Compression and Transfer Moulding

1. Compression and Transfer Molding P rocess Roll # E12-337 Hafiz Muhammad Zubair 5 th Semester (Evening) Department of Metallurgy and Materials Engineering University of T he Punjab

2. Compression Molding: What? The process of molding a material in a confined shape by applying pressure and usually heat . Materials used for Compression Molding are Epoxies , Urea formaldehyde, Melamine formaldehyde, Phenolics , Polyester, Polyamide etc. It is used for manufacturing electrical and electronic equipment's, circuit breakers, television cabinets, radio cases, electric plugs and sockets , electrical switch, fuse box, electricity meter housing .

3. Working Principle The charge of plastic material is placed in the lower half of a heated mould cavity. The mold cavity is closed with upper movable half mold and pressure is applied. The pressure is applied along with heat to compress the material, which also increases the polymerization process. The mould cavity is then opened and the final product is taken out.

4. Stages in Compression molding cycle: The stages of the compression molding cycle time can be represented as a function of the force.

5. Pros Low initial setup costs and fast setup time Heavy plastic parts can be molded Complex intricate parts can be made Good surface finish of the molded parts Cons Low production rate Limited largely to flat or moderately curved parts with no undercuts Secondary operations maybe required

6. Transfer M olding P rocess In the transfer molding, polymer charge is transferred from the transfer pot to the mold. The mold is cooled and molded part is ejected. Generally, thermoset plastics (such as epoxy, polyester, phenol-formaldehyde, vinyl ester, silicone ) are processed by transfer molding process, but certain thermoplastic materials can also be processed . This process is widely used to encapsulate items such as integrated circuits, plugs, connectors, pins , coils etc.

7. Steps In Transfer Molding The required amount of polymer charge is weighted and inserted into the transfer pot. The transfer pot is heated by the heating element above the melting temperature of the polymer charge. The plunger is used to push the liquid polymer charge from the transfer pot into the mold cavity. The mold cavity is held closed until the resin gets cured. The mold cavity is opened and the molded part can be removed.

8. Pros Fast setup time and lower setup costs Low maintenance cost Plastic parts with metal inserts can be made Design flexibility Dimensionally stable Cons Wastage of material Production rate lower than injection molding Air can be trapped in the mold

9. A hybrid polymer–glass achromatic microlens array fabricated by compression molding This affordable and high precision microlens array design has potential applications in the optical industry for its capability of correcting chromatic aberration. In this research a special doublet design was investigated. Specifically, polycarbonate and P-SK57 glass were selected as the equivalents of flint and crown glass for their opposite dispersion properties. The polymer microlens arrays were fabricated by thermal compression molding at a specific forming temperature.

10. Material properties of the P-SK57 glass used in the simulation.

11. Conclusion: Compression molding process is one of the low cost molding methods as compared to injection molding and transfer molding and this process is most suitable to manufacture electrical and electronic equipments. Thanks Q&A