[N2950H]

Does anyone know what causes these little divots at the start/stop point of the plasma arc? The area of concern is at the bottom of the O in the photo. The most obvious cause to me was a lead-in/out that was too small, but increasing those seem to have no effect; they still show up even when moving the pierce point well away from that area. The piece in this photo was done with new consumables so I don't think that has anything to do with it either.

I think my setup has always done this, but it is more noticeable now that I am doing more detailed work with 1/8" steel. About the only other thing I can think of is to try placing the start/stop on an inside curve to see if that makes a difference, but obviously that wouldn't work on round or oval cuts. Any other ideas?

My setup:
Precision Plasma 4x4 LD gantry
Hypertherm 45
BladeRunner Dragon-Cut 4-300 kit with DTHCII
Mach3 and SheetCAM

[shad71]

May be will help this post Revisiting those blasted divots... - PlasmaSpider.com
Also any information there are on the Tech Tips topics Tech Tips - PlasmaSpider.com

[flyinwilly]

A few things to check.

With Sheetcam, I use a ramp type lead in and a arc lead in and lead out. I have found (through trial and error) that the lead in / lead out length should be at least 3 times the kerf width. Also, don't have any end of cut delay (with thinner material - up to 11 ga).

Also, I use a inside offset and make sure you check reverse cut direction on your operation screen. This will give you the correct swirl pattern for the Hypertherm machine.

I don't get any divots with these settings but I very seldom cut anything thicker than 11 GA.

Good luck.

Willy

[plasmamatt]

I've always assumed that those little divots are at the point where the torch crosses over the cut path. It is the same as if you have ever tried to cut over the same cut path twice. The cut width is substantially wider the cut quality drops off.