How to Make a Mold for Foam Casting

So, you want to get creative and make a foam casting mold. There are many purposes for creating molds from making movie props, building toys, to making footwear, furniture, even automotive and construction equipment or just simply replicating family heirlooms.

Practically any design can be custom casted in foam with the correct processes, tools and materials.

Let’s look at some of the materials you can use, as well as a ‘how-to’ guide to building your own reusable mold for foam casting.

Molding Compounds

•         Silicone rubber
•         Resins and epoxies
•         Concrete or plaster
•         Soaps and waxes
•         Different types of foams

Types of Molds

•         1-part mold (for single dimensioned items with flat surfaces)
•         2-part mold that you can put together and pull apart (for fully shaped items such as duplicating a wheel, tools and toys. Basically, anything with two sides to it)
•         3-dimensional molds (for shapes with an internal cavity, such as hollow chocolates and sculptures)

# For this article we are going to make a 2-part mold using silicone rubber as the molding compound and wood to build the mold framework. We will create a solid mold that will be cut into two parts.

Step-By-Step Guide to Creating a Foam Mold

1. First and foremost, remember to wear your PPE (Personal Protective Equipment) when handling chemicals, cutting tools and other equipment.
2. Ensure the item you wish to mold is completely clean and dry.
3. Use wood to create your molding frame or box. Wood is more solid and will prevent bulging of the mold. You can choose to use a round measuring cup or jug as well. (The same principles below apply)
4. Create a square box-like shape that will be the outline of your mold. (Should you choose to use the cup, no changes are required. Simply ensure it is the correct size to fit your composite in, leaving adequate space above for silicone to fully cover it.)
5. Apply releasing agent to the item and inside of the mold. This will ensure the silicone is easily removed.
6. Glue or weight your item to the bottom of your frame and support with small pins if necessary to prevent it from moving during the pouring process. (Ensure the item is at least ¼ inch away from either side of the frame)
7. Follow silicone mixing instructions and remember to remove all air bubbles from the mixture before pouring. (A vacuum de-airing process can be used if necessary.)
8. Carefully pour the silicone mixture into the frame over your molding item.
9. Cure overnight.
10. To de-mold, simply break the box of your frame apart, clean off any excess silicone and cut clean lines of even thickness down either side of the middle of your mold to separate into two parts before removing your finished product.

Helpful Hints for Foam Casting and Molding

•       Always mix slightly more molding compound than you would normally need to ensure you don’t run out mid-pour.
•       Always remove air bubbles no matter what compound you use.
•       Allow enough time for the mixture to set or cure.
•       Purchase materials from trusted vendors and always follow instructions.

Obviously, this process cannot be replicated at scale. If you are creating a one-off item, creating your own mold like this can save a bit of money (however, you’ll likely find the quality of the finished product is not particularly professional). If you have an item you need mass produced, or molded to professional specifications, call 1.888.202.2052, or email jason@jcadusa.com and let’s have a chat about your project!

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You might also like to check out our article covering how to create plastic molds, or our article on creating silicone molds for baking and other kitchen purposes. You might also be interested in learning about our short run manufacturing services.