Originally Published EMDM January/February 2003
PRODUCT UPDATE
Metal Fabrication: Precision Has Its PriceInnovative materials and processes facilitate metal fabrication, helping industry to overcome issues of time and cost.
 |
| The manufacture of metal components is a complex and challenging process that requires a highly skilled and reliable workforce. |
When it comes to metal parts, customers dictate that smaller is better. But smaller also means more expensive and time-consuming. Although these are two continuous challenges facing metal fabricators, a variety of new materials and processes are helping companies keep their customers happy.
"Choosing the right material is the most important starting point for the development of any new medical device," says Clemens Meyer-Kobbe, president of Meko Laser Material Processing (Sarstedt, Germany). Such material properties as strength, fatigue resistance, break elongation, and biocompatibility have to be considered, he says.
For example, selection of a material for stent applications is dependent on various factors. "The levels of microcleanliness, structural homogeneity, biocompatibility, radiopacity, flexibility, expansion rate, strength, and compliance with recognized standards are all important," explains Brian Mercer, sales and marketing manager at Fine Tubes Ltd. (Plymouth, UK). For fracture nails, important factors include very high yield strength, resistance to corrosion and pitting, and machinability, he adds.
An array of metals is currently available to medical device manufacturers, including a range of grades of stainless steel, titanium, nitinol, cobalt-chromium alloys, and tantalum. "There is a growing trend to use more 'exotic' metals—titanium, nitinol, Hastalloy—for a variety of reasons, including nonmagnetic properties and shape memory," says Zev Asch, vice president of marketing and sales for Popper & Sons Inc. (New Hyde Park, NY, USA).
Nitinol's superelastic and shape-memory properties make it a popular choice for implantables. Stents made from nitinol can be bent to facilitate their manipulation within the body and then returned to a prescribed shape at a certain temperature. Stents can also be made using stainless steel, which offers good corrosion resistance, formability, and reasonable fatigue resistance.
Cobalt-chromium alloys, which exhibit corrosion and wear resistance, and titanium, which is durable and biocompatible, are popular choices for orthopaedic implants. Trabecular metal, which is similar to trabecular bone in structure, also has been used successfully in hip and knee replacements. Made of elemental tantalum, the biocompatible, durable, and corrosion-resistant metal has pore diameters of 430 µm and a porosity volume of 80%, which allow bone to grow into the implanted device.
The Creative Process
 |
| Customer demand for miniaturization is causing metal fabricators to produce some parts with tolerances on a submicron scale. |
"The improvement of the mechanical, chemical, and electrical properties of materials is an ongoing process," says Meyer-Kobbe. Over the past few years, new materials such as NiTi, L605, and Elgiloy (also know as Phynox) were introduced in medical applications, he reports. But the development of new materials requires a great amount of research and, as a result, time. There can be no shortcuts, as developers assume a high degree of responsibility when creating products intended for use in the human body.
Just as it is important to choose the most appropriate material, it is also necessary to determine the most suitable metalworking technology for a specific product. This can be a complex process as manufacturers need to ensure that their suppliers have the systems in place to form the desired material into the desired shape with excellent repeatability.
"Swiss machining plays a significant role in metal processing," says Jean-Claude Ziegler, chairman of Mikroland Innovations (Fillinges, France). The process, which involves turning, milling, drilling, and tapping functions, is used to make such products as dental tools and bone screws from stainless steel and titanium, among other materials.
Coil-fed Swiss machines, which rotate tools around a stationary length of continuously fed, self-straightening coil stock, are particularly useful for high-volume production runs that require good repeatability.
"The trend toward device miniaturization leads to the fact that the individual parts become smaller and more complicated in geometry," says Burkhard K. Rother, managing director of Kern Micro- und Feinwerktechnik GmbH & Co. KG (Murnau-Westried, Germany), a 40-year-old micromachining firm. "This often requires five-axis machining at very high spindle speeds."
Combining Swiss automatic machining with wire electrical-discharge machining or laser machining also allows the production of small, tight-tolerance parts.
Working with metals can be a time-consuming and expensive process. At the same time, competitive pressures are forcing customers to get new products to market faster than ever.
"Even during this time of economic slowdown—perhaps even more so—the demand upon metal fabricators is to produce parts quickly," says Tom Ney of the Metal Cutting Corp. (Cedar Grove, NJ, USA) sales department. With technology-based inventories kept at low levels, and product development going from concept to market rapidly, there is no time for production delays, he says. "These conditions, in concert with technological breakthroughs that specialize and miniaturize components, keep fabricators on their toes."
Satisfying Customers
Metal fabricators are feeling the pressure from their customers, and are reacting to it by expanding their capabilities and updating their equipment.
As Ney indicates, one of the greatest challenges to fabricators is micromachining metal components or devices. "There is a clear trend toward miniaturization," says Rother. "Clients are asking for smaller parts to be machined at tolerances that are becoming tighter and tighter, ideally within ±2 µm, and with excellent surface finishes," he says.
Customers also want more flexibility and the integration of single components into assemblies, says André Peyre, general manager of Société Études Développements (SED; Voutezac, France), which offers such capabilities.
"Our clients are asking us to manage their most critical programs by supplying value-added components and assemblies," says Bill Gaffney, vice president of marketing and international sales for UTI Corp. (Collegeville, PA, USA), which has facilities in Manchester, UK; Aura, Germany; and Galway, Ireland. "They are reducing their supplier bases, so companies with a wide range of capabilities and support services stand the best chance of increasing their market share," he concludes.
More Products:
Anthogyr
UTI Corp.
Monnier + Zahner AG
AMTellect Inc.
Popper & Sons Inc.
Metalor 2000
Metal Cutting Corp.
Fortimedix B.V.
Stork Veco B.V.
Cendres & Métaux S.A.
Kern Micro- und Feinwerktechnik GmbH & Co. KG
Meko Laser Material Processing
Mikroland Innovations
SED
Fine Tubes Ltd.
Remmele Engineering Inc., Micromachining Div.
Copyright ©2003 European Medical Device Manufacturer
