How to Replace Metal with Thermoplastics

Have you ever considered replacing your metal parts with plastic parts? It could be a viable option especially when it comes to the flexibility of manufacture, faster production cycle times, and cost-effectiveness of replacing metal parts with plastic parts.

Here are some general best practices to keep in mind regarding both design and manufacturability:

  • The best way to substitute a metal part with a thermoplastic part is to redesign the components, which should be based on the specific requirements of the end product. This usually involves working out a variety of preliminary designs for the new thermoplastic parts and then selecting and refining the best version.
  • Merely copying a metal product design, with only minor changes to accommodate thermoplastic molding manufacturability criteria, rarely delivers desired characteristics and is strongly discouraged.

The new plastic part design must also be appropriate to the specific material needs and the molding process. Here is why:

  • Detailed guidelines for the ribs, bosses, draft, holes, and other features are sometimes specific to a particular material.
  • Several general design guidelines that are important for designers of molded parts to consider are:
  1. Uniform wall thickness
  2. Number of cavities
  3. Higher production with shorter cycle times
  4. No secondary tooling operations

Below is an example illustrating the differences on a manufactured part made of metal versus plastic.

As you can see from the left side on the image above, the wall thickness differs greatly between the steel and plastic versions. The metal version having a non-uniform wall thickness also shows no fillets added at the production process. This typically could be a secondary process or a multi-stage die. However, the plastic version can be accomplished in one production process. Hence the complete design-to-manufacturing cycle can be accomplished with less cost and more flexibility.

Fiber reinforced plastics (FRP) are stronger than regular polymers plastics. This gives you additional choices on the specific application that will meet your design, manufacturability and functional criteria of the end product.

With multi cavity molds, and high-speed molding machines, cycle times are becoming faster with hot runner systems. Nowadays, 96 cavities are not uncommon at all with the secondary process eliminated altogether, reducing part cost and overheard costs for a finished product.
In summary, replacing metal with thermoplastics can lead to obvious engineering and business benefits such as:

  • More design options on specific applications
  • Designing better products
  • Reducing secondary operations
  • Cutting down on production costs
  • Gaining a competitive edge

SOLIDWORKS can increase flexibility, check design defects, and quickly update designs using the same files used in metal and plastic models. SOLIDWORKS Plastics can use the same part file for predicting the outcome of an injection molded part design. Essentially the design and plastics injection mold simulation is done in the same integrated environment. Making design changes are easy and accomplished, tracked and saved by using configurations. Configurations functionality is a unique SOLIDWORKS feature that provides the ability to alter design dimensions, type of material, visual properties and much more. Plastics injection molding design scenarios can be automatically set up and simulated to verify part manufacturability before cutting metal on a mold.

SOLIDWORKS Plastics helps predict, identify, reduce and fix manufacturability errors of plastics parts early on in the design process. Key issues such as short shorts, air traps, weld lines, gate freeze, residual stresses, volumetric shrinkage, warping, etc. can be found and addressed, saving time, money and really streamlining the communication between designers, design engineers and tooling engineers.

Jeff Osman

Jeff Osman

Jeff Osman has more than 23 years of experience in the mechanical CAD industry. As Senior Technical Sales Specialist Plastics NA, he is responsible for all technical Sales of SolidWorks products, focusing on SolidWorks Plastics, for North America and has been with SolidWorks for 19 years. Prior to joining SolidWorks, Jeff was a senior technical manager with Microcadam, a division of IBM. In addition, he has held several manufacturing positions with companies Processed Plastics, Plano Molding and Furnas/Siemens Electric.
Jeff Osman

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