Understanding Plastic Injection Molding

Posted By: Tony | Date: 30-10-2015

Plastic injection molding and plastic extrusion are somewhat similar in that they are both used to create a final profile or shape according to what the customer needs. While there are definite similarities between the two applications, one of the primary differences is that with extrusions the process is usually continual. Both processes are vital to multiple industries and services offered by Offshore Direct Metals.

Plastic injection molding was first introduced by Jons Jacob Berzelius in 1847. At that time, glycerin and tartaric acid was used to produce the first condensation polymer in the form of polyester. Then in 1861, Alexander Parkes invented the first manmade commercial plastic although initially, it was expensive, flammable, and was known to crack.

By 1868, John Wesley Hyatt developed a different type of plastic called Celluloid, which improved on Parkes' invention. Working with his brother Isaiah, the first injection molding machine was patented in 1872. Although shapes produced were simple, this was the beginning to more modern day plastic injection molding possibilities.

To product certain parts, plastic injection molding is used. In this case, material is injected into the preferred mold. While thermosetting polymers and thermoplastic are the most common, this process can also be performed with metals, elastomers, glass, and even confections. Once plastic is fed into a heated barrel, it is mixed and then forced out into a mold cavity.

Once in the cavity, the plastic cools and hardens in the mold shape. For plastic injection molding, usually an engineer or industrial designer is responsible for designing the mold while a mold maker or toolmaker develops the mold. Typically, the mold used for this process is constructed from aluminum or steel although it can also be precision machined capable of creating specific features of a part.

For manufacturing a long list of parts, plastic injection molding is depended on. These parts can be small and simple or large and complex. For example, body panels in cars are held in place by parts that have been created through plastic injection molding but many industries such as electronics, aerospace, and others also use parts created by this method.

To ensure every part meets or exceeds industry standards, the professionals with Offshore Direct Metals can create a prototype first so any flaws or defects can be identified prior to going into mass production.

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