Had the same issue that you get with the animals. Most of the light is blocked before it reaches the top of the engraving…
Tried a number of ways to correct this but nothing very successful that was easily to duplicate.
The best I got was raising the bottom of the image, so it was slightly out of focus, as it moved towards the top it would become more focused and engrave deeper… it turned out to be too touchy to be of any use… had to combine the right lenses…
This is an early one I did … it’s still got the plastic protection on the back… you can see it. I currently flip the image and engrave it on the back. The laser side has the protection peeled away.
also it could be gas buildup between the black cardstock and the acrylic. i have filmed this happening and has the same affect (dark areas) that look less engraved. the gas creates a cloudy barrier that reduces the power that the laser has to react with the cardstock, thus burning less. i found that having the cardstock and the acrylic as flat as possible and even contact. the problem is i found while trying to get desired results by adjusting my settings, when i got the desired result the power was high enough to make the “gas cloud” that affected the laser and finished result.
ultimately i turned to the tempera paint method mentioned and stopped having problems because there is nowhere for “the gas” to build up.
If it helps, you may want to try black tempera paint. I never had any luck using the black paper behind the acrylic method due to burning. What I do for both glass and acrylic with my diode laser is air brush black tempera paint onto the surface until it’s a nice solid coating when held up to the light. I can usually do it in 2 coats. The reason I use an airbrush is because it makes a nice even coat, unlike brushing, but you could try a fine mist spray bottle. Tempera paint dries pretty fast. Two nice things about the black tempera paint is 1. You engrave right on the painted surface, not on the back side of the glass or acrylic. 2. Tempera paint is just about the easiest thing to remove. I just wash it off in the sink with warm water and maybe a touch of dish soap and it rinses right off. I’ve done more glass than acrylic, but it works on both.
Even though I have been here in Texas for a long time now, I was born an Okie. Two kids and 4 grand kids
still live in Ok. Seeing how I have one granddaughter w/ my great granddaughter living in Nebraska , I’ll use Nebraska for my test burns. That way I won’t feel bad when they turn out awful. (LOL) My granddaughter may be living in Nebraska, but I was told by her that she wants an OSU light. Smart girl, although she graduated from OU ? I never have figured that part out yet.
Randy
I was wondering why you had Texaswoodcnc. What part of Tx are you in? I’m 14 miles east of Wichita falls and 6 miles south of the red river, (state line).
I have used tempera on glass before, had good luck with it. I posted my first glass work on here about 16 or 18 months ago.
Randy
Hello Fred: 50 mm to the bottom of the heat sink and 40 mm from the bottom of adjustable focus lens.
I using a Zeus 15 w., Lums. output laser module mounted to an Ortur frame and controller. Because of my mickey mouse air assist I have to do manual Z focus which is ok.
Randy
My success has come with two things: Peel the plastic off the side you are engraving first. Easier than after and better results. Secondly, I would check your image and increase the contrast a little. That way, any subtle things in the image you are not seeing on the screen, but the laser is seeing will go away and not burn.
JacK _ I knew Olney was south of me, but not sure how far. So I googled it. Straight down hi-way 79 from Petrolia to Olney is about 59 miles (94.95 kilometers) by car. Closer than I thought!! Why, it’s only a skipping stone throw from me.
Randy
