Plasma Cutter on the 'Bot

[jimt]

A friend of mine is interested in using a Shopbot as a plasma cutter. I know someone out there has done this already, but I can't find a reference to this in the forum. If you're out there, please e-mail me back with a location and phone number as my friend would like to come and see your machine if it's not too far away. We're in Rochester, NY

Thanks

Jim Turner

[bruce_clark]

Jim,

I could be wrong, but I think Alton Johnson has a
plasma head attached to his SB. He send me a
picture a long time ago, and it was not very
"stock". He said they had to change it to protect
the machine form all the sparks/spray ect from the
arc. He also said they were having problems with
noise, so he had to do a bunch of rewiring.

Now, the sad part is, I cannot seem to find the
info/pictures that he sent me.

Bruce Clark
bwclark@centuryinter.net (mailto:bwclark@centuryinter.net)

[robin]

I also have one running though Vancouver Island would be a little out of your neighborhood. Mine is a dedicated plasma table. The two biggest challenges appear to be keeping the plasma torch at a constant distance from the surface (I've yet to satisfactorily solve this), and shrouding everything in sight. I didn't experience any electrical problems myself using a Lincoln Procut 55 plasma cutter with the optional machine torch head.

[pkleinjan@u-r-online.com]

my machine is a dedicated plasma cutting table with 6" x 12' capacity.it has dual capacity as plasma cutting or oxyacetylene torch.the power source is a hypertherm powermax 1100. steel plate cutting 1/2" thickness 100 percent duty
cutting speed .4 inches per second.
1/4" steel plate at 1.25" per second.
i am using rack and pinion drive which i converted from cable. repeatability of +- .002.
torch height control was solved by using a dc gearmotor mounted to the z axis ballscrew and controlled by the operator. as the cutting process creates a large amount of smoke and sparks it is
crucial to contain this . i solved this by cutting into water .
i'm located in southwestern ontario if you wish to see it in operation.
pkleinjan@u-r-online.com (mailto:pkleinjan@u-r-online.com)

[pkleinjan@u-r-onlone.com]

since i have used the shopbot as a plasma cutter, the issue of torch height control has prevented my machine from running as a true cnc.i have been using a dc gearmotor in place of the z axis stepper and controlling the torch to cutting material manually, a tedious process.my plasma power source has a machine interface with the ability to be able to moniter the arc voltage.
arc voltage directly corresponds to the gap between the torch tip and the plate to be cut.my plasma machine manual gives voltage values for different thicknesses of steel plates, ie: 117v for 3/16" plate.i would install 2 solid state variable voltage sensors,1 would close if the voltage increased because of being too high and the other would close if being too close and the voltage would decrease. i would connect these sensors to si,1 and si,2.my question is can the z axis stepper motor accept these signals to raise and lower the z axis during execution of a part file? i would set the initial torch height with the zero.sbp routine.this could also be used with proximity sensors.this could also work by another zaxis added to the original raised ang lowered by a dc gearmotor and using the zero.sbp routine to set the correct initial height , however the latter seemslike the bettersolution. the voltage sensors are potter and brumfield csj38-70010.

[BoscoToys@thebest.net]

I think if you put the command ON INP([switch number], [1 for on 0 for off]) GOSUB HEIGHT. The height would be the name of your gosub routine. In the routine you would tell the zaxis to do what you wanted. At the end of the sub routine you put in a RETURN command so that the control returns to the correct spot in your file. I wrote a simular routine to sense the depth of my z-axis for engraving at the correct depth. I'm guessing the only differance would be that you have a differant type of switch. If it simply brings the line to zero voltage it should work.