(Photo : Raghavendra V. Konkathi via Unsplash)

The global plastic injection molding market size was recently estimated to be 360.6 billion USD in 2019 and is projected to swell to 498.98 billion USD by 2027. This demonstrates that the injection molding industry is a veritable giant in its class.

Part of the reason plastic injection molding is so successful is because there are so many technologies available to help manufacturers build their products. 

From pressurization that achieves uniform wall thickness to smart polymers that form new materials for injection molding, the injection molding industry has many tools under its belt - and is developing more every day. Here are some of the most popular injection molding technologies.

Some manufacturers may think only in terms of processes when they consider injection molding technology, but this need not be the case. Novel polymers are continuously being developed that can improve plastic material properties, and choosing the right resin plays just as vital a role in product design as the manufacturing process itself.

Selecting the right injection molding material depends largely on the properties your part must possess, a few of which might be:

Sometimes a basic plastic material will have all the material properties that your part needs, while other designs require a more advanced material. 

Third-party manufacturing experts can advise you on which injection molding materials are best for your build, so be sure to consult an expert before choosing what your part will be made from.

Many plastic products must have a high strength but low density for minimal weight. When this is needed, structural foam molding can be a helpful process to use. Structural foam molding involves the insertion of an inert gas as the molten resin is injected into the mold at a lower pressure than usual. 

The added gas helps reduce density while facilitating the lower injection pressure, which in turn allows the equipment to operate more efficiently. Tooling is therefore easier as well, and the reduced equipment strain allows for more parts to be produced.

If a high strength-to-weight ratio is needed for a large number of parts with minimal equipment strain, structural foam molding may be the route to take.

Hollow parts that are designed to hold a given fluid or gas often need a thick wall, which can be difficult to mold effectively. Thick walls don't cool uniformly, which can cause the plastic to warp and lose both its aesthetic and functional properties.

Enter gas-assisted injection molding. To prevent the plastic from warping, a pressurized gas is forced into the mold cavity, pressing against the surface and holding it in place. 

By adding a competing pressure into the mold, gas-assisted injection molding makes uniform thick-walled products possible and reduces surface finish costs in the process.

Thick-walled products are helpful for high-pressure products, but other parts require a thin wall to achieve their purpose. Thin wall molding is used to create many products like tubing, medical equipment, and other simple enclosures.

While it's an effective solution for many parts, it does have its drawbacks. The minimal thickness means cracks can form along the surface if the mold doesn't cool uniformly, which can result in leaks and malfunctions. Checking for quality is essential, perhaps using non-destructive testing (NDT) methods.

Despite the potential for defects, thin wall molding is still an effective choice for building thin-walled plastic parts, and the risk of cracks can be mitigated with proper quality control measures.

Plastic isn't the only material that can be used in injection molding. After evaluating the material properties that your part must possess, you may find that liquid silicone is a better choice for your part.

Plastic and liquid silicone injection molding are similar in that both force their respective materials into a mold or cavity, but there are several important differences between the two. While the former inserts a molten resin into a cooler cavity, the latter inserts chilled silicone into a heated mold. This vulcanizes the silicone, converting it into a solid in the shape of the mold.

Another difference is that heated plastics can be cooled and reheated to form a new molten resin for further use, but once heated into a solid, silicone cannot be converted back into a liquid form.

 This means that there is more waste in liquid silicone injection molding, but the process is still useful for manufacturing sealants, electronics, automotive parts, and more.

Injection Molding Technologies: Bringing Your Product to Life

These are just a few of the most common injection molding technologies, and many others are under development. 

In fact, some molten metals can now be injection molded using high-performance equipment, and despite their higher cost, they are useful in applications like the aerospace industry. 

Innovation is truly pushing the boundaries of what was once thought possible in the injection molding industry, and with such an array of technologies available, manufacturers have all the methods they need to turn their designs into reality.

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