Automotive Injection Molding
5 minutes

In the automotive industry, achieving superior durability of automotive parts is important to ensure the reliability, safety and service life of vehicles. Then, one of the key technologies to achieve this goal is injection molding.

What is automotive injection molding?

Before understanding what is the automotive injection molding process, first review the development history of the automobile.

The earliest cars relied heavily on heavy metal parts. It was not until the appearance of plastics in the 1940s and 1950s that the development of the automotive industry was changed, initially plastic was used for car decoration. By the 1980s, plastic was being used for functional parts like lights and bumpers. By the beginning of the 21st century, plastic parts produced using injection molding processes reduced the weight of automobiles, improved fuel efficiency, and reduced production costs. To this day, injection molding remains one of the most popular manufacturing processes in the entire automotive industry. So what is automotive injection molding? Read on.

Automotive injection molding is a type of injection molding specialized for the production of complex and durable automotive plastic parts. It involves injecting a molten material (usually a thermoplastic) into a mold cavity under high pressure. This process allows precise forming of automotive plastic parts with complex geometry.

How automotive injection molding works?

The production process of automotive injection molding begins with the creation of a virtual model using computer-aided design (CAD) software, which serves as a blueprint for the mold (which is typically made of durable metals such as steel or aluminum). When the mold is ready, it is installed into an injection molding machine, which then begins its work by injecting the heated plastic into the mold cavity under high pressure, after which the mold quickly cools the material to set it. After cooling, the mold opens and the car parts pop out. After the car parts are produced, they can also be subjected to additional post-forming treatments, such as trimming, anodizing or polishing, as required.

Advantages of automotive injection molding

Injection molding is used in automotive parts manufacturing because it offers several key advantages that make it the preferred manufacturing method for the automotive industry. Injection molding allows complex part geometrics to be produced with high precision, providing a versatile choice of materials based on desired properties such as durability, heat resistance and impact strength. Thanks to the automated nature of the injection molding process, production cycles and high yield rates are accelerated and consistent part quality is ensured.

Automotive injection molding is suitable for high volume production, and compared to traditional metal parts, injection molded plastics can significantly reduce the weight of the vehicle, helping to improve fuel efficiency and performance. Moreover, injection molding allows for the integration of multiple functions such as inserts, threads, and complex geometries in a single part.

Although automotive injection molding has many advantages, there are also several potential disadvantages to consider. Mold manufacturing costs for injection molding are often high, especially for complex or large parts. And, although injection molding is fast, it usually takes a certain amount of time to make a complete set of molds. This can lead to long delivery times, especially when customization or modification is required.

Types of automotive injection molding technologies available

Each injection molding technology has unique advantages, depending on the specific requirements of the automotive parts being produced:


Overmolding involves molding one material (overmold) onto another substrate (substrate), typically a rigid plastic or metal insert. The overmold material bonds mechanically or chemically with the substrate during molding, providing enhanced durability, ergonomic benefits, and improved aesthetics. Automotive applications of overmolding include handles, grips, buttons, seals, and encapsulated electronic components, where it improves comfort, reduces vibration, and simplifies assembly.

Insert Molding

Insert molding integrates metal or plastic inserts into the mold cavity before injecting molten material around them. This process enhances part strength, durability, and functionality by securely encapsulating inserts within the molded component. Insert molding is utilized in automotive applications for producing parts such as connectors, threaded inserts, brackets, and housings, where metal inserts provide enhanced wear resistance or facilitate reliable fastening.

Bi-Injection Molding (Two-Shot Molding)

Bi-injection molding, also known as two-shot molding, enables the simultaneous or sequential injection of two different materials or colors into a single mold. This process allows for the production of multi-material or multi-color automotive parts in one integrated operation, eliminating the need for secondary assembly processes. Bi-injection molding is widely used for producing automotive components with integrated seals, soft-touch surfaces, ergonomic grips, and complex aesthetic designs.

Commonly used materials for automotive injection molding

Automotive injection molding utilizes a variety of materials carefully selected for their specific properties and performance characteristics across different automotive applications.

  1. Polypropylene (PP): Known for its lightweight nature, high impact resistance, and good chemical resistance. It is also cost-effective, making it suitable for interior components like door panels, dashboard trims, and storage bins.
  2. Polyvinyl Chloride (PVC): PVC is known for its flexibility, durability, weather resistance and flame retardancy. PVC plastic injection molding is used in automotive wiring harnesses, interior components and weather seals to provide protection and reliability in a variety of environments.
  3. Acrylonitrile Butadiene Styrene (ABS): ABS is tough, impact-resistant, and offers good dimensional stability and surface finish. It is commonly used for interior and exterior trim components, instrument panels, and grilles due to its durability and aesthetic appeal.
  4. Polyamide (PA, Nylon): Polyamide materials offer high strength, toughness, chemical resistance, and good thermal stability. They are used in demanding applications such as engine components, electrical connectors, fuel system parts, and air intake manifolds.
  5. Polycarbonate (PC): PC offers high impact resistance, optical clarity, and good dimensional stability. It is commonly used for automotive lighting lenses, instrument panels, and safety equipment to ensure visibility, durability, and safety.

Parts production applications for automotive injection molding

Here are some key parts production applications where automotive injection molding is extensively used:

  1. Interior Components: Includes dashboard, vents, glove box covers, door panels, armrests, door handles, speaker grilles, finishes, seat backs, bases, headrests, armrests, cup holders, lockers, and gear shifters.
  2. Exterior Body Panels and Trim: Includes bumper, front grille, side die, mirror housing, headlight lens, taillight housing, turn signal indicator, etc.
  3. Under-the-Hood Components: Includes engine cover, housing, air filter housing, fuel system components, reservoir, oil cap, cooling system components, radiator tank, fan cover and coolant storage.
  4. Electrical and Electronic Components: Includes electrical connectors, fuse boxes, sensor housing, internal switches, buttons and knobs.

Metal to plastic conversion in automotive manufacturing

The conversion from metal parts to plastic parts for automotive manufacturing achieves superior performance and efficiency. Through a partnership with an automotive injection molding company, traditional metal parts are replaced with lightweight and durable plastic alternatives. This shift will not only help meet stringent fuel efficiency standards and emissions regulations, but also help reduce operating costs.

By utilizing advanced technologies, implementing best practices, and adhering to strict quality control standards, BOYI specializes in the use of injection molding processes to manufacture high-quality plastic parts for the automotive industry. These parts are designed to meet the rigorous requirements of automotive engineering, ensuring optimal performance and reliability while addressing the complexities of modern vehicle design and manufacturing.

Key factors enhancing durability of automotive components

The key factors to improve the durability of automotive parts cover a number of aspects, and the following are some of the main factors:

Material Selection

In injection molding, most engineers typically choose engineering grade polymers such as polyamide (PA), polypropylene (PP), and acrylonitrile-butadiene-styrene (ABS). Because these polymers have excellent mechanical properties, chemical resistance and heat resistance. Suitable for special automotive parts applications that require special durability.

Surface Finishing

Achieving a durable finish on automotive parts is important for aesthetics and long-term durability. Techniques such as polishing and anodizing can enhance the visual appeal of the car while ensuring resistance to wear and scratches.

IATF 16949 Certification

If you are looking for a reliable injection molding company to work with, make sure your injection molding company is compliant with IATF 16949 certified quality management standards. The certificate emphasizes durability, continuous improvement, defect prevention and sound supply chain management. It is important to ensure the reliability and durability of automotive components.


By utilizing injection molding technology, manufacturers can not only produce automotive parts that can withstand the daily rigors of use, but also improve vehicle performance and safety.

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