Factors to Consider When Choosing the Right Material for Your Product

 

Much of the prolific growth in the plastic industry over the past several decades has been fueled by the replacement of metal products and components. Examples are numerous, and include canoes, airplane parts, medical implants, missile components, gas cans, and car parts. Along the way, many designers have had to evaluate whether to use plastic or metal in their applications. Below are some of the considerations that may be helpful.

 

PLASTIC: THE ADVANTAGES

  • Weight: Plastic can weigh appreciably less than metal, which can translate to savings in several ways. A plastic part could easily weigh one-sixth of the same part in steel or half the weight of aluminum.
  • Chemical Resistance: Plastics are much less likely to suffer chemical attack, and they will not corrode.
  • Machinability: Plastic is easier to cut through, which makes the process of machining parts quicker.
  • Dent resistant (see car bumpers).
  • Eliminates painting process: Translucent or colored parts can be produced without the secondary operation of painting needed for metal parts.
  • Design: Complex designs, shapes, lettering, and surface textures can be incorporated into the tooling made to manufacture plastic parts.
  • Quality: For high volume production, the tooling for molded plastic parts offers very repeatable quality compared to machined metal products.
  • Product Life: The life span is longer for plastics than metals in many applications.
  • Cost: The cost of raw material can be appreciably less. With a less labor intensive process, plastic molding can also save energy, labor, and production time vs. metal processes.
  • Noise: The sound of plastic against plastic is less intrusive than metal against metal.
  • Options: There are hundreds of different plastics available to meet specific applications. The choice of metals is much more limited.

 

PLASTIC: THE DISADVANTAGES

  • High heat can cause plastic to degrade.
  • Thermal expansion and shrinkage is greater than metal.
  • Ultraviolet light can degrade plastic. An ultraviolet inhibitor is often added for outdoor applications.

 

METAL: THE ADVANTAGES

  • Thermal and electrical conductivity is greater.
  • Strength: Metal is generally stronger.
  • Versatility: Metal can be used in more extreme temperature applications.

 

METAL: THE DISADVANTAGES

  • Machinability: Metal is more difficult to machine.
  • Secondary operations are more likely to be needed (i.e. polishing, deburring, painting, etc.).
  • Susceptibility to oxidation and corrosion

-Weight is a big reason parts are transitioned from metal to plastic, as they’ve been in planes and cars for many years.

Pictured are two heating trays. One is made from metal and is a standard item in home kitchens. The other is plastic, and is typical of those used in fast food restaurants, which formerly used metal.  Why the switch?  The plastic version is quieter to work with, lighter, and colors can be used to differentiate food items.

The decision of which material to use is all about the specific application. Strength requirements, number of parts needed, chemical exposure, ultraviolet exposure, and temperature are among the important considerations. It may be appropriate to look at several different metals and plastics.

For your small custom parts and fasteners, we can help you with your decision. Craftech has 50 years of experience with many dozens of different plastic resins – and we have both machining (small volume) and injection molding (large volume) capabilities.

For more information about how Craftech can help you, please visit www.craftechind.com or call us at 518-828-5001.

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