Injection moulding large plastic products is a manufacturing process that has been around for decades. In this article, we will discuss one of the latest developments in the industry: structural foam moulding.
In recent years, injection moulders have worked with engineers to develop new materials and techniques to create lightweight yet strong parts with complex shapes. In other words, there are no longer any trade-offs when it comes to weight or strength.
Structural foam moulding was used for things like boats and car hoods in the past. Because of its strength and lightweight properties have become a popular option in many different industries, including aerospace manufacturing.
Injection moulders can still use structural foam to create lightweight yet strong parts. In addition, they now have the option of using traditional materials such as PVC and polycarbonate, which are very durable but also incredibly heavy. Over time, this could revolutionize many different industries that rely on injection moulded plastics.
To understand how this process works and why it is so beneficial, we need to break it into two major parts.
Let’s take a look at each of these steps below.
Step 1: Preparing the Part for Injection Moulding
To ensure the part will be durable enough for structural foam injection moulding, it must be made from a material with high compressive strength.
Preparing the part for injection moulding is relatively straightforward. We must first make sure the piece is designed so that there are no undercuts or thin sections where the material will be trapped once injected into the tool. If this does occur, it could cause damage to the structural foam and/or screw and barrel, resulting in costly repairs and/or replacements.
To ensure the part is designed correctly, we strongly recommend working with an experienced engineer to produce a 3D model. There are no undercuts or thin sections where the material will be trapped once injected into the tool.
Once the part has been designed, we will need to create a sacrificial gate on all walls surrounding the cavity to be spray bonded together later on. This is done by hand with a scalpel or knife, followed by chamfering around the edge of the gate with a tapered burr.
Step 2: Structural Foam Injection Moulding Process
There are three major parts to the structural foam moulding process :
The first step in the structural foam injection moulding process is injecting your resin. Unlike traditional materials, there is no need for cooling lines since the part will be cold when it comes out of the tool. So, you can either use a cold runner system or make sure the resin has cooled enough before injecting.
This is where you will inject your foam into the powder cavity. You will need to ensure that your part does not contain any undercuts or thin sections so that there is no trapped material. This can damage the screw and/or barrel, which will result in costly repairs.
Once the part has been packed, it is time to eject the structural foam from the tool. Depending on application requirements, you can do this by manually pulling it out or using a pusher system.