How it’s done
To make materials replacement successful, the first step involves bringing design team members and material supplier technologists together to evaluate the overall system and opportunities for improving it.
Rather than taking a silo approach, in which each component is designed in relative isolation, designers and their material suppliers together evaluate the product in terms of function, looking for areas where plastics and/or TPEs can provide equivalent performance to traditional materials along with a host of other benefits.
When replacing metal, the first consideration is often stiffness and impact at low and high temperatures, because these two properties are likely the reason metal was chosen in the first place. When replacing elastomeric materials, the considerations are durometer (hardness) and compression set.
It’s helpful to remember that on their own, plastics are not as rigid as most metals, but can nonetheless replace metals with the addition of ribs to the design or filler to the base resin without sacrificing performance levels, leading to an optimum strength-to-weight ratio.
The next opportunity for replacement lies in conductivity for heat dissipation, as in the high-brightness LED example, as well as electromagnetic shielding (EMI/RFI). Thermally and electrically conductive polymer formulations can be tailored to specific applications, making them more cost effective than metal.
Finally, the team of designers and material technologists considers aesthetics, magnetic properties, perceived quality, and density. As an example, OEMs are now turning to plastics with a metallic filler to create engine covers that improve aesthetics and perceived quality while removing paint, associated VOCs, and cost from the process.
Again, to meet the specific targets in an application, a material supplier can customize each of these categories and can also combine them according to the application’s needs.
Using this approach offers an opportunity to significantly redesign components to utilize the polymer material to the fullest. This can involve functional integration, in which two or more components in an assembly are combined. Further, this approach can include designing for productivity improvements, whether by eliminating secondary operations, reducing wall thickness for faster cycle time, or lowering scrap rates. Finally, adding functionality is also possible with metal-to-plastics redesign.
Marc Mezailles is automotive market manager Europe for PolyOne Engineered Materials.
Kendall, we'd be very interested in 3D printing of this material, in addition to automotive uses. That sounds like my department. Can you please contact me about this?
Thanks,
Ann Thryft, Senior Technical Editor, Materials & Assembly, ann.thryft@ubm.com
Kendall. Thanks for getting back to me. I was thinking of something similar to the way fiberglass panels are made with a metal mesh replacing the glass mesh. Don't know if that is even practical or has been tried. It just seemed like an interesting idea.
Scott, not sure what sort of construct you mean specifically by a 'hybrid.' Some of our systems are filled with various substances. Metals sometimes play a role. But the metal itself doens't play a role for strength. Obviously the trade-off when systems are more highly filled is for strength properties (flex mod, impact). I think maintaining this balance is more critical for automotive applications than say electronics. We are also looking at composite-based constructs for these types of properties. Best, Kendall -
Greg, LED lighting is one area we've looked at extensively and yes, I think that conductive polymers can play a big role in heat management of the new LED systems.
I agree Kendall. The improved thermal conductivity of many polymers is now opening design doors that were previously closed for us. In addition to metal heat sinks that may have been overspecified in the past, new LED technologies burn cooler and brighter, so the opportunity to replace a metal heatsink with a thermally conductive plastic heatsink may now be available.
I found myself wondering if there were some polymer/metal hybrid materials out there for use in automotive applications? Is that a practical tradeoff for weight, strength, conductivity, etc.? Any thoughts?
Not that conductive, but sounds like a great material that can both house and supply data for low voltage sensors. I wonder if this is being explored. Also, a great way to send power or a signal through a enclosed container. That is if both conductive and non-conductive plastics can be molded together. Sound like this will revolutionize the automotive sector sometime soon.
Designing trade-offs are always more complex than getting exact matches of properties. The thermally conductive compounds referenced in the article have thermal conductivities up to about 20 W/mK. While that isn't quite equivalent to aluminum at 100W/mK, it's over 3 orders of magnitude improvement over base plastics which sit at around 0.1 W/mK.
That does make these formulations viable options for heat management. We've done several design cases in areas such as automotive lighting and have shown that those sorts of conductivities are more than enough to replace metal heat sinks which in many cases are *overspecified* for thermal conductivity.
As to 3D printing. We have 3D printing capability and development programs to be able to print some of our key functional formulations. Happy to discuss further if you like.
When demand is there, surplus is there. You can still buy car parts, new, from popular models from the 80s. They made so many of them, they are still cheap.
The low-hanging fruit of plastic-to-metal conversion is no longer there for the taking, but that doesn't mean there are no opportunities. This article does a good job of explaining how to go about finding these opportunities: design engineers should sit down with suppliers or other experts, with a focus on part function. You are probably not going to make the same exact part out of plastic that you made out of metal -- at least, not if you want the part to work! But, with a little creativity, you might be able to get the same function. It takes design ingenuity, along with a knowledge of what's out there in terms of materials. This is where suppliers and outside experts can help.
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