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Metal was once the dominant solution when selecting component materials which required strength, durability, and the ability to handle various stress loads; stresses such as impact, shear, tensile, and warp. With modern technological advancements in finite element analysis (FEA), composite materials engineering, and precision injection molding processes, the conversion of parts and components from metal to plastic has become a viable, economical, and popular solution.

Not only does the use of plastic reduce part weight and manufacturing costs, it also increases design flexibility with fewer manufacturing operations. Utilizing a scientific approach to creating plastic parts that rival their metal counterparts can result in components that are equal in structural integrity, with the added benefits of resistance to chemical corrosion, as well as electromagnetic (EM) and radio frequency (RF) shielding.

The automotive and aerospace industries have led the charge toward replacing metal parts with plastic parts, for the sake of decreasing vehicle weight and increasing fuel efficiency. In a recent article published by the American Society of Mechanical Engineers (ASME), it was stated:

Plastic parts can actually be stronger than metal parts by using engineering-grade materials with proper structural design. The ability to mold in features for structural strength such as ribs, bosses, and gussets when the part is originally produced (instead of fastening, welding, and gluing afterwards) can increase the total strength of the assembled part, as well as reduce additional costs.

Through the use of FEA engineering software and Mold Flow testing, a preliminary confirmation of the proper polymer material and molding efficacy can be obtained. Additional stress loading simulations conducted by mechanical engineering professionals can offer customers peace of mind, knowing that their part conversions are supported by scientific, objective, and real-time data.

Consider these three factors that convincingly support the conversion of metal parts to plastic:

Lighter Weight

Consider that the specific gravity (the ratio of the density or mass of two substances) of aluminum, which is often used for its commendable weight to strength ratio, can range between 2.5 and 2.8 SG. In comparison, one of the denser plastics, polycarbonate, has a gravity range of 1.2 to 1.4 SG. Metal to plastic part conversion is highly successful at reducing component weight, which directly reduces shipping costs, and will also reduce manufacturing and tooling costs. Metal part manufacturing has always required robust machines, numerous operation cycles, and skilled tradesmen. A comparable plastic part can be produced in a single injection molding process that can be completed within one minute.

Multiple Part Merger

Injection molding is able to produce complex geometries, which include bosses, ribs, holes, threads, undercuts, and ports-all with tight tolerance. With the creation of one engineered precision mold and a high-speed production process, multi-faceted plastic parts can be manufactured efficiently. While die-cast parts are considered the metallic equivalent to plastic injection molded parts, consider these potential material additives that make plastic parts a far better solution:

  • Lubricants: Improved wear and reduced friction
  • Carbon or Stainless Steel: Improve conductivity and EMI/RFI shielding
  • Minerals: Electrical properties, dimensional stability, and impact resistance
  • Modifiers: Increased toughness
  • UV Protection: For stability in outdoor environments
  • Colorants: Limitless color options
  • Strength Modifiers: Glass, Tungsten, Kevlar, Copper

Reduced Cost

Using engineering grade resins, such as nylon or ABS, thicker and heavier die-cast metal parts can be replaced with a plastic part that is stronger and has a thinner and more uniform wall thickness. And less material equals reduced material costs. Through the elimination of multiple machining operations (such as threading, welding and surface finishing), high-speed, single-process production cycles can eliminate 25% to 50% of the manufacturing cost compared to metal parts. There exists a wide range of high-performance polymer blends and hybrids that can be engineered to meet specific performance requirements, and many will offer an affordable alternative to the use of metals and alloys.

Start the process by consulting with an experienced precision injection molding facility to determine the economic feasibility of converting your metal parts to plastic. With an engineering review, the current material and functional requirements of your project can be ascertained to ensure part-to-part consistency and the highest possible quality throughout the life of the project.