PIM can cut costs by combining multiple steps, such as texturing and labeling, or multiple parts. “Depending on the application, when you analyze what the parts are doing and why they’re independent, you might be able to design them into a single part,” said Justus.
BASF’s Catamold catalytic debind process has three main advantages over other PIM processes, according to Justus. Its faster manufacturing cycle times increase capacity and enable either a truly continuous process or batch manufacturing. “That’s difficult to do with other, non-catalytic PIM processes because their throughput time is too long,” he said. “Catamold also gives better dimensional control and stability when centering the part. Regardless of the alloy, green parts can be machined more easily to add features that are difficult to incorporate in injection molding.”
For this PM steel alloy power takeoff clutch hub, Capstan Atlantic won the grand prize in the industrial motors/controls & hydraulics category at the Metal Powder Industries Foundation’s 2012 Design Excellence awards. The complex multi-level part, which replaced a machined design, has an ultimate tensile strength of 80,000 psi and yield strength of 90,000 psi to withstand very high torque levels in service.
Powder metal generally gives more design freedom than traditional forging and casting processes, said Franks. “We can make net shapes to help develop technologies that make vehicles weigh less, and other technologies that add to fuel economy.” Examples are variable valve timing, used in most automotive applications; advanced planetary and manual transmissions; and overriding clutches. Otherwise, those profiles and shapes would require machining.
Some shapes can be made with PM that otherwise would need intensive machining and wouldn’t be industrially feasible for reasons of cost, capabilities, and capital, said Franks. “A lot of vehicle innovation today wouldn’t be possible without PM,” he said. “We’re seeing more acceptance among both OEMs and companies that develop PM technology, across all the industries we serve.”
Although as a niche product and process aluminum PM isn’t new, GKN is seeing a growing interest, especially in automotive, for broadening its use, said Franks. In some PM-dependent product lines, saving vehicle weight is the main driver.
Especially with a PM-dependent design, a shape that can’t be made with another process, and the need to take mass out, PM aluminum is a great solution. “We’ve also been involved in materials development to increase strength, wear, or thermal conductivity.”
Thanks, Greg. So it sounds like you've found that, for your needs, PM is good for certain moderate-load, both structural and impact, designs. What I still find interesting is the fact that there are so many automotive parts made with PM with high tensile and yield strength, and that PM use is also increasing in aerospace.
Yes, for relatively moderate structural loads that are well within the strength limits of the PM material. For example, PM oil-impregnated bronze bearings work well supporting the sliding portion of a lamp mechanism on an electroless nickel plated steel rod. Designed properly, PM can successfully be applied to a wide variety of moving part designs.
Ann, I think Dave was spot on when he stated "if a part is not properly designed, it won't work, no matter how well it is made" For many of our medical and electro-mechanical parts (that do not have significant impact loads) we have great success when using an oil-impregnated sintered bronze as a low-cost bearing. Tooling and piece part costs are low and tolerances are very good (assuming a good supplier with consistent process control). However, not every design is suited for powder metal and we use a combination of design experience and historical application to guide us when to use the powder metal process.
Greg, thanks for that input from the field. Do you have any comments about the differences between PM and cast metal along the lines of what Dave said below?
For our moving mechanism designs, I really appreciate the porosity of powder metal which allows us to impregnate oils in the material matrix. This gives us a great low-cost, durable bearing with relatively good tolerances.
Dave, thanks for that observation. I think you're right--we tend to blame materials quality first, design quality second, when in fact the opposite may be true, or even both may be faulty.
@Ann: You bring up a good point -- the relationship between design and quality.
To me, "low-quality PM parts" are parts that are poorly compacted, poorly sintered, cracked prior to sintering, or made using contaminated powder. The good news is that these are all problems that can (potentially) be fixed. Process the material correctly, and the part will work.
On the other hand, if a part is not properly designed, it won't work, no matter how well it is made. For example, using a PM part in an application which involves significant impact loads is almost always a bad idea.
Sometimes the presence of a quality defect may lead you to believe that you're dealing with the first situation, when you're actually dealing with the second.
Dave, I know what you mean about low-quality PM parts. I've been on the receiving end of low-quality cast parts (and probably also low-quality PM; I find those harder to identify visually or tactually). My operating principle as a consumer is either it's the design or the materials or the combination that makes a bad part. You can also accuse QC, but QC may only be able to notice whether the duck walks and quacks like it's supposed to, not whether it breaks because it's actually a badly designed goose. That said, I was impressed at what PM can do when it's done right.
@Ann: I got my start as a process engineer in an investment casting foundry, so I have a certain bias in favor of casting and against PM. I suspect that most people tend to be biased towards materials and processes they are familiar with. I'm aware that it's a bias, and try to keep an open mind.
Unfortunately, this bias has been confirmed to some extent by bad experiences with PM parts. These bad experiences were mostly due to designs which didn't take the nature of the PM material or the limitations of the PM process into account.
Of course, you could say the same about casting, or any other process. Designers ignore the limitations of manufacturing processes at their own risk.
For 3D printing to make the jump from rapid prototyping to manufacturing, engineers will need to find easier ways to move products from their CAD screens to their printers.
Gigabit and PoE are two networking technologies moving ahead in tandem as industrial users power remote Ethernet devices such as IP security cameras at 1,000 Mbps over existing CAT5 cable.
New versions of BASF's Ecovio line are both compostable and designed for either injection molding or thermoforming. These combinations are becoming more common for the single-use bioplastics used in food service and food packaging applications, but are still not widely available.
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