Laser cutting acrylic is an art and a science. There are many factors that will play a role in your ability to get the best possible edge; both in the material as well as the laser cutting machine itself. For example, the brand of acrylic and the type of acrylic can great impact the job. Other factors of variance include laser parameters: power, frequency, and speed; and laser process setup: table setup, focus, gas, exhaust, and material preparation.
It's true that laser cutting acrylic can be very profitable, but it is also quite difficult, especially if you are after a “flame polished edge”. There are several best practices and tips-of-the-trade for processing acrylic on laser cutting machines, one important factor is focal lenses and focal points..
The focal lens choice will play a role in the edge quality. Ideally a 2.5” lens will work with thicknesses up to 3/8-1/2”. Anything thicker may require a 4”, 5”, or maybe even a 7” lens. This is where laser power will come into play. When the focal distance increases, the amount of energy of the laser will seem to decrease. Not having enough power will mean slowing the laser down significantly to cut through the material. There is a point where cutting slower will not work because it will increase the chance of flare-ups that can occur when cutting acrylic too slow. Acrylic is flammable and the only cure for this is more laser power. Then the acrylic can be cut at optimal and production friendly speeds and still get the nice polished edge. Achieving a high quality edge with multiple passes is very difficult.
Focal point will have an effect on the angle of the cutting edge. The thicker the material the deeper “into the material” the focal point should be. For acrylic over 1/4" thick, you should focus in 1/3 of the total distance ( ½” acrylic would need to be focused in approximately 3/16”.) This will keep the edge as straight as possible. The longer the focal point of the lens, the straighter the edge will be.
Ensuring that you have taken into consideration your focal legth and focal point is the next step in getting perfect results when laser cutting for flame polished edges. Stay tuned for more tips on getting flame polished edges when laser cutting acrylic.