Not sure of my laser settings for red/black multi-layered plastic (BF Select)

[Amy Shelton]

I have a 12" x 39" wall-hanging to engrave. I am piecing two 12"x24" sheets of BF Select, 1/16" red with black core. When engraving small details and areas that are 3/4" or so, it looks even. But engraving large areas, it just looks blotchy.

I read somewhere that certain Rowmark products should use two passes. I played around with different settings, and this is what I thought did best:

75 power, 100 speed, 500 dpi, with image density of 3 on my 50 watt Universal, TWO passes

I thought a dot pattern (I used 70% gray instead of full black) would help to decrease the amount of warping, plus would give it some texture. And I used image density of 3 because it looked good enough and would decrease the time.

By the way, to secure it, I used a coroplast sign, and sprayed some temporary embroidery adhesive on it. It worked well but I should have sprayed it a little heavier, it came loose at one end. I left it attached to the sign while I vector cut it also.

Have you noticed that different colors of engravable plastic, even from the same manufacturer, require different settings?

Any advice is greatly appreciated.
Amy

PS The dark blob at the bottom of the picture is the shadow from my camera lens; I had it on macro.

[Dan Hintz]

Sheets from the same batch can engrave differently, but usually same batches are similar enough not to notice (it only gets critical when you're doing very fine work)... be aware of it and shoot for a few % higher power. If large areas are being removed, multiple passes would certainly cut down on warping.

[Mike Null]

I thought I responded earlier--must be old age.

Yes, different colors may require different settings. Not a lot different but something like 5% more or less power or speed will usually do the trick.

Try a little mineral oil to even out and darken the color on the engraved area. If you're getting warping caused by engraving on 1/16" material you may be using too much power.

[Amy Shelton]

Thanks Dan and Mike for your replies! I think I got it.

I didn't get much warping, maybe because I engraved in multiple passes and I used a 70% black. But now I'm wondering if that's what caused the uneven patterns.

The solution was to engrave it a third time, at a low setting (35p 100s, at 4 image density) and I made the filled area 100% black. It's still not great, but it is ok in my book.

I didn't think of mineral oil!

[Dan Hintz]

Thanks Dan and Mike for your replies! I think I got it.

I didn't get much warping, maybe because I engraved in multiple passes and I used a 70% black. But now I'm wondering if that's what caused the uneven patterns.

The solution was to engrave it a third time, at a low setting (35p 100s, at 4 image density) and I made the filled area 100% black. It's still not great, but it is ok in my book.

I didn't think of mineral oil!
If you're trying to completely remove an area, using less than 100% black can give you patterns (not like the one you're seeing though, I'm talking about cross-hatch). Less than 100% will dither the output pattern to create a faux-grayscale, but you want every point burned off. Try it at a more reasonable 300dpi (density 4 is 333dpi, so that's fine) for speed @100% black, and if that's leaving red you can bump it up to density 5.