With increased complexity, functionality, and finer features in orthopedic products, combined with the industry’s intense focus on speed of production and delivery, CMs must have a wide range of tooling and technology options and know how to use them—from standard machining tools like computer numeric control (CNC) machines to the latest innovative technologies such as additive manufacturing. And although the orthopedic industry still relies on traditional CNC machine tools to produce many devices and components, newer and more complex designs challenge the limits of traditional machining methods. This is where CMs need to be experts on the latest machining methods—whether it is new technology, hybrid equipment, robotics, or automation solutions, such as automatic loading and unloading.
Orthopedic designs are increasingly influenced by human factors engineering and considerable input from surgeons. As a result, increased feedback from the operating room leads to more innovation, R&D, and redesign of orthopedic implants and instruments, which sometimes call for an equal amount of innovation in engineering new tooling.
Also, as devices get smaller and more multifunctional, more MDMs are turning toward design for manufacturing (DFM) to be certain they are doing everything they can to maximize quality, reduce risk, and control costs. This is especially important as the regulatory landscape continues to evolve. MDMs realize that to get their products to market faster without sacrificing quality, they need DFM—an integral part of which is machining and tooling. Rapid prototyping is often used during this stage to test different tooling designs.
Other challenges for orthopedic companies are skilled workforce restraints, quick turnarounds, and smaller lot sizes. Tooling improvements designed to meet these challenges provide a competitive advantage and allow CMs to operate more efficiently than ever before.
“The utilization of tooling technologies, which adapt to changing manufacturing requirements, increases productivity and operational flexibility,” said Dan Walker, director of business development for Windsor, Conn.-based Tsugami/Rem Sales, a manufacturer and distributor of CNC Swiss lathes, machining centers, and milling machines. “For example, quick change tooling, oscillation cutting, and lights-out machining, all within the Industrial Internet of Things, generate more up time with less intervention.”
What OEMs Want
OEMs are constantly seeking ways to reduce processing times while still meeting or exceeding stringent quality standards. As a result, they often ask their CMs for increased engineering assistance in custom tool design and quality assurance processes, with a focus on greater up time, less interference, quick changeover, and improved predictability and reliability. More complex orthopedic designs typically require custom tooling solutions. Each tooling solution is determined by multiple factors, including part shape and material, the features being generated, machine setup, and programming. OEMs count on their CMs to have confidence in their abilities and be able to meet their often-challenging production demands.
Increasingly, MDMs and their CMs seek tooling that provides the best rigidity, high-pressure coolant capabilities, and effective chip control. All these factors impact machining consistency, part quality, throughput, speed to market, and lower production costs.
MDMs want their CMs to design the most efficient manufacturing process for their products—this increases efficiency, reduces opportunities for error, saves time, and gets products to market faster. One of the best ways to do this is reducing the number of steps whenever possible, which in turn, reduces changeover time. For example, broaching tools can be attached directly to CNC lathes and mills to cut features in parts, instead of transferring parts to a separate broaching machine.
“By virtue of not having to broach as a secondary operation, or use other time-consuming machining methods, manufacturers can save an immense amount of time creating complex forms with rotary broaching tools, right on their standard CNC machines,” said Kris Renner, director of operations for Slater Tools, a Clinton Township, Mich.-based manufacturer of precision CNC broaching tools and inspection gages. “This means they can cut interior diameter or outside diameter forms at the same time they are completing their other machining operations. With rotary broaching, complex forms like splines and hexlobes can be machined in seconds with speeds and feeds upwards of 2,500 RPM and 0.007 IPR [feed rate, inches per revolution], while still maintaining incredible accuracy. Furthermore, by utilizing custom-made plug or ring gages, timely inspection processes are eliminated.”
Technologies Focus on Efficiency
Thread whirling systems are important to manufacturers of implant screws, where orders can range from 1,500 to 5,000 pieces per production run or more. These machining systems are designed to efficiently manufacture threads for high-production jobs. Bone screws are being designed with more complex thread forms, including deep threads, multiple leads, and unique thread pitch. Inserts are specifically designed and manufactured for individual threads. Many medical threads are also designed to incorporate multiple leads and all medical parts require holding tight tolerances.
“The ability to create the thread form by removing material from the bar stock in a single pass results in reduced cycle time compared to multiple passes with a single point threading tool,” said Steve Easterday, Swiss product manager for Wixom, Mich.-based NTK Cutting Tools USA, a manufacturer of Swiss-style toolholders, inserts, and unique tooling components. “Whirling inserts have stronger edges because the clearance is achieved by rotating the spindle. Multiple inserts with sharp cutting edges and specially developed profiles deliver excellent surface quality and in-spec parts. Because the spindle operates close to the guide bushing, or an extended bushing, whirling technology provides support and rigidity especially beneficial on long-length components with small diameters. This rigidity also results in the finest surface finishes.”
Another important part of a bone screw is the socket feature. Tolerances are tight for socket dimensions and the machined pocket must be consistent throughout the large production lot. Broach tools are the typical go-to style for socket machining, which can, however, lead to increased tool pressure, tool wear, and tolerancing issues. An alternative approach is NTK’s easy-to-use Shaper Duo series of tools, which uses a special grinding process to provide sharp corners on stick-style inserts to shear the material during socket generation for less tool pressure and consistent tolerances.
Hybrid machines combine laser cutting or welding with conventional multi-axis CNC Swiss milling to create a single platform where the operator can easily switch from one technology to the other as needed—a vast improvement over the standard approach of cutting first on a traditional lathe and then moving to a laser machine for cutting. Popular platforms are five- to six-axis systems that support multiple laser types. Hybrid systems are ideal for micro hole-drilling and cutting fine features with no heat-affected zones, producing precision parts in seconds, with positional accuracy in the ±1.0 µm range and ±0.5 µm repeatability.
Integrating laser cutting into a CNC Swiss lathe allows the machine to make small, precision cuts that cannot be achieved using standard machining methods. Combining traditional machining and laser processing into one machine also reduces set-up time and parts handling and provides better precision with less variation. Ultimately, “LaserSwiss technology provides cost savings to the end user while significantly reducing takt time [the rate at which a finished product needs to be completed in order to meet customer demand] and scrap, and improving process capability, all while delivering quick return on investment,” said Walker.
Another trend is the push toward merging multi-axis CNC machining with additive manufacturing (AM) methods, a process known as “hybrid manufacturing.” In this approach, additive processes—such as direct metal laser sintering —are combined with subtractive processes, such as milling, in a single machine system. The system creates its own near-net part shape using the on-board AM method, which is then precision-machined into dimensional tolerance with the CNC portion of the machine. In many cases, the AM portion of the system consists of a tool or robot arm equipped with a directed energy deposition (DED) head that deposits layers of metal powder, which are welded together and then machined. Some hybrid manufacturing systems also process polymers, typically via material extrusion.
More Technology Advances
An increasing number of companies are using high-pressure coolant lines with quick-change connectors. This makes the process of tooling changing more efficient and reduces machine down time. The high-pressure coolant is used to evacuate chips from the cutting area. “This reduces the potential for chips wrapping or packing up around the part during material removal, which could scratch the machined surface,” said Easterday. “The build-up of chips would require the operator to pause the program in order to remove the chips. The use of high-pressure coolant flowing over the insert helps keep the temperature consistent and protects the sharp insert edge, improves the tool life and part tolerance, and maintains surface finish.”
Other advanced features include running coolant through gang stations. This eliminates the need for high-pressure coolant line connections to each tool in the gang; instead, the coolant flows through the gang plate and into specially designed coolant through holders.
The industry is also seeing new chip-breakers designed for specific operations on Swiss machines in order to direct chips away from the part. The design of the breaker takes into consideration the way the material comes off the part during machining. “It is important to mechanically control the chip as the insert is cutting into the material,” said Easterday. “Special surface features molded or ground into the insert will force the chip to bend and fold tightly. The cutting conditions will impact the effectiveness of chip-breakers so dialing in the parameters based on the application is always beneficial.”
Circle segment end mills are a relatively new type of tooling designed for five-axis milling that provides a larger tool path distance during pre-finishing and finishing operations. The end mills enable large radii in the cutting area of the respective tool, which can vastly reduce finish-milling times for workpieces featuring geometric contours.
“We are seeing improvements in circle segment cutting tools for roughing and finishing,” said Philip Allen, vice president sales and marketing for Lowell, a Minneapolis, Minn.-based contract manufacturer of complex implants for the orthopedic and cardiovascular markets. “These tools allow for larger stepovers in a five-axis environment. The leading manufacturers are touting an 80 to 90 percent increase in efficiency.”
Oscillating cutting is another technological breakthrough that oscillates a servo axis to help break chips in tough-to-cut materials. The system reduces heat in the cut, while maintaining tool life and surface finish. This function oscillates the specified axis, and cutting is performed by synchronizing the oscillation of the specified axis with the rotation of the main spindle. “Interruption in the cut, or air cutting, break material into small chips rather than long stringy ones,” said Walker. “Productivity is increased by significantly reducing operator intervention to remove hanging or ‘bird nesting’ chips.”
This cutting technique can be used for turning, drilling, boring, or grooving operations. Productivity is increased by significantly reducing operator interruption to remove hanging or “bird nesting” chips. Oscillation parameters can be changed easily to machine multiple features with multiple tools.
Smaller, more complex parts with tighter tolerances often require advanced automated vision systems to ensure they are within spec. As tolerances get tighter, the CM’s ability to measure the dimensioned features accurately becomes more challenging. What used to be measured easily with an optical comparator now often requires an automated coordinate measuring machine (CMM), or even more advanced equipment. Optical vision inspection is nearly error-free and essential for maintaining manufacturing throughput. Capabilities include automatic recognition of position and orientation of multiple parts and scanning parts in seconds to determine whether dimensions are within specification or not, thereby reducing inspection times and potential errors. The data can also be saved for future use or to create reports at any time, increasing post-measurement work efficiency.
A variety of measurement systems and gages are available to inspect tooling. “We use an OGP Quest 600 vision measuring machine, a Leitz Model PMM-C 700 12-10-7 laboratory grade scanning CMM, and a Brown & Sharpe Global Advantage CMM,” said Allen. “The OGP machine uses analysis of magnified images of part details to accurately measure dimensions, angles, and radii without contact. The CMMs measure larger features via touch probing. Together, the systems provide the necessary measurements to confirm tool designs.”
Selecting the best tooling for orthopedic products and devices is dependent on a variety of parameters, including part size, type and thickness of material, complexity, finish, and cost per part. Of course, smaller, more complex orthopedic devices and components create tooling challenges, which are often solved using specialized or customized tooling.
Contract manufacturers must keep up with and invest in new and advanced tooling to meet ever-increasing customer demands for tight tolerances, quality, and speed. Although mastering new advances in technology is a must, so is having the knowledge, creativity, and savvy to combine existing technologies to push the edge of the technology envelope—where science starts to merge with “art” in making materials and equipment work together to achieve something that may have never been done before.
Technology continues to evolve with new devices, materials, and specific procedures. To keep pace, machine manufacturers offer improved cutting tool technologies, work-holding methods, and overall machine capabilities (many of which are Industry 4.0/Internet of Things (IoT)-enabled. For example, automation and robotics will drive rapid change in how orthopedic products are manufactured. Machine manufacturers continue to roll out advanced machines with greater functionality and intuitive, easy-to-use interfaces on a regular basis.
Software is another key part of Industry 4.0/IoT making great strides. For example, 2D and 3D simulation software can show angles, radii, and other key dimensions, which helps operators visualize the product and the process before they start machining. Machines can be fully connected with each other and integrated with enterprise resource planning (ERP) software, allowing real-time monitoring and decision-making. Robots on the shop floor are programmed to perform tasks, which frees employees to focus on higher-level work. Software can expand machine capabilities, improve quality, reduce cycle times, and speed up time to market, increasing productivity and profitability.
Perhaps the greatest benefit of IoT sensor networks and data analytics is being able to detect variance in machine operations in real time, allowing personnel to correct the variance before it becomes a serious problem that requires downtime to fix. For example, Tsugami/Rem Sales has partnered with Industrial IoT platform provider MachineMetrics to improve its customer service by resolving machine problems faster, without the necessity of an on-site visit. Reducing downtime, particularly unplanned downtime, is an essential part of keeping customer costs down and manufacturing levels up. “By IoT-enabling our new machines, our service managers and technicians can remotely monitor, manage, diagnose, and quickly resolve a customer’s machine issues for any piece of connected equipment in the field and in real time,” said Walker. The historical and real-time machine data that is collected provides insight into customers’ equipment performance, health, and condition, predicts and delivers early warning of potential equipment failures, highlights elevated risk areas that lead to machine downtime, and can even take preventative action before a potential problem impacts a customer’s machine performance.
These capabilities prevents thousands of dollars of equipment replacement costs and days of downtime for machine shops and enables more reliable 24/7 “lights out” manufacturing.
Industrial IoT is “all about data and knowledge,” noted Walker. “When it comes to staying ahead in very competitive industries, the only real leverage any company has is data. With it, we can find new ways to operate or add to our existing offerings, ensuring that we are satisfying not only our customers of today, but the customer of the future as well.”
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.