Not long ago, companies making devices for the medical industry pretty much had a blank check when it came to manufacturing processes for producing new products. With a growing customer base of aging and sickly people, companies building medical devices found themselves in a seller's market. The demand for products greatly exceeded competitive pressures in the marketplace, and it is perhaps only a mild exaggeration to say that the industry operated on a cost-is-no-object basis.

Today, it is a different story. Insurance companies, including Medicare, saw that the financial free-for-all had to end. So cost pressures now permeate the medical field as they do any other industry. Competition has also increased, as more firms want a piece of the lucrative medical market.

These pressures have had a two-fold effect. First, they have induced manufacturers and their suppliers to work harder on developing new processes that cut costs while equaling or exceeding quality standards. Second, companies are less and less willing to reveal exactly what kind of new manufacturing technologies they are using. If their manufacturing skill gives them an advantage in the marketplace, they want to keep it.

Any magazine article on manufacturing in the medical field thus will tend to be long on generalities and short on specifics. A firm, for example, might tell in principle what they are doing. But when it comes to revealing exactly what kind of parts are being produced, they are tight-lipped. Finally, non-disclosure agreements are becoming more common. Even if a custom fabricating shop is eager to take credit for being at the technological cutting edge, agreements with customers may prevent them from talking. Most secretive of all are the in-house fabricating shops operated by device manufacturers. If companies are still doing their own fabricating, the reason, at least partially, often has to do with the special proprietary skills they have developed. In such cases, they will only reluctantly reveal how they are manufacturing parts.

Take, for example, the extrusion of thermoplastics and the post-extrusion processing of reinforced tubing. One fabricating shop told me that the field has seen huge technological advances in on-line measurement and control, yielding, in turn, smaller, thinner, and more difficult to manufacture products. All this has resulted in more technologically-evolved devices made at lower cost with shorter lead times. In addition, the field has benefited from so-called crossover technologies from multidisciplinary teams.

When it comes to revealing specifics, however, the shop is prevented by its customers from doing so. Any cutting-edge technology is guarded by confidentiality agreements with customers. Also, as device manufacturers outsource more of their manufacturing, discussions and contracts over intellectual property get more detailed and intense. These non-disclosure agreements stay in force for years even if the products they apply to are unsuccessful and are discontinued. And when the details of a process are revealed, it generally is no longer cutting edge.

What is noteworthy about medical manufacturing today is much of the proprietary science being applied involves well-known industrial processes and relatively prosaic materials. Where the high-tech aspects come into play are in the complex shapes being generated, the almost microscopic details being formed, and the extraordinary accuracies being held. If you examined several of today's most advanced devices with the naked eye, you would see nothing exceptional about them. But it is the details not readily apparent that place these parts at the cutting edge of manufacturing technology.

Cost pressures are now being felt, surprisingly, in the market for orthopedic devices for such applications as hip and knee replacements. Prices for these devices have been increasing steadily approximately 5% annually. Hospitals have to buy these devices, but the demand is created by surgeons who implant them.

Surgeons, in turn, are sold on the devices by sales representatives of the manufacturers who, it is said, are often present in operating rooms as the devices are implanted. There has also been a certain amount of kickback involved in the pricing of implant devices. Surgeons who use a lot of them have often been the beneficiaries of lucrative “consulting arrangements” with the manufacturers as a reward for the business.

Complicating the situation is a certain amount of flimflam in prices practiced by manufacturers. This had made it difficult for hospitals to get honest market pricing. Today, hospitals are trying to break the cozy arrangements between manufacturers and doctors doing the implant work. It adds up to a better deal for patients and their insurance companies, but also more cost pressures on the manufacturers of implant devices.

The Lee Co.
Automation Keeps Costs in Check

Automation is the answer when parts are so small and are produced in such large volumes they are awkward and costly to handle. Examples are miniature fluid-control components manufactured by The Lee Co. The product line includes flow orifices, check valves, pressure relief valves, and safety screens. They are used in surgical kits, ambulatory devices, balloon devices, and oxygen conservers/concentrators.

Even though the parts are used in critical medical applications, they are used in such volume that cost pressures are more severe than typical for clinical instruments. Consequently, automation is applied throughout manufacturing including the production of individual parts, their assembly into devices, and subsequent testing.

For orifices, drilling and 100% flow testing (liquid and gas) are done with two separate operations on the same machine. Using automation eliminates most of the obstacles associated with flow testing orifices of this size and nature. The flow testing is critical in assuring the performance of these components as opposed to an orifice specified only by diameter. The flow testing takes into account all of the normal orifice shape variations, which affect discharge coefficient. Automation serves as an important component in the Lee Co.'s strategy towards lean manufacturing in high volume production, while controlling costs without sacrificing quality. This strategy lets the company alleviate constant human attention and have its workers oversee multiple operations. This hands-off approach also reduces the level of contamination often associated with handling of the parts to ensure that the cleanliness requirements for a medical-device component are achieved. A number of other fluid-control components are assembled in a similar manner.

Charmilles US
Wire EDM Is Like a Surgeon's Scalpel

If there are manufacturing frontiers being pushed in the medical field, the wire EDM process is one of them. The use of finer wires allows machining of smaller, more intricate, and more accurate parts than previously possible. Also improving the process are more advanced ways to control the electrical aspects of EDM units.

EDM (electrical discharge machining) is one of the more unusual of the many commercial machining processes. There are two types of EDM. In both, an electrically-charged electrode, usually graphite, is immersed in a dielectric fluid and brought near a grounded workpiece. Upon the approach to the workpiece, a spark from the electrode jumps the tiny gap, impacts the workpiece, and creates a miniscule amount of molten metal, which is carried away by the dielectric fluid. In the process, the spark impact leaves behind a small crater, which constitutes the metal removal.

Although each spark crater is miniscule, the sparks come in rapid succession, and each time they jump the smallest gap, which makes them impact the point on the workpiece nearest the electrode. The workpiece thus begins to assume a contour that is a “negative” or conforming fit to the shape of the electrode. If, for example, you are trying to form an impression in a die or mold, you machine an electrode with a contour which is the negative of the one you want in the mold. Then by means of EDM, you “sink” the electrode into the workpiece, thereby rendering it a mold or die.

This is the conventional, die-sinking, or “plunge” EDM process. Its relevance to producing medical parts is mainly through the generation of molds for producing plastic parts, although it can be used for making dies for metal-casting, stamping, or forging.

The other type of EDM, and one currently making the most waves at the frontiers of manufacturing parts for the medical industry, is wire EDM. It dispenses with the plunging electrode and instead uses a wire guided by two wire-guides, giving it a motion much like that of the blade in a bandsaw. It produces straight-line cuts much like those you would produce in cheese by using a wire slicer.

Initially, the wire or worktable in wire EDM was limited to X-Y numerical-control motions that were capable of producing only 2D profiles such as those of stamping or extrusion dies. Over the years, more axes have been added up to full five-axis capability. More recently, an additional axis of motion, the so-called B-A axis, has been introduced to wire EDM machines to produce what is called “turn and burn” for unusually complex shapes such as screw threads.

The question is why bother with a process so complicated when conventional machining also removes metal. The answer is EDM is not affected by the hardness of the workpiece. You can use the process to create tooling already in the hardened state, and you can also machine difficult-to-cut alloys or workpieces in a hard temper. In addition, both types of EDM can be held to exceedingly close tolerances and can produce shapes so intricate that they are difficult to produce by other means.

Currently, the main challenge for the producers of wire EDM equipment, according to Charmilles US, is in developing an ability to machine smaller and more accurate parts for the medical industry. For the production of such parts, Charmilles now uses smaller wires with EDM, down to a diameter of only 0.0008 in. These smaller wires also let shops produce more delicate parts and even so-called “microscopic” parts. Machined workpieces can now have wall thicknesses down to 0.001 in., and in some cases, even thinner.

The biggest recent development, according to Charmilles US, is higher cutting speeds. These speeds are now possible because of the development of what Charmilles calls a CC generator, where the CC stands for CleanCut. The company's equipment, for example, can now cut 42 in.²/hr in steel, a real-life, industrial cutting speed, not just a straight line cut. The previous top limit for speed was about 37 in.²/hr.

The Charmilles generator is a new approach to producing a spark, which, in turn, makes sharper shapes. The generator also brings up energy quickly, allowing better surfaces. This happens because of increased voltages and amperages in machine operation.

Another feature of the new CC generator is the clean surfaces it produces, a plus for medical components. It prevents the backplating normally found in EDM, where the wire replates to the workpiece. When this happens, the part must undergo expensive surface cleaning to get rid of the backplating. The CC technique is now widely used in the medical field for the absence of backplating, according to Charmilles officials.

Also of interest to medical designers is new wire EDM technology for machining titanium alloys. The CC generator prevents oxidation on titanium and keeps the surface free of brass and zinc that might be picked up from the cutting wire.

Another recent Charmilles development is the TW or twin-wire series. The machines can automatically switch between two wires. They, for example, change from a thick wire of, say, 0.013-in. diameter, typically used for aggressive cutting, to a thin wire in the range of 0.004 or even 0.0008 in., for producing delicate features or sharp internal corners. The automated twin-wire capability allows for the faster production of delicate parts.

The wire's metallurgy has a lot to do with the effective use of EDM. High-speed cutting or rough cuts require coated wire. The coating is, for example, zinc with a brass or copper core. For small wires, molybdenum or tungsten wire is used.