There are some common issues that you may face when laser cutting acrylic. When laser cutting on a honeycomb laser bed, the metal honeycomb can reflect the laser beam back into the acrylic. This creates a flashback effect that can leave tick marks on your acrylic piece.
Raising the acrylic away from the honeycomb bed by placing it on standoffs while cutting helps reduce this problem. Standoffs should be roughly 3/4″ to 1″ tall. If you still see flashback when using standoffs, apply additional layers of masking to the acrylic to help absorb the reflected beam before it hits the acrylic surface.
Another issue that may occur during laser cutting is that the acrylic piece may have stick marks on the cut edges. Stick marks appear as matte spots on an otherwise flame-polished edge and are caused by the acrylic sticking together at the cut line as it cools down. Stick marks typically occur when the space between parts is too thin and flexes toward your piece from the heat of the cutting process.
Another cause of stick marks is that the cutting speed is too fast. Ensuring proper spacing and reducing the cut speed of the laser should eliminate or significantly reduce the stick marks.
Another issue that you hopefully have not encountered is a laser fire. Acrylic is flammable, and when not laser cut at the correct settings, it can easily catch on fire. Running your laser at the optimal settings is the best way to reduce your chances of fire, but fires are something that you should always be prepared for.
It is crucial to always watch your material when laser cutting acrylic. Once the acrylic is on fire, there is not much you can do to salvage that piece, but catching it right away can save the rest of your sheet stock or even save your laser.
