Acrylic Problem

[Chad Paulsen]

I'm having a color problem engraving acrylic. I'm doing 250 of the same plaque and after about 20 of them it started engraving really white instead of clear. Does anyone know what is causing the material to engrave with such inconsistency, i'm keeping all my settings the same as i started. Any help would be appreciated.

[Larry Bratton]

Chad:
You more than likely have some cast material mixed in with your extruded. Cast will engrave white and extruded will engrave clear.

[Chad Paulsen]

All these materials seem to be the same, on one piece it actually engraved clear and white. but now i can only get it to engrave white everytime and the customer liked the clear engraving more.

[Joe De Medeiros]

I was getting clear engraving, when I forgot to focus the laser on the weekend, I was engraving thinner material and switched to thicker, you may want to experiment by putting the laser out of focus, just a thought.

[Larry Bratton]

Cast material can vary in thickness. Extruded is consistent due to the manufacturing method. I doubt you could tell the difference between the two types visually. What color material are you engraving?

[Doug Griffith]

If it changed from white to clear on the same sheet, cast or extruded isn't the issue. It could be that you were walking the fine line between in-focus and out-of-focus and the inconsistency of material thickness caught up to you. Measure the sheets and see if there is a difference. How about passing a flame over the white engraving ala flame polishing?

[Chad Paulsen]

Yeah i'm assuming the lens is going in and out of focus. I measured the material and it varies. What is the standard distance away from the acrlyic should the laser be ive been using about 1/4" away. Thank you guys for the help

[Chad Paulsen]

I'm engraving clear acrylic, it varies in the thickness by a very very minimal amount. You can only really tell by putting your finger over it could this be the reason?

[Chad Paulsen]

Is air assist necessary? i noticed when i run it with it turned off it comes out perfect but were running 250 of them so im wondering if i can get away with not using it.

[Doug Griffith]

Yeah i'm assuming the lens is going in and out of focus. I measured the material and it varies. What is the standard distance away from the acrlyic should the laser be ive been using about 1/4" away. Thank you guys for the help

That depends on the focal length of your lens and where you measure from. I'd guess that you have a 2" lens in which case the distance would be 2" from the top of the substrate to the center of the lens. That will not be easy to determine. You may just want to experiment with burning a hole in a piece of paper to achieve the smallest possible hole. Even better, vector a line on anodized aluminum. Use a loupe to see the results.

[Mike Null]

If you're getting a good job without air assist don't use it.

Just remember to check your lens every so often to be sure it's clean.

[Larry Bratton]

Is air assist necessary? i noticed when i run it with it turned off it comes out perfect but were running 250 of them so im wondering if i can get away with not using it.
Not necessary to run air assist while rastering. A must when vectoring.

[Joe Pelonio]

Not only can the thickness of a sheet vary, but like the Rowmark material acylic is often warped, even 1/4". Be sure to store your stock flat. It's often bowed, much like a piece of lumber, so where the focus is this critical (clear vs white) you may get a lot of differences within the same piece. A Vacuum table helps a lot with thinner materials but with 1/4" or greater your suction may not be enough to overcome the bow. It may help to cut it in half, if the finished item size permits, ad use, for example, 12"x12" material rather than 12"x24" to get it flatter.