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