Machining foam

[Rookie machinist]

Has any body here ever machined any type of foam? I want to make some prototype parts out of foam and was wondering if anybody here has done it. I want to be able to have a smooth finish after machining. Also does anybody know of sources for small quanties?
Thanks,
Steve

[tattoomike68]

Grizzly sells machinable wax.

http://www.grizzly.com/products/H9039

As far as foam ,Here is an outfit that sells rods, sheets, and tube.

http://pleiger.com/rst.html

they might be worth giving a call.

[oldtiffie]

Cutting foam

Use a hot wire or an electric kitchen 2-blade oscillating/reciprocating 2-blade bread/meat knife.

A jig-saw works pretty well too.

Check out/ask at your local rubber/foam store.

[winchman]

Do you mean something like the Styrofoam found in coolers and insulation? It machines well on a milling machine using small cutters with sharp edges at very high speeds.

The electrostatically charged dust is atrocious.

You might be able to do some parts with a hot-wire foam cutter.

Roger

[Mike of the North]

Styrofoam

Do you mean styrofoam, my brother works at a pattern shop that make one off patterns for lost foam casting using a foam cutting cnc machine, it uses spacial cutter but does produce a smooth finish, so it can be done, a cutter designed for soft material run at high speed should work, if it is simple flat profile a hot wire could be used.

[Alan Smith]

Big disc sander can be used to very good effect.

[Swarf&Sparks]

google lost foam casting, there's a wealth of info out there

[Evan]

It's possible to create complex shapes other than flat surfaces using hot wire foam cutting. For instance, a hot wire moved though a slowly rotating part will create a helix. I have also made aircraft wings that are both swept back and tapered to a different airfoil at the tip compared to the root complete with washout. A very handy device is a hot wire band saw with a hot wire in place of a blade.

[gellfex]

Has any body here ever machined any type of foam? I want to make some prototype parts out of foam and was wondering if anybody here has done it. I want to be able to have a smooth finish after machining. Also does anybody know of sources for small quanties?
Thanks,
Steve

As many have asked, are you talking about Styrofoam or a professional industrial design urethane modeling foam? I've used several types of the latter, the best being very expensive filled foam stuff called Obo Modulan. The density range is similar to wood. I use 40 lb, that is 40 lb/cu ft.

http://www.obo-werke.de/English/Product.html

It works like a machinists wet dream, with little dust and sands to a smooth finish.

[Rookie machinist]

I am interested in any foam that can be machined to a smooth finish. I think hot wire cutting may also be an option for me.

Mike of the north, do you know what type of foam and cutters you brothers shop uses? Or what machines they are using?

Evan have you ever seen designs cut with a hot wire?

My first projects only involve simple shapes but I plan evloving to more complex shapes which I don't think hot wire cutting can handle. Right now cost is an issue so I would prefer a product that won't hurt the wallet too bad if the design does not go as planned.

Thanks for all the help guys.

Steve

[gellfex]

Look, when I worked as a modelmaker for advertising we used foam in all sorts of ways, in combination with all sorts of materials. If you really want help you need to stop being coy and get more specific about what you're doing. Don't describe your precious "idea" but describe the scale and shapes you want. A hot wire cut might look perfect for an object 3' high but sucks for an object 3".

[wierdscience]

We had a customer that used a cnc gantry to hot wire sign letters out of 1" foam.

It didn't use a wire though,instead it used basically a big soldering iron fitted with a 1/16" diameter carbide rod for a tip.

They also used a lot of this stuff-

Carvable high density sign foam

http://www.signfoam.com/product.php?mode=sf3

[Rookie machinist]

Sorry gellfex was not trying to be coy. My intention is to create molds for gfrc/gfrg precast parts. I would like to cast the mold around the foam. The companys in my area all cast their parts from hand made mold which tend to be inaccurate. I have installed theese parts for years and the biggest complaint we get is that the parts don't fit correctly. I am hoping to make precision molds and either supply them to the local precast company or start making my own products.

[gellfex]

Sorry gellfex was not trying to be coy. My intention is to create molds for gfrc/gfrg precast parts. I would like to cast the mold around the foam. The companys in my area all cast their parts from hand made mold which tend to be inaccurate. I have installed theese parts for years and the biggest complaint we get is that the parts don't fit correctly. I am hoping to make precision molds and either supply them to the local precast company or start making my own products.

My Dad repped a Canadian company for years, Formglas, that made such parts. Domes, column covers, cornices, etc. I don't think a thermoplastic wire cutting foam will give you the accuracy or finish needed for some of those applications. You really want them to be ready for paint after the installation holes are filled. Unless you want to make a mold from a foam model, pull a gfrg positive and do finish work on it before pulling a final mold from it, I would say the model needs to be machined or fabricated from sturdier more accurate materials like dense engineering foam or stable wood products.

I suspect the problem with the existing suppliers lies with the original models being made by carpenters rather than machinists. They have a whole different attitude towards accuracy, as anyone who's ever put a level or square to a newly constructed home can attest.

[Rookie machinist]

You hit the nail on the head gellfex. What I plan on doing is making the mold from the model. The molding process is my final step. I know most engineering foams are pricey, but I think if I can cast better parts I will be able to compete. I have also thought of using machined mdf for the model. Thanks for your input.