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The Complete Guide to Automotive Plastic Design

Updated: Feb 7

Automotive Plastic Design - BK Enineering

Introduction to Automotive Plastic Design

Automotive plastics have revolutionized vehicle design and construction over the past decades. Plastics now make up over 50% of a car's volume but account for only about 10% of its weight. Automakers have increasingly adopted plastics to reduce weight, improve design freedom, provide cost savings, and meet performance goals.

Plastics offer major advantages over traditional automotive materials like metals. They are much lighter and allow for greater styling and design flexibility. Plastics don't rust, which improves durability and longevity, especially for exterior components. Plastics provide noise and vibration-dampening properties important for interiors. They are also electrically insulating and don't corrode. High-strength plastics like reinforced composites have enabled sleek, lightweight external body panels.

From dashboards to bumpers, under-hood components to lighting, plastics are ubiquitous in modern automotive manufacturing.

Using plastics leads to lighter, more fuel-efficient vehicles. The drive toward sustainability, emissions reductions, and increased range for battery electric vehicles will further accelerate the use of plastics to reduce vehicle weight. Beyond improved fuel economy, plastics contribute to performance. Lighter weight from plastic components allows for faster acceleration and better handling. The unique properties of plastics make them an essential material technology for automotive engineers.

Automotive Design Process

The automotive design process is a systematic approach used by manufacturers to develop vehicles that meet the needs and expectations of consumers while adhering to industry standards and regulations. Here's an overview of the typical steps involved in the automotive design process:

1. Concept Development: The design process begins with conceptualizing ideas for new vehicles or improvements to existing models. Designers gather input from market research, consumer feedback, and industry trends to create concept sketches and renderings that capture the desired aesthetics and functionality of the vehicle.

2. Design Sketching: Sketching is a crucial step in the design process, allowing designers to explore different concepts and refine their ideas. Initial sketches may be done by hand or using digital drawing tools, providing a visual representation of the vehicle's exterior and interior features.

3. Digital Modeling: Once a concept is chosen, designers create digital 3D models using computer-aided design (CAD) software. Digital modeling allows for precise detailing and manipulation of the vehicle's surfaces, enabling designers to refine the proportions, contours, and features of the vehicle.

4. Clay Modeling: Clay modeling is often used in conjunction with digital modeling to further refine the design and assess its physical proportions and aesthetics. Designers sculpt scale models of the vehicle using clay, allowing them to visualize the design in three dimensions and make adjustments as needed.

5. Engineering Development: After finalizing the design, engineers begin the development phase, where they assess the feasibility and functionality of the vehicle. This includes structural analysis, aerodynamic testing, and component integration to ensure that the vehicle meets performance, safety, and regulatory requirements.

6. Prototype Construction: Prototyping involves building physical prototypes of the vehicle to validate the design and engineering concepts. Prototypes may be produced using rapid prototyping techniques like 3D printing or traditional manufacturing methods, allowing designers and engineers to test the vehicle's performance and functionality in real-world conditions.

7. Testing and Validation: Prototypes undergo rigorous testing and validation to assess their performance, durability, and safety. This includes vehicle crash testing, emissions testing, and reliability testing to ensure that the vehicle meets or exceeds regulatory standards and customer expectations.

8. Production Planning: Once the design and engineering are finalized, production planning begins, including selecting manufacturing processes, sourcing materials, and optimizing assembly line processes. Manufacturers aim to streamline production while maintaining high quality and cost efficiency.

9. Mass Production: With production plans in place, the vehicle enters mass production, where it is manufactured in large quantities for distribution to dealerships and consumers. Production facilities utilize advanced robotics, automation, and quality control measures to ensure consistency and efficiency in the manufacturing process.

10. Launch and Marketing: The final step in the automotive design process is the launch and marketing of the vehicle. Manufacturers unveil the vehicle to the public through marketing campaigns, auto shows, and dealership events, generating excitement and interest among potential customers. Effective marketing strategies play a crucial role in driving sales and establishing the vehicle's reputation in the market.

Automotive BIW (Body in White) and Trims

In the automotive industry, the term "Body in White" (BIW) refers to the stage of manufacturing where a car's body structure is assembled before painting. It represents the skeleton of the vehicle, consisting of all structural components such as the frame, chassis, and body panels. The BIW serves as the foundation upon which other components, including interior and exterior trims, are installed.

Body in White (BIW):

Structure: The BIW encompasses the structural framework of the vehicle, including the floorpan, roof, pillars, and side panels. These components are typically constructed using high-strength steel or lightweight materials like aluminum to provide rigidity, durability, and crash protection.

Assembly: BIW assembly involves joining individual body panels and structural components using various welding techniques such as spot welding, MIG welding, and laser welding. Advanced robotics and automation are often utilized to ensure precise assembly and alignment of components.

Integration: Once assembled, the BIW undergoes extensive quality control checks to verify dimensional accuracy, structural integrity, and adherence to design specifications. Any defects or imperfections are addressed before proceeding to the next stage of production.

Interior Trims:

Definition: Interior trims refer to the components and materials used to finish the interior surfaces of a vehicle, including the dashboard, door panels, seating, and headliner. These trims serve both functional and aesthetic purposes, enhancing comfort, style, and convenience for occupants.

Materials: Interior trims are often made from a variety of materials, including plastics, fabrics, leather, wood, and metal. The selection of materials depends on factors such as durability, aesthetics, cost, and regulatory requirements.

Design and Integration: Interior trims are designed to integrate seamlessly with the vehicle's interior architecture, complementing the overall design theme and enhancing the user experience. Designers focus on factors such as ergonomics, tactile feel, and visual appeal to create inviting and functional interior spaces.

Exterior Trims:

Definition: Exterior trims encompass the components and features located on the outer surfaces of the vehicle, including bumpers, grilles, side moldings, and trim panels. These trims serve both aesthetic and functional purposes, enhancing the vehicle's appearance and protecting against environmental elements.

Functionality: Exterior trims play a crucial role in aerodynamics, impact protection, and pedestrian safety. They are designed to withstand harsh weather conditions, UV exposure, and road debris while maintaining their appearance and structural integrity.

Design and Styling: Exterior trims are designed to reflect the vehicle's design language and brand identity, incorporating elements such as sleek lines, bold contours, and distinctive features. Designers use advanced CAD software and prototyping techniques to visualize and refine exterior trim designs before production.

Design Principles for Plastic Parts in Automobile

Proper design is critical for plastic automotive parts to function as intended. Some key design principles to follow include:

Functional Requirements

Plastic parts in automobiles must fulfill specific functional requirements to ensure optimal performance and usability. These requirements may include structural integrity, dimensional accuracy, thermal stability, and resistance to environmental factors such as moisture, chemicals, and UV exposure. Designers must carefully consider these functional requirements during the design phase to meet the demands of the automotive application.

Material Selection

Selecting the appropriate material is crucial for the performance and longevity of plastic automotive parts. Factors to consider when choosing materials include mechanical properties (such as tensile strength, impact resistance, and flexibility), thermal properties, chemical resistance, and cost-effectiveness. Common materials used in automotive plastics include ABS, polypropylene, polycarbonate, and polyethylene. The selected material should meet the specific requirements of the application while also being compatible with the manufacturing process and cost constraints.


Reliability is paramount in automotive design, as plastic parts must withstand various operating conditions without failure. Designers must ensure that plastic parts are engineered to withstand mechanical loads, temperature fluctuations, vibration, and other stressors encountered during vehicle operation. Additionally, reliability testing, such as fatigue analysis and accelerated aging tests, should be conducted to verify the durability and longevity of plastic components in real-world conditions.

Design for Assembly (DFA) and Design for Manufacturing (DFM)

DFA and DFM principles aim to simplify assembly processes and optimize manufacturing efficiency, respectively. Designers should consider factors such as part orientation, ease of access for assembly, and minimizing the number of components to streamline production. Additionally, designing parts with uniform wall thickness, avoiding sharp corners, and minimizing undercuts can facilitate moldability and reduce manufacturing complexities.


Economic considerations play a significant role in automotive plastic part design, as cost-effectiveness is essential for mass production. Designers must balance performance requirements with cost considerations to ensure that the final product is both functional and economically viable. Optimizing material usage, minimizing scrap, and maximizing manufacturing efficiency are essential strategies for achieving cost-effective plastic part designs.

By incorporating fundamental design features like draft angles, optimized wall thickness, strategic rib placement, and engineered bosses and snap fits, automotive plastic parts can meet demanding functional requirements in vehicles. Proper plastic product design is crucial for manufacturability, performance, and durability.

CAD Software for Plastic Design in Automobiles:

In the automotive industry, precision and efficiency are paramount, especially when it comes to designing plastic components. CAD (Computer-Aided Design) software plays a crucial role in facilitating the creation of intricate plastic parts, from interior trims and dashboard components to exterior panels and structural elements. Here, we explore some of the leading CAD software used for plastic design in automobiles:

CATIA (Computer-Aided Three-Dimensional Interactive Application):

  • Developed by Dassault Systèmes, CATIA is a versatile CAD software widely used in the automotive sector for its robust capabilities in surface modeling and complex geometry creation.

  • With specialized modules like CATIA Surface Design, designers can sculpt aesthetically pleasing surfaces while ensuring precise engineering tolerances and manufacturability.

  • CATIA's extensive toolset allows for the creation of Class-A surfaces, which are crucial for achieving high-quality exterior finishes and seamless transitions between body panels.

  • Its parametric modeling features enable iterative design refinement, facilitating collaboration between designers and engineers throughout the product development cycle.

Siemens NX (formerly Unigraphics or UG):

  • Siemens NX is another popular CAD software utilized in automotive plastic design for its advanced surface modeling capabilities and comprehensive toolset for mold design and manufacturing.

  • With NX's integrated suite of tools, designers can seamlessly transition from concept design to detailed engineering, ensuring that the final product meets both aesthetic and functional requirements.

  • The software's simulation capabilities enable designers to validate designs for structural integrity, mold filling, and part manufacturability, reducing the risk of costly errors during production.

  • Siemens NX's parametric modeling and synchronous technology empower designers to make rapid design iterations and accommodate changes in design requirements efficiently.

CATIA for Creative Designers (CATIA ICEM):

  • CATIA ICEM is a specialized module within the CATIA suite, designed for creative designers and surface modeling experts who require precise control over surface geometry and curvature continuity.

  • Ideal for creating Class-A surfaces and complex sculpted forms, CATIA ICEM offers a range of tools for freeform surface modeling, curvature analysis, and surface refinement.

  • Automotive designers often utilize CATIA ICEM for developing concept car designs, futuristic prototypes, and high-end luxury vehicle exteriors, where aesthetic appeal is paramount.

  • The software's integration with other CATIA modules ensures seamless data exchange and collaboration across design and engineering teams, streamlining the product development process.

Autodesk Alias:

  • Autodesk Alias is a versatile CAD software widely used in automotive design, including the creation of plastic components such as interior trims, instrument panels, and exterior body panels.

  • Known for its intuitive surface modeling tools and visualization capabilities, Alias enables designers to explore creative concepts and iterate rapidly to achieve desired design aesthetics.

  • With features like dynamic shape modeling and subdivision surface modeling, Autodesk Alias empowers designers to sculpt organic forms and intricate details with precision and ease.

  • The software's compatibility with other Autodesk products, such as Autodesk VRED for visualization and Autodesk Fusion 360 for collaboration, enhances its usability in automotive design workflows.

These CAD software tools serve as indispensable resources for automotive designers and engineers, providing the tools and capabilities needed to create innovative, functional, and aesthetically pleasing plastic components that define the modern automobile.

Common Plastics Used in Cars

The automotive industry relies on several types of plastic for various components and parts. Some of the most common plastics used in car manufacturing include:

ABS (Acrylonitrile Butadiene Styrene)

ABS is widely used in interiors like instrument panels and door liners. It has high impact strength, toughness, and rigidity. Styrene provides gloss and hardness, while acrylonitrile offers chemical resistance. The butadiene improves ductility and impact strength. Key properties:

  • High dimensional stability and tensile strength

  • Good thermal stability and chemical resistance

  • Excellent flow during molding

ABS resins are used for grilles, exterior trim, bumper fascia, wheel covers, instrument panels, and more.


Polypropylene has high flexural strength and is lightweight and economically priced. It has good chemical resistance and fatigue strength. Key properties:

- Resistant to acids, alkalis and solvents

- Good fatigue and creep resistance

- Low-density and cost-effective

Polypropylene is used for interior trim, battery cases and trays, bumper fascia, fender liners, instrumental panels, door panels, and seats.


Polyurethane exhibits abrasion resistance, high resiliency, and good load-bearing capacity. It demonstrates toughness even at low temperatures. Key properties:

- Excellent abrasion resistance

- Good load-bearing capacity

- High tear strength and resiliency

Polyurethane is used in car seats, armrests, instrument panels, trim components, and structural body parts.

PVC (Polyvinyl Chloride)

PVC has high hardness and mechanical properties. It also demonstrates chemical and electrical resistance. Key properties:

- Toughness and durability

- Good mechanical strength

- Abrasion and chemical resistance

PVC is commonly used for mudguards, dashboards, sheaths for electrical cables, and underbody coating.

This covers some of the major plastics used in the automotive industry and their typical applications. The choice of plastic depends on factors like cost, production method, mechanical and thermal requirements, and performance needs.

Plastic Production Processes

Injection molding is the most common process for producing plastic parts in the automotive industry. This manufacturing method involves injecting molten plastic into a mold cavity, where it cools and hardens into the final part shape. Injection molding enables high-volume production of complex, three-dimensional plastic parts with excellent finishes, dimensional accuracy, and material properties.

Extrusion is used to create long plastic profiles with consistent cross-sectional shapes. This process pushes melted polymer through a die, forming it into tubes, rods, or sheets as it cools. Extrusion allows the continuous production of items like plastic trim strips and body-side moldings on vehicles.

Thermoforming starts with a plastic sheet that is heated until pliable, then formed against a mold using vacuum, air pressure, or mechanical means. It can produce large, lightweight exterior body panels for cars at a lower cost compared to other methods.

3D printing has evolved as an alternative process for creating custom plastic parts, prototypes, and tooling in low volumes for the automotive industry. Selective laser sintering, fused deposition modeling, and stereolithography are some of the common 3D printing technologies used. The layer-by-layer approach provides design freedom and rapid turnaround.

4.Plastic Welding and Joining

Plastic parts in automotive applications often need to be joined together or to other materials. There are several techniques used for welding and bonding plastics in vehicle manufacturing.

Ultrasonic Welding

Ultrasonic welding is commonly used to join thermoplastic parts. It works by creating high-frequency vibrations that are applied to the plastic components under pressure. The vibrations generate heat through friction which melts and fuses the plastics together. The main advantages of ultrasonic welding are speed, low temperature, simplicity, and flexibility. It is an automated process suitable for high-volume production.

Vibration Welding

Similar to ultrasonic welding, vibration welding relies on high-frequency vibrations under force to generate heat between plastic parts. However, instead of ultrasonic frequencies, lower vibrational frequencies are used. The parts are held together and one component is vibrated against the other until the contact surface reaches melting temperature. The motion is then stopped and the parts solidify together. The benefits are fast cycle times and suitability for complex geometries.

Hot Plate Welding

Also known as hot gas welding, hot plate welding heats the plastic components using a heated plate placed between the parts. Pressure is applied to push the molten surfaces together and allow fusion. The plate can either move between stationary parts, or the parts can be mo...

Key Considerations in Plastic Design:

Functional Requirements: The foremost consideration in plastic design is understanding the intended function of the component or product. Whether it's a structural element in an automotive assembly or a housing for electronic devices, the design must align with its functional purpose.

Material Selection: Choosing the right material is paramount in plastic design. Factors such as mechanical properties, chemical resistance, thermal stability, and cost must be meticulously evaluated to ensure optimal performance and longevity.

Ergonomics: Human factors and ergonomics play a crucial role, especially in consumer products. Designers must consider user comfort, accessibility, and usability to enhance the overall user experience.

Manufacturability: Designing for manufacturability is essential to streamline production processes and minimize costs. Factors such as moldability, tooling complexity, part geometry, and assembly considerations must be carefully addressed during the design phase.

Aesthetics: While functionality is paramount, aesthetics also play a significant role in plastic design. Attention to detail, surface finish, color selection, and branding elements contribute to the overall visual appeal of the product.

In conclusion, automotive plastic design has revolutionized vehicle manufacturing, offering lightweight, durable, and versatile solutions for various components. Through systematic design processes, advanced CAD software, and innovative manufacturing techniques, designers can create high-performance, aesthetically pleasing, and cost-effective plastic parts. By prioritizing functionality, material selection, manufacturability, and aesthetics, automotive plastic design continues to drive innovation and efficiency in the automotive industry, shaping the future of vehicle design and performance.

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