Thomas Catinat, Operations Manager at Broanmain Plastics, explores the lasting legacy of compression moulding, including the application advantages of this technique.
Broanmain Plastics
“For stronger and more wear-resistant parts produced in lower volumes, compression moulding and direct screw transfer (DST) remain extremely valid and popular options,” observes Thomas.
For sectors like aerospace, automotive, transport, utilities, marine, electronics and renewable energy, compression moulding is undergoing a bit of a resurgence. This is mainly attributed to these industries using more advanced composite materials.
In many instances, compression moulded parts are more durable as a result of the tensile strength. Parts can also be more sustainable as bio-based materials are increasingly being used. Valued globally at USD 12.4bn in 2023, the compression moulding market is projected to double to USD 25.1bn by 2032i.
The compression process
Compression moulding is a forming method that relies on heat and pressure to mould plastic materials. The first step involves creating a strong, precise metal tool that is designed to the required dimensions and shape.
A compression moulding machine places partially heated material into the open, heated mould cavity. Broanmain offers compression moulding using Bulk Moulding Compound (BMC). This composite is a polyester ‘dough’ material that is manually put into the tool in pre-measured amounts.
The mould is closed with a top force or plug member, and pressure and heat are applied to ensure the material reaches all parts of the cavity. The part is cured until the material sets into shape. Finally, it’s removed from the tooling where it’s trimmed down. If intricate details are required, these are often created on a CNC mill.
DST is a hybrid of compression and injection moulding. It allows for the processing of thermoset materials such as epoxy, phenolic, DAP, alkyd and DMC in an injection moulding machine. Although more time is needed to change the equipment components and barrel, automation can significantly accelerate the process.
“Although more labour intensive than injection moulding, where the compression method is beneficial in shaping highly durable parts with significant thickness, the compression moulding tool makes stiff and high-durometer plastic materials perfectly vulcanised and dimensionally stable. It still works best on smooth surface parts that don’t have complex geometries,” adds Thomas.
Despite the strong outlook, accessibility to UK moulders with the capabilities and capacity to offer compression moulding and DST alongside mass injection moulding has fallen significantly. “It’s a process that Broanmain has continued to invest in.
To adapt to our customers’ delivery needs and to ensure knowledge of this traditional technique is retained for future generations, most Broanmain machine operatives are trained in both compression and injection moulding,” reports Thomas.