The Basics of Compression Molding
Molding is increasingly becoming common in productions that have high volumes. While there are other methods of molding like injection molding and transfer molding, this article will look at compression molding. It involves plastic being directly placed in a heated metal mold, it is then heated to get soft and using the heat pressure forced to conform to the mold’s shape.
The rubber compression molding commences with a piece of uncured rubber which has been preheated to attain a particular shape and weight. The rubber is injected into a heated mold and to close the mold, a top force is needed. Once the mold has been closed, the material that has been poured goes through some compression by pressing between the plates and causes it to fill the cavity. To activate the cure system, the material is held in the mold and high temperatures and pressures maintained to activate the cure system. It is now time to let the material cool as it has attained the desired end product shape.
Due to the high-pressure, high-volume nature of the compression molding, it is a most suitable process for molding high-strength fiberglass reinforcements. Advanced composite thermoplastics can also undergo compression molding by using unidirectional tapes, or arbitrarily oriented fiber mat. To reduce excess flash, the advanced composite thermoplastics are preheated.
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Compression molding involves three different types of molds; the landed plunger mold, the flash plunger mold, and the straight plunger type. Generally, all the mentioned plunges offer you with different mold size. Compression molding is generally used in manufacturing dinnerware, electrical parts, gears, buckles, buttons, knobs, appliance housing, radio cases amongst others.
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Why Compression Molding is Beneficial
Tooling is less complex and the cost of construction is lower. It has a lower percentage material runner scrape as compared to transfer molding.
Compression molding can be carried out from any of the elastomers and cure systems. There are several points that any engineer should note when it comes to compression molding.
Determining the right amount of material is always important.
It is vital that you check on the minimum heat required for heating the material. check on the minimum heat requirements. Ensure that you have conned the best heating technique.
Predict the amount of force required so as to ensure that the shots attain the proper shape.
Always ensure that the mold is designed in such a manner that it allows fast cooling after it has undergone compression to form it.
Compression molding has a setback in that it is difficult to control flashing and the product consistency is poor. It produces fewer knit lines and less amount of fiber length degradation is noticeable when you compare it to injection molding.