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Knowing Your Automobile: How Many Parts in An Automobile Was Made by Injection Molding?

Knowing Your Automobile: How Many Parts in An Automobile Was Made by Injection Molding?

Kenny Leys on Unsplash |Kenny Leys on Unsplash

A thorough checkout of your car will show you the diversity in the use of plastic components in modern automobile manufacturing. According to stats, as of 2016, a typical car has 151 kg of plastic polymers, which is about 8% of the car’s weight and 50% of its volume. The diverse use of plastic materials shows how important the plastic material is in the automobile world. The question then is what makes plastics special and how many parts of an automobile are being made by injection molding manufacturers.

Plastics are chemically stable and lightweight polymers easy to mold to different shapes and sizes. Generally, they also have good insulation properties, low thermal conductivity, etc., which makes them suitable in automobile manufacturing. This article will introduce the different parts in an automobile made via plastic injection molding.

Plastic Injection Molding in Automobile

The benefits of using plastic polymers have improved the relevance of injection molding in the automobile industry. Plastic injection molding is a plastic manufacturing process that involves injecting molten plastic polymers into already fabricated molds and allowing them to cool. It is an important process in the automotive industry due to benefits such as repeatability, precision, etc.

There are many automobile parts manufacturable using plastic injection molding. Listing each part would not be efficient. Therefore, we will introduce them under three general categories. Below are the parts made by injection molding.

Under-The-Hood Components

Recently, automobile manufacturers are transitioning from metals to plastics in making parts such as cylinder head cover, radiator water tanks, fuse box, and oil pans. The under the hood of a car is where most engines are located. Therefore, using plastic parts reduces the weight of the car and the cost of using metallic parts. Here, materials such as ABS, Nylon, and PET are the most common ones for such components.

Other examples of under the hood automobile components made using plastic injection molding include radiator support, air management, HVAC seals, and Dash Noise Control.

Exterior Components

The use of plastic in making automobile parts is more common in the external parts. Injection molding is employed to make components such as fenders, bumpers, door panels, mirror casing, grilles, hoods, headlights, taillights, etc.

Plastic is an ideal material due to its properties in relation to the environment. Unlike metals, plastic does not undergo processes such as rusting and it is chemically and thermodynamically stable in dry and wet conditions. Also, plastics are moldable, which ensures that you can design many components as you like.

Interior Components 

Plastic polymers’ ability to be molded into different shapes, dimensions to achieve the needed design makes it an excellent material for making interior automobile components. Here, parts such as interior surfaces, dashboard faceplates, door handles, A/C condensers, glove compartments, and air vents are carefully molded.

 Knowing Your Automobile: How Many Parts in An Automobile Was Made by Injection Molding?

The Benefits of Plastic Injection Molding in Automobile

The benefits of injection molding in the automobile industry are visible in its uses in making parts that reduce fuel consumption, reduce car weight, improve design, etc. It is undeniable that plastic parts are becoming a rave. Consequently, plastic injection molding has a few benefits for the automobile industry. Below are a few benefits of the process.


One of the most important requirements of the automobile industry regarding any manufacturing process is the degree of repeatability. Repeatability means that the manufacturing process must be able to make identical parts consistently.

Plastic injection molding guarantees repeatability as a mold can be used in making the desired parts as needed. For example, in making radiator water tanks, a single mold can be used for making many tanks without a change in dimension. The repeatability of the process, however, depends on the design and the durability of the injection mold.

Scalability and Cost of Production

For any business, there is a need to balance cost and production. The cost of making a mold can be very high due to the process used (since most injection molds are made using CNC machining). However, due to the making of many parts using the same molds, injection molding is a highly scalable process.

Nevertheless, remember that the scalability depends on the number of parts produced by automotive industry injection molding manufacturers. For mass production, it is beneficial. However, if you have any less than that, you may attract a high cost.

Material Availability

Different plastic materials are employed in making many automotive parts. Popular ones include ABS, PET, polypropylene, acrylic, acetal, nylon, polycarbonate, etc. The wide range of plastic materials with differences in properties such as rigidity and flexibility, and application makes plastic injection molding a huge benefit to the automotive industry as manufacturers can easily use different plastic polymers for various applications in the automotive industry

High Precision and Surface Finish

Plastic parts used as automotive components have exquisite designs, dimensions, and complexity. Achieving these requirements is possible as plastic injection molding allows injection molding manufacturers to make parts with high precision. The process is suitable for making products with simple and complex geometries and guarantees better surface finish quality.


The automotive industry thrives on performance and aesthetics. On the one hand, performance is improved by the incorporation of plastic which reduces fuel consumption and other benefits. On the other hand, aesthetics occurs as a result of good design and color options on the plastic component. Injection molding manufacturers can mix dyes with plastic materials prior to production. Consequently, there is consistent coloration after molding, which improves aesthetics.


Plastic parts are becoming popular in the automotive industry due to the reduction in weight, fuel consumption, and improved aesthetics. Fabrication of such plastic parts is possible via many manufacturing processes. However, the most common one used due to its benefits is plastic injection molding. This article introduced plastic parts used in automobiles and the benefits of using the process in the automotive industry.