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View Full Version : Question about co2 laser cutting and engraving finish



Brent Ramsay-Boyd
02-18-2014, 11:43 AM
Hi all

I have a question about the type of finish to expect from a CO2 laser.

I have been cutting a few items, and I notice that my edges are quite rough and in my engraving you can visibly see the lines from where the laser is cutting.

I ask because I have had stuff cut and engraved by others in the past and the edges are much smoother than I am getting, and so is the engraving.

Does anyone know why this could be happening.

I have an 80W shenhui laser

Regards

Brent

Dan Hintz
02-18-2014, 3:40 PM
There is typically a very fine ridge on even the best-cut acrylic due to the constant build-up/ejection of dross... a poorly-cut piece will show an exaggerated ridge. The ridges are also highly affected by your air pressure... too high and you cool the acrylic too quickly, leading to a nasty edge... too little and you can see melted edges and flare-ups.

If you absolutely must get rid of all ridges, you need to consider a post-operation like flame polishing.

Mark Sipes
02-18-2014, 3:50 PM
Not familiar with your settings but the ppi/hz settings should be set high so the laser is not giving you a pulse pattern when cutting, also travel speed is a factor.

Joe Pelonio
02-18-2014, 9:47 PM
I only have 45 watts but with the correct settings I get fairly close to flame polish quality on 1/4" acrylic, and 1/4" wood is as smooth as if it's been sanded, but darkened from the scorching.
You may be using too much power, or not enough speed. Mine uses "frequency" rather than PPI and I set it at the maximum for acrylic, 5,000, and about 25 lbs of air assist.

Mike Null
02-19-2014, 5:22 AM
The edge you are describing is referred to as "coin edge". Typically, you should be using just enough power to get through the material. If you have ppi/frequency settings play with them until you find a better result. I often use two passes to get a cleaner edge.

Check all your belts, bearings, pulleys, etc. to be sure all are functioning smoothly as a problem here can produce such results as well. Be sure your lens and mirrors are clean, secure and in focus.

Dave Sheldrake
02-19-2014, 8:00 AM
It's a ShenHui machine guys, no way to change the PPI and it's a DC pumped tube so changing the frequency can kill the PSU and Tube.

Slow and hot is the only way on a Chinese machine Brent, nature of the beast I'm afraid, DC units are much lower quality beam profile and have a fixed pulse rate usually with lower quality optics. Keep your air down at 2 - 5 psi if it's through the cone air assist.

cheers

Dave