Compression transfer

Principle

Transfer molding (BrE moulding) is a manufacturing process where casting material (composite of plastic) is forced into a mold. Transfer molding is different from compression molding the mold is enclosed rather than open to the fill plunger resulting in higher dimensional tolerances and less environmental impact. Compared to injection molding, transfer molding uses higher pressures to uniformly fill the mold cavity. The compound used are thermoplastics and of thermosetting materials (mostly).

Application

Transfer molding is mainly used for the manufacturing of pan handles, parts for electrical devices, electronic components or connectors.

Raw materials

The main plastics shaped by compression-transfer molding are thermosets such as epoxides , unsaturated polyesters , phenol-formaldehydes , silicones and fiber-reinforced composite materials made from Bulk Molding Compound (BMC).

Procedure

The raw materials are generally in the form of powders, granules, semi-solids or preforms.

The following steps constitute the molding

  • preheating the mold
  • preheating the material to soften it
  • introducing the softened material into a holding cavity
  • transferring, by pressure, the material of the holding cavity to the preheated mold with a punch through a channel
  • maintaining, in the case of thermosetting materials, the heating until the end of cooking (crosslinking)
  • mold cooling
  • opening of the mold and recovery of the part.

Applications

Connection boxes for electrical or electronical equipments,

Electrical blocks used in the aeronautics, railways or naval industry

Parts for Connecting devices, relays, power contactor, terminal box