Bulk Moulding Compound (BMC) is usually injection moulded. But also injection-compression moulding in a tool / injection moulding machine is applied. Even SMC grades specially designed for injection moulding are offered by Menzolit to achieve a maximum in mechanical properties.

Injection-compression moulding means that the material is injected into a slightly open tool which is then closed and the part moulded. The process is an advancement of the injection moulding for the production of highly exact or very large construction units made of plastic. The mass cake injected into the practically pressure-free, not completely closed tool distributes much slower than within a closed tool. It is only closed during the solidification procedure completely. Thereby evenly developing the closing pressure provides for final forming out of the shaped part.

Basic requirements on an injection machine 

There are machines of all designs. The work routine on the closing side on machines with fully hydraulic closing system can particularly simple be steered. The work routine is programmable and can be adapted also during thermosetting polymer processing well on the process of transformation of the moulding material to the shaped part and the respective hardening characteristic. Fibre orientation arising with the spraying-casting process with fibre-reinforced moulding materials is partly waived when injection-compression moulding is used.
The process does supply shaped parts with very good surface and small mechanical anisotropy. Furthermore the necessary closing force is reduced, so that on a given machine larger construction units and/or be used for a given construction unit can be manufactured a smaller machine.

 With a variant the cavity can be filled completely. The rising internal pressure opens the tool around a controlled small way by raising of the closing force for pressure on the moulding material is exercised and a relatively tension-poor shaped part formed out.

The final compression of the BMC is here particularly favourable regarding the quality. Besides also wide or thick-walled construction units in optical applications e.g. boxes or isolators with the spraying embossing procedure are manufactured.

Injection-compression moulding of BMC is another way to fully automate the production process of large volume series of parts. The machine and its peripheral devices can handle material feed, moulding, de-moulding and often post-moulding operations easily.

Injection moulding