Analytical Software Finds the Weakest Point
Piper Plastics uses proprietary FEA structural analysis to solve the mystery of why parts break.
Injection molder and plastic component design firm Piper Plastics, Chandler, Ariz., is all about challenging the status quo. “Everything we do here is based on science and engineering,” says Dave Wilkinson, materials engineering manager at Piper Plastics. “We take the tightest requirement of any customer and drive it throughout the entire business. We try to take away art, and make it as much as possible about the science.”
Piper Plastics offers services in engineering design, polymer development, and processing. Earlier this year, the company was acquired by Quadrant Engineering Plastic Products, a subsidiary of Swiss-based Quadrant AG, which has similar product lines (U.S. office in Reading, Pa.). Randy White, president and CEO of Piper Plastics, says the acquisition will help give Piper more of a global reach, as Quadrant (quadrantplastics.com) has facilities located all around the world.
At its Chandler facility, Piper employs a variety of plastics fabrication methods, including a proprietary injection molding process it developed for very thick, net-shape parts. Piper also launched a line of injection-moldable thermoplastic composite materials called Kyron Max that allow parts to be processed in high volumes with strengths that approach lay-up composites and metals. Target markets include aerospace, automotive, industrial, oil and gas, and medical.
In addition, Piper has developed advanced analytical software packages to predict the mechanical performance of its molded parts based on the polymer matrix, processing technology, stress loads, and environmental conditions. “Our employment of polymer scientists and structural and mechanical engineers enables Piper to be the ‘plastic expert’ for our customers, and we are involved in thousands of metal-to-plastic conversion programs,” Wilkinson says.
Piper conducts lots of testing of metal-to-plastics applications for industries from aerospace to sports and recreation. Companies come to Piper Plastics to help conduct R&D on polymers and processing.
Relying on analytical software, Piper is able to run multiple analyses on a part that shows the customer how it will mold as well as provide structure analysis of non-uniform (anisotropic) properties due to fiber orientation. The company also evaluates part stress in the intended use and the effects of that stress on various polymers. Based on the software packages the company has developed, it can examine the actual strength of the part. “We are one of the few people that can do that and do it accurately, instead of relying on a data sheet,” Wilkinson says.
While engineers working with metals often can use data sheets with confidence, it’s not the same with plastics, especially when filled and reinforced. Wilkinson says this is because when a data sheet is developed, it is based on a molded test specimen that may not reflect the molecular or fiber orientation in critical areas of an actual part. As a result, the part can fail. And here is where analytical software and engineering comes in to solve the mystery of the broken part.
White says Piper gets a majority of its customers through resin suppliers. “Companies will use a particular polymer and once it breaks, they will go to the resin company and ask, ‘I thought this material was supposed to be much stronger than that. Why is my part breaking?’ The resin suppliers send the customers to Piper to help change the design to eliminate breakage.”
Wilkinson adds, “We have expensive software and experienced engineers that can actually predict the strength of a part.
“So, for example, we can tell a customer that in a localized section of their part, they’re going to lose 80% of mechanical properties due to flaws in the polymer matrix inherently caused by injection molding, and we can do a finite-element analysis (FEA) of the part based on that prediction.”
White points out that while it’s important to know how strong a part will be early in the development cycle, sometimes it is even more valuable to know how weak it is—and where. “We tell the customer where the weakest point of design is, the weakest link, and that is valuable for companies who don’t want a part to break,” White says. “For instance, with aerospace, or even competitive bike racing, you’re dealing with people’s lives. It’s important to everyone to know the weakest part of their design and what they can do to make the weakest part as strong as the average.
“In most cases, after we make the customer aware of the problem, they request that we eliminate the issue using our process technologies,” he says. “It is a great service to our customers to have the ability to identify the issue, but we also developed advanced technologies to eliminate or minimize the problem.”
White cautions that companies that are looking for the cheapest price shouldn’t ring his doorbell. He says starting with the right polymer in the first place and then modifying the design will save a company so much more money than going with the lowest bid.
“A lot of times they don’t believe us, so we say, ‘Lend us your mold free of charge and we’ll show you how strong we can make the part.’ And then, hopefully, we will work with them on designing the next generation of the part to be molded with our machines.” White adds, “The most important thing is that we test everything and there’s a lot of engineering going on before we even process a part.”
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