1. Compression and
Transfer Molding Process
Roll # E12-337
Hafiz Muhammad Zubair
5th Semester (Evening)
Department of Metallurgy and Materials Engineering
University of The 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 Molding Process
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
1. The required amount of polymer charge is
weighted and inserted into the transfer pot.
2. The transfer pot is heated by the heating
element above the melting temperature of
the polymer charge.
3. The plunger is used to push the liquid
polymer charge from the transfer pot into
the mold cavity.
4. 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.

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

12. 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