Attaching CNC controller to plasma table

[jeremy13]

We wear going to attach the CNC controller to the metal plasma cutting table. But was thinking of the plasma arc grounding to the table and maybe not being to good for the controller. Will this affect anything or add some bock ground noise?

Miller Spectrum 625 plasma
Hobby CNC controller
steeper motors

[macona]

Have you bought the parts yet? I hope not. I wouldnt use steppers. Plasma likes faster acceleration and the price difference to go servo is negligible now.

Your spectrum is blow back start so there is no HF. There should be no interference problems as long as your cables are shielded properly.

You do realize that a 625 will only be good for about 3/16" to 1/4" on a CNC. These little machines are not rated at 100% duty cycle at their rated output which is what you need for CNC. It is very easy to go past the duty cycle on an automated setup. Also the pierce is not going to be as effective at the lower current you will have to run your machine at.

[jeremy13]

The steppers are from a router table project that got scraped for the plasma table project. So wear not out to much money but will be easy to up grade later if needed. The miller is an older 625 not the new extreme models but have no clue as to it's duty clyle. I need to look at that rating plate.

[macona]

Its 50% at full power for both the torch and the power supply. You will need to drop to about 30 amps for 100%. In a CNC application this will probably give you something like 1/4" pierce cut capability and so-so consumable life.

I would really look at a torch height controller too. They will significantly increase cut quality and consumable life. Especially with thinner material that may start moving around on you.

[kf2qd]

As you are not using high frequency start this may not be a problem, but you might want to connect a good earth ground to you table. I used to build and install Plasma tables and there were a few instances where there was enough noise from just the plasma arc to cause problems. I have run them with no grounding(in our shop during testing) and in the field where we had to make special provision for grounding with multiple ground rods because of local conditions. A scrap of #2 welding cable to a nearby ground rod should suffice.