What is a compression mold?

Compression moulding is a versatile technique. Typically, the mould is filled with a synthetic resin with good wetting properties. This resin must be suitable for the specific material to be molded. It should also have appropriate viscosity to fill the mold cavity uniformly. It should also have the right curing speed to minimize by-products, and its volume shrinkage should be small. For composite molded products, the resin should also meet the exact requirements of the product to be moulded.

Compression moulding is most suitable for the manufacture of large parts that require significant volume. Unlike injection moulding, compression moulding has no weight limit for the parts. However, the injection barrel limits the volume of the mould. The advantage of this process is that it has low capital costs. Further, the process is flexible and can be automated.

Compression moulds are generally operated by hydraulic systems. They are necessary for the rapid movement of the mould and closure of the mould during the moulding process. Some systems use both high and low-pressure pumps to move platens rapidly. A typical system uses a combination of both types. This allows for a combination of low pressure and high volume to carry out the moulding process.

Compression moulds are commonly used for the production of composite parts. They improve the performance of the final part by pre-forming it. Once this is complete, the finished part is placed in a heated compression mould under high pressure. Typically, the pressure used during this process is between 800 and 2000 psi. Once the pressure is released, the resin flash is removed.

The process of de-flashing is usually manual or automated. The former is more common for larger molded products and is typically done for financial reasons. The latter is automated and uses ice blasting or water jets. Another option is vibration tumbling. The degree of flash removal will depend on the geometry of the parting line and the amount of product to be molded.

While injection molding can be more efficient than compression molding for producing complex plastic parts, it is still limited in its application and speed. In contrast to injection molding, compression moulding can produce composite parts with longer fibers and better mechanical properties. This allows compression moulded composite parts to be more structurally sound than metal parts and require less post-fabrication machining.

Compression molding is a practical and sustainable process, and the mold used is reusable for multiple cycles of compression. An expendable mold, on the other hand, should be discarded after every cycle. The process involves several key steps and a variety of materials. First, the charge is prepared, which involves preparing the material and changing its state.

Compression moulding is slower than injection and transfer moulding. The main difference is that injection and transfer molding involve the heating and pre-compression of plastic materials. This means that the parts produced with these processes are cleaner than parts produced with compression moulding.