Structural Foam Molding

Low pressure structural foam molding is a plastic molding process that uses nitrogen gas and/or chemical blowing agents to create parts with a solid outer shell and a lightweight, cellular core. This results in thick walled, strong, rigid parts that are lighter and use less material than parts made with traditional injection molding.

This type of molding utilizes low-pressure, multi-nozzle machines that include multiple barrels and injection points for each section of the part. Gates are large – about 5/8” in diameter.

Structural foam molding can also be done on standard injection molding machines using single-nozzle injection.

Unlike traditional injection molding, structural foam molding uses lower pressure and creates a foamed interior. This reduces weight and material usage, allows larger part sizes, and supports multi-cavity tooling for higher efficiency.

Structural foam molding is ideal for large plastic parts that need strength and durability – survivability is more important than lightweighting for most manufacturers. Common applications include pallets, bins, totes, enclosures for electronics and utilities, housings, and structural panels – essentially any large parts that will see harsh environments.

Compatible plastics include olefins and styrenics:

• Polyethylene (PE)
• High-density polyethylene (HDPE)
• Polypropylene (PP)
• Polystyrene (PS)
• Acrylonitrile butadiene styrene (ABS)

Some filled engineering-grade resins, including flexible materials such as TPVs and urethanes, can also be used for high-performance applications.

Yes. Similar to standard injection molding, structural foam molding supports deep draws, thick walls, and intricate geometries, making it suitable for custom designs in industrial and OEM applications.

With the right tooling, parts can be over 10 feet long and weigh up to 300 pounds. This makes the process well-suited for oversized or structural components.

Structural foam molding offers:

• Reduced manufacturing cost vs. standard injection molding
• Reduced material and part weight
• Consistent part quality shot-to-shot
• Design freedom
• Lower tooling costs (aluminum vs. steel)
• High stiffness and strength
• Minimal warping or shrinkage
• Efficient multi-part molding

You can make a large part in a smaller tonnage machine than with standard injection molding. In addition, by utilizing gang tooling, multiple parts can be made per machine cycle, so the energy usage and operational cost is lower. It also reduces material usage and discreet cycle times. Low-pressure requirements and multi-cavity tooling further drive down production and tooling costs.

Industries that benefit from structural foam molding include:

• Construction
• Material handling
• Packaging
• Water Management
• Consumer goods
• Appliances
• Utilities
• Industrial equipment
• Recreational products / Powersports
• Transportation
• Telecommunications

Yes. It produces less material waste and creates lighter parts, which reduce transportation emissions and energy use. Many parts are made with 100% recycled materials. It’s a more sustainable option compared to traditional injection molding.

Lead times vary widely by the project, part complexity, and tooling lead times – from 4 to 20 weeks generally. We will work with you to determine realistic, project-based delivery timelines so that you can plan accordingly.

We work with proven partners like 20/20 Custom Molded Plastics to ensure precision, consistency, and industry-grade performance in every molded part. They mold in the U.S., are the most experienced low-pressure structural foam molding firm in the world. They feature all new equipment, over 40 machines with redundant controls for ease of operation, tool handling expertise, and ISO certification.

Visit our contact us page or give us a call at 440-539-2433 to discuss your part requirements. We'll guide you through the process and connect you with the right manufacturing partner. If we can’t help you, we’ll connect you with someone who can.