Laser Cutting 3/8" White Acrylic & Getting Burned Edges

[RJlaser]

Hello everyone!

I saw a thread on this subject already. Here is my issue. My company owns a 400w Kern laser. It's a beautiful machine, and cuts everything perfectly except for this 3/8" white acrylic. We are cutting out letters and numbers about 6-7 inches high. What happens is the edges of the acrylic get yellow, and black burn marks on most of the letters. I've found some settings that minimize the burn but does not take it completely away. Some people were saying that its the brand of material that we use. I'm not sure what brand this is as we peeled all the mask off and threw it away. Does anyone know of any specific brand of cast or extruded 3/8" white acrylic that is good for laser cutting? Thanks in advance all.

RJLaser

[lamicron]

If you cut it with the protective plastic cover the yellow mark will be on the cover, maybe that way you can do the work.

[RJlaser]

Thanks for the reply. I don't think I was specific when explaining my problem. The burn marks are on the edges of the letters not on the face or back. I should be getting a nice polished edge but instead I am getting black and yellow burn marks on most of the edges of the letters.

[zax15uk]

It sounds like you are flaming. Increase your air assist and/or raise the sheet from the table.

Zax.

[RJlaser]

The material is raised up 1/4" from the table. No flaming is happening at all during the cutting process. My air assist is on 20 psi and I tried going up to 30, 40 , 50 and 60 psi with the same output. The only thing that has worked somewhat is slowing down the speed to .6 ips power to 65% and frequency to 10000. I'll keep testing and see what happens. Thanks all.

[Litografa]

May be you have possibility add inert gas in laser area. We just have tests on thick grey porous rubber (12 mm) - excellent results with Argone - no burn/yellow cuts at all.

[DaveDoesIT]

Have you tried...

Setting focus to the middle of the sheet? i.e. setting the focus point 3/16" deeper than the top surface.

Drop-power and up-speed and do two passes. I find two passes on acrylic gives better results and I don't have air assist.

Dave