Going Plastic: Considering the Move From Metal to Plastic Components

Published on February 6, 2024

Certain manufacturers have disingenuous opinions regarding plastic components. Some may worry plastic is a weaker material or erroneously believe there will be challenges regarding design, while others are merely resistant to change and want to continue making products using material with which they’re familiar. However, the metal-to-plastic conversion process can offer many benefits to product manufacturers due to certain unique qualities that plastics bring. Often, the properties can match or exceed those of the material currently used for a company’s products. A manufacturer should carefully weigh the advantages and disadvantages to determine whether a metal-to-plastic conversion makes sense.

How Metal-to-Plastic Conversion Benefits Production

Plastic parts have been around since the late 19th century when plastic injection molding was first developed. World War 2 saw their use expand dramatically, with a massive and urgent demand for mass-produced items that were both dependable and economical. Generally, plastic components are half the weight of analogous metal components, while they can also be made smaller and with thinner walls. This often offers an advantage for aerospace, automotive, or other applications where lighter weights offer better performance.

When tolerating tension, plastics are equally as reliable as many metals. Manufacturers looking at metal-to-plastic conversions for their products can even find plastics with a tensile strength greater than metal ones. With injected molded components, there’s also no need for welding, which eliminates the structural weakening that often occurs around welds. Unlike most metals, plastics don’t require coatings to protect them, making them better at enduring corrosion, heat, impacts, and other conditions components might face.  

For manufacturers mulling a metal-to-plastic conversion, the benefits of plastics include the following: 

  • Cost of manufacturing is usually lower
  • Design flexibility for plastic parts is better
  • Fabrication of plastic parts generally results in less scrap
  • High tensile strength when parts are properly designed
  • Highly repeatable processes make them ideal for mass production
  • Lower component weights make them a better choice for many applications
  • Shipping costs tend to be lower because of their lesser weight
  • Tooling used to deburr or otherwise shape components last longer as they require less machining

Engineers working with plastic producers continue to innovate to solve issues surrounding metal-to-plastic conversions. Plastic resins and composites are being developed to improve aesthetics, make more complex designs, withstand inhospitable conditions, offer better structural dynamics, resolve weight limitations, and provide solutions to material issues for various products. Plastic injection molding already produces many components that were previously made from metals.

Design Improvements

Parts designers and mechanical engineers like the freedom metal-to-plastic conversions give them. Often, converting metal components to plastic will allow them to add design features that would be otherwise prohibitively expensive and difficult to make with metals or alloys. Using cutting-edge technology and the latest software, injection molding companies can test out various types of plastic during the design stage of product development.

This allows manufacturers to make parts with more complex geometries, sometimes even allowing them to consolidate multiple components into one. With the reduced weight that results from metal-to-plastic switching parts, conversion can produce components with fewer structural limits. Add to this the ability to easily make parts in various colors, and it’s no wonder many manufacturers are switching to plastic.

Quicker Manufacturing with Better Repeatability & Easier Changeovers

There are many ways to manufacture components from metal. Plastic conversions of parts previously made from metals often result from the manufacturer realizing the faster rate at which plastic injection molding can produce components. Utilizing a single mold design, the process can also produce more uniform parts. Additionally, the plastic injection molding process allows manufacturers to combine components without welding to make them seamless, often eliminating the need for additional assembly.

Unlike metal parts, which normally require a finishing process, plastic components need no coating or painting to protect them, reducing production costs. The need to maintain tooling is also decreased, as though the cost of tooling is essentially the same; tools wear more quickly when compared with metal or plastic. Conversion from metal to plastic parts can result in tooling that lasts, on average, ten times longer. While plastic parts don’t require any type of coating, polymers can be made with additional protective properties by mixing certain ingredients into the molten plastic.

Plastic parts are also made with readily repeatable processes and fewer steps. Though there are automated means to produce parts from metal, such as CNC (computer numerical control) machining, these tend to be highly expensive when comparing part fabrication of metal to plastic. Conversions that involve plastic injection molding offer highly automated processes with high throughputs that require little supervision.

In addition to all this, it’s easier to change materials with metal-to-plastic conversion. For example, altering a component from aluminum to stainless steel would require a complete product redesign or at least the part. Regardless of their ingredients, plastic resins offer greater flexibility regarding material changes, whether done to improve quality or reduce cost.

Reducing Production Costs & Time to Market

Perhaps the most common reason for a metal-to-plastic conversion of parts involves the cost of materials. There are a few reasons why this is so.

Reasons why material costs are often less for plastic parts than for metal include: 

  • Energy: The lower temperatures needed to melt plastics than metals means less energy is required, while the reduced need for machining also means injected molded parts require less energy to fabricate.  
  • Price stability: The price of metals tends to fluctuate, sometimes wildly, as economic downturns, tariffs, and other events cause insecurity in the markets; in contrast, the price of plastics and resins used for injection molding remains much more stable.
  • Shipping expenses: Plastic parts weigh less, so cost less to ship than metal ones; additionally, it’s easier to design certain plastic components to stack closely together or nest within each other to optimize space during transport.
  • Waste: Metal component fabrication produces more scrap than the plastic injection molding process.

Overall, metal-to-plastic conversion of parts within a product will lessen production costs, raising profit margins while also often augmenting performance.

Augmenting Performance

The performance of a product can be enhanced with a metal-to-plastic conversion of components. Generally about half the weight of metal, plastic parts can also be made smaller, with reduced wall thicknesses. Making components lighter, smaller, and thinner makes them easier to use in a wide variety of applications, including aerospace, automotive, and medical device industries, along with other applications where critical or complex components require tight tolerances.    

Many modern plastics can withstand significant stress, making them as reliable as their metal counterparts. While just as robust as those made of metal, plastic conversion of a product’s components also enables them to withstand harsh conditions. Modern hybrid plastic formulations result from blending resins, which are used to achieve specific performance needs. With metal-to-plastic conversion, components that better absorb impacts, resist heat, withstand corrosion, and offer other valuable properties can be made.

Metal to Plastic: Conversion Comparisons for Components

Not every part should be made from plastic, just like not every part should be made from metals or alloys. Both metals and plastic resins have their various strengths and weaknesses. For this reason, the properties of any material used for a vital component should be carefully considered by manufacturers looking at metal-to-plastic conversions for parts in their products.

Benefits of metal components include: 

  • Heat resistant:  Though modern resins like polybenzimidazole (PBI) can withstand temperatures of over 500°C (932°F) for short periods, stainless steels are capable of enduring temperatures between 1400°C to 1530°C (2552 °F to 2786 °F) before melting.
  • Stronger: While metal alloys are generally tougher than plastics, new plastic polymers like 2DPA-1 are even stronger than many steels.

Drawbacks of metal components include: 

  • Design limitations: Making components with complex geometries is difficult, requiring more costly processes.
  • Higher processing costs: Tooling required to work with metals is often more expensive than those used for plastics due to increased wear.
  • Post-fabrication: Often metal components require more work after fabrication, such as surface finishes or a deburring process to ensure there are no sharp edges that can interfere with a product’s operation.

Advantages of using plastic parts include: 

  • Chemical resistance: For parts that need to tolerate exposure to chemicals, or even water, plastics offer greater durability and won’t oxidize or rust.
  • Design choices: With it’s lower melting point, plastic can be formed into myriad shapes easily so offers many more design choices, especially when using injection molding techniques.
  • Faster production: This is particularly true for plastic injection molding of parts, which can mass-produce significantly more plastic parts than with metal.

Difficulties with using plastic parts include: 

  • Durability: Though specific types of plastic will last longer, depending upon their application and properties, metal parts will generally outlast those made from plastic.
  • Post-fabrication: While metal parts commonly require work after fabrication, certain types of plastics require deburring too.
  • Weaker: Though certain newly developed plastics can be made stronger than many metals, plastic parts largely aren’t as strong as their metal counterparts.

With all these considerations, manufacturers can decide for themselves whether metal to plastic conversion of components is a good choice for their specific application.

How Spaulding Can Help with Metal-to-Plastic Conversions

Spaulding Composites, Inc. partners with manufacturers to mass-produce high-quality components. With comprehensive knowledge of various materials and processes, our material experts can assist with determining the best material for your application. Meanwhile, our mechanical engineers can also help optimize part designs for the injection molding process. To learn more about our capabilities, contact the plastic experts at Spaulding Composites.