SRS,
As I understand it, different plasma cutters work differently. Some work best with a small gap. The Hypertherm has a "drag tip" that has some castelations on the tip (notches like a castle wall) that I believe allow for some air flow to help stabilize the arc jet. It actually cuts best with very light drag pressure against the cutting surface. I have found that if the surface is smooth, it is easier to drag smoothly. If you find yourself jerking the tip, you will not get as smooth a cut. If I find the surface roughness is causing me to skip, I just lift it very slightly above the roughness and it seems to still cut just fine. Of course, if you get very much extra gap, it doesn't cut through as deeply.
Also greatly affecting the quality of cut is the electrode and nozzle condition. They gradually erode from normal use and eventually they cause the plasma jet to become unfocused and even spray out in a diagonal smear. At that point (or sooner if you want the best quality cut) the consumables need to be replaced.
They say that very clean dry air is VERY important to quality plasma cutting. I added a large 5 micron air filter and water separator in addition to the air filter and water separator in the Hypertherm. Initially, I had a desica gel drying cartridge, but it got used up and I need another. They change color from blue to pink when they absorb enough water. I guess the fact that it did change, tells me that I ought to get another one.
I've attached here a picture of three steel plates that I removed from the bottom of this plate today. They are about six inches by seventeen inches, half inch steel with some cuttoff ends on the surface. I was really kind of worried that these would be real tough, wasn't entirely sure what I was going to do because they were attached with good fat weld beads all the way around on all four sides. But today I decided I would try gouging out the welds and see if I could remove one. I used the same technique that I had used on the angle iron, except that getting the chisel started was a bit harder because of the continuous welds. But once I got it started, they came off pretty easily. Once I got a quarter inch gap, I saved some time by putting in a large pry bar and whacking it with a sledge. At that point it went pretty quickly. Once you've gouged out the bulk of the welds, they don't have much strength.
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