Although plastic injection molding has advanced significantly over the years, it's still based on the same standard principles it was years ago; today's technological developments have only further enhanced its versatility and reliability.
During plastic injection molding, plastic particles are melted down and injected into molds, which are chilled via water or a coolant that allows the plastic to harden. Once it has hardened, it is ejected from the mold and ready for use.
Plastic Injection Molding Materials
Invented in the 1850s, early plastic forms were extremely hard to work with, but more malleable forms were developed in the 1870s, as was the plastic injection molding process, which allowed for quick, efficient forming tailored to specific application needs.
Today, many types of plastic — of all different melting points — can be used for injection molding, making it a versatile solution for a wide range of industries and applications. Various plastic types offer unique properties and benefits for specific uses and can be combined with other types of materials and additives to allow for different features and coloring.
Some of the most versatile, popular plastics today include:
- PVC and Polyurethane
Plastic Injection Mold Options
In the past, molds were typically created with two different plates; one contained the mold cavity — where the actual injection of molten plastic takes place — and the other was used to efficiently eject the finished product from the mold.
Now, computer-assisted manufacturing (CAM) processes allow for much more complex molds, which may contain multiple sections or parts. CAM also allows for much more detail and precision, but the mold cavity and the ejector plate remain the two critical, primary portions.
Plastic Injection Molding Machinery
Screw injection molding machines — designed and built by American inventor James Watson Hendry — significantly changed the manufacturing landscape; allowing for precise control of injection speed, this technique greatly improved the quality of finished pieces. Screw injection molding also allowed materials to be mixed before beginning the injection process; this meant that colored or recycled plastic could now be added to virgin material and thoroughly blended before actually being injected. Today, around 95% of all injection molding machines make use of this versatile screw technology.
Hendry also developed the first gas-assisted screw machine, enabling the production of complex, hollow pieces that required little cooling time. Allowing for enhanced process flexibility as well as superior strength and finish, this method reduced costs and cut down on production time, waste, and end-product weight.
The Future of Plastic Injection Molding
As technology and automatic capabilities continue to advance, plastic injection molding — and the plastics industry at large — is also continuing to evolve. Today, for instance, lighter-weight materials are becoming increasingly popular, and automation is cutting down on costs and labor needs. Enhanced customization options, meanwhile, are allowing for more tailored plastic solutions. And as eco-friendly initiatives continue to pick up speed — due both to new regulations and shifting consumer preferences — reclaimable, recyclable, and renewable plastics are becoming increasingly popular.
At The Rodon Group, our expert team is well-versed in over 60 years of plastic injection molding, and we're also proud to be at the forefront of today's exciting plastic injection molding evolution. To learn more about plastic injection molding and better understand the various methods available, download Rodon's free eBook, Plastic Injection Molding 101.