New designs, technologies, and materials in the manufacture of medical devices, appliances, and tools has increased the need for precision workholding devices that can meet stringent product quality standards and increased production capabilities.
“The medical industry presents unique challenges for manufacturing,” says James F. Woods, president of Hainbuch America, North American distributor for Germany’s Hainbuch GmbH. “The combination of requirements – high degrees of precision and surface finish with a wide proliferation of part geometry in sophisticated materials – demand workholding that is not only precise and rigid but allows for efficient and accurate changeover. Because even the newest machines often come equipped with conventional chucks, it is necessary for manufacturers to source higher quality workholding equipment capable of meeting their present and future operational needs.”
Highly specialized medical applications have redefined accuracy and precision. In conventional machining, these have traditionally referred to the ability to hold tight tolerances. Modern requirements are often involved with other factors as well. Components demanding a high finish are typically moved from turning or machining centers to specialized grinding or polishing machines. Today, this is less than practical for many reasons, including the fact that moving workpieces between machines risks inaccurate positioning. Multiple machine operations are also more expensive because of equipment costs, tooling, and the time involved in making the transfers. With precision workholding equipment and high-performance tooling, it is possible to complete first-pass machining and finishing operations in the same setup – an increasingly important flexible workholding consideration, especially for orthopedic devices.
Pete Peterson, national sales manager for Germantown, Wisconsin-based Hainbuch America, explains, “Whatever the application, we emphasize how important it is to partner with a supplier offering quick-change capability for multiple-size clamping heads (collets), combined with the ability to handle both ID and OD machining. We recently assisted a plant producing joint cups that involved multiple machine operations. By reducing their changeover time for various sizes, they maintained high levels of precision while increasing production by more than 40%. This not only resulted in a more streamlined operation, but enabled them to seek additional business.”
The owner of a medium-sized shop that produces bone pins and surgical tooling explains, “When we went over to precision workholding equipment on all our machines, we incurred an expense both in terms of initial outlay as well as training. We knew that it might not be necessary for every job but, by being equipped, we’re prepared for whatever our customers engineer next. It’s also enabled us to bid more work. If you’re going to stay competitive in this business, it’s something that you have to do – the sooner the better.”
The highly competitive nature of medical manufacturing also has redefined the concepts of economics and competitive advantage. This has created a management model that places as great a value on preparedness as it does on meeting present-day challenges, making the flexibility of their workholding system paramount.
In 1996, Matt Saccomanno, co-founder of Masa Tool, was frustrated with the limitations of conventional collets and workholding systems when performing secondary machining operations as engineering manager at Allied Swiss Screw Products. This was in the early days of CNC Swiss-type machines, when machining capabilities were limited, requiring lots of secondary operations. His solution – a high-precision, collet-type workholding device for small parts machining.
As machining capabilities advanced and precision requirements became more challenging, Saccomanno realized that the legacy collet systems used in micro-machining were a serious limiting factor that prevented full use of modern machine capabilities. That prompted Saccomanno to design the next generation, the Microconic system.
Cartridge & collet
“The Microconic system consists of a cartridge and collet, with the cartridge fitting in the machine just like a standard legacy collet,” Saccomanno says. “The cartridge, a self-contained precision mechanism using the machine’s standard collet closing function, brings Microconic features to any machine.”
Cartridges fit an expanding range of machines, and are currently available for those using TF20, TF25, or 5C collets. Microconic UM10 collets fit into the cartridge to hold the workpiece and because of the design and closing action, it is inherently more accurate and consistent than traditional collets.
“The origin of the word Microconic alludes to the precise way in which the collet closing taper is formed to cancel the effects of heat-treat warp and grind tolerances, providing concentricity every time,” Saccomanno explains. “There are two basic types of Microconic collets – standard and over-grip, and both types fit in any of our cartridges. Our over-grip collets deliver rigidity, concentricity, and the ability to open 4mm (0.156") larger than the gripping diameter.”
Explaining that the patented design of the system enables the improved over-gripping performance, Saccomanno notes – from his own experience – that this is impossible to do in a legacy collet system alone.
Included with the over-grip collet is an ejection guide sleeve blank for ejecting the part from the collet – an often challenging task because the larger head of the part inside the collet can get stuck if not securely guided out when opening.
Saccomanno says the system alleviates challenges machinists face when setting up for small part machining by addressing the limitations of legacy collet systems.
“Collet-type workholding has a history of being the best method to hold small workpieces in production situations, because of rapid closing action, high clamping force, rigidity, and accuracy. To grip various workpieces of different diameters, a specifically sized collet is pre-made to match the gripping diameter,” Saccomanno says. “The exterior size and shape of the collet does not change, only the internal diameter of the gripping surface. So, a collet system for any given machine must be made large enough to fit the maximum workpiece diameter capacity of the machine. The result is the collet mechanism is designed to handle the largest workpieces, which means it is excessively forceful and bulky when used for the smaller workpieces. Smaller parts get sacrificed, because they typically require a higher degree of accuracy and the workholding is more critical.”
Prescott explains that there are three ways the Microconic cartridge optimizes machines for small parts.
Precision control – The cartridge provides complete internal control of collet closure, regardless of how forceful the machine’s mechanism is. Micrometer-graduated adjustment of the precise amount of collet closure, set with the MicroGrad wrench, allows even the most fragile parts to be held securely and without damage. The closure setting can be recorded on the set-up plan and accurately repeated without relying on the feel or experience of the machinist.
Improved part access – With small parts reaching the part with small cutting tools can be difficult due to interference with relatively large spindle noses. Legacy systems often use an extended nose collet to give adequate clearances, causing problems with lack of concentricity while the flexing of the long collet jaws leads to poor rigidity and holding power. Machinists then apply more force to grip the part securely, which can cause part damage. Also, with increasing force comes increasing flex, so the collet jaws start to flare outward, causing less gripping strength at the end where the cutting force is happening. High-force machining operations, such as blind hole broaching, can’t be performed because the part slips and pushes back in the collet. With Microconic, the solid extended nose of the cartridge applies the closing force directly over the workpiece. Maximum rigidity is achieved, so the part can be held securely without too much force, allowing operations that legacy collets can’t perform.
Rapid setup – The collet can be changed and adjusted entirely from the front of the spindle nose. Also, the concentricity and rigidity means no troubleshooting or swapping of collets to find one that runs true. It is guaranteed that the system will not add more than 0.0002" (5µm) total indicated runout.
When making the change to the system, machinists will remove the legacy collet (and spring, if any), and install the Microconic cartridge the same way a legacy collet would be installed. The Microconic collets then thread in from the front of the cartridge, which makes collet changing easier.
When the cartridge is first installed, the machinist should use a dial test indicator to measure the runout of the cartridge nose, which is ground to gage-like tolerances.
“If there is any runout, it is a result of the machine spindle condition and should be diagnosed as required. Usually this just involves a very thorough cleaning of the seating surfaces, but may also be due to production wear or damage,” Prescott notes. “The key here is that concentricity issues can be properly diagnosed and corrected right away, without having to run parts or try multiple collets. Once corrected, concentricity will be good every time, saving hours of troubleshooting during future setups.”
Masa Tool Inc.
About the author: Elizabeth Modic is the editor of Today’s Medical Developments and can be reached at email@example.com or 216.393.0264.
Silicon dioxide, or silica, is one of the most fundamental elements on earth. Most commonly found in nature as quartz, it is the major constituent of sand and a primary component in silicone and glass. Now, this basic chemical compound is being applied using plasma-enhanced chemical vapor deposition (PECVD) techniques as an anti-microbial barrier, a primer to promote adhesion between stainless steel and proprietary coatings, or to create hydrophobic or hydrophilic surfaces.
For many medical device manufacturers, proprietary coatings and surface treatments can play a significant role in product development and upgrading legacy medical devices under 510(k) guidelines. As a result, the medical device industry is aggressively investigating and applying plasma-applied coatings to products such as stainless steel guide wires, catheters, stents, and vascular surgical tools.
“We are always looking for unique and novel ways to make our products more robust and become the market leader, but to do that we need to bring more technology to our devices. Often, that is going to involve some form of coating to functionalize the surface,” explains Aaron Baldwin R&D project group leaders at MicroVention, a company that offers neuro-interventional products including access products, intraluminal stents, occlusion balloons, and polymer coils.
“PECVD can take a product to the next level by addressing surface reaction issues such as biocompatibility or lubricity. It is a unique and eloquent way to deposit and enhance coatings because it allows you to tailor the surface while retaining the bulk material’s properties you need.”
Organic silicon PECVD
The PECVD process deposits thin films from a gas state (vapor) to a solid state on a substrate. PECVD deposition of silicon dioxide often requires organic silicons are as the feedstock. Within this family, the best known are hexamethyldisiloxane (HMDSO) and tetramethyldisiloxane (TMDSO).
HMDSO is an affordable, flexible reagent that is commercially available in a high purity, liquid form. The volatile, colorless liquid can be plasma-polymerized to create a variety of surface coatings that are safe for medical use. Depending on the composition of oxygen to HMDSO, the property of the surface can be hydrophobic or hydrophilic.
This flexibility makes HMDSO and other siloxanes the ideal choice for PECVD. By adjusting the parameters and other gasses added, chemists can tightly control the material to address a wide range of applications.
Fine-tuning PECVD chemistry
Despite the flexibility of PECVD- applied organic silicons, developing the precise chemistries, added gases, and plasma equipment design requires a close, collaborative relationship between medical device designers and equipment manufacturers.
Because MicroVention already had an established relationship with PVA TePla – several of its plasma chambers were already being used to aide in coating adhesion – Baldwin began consulting with them on a project to determine the benefits of coatings for stents.
Plasma equipment manufacturers fall into two categories, Baldwin says, those that produce commodity, off-the-shelf products and those that design and engineer systems to fit the needs of a specific application and/or to resolve unique surface energy challenges. So, when companies present PVA TePla with a challenging surface chemistry problem they are encouraged to visit the lab in Corona, California, giving them an opportunity to brainstorm with their technical team and run experiments together.
Many of the best experimental matrices and ideas are produced during these technical customer/supplier meetings. In addition to designing and manufacturing plasma systems, the company also serves as a contract manufacturer and has in-house equipment needed to run parts and conduct experiments with full customer involvement.
“When we start on something new, instead of poking around in the dark, it is better to get expertise involved and [PVA TePla] is very willing to do experimentations – often free of charge – to get the project moving and improve the characteristics of the system and chemistries involved,” Baldwin says. “We were able to go there and work on their plasma machines to determine our parameters and evaluate the equipment.”
Every PVA TePla system is designed to meet the application requirements, which can include unique fixtures, unique electrodes, and chamber modification to accommodate throughput and coating uniformity.
The ability to thoroughly clean the chamber after each application of organic silicons is a major consideration as it coats the entire interior of the chamber (including the electrodes) in addition to the products receiving the coating. As a result, PVA TePla modifies the chamber to make it easier for the user to clean it after every coating application.
Connecting machinery to computer and communications can boost productivity by offering insights into operations. Eric Fogg, co-founder and COO at software provider MachineMetrics identified these critical benefits in an interview with Today’s Medical Developments.
1. What are the risks when a company connects machine tools for monitoring?
Fogg: Connecting equipment for monitoring can present a security risk when not done correctly, however doing so securely does not have to be expensive. MachineMetrics has worked and consulted with information technology (IT) security experts to make sure our system is safe.
2. What are the benefits when connecting machine tools for monitoring; how does that outweigh the risks?
Fogg: Those that connect to machine monitoring are increasing production by making better decisions driven by data, enabling better, real-time communication between management and the shop floor.
3. What are some hesitations heard when considering implementation of a machine monitoring system?
Fogg: Security is usually the top concern. After that, customers worry if they are ready to handle all the data and if they have the time and staff to act on it.
4. What steps should a machine shop take in order to protect equipment it plans to monitor?
Fogg: Since we pull data directly from machine controls, and our system is cloud based, all computers in the plant are separate from the monitoring system. Though it’s good practice to keep up with updates, password protection, etc., it has no impact on the security of MachineMetrics. All a shop has to do is run network cables to each machine (wireless is available as well) and MachineMetrics takes it from there.
5. How do machine monitoring, dashboards and data transparency save money, increase competitiveness, and improve employee morale?
Fogg: The transparency of the system allows companies to acutely understand problems, bringing problems to the surface much quicker than before.
MachineMetrics increases machine utilization by 15% to 25% in most shops by allowing customers to understand how well their investments are working for them and where they should be investing further.
Employees can be approached about problems within minutes or hours of an event, not the end of the day or week when the problem is inflated. This turns the conversation between management and employees from frustrated or angry when a job is late to more helpful when the problem has just occurred and can be worked through for improvements.
With setup times varying by operator and shift, job changeovers are the biggest source of lost production time for a business. Using monitoring systems enables a business to track setup time by incorporating it into the workflow when dispatching jobs.
The software’s Operator View allows operators to start and stop jobs, categorize downtime, and reject parts for quality assurance. Operators also gain confidence that supervisors are going to address problems proactively and involve them in the process, and supervisors gain confidence that their employees are engaged.
6. What have machine tool companies responses been when job shop owners realize they don’t need to invest in more equipment once they have data and have learned how to improve production with current machines?
Fogg: Machine tool companies like machine monitoring software because they know that their customers’ success and profit is good for them in the long haul when equipment performs up to stated specifications or better.
7. What is the minimum improvement a shop can expect to see once implemented?
Fogg: We usually see a minimum of 10% increase in productivity as well as more confidence in quoting and capital expenditure decisions. Information such as cycle times, performance, number of parts produced, rejects, downtime reasons, and reject reasons can be collected for each part operation. This information allows managers to quickly identify issues related to specific operations and measure the effectiveness of process improvements.
8. How is MachineMetrics set apart from market competitors?
Fogg: We are focused on building simple software that focuses on providing a human context to data, something no one else is currently doing. In addition, by being cloud based, our software is dynamic with new features and updates weekly.
About the author: Elizabeth Engler Modic is editor of Today’s Medical Developments and can be reached at firstname.lastname@example.org.