Injection molding is a method used by machine part manufacturers to produce large quantities of parts through the injection of molten material into a mold. The process has evolved considerably since it was first invented in the 1800s and has expanded and adapted during boom periods for businesses both in North America and worldwide. Today, more conscious manufacturers, driven by increasingly eco-aware customer bases, are seeking new ways to introduce more effective and efficient materials and processes into injection molding.
The injection molding process involves the use of various materials that can produce parts of reliable quality. These materials can include metal, glass, thermoplastics, and more, while the molds themselves are usually made of steel or aluminum. Injection molding is currently the most common method of part manufacturing and can be used to create a wide variety of machine parts—everything from beverage containers and caps to children’s toys to automotive parts. It is an age-old process still in wide use today, but it is hardly the same as it was hundreds of years ago.
New advancements in industrial technology are allowing the process to be reconsidered. For example, 3D printing is proving to be a way to revolutionize injection molding. Printed molds are typically produced in two configurations: mold inserts in aluminum frames, which are the most common configuration and produce more accurate parts; and standalone molds, in which the mold is fully printed. A piece for The Welding Institute says that 3D printing, also known as additive manufacturing, is ideal for fast prototyping, with turnaround times of one to two per week, and allows for frequent design changes. “This process is also able to produce relatively small plastic parts and components, while also being ideal for complex or intricate designs.”
Mold elements like steel and aluminum are resistant to wear and tear during the molding process but can require a large initial investment. Because of this, molding projects with a lower planned run often need to shift focus away from wear resistance, making certain 3D printing technologies an attractive solution. When high-accuracy part printing processes such as material jetting and stereolithography are paired with temperature-resistant printing materials, printed molds become a good option for manufacturing low-run injection molding dies.
According to The Welding Institute, while 3D printing is currently seeing more widespread adoption, injection molding remains the preferred process for manufacturing plastic parts due to the cost efficiency and quality associated with mass production. However, 3D printing can be preferable for prototyping projects because injection molding tooling design is often expensive and time consuming.
This distinction can be seen in areas such as the medical field, where 3D printing is used for the production of custom items like prosthetics. “Rather than seeing 3D printing as a potential replacement for injection molding, the two technologies should be seen as complementary processes that can be used together depending upon requirements,” according to The Welding Institute, which says that 3D printing is currently best suited for low-production runs of 100 parts or fewer due to the time and cost involved in larger runs.
Moving beyond additive manufacturing—and like many other sectors undergoing similar changes in processes and materials—injection molding is also addressing a shift toward greater sustainability. Companies such as sustainable plastics manufacturer BIO-FED are now openly using compounds made from biodegradable biopolymers and renewable raw materials. Renewable materials can replace traditional injection molding materials like metal, glass, and ceramics with alternatives such as coconut shells and rice hulls. Research into these practices is ongoing, and new materials are being discovered and tested on a regular basis.
In a piece on sustainable plastics manufacturing for Fictiv, David Willson says that the plastics manufacturing industry is shifting toward more sustainable practices, driven by a global desire for environmentally friendly solutions. “Sustainable plastics, designed to minimize ecological harm through renewable sourcing, recyclability, or biodegradability, are driving this change,” Willson writes. Materials such as biodegradable and recycled plastics, including polylactic acid, polyhydroxyalkanoates, post-consumer resins, and thermoplastics, are increasingly being adopted. Bio-based polymers sourced from plants like corn or sugarcane are also appealing, as they offer a lower carbon footprint. “Unlike virgin plastics, which emit 2 to 3 kg of CO2 per kg during production, recycled plastics can reduce emissions by up to 60 percent, often to 0.8 to 1.2 kg of CO2 per kg.”
These sustainable practices require additional care, as materials must be carefully sorted to remove contaminants that could affect color or strength. Bio-based plastics often require industrial composting facilities to break them down effectively, making widespread adoption more challenging. In some cases, production can place strain on agricultural resources, such as polylactic acid requiring up to one hectare of land per ton, meaning the transition is not as simple as switching materials without further consideration.
Beyond additive manufacturing and sustainability, other emerging technologies are also influencing injection molding. The industry has become more intelligent and data-driven, combining sensors, algorithms, and electric drives to achieve consistent quality. Artificial intelligence is being used more frequently in injection molding, with direct integration into machines and controllers to help predict and correct process inefficiencies, further automating mechanical operations.
Electric injection molding machines are also gaining traction, offering greater precision and energy efficiency than traditional machines. They provide improved motion control, faster response times, and more repeatable injection processes. However, the initial investment for electric machines remains high, and maintenance has become more specialized. Like 3D printing, electric alternatives are promising but come with their own challenges.
Further technological advancements will continue to drive innovation in the injection molding sector as smart manufacturing technologies increase efficiency through real-time monitoring and improve quality through Internet of Things sensors. Predictive maintenance can help reduce costs by limiting equipment failures and labour expenses, while data analytics can enhance flexibility and supply chain planning.
Injection molding, and plastics manufacturing as a whole, are entering an especially dynamic period of innovation and sustainable development. The topic remains prominent at major industry gatherings such as the annual Medical Design and Manufacturing (MD&M) trade show, which regularly features injection molding among its key subjects. As global demand for machine parts continues to rise year over year, innovation in processes like injection molding is increasingly important, particularly as customers expect more responsible and efficient production from industries that have existed for centuries.
