So I found this cool new foam at a local arts/craft store that is used mainly in the automotive industry (For car bumpers), It is ultra stiff and rigid and dents about as easily as light ply. The one problem. It doesn't come in sheets its a 2 part liquid that you need to place in a mold. So I bought some and to play around with making molds and how this stuff reacts I made a 5.5 inch B2. File is setup for milling from 1 inch foam but I think you might get away with .5 inch but double check. For the first run I used vaseline as a release, That was a mistake as the foam didn't react correctly (I ran a test in a cup prior). I cleaned out the molds with denatured alcohol and tried some commercial mold release. I pulled those out this morning and the foam came out all soft. I am not sure if this is from being in the molds all night or a reaction to the mold release. Additionally one casting concaved in the middle. This might have been from not being filled enough/reaction to release. so much more experimenting left to be done. but here are a few pics for now

Attached files B2 6 inch model.zip (4 MB)Â

 

Thats the stuff i got was going to peruse their site at lunch today

 

Thanks for the Link Mark. It gave me an idea to try for a release

 

Well Thanks to the link Mark sent I looked at parts of the site I would have otherwise skipped. This lead me to find that using a silicon based release agent with the foam is a no no. I looked at the product they were selling for a release agent and besides being hazardous to ship it was some kind of wax based release. As my wife did candles for a stint and still has lots of parafin wax around. I melted some and brushed it onto the molds. I did another casting again and the foam set correctly but I had a bunch of wax all over the parts that I now needed to get off. I boiled some water stuck it in that and while it melted the wax it just redistributed over the parts. It also made the parts soft and bendable for a time. Tried a heat gun next. That was a big NO NO made the parts crack and bend again. Kinda predictable in afterthought. But anyway I manged to crack one of the molds by putting the clamp to tight. also need to recast the parts. I think the next round I will use the parafin wax again but instead of brushing it on I will rub the mold so it is a thinner layer and hopefully not effect the final product as much.

 

I never worked with the paraffin wax but can you buff it after you've applied it? If it comes out shinny there is less chance for the foam to stick to it. I used to use Turtle wax when I made fiberglass parts. Two three applications and buff it in-between with a buffer. Three is better than two, if you are not lazy.