Understanding the Injection Molded Foam Process - pt. 1
Posted by Nancy Grossbart
When my company (MDI Products) first began to work with product designers who wanted to create a foam product and had lots of plastic molding experience, it was very difficult to get them to "think differently" about how to design a product that took advantage of our
injection molded foam process. There are only some things about both processes that are similar. Both plasticize raw materials in a hot barrel. Both inject in the materials into a closed mold. Pretty much the similarity stops there.
Understanding the fundamentals is key to designing a great part. To really comprehend what is happening, you need to first know that injection molded foam is actually a foam manufacturing process which manufactures foam in the shape of your part.
The next area to understand that, unlike the single mold plastic process, the machines used in the injection molded foam process are multi-station presses, which utilize multi-molds.
Again, unlike plastic injection, the mold cavities are designed smaller than the final part size. The parts expand rather than shrink. The amount of expansion is dependant on the material softness you require.
The material remains in the heated mold during the cross-linking or cooking process. The cooking time is dependent on the thickness of the part. The mold opens very quickly when the cooking is complete. The part expands and explosively self ejects from the mold cavity. The part is removed from the mold station and set to cool.
Learn more about self-ejection, draft, corners, edges, and undercuts later.
