Introduction:Automotive injection molding process is when you use injection molding to make car parts. You can make lots of different parts for a car, like the dashboard, bumper, headlights, and parts under the hood, using automotive plastic injection molding.

In this article, we’re going to dive deep into how plastic injection molding is used in the automotive parts manufacturing industry, what types of injection molding materials are used in the automotive industry, the types of injection molding technique used in the automotive industry, the benefits of injection molding in automotive applications, and the production applications of automotive injection molding.

How did Injection Molding Begin to be Used in the Automotive Industry?

Back in the day, car companies didn’t use plastic injection molding much. They mostly used metal stamping to make parts, but those parts were heavy and expensive. But as the car industry grew, they needed to find ways to make parts faster and cheaper.

Back in the 1950s, they started using injection molding to make decorative stuff. Then, in the late 1970s and 1980s, plastic injection molding became the way to go for making molds for all kinds of car parts, like dashboards, headlights, and instrument panels.

In the 2000s, plastics became a big deal in the automotive industry. They were lighter than metal parts, so they made cars more fuel-efficient and cheaper to make.

The advantages of injection molding made it the way to make stuff for a lot of other industries too. Today, a lot of industries use plastic injection molding to make all kinds of parts and stuff.

Why Choose Injection Molding for Automotive Parts?

Injection molding is great because it can make parts that are really complicated, with tight tolerances and a nice surface finish.

Also, injection molding is a super versatile process that manufacturers use to make all kinds of automotive components, from engine stuff to body panels. It’s a scalable process, and you can make thousands of the same thing using this method.

What are the Materials Used to Manufacture Automotive Injection Molded Products?

Since car makers make a bunch of different parts through car plastic injection molding, not one material is good for everything. So, they use different plastic polymers for car parts. 

Here’s a list of plastic materials that car makers use to make car parts.

Polypropylene (PP)

Polypropylene is a polymer of propylene and is one of the common materials used to make car parts. It is used to make the outside parts of cars, like bumpers, because it doesn’t get hurt by chemicals, UV rays, or water. It is also used to cover cables.

Polyvinyl Chloride (PVC)

PVC makes up about 16% of the plastic parts in cars. Because it’s flexible and can withstand heat, auto parts makers use it to make different parts with different hardnesses, including interior panels and dashboard components.

Polyurethane (PU)

Stuff that needs to be bendy, like foam seats, often uses polyurethane. Car seats are an example. Polyurethane is also used to make seals and gaskets, insulation panels, and suspension bushings in cars.

Acrylonitrile Butadiene Styrene (ABS)

ABS, as its name suggests, is a polymer of acrylonitrile and styrene. It’s hard and shiny, which is why you see it used for dashboards and wheel covers.

Acrylic (PMMA)

Acrylic is a clear plastic that is strong, clear, and hard. It is used instead of glass and is used to make headlight covers and screens.

Polyamide (Nylon)

Nylon, also known as polyamide, is super tough and is used to make bushings and bearings.

Polycarbonate

Polycarbonate is a tough, hard, and durable material. Because it can handle heat and weather, it’s the best choice for making car bumpers.

Polyethylene

Polyethylene is strong, lightweight, and impact-resistant. It’s great when you need something that can handle moisture and you don’t want to spend a lot of money.

What are the Types of Injection Molding Techniques Used in the Automotive Industry?

In the car biz, we usually see three main ways to mold stuff: thermoplastic injection molding, elastomer injection molding, and thermoset injection molding.

Thermoplastic Injection Molding

Thermoplastic injection molding is the most common type of injection molding in the automotive industry. It is used to make parts out of thermoplastic materials like polypropylene, nylon, and ABS.

This car molding technique has a lot of advantages over other types of injection molding, including low cost, high production speed, and versatility.

Elastomer Injection Molding

Elastomer injection molding is used to make parts out of elastomeric materials like rubber and silicone. It has a lot of the same advantages as thermoplastic injection molding, like being cheap, fast, and versatile. Plus, it’s great at absorbing shock and reducing vibration.

Thermoset Injection Molding

Thermoset injection molding is used to make parts from thermoset materials, like epoxies and polyesters. This automotive molding technology has many of the same advantages as thermoplastic molding, like its precise dimensional tolerances and repeatability.

But it also has some advantages over thermoplastic molding. It doesn’t melt or deform easily at high temperatures, which is why automotive manufacturers choose thermoset injection molding.

What are the Advantages of Injection Molding in Automotive Applications?

Injection molding is a well-established production process where molten plastic material is injected into the mold cavity. The molten plastic cools and hardens, and the finished part is removed.

Although the mold design process is critical and challenging (poorly designed molds can lead to defects), injection molding is a reliable method for producing solid plastic parts with a high-quality surface finish.

Here are a few reasons why the process is beneficial for automotive plastic part production:

Design of Complex Shapes

Another advantage of injection molding is that it can make parts with complex shapes. Injection molding machine use a process called “screw advancement” to inject molten plastic into the mold cavity.

This process allows for the creation of highly detailed and complex parts. Also, injection molding can be used to make parts with internal cavities, like engine intake manifolds.

Repeatability

In the car biz, you gotta be able to make the same part over and over. When you make a plastic car part with a metal mold, you get the same part every time. There are a lot of things that can mess up injection molding, but if you have a good mold, you can make the same part all day long.

Scale and Cost

Injection molding can be expensive because of the cost of the mold. However, it is a highly scalable process, with the cost per part decreasing as you make more parts.

So, for mass production applications, injection molding is great. But for anything that is not mass produced, the tooling costs of injection molding can make it cost prohibitive.

Material Availability

One of the biggest benefits of using injection molding in automotive manufacturing is the wide range of rigid, flexible, and rubbery plastics that the process can handle.

Manufacturers use all sorts of different polymers for all sorts of different applications in the automotive industry, including ABS, polypropylene, acrylic, acetal, nylon, polycarbonate, and more.

High Precision and Surface Finish

Injection molding is great for making plastic parts with simple shapes that look really nice. When you make parts with injection molding, you can choose from a bunch of different surface finishes.

You can make parts that are shiny, parts that are rough, or parts that are kind of in between. You can do this by putting different textures on the mold instead of the part. But the kind of plastic you use can also change how the part looks.

Color Options

When it comes to automotive plastic injection molding, it’s easy to change the color of the molded automotive part to match the color scheme of the vehicle.

Unlike other processes, injection molding allows you to mix dyes with the raw material pellets before you start manufacturing. This gives you solid, consistent color without having to paint or tint after the molding is done.

Rapid Prototyping and Rapid Tooling

Automotive manufacturers use injection molding a lot to make car parts, but they also use it to make prototypes. They can make short runs of prototype car parts faster with rapid tooling, which is when they make fast, cheap aluminum molds—usually with 3D printing or CNC machining—instead of traditional (steel) molds.

What are the Production Applications of Automotive Injection Molding?

When it comes to making plastic car parts, injection molding is one of the main ways manufacturers do it. There are so many plastic parts in a car that are made using injection molding, it’s hard to list injection molding automotive parts all, but we’ll look at some of the big ones.

Under-the-Hood Components

Over the past couple of decades or so, a lot of manufacturers have switched to plastic for under-the-hood parts that used to be made of metal.

For these applications, strong polymers like ABS, nylon, and PET are common. But now, manufacturers use injection molding to make parts like cylinder head covers and oil pans. This method is lighter and cheaper than metal parts.

Exterior Components

Injection molding is a process that’s been around for a while and is used to make a lot of the outside parts on cars, like fenders, grilles, bumpers, door panels, floor rails, light covers, and more.

Splash guards are a good example of how tough injection molded parts can be. They’re usually made out of rubber or some other tough, flexible material and they’re there to keep rocks and stuff from hitting the car and to keep water from splashing up on the car.

Interior Parts

Automotive plastic injection molding is also used by manufacturers to make a lot of automotive interior parts. These include instrument components, interior surfaces, dashboard panels, door handles, glove boxes, air vents, and more. They also use injection molding to make decorative plastic elements.

In some high-performance cars, carbon fiber reinforced plastics is often used in key structural components (such as body panels, roof, chassis) to achieve optimal performance and weight optimization.

Conclusion

Injection molding is used in many industries for mass production. The cost per part is low once you have paid for the molds and tooling. Injection molding is a good solution for car makers who need to make a lot of parts and make them complicated.