I've experienced similar issues with my Triumph, mostly when trying to run Cermark too fast. I can't find my pics but this is kinda what happens:
diff.jpg
the upper version would happen at higher power, the long expanses would over-cook the Cermark to gray,
while the short expanses would be nice & black...
The lower version is what happened when attempting to lower the power to compensate;
the long expances would now be nice & black, but the short expanses would wash off because
not enough power was applied to fuse the Cermark properly... very frustrating!
However, Cermarking stainless is the only time I've noticed this issue, engraving plastics and wood isn't a problem. It DOES do it, but it's only noticeable if you look for it.
I believe this can be corrected, at least somewhat, in the controller's settings. But what settings to change, I have no clue!
Here's some of my Triumph's Lasersoft/PhCad parameters:
triparam.jpg
I would love to find an explanation as to what all those parameters mean! I HAVE made some changes that's resulted in WAY less laser head overrun and much cleaner curves when vectoring, but I couldn't tell you which ones!
But I'm thinking some of these numbers may temper down the difference between the power applied over short v long expanses...