What is Structural Foam?
Structural foam is a low-pressure form of injection molding, which utilizes most thermoplastics, (including post-consumer regrind), to mold rigid product, which can have thicker walls and higher stiffness-to-weight ratios than standard injection molded product.
In the structural foam process, a physical or chemical blowing agent is mixed in with the resin. The resin is shot into the cavity, but not completely filled or packed out. The blowing agent expands to push the resin to the extremities of the cavities. As the part cools, the internal pressure of the foaming action takes up the internal shrinkage, and reduces sinks over ribs or heavy cross-sections.
What are the advantages of the Structural-Foam process?
There are many advantages of the structural foam process which combine to provide an economical advantage over other processes, and allow production of parts which can’t be matched by any other process. Following is a list of many of the advantages of the Structural-foam process:
When should the structural foam process be considered for a part?
What does a part molded with the structural foam process look like?
A product molded utilizing the structural foam process will typically have a surface which appears to have swirls on it. This is due to the internal “foaming action”, in which some of the small internal bubbles come to the surface of the part. A cross-section of a structural foam molded part will show a cellular internal core sandwiched between two solid wall sections.
How much weight reduction can be expected by utilizing the structural foam process?
The amount a part is reduced in weight by utilizing the structural foam process is dependent on many variables including part configuration, wall thickness, material type, and processing. However, a reduction of 10% to 20% is common.
Why is aluminum tooling utilized in the structural foam process, and what is the life expectancy of an aluminum mold?
Since the injection pressures in the structural foam process are relatively low, the use of aluminum tooling is prevalent. Aluminum tooling provides superior cooling over steel, while the aluminum tooling can be built quicker and more cost effectively than a steel tool. As with any tool, the life of a tool depends on the molder and the care taken with the tool by the molder. An aluminum tool will last as long as a steel tool if it is taken care of. There are many examples of aluminum tooling running in excess of a million parts.