Cant cut cleanly through black acrylic

[Troy Shaffer]

I cut most 1/8in acrylic with 2 passes at 35% speed on my 35w laser. But black seems to be a problem, I tried more passes, lower speeds. and it cuts right up to the bottom paper and gives me a preferation of sorts. I can snap it out with a rough edge, but dosen't cut clean through. I have been leaving the paper on the top too. Didn't think it'd make that big of difference. I even tried focusing deep into the material. Any ideas?

[Mike Null]

Troy

Are you cutting on a grid elevated above the table? Is your material flat and in focus? Try increasing your PPI or hertz.

[Frank Corker]

All acrylic is clear when it is being made. In order to get black and colours they introduce other incredients. This is why you are having more problems with it, it will need more power to cut through it.

[Chuck Stone]

I know black is going to cut slower because of the absorption. Gray does too.
I typically cut 1/4" clear at 0.7 speed (1 pass, 100%) and the black is about 0.5
speed for the same th

[Troy Shaffer]

Yes its elevated. I've tried different focuses, generally for cutting I focus on the middle of the material. I've tried focusing all the way through and in the middle. At this point I've nearly exausted my supply of black. If I reorder translucent black instead of opaque will it cut easier. Troy

[Larry Allred]

What exactly are all your setting? DPI, Frequency, speed, power...
When did you last clean the lens and mirrors? Tried auto focus compared to manual?

I cut 1/8" black at 600 DPI 15% speed 100% power 5K Freq, in one pass and it comes out clean. My laser is a little hotter than yours so you'd go slower or twice, but it should work.

[Scott Shepherd]

What machine do you have? I can't cut through 1/8" black with 75W at 35% speed. That's WAYYYY fast for vector cutting.

[Gary Hair]

I cut most 1/8in acrylic with 2 passes at 35% speed on my 35w laser.

You are trying to cut it way too fast. I have a 30 watt machine and cut 1/8" at 1.2% speed. My laser is 40 ips in vector, so I'm cutting at about .48 ips. For a 35 watt machine that cuts about the same speed, I would think you should be very close to mine. I use air assist and it cuts perfectly clean in 1 pass. I have cut smoked acrylic and it needed a bit less speed, maybe .9% or 1.0%. I cut 1/4" between .6 and .8, and even cut 1/2" at .1 - all in one pass. Slow it down, use air and it should work fine.

Gary

[Joe Pelonio]

Every machine is different, even with the same wattage rating. Still, I would think that something is wrong when a 35 watt cannot cut 1/8" in one pass while a 45 watt (mine) will cut 1/4" black at speed 6, 1/8" at speed 12. Have you checked mirrors and lenses, and are you using air assist?

[mark anizan]

My 35 watt Epilog Mini 18 will cut 1/8 in black acrylic at 22 speed 600 dpi 5000 clean in one pass .
mark

[Ross Moshinsky]

Black acrylic should be cut easily with a 30W unit. We've cut it several times. I forget the speed but it's relatively slow. I want to say somewhere between 8 and 15. 35 speed wouldn't even get half way through probably.

[Dee Gallo]

I cut through 1/8" black acrylic with 12 speed/100 power/5000 freq. with my 35w Epilog. You are trying to go too fast, as mentioned by others. If I used the same settings with lower frequency, it would not cut all the way through, as Mike, Larry and Mark suggested.

[Troy Shaffer]

Ok I feel foolish. I had questioned leaving the paper on top. I'd been cutting mirrored that didn't have paper on both sides. took off the top layer of paper and went through it no problem. Thanks guys.....

[Dee Gallo]

Wow- what kind of paper is THAT?

[Michael Kowalczyk]

just 1 question and then an FYI. Question is that I see several posters above that use DPI as a setting for vector cutting. My understanding, at least on my Trotec, is that DPI has nothing to do with the settings for vector cutting and only makes a difference when rastering/engraving. Is DPI used differently on other lasers? PPI or Hertz are the ones that make the difference. and the FYI is that there is a huge difference in Black and White materials. For instance we made a prototype, on one of our CNCs) several years ago out of Sintra material. We used the exact same router bit, same toolpath, same vacuum hold down same everything. We made the 1st one out of white Sintra and it cut like butter and was very quiet. Then we cut the exact same prototype in black Sintra and it was a little bit nosier but it was a NIGHTMARE. The toolpath caked up with the cut material and re-welded itself in place. We have never cut it since (have not been asked to either). We also paint the edges of 1000's of parts each month and the white paint goes on good as does the black paint but the problem is cleaning it up after. The white comes off the edges with little effort but the black does not dry the same and is always more time consuming. Both paints start with the same base. it is only the color additives that are different. So we always charge more for black material but have not had any issues with black acrylic. We have cut black cast acrylic and have had no issues.

[Larry Bratton]

just 1 question and then an FYI. Question is that I see several posters above that use DPI as a setting for vector cutting. My understanding, at least on my Trotec, is that DPI has nothing to do with the settings for vector cutting and only makes a difference when rastering/engraving. Is DPI used differently on other lasers? PPI or Hertz are the ones that make the difference. and the FYI is that there is a huge difference in Black and White materials. For instance we made a prototype, on one of our CNCs) several years ago out of Sintra material. We used the exact same router bit, same toolpath, same vacuum hold down same everything. We made the 1st one out of white Sintra and it cut like butter and was very quiet. Then we cut the exact same prototype in black Sintra and it was a little bit nosier but it was a NIGHTMARE. The toolpath caked up with the cut material and re-welded itself in place. We have never cut it since (have not been asked to either). We also paint the edges of 1000's of parts each month and the white paint goes on good as does the black paint but the problem is cleaning it up after. The white comes off the edges with little effort but the black does not dry the same and is always more time consuming. Both paints start with the same base. it is only the color additives that are different. So we always charge more for black material but have not had any issues with black acrylic. We have cut black cast
acrylic and have had no issues.

I was about to look that up..I'm with Michael,since when does the DPI setting have anything to do with vector cutting?
I have been cutting some 1/8" black CAST acrylic the last couple of days. I have suffered some inconsistency in what it took to get through it. I didn't worry about it much realizing that cast is manufactured in a mold unlike extruded and subsequently has some variation in thickness. Extruded, being made by drawing through a die is very consistent and I get more consistent cutting results

[Joe Pelonio]

On the Epilog and some others it's not DPI but Frequency that is adjusted depending on material, for acrylic I use the maximum frequency of 5000. I have found that some cheap black from Indonesia does not leave the usual glossy edge, but still does cut in one pass with the same settings.

[Larry Bratton]

On the Epilog and some others it's not DPI but Frequency that is adjusted depending on material, for acrylic I use the maximum frequency of 5000. I have found that some cheap black from Indonesia does not leave the usual glossy edge, but still does cut in one pass with the same settings.
Yes, I also use 5000 frequency on acrylic vectors. I get an edge that is really smooth. I have run into that stuff from Indonesia. The product I was cutting was Chemcast, made in Mexico which I have used in the past and found it to be a good product.

[Stephen Hooper]

My 35 watt Epilog Mini 18 will cut 1/8 in black acrylic at 22 speed 600 dpi 5000 clean in one pass .
mark

I also have a mini 18 35W and black acrylic is no problem at 5mm thick in one very slow pass.