The Basics of Compression Molding

Molding is increasingly becoming common in productions that have high volumes. In this article, compression molding will be discussed while little will be mentioned about the other mold processes like injection and transfer molding. Compression molding involves plastic materials being placed directly into a heated metal mold and then softened using the heat and forced to take the shape of the mold with the closure of the mold.

The rubber compression molding commences with a piece of uncured rubber which has been preheated to attain a particular shape and weight. The plastic or rubber is then inserted into a heated mold and a top force is applied to close the mold. 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. The material is put under the mold in high pressure and extreme temperatures as a way of activating the cure system in the rubber compound. It is now time to let the material cool as it has attained the desired end product shape. To understand more about compression molding, check out https://en.wikipedia.org/wiki/Compression_molding.

Compression Molding is a method that is both high-pressure and high-volume that is suitable for molding complex, and high strength fiberglass reinforcements. It can also be used to mold advanced composite thermoplastics by using unidirectional tapes, chopped strand or woven fabrics. To reduce excess flash, the advanced composite thermoplastics are preheated.

Compression molding involves three different types of molds; the landed plunger mold, the flash plunger mold, and the straight plunger type. All the mentioned types hold a broad size range. This method of molding is commonly used in the manufacture of electrical parts, buckles, radio cases, appliance housing, gears, buttons, e.t.c

Why Compression Molding is Beneficial

The tools used are less complex and have a low construction cost. It has a lower percentage material runner scrape as compared to transfer molding. Check it out!

The process is suitable from most of the elastomers as well as cure systems. There are several points that any engineer should note when it comes to compression molding.

Ensure that you determine the right amount of material.

It is vital that you check on the minimum heat required for heating the material. Always ensure that you know the minimum time required for heating the material. 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.

The mold should be designed for rapid cooling after being compressed into the mold.

With all that said, you should note that compression molding most of the time provides product consistency that is poor and it is difficult to control flashing. It produces fewer knit lines and less amount of fiber length degradation is noticeable when you compare it to injection molding. Visit our homepage if you have questions.