What's special about injection compression molding? The change in cavity volume during the injection or holding pressure phase. For the production of precise free-form surfaces, for example.
Only when there is melt in the cavity does the mold close completely or a compression stamp move forward. This means that a uniform pressure is exerted on the corresponding surface.
With injection compression molding, you can achieve larger flow path to wall thickness ratios and reduce shrinkage and warpage effects. For high dimensional accuracy and part quality.
What is particularly important for optical parts is that injection compression molding reduces internal stresses in the part as well as birefringence effects.
- Light testing
- Active breathing
Polarized light can be used to check the stress distribution in the molded part. For example, stress birefringence can be seen at the injection point of an injection molded part.
LED attachment lens
ARBURG is involved in the OptiLight research project: Injection-molded precise free-form surfaces purposefully direct the light of innovative hybrid optics into a rectangular illumination profile.
With thermosets, injection-compression molding can be used to increase part strength and avoid sink marks. For the belt pulley, the coining gap in the mold is 7 mm.
In opthalmic lenses for spectacles, the thickness of the part can be adjusted by means of the compression path. The coining time for a 10 mm thick lens is 90 seconds.