Trouble with detail vector cutting through acrylic

[Joel Matteson]

Hello everyone,

We have been working with a lot of acrylic lately and are attempting to do some detailed cutting of monograms. They are small, approximately 1.5 inches x 1 inch and we are using a 'vine' type font that results in very thin pieces that need to be cut out of the acrylic. We've tried both 1/8" and 1/4" Cast acrylic and these fine pieces melt and deform if not vanish all together.

Is this a matter of the optics we have (basic 2.0 that came with the ULS 4.6) or are there some tricks we can play with the settings to reduce the melting? We did try multiple passes with reduced power but the result was not much different. If it is an optics issue, would the ULS High Power Density Focusing Optics make a big difference in the amount of detail we can cut?

Thanks for the input!
JM

[Joe Pelonio]

You have simply gone beyond the limits of what can be done with a laser. When the beam cuts and then passes too close on the next cut the plastic will melt. Even if it worked, the pieces are too fragile to work with. You have to choose your fonts/logos and sizes carefully.

[Joel Matteson]

Joe,
That was exactly what I said when we were struggling with it. Then I started googling the topic and came across this picture of a snowflake laser cut out of acrylic. Of course there were no details on how it was done. The lines we are trying to cut are not any thinner than this example. If we could cut this, then we could pull off the monograms we are working on. I'm only guessing, but looking at the size and thickness of this snowflake, had we cut it using our ULS settings, the thin straight lines would certainly have melted.

Here is a link to the post I was looking at:
bostonlasers.com/laser-cutting-blog/bid/52664/Tis-the-Season-for-Laser-Cut-Acrylic-Snow-Flakes

[Scott Shepherd]

Joel, my suggestion is to go into Corel and change the colors around. Make it 2 or 3 color outlines. Don't put the same color next to each other. The heat from cutting the same lines next to each other can cause problems. If you can make it cut one line, move to another part of the piece, and cut something else. So essentially, it'll cut, move to another area, cut, move to another area, cut, then change color and come back to the first area, cut, move, cut, etc.

What you're doing is using the color mapping to make it cut sections further apart than it normally would.

I did a job like that recently and when not skipping around, it was frying the material bad. When skipping around, it cut clean and looked fine and stayed flat.

I hope I said it clear enough to understand.

[Rich Harman]

Did you try turning up the air assist?

[walter hofmann]

Hi
I think first you have to clean your mirrors and the lense,adjust your beam that it is dead center on all four corners of the table.
then make the line test ( meaning: a piece of wood on the table and lay on one end a piece of 1/2 inch) then engrave a line.
after this look where the line is the thinnest, measure the distance from the laser head to the material there thats your foacal
distance and for detailed cutting essential must be hold around all four corners of your table. people dont believe how much this
brings. I cut 1/8 acrylic with my little machine 40W at 25mm/s power 25 to 30 % or 10 to 13mA
greetings waltfl

[Mike Null]

I would suggest reducing your power and your ppi and making more than one pass if necessary. Others have said it--you may have a drawing with lines so close and fine that it takes too much heat to cut in one pass. There is no need to consider a shorter lens.

Next question, can you make do with 1/16" instead of 1/8"?

[Wes Reeve]

I think Scott has the solution to this one. I cut custom acrylic pickguards pretty often and I've found that allowing the material to cool, even for a few seconds will make a huge difference, it just takes some thought to make the artwork work properly for your piece.

[Joel Matteson]

Hi Scott,
I completely understand what you are getting at, but this is taking three letters and welding them all together with a border, so I'm not sure how I could then break that up into separate colors.

[Dee Gallo]

I don't know how much help this is, but I cut out a heart made of little hearts a while ago and the 1/8" acrylic is pretty thinly cut. I just used my usual settings (12sp/100p/5000fr), air assist at 10psi. Maybe your design has the lines too close together and a little tweaking will help. You don't mention your settings, but sometimes a small change in speed makes a big difference. For instance, I might cut something else from acrylic with a slower speed of 8 or 10. It's difficult to imagine what you have in mind, but I have a hard time thinking the pieces are any thinner than this.

cheers, dee

[David Fairfield]

All good ideas here. 1/4" acrylic is pretty thick for the sort of cutting you see in the snowflakes. They appear to be cut in thin acrylic, which cuts very nicely, but its a very brittle material more suited for solid shapes. Those snowflakes would probably not survive a drop on a hardwood floor or mailing in a padded envelope. They are beautifully made however, and tree ornaments are traditionally fragile.

There is no reason you shouldn't be able to cut something like this on your machine. If you intend your monograms as jewelry like necklace pendant, try wearing one yourself a few days and see if it survives car seat belts etc.

Dave

[Scott Shepherd]

Hi Scott,
I completely understand what you are getting at, but this is taking three letters and welding them all together with a border, so I'm not sure how I could then break that up into separate colors.

Covert the font to curves and then break the curve apart (arrange, break curve apart).

It would look something like this, with all 3 colors having the same settings.

colormap.jpg

[Glen Monaghan]

The end segments of the two thin inner curves that are green on both sides should be split into different colors (green and red, probably) to avoid cutting both sides together and risk melting the segments.

[Scott Shepherd]

True Glen, about the time I was doing this, I got a "hey, I think I have a virus on my computer" interruption. Not the best thing to hear. Once I got all that straight, I just published it where I left off, hoping the concept would be understood, but you are exactly right, that's a better way.

[Richard Rumancik]

Covert the font to curves and then break the curve apart (arrange, break curve apart).

Joel, Scott has the right idea but I'll elaborate a little . . . I assume you already have a closed curve as you are welding letters together. In any event you need to make it into curves. Once that is done, select the outline, then select a node with the shape tool in CorelDraw and right click. Select "break apart". (This breaks the curve at the node.) Then select the other end of the segment you want to isolate. Again, right click, "break apart". Finally do the arrange -> break curve apart. (This breaks the whole curve into separate pieces, at the selected nodes.) Now the selected segment is fully detached and you can change it's color.

You may still need to sort your vectors by moving them front or back on a layer so they cut in the required order. Usually we sort so vectors close to each other cut together, but you will do just the opposite to avoid the heat build up.