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Denver Shearon
01-13-2012, 4:00 PM
Hello all,

I was wondering if anyone out there had a solution to the raised top edges I am getting on acrylic. I can minimize the visibility of the raised edges but only at the expense of the smoothness of the actual edge. Using faster speed and multiple passes gives lousy edge results. Can this be fixed with stronger air assist?

Gary Hair
01-13-2012, 4:21 PM
How about some more info - laser power, laser speed, % speed used, % power used, thickness of acrylic, type of acrylic? I have cut tons of acrylic over the last 5 years and have honestly never seen that result. It looks as if the laser was out of focus and is melting the acrylic and it's solidifying around the cut. Check mirrors and lens for cleanness, ensure you are focused on the surface of the material, use air assist - transfer tape (or masking tape) might help.

Gary

Denver Shearon
01-13-2012, 4:29 PM
How about some more info - laser power, laser speed, % speed used, % power used, thickness of acrylic, type of acrylic? I have cut tons of acrylic over the last 5 years and have honestly never seen that result. It looks as if the laser was out of focus and is melting the acrylic and it's solidifying around the cut. Check mirrors and lens for cleanness, ensure you are focused on the surface of the material, use air assist - transfer tape (or masking tape) might help.

Gary


I am using a 40W machine and amd running 15%-25% Speed and 100% power. The acrylic is 3mm cast, I see the problem on clear and all colors but it is worse on the darker colors. I have tried with the stock masking, no masking and replacing it with a medium tack paper mask. I have cleaned all of my optics and am using air assist although it isn't the strongest. The focus doesn't seem to make much of a difference.

Denver

Neil Pabia
01-13-2012, 4:32 PM
Have you tried speeding it up a bit, that seems very slow for acrylic.

Denver Shearon
01-13-2012, 4:42 PM
Have you tried speeding it up a bit, that seems very slow for acrylic.

30% speed is about the quickest I can go and get through in 1 pass.

Frank Corker
01-13-2012, 5:27 PM
Well if that was happening on an Epilog I would adjust the frequency setting. If your 40 watt machine is an Epilog it should be 5000 for the frequency and you should use air assist. On other machines they refer to ppi. If you are getting raised edges it's probably because the laser is burning hot for too long and causing a distortion, you should increase the speed in 5's until you get it where it doesn't happen.

Denver Shearon
01-13-2012, 5:47 PM
Well if that was happening on an Epilog I would adjust the frequency setting. If your 40 watt machine is an Epilog it should be 5000 for the frequency and you should use air assist. On other machines they refer to ppi. If you are getting raised edges it's probably because the laser is burning hot for too long and causing a distortion, you should increase the speed in 5's until you get it where it doesn't happen.

I am using a cheap Full Spectrum Engineering chinese 40W with their Retina Engrave card. It is kind of a double edge sword. If I speed up the melting lessens bu the edges themselves are more jagged. It lloks like most other users with similar machines are using between 15-30 speed. I have not asked for thier thoughts on this yet.

Chuck Stone
01-13-2012, 5:54 PM
my question would be about the material.. are you sure it is acrylic?
Is there a brand name on it?
I cut a lot of it and haven't seen this problem yet.

Denver Shearon
01-13-2012, 5:59 PM
my question would be about the material.. are you sure it is acrylic?
Is there a brand name on it?
I cut a lot of it and haven't seen this problem yet.


Yes it is 3mm Cast Acrylic I purchased from Inventables.com. The decription says it is great for lasers.

Ross Moshinsky
01-13-2012, 8:43 PM
Get the acrylic off the table. That's most likely your issue.

Joe Pelonio
01-13-2012, 10:04 PM
Edge on top means too slow, jagged edge when sped up means not enough power. Your 40 watt machine should cut cleanly at speed 15 or less and 100% power. Check the artwork, make sure the lines are nice and smooth without additional points. If it looks good, then I'd try more air. Clear does cut easier than dark colors but with 1/8" you shouldn't have trouble getting through 3mm. You can also try removing the paper film, and replacing it with transfer tape, then mist with a water squirt bottle before cutting.

Rodne Gold
01-13-2012, 10:54 PM
You need to do a beam alignment and also check your head is perpendicular to the Y axis gantry. double check your focus point too.

Mike Null
01-14-2012, 7:29 AM
Denver

Please load the picture using the tools supplied in the "manage attachments" section of the response area.

Denver Shearon
01-15-2012, 2:44 PM
Get the acrylic off the table. That's most likely your issue.

I am using a honeycomb table, I have also just tried it supported up off the table.



Edge on top means too slow, jagged edge when sped up means not enough power. Your 40 watt machine should cut cleanly at speed 15 or less and 100% power. Check the artwork, make sure the lines are nice and smooth without additional points. If it looks good, then I'd try more air. Clear does cut easier than dark colors but with 1/8" you shouldn't have trouble getting through 3mm. You can also try removing the paper film, and replacing it with transfer tape, then mist with a water squirt bottle before cutting.

This was actually cut at 25% speed 100% power. This was just a simple .5" vector square. I have also tried with/without stock backing and replaced it with medium tack paper mask. I have not however tried misting the paper mask with water. I will give that a shot and see if it helps, thank you for the suggestion.



You need to do a beam alignment and also check your head is perpendicular to the Y axis gantry. double check your focus point too.

I think this may be the ticket I went through the alignment procedure again this morning. While I have the beam aligned for straightness it is entering the lens holder off center. I have the gantry shifted as far forward as it will go so I may have to move one of the mirrors.