Structural foam molding is an injection molding process whose injection stage is basically the same as traditional injection molding, but the packing stage is augmented by a chemical blowing agent mixed with the thermoplastic material to create thermoplastic foam. That chemical blowing agent is triggered by heat and expands the material by creating a microcellular structure to form the part against the mold.
The advantages of converting to structural foam injection molded plastics are just as varied as the many products that can be made successfully by this process. They include higher stiffness-to-weight ratios (parts made with structural foam molding can weigh 10 to 30 percent less than other parts, while retaining durability), lower material costs, lower tooling costs, smoother finished part surfaces for easy painting and cleaning, and a wide range of design flexibility.
Some common – and uncommon – products that have been successfully converted from traditional materials to structural foam injection molded parts include palettes for industrial and consumer use, a variety of lawn and garden equipment and supplies, car and truck door handles, sump pump tanks, surgical equipment and even more recently things like voting machine housing, screws and bolts, and even some concept vehicles.
Switching to structural foam injection molding can save costs at many steps along the way to your finished part. For example:
The lower pressure required for the process allows for cheaper aluminum molds
Recycled post-consumer plastics can be used in the process
Less scrap, but when you do have scrap parts, they’re recyclable and returnable to the supply chain
Lower raw material costs
Reduced part weight, which can result in lower packaging and shipping costs
If you’re thinking about converting to a lower weight yet high-strength part to save on production time and costs, structural foam molding may just be the right design choice. When you’ve made the decision to switch, it’s important to share as much detail as possible about your project with your injection molding contractor up front.
Some questions that you and your injection molding partner can answer together include:
Who and what is the part for?
What are the design goals and priorities?
Does the molding supplier have experience in the designing and molding of parts for your particular industry or end-use?
What factors go into the resin selection process? For example, are properties like chemical and environmental resistance, impact strength or electrical properties critical for your finished product?
What are the testing procedures at various stages?
Who will own the final part design and the tooling?
At Ferriot we actually recommend developing a project checklist that is shared between the designer, OEM and injection molding partner and referenced often to ensure understanding on the part of all stakeholders. In the end, all involved will appreciate the detail and heavy lifting up-front.
In Part 1, we discussed mold flow analysis (MFA) and the ways Ferriot uses it to improve the tool design process and, ultimately, the quality of the final custom injection molding we perform for our customers. In this ...