Everything You Want To Know About Plastic Injection Molding

In manufacturing, efficiency and reliability are crucial to success. This is where plastic injection molding plays a critical role, revolutionizing the industry with its precision and convenience.

This blog will dive into plastic injection molding — its history, the process, and how it can benefit your business.

History of Plastic Injection Molding

Plastic injection molding dates back to the late 19th century when John Wesley Hyatt invented the first molding machine for plastic injection. The machine utilized celluloid as a material, and it was used to produce simple products such as hair combs and buttons. Soon after, in the early 1900s, Bakelite was introduced, expanding the range of products that could be created.

Significant milestones have been achieved through plastic injection molding, cementing its place as a critical manufacturing process. In the 1950s, the first screw injection machine was introduced, improving efficiency and producing more complex parts. Meanwhile, the 1970s saw the introduction of computer-aided design (CAD) and computer-aided manufacturing (CAM), further enhancing the production process.

Today, this type of injection molding is widely used in various industries — aerospace, automotive, medical, and consumer goods manufacturing, to name a few. With continued advancements in technology and materials, it is expected to remain a vital process in the manufacturing industry for years.

The Plastic Injection Molding Process

Plastic injection molding involves several stages, each crucial to producing high-quality parts. The following is a step-by-step breakdown of the process:


The first stage involves clamping the mold in the molding machine. Here, the two halves of the mold are securely closed to prevent plastic leakage.


Once the mold is clamped, the molten plastic is injected into the mold cavity. This is done under high pressure to ensure the material fills all the mold details.


After injecting plastic, it cools and solidifies in the mold cavity. The cooling time depends on several factors, including the material used, the part’s wall thickness, and the mold’s size.


Once the plastic has cooled and solidified, the mold is opened, and the part is ejected from the mold cavity. This is done using ejector pins that push the part out of the mold.

Types of Plastics Used in Injection Molding

Several types of plastics are used in injection molding, each with unique properties and characteristics. The following is an overview of some of the most commonly used plastic materials:

Acrylonitrile Butadiene Styrene (ABS)

ABS is a thermoplastic polymer known for its strength, toughness, and impact resistance. It is commonly used in the automotive and consumer goods industries.

Polypropylene (PP)

A lightweight and flexible plastic, PP is known for its high resistance to chemicals and temperatures. This makes it an ideal material for manufacturing food packaging and medical devices.

Polycarbonate (PC)

Transparent and lightweight, PC is a plastic that is impact-resistant and shatterproof. Due to these properties, it is utilized in various industries, such as eyewear, automotive parts, and electronic devices.

Polyethylene (PE)

Polyethylene is a remarkably versatile and lightweight plastic with excellent moisture, chemicals, and impact resistance. It is widely used in various packaging materials and household products due to its outstanding properties.

Nylon (PA)

Nylon is a robust and durable plastic resistant to wear and tear. It is commonly used in automotive parts, sports equipment, and mechanical components.

In selecting materials for plastic injection molding, several factors need to be considered: the desired properties of the finished product, the manufacturing process, and the cost. For instance, choosing a material that can meet the application’s requirements while being cost-effective is essential. The material’s properties — like strength, flexibility, and resistance to heat or chemicals — should also be considered.

Upgrade Your Manufacturing Process With Our Plastic Injection Molding

At Seagate Plastics, we offer top-notch custom extrusions, injection molded components, CNC machining, fabrication, and assembly services. We are also an ISO-certified company with 35 years of industry experience, so we guarantee custom thermoplastic products of the highest quality!

Contact us today to learn more about how plastic injection molding can benefit your business. You may also request a quote to let us help you take your manufacturing process to the next level!