In the automobile industry today, the substitution of plastics for expensive metal materials has become an inevitable trend. High-strength engineering plastics not only reduce the cost of parts processing, assembly, and maintenance but also make cars lighter, more energy-efficient, and environmentally friendly.
Data shows that plastics and their composites are the most important lightweight materials for cars. They can reduce the weight of parts by about 40% and decrease the purchase cost by approximately 40%. Consequently, their usage in automobiles has rapidly increased in recent years, making them the “new favorite” in automobile manufacturing.
Therefore, ensuring the consistency of materials between the development stage and the production stage of an automobile is particularly important.
Question: Is it possible for the materials used in the prototype stage to be consistent with those used in the final production?
In this article, we will share information about the materials and options for CNC machining services in China during the prototype phase of automobile development.
What’s the Mainstream Automotive Engineering Plastics?
Currently, the most commonly used general plastics in automobiles include polypropylene (PP), ABS resin, PVC, and PE. Polyolefin materials constitute the main plastic parts of cars. Below are several mainstream automotive engineering plastics:
Polypropylene (PP)
PP is used in a variety of auto parts, and in a typical passenger car, PP plastic parts account for more than 60%. Main varieties of PP auto parts include:
- Bumpers
- Dashboards
- Door interior panels
- Air conditioner parts
- Battery cases
- Cooling fans
- Steering wheels
The first five types alone account for more than half of the total PP usage.
Polyethylene (PE)
Through graft modification and filling toughening modification of high-density PE and low-density PE resin, a series of modified PE alloy materials with good flexibility, weatherability, and coating performance are obtained. PE mainly uses the blow molding method to produce:
- Fuel tanks
- Ventilation pipes
- Flow deflectors
- Various storage tanks
In recent years, the consumption of PE in cars has not increased significantly. However, the trend towards car lightweighting promotes the plasticization of fuel tanks. Plastic fuel tanks, primarily made of high molecular weight high-density polyethylene (HMWHDPE), are now officially used in cars in Europe.
Polyoxymethylene (POM)
POM has excellent properties such as:
- Resistance to friction and wear
- Long-term sliding
- Forming fluidity
- Beautiful surface and gloss
It is suitable for insert molding and is widely used for automobile chassis bushings, such as:
- Steering knuckle bushings
- Various bracket bushings
- Front and back plate spring bushings
- Brake bushings
POM’s structure, featuring an oil storage pit with certain regularity, provides both the mechanical strength and rigidity of steel and excellent anti-friction properties under boundary lubrication. Other applications include:
- Door handles
- Seat belt mechanical parts
- Combination switches
- Mirrors
ABS Resins
ABS resin is a ternary copolymer of acrylonitrile, butadiene, and styrene. It can be used to make both external and internal automobile parts, such as:
- Instrument housings
- Refrigeration and heating systems
- Toolboxes
- Handrails
- Radiator grid plates
- Dashboards
- Luggage
- Miscellaneous box covers
In recent years, the increase in ABS resin usage in cars has been modest. This is due to fierce competition between ABS resin and PP resin, as well as ABS’s own drawbacks, such as poor weather resistance, discoloration, and flammability. These limitations restrict its application in main parts of cars, such as dashboards and grilles.
Polyamide (PA)
Commonly known as nylon, PA has high impact strength, friction and wear resistance, heat resistance, chemical resistance, lubricity, and dyeing properties. As a structural part of automobiles, the use of PA is continually increasing. It is especially suitable for applications in the harsh environment around the engine.
Why Are CNC Machining Services More Generally Used And Considering the Material Factors?
There are two commonly used rapid prototyping processes in the automotive industry: 3D printing and CNC machining. When considering the final production-grade materials, CNC machining services offer more advantages and are more widely used than 3D printing. The range of available materials and the primary differences are outlined below:
Additive manufacturing technology（3D printing）
Over the past few years, a variety of new rapid manufacturing technologies, collectively known as Rapid Prototyping and Manufacturing (RP&M), have emerged. These technologies include Stereolithography (SL), Selective Laser Sintering (SLS), Fused Deposition Modeling (FDM), Laminated Object Manufacturing (LOM), and Three-Dimensional Printing (3D Printing).
The advancement of these technologies has extended into many traditional fields, capturing the interest of artisans. Their expertise has enabled the use of 3D objects both directly and indirectly as patterns and models for soft tooling.
All 3D printing technologies share a common important feature: the prototype part is produced by adding materials rather than removing them. However, the performance of 3D printing materials typically only approximates that of final production materials.
| Technology | Material | Limitation | Main usage at development phase |
| SLA | Resin: photosensitive resin Beige/foggy translucent | Weak, Easy transform | Being used directly and indirectly as patterns and model for soft tooling |
| SLS | PA12 Powder | Rough, hard to do finish | Making initial prototypes and models |
| FDM | Plastic filament | Poor resolution and finish Quality, not very strong | Making initial prototypes and models |
NC MACHINING TECHNIQUE (CNC machining)
CNC (Computer Numerical Control) is the automation of machine tools through computers executing pre-programmed software that dictates their movements. The most advanced method of programming a CNC machine involves using a three-dimensional model of the part to provide the data that guides the machine in producing the part.
As CNC technology continues to evolve, this programming method is expected to become increasingly widespread.
The biggest advantage of CNC prototyping is that the materials used are very close to those used in final production.
CNC machining services in China
In the third quarter of 2018, our customers in Europe and North America sourced a significant number of prototype parts using our CNC machining services in China. We provide our customers with a wide range of quality standards that align with their project budget targets. Currently, we collaborate with the majority of major vehicle constructors. I understand our customers’ needs and, together with our team, strive to meet designers’ expectations in terms of technical specifications, quality, and innovation.
