Automotive Injection Moulding: Explained

The automotive industry relies heavily on injection moulding to produce large-scale, precision plastic parts. This key manufacturing process plays a crucial part in creating high-quality, cost-effective parts and components such as bumpers, dashboard panels, and wheel arches.

Below, we’ll detail how injection moulding works, its importance in automotive manufacturing, and why it’s likely to remain a pillar in the manufacturing of cars.

What is injection moulding in automotive?

Injection moulding is a manufacturing process that involves injecting molten plastic into a mould to create parts with high precision. In the automotive industry, this technique is critical for producing parts and components that meet stringent performance, safety, and aesthetic standards. Injection moulding is known for speed and precision, leading to less wasted materials, energy, and time.

This method supports the mass production of vehicle parts, making it highly cost-effective for OEMs aiming to produce thousands – or even millions – of components.

Additionally, injection moulding is compatible with a wide range of plastics such as polypropylene, acrylonitrile butadiene styrene (ABS), and polycarbonate, offering a range of material properties like durability, flexibility, and lightweighting, depending on the need of the OEM for a particular component.

This lines up perfectly with the principle of lean manufacturing, minimising waste and optimising efficiency, to contribute to sustainable production practices.

The injection moulding process

Injection moulding follows a detailed step-by-step process to ensure precision and consistency:

Step 1: Preparation of molten plastic
Granules of the desired plastic(s) are fed into a heated barrel, where they are melted and mixed to achieve the desired consistency.

Step 2: Injection of plastic into the mould
The molten plastic is injected into a custom-designed mould under high pressure, ensuring it fills every cavity and detail.

Step 3: Cooling and solidification
Once inside the mould, the plastic cools and solidifies into the shape of the component. The cooling time depends on the type and thickness of the material. 

Step 4: Ejection of the finished part
After solidification, the mould opens, and the finished part is ejected using pins or plates. The component is then inspected for quality before moving to the next stage of the production line.

Applications in automotive components production

Since the invention of the first injection moulding machine, manufacturers have relied on injection moulding to meet a variety of needs quickly and efficiently without compromising on the quality of their final product.

Injection moulding is used to produce a wide array of automotive components, such as:

Exterior parts

• Bumpers
• Wheel arches and mudguards (fenders)
• Sensor holders and floor rails
• Exterior door trims

Interior components

• Dashboard panels, including glove compartments
• Door and window pillars
• Trims and door handles

Functional parts

• Brackets and connectors
• Clips and fasteners

Modern safety standards require consistency among components, which is why injection moulding is so widely used. It reliably provides uniform, safe components almost every time. Some experts claim a less than 1% rejection rate for injection moulding.

Advantages of injection moulding for automotive parts

Injection moulding offers numerous benefits that make it such a popular choice within  automotive manufacturing: 

• Increased production efficiency: Injection moulding enables fast high volume production of consistently high quality parts. 
• Cost-effectiveness: Automotive injection moulding is a cost-effective process thanks to faster production times, lower material costs and reduced labour expenses. Once the moulds are ready, reproducing parts can become an automated process.
• Design flexibility: Injection moulding offers unmatched design flexibility, allowing manufacturers to create complex and intricate automotive parts and components with functionality and aesthetics at the forefront.
• Lightweight components: Plastic injection moulded parts are significantly lighter than traditional metal parts. In turn, this reduces the vehicle’s weight, allowing for improved fuel efficiency and aerodynamics.
• Durability and strength: Injection-moulded parts are created using high-performance plastics designed to withstand high temperatures and mechanical stress.
• Aesthetic benefits: Colourants and surface textures can be added to produce components and parts that meet OEM requirements.
• Waste reduction: Excess material is often recyclable, supporting sustainable practices, and further reducing cost.
• Material versatility: A wide range of plastics can be tailored to specific needs, whether that’s a heat-resistant component in the engine bay or a flexible component in the bodywork.

Plastic components in modern-day auto production

Plastic components are vital in modern vehicles, contributing to performance, sustainability, and flexibility in design that wasn’t available to manufacturers in previous decades. Here are some of the major benefits of plastics in automotive production today.

Versatility

Plastics are so widely used because of their versatility. By using different types of plastic, manufacturers can determine the heat resistance, flexibility, rigidity, etc. of their panels.

Sustainability

By using recycled or bio-based plastics, the use of injection moulded plastic can contribute to long-term sustainability goals. The reduction of waste will also mean less material and energy wasted.

Alternatives to injection moulding plastic car parts

While injection moulding is a leading method, other techniques are used in automotive plastic part production:

• Compression Moulding: Compression moulding is similar to injection moulding. Rather than injecting the heated plastic into a mould, the plastic is pressed into the mould.
• Blow Moulding: This technique is used to fill hollow moulds for things like tanks. Compressed air is used to spread the plastic in a mould.
• 3D printing: Ideal for prototyping and small-batch production. Unfortunately, it’s a timely process that isn’t suited for large-scale operations as yet.
• Thermoforming: This is the process of applying a material over a mould when it is hot so that it will cool in the shape of the mould. It is commonly used for components like dashboards and door panels.
•  Rotational moulding: Similar to blow moulding, rotational moulding is ideal for components that are hollow, like tanks. The hot material is poured into the mould, while the mould rotates and cools the material so that it hardens in the desired shape.
• Extrusion: Extrusion produces continuous lengths of material, such as tubing, by forcing material through a long tube and cooling to the desired shape.

Key injection moulding considerations for OEMs

OEMs must weigh several factors when using injection moulding, which might affect the extent to which they use it in their manufacturing.

Collaboration with experienced suppliers

Partnering with the correct companies ensures access to advanced moulding technologies and materials, delivering even more efficiency.

 Balancing cost, quality, and timelines

Efficient project management is critical to take advantage of the benefits of injection moulding. The time savings that it delivers must be utilised to provide a better product or service to the customer.

Sustainable practices and materials

Incorporating recycled or bio-based plastics into the injection moulding process can support environmental goals, making it a key aspect of the automotive industry moving forward.

Injection moulding remains essential to modern automotive manufacturing, offering precision, scalability, and material versatility.

By integrating sustainable practices and collaborating with experienced suppliers, OEMs can enhance their production capabilities and meet evolving market demands.