Direct injection expansion molding

Direct injection expansion molding

How Direct injection molding works

Direct Injection Expansion Molding (often referred to as DIEM) is a more specific molding process related to expandable bead molding but with its distinct methodology. It’s a process that combines the benefits of thermoplastic injection molding with the weight-reducing properties of foam materials. This technique is especially popular in automotive applications, such as making lightweight foam-filled parts like door panels, bumper cores, or instrument panels.

1. Process:

The process begins with the injection of a molten thermoplastic (often filled with a blowing agent) into the mold cavity. This initial phase is quite similar to the traditional injection molding process.

Once the thermoplastic material fills the mold, the heat within the mold causes the blowing agent within the thermoplastic to start decomposing. This releases gas, causing the molten plastic to expand.

As the plastic expands, it forms a foam structure. This foam structure has a solid skin on the outside (due to contact with the mold walls) and a cellular foam core.

After the foaming process, the part is cooled to solidify its structure.

Once the part has cooled and solidified, it’s ejected from the mold.

2. Advantages:

The foamed core allows for significant weight reduction compared to solid injection molded parts. This is especially valuable in industries like automotive manufacturing, where weight savings can lead to better fuel efficiency and reduced emissions.

Unlike processes where foaming and molding are separate, DIEM allows for the creation of foam parts in a single integrated step, making the production process faster and more efficient.

The combination of a solid skin and a foamed core offers a balance between rigidity and weight, leading to parts with good structural properties.

The foam core provides good thermal and acoustic insulation properties.

Reduced material usage (due to the foam core) can lead to cost savings.

3. Applications

As previously mentioned, the automotive industry finds significant value in DIEM for producing lightweight, rigid, and insulating components. However, other industries can also benefit, especially where there’s a need for structural components with insulation properties or weight concerns.

4. Summary

In summary, Direct Injection Expansion Molding is an innovative molding technique that leverages the benefits of injection molding and foaming to produce lightweight, structured parts efficiently.

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