Compression moulding is a manufacturing process that creates a range of parts and products with complex shapes and high strength, such as electrical sockets, isolators, and connector blocks. The plastic material is heated in an oven or another heating device to the point where it becomes pliable and flowable. This step is critical as it allows the material to easily flow and fill the mould cavity. The pre-heated plastic is placed into a mould cavity. Typically, the material is manually or mechanically loaded into the mould and then closed with a top force or plunger that applies pressure to the material. The pressure ensures that the material thoroughly and uniformly fills the mould cavity. The material is cooled and solidified naturally or through a cooling system. This is significant because it allows the material to keep its shape and structural integrity after removing it from the mould. The finished product is removed from the mould by opening and releasing the part. The part can be removed manually or automatically.

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What are the Different Types of Compression Moulding?

Hot Compression Moulding

This is the most common type of compression moulding, and it involves high temperatures to melt and flow the plastic material into the mould cavity. The material is placed in an oven or other heating device to raise its temperature to a point where it becomes pliable and flowable.

Cold Compression Moulding

Cold compression moulding is a manufacturing process that involves using lower temperatures to mould the material. The process is similar to hot compression moulding, but the material is typically pre-heated to a temperature below its melting point. The material is then placed in the mould and subjected to high pressure, which causes it to fill the cavity. The material is cooled and solidified, and the finished product is removed from the mould.

Cold compression moulding often produces parts with high strength and dimensional stability. It is particularly well-suited for materials sensitive to high temperatures. The process can also produce parts with high accuracy and repeatability.

Transfer Moulding

Transfer moulding is a type of compression moulding that involves using a plunger to transfer the material from a pot or other container into the mould cavity. The material is typically pre-heated to a temperature where it becomes pliable and flowable. The plunger is then used to push the material into the mould cavity, which is subjected to high pressure. The material is cooled and solidified, and the finished product is removed from the mould.

Transfer moulding is often used to produce parts with intricate shapes and features, such as seals and gaskets. It is a versatile process that can be used with many materials.

What Materials are used for Compression Moulding?

Both thermoplastics and thermosets can be moulded using compression moulding. Thermoplastics are plastics that soften when heated and harden when cooled, and can be reshaped multiple times by repeating this process. Thermosets, on the other hand, are plastics that cure irreversibly when exposed to heat and can only be moulded once.

Materials commonly used in compression molding include:

  • Diallyl phthalate (DAP)
  • Epoxy
  • High-density polyethylene (HDPE)
  • Polyamide-imides (PAIs)
  • Polyether ether ketone (PEEK)
  • Polyurethane (PU)
  • Polyphenylene sulfide (PPS)
  • Phenolic resins (PF)
  • Polytetrafluoroethylene (PTFE)
  • Silicone
  • Urethane

What are the Advantages of Compression Moulding?

  • High dimensional accuracy and consistency: The process allows for tight tolerances and precise dimensions, ensuring consistency in the final product.
  • High strength and durability of products: Compression-moulded products are known for their strength and durability, making them suitable for various applications.
  • Versatility in the types of materials used: Compression moulding can be done with a wide range of materials, like thermosetting plastics, rubber, and composites.
  • Variety of shapes and sizes that can be produced: Compression moulding can produce many shapes and sizes, from small to large parts.

What are the Disadvantages of Compression Moulding?

  • Limited to producing solid parts: Compression moulding is only suitable for producing solid parts and cannot be used for hollow parts.
  • Can be sensitive to changes in temperature and humidity: Compression moulding can be affected by changes in temperature and humidity, which can affect the quality of the final product.
  • A higher initial investment in equipment and machinery: The cost of equipment and machinery for compression moulding is relatively high compared to other moulding methods.
  • Limited colour options for the final product: The selection of colours for compression-moulded products can be limited, as the process may not accommodate certain colours or pigments.
  • Limited to specific types and sizes of products: Compression moulding is unsuitable for producing small, intricate parts.

How Can I Contact the Leading Compression Moulders in the UK & Ireland?

Click here to visit the PlastikCity website, where you can contact the leading compression moulding manufacturers in the UK and Ireland for advice, assistance or a quote for your compression moulding project, free of charge.