Home Technology & Safety Design Considerations for Plastics – Here’s How Plastic Components Are Designed To Increase Manufacturability
Design Considerations for Plastics – Here’s How Plastic Components Are Designed To Increase Manufacturability

Design Considerations for Plastics – Here’s How Plastic Components Are Designed To Increase Manufacturability


Today, you can find plastic components in almost all subsystems of the vehicle, including the engine compartment, the interior cabin and the exterior of the vehicle. In the age of energy efficiency, engineering plastics are increasing potential to lower vehicle weights, meaning reducing fuel consumption. Plastics are also highly versatile, and possess longer lifespans.

Plastics are typically formed through injection molding. During the manufacturing process, automotive engineers consider numerous elements to ease the production and manufacturability of plastic components.

Here are some aspects engineers look at to increase plastic component manufacturing:

Draft Angles

Green illustration shows correct draft angle and red shows a lack of draft angles

(Picture Source: medium.com)

Draft angles provide significant ease for the solidified plastic to be removed from its mold. The absence of draft angles produces very high friction between the plastic and its mold which will cause the plastic to scrape against the edges of the mold. The scraping can cause unwanted marks on the surface of the plastic and it can also lengthen the time of manufacturing (cycle time).

For more information, watch the video below:


Red illustration shows lack of ribs and green illustration shows correct addition of ribs

(Picture Source: medium.com)

Ribs are an effective way to improve the rigidity and strength of molded parts. With proper implementation, ribs will also be able to reduce weight, shorten molding cycles and eliminate heavy cross section areas which could cause molding problems. Ribs can also enhance the strength of thin plastic components as usage of ribs can be executed without adding to wall thickness.

Usually, ribs are used in two situations – (a) where a part has 90-degree angled walls that meet, or (b) when where a part may be too long or large and the wall thickness leaves the part flimsy or weak. In some cases, ribs are also used to provide alignment, provide stopping surfaces for assemblies and as decorative features.


Boss feature in plastic parts such as Lego bricks

(Picture source: Wikipedia)

Products are generally composed of two or more parts connected together. A “connector” is usually needed to connect these parts together. In the manufacturing of plastic components, boss is a basic design consideration that is used for mounting purposes or to serve as reinforcement around holes. It is typically cylindrical in shape. One of the most common examples of the usage of boss can be witnessed in Lego bricks. The underside of the brick consists of cylindrical holes while on the surface are smaller, protruding cylindrical parts. When pressed against one another, these two parts “click” and connect.


Example of radiused corners on the design of a plastic part

(Picture source: medium.com)

Adding radius to edges and corners of plastic components (both inside and outside) is another method to prolong the life of a plastic component. Designing a radiused edge instead of a sharp edge will prevent the formation of cracks due to stress concentration. Having a radius also allows for better removal during the fabrication process. Plastic components with radiused edges can also reduce chipping, simplify mold construction while also being more economical and easier to produce.

Part Lines

Example of a part line on a screwdriver

(Picture source: medium.com)

Plastic components are usually molded in two halves. Once they are solidified, they will be fused together. Part lines are where the two halves of the mold meet. Part lines are not only visible but are also noticeable to the touch. Hence, while designing a plastic component, it is important for designers and engineers to always consider the location of the part lines and to make sure they do not disrupt the aesthetics and the functionality of the product.

For more information, watch the video below:

Ejector Pin Locations

Arrows point to ejector pin marks on a plastic battery holder plastic

(Picture source: medium.com)

Ejector pins are a tool that is used to aid the removal of the part from the mold. However, while performing its task of removing the mold, the ejector pin will tend to leave marks on the part. Plus, these marks are not removable. Hence, it is vital for designers and engineers to consider the location of the ejector pins while designing the part.

For more information, watch the video below:

Designers and engineers in automotive industries make use of tools such as these to assist them in the product development stage while ensuring quality requirements are met. This also makes it possible to manufacture vehicles with cost and mass reduction, developed in shorter periods of time. This process of continuous improvement and optimization will enable the automotive industry to continuously expand and reach greater milestones.

Do you have specific knowledge on this subject, and would like to contribute to the knowledge pool? Contribute an article, send an email to editorial@mai.org.my with the title – Automotive Community Article!