Ha! That explains all the dross on my first 1/4” cut… metal was cut through but the dross held the piece really good
The reason for these shims is to minimize blowback. By the book your cut height generally won’t change until you get to super thick stuff. Usually cut height is around 1/16" (the thin shim). Then your pierce height is a percentage of that. 200% 300%. I usually just go 2.5 times cut height. The thick shim creates clearance between the tip and work piece, because the machine has a fixed z height, so when you pierce the tip won’t stick to the material from the blowback at start.
I am a bit confused - but again i am a novice. Looking at your first image - it looks pretty good to me - just some top dross perhaps from having too much height. - your second image to me looks very clean. But that curf looks huge to me in comparison to what i would expect to see. and compared to the first image.?? so I guess i am trying to figure out if that is the case -and what you could do to narrow that up?