Has anyone worked out good settings for vector engraving edge lit acrylic panels (e.g. for simple line art or text)?
Are there any established “best practices” for edge lit acrylic (in general) so far?
Because of the way motion control is handled in the Glowforge, there tends to be significant depth variability during vector engraves (scores). Going around corners seems particularly prone to creating spikes. This all makes the engrave look kind of rough. I’ve had some luck reducing this by using lower power at slower speeds and, by disconnecting corners in the designs.
I searched the forums but, didn’t really find anything relevant. I suspect I am probably just not finding it with search. I saw that some people were converting vector engrave to raster for edge lit applications. I hate to give up speed and simplicity if I don’t have to.
I’ve pretty much used PG settings for mine. I’m on my phone right now and need a bigger screen for searching, but there was some discussion of defocusing the beam to smooth the engrave, and what lpi is optimal; alternatively you can flood the engrave with solvent to smooth it and add some transparency.
I’ve got to go wrestle a 2yo into take by a nap (babysitting the grands today) but if nobody’s turned up links for you by then I’ll pull out my laptop and see what I can find.
I use .210" chemcast for my edge lit signs. I always reverse the engrave and go from the back. I am most satisfied with 700 pews and 80 zooms with a 340lpi. It takes longer but it is a good balance for smaller text and thicker graphics and lines. If there is a large area of engraving I go ahead and defocus sometimes, but in general I don’t have that much of a visible engraving line. I’m happy with that.
I am almost always engraving filled vectors, but sometimes there are bitmap graphics.
Here is the result but I didn’t post settings here.
By the way. I am using a thicker, .220" acrylic, just a hair thinner than Proofgrade thick. That’s why I like a deeper engrave. If I do the medium acrylic from Glowforge, I do a little faster and more power for not as deep an engrave.
I ran some additional tests in different ranges suggested here. There are lots of little 1.5" test squares everywhere.
The settings that seem to be about optimal for 0.24" thick clear acrylic and Lightguide acrylic (no masking) are 115/50 defocused to 0.5".
This gets an engrave depth of around 0.08" (~2mm). That’s a little shallower than I was aiming for originally but, it actually seems to work better. There is still a minuscule amount of spiking at some points but, you really have to look for it to see it. So, I am calling it good.
At this point, I also think I prefer the regular cast acrylic to the Lightguide for this edge-lit application. The regular acrylic has more contrast when lit. The Lightguide shows the path of the light beam through the acrylic a bit – like a flashlight beam through dust or smoke. Not surprising, since the Lightguide is a suspension of light-scattering particles.
Edit: I am reversing the designs and engraving on the back. The main difference from what I was doing before was the defocusing.
Change the focal point setting (you’ll need to be using Manual Engrave for the operation). You want it to focus above the acrylic to smooth the engrave. So if the material is 0.125" you put something like 0.250" in the focal length field. The beam will be wider when it hits the material and burn a thicker line with each pass.
Quick update if you are trying this: I switched to masking the engraved side. I found I could get most of the residue off with toothpaste and a lot of rubbing but, just masking it was easier. I also learned about the joys of crazing and annealing by trying to use isopropanol to remove residue.