Molding technology

What is compression molding?

compression molding

Compression molding is the most widely employed method for molding thermoset plastics, and has been in use for a long time. Measured molding material is forced into a cavity of a heated mold and cured by applying pressure with a compression molding machine. Compression molding has a drawback in that it generates more burrs (excess portion caused by resin overflow from a mold) than injection molding, and therefore requires extra effort in the finishing process. However, it offers great advantages in the fabrication of thick and sturdy parts, and is capable of being applied to the production of multiple parts in a multi-cavity mold at a comparatively low cost.

Characteristics of compression molding:

  • Because molding materials are poured directly into an open mold, material loss is minimized.
  • As there is no material orientation, strong products that make use of the properties of plastics can be fabricated.
  • Because molding pressure can be directly applied to a product, its internal stress is lessened.
  • Because molding pressure can be directly applied to a product, it is suitable for the fabrication of large or thick parts.
  • Multi-cavity molds can be easily made.
  • Because molding is performed while the mold is being clamped, it is difficult to assure dimensional accuracy of the molded products, and hardening requires a longer time.
  • Because the burrs are thick, more time is required in the finishing process.
  • Unfit for molding intricate parts.

Compression molding by Naniwa Gousei Co., Ltd

We have following direct pressure double-action.

  • 2presses:300 ton x 1
  • 2presses:200 ton x 1
  • 2presses:100 ton x 5
  • 2presses:70 ton x 3
  • 2presses:50 ton x 2

Existing compression molds provide less dimensional accuracy than transfer molds. However, we are able to ensure the reliability of our products thanks to our superior technology, and highly experienced engineers, as can be seen from our excellent performance record over more than 50 years.

Needless to say, plastic molding is carried out by a molding machine, but whether the finish is good or not is highly dependent upon the skill and ability of the engineer carrying out the molding operation.
As we conduct full-scale manufacturing from molding to finishing on our company premises, a time-consuming job like deflashing can be carried out in the shortest amount of time.
We make every effort to accommodate our customers’ tight schedules. Please feel free to contact us.