All About Acrylic: Focal length and point

Learn more about how focal point and length can determine edge quality.

Learn more about how the focal length and focal point can determine edge quality when laser processing acrylic:

Focal length: The focal lens choice will play a role in the edge quality. Ideally, a 2.5-inch lens will work with thicknesses up to 3/8-1/2 inches. Anything thicker may require a 4-inch, 5-inch, or maybe even a 7-inch 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: 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-inches thick, you should focus in 1/3 of the total distance (1/2-inch acrylic would need to be focused in approximately 3/16 inches.) This will keep the edge as straight as possible. The longer the focal point of the lens, the straighter the edge will be.

-Josh Stephens, Trotec Laser

Josh Stephens Lasers Plus

Josh Stephens

Josh Stephens is the owner of Lasers Plus. Formerly, he was the lead applications expert for a large laser manufacturer. He has been in the industry for over seven years.

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