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Introducing the Structural Foam Molding Design Guide

By July 29, 2019September 11th, 2023No Comments

Although it is similar to standard high-pressure injection molding, structural foam molding is unique and offers designers and manufacturers distinct advantages. The most notable is the size and scale of the molded parts that can be produced with structural foam. Single parts, up to 72”x72”x24” and larger are achievable.

Another basic difference is structural foam molding uses low pressure molding instead of high pressure.  Also, the finished molded material has a cellular ‘foam’ core with a smooth solid outer surface that is extremely durable, rigid and impervious to weather.

Other benefits of structural foam include:

  • The density reduction of the cellular ‘foam’ core makes parts that are 10% to 15% lighter in weight compared to ordinary injection molded plastic.
  • Large sized and complex parts can be molded without sink marks.
  • High strength-to-weight ratio compared to other materials and production methods.
  • Large platen presses that can hold multiple tools and mold multiple parts simultaneously.
  • Low pressure molding allows for the use of aluminum molds which reduce costs
  • Recycled post consumer plastics can be used for many products.
  • Plus many more benefits that can improve product design, production and costs.

With all the advantages it offers, structural foam molding is definitely worth considering for many products. This is the reason we’ve created the Structural Foam Molding Design Guide.

The free guide provides and overview of this versatile manufacturing process, its strengths and uses.

Specifications and illustrations throughout.

Some of what you will find in the guide includes:

Multi-Nozzle Molding Overview

The platens on these large presses have many inlets where multiple injection nozzles can be used during molding. The guide explains this technology and the opportunities it delivers.

Gas-Assist Molding Overview

This process introduces inert gas during the molding cycle to assist the material flow. This improves the cosmetic finish of the large-sized molded parts. The basic principles of gas assist and how it can be applied to your designs are covered in the guide.

Design Considerations, Tips and Specs

The bulk of the design guide is filled with specifications, best practices and other useful information to keep in mind or refer to when planning and designing for structural foam molding.

Here is the Table of Contents from the guide:

Process Overview

  • What is structural foam?
  • Advantages of structural foam
  • Single-nozzle molding
  • Multi-nozzle molding
  • Gas-assist molding


Industries and products using structural foam


Plastic materials compared

Design Considerations

  • Wall Thickness
  • Material Flow
  • Transition Sections
  • Radii and Filets
  • Tolerances & Warpage Control
  • Draft Angles
  • Bosses
  • Ribs
  • Design Tips


  • Self-Tapping Fasteners
  • Press-In Inserts
  • Snap-Fits

Secondary Operations

  • Decorating
  • Warehousing & Distribution
  • Painting

Structural foam molding is just one of the full range of North American made custom molding services that Miles Products supplies its customers.

We hope this design guide will help you discover the benefits that structural foam molding can bring to your products. And, we believe you’ll find the information it contains beneficial when working on your next project.

Want to download the design guide and read it for yourself?

Macay Hunter

Macay Hunter

An expert in plastics manufacturing, Macay works with engineers and supply chain managers during the planning, design and implementation stages of their molded plastic productions.