High-Volume Low-Cost Plastic Bushings
In this article, we are going to discuss what the best choices are for high-volume low-cost plastic bushings. When an engineer is designing a part to be manufactured, there are two approaches:
- the first is to choose an appropriate material, then select a manufacturing process compatible with the material;
- the second is to select a manufacturing process, then choose an appropriate material from the ones that are compatible with that process.
Lets try answering the question for todays article by starting with manufacturing processes for plastics.
Want more information on Polymer Bushings? Check out the following post from the popular Engineer’s choice Advanced EMC Technologies Blog:
- Selecting the Precise Polymer Bushing
- Bushings: Nylon 6, Nylon 66, and Self-lubricating Nylon
- Polymer Bushings Taking a Beating: Two Important Concepts behind the Wear and Tear
Manufacturing with Polymers
Plastics can be extruded, injection molded, thermoformed, compression molded, cast, machined the list is really quite extensive. If the goal is cost-efficiency, then we need to consider the production run. For very short production runs, machining is a good option. For longer production runs, however, casting and injection molding rise to the top. Since this article is focusing on high volume production runs, lets go with injection molding.
Polymers Appropriate for Bushings
Now that we have selected a manufacturing process, Its time to take a look at materials. Some typical Bushings materials to consider based on the type of service would include the following:
- PA (Polyamide)
- PEEK (Polyetheretherketone)
- Acetal (Polyoxymethylene)
- PPS (Polyphenylene sulfide)
- PTFE (Polytetrafluoroethylene)
Polymers that can be Injection Molded
Each one of the polymers just listed can be injection molded. However, there is another wrinkle in this problem. When these polymers are used for a bushing, they arent usually in pure form. Rather, they have fillers added in the form of solid lubricants and reinforcing fibers. If the solid lubricant particles are sufficiently small (and they normally are) and the reinforcing fibers sufficiently short (and they usually are), then injection molding still remains a viable option.
Looking at Processing Costs
So we now have a manufacturing method that seems cost efficient, and a list of materials that are compatible with it. Now we can narrow down the materials a bit more. Again thinking in terms of cost-efficiency, we can order these polymers by price, from lowest price to highest price:
Now if you look up the resin prices for these polymers, you might disagree with this list. However, resin prices dont take into account that the processing costs for some resins are higher than others.
Selecting a Polymer
Our next step is to calculate the PV for our bushing, and look at what chemicals the bushing might be exposed to, what its running temperature is, etc. With that information in hand, we can start with Nylon and work our way up the list until we find a compatible polymer.
Just because you have a high-volume need for polymer bushings doesnt mean you have to sacrifice a large part of your budget. There are several low-cost options for plastic bushings that provide excellent performance, starting with injection molded bushings.