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The Techonlogy Of Compression Moulding

Join Date: 2019-07-06

Compression Moulding

MDC mould have been engaged in the development and manufacture of compression moulding for more than 20 years, are you interested in the technology of compression moulding?

Compression moulding is a technique mainly for thermoset moulding in which the moulding compound is placed in the open mould cavity. Heat and pressure are applied until the material is cured. Compression moulding is often used for moulding of glass fibre reinforced plastic.

Compression moulding is often associated with Sheet Moulding Compound (known as SMC), Bulk Moulding Compound (known as BMC) and Long Glass Fibre Polypropylene (known as LGFP). The materials all use long glass fibre as its reinforcement and have been formulated to meet specific performance levels required for the part to be produced. They are ideal replacements for metal, aluminium, concrete and timber components.

SMC, BMC, GMT, LWRT and other compression moulding processes have been widely used in many industries such as automobiles and electrical appliances. MDC mould, as an industry leader, is currently working with OEN to push composite materials into more fields.


  • Fill the indentation of the die with a pre-weighed thermosetting powder mixture or pre-formed granules.
  • Usually, the charge is preheated to 60-100?C first. The mould is heated to 140–170°C, and the temperature may increase further due to the exothermic characteristics of crosslinking.
  • Use the top convex punch to apply pressure. This allows the material to flow into the desired shape.
  • Compression moulding is a low shear process and uses a minimum flow mode.
  • Curing also occurs under the influence of heat and pressure (curing time varies between 0.5 and 3 minutes). This reduces productivity compared to injection moulding.
  • Since there are no gates or runners, the rejection rate (2–5%) is lower than injection moulding.
  • Product shrinkage rate is low (<1%).
  • The process can be repeated for precise shaping.
  • Metal inserts and threads can be compression moulded.


  • Use only for thermoset polymers in the following cases:
  • Phenolic formaldehyde
  • Urea-formaldehyde
  • Epoxy resin
  • Add filters for dilution or reinforcement, such as wood flour, cotton, glass, mica or talc.
  • Phenolic resin is hard and strong, but it can also be brittle.
  • The material has good electrical insulation properties.
  • The maximum operating temperature is 150°C.


  • The size of the item is limited by the size and capacity of the available press.
  • The weight of the parts varies from 0.1 kg to 15 kg.
  • The wall thickness of the die casting should be uniform and within the range of 3-6 mm. It is possible to mould thicker walls up to 12 mm, but the curing time is not economical.
  • Parts with these design requirements may not consider very complex items with undercuts, small holes or undercuts.
  • A draft angle of at least 1° is required.
  • The tolerance should be as wide as possible. The material will shrink to varying degrees. The greater the shrinkage, the greater the tolerance.

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