similar to it
My software does it automatically. I design, set my cut path and lead in/outs are automatic and I export my gcode to cam. It's easily the easiest cnc to operate ever
jacob32123 wrote:My experience attempting this was that the plasma cutter could be easily controlled using the spindle on/off signals, but that without torch height control cut quality was so bad the parts were useless.
I don't have height control. I get excellent cut quality. Especially on 3/16 mild steel. I just did some 1/4" aluminum that I was pretty happy with the results. Not as good as one with height control of course but no complaints here. Majority of my work is .100 or thinner steel & aluminum. Dross on 14g steel sucks. Dross on .063 aluminum is almost non existent.

Re: Plasma on a Shapeoko, feasible?

Posted: Sun Feb 19, 2017 10:59 pm
by BDuplan
I'm running an Uno with the cnc (grbl) shield v3.51 to control a home-made 4'x4' plasma table. I'm using pretty large Nema 23 stepper motors and DRV 8825 drivers on the shield. I'm in the very early stages of testing it out and don't currently have torch height control (THC). I was able to get some very good results with a pen where the torch goes. I have re-done the bed since this picture using 2" X 1/8" flat bar. It's now very stiff.

Image

I have a Hypertherm Powermax 45XP with the CPC port, which means I control the machine and receive divided arc voltage and Arc OK feedback from a connector at the back of the plasma power unit. The torch has blowback arc and all of my stepper motor wires are shielded and grounded in the control box. I'm hoping that it can handle the plasma arc. The cutter is powered on it's own 240V circuit.

The machine torch is mounted on a floating bracket that allows probing. The z axis will lower and then the torch nozzle touches the work piece and begins floating. While the Z axis continues down, a microswitch opens.

For now, I'm just trying to get it going without THC. I'm evaluating SheetCAM currently, but the only post that I can get to reliably work is the 'minimal gcode, no arcs' post. I've tried a bunch of the other included plasma posts with no luck. It would be great to find a post that has the probing sequence built in that will work with grbl until I get the THC controller running. Any suggestions?

My plan for that is to try to make a custom THC with a second Uno that essentially interrupts the torch-on signal coming from the grbl shield. It will send a signal back to the hold pin on the shield. Then it will do a probe sequence, send the cut command to the cutter via an opto-isolated mechanical relay, send a resume signal to the shield, plunge from pierce height to cut hiehgt, and finally begin closed loop control of torch height. If the SpinEN pin is low, it will just pass Z-commands through. I've never programmed an Arduino before, so that should be a learning experience. I'll also have to come up with some UI for entering target voltage (which translates to a torch height) for the given material. Hoping to just do that with software.

This is the first time I have done anything like this. I have quite a bit of Matlab experience, and from the C++ tutorials, the concepts look very similar.