The Two Most Common Methods Of Plastic Molding

By Author: Todd Harris
Total Articles: 5
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It was in 1885 that plastic was first invented by a scientist named Alexander Parkes. Ever since then, the material has found its way into countless daily items, and has become integral to various industrial functions. However, it has come a long way from its earliest form when it was limited by shape as well as make up.
Today, you can get plastic objects of any size and shape courtesy of custom plastic manufacturing. The common process by which the material is given the desired shape is known as molding. There are different techniques to plastic molding, each with their own advantages and disadvantages. However, the two most popular methods of molding plastic are:
Injection molding
There are two classes of plastics, thermoplastics and thermosetting plastics. A forming method used for these plastics is the injection molding process. The process involves placing the plastic into a setup known as a hopper which then transfers the plastic ...
... to a heated unit. This heated unit is known as the injection unit and is from where the name “injection molding” comes from. The unit consists of a long chamber where the plastic is melted. The molten plastic is then transferred under high pressure to a mold where it is allowed to cool and solidify.
Once the plastic solidifies, you get the desired product. Although injection molding is commonly used for thermoplastics, that method is not as suitable for thermosetting plastics. Thermosetting plastics tend to set quickly, so they need to go through the injection unit faster. However, faster processing can risk inadequate setting of the plastic.
Compression molding
Since injection molding is not ideal for molding thermosetting plastics, another method used for molding of thermosetting plastics is compression molding. The process involves the use of pressure and heat to give plastics the desired shape.It is also possible to compression mold thermoplastics.

The process involves use of molten resin.The mold cavity is filled with resin and subjected to cycles of heat and pressure to produce a finished plastic part. Usage of resin in this process can be very efficient since the mold cavity is of a known volume and waste of raw material is minimal.Of course, this method is not suitable to all kinds of plastics, which is why there are other less common methods available such as transfer molding, blow molding, and thermoforming.