In the early days of automotive industry, car was almost entirely made from metal parts. As the industry started to evolve in the 40s and 50s, automotive manufacturers began to experiment with plastic car parts in their production. They quickly realized the potential of using such material in the production of car parts, as it helped to improve the efficiency of the vehicles thanks to an economy in weight and production cost. With the development of automotive industry in the following decades, plastic gained importance, and functional parts like plastic headlights, bumpers, and fenders made their apparition in the 80s. Today, injection moulding is a dominant production method for manufacturing plastic car parts in the automotive industry.
In this article, we will discuss the advantages of injection moulding in automotive parts production and its application.
The advantages of using injection moulding.
Injection moulding is now one of the predominant methods manufacturers use to produce plastic parts. It offers a viable solution for the mass production of high-quality parts in an industry where consistency, safety, and quality are of utmost importance. Today's cars on average are made of about 50% plastic by volume but only 10% by weight. It shows the benefits from using such material instead of metal for parts production. So here are a few reasons why the process is beneficial for automotive plastic parts production:
1. Repeatability
In the automotive industry, repeatability, or the ability to consistently produce identical parts, is crucial. Because automotive plastic injection moulding typically relies on robust metal mould, the final moulded automotive parts produced using the mould are practically identical. Some factors come into play with injection moulding, but injection moulding is a highly repeatable process if the mould has a good design and finishing.
2. Scale and cost
The injection mould-making process can be an expensive process due to the cost of the mould. However, it remains a highly scalable process whose overall cost decreases as the manufacturer makes more parts. For mass production applications, injection moulding is thus beneficial to the manufacturer. For anything less than mass production, however, injection moulding tooling costs may curb the cost efficiency of the process.
3. Material availability
A significant benefit of using injection moulding for automotive production is the wide range of rigid, flexible, and rubber plastics the process is compatible with. Manufacturers use a wide range of different polymers for various applications in the automotive industry, including ABS, polypropylene, acrylic, acetal, nylon, polycarbonate, and more.
4. High precision and surface finish
Injection moulding is ideal for producing plastic parts with relatively simple geometries and results in high surface finish quality. Manufacturers have many finish options when producing parts, including various surface textures—such as glossy, rough, or matte—which they apply directly to the mould rather than the moulded part. However, different plastic materials also influence the final surface finish.
5. Colour options
In automotive plastic injection moulding, it is easy to modify the colours of moulded automotive parts to fit the vehicle’s colour scheme. Unlike other processes, injection moulding allows you to mix dyes with the raw material pellets before manufacturing begins. This produces solid, consistent coloration without the need for painting or tinting after the moulding is complete.
6. Fast prototypes with rapid tooling
Although automotive manufacturers widely use injection moulding for mass production of auto parts, they also use it as a prototyping tool. By creating fast, low-cost aluminium moulds with rapid tooling — usually by additive manufacturing or CNC machining — automotive mould manufacturers can turn around short runs of prototype moulded car components much faster than traditional (steel) tooling.
Automotive parts produced using injection moulding.
With so many advantages and such a big volume of plastic used in car production, it would be impossible to list all the parts that are made of plastic, so we will focus on the most important ones.
1. Under-the-hood parts
As said in the introduction, the use of plastic in car parts production has increased very quickly throughout the years, to reach new applications every decade. Many under-the-hood parts were formerly made from metal, until the 2000s when they transitioned to plastic. Manufacturers now make parts such as cylinder head covers and oil pans using injection moulding. This method offers lower weights and costs compared to metal parts.
2. Exterior parts
Many exterior components like fenders, grilles, bumpers, door panels, floor rails, light housings or splash guards are made with injection moulding and are the most visible parts made from this process. Splash guards are actually a great example to demonstrate the durability of this production process, as the purpose of this part is to protect the vehicle and the components are often made from rubber or other durable and flexible materials.
3. Interior parts
Manufacturers also produce many automotive interior parts using automotive plastic injection moulding. They include instrumentation components, interior surfaces, dashboard faceplates, door handles, glove compartments, air vents, and more. In addition, they also use injection moulding for producing decorative plastic elements.
In conclusion, plastics have been used to serve as an alternative to metals, and injection moulding is now the preferred production method for many car components. However, the quality of the parts also relies on the material that will be used in the injection moulding production process, and it is the responsibility of automotive producers to build their vehicles according to the rigorous safety standards to become roadworthy.
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