An Introduction to Injection Compression Molding (ICM)

As early as to 1960s, Japanese injection molding masters began to research on ICM. However, it was not well developed due to the limitations of machines and molds. In the 1980, injection machine and mold technology had a very fast development which is very good for injection compression development. Nowadays, it has become one of precision injection molding processes. The advances in CAE also help the feasibility of this special molding process.

Injection Compression Molding have properties of both injection molding fast, process can be easily automated and compression molding like thin wall and complex geometrical graphics with full details.

Types of Injection Compression Molding

ICM is further divided into following types:

1. Short-Shot Compression ICM
2. Full-Shot Compression ICM
3. Co-Injection Compression ICM

In short-shot compression molds is filled with 90 to 95 percent and in full-shot compression mold is 100 percent filled with material required for the product and then compression occur. Co-injection compression is little bit different from above two discussed in such way that injection and compression occur at the same time with little delay in compression.

Advantages of ICM

Injection compression molding (ICM) aside from reduced material shear and less orientation, offers numerous qualitative advantages for injection-molding parts. ICM also permits are duction in injection pressure, clamping force, and cycle time. Added to this is often an improved hold pressure effect, which minimizes sink marks and warpage.

Advantages of injection compression molding for the process

1. Compensates shrinkage by compressing the melt through the clamping movement
2. Distributed, uniformly acting holding pressure
3. Reduces holding pressure time, shortens cycle times
4. Permits over packing of cavity
5. Reduces clamping force requirements
6. Less orientation and molecule alignment during injection
7. Easier and faster mold filling through improved venting
8. Less material shear

Advantages of injection compression molding for molded part properties

1. Eliminates sink marks with thicker wall sections and at the end of the flow path
2. Reduces to warpage susceptibility improves long-time dimensional stability
3. Reduces stresses in mats or films in direct back injection for decorative parts
4. Reduces fiber degradation in parts made of long-fiber-reinforced thermoplastics (LFTs) and, consequently, improved mechanical part properties
5. Improves optical properties in the case of transparent parts.
6. There is a trade-off between the numerous advantages and the extra expense for the machine and mold as well as restrictions in terms of part geometry:
7. Undercuts or penetrations across the compression direction are problematic

Only components that are of very great depth in the injection direction are very difficult to produce by i