The Places Where Plastic Has Replaced Steel

By Benedette Cuffari, M.Sc.Oct 3 2018

ImageCredit:Shutterstock/Pixachi

When considering most industrial applications, it is often both extremely time- and cost-consuming to construct multiple different metal parts that are needed to make up a single large material or machine component. Since the early 1950s when the first application of metal-to-plastic conversions occurred, manufacturers have continued to embrace the numerous advantages associated with utilizing engineering-grade resins rather than metals for their industrial needs.

By 1979, following a period of intense scientific research that focused on the potential manipulation of plastic components, plastic manufacturers determined that the incorporation of elongated glass fibers could significantly improve the strength of plastics to make it more competitive with metal¹. Furthermore, the introduction of thermoplastics and other advanced plastic materials continued to support this revolution of replacing metal components with plastic for a wide variety of industrial purposes.

Benefits of Replacing Metal with Plastic

There are numerous benefits, both direct and indirect, that are associated with utilizing plastic material rather than metals in a wide variety of different industries.

Cost Efficiency

In regard to the cost efficiency associated with replacing metals with plastics, the American Society of Mechanical Engineers in September 2013 stated that companies can achieve overall cost savings of up to 50% by converting metal materials to plastic parts¹. These significant cost savings can be achieved through numerous ways, some of which include:

• Injection-molded plastic parts can eliminate the need for metal fasteners and assembly.
  • Injection molding processes also exhibit more rapid cycle times as compared to metal processing techniques.
  • This technique also eliminates the need for secondary machining procedures to be performed.
• Colors can be directly incorporated into the plastic melt, thereby eliminating the need for subsequent painting or laser marking procedures to be performed
• Eliminates the need to weld, grind, add dents/scratch resistance aspects and/or noise dampening to the material².
• Plastics significantly reduce the weight of materials as compared to when metals are used, thereby reducing shipping costs and improving the end-user’s physical ease when utilizing the product.

Improved Strength

When engineering-grade plastics are being used, these materials can exhibit a material strength that actually exceeds that of metal parts. Some of the strongest plastic materials that have been investigated for their potential application in automobiles are thermoplastic composites that have been found to be just as strong as both steel and aluminum while significantly reducing the weight of applied products. To achieve these exceptional strength properties, various different plastic composite formulations can be used, of which include:

• Short Glass Fiber-Reinforced Plastic
  • Improved strength, stiffness and heat detection properties
  • Preferred material for cylinder heads and cooling components used in vehicle engines
• Long Glass Fiber-Reinforced Plastic
  • Improve the high-performance and lightweight properties of vehicles
  • More expensive as compared to other plastic materials³
  • Reduces costs as a result of its lower specific gravity
• Carbon Fiber-Reinforced Plastic
  • Reduces the weight of large vehicle parts (e.g., side panels)

Ease of Fabrication

Both metal and plastic materials require a series of fabrication methods to cut, shape or form the material prior to their incorporation into any product. The type of plastic materials being used plays an important role in determining the type of plastic fabrication method that will subsequently be performed; however, plastic materials offer significant advantages as compared to metals when considering the manufacturing process.

For example, the particularly low melting point and high malleability of plastic allows these materials to be easily formed into a wide variety of complex shapes; thereby contributing the ease of forming this material without requiring the use of any forming or machining procedures. Furthermore, plastic materials also typically exhibit a greater chemical resistance as compared to metals against potentially hazardous chemicals, such as those that cause oxidation or rusting when applied to metals⁴. Despite these advantages, plastic materials are not as heat resistant as metals, which can be concerning for industries that require their equipment and other products to be exposed to extremely high heat levels. Overall, plastic materials can be produced at a much faster rate as compared to their metal counterparts at a lower cost.

Conclusion

With this information in mind, it is clear why so many different industries have made the transition from metal to plastic. One of the most notable examples of an industry that has actively participated in this material replacement is the automotive industry. Some ways in which automobile manufacturers have replaced metal with plastic materials include:

• Exterior vehicle parts
  • Front-end modules
  • Beams
  • Brackets
  • Trunk lids
  • Deck lids
  • Body panels
  • Floor panels
• Air-bag containers
• Pedals
• Seat components
• Air ducts
• Resonators
• Chain Tensioners
• Belt pulleys
• Oil pans
• Sumps
• Cylinder head covers
• Gear components⁵

The aerospace industry has also actively looked to replacing their metal aircraft components with high-performance plastic materials. The lightweight nature of plastics combined with their tough and impact resistant properties are ideal for the needs of this industry. Some ways in which aerospace manufacturers have replaced metal with plastic materials include:

• Cabin interiors
• Back-lit panels
• Protective insulation components
  • Heat shrinking features
  • Vibration-resistant wires and cables
• Valve components
• Composite tooling
• Fasteners
• Gears
• Gear spaces
• Wear pads
• Wire wrap insulation⁶

References

1. “Replacing Metal with Plastic” – MachineDesign
2. “Change-up Pitch: From Metal to Plastic” – Advanced Manufacturing
3. “Plastics Strong Enough to Replace Steel in Automotive” – Kaysun Injection Molding & Engineering Solutions
4. “Plastic Vs. Metal Fabrication – Advantages and Disadvantages” – Thomas Publishing Company
5. “Plastics outperform metal in automotive applications” – ICIS
6. “Aerospace” – Curbell Plastics

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