Torch Jumping Up And Down!!!

[Deezl Smoke]

Ok, just an update of sorts. I checked the ground cable, and though it was not coiled, I spread it out a bit. It is not too long and in good order.
The customer had me do a fair bit of bending with my press brake. This brought a whole new conundrum into the works. Customer helped me bend the first 2 pieces to set the brake and get an accepted result. Those 2 pieces were cut from a previous plate drop. Customer supplied. Now the customer brings in 11 5x10 sheets from a different supplier. I checked the thickness with a caliper and it was near .009" difference. Ok, there is a tolerance listed. This new delivery however, though the same designation A36, wont bend for crap. It made so much noise in the brake and virtually would not bend a few parts. It took a whole new setting of parameters.
This larger delivery, would not cut in the plasma worth a darn either, the torch had that "sewing machine" affect, not all of the time, but at inconsistent intervals. Finished that stack of plate, then got a coll for a few more pieces. Ok, once again, a new delivery from another supplier. Thickness within stated tolerance. Cut beautiful. No sewing machine. No dross. (water table) So on to the brake. Same settings, over bent by huge amount. WTH? And it was even a bit thinner sheet.

So, what I am thinking, is that even though a plate has a designation of say A36, it can also be multi-grade. It can also be a completely different metallurgy if it comes from over seas vs. domestic. This difference in metallurgy and grade may be one of the causes of the sewing machine affect. ? What opinion would anyone have on that?
Could it be that my torch needed a different cut height for the tougher cutting plate? Could the metallurgy cause the voltage to be out of spec for that tool set?

[weldguy]

Indeed steels from different mills or especially overseas can be different and cause exactly what you are seeing. A different cut height should not be required, you would likely do better by doing some test cuts at different speeds using the proper cut height and see what works best for the material your currently using. Sometimes you need to go a little slower or faster for best results. When you find the speed that is cutting well double check the cutting height by pausing the machine and measuring with feeler gauges to be sure your still where it should be and adjust if required.

[adbuch]

Weldguy gives some good advise. I agree with his recommendation.
David