Compression Molding

PROCESS : This was the first plastic processing method to gain large scale commercial usage. In it, a slug of hard plastic is pressed between 2 heated mold halves. This is generally done with vertical presses as opposed to the horizontal presses used for injection and blow molding. After being formed, the part is air cooled.

RAW MATERIALS : Thermoset plastics are used in this process. These materials cannot be remelted as can their thermoplastic cousins. The most widely used plastic is phenolic, commonly known as “Bakelite”.

TOOLING : Machined steel.

COST : Tooling & parts moderate.

ADVANTAGES : Makes parts which can be subjected to high heat, since the raw material will not remelt. Equipment is readily available.

DISADVANTAGES : High scrap costs. Relatively slow cycle times.

EXAMPLES : Radio & appliance knobs, ash trays & electrical parts.