Cutting High density Polystyrene foam.

[Rodne Gold]

Recently had a gent come to me and ask us to cut 2300 letters , about 2" high out of high density polystyrene , 1/2" thick. In one day!!
Its the stuff you see in bigger electronic boxes as packaging , a little denser tho.
Anyway to cut a long story short , the 12mm HD styren cut exceptionally well with not to bad a kerf width and little divergence on the sides of the letters.
Cut speeds with a 25w and a 2" lens were real fast. Not too bad a smell either and the lasers kept clean.
These letters were paragraphs of a speech and were being applied to a wall and painted , so they stood out in a subtle way.
So we not only had to cut the stuff , we had to keep the waste and the letters together so he could apply em easier. So we cut on a fine honeycomb grid and applied masking tape across the letters which kept the whole slab of styrene and letters together.

There are a LOT of applications for finer cutting of styrene which the hot wire cutter guys cant do. Speak to a few of em in your area and try work a deal where they send you the fiddly stuff.
Open cell foam works just as well , with that you can make decorative stamps, Mout the foam to a wood handle , apply paint and you have a great paint stamp.
I was surprised at just how well the polystyrene cut.

[Larry Bratton]

Rodne, that's very interesting. Did you accomplish the 2300 quantity in the one day?
How about Polyurethane foam? Seems I read somewhere that it is not laserable? I have used it for signs but always routed it with CNC. I made a big sign once (before I got my big table) out of cut out letters I made with my 16x24 Vision rotary machine. It's a very workable material for that purpose.

[Rodne Gold]

I've never tried polyurethane foams at all , in fact I've never seen the material.
Are you perhaps taking about a material called Kommatex (expanded PVC) ?
We cut all 2300 letters in one day , I have 6 lasers on my premises and we devoted 3 to the job , in fact we cut em all in 1/2 a day.
One thing I forgot to mention is that we focussed on the top surface and raised the table 1/2 the material thickness.
This is the polystyrene thats used for Casinos , hotels , film sets where they make those imitation architectural detials , sculptures etc by spraying it with a solvent that hardens the skin and then painting it to look like bronze/stone/marble etc.

[Larry Bratton]

Some companies refer to polyurethane foam as HDU (high density urethane) http://www.signfoam.com/product.php?mode=sf3 Mostly used for signs. Comes in various density. It cuts like butter with a router. Then it's primed and painted out with regular exterior paints. I don't use it much because it is expensive compared to some other substates. We use a product called Extira http://www.cmicompany.com/pageBuild.asp?PageID=B_ext_e for exterior signage. Inexpensive and very durable.
Wow, that's a lot of laser power. I suspect you did knock those out in 1/2 day. Just goes to show, you have to have the tools to do the work.

[Joe Pelonio]

Did we ever establish whether polyurethane foam is laser cuttable? I have someone sending me some to try, and possibly give me a good sized job (3/16" thickness). I checked the MSDS and there is no PVC/chlorides, and I found a website that shows it as "laser-friendly." If no one else has tried it I'll be the guinea pig next week.

These people are laser consultants and operators, and should know:

http://www.bostonlasers.com/index.php?option=com_content&task=blogsection&id=6&Itemid=18

[Larry Bratton]

Joe:
That is a very interesting site. I would be very interested to know your results cutting sign foam. Good luck! My guess is that it will cut no problem.

[Mike Null]

Joe;
If you have a chance, pictures would be very nice.

Here's another great reference site: http://synrad.com/search_apps/application_briefs/12-2.htm

[Joe Pelonio]

This is the 3/16" material. It's very flexible and translucent, almost rubber like.

After getting the setting nailed down to cut all the way through in one pass
(Epilog 45 watt speed 10 power 100% freq. 500) I find that the edges are sort of slimy/sticky. After sitting a few minutes it's better, but I'm not sure whether the customer will be happy with that. The actual parts are pretty detailed to have to clean unless a dip in soap and water will work. I'm waiting for him to let me know whether to proceed or not.

No flaring, no discoloration, just a little white smoke. Had air assist on.

Looking at the picture now that it's posted, it looks like there is discoloration around the edges on the top, but it's that residue, and does wipe off with my favorite citrus based cleaner if you do it right away. After 5 minutes it won't.

[Joe Pelonio]

My customer was very happy with the results from my laser cutting on the polyurethane foam.

I would not use it myself much, now that I see what it costs. Their supplier accidentally sent me the bill. It was $21.16 each for 6"x6"x3/16" piece!:eek:

[Larry Bratton]

That's the biggest reason I don't use it. Too pricey and not durable enough to suit me.