Compression molding.

Molding

Molding is a technique generally use for thermoplastic and thermosetting materials.

This technique is used to produce sheet like, hollow and solid materials, from very small to very large materials. The various molding process are

Injection molding.

Extrusion molding.

Blow molding.

Compression molding

This technique is widely used in automotive (vehicle motors) industries to produce parts that are large, thin,strong,stiff. This process is also used in household goods and electrical industries.

The polymers processed from compression molding are epoxies (EP), phenolics(PF), melamine formaldehyde (MF) and urea formaldehyde (UF).

Compression molding occurs by the following steps:

Compression molding.

A pre-weighed polymer with additives and fillers (called charge) is placed in the lower half of the mold.
The charge may be powder, pellets,putty like masses.
The charge are heated before placing on the lower half of the mold as the heated polymers are soft which reduces the molding cycle time.
The upper half of the mold moves downwards which forces the charge to fill in the gap of mold (called mold cavity) of the lower half.
The mold is opened the molded part is seperated by means of ejector pin.
If polymer is thermosetting, the mold can be open when hot because the cured thermosetting retain its shape and dimension when hot.
If polymer is thermoplastic, the mold and molded part is allowed to cool and then open.

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