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.

The process requires the application of an injection molding machine, a mold, and raw material. During the process, the plastic is melted in the machine and the injected into the mold. It is then allowed to cool and hence solidifies into the final product.

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.

Secondly, is injection process. During this process, the raw materials which are in form of pellets are usually fed into the machine. After feeding the raw material, they subjected to heat and pressure so that they can melt. The molten materials are put into the molds very fast. Pressure is created which is responsible for packing and holding the materials in place. The quantity of raw material injected is referred to as the shot volume. It is possible to estimate the injecting time using the shot volume, injection power and pressure.

As soon as the molten material comes into contact with the interior surface of this mold, it begins to cool. During the cooling process, the molten plastic solidifies into the shape of the desired part. As cooling takes place, some shrinkage occurs. Therefore, packing of raw material at injection stage allows the flowing of additional materials. Thereby, reducing the amount of visible shrinkage. At this stage, it is left opened until the required cooling is achieved.

Lastly, is the ejection stage. After cooling, the cooled part is removed through the ejection system. This system is attached to the rear half of this mold. Force is applied to eject the part since while cooling; the part may shrink thereby adhering to it. To facilitate the ejection process, a mold release agent is sprayed onto the surface of mold cavity before the injection of this material.

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.

One of the benefits of this process is that it is accurate. It is a precise method which can be used to fabricate any type of part. There are some design restrictions. However, the molds made allow the finished part to be very precise thus very accurate which is made possible by the skillfulness of the designers.




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