[Spezzaferro]

Does anyone know about the requirement of a mold that is used for the manufacture of expanded foam products ,such as seat cushions and the like?
do they have to be made of aluminum, or can they be made from high density tooling board. also do they require venting for escaping gasses?
I used to be involved with making blow molds, so molding is molding, but im pretty sure these molds would be quite simple to manufacture.
can any one help, or suggest a link for info.
Thanks

[7feet]

Sorry for replying to such an old thread. Most of the molds for polyurethane foams that I've made (especially for larger parts) have been epoxy/fiberglass molds. I'm not sure about the tooling board. One of the things you need in this type of mold is to create some degree of backpressure on the expanding foam so that the foam will skin properly at the surface. Very small vent holes in areas where air might be trapped are a good idea, 1/16" should generally be sufficient, not affecting the backpressure much or allowing lot's of foam out of the mold. It depends on the size of the mold, but if it's not too large just the pour spout should be enough to moderate the backpressure, it really varies a lot depending on the shape and thickness of the piece and the volume of foam you are pouring.

It can create an awful lot of pressure if you pour too much foam in the mold, so it's pretty important to know what the volume of the final piece is. From there, it's not hard to calculate how much foam you need. For a rough example, your pieces volume is 10 gallons. The foam expands to 8 times it's liquid volume. So 1.25 gallons of foam (mixed) should exactly fill the mold. But you want a little backpressure, and sometimes depending on temperature and humidity variations the foam may not expand exactly to spec, and I'd usually add perhaps 5-10% more foam to make sure it fills and skins properly.

Most of my experience with the stuff has been for casting pretty large skin sections for animatronics. But I've also done plenty of smaller pieces in ultracal or Forton MG molds. It's not a super critical thing. Almost anything that is reasonably strong and rigid should work.

[maquiza]

I am planning on doing some parts in molded EPS (expandable polystyrene). I will be doing the aluminum molds and also I am planning on doing a small molding machine for my parts.
I will use these parts for Lost Foam Castings, but if this works, I will find some costumers for packaging products.
If anyone can give me some pointers, it will be appreciated.

[rkonnen]

I want to know where you get to foam beads and how do you make them heat together.

[miljnor]

me too!

[CNC Pro]

I have a supplier that produces expandable polystyrene components. As explained to me, the beads are processed by exposing them to steam, the density of the finished component is varied by the amount of steam & heat.

[rkonnen]

Well here is some info http://science.enotes.com/how-produc...yrene-foam-epf

[plasticbaldy]

Did you find a source of information or gain your own experience in molding EPS ? I have a similar project and am trying to find answers regarding pressures that the mold must withstand, temperatures etc etc. Please help if you can or please direct me to an expert that you might know.

[miljnor]

These guy's are balls deep into the EPS molds thing.

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