first time cutting acrylic and getting sawtooth linies

[Dann Ernstsen]

Hi Gentlemen and Ladies

I'm getting these sawtooth marks when I'm cutting acryl with the laser, normally it is used for fabric so this is the first time I see it. Whats wrong with the laser?

[Scott Shepherd]

What laser do you have? Make, model, power? What settings did you use?

It would be most helpful if you took a minute and edited your signature to include all the information about your machine. It'll make answers a lot easier.

[Dann Ernstsen]

Now I have editet my signatur. But it is a G.Weike Laser LC1612 singel head, 100w with a airpump and chiller 5000

The setting I used was for cutting speed 20 and power 70. hope this helps

[Scott Shepherd]

I can't speak for the Chinese machines, but I've never seen a Western machine that vector cuts at 20 speed (other than maybe in a straight line).

Someone with those machines will chime in and help, but I'd slow it down to 1/2 or 1/3, or even 1/4 of what you have and see if it gets better, if you're looking for something to do while waiting for someone else to answer.

[Bill George]

70% of 100 watts is a lot of power for something that thin, 3 or 4 mm? There are settings for slowing the speed down on a curve at least in my software. I am thinking like Steve/Scott do a little trial and error and do keep a log book.
On my 40 watt machine I cut 6 mm, at 95% and about 2 to 5 mm/Sec speed.

[Braden Todd]

The lines are the pain of working with acrylic!

I would try going much slower and check your vacuum/air assist to make sure it isn't to strong and cooling the acrylic to fast.

[Dave Sheldrake]

Heya Dann,

There are a few possibles....

Firstly try increasing power and speed, not by much and not in ratio. If that's 3mm acrylic (1/8") then try 22mm per second at 85% power, also reduce the air from the air assist, what's happening is the *heat* in the cut is being pulled / blown away by the air jet leading to the striations you are seeing.

DC lasers in general don't have the ability to vary the frequency (other than on some VERY expensive versions) so you won't be able to trickle around like the Western made machines do to get a good finish so you are left with combinations or air/power/speed to play with.

Braden above ^^^^^ was pretty much spot on right away, too much air..not enough heat :)

cheers

Dave

[Scott Shepherd]

Look at the photos closer guys, that's not air, that's speed. The top left has chunks missing. That's not being able to interpolate fast enough, not air.

[Rich Harman]

Look at the photos closer guys, that's not air, that's speed. The top left has chunks missing. That's not being able to interpolate fast enough, not air.

That could be flashback nicks from the honeycomb. I cut at 25mm/sec without interpolation issues - I don't remember what the limit is, I think it is higher than then "wiggles" limit.

[Dave Sheldrake]

I think Rich is right Scotty, they look like backscatter?

[Bill George]

That could be flashback nicks from the honeycomb. I cut at 25mm/sec without interpolation issues - I don't remember what the limit is, I think it is higher than then "wiggles" limit.
Or is it melted pieces coming off from to much heat? 70 watts on 3 mm acrylic is a lot.

[Scott Shepherd]

I think Rich is right Scotty, they look like backscatter?

That's a massive nick then. I've cut more acrylic than I can count and I've never seen chunks missing from flashback and it's no where else around it. Nicks from flashback are typically uniform around the work, in various places.

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[Clark Pace]

Of first off I'm guessing your are using cast acrylic. Black does a similar thing. Generaly you will notice small vertical marks, But those look kind of bad. Try cutting clear and see what happens.

Another problem would be be the acrylic it-self. You see colored acrylic has extras in it. So it's less acrylic. Depending on the brand of acrylic and the dyes they use can the flame polish look that we look for.

[Mike Lassiter]

was the part a bitmap image that you traced around for the outline to cut after raster engraving? A jagged edge from a enlarged bitmap image could give you the rough shape due to many unneeded nodes being in the vector circle cutout. If this was in face a vector circle you created and placed yourself then not likely. I have saw tracings of bitmaps produces extreme amounts of nodes that were hard to see unless zoomed in on where what appeared to be more or less a smooth line at normal size turned into a ragged mess when zoomed in on.
I think a close look at your vector line in Corel Draw might show the vector line itself possibly the problem.

[Dave Sheldrake]

That's a massive nick then. I've cut more acrylic than I can count and I've never seen chunks missing from flashback and it's no where else around it. Nicks from flashback are typically uniform around the work, in various places.

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It will be the bed rails brother, Chinese machines like the weike have single slat rails rather than a bed as such so flashback only tends to happen as the beam crosses them.

[Matt McCoy]

Are you able to adjust the import tolerance of your vector objects? If the edges look like an U.S. quarter, it might not be generating enough points.

The nicks look like flashback from the honeycomb.

[Kev Williams]

There's a setting in my lasersoft program called 'curve discrete length'--
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Now, since I can find no instructions anywhere as to what this means, I kinda figured that making the
distance smaller from the .100 default would maybe mean that it would tighten up the resolution of
the curve, giving me a smoother curve. So I moved the slider left about half-way--

What actually happened was, while etching outlines with a 3/4" radius on a black anodized panel,
the machine tried to run the curves at full speed. The stepper motors did NOT like this, and would
hang, and stay hung during the straightway run until the hanging motor had to change direction-
the hanging was inconsistent, and also happened while I wasn't looking. Each outline is 12 passes, x4
corners-- I had lines etched from hell to breakfast. Ruined a $225 operator panel...

SO, I moved the slider about 1/3 the way to the right of center. I'm not on that computer so I don't know
the actual setting, but doing so DID slow the curve speed down, quite a bit from the default setting...

It works pretty well so I haven't changed it.

That all said, I haven't found lasers to be all that great at cutting nice smooth circles...

As for the OP's machine, since he's been cutting fabric, I wonder if he might have some buildup
in the belt teeth & drive cogs?

[Scott Shepherd]

It will be the bed rails brother, Chinese machines like the weike have single slat rails rather than a bed as such so flashback only tends to happen as the beam crosses them.

I still disagree with that. If it was the air, then I would be able to emulate that by air pressure. I can't. I can go no air or full blown air and every where in between and never get results like that. If it was air, every one of us should be able to replicate it and I don't think we can. That's a speed/motion issue. Something is set wrong or something is loose in my opinion.

[Neil Pabia]

What is the frequency you are cutting at? I max out my power and frequency for acrylics and it seems to work fine, I just run it at a slower speed.

[Dave Sheldrake]

What is the frequency you are cutting at? I max out my power and frequency for acrylics and it seems to work fine, I just run it at a slower speed.

DC tubes don't have variable frequencies on Chinese machines Neil :)

Biggest difference between Chinese and Western machines is the resonator, RF give much more control over the process and can give very nice polished edges, DC don't, you can get a decent edge but no where near the quality of a western box :)

[Dann Ernstsen]

I had a go at it again last night, and I think it is mainly a mechanical problem. So I will try to fix that, thanks for all the input from you guys. The project is on hold until i get time to look at the mechanical side of the machine.

Thanks to you all for your help, this has been very helpful