Modernizing Machining Through Material and Technology Advancements

Machining is one of the hottest sectors in the orthopedic market. Medical device manufacturers (MDMs) emerging from the pandemic have presented a backlog of projects for their machining partners, with compressed timelines to match. With machinists in short supply, there is even greater interest in using automation, robots, and Internet of Things applications to stay operational and competitive. However, despite all this bustling activity, signs of instability are still present—for example, supply chains remain unsteady.

“Some supply chain material lead times are increasing and the prices of certain raw materials and consumable supplies are going up,” said Michael Raasch, business development manager for XACT Wire EDM Corporation, a Waukesha, Wis.-based provider of wire EDM (electrical discharge machining) services. “Some devices and components are also being reshored after experiences with disruptions due to the pandemic.”

Graham Immerman, vice president of marketing for MachineMetrics, a Northampton, Mass.-based provider of machine data platforms that monitor and analyze data from manufacturing equipment, agreed.

“Supply chain restructuring has been accelerated by the COVID-19 pandemic,” he said. “Many medical device companies are looking to restructure their supply chains, trying to support rising demand with a balance of resilience, efficiency, and reduced costs. More companies are also considering reshoring as a solution, with a recent study showing that 70 percent of companies queried¹ were likely or extremely likely to reshore in coming years.”

“Most of our medical OEM customers serve elective surgery markets,” said John MacDonald, president of AIP Precision Machining, a Daytona Beach, Fla.-based provider of ultra-precision machining of plastic and composite materials for the medical industry. “In late Q1, the availability of effective vaccines and declining COVID-19 rates resulted in a strong return of demand, including a strong appetite for new product development from both existing and new orthopedic customers.”

Orthopedic MDMs continue to design and develop smaller, more advanced, and more complex medical devices (especially for the minimally invasive market) than ever before, which require production processes that can provide stringent, repeatable, precise, and accurate finish components at very small scales. Modern computer numerical control (CNC) machines are designed to meet these high-precision challenges with more automated capabilities and improved process controls. These expectations, when combined with the cost-down pressures of the industry at large, are creating a trend toward “lights-out” manufacturing and Internet of Things (IoT) mobile control of multiple machining cells.

“The utilization of tooling technologies, which adapt to changing manufacturing requirements, increases productivity and operational flexibility,” said Dan Walker, director of business development for Tsugami/Rem Sales, a Windsor, Conn.-based exclusive importer of Precision Tsugami CNC machine tools, including lathes and milling machines. “Quick-change tooling, oscillation cutting, lights-out machining, and more powerful CNC controls generate more up-time with less intervention.”

Latest Trends
Cost pressures and supply chain worries continue to weigh down MDMs, causing many of them to consider reshoring. However, reshoring also comes with pressures to deliver products in record time and still turn a profit, all while controlling or reducing costs, finding and hiring skilled labor, and boosting productivity. To be competitive, MDMs and their contract manufacturers (CMs) must find ways to increase efficiencies—largely through the investment in IoT technologies that maximize performance, quality, and speed.

“There has never been a more important time to reduce the burden of non-essential manual tasks and decision-making,” said Immerman. “Continuous improvement via automation starts with capturing insights from the heart of manufacturing operations—specifically the machine assets that make these products and the people that run them.”

Machining equipment in the medical device market is worth hundreds of thousands of dollars and produces more data than in many other industries—yet this information is often not captured or analyzed to improve efficiency and performance, despite the continued innovation (and increased affordability) in robotics and automation. “IoT systems optimize manufacturing processes by using machine data, leveraging real-time analytics, and remotely monitoring machines, all of which can maximize shop floor operations and contribute to large increases in productivity,” added Immerman.

Material advancements are just as important as machining advancements for achieving the manufacturing and product performance goals for orthopedic implants and devices. For example, tight chemical and processing control of raw materials ensures reliable yield during production and repeatable, expected machining performance. “As trends towards minimally invasive surgeries continue, the need for smaller devices will require both the precision of advanced machining and the characteristics of next-generation materials, where more performance is packed into a smaller unit volume,” said Ray DeFrain, Jr., field metallurgist for Carpenter Technology, a Philadelphia-based melter and manufacturer of metal bar, wire, strip, plate, and powder. “For example, Carpenter’s BioDur 108 alloy takes the performance expectations of an industry standard—vacuum-melted 316 stainless—and increases strength, corrosion resistance, fatigue, and biocompatibility, while concurrently removing nickel and cobalt for regulatory and allergic concerns.”

MDMs are always looking for ways to increase quality, reduce lead times, and save money. One way to accomplish this is by implementing improvements that can increase throughput and decrease scrap rates—which can simply be a change in material. “Miniaturization of components and devices often require advancements in both processing and materials, such as Custom 465 stainless,” said DeFrain. “This drop-in replacement for 17-4PH delivers increased strength and hardness, while still retaining very high levels of ductility and corrosion resistance.”

What OEMs Want
MDMs are keen on having a strong supply base, with Tier-1 suppliers that totally understand their needs and only work with top CMs downstream—not just for their technological abilities, but also the quality and capacity they bring to the manufacturing process.

“These manufacturers are looking for a supply chain that embraces advanced technologies that improve quality while reducing costs,” said Walker.

“MDMs want parts that meet specification, are on time, and priced to be economically feasible for the given product,” added MacDonald. “At the end of the day, those are the demands and in that order of importance.”

Being highly cost-sensitive, especially emerging from the pandemic, MDMs can have a hard time making decisions on cost per part, what to add or take out of a design, and how those changes could impact functionality, performance, and sales. “It is not always the cheapest product that brings the highest advantage for the customer,” said Florian Dierigl, business development manager for the medical industry for TYROLIT Schleifmittelwerke Swarovski K.G., a Schwaz, Austria-based manufacturer of bonded grinding, cut-off, sawing, drilling, and dressing tools. “Engineers should be involved more in the decisions to find a balance for price/performance.”

Reliance on CMs for their manufacturing know-how and problem-solving is a continuing trend for MDMs, which allows them to focus their resources on R&D and design. They expect their trusted CM partners to make their products better—from sharing material knowledge to design changes to the different levels of machinability or biocompatibility—for a range of orthopedic devices. Design activity is especially high in the foot and ankle sector for implants and carbon-fiber, polyetheretherketone (PEEK)-based radiolucent surgical tools, as well as surgical navigation tools.

“Surgical navigation technologies continue to advance and incorporate more polymer parts to reduce metallic component interference, which has proven to be very successful,” said MacDonald. “Many of these components require extremely tight tolerances, down to a true position of 0.0005 inches.”

New Technologies and Advances
Materials and technologies in the highest favor with MDMs are those that accelerate product development, maximize quality, and reduce costs. For example, when grinding femur parts for artificial knee implants, the trend is toward using state-of-the-art super-abrasive grinding wheels, rather than the conventional aluminum oxide grinding wheels used in the past. These super-abrasive wheels have the same damping properties as carbon fiber but are lighter and cost less per produced part.

“This makes it possible to decrease grinding cycle times and increase output per wheel,” said Dierigl. “As a result, less frequent tool changing and, therefore, reduced tool changing time is required because of the longer life for the grinding tool. This has allowed customers to reduce the grinding cycle time from 12 minutes to about 4.5 minutes, meaning a productivity increase of about 60 percent.”

Another advancement that saves time is using hybrid equipment—for example, combining laser cutting and welding with traditional Swiss turning in a single machine that can perform multiple processes in a single set-up. This is especially effective for laser-cut slots and holes and simultaneous machining of differing outside diameters, which reduces set-up time, secondary processing, and handling costs. Additive manufacturing can also be added, as well as increasingly sophisticated micro-machining and bar-fed multi-axis machining. The trend toward hybrid equipment also drives costs down by shortening lead times for prototyping and production volumes.

“Hybrid equipment can make small, high-precision cuts that cannot be achieved by conventional machining,” said Walker. “Our LaserSwiss technology, which combines multiple separate operations into one, provides cost savings to the end user while significantly reducing takt time and scrap and improving process capability, while delivering quick ROI.”

Oscillation cutting is another technological breakthrough that oscillates a servo axis to help break up chips in tough-to-cut materials. This action reduces heat in the cut, but does not diminish tool life or surface finish. “By oscillating the specified axis, cutting is performed by synchronizing the oscillation of the specified axis with the rotation of the main spindle,” said Walker. “Interruption in the cut by oscillation breaks material into small chips rather than long stringy ones. Productivity is increased by significantly reducing operator intervention to remove hanging or ‘bird-nesting’ chips.”

Wire EDM is a very effective process for prototype through production volume on medical applications that require close tolerances and good surface finishes. Tight temperature control and calibrations are also critical. Any conductive material can be machined with wire EDM. In many cases, parts can be stacked or chained together and very efficiently produced. With tolerances as tight as ±0.002 mm, inspection can become a challenge. “Vision inspection at a very high magnification [100-300x] can complement coordinate measuring machine [CMM] inspection, especially when checking delicate, fragile parts or tiny features,” said Troy McGroarty, quality assurance manager for XACT Wire EDM Corporation. “Non-contact vision inspection is essential for the medical device and orthopedic projects that we see on a daily basis. If you can accurately measure extremely small, detailed EDM-cut features, you can improve their accuracy and consistency. We frequently cut with 0.004 inches [0.1 mm] wire to generate radii down to 0.003 inches [0.08mm].”

Near net shape (NNS) manufacturing is an approach that makes the first version of a component as close as possible to the actual shape and dimensions of the finished product. The goal is to reduce material waste and machine time, which in turn reduces production costs. Near net shape manufacturing is especially valuable when using high-cost materials, such as titanium alloys. Other advantages include less wear on machining equipment and reduced waste disposal costs.

NNS technology can be used to produce orthopedic implants, such as large joint orthopedics, knee and hip implants, spinal cages, and suture anchors. The technology enables orthopedic implants, tools, and devices to be produced in nearly-finished forms that are close in shape to the final product.

“NNS technology reduces systems costs when machining finished components from expensive highly regulated implantable thermoplastic materials such as PEEK, ultra-high molecular weight polyethylene [UHMW-PE], and the emerging UHMW-PE/PEEK hybrid for implant designs for orthopedics,” said Eric Tech, global market segment manager for healthcare at Mitsubishi Chemical Advanced Materials in Bellmawr, N.J. “NNS can reduce or even eliminate the need for surface finishing like machining or grinding and delivers bottom-line benefits that can result in significant savings in production costs.”²

Manufacturing processes that can achieve NNS include additive manufacturing, linear and rotary friction welding, casting, and injection molding. PEEK polymers are especially well-suited for orthopedic implants and NNS technologies, which “can improve mechanical strength and can reduce material mass by 15 percent to 45 percent when PEEK hollow profiles are produced,” Tech added. “The unique technology can provide a near net shape benefit with removal of 5 percent to 25 percent of the UHMW-PE in the raw material blank size. Complementary benefits are a reduction in machining time and less waste material, which is an important consideration for meeting sustainability goals.”²

Internet of Things
The IoT is a relatively easy and effective way to improve the efficiency of manufacturing operations. Using IoT hardware, sensor technologies, and software programs, MDMs and their CMs can build digital transformation strategies that:

• Monitor equipment performance for developing proactive maintenance policies and improving product quality and capabilities
• Aggregate and analyze data to help MDMs optimize machine utilization
• Deliver or integrate actionable insight into factory operations and workflows
• Integrate both available and upgraded industry standards into workflows and produced equipment
• Enable the creation of new revenue streams to support small or declining profit margins.

“IoT is today’s want and tomorrow’s expectation,” said DeFrain. “We see a shift away from the traditional machinist linked 1:1 with a particular machine and instead see a single engineer linked to multiple machines—often off-site and controlling remotely. Furthermore, it would not be surprising to see the effects of the COVID-19 pandemic drive further adoption of these practices.”

MachineMetrics, for example, is connected to thousands of machine tools, enabling its data scientists to build algorithms that can predict quality defects and extend tool life. It recently launched MachineMetrics Tool Monitoring, an adaptive tooling technology that enables MachineMetrics to diagnose, predict, and automatically prevent the machine tool failures that lead to broken tools, scrap parts, and costly downtime. “Our machine learning/artificial intelligence algorithms detect patterns from the hundreds of data items collected from each machine that can detect these problems before they occur again and stop the machine before failure occurs,” said Immerman.

Additive and Subtractive
The orthopedic device market is one of the fastest-growing industries for additive manufacturing (AM). Additive manufacturing is suitable for complex parts, internal features, and low-volume components. AM is a slower process compared to CNC machining, as the various layers of material require time to heat and solidify, making it too slow for large-scale production.

Both traditional and advanced CNC machining will not be replaced by AM. Currently AM cannot produce the tight tolerances, low surface RA, or high-volume parts that CNC machines can make. In addition, machining has established known performance standards—these are still being developed for AM. That said, machining (subtractive) and additive manufacturing can also complement each other—for example, machining is often needed as a secondary operation to finish an AM-made orthopedic product.

“Additive manufacturing will definitely have its place in the manufacturing world,” said McGroarty. “However, wire EDM will still be needed to attain the precise geometries and close fits that many of these AM orthopedic components require.”

“As AM evolves, we are seeing dual machines that incorporate AM build-up and machining practices—driving tolerances, speeds, and surface finishes in both series and parallel operations,” added DeFrain. “Feeding in a semi-finished component, and then performing both subtractive and additive manufacturing processes to it, can leverage the best portions of each process.”

Moving Forward
Lasers continue to be used in creative ways to make tiny, high-precision features in orthopedic products. Laser micromachining can remove material in nearly any shape or pattern. Features as small as a few microns in diameter are achievable and sub-micron kerfs are possible for very thin materials. Ultrafast, femtosecond laser machining is especially useful for the production of precision components with complex patterns. These laser systems are good choices for prototyping, low-volume production of intricate parts, and high-volume manufacturing of less-complex parts. An increasing number of orthopedic device companies utilize femtosecond lasers to texture surfaces of orthopedic implants, such as hip joints and dental implants, to aid osseointegration. Because the material removed by the laser is vaporized, parts are typically contamination-free and burr-free and require no or minimal secondary processing.

Machining advances in orthopedics will continue to be technology-driven and material-driven.

Advanced machining will rely on minimal run-out to ensure consistency, minimal user involvement, tight tolerances, and repeatability from piece to piece. Material consistency and repeatability is considered a critical first step in setting up lights-out manufacturing or off-site IoT-controlled capability.

Carpenter Technology is currently developing a minimum residual stress 17-4PH bar stock for some unique medical machining applications to ensure consistency from bar to bar. Ultimately, this will minimize deflection during the machining operation and enable advanced, hands-off manufacturing of complex and thin-wall geometries. Secondary operations could also be eliminated due to first-time through acceptability. “This would be a game-changer for many of the medical component machining practices, especially as we continue this development project with other metal alloy systems,” said DeFrain.

To keep up with the intense capacity demand from their OEMs, a CM and MachineMetrics client ran its machines at 200 percent capacity, simply accepting the lost time and materials due to tool failure as part of the cost for keeping this job. The CM enlisted MachineMetrics’ tool monitoring technology to diagnose, predict, and automatically prevent these machine tool failures. MachineMetrics identified the signals on their machines that indicated catastrophic tool failures were imminent. Parts made during these elevated load periods also had quality problems, costing the CM more time and money.

“Over time, a predictable pattern emerged, indicating with 99 percent accuracy when a machine tool would be likely to fail, allowing the client to prevent the failures that led to broken tools, scrap parts, and costly downtime,” said Immerman. “This solution essentially eradicated all scrapped parts from their production, which equated to about $6,000/machine/month of value, or $72,000 a year per machine. Across their production fleet, the impact was remarkable to their bottom line.” 

References

1. bit.ly/odt210921
2. bit.ly/odt210922

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Mark Crawford is a full-time freelance business and marketing/communications writer based in Madison, Wis. His clients range from startups to global manufacturing leaders. He also writes a variety of feature articles for regional and national publications and is the author of five books.