Mechanical design engineer: Why care about learning plastic design?-Part 2 - CADCAMGURU Institute

Mechanical design engineer: Why care about learning plastic design?-Part 2

Plastics is playing a critical role in creating lightweight and fuel-efficient vehicles. It helps the companies to remain competitive in the market. This is leading to an increased demand for plastics in automobile sector.

We have discussed the reasons for using plastics in manufacturing in greater details in our blog  Read Part -1

 Here we will discuss on type of plastic and some key manufacturing processes.

Plastic, Plastic and More Plastic

There are 39 different types of plastic used in automobiles. Much of the plastic is used in several systems in the car like safety components, including Airbags and restraints, Electrical systems, Chassis design, Powertrains, Fuel systems, Engine components. Here is the table from the report of SPI: The Plastics Industry Trade Association.

Doors & Trim SystemsInstrument Panels, Consoles & CockpitsFlooring & Acoustic SystemsHeadliner & Overhead SystemsOther Interior & Exterior Components
Door panelsInstrument panelsFloor carpetsOverhead systemsInterior
Acoustic InsulatorsAcoustic insulatorsAcoustic insulatorsAir distribution ductsCargo management
ArmrestsAir duct systemsEngine insulatorsAssist handlesLoad floors
Decorative appliquésAir registersExpandable sealingCoat hooksSeat components
Garnish trimCenter consolesFloor matsGarnish trimExterior
Hard & soft panelsCockpitsHeat shieldsHeadliner substratesFascias
Map pocketsCupholdersPackage traysInterior lightingGarnish trim
Safety componentsDecorative appliquésTrunk trimOverhead consolesRec. vehicle trim
Speaker grillsGlove box assembliesUtility flooringSafety componentsReservoir systems
Switch bezelsHard & soft panelsWheel arch linersVisorsRocker panels

Plastics and its Main Types

Plastics are organic materials and hydrocarbons. They are obtained out of a process chemically called as polymerization where chains of carbon and hydrogen atoms are formed due to application of heat, pressure or due to some chemical reaction. The physical formation of any plastic component is due to direct linkage or cross linkage of the chains of polymers. Plastic raw material is available in form of granules or viscous liquid.

The plastic materials can be broadly classified in two groups.


These materials are available in solid form. They soften due to application of heat at temperature around 150°- 300°. At their softened (viscous liquid) state, they can be given a desired shape. They can solidify after subsequent cooling to room temperature. The process of softening (liquification) and solidifying can be carried out number of times.

Common types are Polyethylene (PE), Polypropylene (PP), Nylon, Polyvinyl Chloride (PVC), Polyestyrene, Acrylic.

Thermosetting plastics

These materials are available in solid form or thick viscous liquid form. If solids, they soften at lower temperatures and get solidified at higher temperature (around 250° C) or at higher pressures. For the materials in thick viscous liquid form, some chemical reaction can lead to their solidification. However, after such solidification, no softening due to heating again is possible. Application of heat may only burn the material.

The common types are Phenol Formaldehyde, Melamine Formaldehyde, Epoxy resins, Hard PVC, Bakelite, Urea formaldehyde, etc.

Thermosetting plastic components are harder, rigid and can withstand comparatively high temperatures. For engineering applications, use of thermoplastics is more common as compared to the thermosetting plastics.

Choosing Right Manufacturing process

Wide variety of plastic manufacturing processes are available based upon type of plastic, its application and geometries needed. Here are some of the factors which play a key role in choosing the manufacturing process.

FormComplex structure of partsVery tight tolerancesComplex geometrical shapes
VolumeHigh volume or Low volumeVolume would decide the cost.
Cost/BudgetTotal cost = Cost of tooling + Cost of partHigh volume will have expensive set up
Cost/BudgetTotal cost = Cost of tooling + Cost of partHigh volume will have expensive set up
Cost/BudgetTotal cost = Cost of tooling + Cost of partHigh volume will have expensive set up

Now let us touch upon some of the most widely used manufacturing processes for plastic components.

Blow moulding

Blow moulding is method of blowing heated plastic. It is used to create the plastic parts which are hollow by blowing a heated plastic tube inside a mould. Heated plastic tube takes the desired shape of the mould. This method is used for production of plastic bottles, cans, containers, etc.


Extrusion is used to manufacture objects of fixed cross-sectional profile. In this method, plastic is pushed through a die. This method is useful for production of plastic pipes, tubes, bags, conduits.


Thermoforming is a manufacturing process where a plastic sheet is heated to soften and then put inside a mould to give it a desired shape. It is then trimmed if needed and the final product is created. This method is used for transparent film packaging of consumer products like toothbrushes, shaving blades, soaps, toys, dry articles, capsules, etc.

Injection moulding

Injection molding (IM) is a manufacturing process which creates objects by injecting molten thermoplastic into a mould. It is the most widely used process for mass manufacturing of plastic parts. This is very useful for complex shaped products as car interiors, suitcases, baskets, furniture spares, utensils, cell phone and calculator bodies, presentation articles, knobs, handles etc.

Why care about plastic design?

As more and more parts in the automotive are manufactured using plastics, it is obvious that knowledge of these processes will become crucial for a design engineer. He /She must know what the best manufacturing option is available today and in near future. You would develop a good understanding of plastic components from design perspective with a professional training course Product and Tool Design Engineer from CADCAMGuru.

We will touch upon design considerations for manufacturing of plastic components in our next blog.  Read Part-3