i have a miller 125c that i am going to use to make a cnc plasma to cut sheet metal and have 2 questions

1. whats the smallest relay i can get away with using a 10 amp is the biggest i can find for my mechtronic board will this work

2. if i cut sheet metal sheets 3feet x 3 feet how much will it warp as i dont want to buy a thc yet and suggestions

1. you only need a very small relay trace back the wires from the torch handle and switch those.

2. Make a floating head that will hold the metal down. Easiest way to do is with a pneumatic cylinder and some roller balls in round shaped disc to roll over the material while the cylinder pushes down only lightly

i find the machine allmost useless without a thc,
i got good result on 1mm thick steel sheet, and unusable on 0.8mm stainless.

but the thc is not only for warping, u will get more control on the pierce/cut height, resulting in better cuts and longer consumable life, i will tell you more when my thc arives ...

If you use a floating head with the drag tip you will be fine.

John