What Makes It Medical?
Making it in the medical market
By Robert B. Aronson
The medical market is one of the few areas of manufacturing that showed an increase in sales during the last recession and it continues to generate predictions of significant long-term gains. It’s no wonder so many companies from the Fortune 500 to job shops are now participating or at least looking for chances to be part of this market.
A sampling of present players shows three conditions under which companies are involved with the medical market. First are those that have long made medical products, such as Johnson and Johnson. Second, companies that have modified their existing equipment to meet some unique medical-product requirements. An example is those companies that changed or eliminated cutting fluids to meet unique sanitation requirements, or changed programming because of some complex part shape. Third are those situations where the supplier and user “discover” each other. For example, medical companies that needed high-precision metrology, or the surface finish provided by an EDM process.
Here are some additional examples.
Charmilles (Lincolnshire, IL) is offering equipment that matches all three categories. Their Robofil 240 cc “Turn while burn” system was developed after surgeons suggested a machine that could provide a finish only the EDM process could supply but also be able to make more complex shapes. Charmilles engineers achieved this by adding a servocontrolled B axis that rotated the part while the X and Y wire axes cut the complex shape. This machine can cut at the rate of 42 in.3/hr (688 cm3/hr). Key to the cutting speed is a new spark design in which the ignition voltage was increased from 400 to 1200 amp.
The application of the HSM 400 U five-axis unit was a case of manufacturers of dental implants “discovering” this machine cut titanium with the necessary precision in a single setup.
Finally the use of the UCP 600 Vario five-axis to make hip joints was a situation in which Charmilles engineers modified the software so the machine’s high-speed spindle could machine a complex hip shape.
Robots are becoming familiar tools in the medical industry in three areas: surgical operation procedures, part manufacture, and packaging. The first is a less developed area. Researchers are looking at situations where the robot might augment the surgeon in certain procedures requiring extreme stability and positioning accuracy.
In medical-part manufacture, robots are more widely accepted, chiefly in the finishing of larger parts such as hip and knee-joint elements. Initially, most of the burnishing and finishing was done manually. However, the cost and the need for greater precision are moving that task to robots. The cost is not only in labor, but the fact that with human workers, scrap rate is reportedly high.
Product handling is a rapidly growing area, according to Mark Handlesman of Fanuc Robotics Automation Inc. (Rochester Hills, MI). In one application robots load medication or instruments in shipping boxes. This is often linked to a tracking program that monitors the shipping operation.
The second robot application is in automated medication dispensing, which is now used in hospitals and pharmacies. Accuracy is the big driver in this situation, with minimizing labor a secondary benefit.
Grinding is often used as a finishing technique for medical parts. Though there are now exceptions, wheels are generally used for the less complex surfaces and belts for highly contoured parts. St. Gobain (Worcester, MA) has developed a number of products specifically for the medical market and many others that are an excellent fit for medical applications. They are chiefly used in the manufacture of prosthetic and orthopedic devices.
One of the more recent products is the Blaze R 980, SG grain, coated-abrasive belt. “For this product we basically engineered a new grain to fill a niche in the market,” explains Ed Reitz, senior corporate applications engineer. “It has a special backing for longer life, is free cutting and provides a faster cutting rate than previous products in the line.”
Free cutting is essential because these products are very heat sensitive, and heat causes metallurgical damage and distortion. This belt is generally used for roughing and preliminary shaping. It’s particularly good for working with investment castings.
St. Gobain engineers are also looking at the problems of sharpening cutting tools for the medical industry, both for initial manufacture and rework. The tools include dental drills, reamers, and bone rasps. “For this work we have a new XGP wheel that combines a new bond technology with high-performance abrasive,” says Reitz. “It’s particularly good for fluting and pointing, and offers a life up to ten times longer than that of previous wheels. It is cool cutting, provides higher tolerances, and greater burn reduction to limit metallurgical damage.”
Another key factor in the medical market is surface generation. It’s important to have a clean surface with minimal displacement. That is, it’s critical that metal not be moved once the initial finish is established. That can cover some defects that will cause problems later. This sometimes happens with burnishing. Another problem with burnishing is that it can generate distortion-causing heat.
St. Gobain has a superabrasive product called the G Force wheel. It works well with carbides, tool steels, and even stainless alloys and it reduces or eliminates wheel dressing. G Force wheels also eliminate burning and burrs in sensitive applications.
A coated abrasive belt called Norax has new designs linked to medical applications, the U243 flexible belt is for fine polishing and contouring, the U152 ×3 (3 µm grit size) belt which easily produces single digit Ra finishes, and the U442 ×40 and ×20, which is a silicon carbide abrasive belt utilized for titanium polishing.
The NL series of CNC lathes from Mori Seiki (Chicago) has a strong market with medical manufacturers, particularly in the production of replacement joints. Usually made of titanium or stainless steel, these parts require extreme accuracy and surface finish.
To ensure the necessary rigidity, the spindle motor is inside the turret and directly coupled to the milling tool. This reduces tool spindle acceleration time by 2/3 and diminishes vibration and noise by 1/2 compared to that generated in lathes that use a series of gears and belts in the spindle drive. This design also improves accuracy by reducing heat dissipated into the turret to 1/10 of that found in a conventional lathe’s milling function. The NL Series machine further reduces vibration because of its rigid internal support system.
Pill making is one of the most basic medical manufacturing activities, but the process can still be improved. Sunnen Products (St. Louis, MO) has a client that uses their honing equipment in the manufacture of medical tablets. The tolerance between the die and small pistons that compress the material. A Sunnen honing machine was able to provide the tight tolerances needed.
Tornos (Brookfield, CT) now offers machines that resolve a specific problem. Some of the newer orthopedic screw designs have single and/or double-lead threads with high pitch angles of up to 24°. Typically these high-pitch threads had to be manufactured as a secondary operation after blanking on a Swiss-style machine. This was due to a limitation in the pitch-angle adjustment on the thread-whirling attachment. To meet this new market demand, Tornos has a new thread-whirling device on its Deco series machines to produce high-angle bone screws in one setup. The device supports the part while it’s being whirled. This results in better accuracy, with burr-free results. These machines can handle bars 20 mm in diam (25.4-mm optional), and are offered with up to 12 axes (10 axes is standard). They have a 10,000-rpm spindle powered by a 5.5-kW motor.
As the accuracy of medical equipment improves, so does the need to provide measurements with greater precision. The increasing use of Heidenhain equipment on medical systems is a matter of the medical suppliers finding them. According to Kevin Kaufenberg, Heidenhain (Schaumburg, IL), “We have not had to modify our equipment for the medical market. But as those making medical equipment found the need for greater precision, they came to us. In one case, the resolvers on a radiation machine did not give the positioning accuracy needed for more precise targeting of the radiation. We replaced them with our absolute encoders. This gave a better correlation between the positioning of the radiation source and the patient’s body.
In another example of these applications, the Heidenhain LIDA 400 linear encoders, which have a 20 µm resolution, were used in a high-speed medical slide scanner that allows pathologists to create diagnostic-quality digital slides for anywhere, anytime viewing. Aperio Technologies Inc. (Vista, CA) manufactures this virtual microscopy system, the ScanScope Scanner. This instrument creates seamless and crisp true-color entire-slide scans free from artifacts and optical aberrations in minutes.
“We have not had to modify our products to meet the demands of the medical market,” explains Preben Hansen of Lyndex-Nikken Inc. (Mundelein, IL). Our standard products meet or exceed the high quality demands of the medical, aerospace, and die mold industries. Because medical products are often made from tougher materials such as Cobalt Chrome, Inconel, Incaloy, and stainless, the user has to be aware that the equipment has to be brought up a level above that needed for more conventional jobs. It’s not so much speed, but accuracy and rigidity, such as that offered by our VC Toolholder, that is the key to machining these materials. Lyndex-Nikken’s VC toolholder also offers vibration control and the added benefits of longer tool life and better surface finishes.
“Those new to the medical market often find that they need accessories, such as rotary tilt tables, to allow them to handle very complex shapes. They don’t need to invest in five-axis machines, when three axes and a rotary tilt table will do the job,” he concludes.
NTC America (Novi, MI) offers the Zu3500, a machine primed for the medical market. When working with precise small parts, even small deviations are unacceptable. This design boasts a noncontact slide system. That is, the combination of hydrodynamic and hydrostatic bearings means no contact between the moving bed and its support. For greater speed and precision, linear motors are used that offer 0.6-g acceleration.
In addition, the oil used is cooled, as is the cooling oil for the spindle, to minimize or eliminate runout.
It has travels of 350 mm in theX axis, 300 mm in Y, and 300 mm in Z. The 30,000-rpm, 25-hp (18.5-kW) spindle incorporates hydrostatic and hydrodynamic technologies that minimize wear and runout. The spindle is temperature-controlled and uses filtered hydrostatic oil. Footprint is 1300 × 2270 mm.
“Medical products are one of our fastest growing markets,” according to Mike Tibbet, senior development engineer, Kyocera Micro Tools(Irvine, CA) “We specialize in tools 1/4" and under, with about 70% of the tools less than 0.020" (0.5-mm) diam. Making a 0.010" (0.25-mm) diam hole is not an uncommon job. For example, we recently had a job in which 260,000 holes were made in a single plate used in a micromold of hardened stainless. These are not just scaled-down conventional cutting tools, but tools designed specifically for micro work.
“Medical manufacturing stresses the need for good surface finish and cutting-edge integrity. The harder materials can quickly ruin cutting tools, so we put a lot of work into our line of microtools, particularly with tool geometries and newer coatings.”
In conventional machining, the weight of the chip helps move the chip from the flutes of the tool. With micro holes, the “chip” is essentially weightless, so the chips tend to stick in the flutes, causing tool breakage. Materials used in medical devices, such as MP35, eat tools. As soon as it begins to loose its edge, the chip wraps around it and breaks the tool.
“There is a high demand for 0.0020 and 0.0030" (0.050–0.076-mm) drills. They are used for jobs such as drilling holes in medical instruments, which are made of 300 stainless.
“Burrs are a major no-no for the manufacturing of devices for the medical industry. We have developed cutters that won’t generate the burr in the first place, or will make them easy to remove,” he concludes.
“Fast turnaround of prototypes is the specialty of Small Parts Manufacturing Co. (Portland, OR). “You have to produce in five to ten days or you’re out,“ says Mert Rockney, Jr. president. “For us, a production order is 250–500 units, and they have to be made in three to four weeks. That is sometimes complicated by a need for special coating and packaging.”
“Materials may be a big issue. They define the processes we have to use. We work with such things as PEEK, an ether ketone polymer with a hardness of RC 40–50 and also centrifugally spun titanium. This metal is difficult to work with because it has no uniform grain structure. You can’t just drill and tap it. You have to drill, then bore, then mill the thread to achieve proper results.”
A lot of the newer projects involve stents—those little spring-like devices that are now commonly used to keep blood vessels open. In addition to the stents themselves, surgeons need a whole arsenal of specialized surgical tools to place and retain the stent.
Another challenge is that each job has to done in one operation. There is no second setup. “Normally, we begin with over-size bar stock, do all the precision cutting, then separate it from the stock as a final step,” Rockney explains. “For example, for a part 0.180–0.195" [4.6–5.0 mm] diam, we will start with 1/2 or 3/8" [13–9.5-mm] stock that supports the part until we make the required features with the live tooling.”
“Appearance and burrs are the big issues for the medical products we make,” Bill Woodrum, quality control manager, Pacific Precision (San Demos, CA). “Much of our work is not that high tolerance. Specifications of ±0.0001" [0.003 mm] are common.”
“Dental products are a strong market for us. These are chiefly the studs that are embedded in the jaw by the dentist, then capped.”
Record keeping is a major chore, involving both ISO and FDA regulations. A company has to be able to produce all relevant records on short notice, and surprise visits are not uncommon.
Lasers are another element in medical manufacturing because of their ability to cut and weld very small areas. The main goal in this work is to be able to work with ever smaller components while introducing a minimal amount of distortion-causing heat. One of the more recent entries in this field are the units from SPI Lasers (San Jose, CA). This is a diode-pumped, fiber-optic unit which is said to achieve a smaller beam focus and have greater stability than the YAG laser. Weld area is 40 µm. Another feature is a plug-and-play design. Set up and maintenance are minimal.
The SPI design claims up to 10 times more efficiency than Nd:YAG, little or no maintenance, small kerf width, and beam focus to less than 10 µm. The beam quality, small focus diameters and, therefore, small kerf width, makes these units a good tool for microcutting of miniature implants such as stents. It is now possible to laser-cut complex shapes in 2-mm OD tubes with walls as thin as 0.2 mm. It’s possible to make high-quality welds of medical components with a penetration of typically 0.5 mm or less. Average power required is usually less than 100 W.
Rego-Fix (Indianapolis, IN) offers a variety of products designed for small-part machining and the medical industry. Their powRgrip system uses a toolholder and collet which is said to generate clamping forces higher than shrink-fit holders and hydraulic chucks. These features can improve surface finishes and tool life when cutting complex materials. Run-out is 0.0001" (0.003 mm) or better.
To use the system, the tool is inserted in a collet, the collet is inserted in the toolholder. Then, the combined unit is placed in a press and the collet is clamped into the toolholder under 6 tons of force (53.4 kN). The process is reversed to remove the tool.
To reach deep pockets or to create complex shapes, a variety of extensions are available ranging from 120 to 200 mm in length.
The Medical Side of IBM
When a company wants to get a medical product to market, the problems are the same as with any other product:
- Time to market
- Integrating the production technology into the product’s design
- Establishing product differentiation. That is, what does this product offer that is unique?
Three years ago, IBM decided to take advantage of the growing medical market and set up a separate division to work with companies across a variety of industries—including medical—who had to solve these three problems. “We offer a diverse service,” says Joe Nemeth, vice president of Medical Solutions, IBM Technology Collaboration Solutions.
“It is more than counseling but less than turnkey. It depends on what the client needs. In particular, we help resolve the complex electronic problems that are common in many new medical devices and collaborate with our clients to engineer unique solutions customized for them and their clients.”
“One of the fastest growing areas is that of patient monitoring. This is both for the benefit of the patient, and to reduce medical office visits and hospital stays. IBM is particularly well suited to work with the complex programming that is a critical part of much new diagnostic equipment.
“We have a large portfolio of companies across industries where we see a future in working with them on potentially new products and solutions. They range from small companies to those in the Fortune 500, who may need help with getting an existing product to market or want to modify a product to meet a specific medical need.
- IBM’s manufacturing capabilities can do actual production in a partnership arrangement.
- When FDA certification is required, IBM works with the specific client to help supply the required tests and reports for their use.
Among IBM Technology Collaboration Solutions achievements in the medical field:
A collaboration between Technology Collaboration Solutions and Bang & Olufsen Medicom, has led to an enhanced Bluetooth-enabled dispenser device that helps patients on long-term drug therapy to continue taking their medication at the correct intervals. It’s known as “The Helping Hand.”
The Mayo Clinic developed a series of MRI devices called BC-10 MRI Coils to more easily diagnose injuries and diseases that affect wrists, forearms, elbows, hands and fingers. Mayo worked with a team of IBM engineers to optimize the functionality of the Coil for both the medical technician and the patient.
This article was first published in the May 2006 edition of Manufacturing Engineering magazine.