In-mold compression
Craftsmanship introduction
In-Mold Compression (also known as Injection-Compression Molding) is an advanced plastic molding process. Its core principle involves maintaining a specific compression gap (typically 1-20mm, adjusted per part) between the mold halves during initial clamp-up.A precisely measured volume of plastic melt is first injected into the cavity. As the melt begins to cool and shrink, the mold is fully closed, applying an external mechanical force to compensate for the material shrinkage, thereby producing a final product with high dimensional accuracy and low internal stress.
This process is specifically designed to address the challenges of molding large and complex components. It is particularly suitable for:
■ Large-sized curved parts (e.g., automotive sunroofs, quarter windows)
■ Thin-walled components
■ High-precision optical lenses
■ Various engineering plastic products requiring minimal internal stress and high dimensional stability.
Technical advantage
■ Reduced Cavity Pressure:
Significantly lower required cavity pressure compared to conventional high-pressure injection, which helps protect the mold and reduces machine requirements.
■ Reduced Molecular Orientation:
The melt is compressed to fill the cavity rather than shear-filled, effectively minimizing the directional alignment of polymer molecules.
■ Lower Residual Stress:
The lower injection pressure and uniform compression process fundamentally reduce internal residual stresses in the molded part.
■ Reduced Differential Shrinkage:
The compressive force ensures more uniform packing throughout the cavity, greatly minimizing defects caused by uneven shrinkage.
■ Lower Birefringence:
For transparent materials, low molecular orientation and low internal stress directly result in reduced optical birefringence, enhancing optical quality.
■ Overcame Warpage:
Uniform shrinkage and low internal stress work together to ensure superior flatness and dimensional stability of the product.
■ Minimized Density Variation:
The density distribution throughout the part is more uniform, ensuring consistent performance.
■ Improved Dimensional Accuracy:
A combination of the above benefits ultimately achieves high and stable dimensional precision in the final product.