Compression Molding

Note: The following index list will take you to separate articles pertaining to the specific subject.

Index

return to Plastic Information and Processes

Introduction:

This was the first plastic processing method to gain large scale commercial usage.

Practically all compression molding uses thermosetting plastics, But in certain specialized applications, thermoplastic materials may be processed by compression molding.

Many parts may be molded by either compression or transfer molding. Molding technique selection frequently depends upon the molder's own economics and capabilities.

Process:

The material (powder or granular form) is placed in a heated die, melt and fills the cavity. The pressure causes the liquid material to fill and conform to the die shape.

Pressure 100-8,000 psi (0.7-55 mpa) Temperature 250-400 F.

Advantages

  • Parts made by this process (thermosetting plastics) can be subjected to high heat, since the raw material will not remelt.
  • In general, compression molds usually are less expensive to build than transfer or injection types.
  • Waste of material in the form of sprue, runners, and transfer-culls are avoided, and there is no problem of gate erosion.
  • Tooling and part costs are moderate.
  • Internal stress in the molded article is minimized by the shorter and multidirectional flow of the material.
  • Parts with wall thicknesses as thin as 0.025 inch are molded; however, 0.060 is usually recommended

    • Disadvantages

  • Relatively slow cycle times.
  • Very intricately designed articles containing undercuts, side draws, and small holes, may not be practicable.

    • Return to the Enginnering Resource Center Home Page. (ERC)
    Kodak Equipment Manufacturing Division. (KEMD)

    return to Plastic Information and Processes

    Return to the Top