May 14, 2014

Posted by in Business | Comments Off on What are compression moldings?

What are compression moldings?

Compression molding companies produce products with the aid of a mold. The mold is comprised of two parts, a top half and lower half, when the mold is closed the cavity represents the shape of the finished part. The material is usually pre-heated and then placed on top of one of the mold halves, the mold is closed and the material is compressed, filling the cavity. The high pressure that is used spreads the pre-heated material evenly throughout the cavity.

The material that is being used to manufacture the part is pre-heated so that it will conform exactly to the mold cavity, during operation the mold is oftentimes heated as well which stops the material from cooling too quickly. When the mold is closed on the material the halves stay closed while the material cures. The curing process is necessary, otherwise there would a good chance the material would change shape when it is extracted from the mold. Depending on the material which is being used the curing time can be anywhere from a few hours to days.

Compression molding companies normally work with plastics, rubber and sintered metal alloys. The plastic that is usually used for compression molding is either vinyl or polyester. Prior to molding the plastic material is either in the form of pellets, sheet or paste. In many cases additives and fillers can be mixed into the plastic compound, these additives can reduce the cost of the part without being detrimental to its core properties and the additives are also used to combat shrinkage.

When rubber is being molded the compound that is chosen must withstand high temperatures. A primary benefit with rubber compression molding is the smooth exterior surface, this is ideal for components such as liquid stoppers that must fit tightly,

Compression molding brings with it several advantages. As the material is usually soft and pliable when it is introduced to the mold, the compression molding companies can accurately gauge the amount of material which is in the machine. This is especially important when the material is very expensive and scrap must be kept to a minimum. Any material which overflows the mold is called “flash”, this can be removed, reheated and recycled back into the process material, this helps to keep scrap at a minimum.

Compression molded parts can be very intricate as very high pressure forces the material to follow the form of the mold, this advantage is important for those who manufacture small, precise components.

If you are looking for compression molding companies to take on your next project you are invited to contact R.E. Darling Co., Inc.

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