When Powdered Metal Meets Plastic
A common use of sintered or powdered metal (PM) componentry is to utilize the strength and wear resistance of metals to enhance the performance of plastics. Examples include plastic levers and controls for your vehicle, wheel hubs for utility vehicles and carts, pump and seal mechanisms, gearboxes and torque applications.
Buyers for any plastics assembler or manufacturer should be familiar with the fundamentals of PM for best performance and results when utilizing mixed materials in their BOMs.
This article examines some of the most common factors you’ll want to consider when PM and plastic components are used together.
Why Plastic and Powdered Metal Are Used Together
Designs incorporating plastic-overmolded PM components and PM press-in applications to plastics are becoming more common because sintered metallurgy is growing in prevalence and end markets are driving the need for light weighting and cost reduction.
Discussions between PM components and their customers must reach an understanding of the requirements of the mating materials and the application. For instance:
- What type of plastic is being used?
- What temperature will the PM part be subject to during the over-molding process?
- What are the load requirements and are there wear points?
Common Considerations: Oil Compatibility, Temperature, and Structure
PM or sintered metal components by nature are porous. Bearings are usually impregnated with oil to improve the durability of the part and provide additional corrosion protection. Structural components may also be oiled, plated or impregnated for corrosion protection. Knowing the temperature of the application is important in assuring that the flash point of any of these additives is appropriate for the overmolding process and that the temperature will not affect the structure of the metal. Another important step is verification of compatibility between the oil and the plastic selected for the application.
During the overmold process, achieving a strong bond between the plastic and metal requires clean parts free of oils. But wait – didn’t we just say parts are oiled for durability and anti-corrosion? If oil is needed for durability and anti-corrosion, in some assembly processes, the sintered metal part is still exposed, allowing sufficient surface area so that oil can be added to it after the overmold process. Therefore, if the plastic process is incompatible with the oil, sintered metal parts can be specified as free of dirt, dust, and grease and dry to the touch. These are common specs for PM components going on to be assembled with plastic or other materials.
For push-in requirements or to prevent push-out or slippage, sintered metal components can engage with plastic with a simple metal spline, straight knurl or flange feature. Diamond knurl or recessed rings can also be machined into the part to aid in the improvement of push-out force.
Contact Atlas Pressed Metals for Your PM-Plastic Needs
In this article, we’ve covered a few of the most common factors you’ll want to consider when combining PM and plastic components, but we know there’s always more to learn! Atlas Pressed Metals has experience producing PM components for a wide variety of applications involving plastics and other materials. Our long track record of success has equipped us with the knowledge, skills and tools needed for consistent, high-quality results on every project, regardless of volume or complexity.
At Atlas, a core part of our strategy is to make understanding your requirements a top priority so we can recommend the right approach to meet your needs. Contact us for more information about PM best practices, or to get the cost-effective precision parts you need.