How well do you/does your laser cut PMMA?

[Steffen Heidemann]

Hi,

i was wondering..

before i bought my laser in the first place i read/heard a lot about how well lasers cut PMMA - and how well the edges are supposed to look.

I have always been relatively happy + convinced by the final results my laser produced ever since.

Anyway.. a few days ago i was shown a sample of some laser cut PMMA by a salesman from another manufacturer - images attached. He claimed nothing else but laser cutting was involved, no flame-polishing etc.

Anyway.. how well do your edges look when you cut PMMA? Is it similar to the samples attached and am i simply doing something wrong?

IMO those look really good.

Best, Steffen

[Mike Null]

Your pictures are results far better than I can get. Those edges look polished or flamed to me.

[Jon Colley]

Most lasers should be able to achieve edge quality like this on straight edges providing they have enough power, but it takes CAD/CAM software to achieve edge quality like this on curves. It provides a level of control that is not possible through a print driver interface.

We provide our TroCAM software with our largest system, the Speedy 1500, but it can also be purchased separately for use with any of our systems. I recommend it for any acrylic cutting application.

I'm not sure which system you are running because you don't have it in your signature line. I can tell you that any Trotec system with 60W or more using the TroCAM software can achieve this quality level.

[Steffen Heidemann]

Interesting, thanks.. my own results show much more 'steps' as well.

The salesman argued the difference is also buried in their software..

I honestly do not remember the samples the Trotec sales person showed me before i bought mine - but somehow i think to remember they looked different from those samples by Eurolaser..

[Steffen Heidemann]

Thanks, Jon. I am sorry, did not put it into my signature yet. I run a Speedy 100 30W from AdobeIllustrator via the Printer driver and JobControl.

The aspect about TroCAM i have not been told until now :) Interesting, thanks!

[Dan Hintz]

Steffen,

Without some final flame polishing, I call BS...

[Gary Hair]

Steffen,

Without some final flame polishing, I call BS...

I'm inclined to agree with Dan. I get a nice clean edge with my laser but nowhere near that clean. If it's possible with a laser, I'll buy the laser and software tomorrow!

Gary

[Frank Corker]

That edge has definitely been finished after the event. It's been flame polished for sure. Picture two and picture three, the right hand side, both have some distortion on the top of the 'polished' edge. Look closely and you will see slight bevelling caused by heat.

[Greg Bednar]

<snip>

Anyway.. a few days ago i was shown a sample of some laser cut PMMA by a salesman from another manufacturer <snip>


The "shown a sample" as opposed to "he gave me a sample to try on my laser" is enough for me to have EXTREME doubts about it.

[Doug Griffith]

I call BS as well. There is a slight curvature to the edge as if it's been polished.

[Scott Challoner]

I call BS as well. There is a slight curvature to the edge as if it's been polished.
Could that rounded edge be caused by focusing into the material? That would make the beam wider along that edge and give it that rounded look. I usually focus into acrylic. I'm not backing anybody up. Just sayin'.

[paul mott]

Don't know if this helps the discussion or not but this is typical of the results I am getting using a 40mm FD lens.

Paul.

[Rodne Gold]

Striations on curved and even straight edges arent caused by bad software - caused by melt ejection , air pressure etc etc. I also think those edges are too good to be true for a "straight out a laser" application

[Steffen Heidemann]

Thanks, guys..

My conclusion so far would also be.. interesting, too good to be true.

The manufacturer in question argued to come by and watch a live demonstration though. If i find the time i might have to take him by his word ;)

Anyway, some images of the typical edge quality would be great - at least to me. I will upload some of my results when i get back to the office later today.

CAD/CAM software vs. printer driver is an argument that could make sense up to this point.. guess i will at least look into that.

[Dan Hintz]

Steffen,

Paul's image a few posts up is more realistic... you don't get the perfect "window clear" view through the edge right out of the machine. Not to say that flame polishing takes any real amount of time on simple designs, but it is a separate step that needs to be accounted for...

[Lee DeRaud]

CAD/CAM software vs. printer driver is an argument that could make sense up to this point.. guess i will at least look into that.It's a matter of where the conversion of points on the curve's path to machine X/Y motion commands is done. If it's done in the laser itself, it will be as good as anything a CAD/CAM software can put out. If it's done up in the computer by the printer driver, it's depends on whether it's done to the limits of the laser's motion system or to some coarser coordinate space.

[paul mott]

Hi,

i was wondering..

before i bought my laser in the first place i read/heard a lot about how well lasers cut PMMA - and how well the edges are supposed to look.

I have always been relatively happy + convinced by the final results my laser produced ever since.

Anyway.. a few days ago i was shown a sample of some laser cut PMMA by a salesman from another manufacturer - images attached. He claimed nothing else but laser cutting was involved, no flame-polishing etc.

Anyway.. how well do your edges look when you cut PMMA? Is it similar to the samples attached and am i simply doing something wrong?

IMO those look really good.

Best, Steffen Hi Steffen,

I think the salesman was telling the truth here. It is perfectly possible to obtain edges like the sample you have shown. I was not certain until I had done it myself but now I know it can be done.

Paul.

[Greg Bednar]

Paul, do you have a closer shot perhaps with a macro lens? I'm not doubting you, I'd just like to see a closer view. I was a doubter until you said you tried it yourself. So sorry for that - But a closer view of the edge if possible would be great. It would cut down on a lot of post production time.

[paul mott]

Hi Greg,

No worries, I do fully understand your apprehension. When I first saw the Eurolaser foot I thought it had been reworked too, exactly the same as everyone else.

This is the closest photo I can get (don't have a macro lens) and I can assure you that there are no visible striations. Looking at the edge through a magnifier reveals signs of striations, so they are still there just not visible to the naked eye.

It is my opinion that If a machine allows you to cut acrylic in straight lines without vertical striations then it will allow you to cut curves without vertical striations - the trick is going to be finding out how. The curved surfaces on this foot are not really curves they are just many straight lines which approximate a curve.

I need more information on printer drivers and the type of info they accept - please anybody.

Paul.

[Lee DeRaud]

I need more information on printer drivers and the type of info they accept - please anybody.Assuming we're talking about Windows, it's not rocket science. The application sends the "print" data to the driver using a Windows Enhanced Metafile (EMF), which is essentially a binary representation of a set of GDI calls. The feature set includes everything you'd want or need for the laser (or a CAD/CAM system for that matter); you can get the full specification here (http://download.microsoft.com/download/a/e/6/ae6e4142-aa58-45c6-8dcf-a657e5900cd3/%5BMS-EMF%5D.pdf) (warning: it's about 8MB). Whether a given feature is implemented in the hardware, emulated by the driver, or simply omitted, obviously varies wildly from one device to another.

Corel can export EMFs directly: some hacking will reveal that it implements circles (ellipses, actually) as a set of four polybeziers, one for each quadrant. Relevent to this conversation, the device driver for a ULS VL200 then converts that to a polyline, still more-or-less in EMF format; for example, a 2" diameter circle becomes a 128-segment polyline. (I have no idea how the higher-end ULS machines do it.)

[paul mott]

Lee,

Thanks for the info, It is eye-opening just how many variations the EMF format will allow.

From what you have discovered about the print driver the way forward may be to avoid curves and circles which automatically get strung into poly-lines by the software and try to fool the print driver by only feeding it straight lines. (after all the machine will only move in straight lines, excepting the rotary axis of course :) ).

If it is possible to cut a straight line in acrylic without producing any noticeable vertical striations then it is also possible to cut a circle (comprising many straight lines) again without any noticeable vertical striations.

I suppose the question to ask here is:-

"Why are we not doing this" ??.

Any ideas welcome.

Paul.

[Lee DeRaud]

If it is possible to cut a straight line in acrylic without producing any noticeable vertical striations then it is also possible to cut a circle (comprising many straight lines) again without any noticeable vertical striations.Huh? What's the difference between (1) the vertices between the polyline segments and (2) the "vertical striations" you've been complaining about?

(There's the additional question of whether a given combination of firmware and motion system actually can cut a straight line in acrylic at arbitrary angles to the axes without vertical striations. As both Rodne and I have pointed out, there is more than one mechanism in play here.)

[paul mott]

Huh? What's the difference between (1) the vertices between the polyline segments and (2) the "vertical striations" you've been complaining about?To save repeating stuff I think I have explained this (best I can) here.
http://www.sawmillcreek.org/showpost.php?p=1491973&postcount=45


(There's the additional question of whether a given combination of firmware and motion system actually can cut a straight line in acrylic at arbitrary angles to the axes without vertical striations. As both Rodne and I have pointed out, there is more than one mechanism in play here.) Others laser machines and their capabilities are beyond my knowledge / experience but Rodne has said that he has discerning customers who are pleased with his cut acrylic items so It must be possible to obtain a good surface finish.
It would perhaps be helpful to see others pictures of their cut acrylic items.

Paul.