Lead in-out point cut quality

[Metriccar]

I was experimenting with my Plasmacam yesterday on thicker metal than I normally cut. Normally I cut thinner stuff so it’s not a problem, but on the thicker stuff, like 3/16 or more, I was getting some messy parts around where the torch leads into and turns at a 90 degree angle to start actually cutting the part out. What was happening was in inner diameter holes. I had a lot more bevel where the torch came in and turned 90 degrees to begin cutting the hole out. Lowering the acceleration helps. It’s almost as if the acceleration is too high and it’s going around corners, the top of the flame is cutting ahead of the bottom of the flame, giving a lot of bevel.


On top of this I changed a setting called “gap at end of loop”. Cutting 3/8” thick metal, I made the gap -.10, meaning the torch continued cutting .10” past the 90 degree lead in. Doing these two things, I seem to be getting a lot better holes. I tried different lengths for the gap but found .10” to be ideal for 3/8”.

Outer diameter is a different story. I get no consistency there. I tried changing the lead in to 45 degree angle, that didn’t help. And I think cutting .10” past the lead in is a bad idea… by that point the part has dropped out and the torch will be doing a totally random thing to it every time depending on how the part falls! I tried different gap lengths but just when I get a good smooth part, I try it again and get a different result. How are people handling the lead in/outs on outer diameter cuts to get better cut quality? Do people have different cut paths for inner and outer diameter cuts? Meaning they will have different settings for circles than they do the outer edge of the parts? That seems to be the best way to go right now.

As far as divots go, I was using a setting incorrectly. “overcut to reduce undercutting” at a high setting seems to cut into the part, ie the lead in goes in too far leaving a divot. I thought this was actually a setting to keep cutting past the lead in but that’s actually the “gap at end of loop” setting. When I unchecked this option, I do not get any divots.

[DXF]

Hope this helps. I radius inside (.040" - .050") and outside corners (.030" -.040"). I know a lot of you are saying "F" that. The reason for the radii is it cuts smoother and it gives you many points to shoot your lead-in from so you can center it on an inside or outside corners and it doesn't take that long to radius the corners. Most of my lead-ins are .150" long and the kerf width of my plasma is .035". I've included my settings that work great for me using a Plasma Cam machine W/O THC and 15 years old.

Dave Hanks