“For example, information from various sensors can be integrated and analyzed, enhancing computer-aided manufacturing simulation and offline G-code verification,” said Dave Davie, production manager at the Dayton, Ohio, facility for Lincotek Medical, an Italy-based contract manufacturer for the orthopedic, trauma, spine, and dental markets.
Even with additive manufacturing (AM) looming constantly in the wings, the demand for CNC subtractive machining remains robust in the medical device industry. This is largely due to a willingness to embrace process improvement in all areas and push current manufacturing systems (sometimes to the limits) for the quickest and most cost-effective process. OEMs and their contract manufacturers (CMs) are always looking for ways to improve machining and tooling, especially to reduce cycle times and get products to market faster. As OEMs continue to apply price pressures on their manufacturing partners for increasingly complex devices, CMs are forced to be more innovative with their equipment and their approaches to process improvement.
“As the medical device industry continues to focus on improved patient outcomes, it is vital to have production processes that provide stringent, repeatable, precise, and accurate finish components,” said Ray DeFrain Jr., regional metallurgist for Carpenter Technology, a Philadelphia, Pa.-based provider of high-performance alloy-based materials and process solutions for the medical device market.
“Additionally, linking these performance metrics with cost-down pressures of the industry at large, we see a shift toward megatrends of lights-out manufacturing and IoT [Internet of Things] mobile control of multiple CNC cells.”
According to John Kennedy IV, general manager for Autocam Medical, a Kentwood, Mich.-based contract manufacturer of implants and instruments for the orthopedic, spine, and robotic surgery markets, one of the biggest challenges CMs face is implementing continuous improvement activity in a fluid environment. “Many OEMs are looking for price-downs, but also handcuff the CM by requiring that all changes be requested prior to the improvement, no matter how small or large they may be,” said Kennedy. “Clearly, we understand the impact a process change may have on the final product. There is no standard available to the CM for which to guide what is necessary for a change request. To complicate matters, the speed at which many OEMs approve changes varies, so even the most minor requests can take months to approve.”
In the machining world, there is a gradual shift toward IoT-enabled equipment, utilizing technologies such as process automation, process integration, process control, high-speed lathing, milling, drilling, and 3D printing. Engineers and operators increasingly must have superb metallurgical, mechanical, and IoT knowledge to manage CNC needs for increasingly complex devices.
In orthopedics, especially 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 which were used in the past. “This makes it possible to decrease grinding cycle times and increase output per wheel,” said Florian Dierigl, business development manager for the medical industry for TYROLIT, an Austrian-based manufacturer of bonded grinding, cut-off, sawing, drilling, and dressing tools. “As a result, less frequent tool changing and, therefore, reduced tool changing time is achieved because of longer lifetime of the grinding tool. The same is true for grinding artificial hip cups, where productivity can be raised by nearly 90 percent using super-abrasive tools, reducing cost per parts for the customer.”
Other trends include developing hybrid equipment that combines laser cutting and subtractive and additive technologies in a single platform, as well as increasingly sophisticated micro-machining and bar-fed multi-axis machining, sometimes developed as customized equipment between MDMs and their contract manufacturers and machine tool manufacturers.
What OEMs Want
Many OEMs in the orthopedic market are intent on improving surgical procedures and patient outcomes, which often involve miniaturized and more complex devices.
“OEMs require process consistency at the right cost on one side and increasingly complex geometry on the other side to satisfy evolving surgical scenarios where usability, endurance, and weight play a role in a surgeon’s performance,” said Enrico Sandrini, general manager for Lincotek Medical in Bologna, Italy.
To meet the challenges of increasingly complex devices, CNC machinists are constantly mixing different technologies. Modern CNC equipment is easier to program and provides high-precision process control. Machines can be interconnected to maximize quality and throughput, increasing production capacity.
OEMs are constantly pushing their machinists to use these advanced technologies to reduce costs. OEMs also want higher quality standards, tighter tolerances, and faster speed to market. They are always looking for process advancements that can increase throughput and shorter lead times. In addition, they want more technical expertise and guidance from their CMs. More OEMs are asking their CMs to collaborate on the development of new parts and products, including design, materials, prototyping, and testing, and expect them to have the technical prowess they need to deliver the right solutions quickly.
Although MDMs may approach their contract manufacturers with a particular machining method in mind, most are open to suggestions that make more sense from a production viewpoint. “Customers certainly want to be sure we have the capabilities and process controls in place,” said Tim Hoklas, senior director of technical solutions for Viant, a Foxborough, Mass.-based global outsource developer and manufacturer of medical devices and components. “But for many MDMs, it’s less about process and more about results. They might come to us with a particular process in mind for a component, but we may suggest something that’s a better match to their objectives. In one instance, we converted a machined part to a molded part and reduced the cost by 75 percent.”
The CNC world is rapidly evolving, including the combination of different technologies to meet increasingly challenging demands by OEMs. Modern CNC machines are faster than standard machines and easier to operate and validate. Tolerances are often in the range of a few microns, which requires top tooling. Other needs include climate control, ultra-clean shops, and quality inspections with visual software and advanced coordinate measuring machines. When combined with other technologies, such as additive manufacturing (AM), CNC machining can turn the complex designs of surgeons and medical device designers into orthopedic products that improve and extend quality of life in amazing ways.
For CNC today, control probes are required to keep production under control and avoid over-control after machining. Combining machining and quality control in one step not only means more accurate process control, but also less scrap and reworking in a cycle and overall improved efficiency.
“New laser-based technologies such as laser micromachining and cutting allow us to combine 3D printing with machining, opening a wide new range of production possibilities and process improvements,” said Enrico Sandrini, general manager for Lincotek Medical in Bologna, Italy. “The combination of CNC and AM will pave the way to a new era for machining.”
Material advancements are just as important as machining advancements, especially with the demand for smaller devices that require both the precision of CNC machining and the characteristics of next-generation materials, where more performance is packed into smaller unit volume. “For example, Carpenter Technology’s BioDur 108 alloy, which takes the performance expectations of an industry standard, vacuum-melted 316 stainless, and increases the strength, corrosion resistance, and fatigue,” said DeFrain. “As an essentially nickel- and cobalt-free alloy, it also supports regulatory and metal allergy concerns, as well as enhanced biocompatibility and the trend towards minimally invasive surgeries.”
Miniaturization of components and overall devices is a common goal in the medical device industry to support improved patient outcomes through minimally invasive surgeries. “Miniaturization also requires advancements in both processing and materials,” continued DeFrain. “For example, 17-4PH is a commonly used material that can be substituted with Custom 465 stainless as a drop-in replacement with increased strength and hardness, while still retaining very high levels of ductility and corrosion resistance.”
With these trends, there is a growing focus on the quality and consistency of the input feedstock material. Material producers are working hard to improve the consistency and reduce the residual stresses developed during material processing to support consistent machining expectations from the workpiece.
CNC equipment can also machine next-generation materials in the pre-hardened state.
“This showcases the capability of both tooling and the rigidity of the CNC equipment today,” said DeFrain. “Alloys such as 440A and 17-4PH—workhorses of the medical industry for instrumentation—are now being machined in the fully heat-treated condition to minimize any deflection and/or size change that would arise from a finish size heat treatment.” This again exemplifies the linkage of CNC to the needs of the industry at large, where precision components can continue to leverage more out of the CNC platforms of today and will continue in the future.
For grinding, TYROLIT offers an innovative core material for super-abrasive grinding wheels. This equipment is especially beneficial for the CNC machining of artificial knee implant components. It has the same damping properties as carbon fiber but is lighter in weight and costs less per part than other comparable tools with a carbon fiber-reinforced polymer core. “Our core material, when combined with our vitrified bond solution for cubic boron nitride, can reduce grinding cycle times by nearly 60 percent,” said Dierigl.
Automation continues to impact efficiency and quality. Advanced controls and remote monitoring capabilities allow manufacturers to problem-solve in real time, creating a more consistent machining process. For example, “many of our automated machines are set up with probes that measure cuts and dimensions during production,” said Phil Allen, vice president of sales and marketing for Lowell, a Minneapolis, Minn.-based contract manufacturer of orthopedic, cardiovascular implant, and instrument devices and products. “These measurements are analyzed by a control system that automatically determines if measurements conform to requirements. If measurements are drifting, the control system can automatically adjust the offset before it causes an issue.”
Perhaps the most critical factor to machining is understanding design intent.
“We talk a lot about design intent during pre-production meetings so we can better understand how a part will be used, how components fit together, what a surgeon needs from the device, and how the implantable device and instrument will interact,” said Allen.
Another consideration is stack-up. As device assemblies become more complex, and multiple manufacturers are contracted to create individual pieces of an assembly, design intent becomes extremely important to manage tolerance stack-ups and ensure parts work together and assemble as designed. If the tolerance stack-up is wrong, or the process needs to be adjusted, time to market can be delayed.
During these pre-production sessions “we usually present ideas that will make a part simpler or more cost-effective to machine,” Allen added. “By understanding the part’s features and why they were designed as they were, we can make appropriate suggestions to improve manufacturability before any machining is done.”
For example, a customer wanted Lowell to mask the threads of a component that was going to be bead-blasted. The Lowell team understood that doing this would add time and expense to the project; based on their experience, however, the Lowell engineers knew that bead blasting would not affect thread conformance or functionality. After discussing this during the meeting, the customer decided to remove the masking steps, which saved considerable time and expense.
Peridot Corporation, a Pleasanton, Calif.-based provider of custom device/instrument manufacturing for the medical and technology industries, has invested heavily in fiber-delivered laser workstations for tube cutting, sheet cutting, and laser engraving. Fiber lasers are faster and more precise than CO2 gas-excited tube lasers. Other advantages include up to 50 percent higher throughput, fully automated tube loading, advanced cutting heads, and easy workpiece removal even during the cutting process.
“For sheet and tube laser processing,” stated Patrick E. Pickerell, president of Peridot Corporation, “fiber delivery typically means less dross and therefore less cost in post-laser processing, such as deburring. This technology enables us to tackle features as small as 25 microns with greater accuracy. Also, you are not going to check these parts with hand-held instruments such as calipers or micrometers—these fine features demand the latest in vision system metrology.”
Machining, Industry 4.0 Style
As a manufacturing technology, machining lends itself perfectly to the Internet of Things. With the precision and speed OEMs require today, collecting and analyzing machine data from the sensors and controls in the grinding equipment is essential for optimizing the production process. IoT is increasingly used to support both product traceability and overall equipment effectiveness performance. As IoT gains popularity, “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,” said DeFrain.
Data acquisition is typically managed by dedicated collector PC software, whereas the data is stored on server PC software. The server PC usually provides a web-based user interface for data access and visualization that can be accessed from any PC or tablet computer on the network with a browser. For small systems with only a few machines, collector software and server PC software can run on a single standard personal computer. Up to 100 machines can be handled by one server.
ToolScope is a modular assistance system designed by TYROLIT that connects grinding technologies through IoT methods. Because it is directly integrated into the machine controls, ToolScope easily accesses and evaluates machine data, production data, and process data in a simple manner, without external sensors.
“Each machine can be set up easily within a short period of time and every aspect of the grinding process is monitored in real time,” said Dierigl. “The program can answer questions such as, after a part loads, when does the actual grinding process begin? Is the grinding wheel being utilized properly? How does the same material obtained from different suppliers respond to grinding? What are the best ways to respond to variances?”
The other major Industry 4.0 technology is additive manufacturing, which is advancing at a record pace. Even so, AM can never fully replace CNC machining. Although AM can make some complex devices that machining cannot, “it cannot produce the tight tolerances, low surface roughness, or high quantities required by many applications,” said DeFrain. “Additionally, CNC machining is established with known performance standards—AM has a long road ahead with respect to adoption in critical components.”
Lasers are still one of hottest market segments in CNC machining—laser cutting, laser welding, laser texturing, and laser knurling. Combining laser processing with machining in hybrid equipment eliminates steps and saves time. For example, by combining laser cutting and welding with traditional Swiss turning, laser-Swiss machines can perform multiple processes in a single set-up, which also streamlines the validation process. The trend toward hybrid equipment also drives costs down by shortening lead times for prototyping and production volumes. Swiss-turn machining and laser cutting can be combined for laser-cut slots and holes and simultaneous machining of differing outside diameters, which reduces setup time, secondary processing, and handling costs.
CNC and AM are, however, not mutually exclusive. Machine manufacturers are building hybrid, dual-purpose machines that incorporate AM build-up and CNC tolerances, speeds, and surface finishes in both series and parallel operations. “Feeding in a semi-finished component, and then performing both subtractive and additive manufacturing processes, can leverage the best portions of each production methodology,” said DeFrain.
For example, the AMBIT tool piece manufactured by Hybrid Manufacturing combines AM and CNC machining in a single machine through its innovative tool-changeable laser cladding heads. The equipment utilizes a combination of a laser as the energy source and deposited metal powder to build up material onto the desired substrate. Upgrading a CNC machine with metal deposition gives both additive and subtractive machining capabilities in a single system. Changeover between the heads is completely automated and only takes seconds. AMBIT is especially useful for repairing high-value metal components and adding features onto existing parts, and can be retrofit for existing CNC machines.
Machine companies know that, with increased pressure from AM, they must continue to innovate and advance the capabilities of their machining equipment to meet the increasingly challenging demands from OEMs in the orthopedic space. Customers are demanding reduced cycle times and better cutting tools, work-holding, and cutter paths. 3D laser texturing is beginning to replace traditional manual sandblasting and/or chemical etching processes with a more accurate, adjustable, and fully digital process that provides improved surface quality and lower manufacturing costs.
Net-shape 3D printing of biocompatible materials such as TI6AL4V titanium is starting to gain traction. CNC manufacturers are working to improve the cleanability of their equipment and increase performance with the support of biocompatible lubricants.
New machining methods are being developed for challenging materials such as Nitinol, which is a notoriously difficult material to machine and takes a vast amount of operational skill and experience. “Some OEMs believe that Nitinol cannot be processed by chip-based subtractive machining,” said Pickerell. “However, we have pioneered some very novel machining techniques that are highly effective for this type of machining.”
Ultimately, there is not just one way to machine.
“The real question,” said Jeff Goodman, vice president of business development for Autocam Medical, “is what are customers willing to pay for in terms of technology and innovation? What might have been perceived as a machining miracle a few years ago may be quite commonplace today in our market. As we continue to innovate ways to accomplish a final outcome, there may be a steeper price to pay, and some customers may not be willing to accept the new reality. But, with speed-to-market as a primary goal of OEMs, an initial cost can easily turn into an investment for their future.”
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.