Optical clarity raster laser settings without flame polishing acrylic surface

[Ed Jamron]

I want to find the ideal raster laser settings of power and speed to maintain optical clarity without the need to flame polish on as large as 4'X8' transparent colored sheets of either cast acrylic or extruded that I've seen stay clearer than the frosted effect normally looked for in cast. I'm not concerned with the edges but the overall surface that I will be ornately sculpting more than just a superficial texture or pattern as much as 2/3 the way into the sheet in many areas. I will modify my files to take into account any limitations. I'm using a new 400 watt Kern laser and thicknesses will range from 1/16 inch to 1 inch.

Thanks
Ed

[Dan Hintz]

High frequency will be key here. At 400W, you won't have to go slow, that's for sure.

[Matt Turner (physics)]

Hi Ed,

Have you talked to the Kern folks about this? One of the guys at our lab had the same question for them a while back. I don't remember exactly, but they may have recommended doing a second pass slightly defocused, which basically uses the laser to do the flame polishing.

[Ed Jamron]

Hi Matt

I'm on a mission and must be successful on maintaining the optical clarity without the flame polishing. I'll forward the settings to you tomorrow from Kern and I believe they said 1/16th out of focus on the last pass but still real frosty and unacceptable. Can you check with your associate to see the exact settings he may have ended up using from Kern or otherwise developed to get heavily carved surface optical clarity. I've a large scale project that requires this consistent result and it won't happen unless I'm successful. I'm working with a local firm but could work with anyone that can get me the results of power, speed and optical clarity to arrive at efficient, consistent results. A 100 watt laser or even less would probably provide such results.

Thanks
Ed

[Ed Jamron]

I'm told they do 2 passes. Normally about 1/16th out of focus. 50-55 inches per second 100% power. Second pass 120 inches per second 65-70% power. You will hear a little air coming out of the nozzle.

[Kev Williams]

I would have to think you'll need to be WAAAYYY more than 1/16" out of focus, I routinely get decent engraving results at more than .060" out of focus both directions.

Just a stab in the dark, but I'm thinking a long lens, 4 to 6" focal length- because of the fatter focal point to begin with, and because of the forgiving depth of field- and I would start at LEAST 1/4", if not closer to 1/2" out of focus, medium-ish power and crank it up as needed. If nothing happens, then tighten down the focus until something does happen...