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Makin Signs from Foam

Makin Signs from Foam

Postby keith » Sun Feb 21, 2010 9:17 am

I have seen on a number of sites that people are using CNC ROUTERS to carve large signs from light weight foam materials like Polystyrene and then cover the finished sign with some sort of sealent or something which is designed to protect from the Polystyrene from the weather and knocks, bumps etc. Does anyone know what would be used in this fashion? This would be another great application for our machines.

The Titanic was built by professionals; the Ark was built by Amateurs..........
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Makin Signs from Foam

Postby Awesomeness » Sun Feb 21, 2010 5:47 pm

I'm not sure what you mean by "Does anyone know what would be used in this fashion?". Are you asking what would you use a foam sign / cut foam for?

In college, I designed and build an 8' tall version of my fraternity's crest out of foam. It was made from several layers of 2" foam, so it is very 3D. It was made by hand then, but could have been easily done by a CNC router. We painted the foam with exterior house paint.

I intend to use my CNC router to make foam Halloween decorations, like tombstones for my front yard. Someone involved in theater, prop making, or cosplay/costuming would also love detailed CNC cutouts (from foam, or other materials).

You can also cut things from foam, to use as forms to fiberglass over. The nice thing about foam is that it is relatively cheap in large volumes. You can use it to make, or provide a base shape/form, for large things that you couldn't make out of more expensive materials. I could imagine making things like a boat hull out of foam, then fiberglassing over it.

The possibilities are pretty endless.

If you don’t have time to do it right, when will you have time to do it over?
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Makin Signs from Foam

Postby keith » Sun Feb 21, 2010 5:56 pm

Sorry for not being clear enough... What I mean is that once the sign/oblect is made from foam it is then effectively "SKINNED" in a material to protect it from the elements and bumps and knocks. This is the sort of thing I am trying to find out about. Do you mean that what I am looking for is just fibreglassing over the Polystyrene? I thought it would "MELT" if it came into contact with fibreglass. Also if it was fibreglassed wouldn't some of the detail be lost?

The Titanic was built by professionals; the Ark was built by Amateurs..........
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Makin Signs from Foam

Postby cgjeff » Sun Feb 21, 2010 9:23 pm

Correct, you don't want to be using polyester fiberglass directly over polystyrene foam. It will eat the foam away like nobody's business.

What you want to be using to reinforce the foam is either an epoxy based fiberglass resin resin (check local boat shops), or you want to be using any urethane resin (www.smooth-on.com)

Either epoxy or urethane resins will soak into the styrofoam and create a very strong surface. without needing any further reinforcement like fiberglass.

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Makin Signs from Foam

Postby Awesomeness » Sun Feb 21, 2010 11:46 pm

I've used epoxy fiberglass resin on top of foam. It doesn't create a strong surface AT ALL, without fiberglass reinforcement. Resin alone is very brittle.

When applied over foam, it creates a smooth surface, but is about as delicate as egg shell. If you're using closed-cell foam (like blue/pink foam from Home Depot) it also WILL NOT soak into the foam at all. It will bond to the surfce, because it's rough. This can actually cause an issue because the resin will chip off, in use, and just pull the foam surface off with it.

Yes, if you coat foam with fiberglass, or other materials like vacu-formed styrene, it will reduce detail.

The best method is probably to do some coating/smoothing work on the foam, then make a mold.

If you don’t have time to do it right, when will you have time to do it over?
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Makin Signs from Foam

Postby graph4sure » Mon Feb 22, 2010 3:21 am

Hey Keith,
In the Signage Industry we use a product for Large and small signs
called: SIGNFOAM. It is really HDU ( High Density Urethane ) it comes
in 4x8 sheets and larger and from 1/2" to several inches thick.
You can google it or try my supplier: Harborsales.net - in the mid-atlantic
states. Also there is a hard coat that can be applied, basically it is a
2-part epoxy ( resin & hardner ) like West Systems Epoxy is what we use.
It carves very smooth and there are a couple different densities. It is a
closed cell urethane that was first developed by NASA.
Hope this helps, Tom Bogley

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Makin Signs from Foam

Postby Awesomeness » Mon Feb 22, 2010 4:30 am

Good info.

For those who are interested, it isn't cheap.

Here's some examples...
4' x 8' x 1/2" 18LB. DENSITY $169.23 ea
4' x 8' x 1" 18LB. DENSITY $275.30 ea
4' x 8' x 2" 18LB. DENSITY $506.95 ea
4' x 8' x 4" 18LB DENSITY $960.49 ea

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Makin Signs from Foam

Postby mikeusnret » Mon Feb 22, 2010 4:54 am

couldn't one use the blue foam that is found in the building industry at such borg places like Lowes and Home Depot etc?

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Makin Signs from Foam

Postby graph4sure » Mon Feb 22, 2010 5:43 am

Guido,
You sure are right about the steep pricing, esp, on SIGNFOAM.
There is one other HDU manufacturing firm in California that makes
the same type product , called: PRECISION BOARD.
Like you stated, all the same densities and sizes. It is not top grade because
the closed cell structure is larger with more voids - and thus they sell a special
filler/primer to level out the surface. The cost is not extemely less
but it is reasonably less expensive.
Again, it is distributed by: Harborsales.net
They typically only sell to Sign Companies. But a local sign shop
that does dimensional signage would probably get it for you.
- Tom Bogley

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Makin Signs from Foam

Postby graph4sure » Mon Feb 22, 2010 6:02 am

Michael,
In the Signage Industry we do use the BLUE FOAM from Lowes or Home Depot for
cutout letters and graphics. And the really cool way to protect them is with Spray
Polyurethane finish. And what this basically is, is: Truck Bedliner finishing protection.
You know, the hard shell that either comes from the factory or - there are
companies now that specialize in this. So you can take your cutout foam and they
can spray on any number of colors and textures. It is rock hard. We sometimes add
a 3/4" MDO Plywood backer - if it is freestanding.
Try to google: Truck Bedliner or Polyurethane Spray. I guarantee you have a firm
near you that does this service.

Also, thanks again Michael, for the information on my KL 4030 Dip Switch settings.
- Tom Bogley

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