brown parts when engraving anodized aluminum

[anchange]

I’ve been having some weird results with my converted k90. I’m trying to raster anodized aluminum. I got some settings that I was happy with and it was working well. Without changing the settings or the material after a while of lasering I started getting brown parts. The “Test” text in the picture is the same setting as the “150/50/.05” text. I believe the brown indicates that the material isn’t getting enough energy to engrave all the way and turn white. Is this correct? Why is this happening???

[anchange]

Also just to confirm which was does the lens sit. Does the bowed out (convex) side sit down or up?

Thank you for any help you can provide

[Tech_Marco]

It look like that you're doing cutting instead of engraving. Double check it

Marco

[anchange]

I've always been on engraving but when I check the PPI box it works much much better. Any idea why this is?

[Tech_Marco]

I don't think that you're doing engraving for all those charactertics . The "TEST" surely look ike it's running in 'cutting' mode. Was it on a single layer or multiple layers?
The "PPI" is designed to work for better result when doing 'cutting'.

You may post a screen shot of the LaserCad on both drawing and the setting. If it's on a single layer with engraving setup, it surely weired enough

Marco

[anchange]

I was definitely in engraving mode but without the PPI box checked. I tried many many settings with some good results for awhile but then things went a little wacky. I wouldn't change the setting and the results would be varied. After checking the PPI box (still in engrave mode) I got perfect results. I believe the reason the edges are white is because the laser dwells there more when it's turning on and off (and reversing)? The head was definitely moving rapidly back and forth on the x axis, it did not ever make an outlining motion on any of the prints in the picture.