Structural Foam Injection Molding
Manufacturers seek light, strong, and cost-effective plastic components. A solution is structural foam injection molding, which is becoming a popular alternative plastic injection molding. The foam molding process mold parts geometries and flow lengths that traditional molding cannot handle.
The Foam Molding Process
In structural foam molding, the base resin is blended with a chemical blowing agent that activates under the heat and pressure introduced during processing. As the resin melts, the blowing agent decomposes and releases gas (typically nitrogen), creating a uniform cellular structure within the material. This creates a controlled foaming effect as the material is injected into the mold. In some cases, base resins are specifically formulated for foaming without compromising material properties. As the material expands within the mold, it effectively packs itself, replacing the need for traditional mechanical packing pressure from the injection machine.
A wide range of materials can be used in structural foam molding. While many resin suppliers offer grades designed specifically for this process, standard resin grades can also be successfully utilized. CVG provides support in material selection and testing to ensure optimal performance and desired material properties after sampling.
Traditional Molding vs. Structural Foam Injection Molding
With structural foam molding, a chemical blowing agent that generates nitrogen gas is typically blended with the base resin before melting. This process creates a gassing and foaming effect as the material is injected into the mold. In some cases, the base resin itself is specially formulated to foam without compromising material properties. As the material expands within the mold, it naturally packs the cavity, which eliminates the need for high mechanical packing pressure. This results in reduced warpage, lower tooling stress, and improved dimensional consistency.
Use Structural Foam Molding for Large Parts
Using a blowing agent in the process increases the flow length of the material as it’s injected into the mold. The resulting parts are lighter in weight, which is especially beneficial for large components. Additionally, the process minimizes molded-in stress, producing parts that are highly resistant to warping or twisting while enhancing overall strength and durability. It also significantly reduces the clamp pressure required to keep the mold closed during processing, allowing parts to be produced on lower-tonnage presses and helping to reduce overall manufacturing costs.
This means structural foam molding is ideal for parts in the following applications:
- Powersports and recreation – Roofs, hoods, body panels, cargo beds, and floor sections
- Construction and agriculture – Exterior covers, interior panels, fenders, and access doors
- Telecommunications – Antenna housings, junction boxes, and equipment cabinets
- Energy storage and battery housing – Large protective cases or frames for battery modules
Benefits of Structural Foam Molded Parts
Structural foam injection molding offers a range of benefits for manufacturers. It provides significant weight reduction, increased stiffness, and lower molded-in stress, which helps to minimize warping or twisting. The process also enhances design flexibility, allowing for longer flow lengths from the gate.
Because structural foam molding operates at much lower pressures, tooling costs can be reduced, and molds are often made from aluminum rather than steel. The process also uses less material than standard solid polyurethane reaction injection molding, further reducing costs and improving thermal transfer for faster processing and cooling times.
Additionally, structural foam molding allows greater freedom in design features such as rib-to-wall ratios and helps eliminate sink marks on the “A” surface, even when bosses, walls, or other features are present on the “B” side. Last but not least, the gas bubbles formed inside of molds during the foam molding process offers thermal insulation and sound deadening.
Partner with AdvancTEK
AdvancTEK is your premier plastics manufacturing partner with over 35 years of industry experience.
We use advanced processes to deliver structural foam molded parts of all sizes, utilizing a wide range of base materials and chemical blowing agents to meet performance requirements. From start to finish, you will see excellence in our processes. Regardless of the size of your project, our team will take it on and work to ensure success. Allow us to use innovation and our expertise to turn your project concepts into a reality. In addition to structural foam, we also specialize in gas-assist and insert injection molding solutions.
FAQs About the Foam Molding Process
How much weight reduction can we expect?
The answer to this varies questions depending on the material selection and final property requirements of the part. As a general rule, a reduction of 10- 30% could be expected.
Will the resulting part look like a straight injection molded part?
The answer to this is usually no. There is some inherent cosmetic swirl on the surface of the part and reduced gloss. This can be improved with some processing adjustments and with some specific chemical blowing agents designed for improved surfaces, but not completely eliminated. Often structural foam is used for non-cosmetic parts or parts that will be painted or otherwise coated.
Contact Us Today to Get Started!
AdvancTEK is ready to bring our structural foam injection molding expertise to your project.