Considerations of Replacing Metal with Plastic

Metal replacement is a very straightforward process which is not dissimilar to traditional design engineering. The key difference is understanding the material performance tradeoffs in switching to a plastic material, and how those tradeoffs affect the geometry of the design.

Too often we try to "replace" metal with plastic, and that approach is a source of many problems. Each material can do what the other can't, in addition to the characteristics they share. The real question is, "What function(s) is the part intended to perform?" Because plastic can often be processed to net, or near-net, shape and because it can often combine shapes of several metal parts into one, the design of the part depends on the job to be done, the process to be used in producing the part, and in what environment will the part be used. Sometimes direct replacement is valid, but often it is not, or the product can be made better or more inexpensively by using a functional design review, either formal or informal.

There is some information (at least material data) on internet. I also have a metal replacement "roadmap" that I can share to help you understand the process if you would like it.

The process consists of the following steps, but the detail may vary depending on how formal you want to be about the project:

• Establish the cost incentive using quotes or cost estimation tools.
• Understand everything about the function of the "target" component to be replaced.
• Develop thermoplastic concepts which reflect the required functions, including environmental considerations, temperature, structure, etc.
• Validate the preliminary concept using simulation tools.
• Validate the cost incentive - make sure the project is a net cost save given the geometry, material, and annual volume (i.e. tooling amortization).
• Finalize design.
• Prototype.
• Validate with testing.

Again, it is critical to ensure that the design and validation tasks are done with an in-depth knowledge of how the material and geometry (design) will function in the application. Remember, you are dealing with materials that have only < 10% of the stiffness of steel, with significantly reduced strengths as well.

Finally, you must incorporate design features which are appropriate for the target thermoplastic process while developing the new design.