Engraving Acrylic with a laser creates amazing end products!
You can engrave acrylic on either the back or the front of the acrylic. If it is translucent or mirror, engraving from the back can give it a nice dimensional polished finished look.
This photo shows the same turtle design engraved on Crystal Clear Acrylic. The Left side shows the design from the back. The Right side shows the design from the front.
There are 2 main types of acrylic, Cast acrylic and Extruded acrylic. Both these acrylics are laser safe and fine to use with your laser.
Cast Acrylic is made by the manufacturer pouring liquid acrylic between a set of temper glass sheets. This liquid hardens and becomes the acrylic sheets. When engraved with a laser it gets a frosty appearance to the engrave. Cast acrylic cuts clean and has very good optical quality.
Extruded acrylic is made by the manufacturer adding acrylic pellets to an extruder which melts it down and then presses it through a die at high pressure to make a sheet. Most mirror acrylic and a lot of specialty acrylics are extruded acrylic. Extruded acrylic engraves with a clearer engrave then cast. It is also much softer so doesn’t need to cut or engraved at as low of a speed as cast acrylic.
When engraving extruded acrylic, engrave first and cut second. The big reason for this is that if it is cut and left sitting during the engraving, it will most likely melt back together in some places. Extruded acrylic should be cut at the fastest speed possible and then taken right out of the laser and taken apart.
When engraving on mirror or clear acrylic, turn the acrylic over, reverse the image and engrave it from the back. The engraving will look a lot more polished and clean.
Acrylic engraves with a nicer look if you defocus the lens first. To do this you manually set the focus. When I engrave ⅛” acrylic, I usually set the focus at .3 for an even and smoother engrave. Trying different settings in small circles or squares to see what focus your laser engraves a certain piece of acrylic, is a great idea.
This pictures shows Crystal Clear Acrylic engraved at 1000 speed full power for both. The left side is at .3 focus and the right side is at .12 focus. You can see the difference between the raster lines by defocusing the laser. Defocusing creates a smoother finish.
When engraving acrylic, I usually remove the masking on the engraving side and put a thin layer of liquid dish soap on the acrylic instead before engraving. You can remove the masking on both sides if you would like, then cover both sides of the acrylic with a thin layer of dish soap.