Society of Plastics Engineers
Plastics Engineering
April 2011

Strong and Flexible Implants

In the late 1990s, polyetheretherketone (PEEK) was first used for implants. PEEK-based spinal spacers were used to hold vertebrae upright after disk removal. Unlike titanium, PEEK parts didn’t eventually subside into bone, and they allowed visualization of the bone surrounding the implant in X-ray or CT images.

These advantages and others have led to many more PEEK-based implants. Marcus Jarman-Smith is a technology leader at Invibio Ltd., which has been making PEEK-Optima^R polymer for over a decade. He says that in addition to spinal implants, the material holds clear benefits for knee-replacement and hip-replacement parts. PEEK parts don’t produce the health concerns associated with the metal against metal wearing of traditional hip replacements. The strength of Invibio’s bearing grade, Motis^R, means it can be used alone to make hip-replacement cups instead of combining a metal cup with a polymer liner. The resulting thinner cup requires the removal of less bone. In addition, polymer parts flex and pass on stress to the bone rather than focusing the stress on the implant. This transfer of stress helps bone maintain strength and means that damage is less likely to occur.

“Because of the polymer’s high strength and bearing properties, it is starting to be looked at more for trauma applications,” says Jarman-Smith. He says that PEEK has a high strength-to-weight ratio and allows more flexing than metal plates and nails used to repair a broken arm or leg. If the patient is a child, or if the patient develops an infection, plates or nails may have to be need removed, which is difficult with metal because it tends to bind to the bone, whereas PEEK doesn’t. The Quantum^TM Humeral Composite Nailing System from N.M.B. Medical Applications Ltd. was the first PEEK intramedullary nail to gain FDA approval (March 2010). The nail is made of Invibio’s Endolign^R, a composite of continuous carbon fibers in a PEEK-Optima polymer matrix.

For future developments and applications, the company is considering options such as combining PEEK with additives that help it bind better with bone or encourage bone growth. “We also want to see if we can use it to make scaffolds or porous PEEK parts that can support tissue and allow tissue to grow inside and regenerate,” says Jarman-Smith.

Although PEEK has many advantages for medical implants, it can be difficult to mold in a clean-room environment because of its high melt temperature. PMC SmartSolutions^TM has been implementing new ways to handle this challenge. The company, founded in 1929, entered the medical molding market four years ago. It specifically focused on long-term surgical implants made of materials such as PEEK because of the potential growth in this market.

“Consistency is very important for implants,” says Lisa G. Jennings, president of PMC SmartSolutions^TM. Using heat-transfer oils for mold-temperature control can potentially cause product contamination. Electric cartridge heaters are subject to temperature problems that can affect product consistency because they cannot control the mold’s surface temperature in a tight window across a part and often have hot and cold spots along their length. Cartridge heaters are also unable to remove heat from the mold if it becomes too hot.

Thus, PMC examined using pressurized water for precise mold-temperature control. Pressurized water can be heated to temperatures as high as 400°F. The company partnered with Single Temperature Controls of Charlotte, North Carolina, USA, which sells temperature-equilibrium systems that pump water through the mold at a set temperature. Heat is transferred to the mold if the water is hotter than the mold and removed from the mold if the opposite is true.

In PMC’s experiments, it found a 44.2°F variance in mold temperature with electric heating and only 5.0°F variance with the water-heated system. The effects from this variance could be seen through a 0.003-inch increase in part shrinkage and average 18.5% reduction in relative crystallinity in the same parts produced using the electric-heated molds.

The pressurized water system has allowed the company to make complex parts of PEEK and other high-melt temperature plastics. For example, it has made insert-molded porous metal parts for orthopedic implants. “We were among the first to use high-pressure water to control mold temperature for making medical-device implants in a clean room,” Jennings says. Since PMC shared its data showing the benefits of using water to control mold temperatures, other companies have followed its lead in using this technology. The complete white paper is available on www.pmcsmartsolutions.com.

By Frank Esposito | PLASTICS NEWS STAFF

WESTLAKE, OHIO (April 20, 1:40 p.m. ET) — The medical device market can be a rewarding one for plastics processors, but it’s not a market you can wander into and hope to succeed.

The volume of requests for medical projects is growing at Parker Hannifin Corp., a Cleveland-based manufacturing giant that uses engineering resins, fluoropolymers and urethanes in its seal products. But Dale Ashby — vice president of technology and innovation for the firm’s sealing and shielding group — said that those increased requests bring with them a lot of work in material selection, as well as part production.

“The main question that every customer has is : ‘How long can I expect this product to last in my application?’ “ Ashby said at the Plastics in Medical Devices conference, held April 12-14 in Westlake.

“We need well-defined expectations of performance from our customers to make predictions on seal life,” he added. “Modeling is very important. It’s step No. 1 in proving useful life. Tools and modeling continue to improve, and OEMs have more knowledge than ever before.”

Parker, a supplier to many major OEMs, rang up sales of more than $10 billion in 2009. The firm employs 62,000 at almost 300 plants worldwide.

Parker made a big move in the medical field in 2008, when it created a new medical systems division in its seals group. The new division was based on six businesses — five in California and one in Indiana — that Parker had acquired from HTR Holding Corp. Those businesses make plastic and elastomeric components for medical devices such as intravenous equipment, drug-infusion pumps, respirator hoses and catheters sold directly to OEMs. The group performs injection molding, rapid prototyping and similar services.

Ashby said that in material selection, it’s important for processors to consider physical properties such as elasticity and lubricity, and mechanical properties such as flex resistance and toughness. In thermal properties, processors need to be aware of melt flow index and thermal conductivity; while in electrical properties, surface resistivity and arc resistance can impact material choice. Chemical resistance to solvents and cleaning solutions also plays a role.

Injection molder PMC LLC of Cincinnati is among the ranks of firms that successfully have entered the medical field in recent years. But even for PMC, doing so took a pretty big leap of faith, according to President Lisa Jennings.

“We bought the equipment for medical molding, had a clean room ready and did sample molding before we even had a customer,” she said at the event. “But based on our evaluation of what PMC is capable of — making millions of parts at 0 PPM quality levels — we determined that medical was a good niche for us.

“We had best-in-practice standards that weren’t available to most of the medical device group.”

PMC also “had to develop a medical culture” that was different from automotive and other markets it had participated in over the course of its 81-year history.

“We needed to consider all areas of our business and manufacturing systems,” said Jennings, who is also a fourth-generation owner of the firm. “For clean-room classification, we had to create an environment to insure that implant molding is controlled and consistent.”

“We learned that having the right processing equipment is the foundation for repeatable processing of implantable polymers. We also learned that customer validations are custom and are up to interpretation.”

PMC — which operates plants in Indiana, Mexico and Germany — now produces medical items used in orthopedics, sports medicine, spinal care, cardiovascular care and drug delivery. PMC’s medical products are based on polyetheretherketone (PEEK), thermoplastic polyurethances and ultra-high-end bioabsorbable and bioresorbable resins, which are used in implants and other devices.

“Some of these materials can cost from $125 a pound to thousands of dollars per pound, so there can’t be any material wasted,” Jennings said. “That’s a huge consideration.”

PMC Medical is pleased to announce the development of unique technologies and services for Orthopedic, Spine, Cardio and other implantable and high-temperature polymer-based medical devices.

PMC Optimized Thermal Management System (OTMS)
PMC Medical’s latest technology innovation is the PMC Optimized Thermal Management System. PMC OTMS offers more uniform heat control, providing shorter processing times and a more consistent processing window, while delivering better control of the crystalline structure. PMC is conducting injection molding process improvement studies with the PMC OTMS system, for implantable and technical grades of PEEK (Polyetheretherketone, Polyaryletherketone), PPSU (Polyphenylsulfone, Radel®), PSU (Polysulfone, Udel®), PEI (Polyetherimide, Ultem®), and other high temperature materials.

The objective of PMC OTMS is to optimize thermal control in the molding process, to improve the physical properties and cost drivers of the molded components. PMC OTMS is being developed with input from our customers and our material suppliers. The primary benefits for biomaterial and high-temperature polymer-based medical devices can include:

• Cost reduction – reduction in material usage and cycle time
• Tighter as-molded tolerances
• More consistent structural properties
• Part-to-part consistency and reliability
• Greater design flexibility
• Improved machining characteristics

Upcoming studies will include process optimization for bioresorbable materials, implantable elastomeric polycarbonate materials, and other new biomaterials.

PMC Biomaterial Sampling Tools
PMC Medical is offering medical device customers a sampling tool incorporating PMC OTMS technology. Sampling services offer medical device customers the opportunity for:

• Biomaterial and high-temperature material studies and testing
• Basic injection-molded shapes for machining into devices and trial parts

Sampling tool sizes available include:

• 1” x 5” x 0.100”
• 1” x 5” x 0.200”

PMC can provide additional geometries upon request, catering to unique device needs.

For more information, please contact Phil Cashen at 630-650-0343 or [email protected].

PMC Medical is an innovator of biomaterial and high-temperature thermoplastic material processing and tooling technologies for the medical device industry. PMC’s unique offering provides customers with a trusted source for specialty materials expertise, while providing a complete range of services through packaging and sterilization management. An ISO 13485:2003 certified contract manufacturer with 80-years of experience, PMC’s services include design for manufacturability, prototyping and sampling, hyper-precision injection molding, assembly, packaging, and sterilization management. PMC Medical is based in Cincinnati, Ohio, with facilities in Indiana, Mexico and Germany.
www.pmcsmartsolutions.com

Plastics Machinery Magazine
Issue: May 2015
By Angie DeRosa

Lean manufacturing practices are ingrained at the Shelbyville, Ind., injection molding facility of PMC SMART Solutions LLC, where insert molding, two-shot molding and overmolding are performed. The company is world-renowned for its deft skill in molding high-temperature, highly engineered resins such as PEEK and polyphenylene sulfide (PPS). Other biomaterials that it works with include bioresorbables and polysulfone. The components being molded are not for the faint of heart.

Here, dedicated presses have been configured scientifically to produce safety-critical parts for Tier 1 automotive suppliers in one section of the facility. In another, a Class 8 clean room is home to all-electric presses that mold components that go directly from PMC’s facility to the operating room. The parts being molded can go directly into the human body. This site is certified under ISO 13485 and is FDA registered to produce finished medical devices.

“SMART” is part of the company’s name for a reason. It is an acronym for Scientific Manufacturing Assures Reliable Throughput. In its fourth generation of ownership, the company was started in 1929 by the Gerdes family. It was recently certified women-owned.

PMC President Lisa (Gerdes) Jennings leads the tour along with Vern Nightenhelser, director of manufacturing operations. Jennings explains how scientific molding and a culture of extremely high quality give customers the confidence to entrust their most critical products to PMC.

“We are making brake parts every day. If a brake goes bad, somebody could die. The culture and mentality is just within us,” she says of the stringent practices that must be followed. “Our parts get put into other things, and tested and cycled. We’re the last hands before they go into one of our family member’s surgeries.”

PMC’s quality systems and performance “help our customers feel safe with us delivering their babies,” she says. “They are ultimately responsible for these parts going into the operating room.”

PMC is based in Cincinnati where it began operations in 1929. On the day of the tour, Jennings just had been notified that her firm has won two awards from customers — one on a global scale and the other for the NAFTA region.

“So I can say that we’re getting two awards. I just can’t be specific right now,” she said.

STANDARDIZING FOR SIMPLICITY

The awards are the ultimate feather in the cap for very strategic and purposeful manufacturing practices that incorporate lean into every part of the operation. Lean is communicated throughout the operation through tangible results, for example, achieving less than one-half percent scrap rates. That includes start-up and shut-down. There also is the 99.7 percent on-time delivery. Unplanned down time due to maintenance failures is less than 1 percent.

The auxiliary equipment that supports clean room molding is located outside the clean room.
“You continuously have to drive waste out of processes,” says Nightenhelser, who has been with PMC for 33 years. “You have to do that to remain competitive and you have to do it internally. You can’t wait for your customer to tell you that. You have to do it yourself. And that is how you’re always looking for a little better way to make what you buy into what you sell instead of recycling it into the scrap bin or the dumpster. You’re forced to do that because of the cost of your materials.”

Jennings refers to it as managing to the pellet.

“Whether it’s $1,000-per-pound material for implants or $3-per-pound material for something else, we treat it all the same. All of it matters,” she says.

This is where the primary machinery and other equipment play a critical role. In PMC’s world, molded parts are extremely complex. Some of these components have to be molded to tolerances as low as 15 to 20 microns. To reduce the complexity in other areas of the operation, officials have standardized the equipment. In this way, they also have fewer spare parts to store.

“We’ve done our homework on why we’re doing it and what we need,” says Nightenhelser. “It’s based on what you’re getting from the customer and then we go in and rightsize the equipment to make sure it’s best utilized for that (project) and we couple that with volumes. So I wouldn’t go to Lisa and say that I need this press for 100 pieces a year.”

Instead, they seek volume. Think a half million, 1 million, 2 million parts per year. Then they can rightsize the primary equipment or the automation and that makes it easier to get a return on investment.

“You do not want a little bitty mold in a great big press,” he says. “We did a lot of work years ago on the equipment as far as, we’re going to go to Milacron Roboshot, here is why. We’re going to use a Matsui dryer, here’s why. We haven’t deviated from that and that creates familiarity amongst the troops.”

The Roboshots are standardized, all-electric, closed-loop, so they support PMC’s scientific manufacturing and scientific molding.

“We dial in the process and the press is tied into the robot and it will reject a part automatically,” Jennings says. “If it rejects a part three times, it shuts down automatically. We use the press’s features to manage our scientific injection molding.”

From a parts standpoint, the technology has evolved within that press so that it can be done in a closed loop. When the process of standardization began, PMC took into consideration the technical capabilities of the pieces of equipment, all of the advantages and disadvantages, says Jennings.

“We took into account, just like on the vertical presses, all-electric versus hybrid. There are a lot of people who use hybrids in the clean room. We just said, ‘It’s not for us,’” she says.

Two all-electric vertical Nissei presses round out the clean room molding capabilities. In the automotive facility, a 200-ton Engel vertical press performs molding of an accessory drive assembly. Actual finished products are displayed at the press so that operators can see the ultimate placement of the parts being molded.

This plant operates under the concept of OEE, an acronym for Overall Equipment Effectiveness. Nightenhelser explains that it takes into consideration the availability of people, the availability of the equipment and first-time quality. It’s a calculated system that scores a company in all those categories. World class is considered 85 percent.

He’s proud to disclose another tangible number to communicate to the troops. PMC is in the 90 percent range.

“It’s just another tool to use,” he says. “It makes you look at, for example, why on third shift you have an availability issue. It will point out that you do not have the right number of people on that shift if your availability on that shift is low.”

CREATIVITY VERSUS CAPITAL

Jennings is happy to be in a place where PMC can think about a physical plant expansion up from the current footprint of 67,000 square feet. They already have done the preliminary analysis and can add about 21,000 square feet. But it’s not without thorough review and taking lean thinking into that analysis.

Within the last 18 months, PMC finished expansion of the clean room, which included the addition of a press, an ultrasonic welder and some assembly. But that total clean room space is configured creatively so that there is less need for capital outlay. The clean room is modular and expandable.

A lot of items are on casters so that the necessary secondary and testing equipment can be wheeled up and out. Workers can wheel up the assembly station for a certain job.

“It’s our way of flex manufacturing in the space that we have in the spirit of creativity versus capital,” she says. “Otherwise, if we had all this stuff fixed where it was, we’d need expansion a lot quicker.”

As an example of a highly complex medical part, PMC has an overmolded part that has five components that it assembles and then overmolds with Santoprene. It is then tested for 100 percent electrical functionality. This part goes into an electro-surgery device for one of the largest medical device companies in the world.

“I would say that we’re really excited to be in that position (of expanding),” she says. “But we are also going to really think about the right way to do that too. Is it build it and they will come? Is it, can we build but progressively add on to that over time depending on what the business requirements are? You can get all excited about putting 20,000 square feet on and outfitting it with everything you might need but you only have a press to put in there for the work you have committed from a customer. So I think the lean concept for PMC goes into how you expand, too. There is always a delicate balance because you want to optimize flow and future potential with not getting out ahead of yourself.”

ADAPTING TECHNOLOGY TO MEET ITS OWN NEEDS

When PMC cannot find a technology beyond its own walls, it will create it within. Take, for example, its Optimized Thermal Management System (OTMS) for injection mold temperature control. Jennings and Nightenhelser show off the area where this technology is in play – among the auxiliary equipment that is separated from the clean room injection presses. All the auxiliary equipment is located outside the clean room and its functionalities are transported through conduits.

PMC’s desire to run high-temperature materials is what led them to find solutions such as OTMS. PEEK is one of the primary materials. As Jennings puts it, most medical molders wouldn’t touch it because they don’t know how to run it. Outside of medical, those who mold PEEK would use hot oil.

That hot oil cannot be used in a clean room, however. Most people use electric cartridge heaters in their tools. But PMC had to figure out how it was going to control the temperature between 350 and 400 degrees Fahrenheit with electric cartridge heaters. Electric cartridge heaters only put heat into the tool; the heat cannot be pulled out. Once you pump it in, putting 700-degree material in there, the temperature of the mold can go way beyond 400 degrees Fahrenheit. PMC started looking at technologies to explore how it could be done differently.

It partnered with SINGLE (pronounced Sing-lay) using the SINGLE Temperature Controls STW200/1-6-25-HO.2 system which uses pressurized water for these high-temperature medical and implantable biomaterial applications.

“Water is much cleaner and much more efficient than running oil,” says Nightenhelser. “There are less leaks. The tools look better when they come out of the press.”

“It has been a huge selling point for customers,” Jennings says.

Cooling is almost instant. It can be up to six times slower when using oil. PMC now is taking this technology into automotive. It is converting some jobs that it ran on oil and even has begun seeing improvements in cycle times from the use of the technology.

PMC’s technical prowess is a point of pride for Jennings. Customers might not even know that something is possible.

“I think we’re really good at thinking through something that has never been done before,” she says. “Technically, a challenge that a customer has that they can’t figure out. Sometimes they didn’t know that what we were suggesting was even possible or that there was even a material available that could do what they needed to do. But then we go out and look for it, whether it’s an existing technology or taking an existing technology and applying it in a completely different way, which is really what happened with the pressurized water.”

As PMC has thrived on taking on highly complex devices with challenging materials, Jennings and Nightenhelser are honest about the challenge of finding tooling. Their customers always are demanding more in terms of tooling.

“Because the parts we’re pursuing in our niches are so technically complex, finding tool shops that are capable of building those tools is a challenge,” says Jennings. “We used to build tools in Cincinnati. We were a molder first and a tool builder second. But finding the tool shops that are at the tippy top of the pyramid, as we call it, that’s a challenge. We’re taking on more and more dimensionally complex parts. And that is more in automotive than it is in medical, for sure. Medical parts are more complex for completely different reasons. The tool shop situation, there are some great tool shops, always have been, but we’re really pushing the envelope.”

IMPLEMENTING THE POKA-YOKES

If you never have heard the phrase “poka-yoke,” it is a lean manufacturing concept for error-proofing. In Japanese, it means avoiding inadvertent errors. It is implementing habits or devices where errors are most likely to occur.

A molding cell, for example, would be designed so that the molding, robotics and any other automated functions cannot be performed incorrectly. This practice is perhaps best illustrated by what happened with a transfer tool that PMC received for a vibration control device for engine mounts.

The customer didn’t design the tool so that the parts could be aligned automatically and then put together. PMC has equipped the system with a special arm to align the top part to the bottom part to make sure they are aligned every time, says Nightenhelser. Inside the welding fixture, there is a sensor that detects the presence of a bladder. At a different stage of production, the part is sent through an overall height gauge before an ultrasonic welder will cycle the next time.

Elsewhere in the facility, Nightenhelser showcases the most-automated cell that is in production for automotive. Central to this cell is a 380-ton all-electric Roboshot and all the requisite automation for the task of making a part that goes atop an all-electronic steering housing. Two million pieces go through the press annually. It’s a PBT material with 30 percent glass. As you can imagine, this press is dedicated. There are only mold changes that occur, no material changes. This system has eight poka-yokes, three inside the press.

Every station has something to validate, whether the part has met the criteria to move to the next station, including vision systems and parts measuring. When the part is finished, it is ready to go to the customer’s electronic power steering assembly line.

“We want to confirm, in a simple, lean way, that a part is good before we add more value to it,” explains Jennings.

Angie DeRosa, managing editor

[email protected]