Injection compression molding

Injection compression molding (ICM) is an innovative hybrid process that combines the advantages of both injection molding and compression molding. The main goal of this process is to reduce internal stress and minimize warpage, while significantly improving the dimensional accuracy and surface quality of molded parts.

Unlike conventional injection molding, the mold is initially not fully closed in the injection compression molding process. Instead, molten plastic is injected into the still partially open cavity. Only afterwards does a controlled compression movement close the mold completely, distributing the melt uniformly under pressure and compressing it into the final geometry. This method is sometimes referred to as compression injection.

Benefits of injection compression molding

Higher dimensional accuracy

The uniform material distribution during compression plastic molding reduces residual stresses and ensures extremely accurate reproduction of fine details – ideal for components with tight tolerances.

Less warpage and shrinkage

Due to the absence of a conventional holding pressure phase, the plastic cools under low stress. This drastically reduces the risk of warpage or sink marks – especially in materials with high shrinkage like POM, PET, PA or PBT.

Lower clamping force required

The process uses the machine's clamping unit more efficiently. This makes it particularly suitable for large or thin-walled parts where conventional molding would require excessive clamping force.

Reduction of internal stress

The lower pressure and uniform material flow result in low-stress components – a crucial benefit for dimensionally sensitive parts made from thermoplastics.

Superior surface quality

Injection and compression molding provides high-fidelity replication of fine surface textures, making it a preferred process for decorative or optical plastic components.

Typical applications of injection compression molding

Thin-walled or large-area technical housings
Optical and functional components in automotive or electronics
Precision parts and structural components with narrow tolerances

Materials for injection compression molding

The process is ideal for both standard and high-performance thermoplastics. Materials such as PEEK, PEI, or PPSU benefit from the gentle processing conditions of compression and injection molding, which preserve their mechanical properties and dimensional stability.

When to choose injection compression molding

We recommend injection compression molding whenever high-precision components made of thermoplastics require maximum dimensional stability, low internal stresses and perfect surfaces. The hybrid character of injection molding and compression molding makes it an efficient and economical alternative for producing high-quality plastic components – especially in demanding, large-scale or thin-walled designs.