Issues laser cutting foam.

[Keith Upton]

I'm trying to laser cut some pretty dense foam that is backed with pressure sensitive adhesive and am having some problems. I've got a 60w Epilog Mini 24 and the settings I've found that give me the best cut are Speed 18, Power 100, and 5KHz. It cut really well and give a really smooth wall. But the problem is that the two parts melt back together if they are not pulled about with in seconds of them being cut.

This is the type of foam I'm using:

http://www.wingsofwar.org/forums/attachment.php?attachmentid=116919&d=1385916864

But this is one of the many shapes I'm cutting out of it:

http://www.wingsofwar.org/forums/attachment.php?attachmentid=116922&d=1385916866

The final product has a total of 12 shapes cut out of it, so it take several minutes to cut the entire thing. Any thoughts on what I can do settings wise to either create a bigger kerf between the two parts so that they can't melt back together? I've got a 1.5, 2 and 4 inch lens. I've tried both the 1.5 and 4 in and out of focus. The 4" gives me flare up on the PSA backing regardless being in focus or not.

One other bit of info that might be helpful, I'm cutting these with the PSA up as doing them with the PSA down seemed to cause a lot of heat build up above the PSA, in the lower section of the foam.

What do you guys and gals think?

[Mark Sipes]

just a thought.

1) would freezing (dropping the temp) of the foam prior to lasering help harden the 2 surfaces faster.

2) Increase Air flow at a point after cutting to cool weld surfaces.

3) Possible to use a different blend of foam?



Video of Tool Foam Cutting.... http://www.youtube.com/watch?feature=player_detailpage&v=wu56Szwxwnk

[Keith Upton]

Mark,

1) I had thought about freezing the foam first, but was not sure if that would be bad for the laser/lens or not?

2) Not sure how I'd do that... splice into the air assist line and put a second line on it to blow behind where it just cut?

3) Might end up having to go that rout, but would really like to stick to the foam I've selected. I did try tool foam as you can see in my photos above. But that was only at the Epilog factory and we only cut one shape out at a time testing the settings (so there was never time for it to melt back together if it wanted to).

[Michael Hunter]

When I cut thick foam (30mm, 1.25") I set the focus point about 1/3 the way into the material (the autofocus plunger almost scrapes on the foam).
That and good air assist gives me a good cut for 99.9% of the time.
Just very occasionally if the foam is thin or stressed it will move and close the cut before the melt has solidified.

[Keith Upton]

Thanks for that Michael. What type of foam are you cutting?

[Matt Turner (physics)]

Could you defocus to get a wider kerf so the pieces can't stick back together?

[Michael Hunter]

Keith -

LD29. Looks similar to yours, but perhaps not quite as dense as the one you have your finger on.

[Keith Upton]

I tried that as well Matt. Defocusing does give a wider kerf, but I lose my tolerances and it flares up quite a bit... melting it even more.

[Keith Upton]

Keith -

LD29. Looks similar to yours, but perhaps not quite as dense as the one you have your finger on.

If google turned up the correct foam that you are using, it's actually quite a bit different that I'm trying to using.

I used to have the made out of that type of foam back before I bought my own laser:

http://www.wingsofwar.org/forums/attachment.php?attachmentid=118404&d=1388544518

But I wanted to get a denser foam for more protection and one that was not porous to grab the little detail bits of the models they hold. Here is the new foam to compare to that photo above....

http://www.wingsofwar.org/forums/attachment.php?attachmentid=118403&d=1388544517

Note that the new foam does not have the backing piece in that photo like the old style, so it will be even more sturdy when it does.

[Dan Hintz]

I'd suggest increasing your air pressure quit a bit... you'll likely have to increase the power (or slow it down, in your case), but it should freeze the foam the moment you cut through, preventing it from welding back to itself.

[Keith Upton]

Dan, I'm running my air assist at 25psi right now and the Epilog says a max of 35psi (I think, don't have the manual in front of me). Would that be enough and what concerns would I have using a higher air pressure?