Advantages of compression moulding

Companies come up with all sorts of excellent theoretical designs for plastic components. Often, these designs make it all the way to the press and into early prototypes. And then they fail.

That’s because the type of plastic or the moulding process wasn’t appropriate for the part’s application.

Compression moulding, however, is your go-to option when you need strong, durable, heat-resistant plastic parts. It’s not necessarily what your business needs in every situation. Sometimes, injection moulding may be a more cost-effective solution.

That said, here are a few of the main advantages of compression moulding, and why.

 

Suitable for high-strength, complex parts

The process of compression moulding involves placing a charge of a specific type of plastic (more on that later) into a heated mould. The mould then closes and pressure is applied to the plastic inside. The combination of the heat, the pressure, and the time causes the plastic to flow and permanently cure, forming the shape set by the mould.

This strength and rigidity makes compression-moulded plastics ideal for parts that need to be heat-resistant, carry a load, provide electrical insulation, protect against chemicals, or otherwise stand up to general wear and tear. (The specific qualities depend on material selection.)

Typical examples of parts made using compression moulding include electrical insulators, industrial housings, rail interiors, structural covers and much more.

For example, compression moulding is ideal for complex geometries with thick cross-sections or large surface areas. Other common methods like injection moulding can struggle with these specific sections of parts, inevitably leading to flow hesitation, internal stress, and a resultant distortion. Not so with compression moulding.

Design teams get a measure of freedom when designing plastic parts that will be formed using compression moulding. That’s because this process supports ribs, bosses and other integrated features without compromising the component’s structural integrity.

 

Material efficiency

Compression moulding typically uses either thermoset or composite plastics, including phenolic resins, epoxy resins, polyester and vinyl ester resins, silicone rubber, SMC (sheet moulding compound), and BMC (bulk moulding compound). Since the curing process is irreversible, it’s essential to place precisely the right volume of material in the mould, not too much, and not too little.

This precision makes compression moulding extremely efficient when it comes to material use. There is very little waste, almost all of which comes from minimal flash. With no runners to grind or manage, there’s even less material waste. All this means enhanced sustainability and a clearer idea when it comes to cost forecasting.

 

Lower tooling costs

Engineering changes and adjustments are needed in almost all manufacturing runs, whether that’s for a complete redesign or a minor tweak, either during R&D or post-production. And in other moulding and forming processes, even small revisions mean large changes to the tooling, affecting things like gates, runners or flow balance. That drives rework and revalidation, all of which means more costs.

Compression moulding brings a simpler tooling approach. When designs change, it still affects the cavity geometry. However, the rest of the tool remains untouched, requiring no adjustments at all. This keeps your modification costs lower and reduces your risks, especially during development or if minor changes are needed post-release.

 

Consistently high quality

Compression moulding is among the most high-quality ways to form plastics. It delivers dimensional stability, uniform density and a controlled, consistent cure across each part of every component.

The process of compression moulding avoids many of the risky variables associated with high-shear flow. The internal stress stays low, with consistent surfaces and thicknesses across all resultant parts.

Many of the industries we work with depend on compression moulding for this quality, producing parts to within +/- 0.1 mm of design specifications. Rail, electrical, automotive and industrial customers, in particular, expect this intricacy, and compression moulding can deliver.

 

Benefits for medium-volume production

Some of the main advantages of compression moulding (as discussed above) come out in medium-volume production runs. That’s primarily because of the low tooling costs, combined with predictable, scalable expenses, cycle times and expected outputs.

As such, you can avoid over-investing at launch and then scale production without forcing a major mid-programme change to the moulding equipment. Again, this brings stability and reduces the risks.

Here at the Talisman Group, we provide clients all around the UK (and the world) with compression moulded components across thermoset and composite plastics. We work with the rail, automotive, electrical, fluid transfer and many more industries to provide the perfect solutions to your parts requirements.

We also offer injection moulding. This process is more suitable for the mass production of smaller, thinner components at lower cost. In some production runs, you might require injection moulded parts alongside compression moulded units.

To discuss which process best suits your production run, and how we work with you to ensure the best possible results, contact our expert team today. We’ll explain all about the advantages of compression moulding and injection moulding, and help you make the right choice.