Compression Moulding

Compression Moulding UK

We are able to produce compression mouldings in a range of sizes from a few grams to over 10 Kilos in weight. We have an extensive range of compression moulding presses, from 25 tons to 400 tons, including ‘Side Ram’ and ‘Transfer Ram’ presses. Mouldings produced range from small insulators for the electrical industry, to one piece railway carriage seats for modern trains.

Compression moulded products are ideal as cost saving replacements for metal and die cast parts.

Materials along with their properties are selected to suit the application range from the simplest of wood flour filled phenolics, to advanced glass filled flame retardant and low smoke emission, ‘Dough’ and ‘Sheet’ moulding compounds. Our advanced materials selection processes ensure that components are tailored to suit specific applications.

What is Compression Moulding?

Compression moulding is the oldest and, in it’s basic form, simplest way to make rubber products, and for specific applications, compression moulding is still the best way, and not just for rubber.

Developed in the 1850’s, Compression moulding was the original method for moulding rubber and is still ideal for manufacturing low to medium volumes of parts. It’s also a useful moulding process when forming bulky parts. Merriott Plastics Group has a wide range of compression moulding machines, from 5 tonnes up to a 1000 tonne press, with a maximum of a 1 square metre press area.

The following factors must be considered when using a compression molding method:

  • Material
  • Shape
  • Pressure
  • Temperature
  • Part thickness
  • Cycle Time

Compression moulding is a method of component production in which the moulding material, generally pre-heated, is first placed in an open, heated mould cavity. The compression mould is closed with a top force or plug member, pressure is applied to force the material into contact with all ares of the mould, whilst heat and pressure are maintained until the moulding material has cured. The process employs thermosetting resins in a partially cured stage, either in the form of granules, putty-like masses or sheets.

Generally, the compression mould is a matched set of forged steel dies that are plated or surface treated to reduce wear. The mould is heated to 130-170°C, and closed with a fast approach speed followed by a controlled final closure speed. Variable pressure profiles can be used during the mould closure phase. Thermoset compounds are flowable, and with heat and pressure it is transformed from its leather-like quality to a very low-viscosity liquid. The compound flows to fill the mould cavity. A shear edge zone in the perimeter of the cavity enables air to pass through, and the small amount of material that escapes through the sheer edge results in ‘flash.’

Compression moulding can also be used for high-volume, high-pressure components, and is suitable for moulding complex, high-strength parts. Advanced composite thermoplastics can also be compression moulded with unidirectional tapes, woven fabrics, randomly oriented fibre mat or chopped strand. The advantage of compression moulding is its ability to mould large, intricate parts. It can be one of the lowest cost moulding methods, and it wastes relatively little material, giving it an advantage when working with expensive compounds.

Materials along with their properties are selected to suit the application, and range from the simplest of wood flour filled phenolics, to advanced glass filled flame retardant and low smoke emission, ‘Dough’ and ‘Sheet’ moulding compounds. Our advanced materials selection process ensures that components are produced from the best possible material to suit the specific requirements.

Thermoset mouldings give excellent rigidity and electrical resistance coupled with very close dimensional accuracy. They are particularly suitable where flammability is of concern.

Compression moulding is commonly used for manufacturing electrical parts, flatware, gears, buttons, buckles, knobs, handles, electronic device cases, appliance housing, and large containers. As many products are still made using raw materials, compression moulding is likely to remain in widespread use.

At Merriott Plastics Group we are able to produce compression mouldings in a range of sizes from a few grams to over 10 Kilos in weight, and undertake in-mould inserting. Compression moulded products are also ideal as a cost saving alternative to metal and die cast parts, and can even exceed their standards and improve the finished product.

Contact us to find out more about our extensive experience in compression moulding technology.

Merriott Plastics Group – your premier compression moulding company in the UK.

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