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Learn The Process Of Plastic Injection Molding

By Dennis Foster


Manufacturing industry is among the leading industry in the state. Plastic injection molding usually is among the manufacturing procedures which deal with the fabrication of plastic parts. A broad range of products is manufactured through this process. The products vary greatly in size, complexity as well as application.

Three things which are needed in this process include an injection molding machine, mold, and raw material. The process involves melting the plastic in the machine. The molten plastics are injected into the mold. It then undergoes cooling and solidification to form the final product which is ready for the market.

The process has four steps the first one being compaction. Here, the two halves of these molds are clamped together in the clamping unit. Clamping takes place before injection, and it ensures that the halves of the mold are securely closed. During the clamping process, the two parts produce a force which is sufficient to keep it shut for the whole process.

After clamping the material are injected into these molds. The materials entering the molds are usually in a molten state. To begin this stage, the raw materials which are in the form of pellets are fed into the machine. Heat and pressure are applied to them making them melt. The molten material is the injected into the molds. Pressure is created that packs and holds these materials into position. The amount of material injected into it is known as the shot. The taken while injecting the materials can be estimated from shot volume, injection pressure, and injection power.

Thirdly, is cooling. The molten plastic which is inside the mold starts to cool immediately it comes in contact with the interior mold surface. As it cools, it solidifies to the shape of the required part. However, it is important to know that during cooling, some shrinkage may occur. As a result, the packing of material in the previous stage allow additional material to flow into it thus reducing the visible shrinkage. The frame remained opened until required cooling is obtained.

Finally, the materials are removed from the molds in a process known as ejection. This procedure occurs in the ejection system which normally is attached on the back of the mold. As stated earlier, shrinkage normally takes place as the material cools. For this reason, some material adheres to the mold. A force is thus applied to force these materials out of the mold. A mold release agent can be sprayed on the surface of this mold before injections to make ejection easier.

This process is used to produce thin walled plastic parts for different applications. One of the common is plastic housing which is a thin walled enclosure. The housings are used in several products such as power tools, household appliances, automotive dashboards and consumer electronics.

On its benefits, accuracy is the outstanding; however, there are some other advantages. This process is accurate because it allows fabrication of any form of the part. Despite design restrictions of these molds, the finished parts are usually precise.




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