Changes Give a New Shape to Machining

Originally Published MDDI November 2002COVER STORY In today's machining arena, medical device firms are reaping a range of benefits, from lower prices to higher-quality parts.William Leventon

William Leventon

November 1, 2002

13 Min Read
Changes Give a New Shape to Machining

Originally Published MDDI November 2002


In today's machining arena, medical device firms are reaping a range of benefits, from lower prices to higher-quality parts.

William Leventon

If you look in the dictionary, you'll find that the definition of machining—"to cut, shape, or finish by machine"— hasn't changed. But that can't be said for much else about the subject. In recent years, machining materials, equipment, processes, and related services have all changed in important ways.

The changes were made to satisfy the constant demand for better and smaller products, faster turnaround times, and more contract services. In addition, machining firms have been forced to change in order to keep up with tough competitors both in the United States and abroad. Taken together, the changes are a boon for medical device firms that want more for their machining dollar.


In the area of materials, stainless steel has been toppled from its throne. For years, it was the preferred material for part machining, but new equipment and tooling capabilities have made titanium more popular among machining companies, according to Todd Oehlerking, program manager at MedSource Technologies Inc. (Minneapolis), a contract manufacturing firm that focuses on medical devices.

Among other things, titanium enables machines to drill small holes deeper than is possible with other materials. MedSource has drilled a 0.015-in.-diam hole 0.6 in. deep in a titanium part, Oehlerking says. "That's something that's usually not possible when you use any other material."

When customers want titanium parts, MedSource steers them to Grade 5, which "is much easier to machine than some of the other options," Oehlerking says. "It's an alloy that was optimized for machining requirements."

A finished part measuring 0.3 x 0.5 x 0.5 in., with three 0.013- in.-diam holes and two 0.030-in.-diam holes.

Another Choice is nitinol, which offers shape-memory characteristics that are becoming popular among medical designers. For example, a nitinol stent will contract to ease insertion into the body. Once in place, the stent will expand to its original shape to open an artery.

In part, nitinol's shape-memory characteristics are due to the material's high yield strength. But high yield strength also makes the material difficult to machine, says Oehlerking, whose company often works with nitinol in wire form. The material is also abrasive, he adds, making it hard on tooling.

Besides nitinol, MedSource is machining more nonmagnetic alloys than it has in the past. These alloys are used to make parts for surgical instruments that will be placed in or near MRI machines. The nonmagnetic materials won't interfere with the operation of the machines, says Bill Ellerkamp, MedSource's vice president of market development.


Alongside metals, ceramics play a crucial role in some medical devices. In laparoscopic electrosurgical instruments, for instance, ceramics such as alumina and zirconia serve as insulators to protect surgeons from the electric current running through the device. As Tim Haen, general manager of sales and marketing for the metals and assembly unit of CoorsTek (Golden, CO), explains, these ceramics are nonconductive materials that can withstand high temperatures.

According to Haen, zirconia is actually slightly more rigid than steel—a property that can be crucial during the machining process. "When you machine metal, sometimes it will move a little and you'll get variation in dimensions," he says. "But ceramics don't move on you."

On the other hand, ceramics are brittle materials that aren't suitable for very thin parts. In addition, tight-tolerance ceramic machining can be an expensive process. "The biggest issue is how much you want to pay for tight tolerances," Haen says. "In a lot of cases, we're holding 0.0005-in. tolerances for medical devices. But it can be cost-prohibitive."

Ceramics are well suited to insulation applications that require rigidity and high-temperature resistance. But when temperature and rigidity demands aren't as great, Haen says, manufacturers may want to consider plastic insulation materials such as PEI, LCP, and PEEK, which cost only a fraction as much as ceramics. During machining, however, plastics will move more than ceramics, making it more difficult to hold tight tolerances.

New plastic formulations can also replace metals in many medical devices. Mike Kartsonis, president of Dynamic Fabrication Inc. (Santa Ana, CA), a contract machining firm, says plastics are "getting stronger and lasting longer." Compared with metal, plastics "cut like butter," he says. "When you're cutting a hole in plastic, you can have the drill going three times as fast as it goes when you're drilling stainless [steel]." In addition, he says, plastics are less expensive than metals and may last as long.

Not all plastics last as long as metals, however—and that's just fine with some bone screw manufacturers, who are switching from metals to biodegradable copolymers. Bone screws made of these reinforced plastics dissolve in the body over time, so no surgical procedure is needed to remove them once they have served their purpose.

Polymer bone screws are usually made by multiaxis Swiss machines, says Al LaVezzi, president of LaVezzi Precision Inc. (Glendale Heights, IL), which machines many types of medical components. According to LaVezzi, plastic screws are becoming more popular, thanks to stronger new polymer grades.

On the downside, plastic bone screws are more expensive than their metal counterparts. They're also less stable, which can cause machining problems. "They'll shrink longitudinally, so it's kind of tough to put a tight tolerance on them," LaVezzi says.


This part was created using high-speed small-hole (0.013 in. diam) EDM and wire EDM.

Whatever the material, new equipment can machine it into parts faster than ever. "Five years ago, it might have taken 30 seconds to drill a hole in a piece of titanium," Kartsonis says. "Now, with high-speed spindles, it takes half that time."

New machines are also more versatile than their predecessors. At UMC Inc. (Hamel, MN), for instance, parts that once required five different milling and turning procedures are now made by one machine in a single operation. This boosts throughput, cuts costs, and produces tighter-tolerance parts, according to Don Tomann, vice president of UMC.

Among other things, a rising demand for tighter tolerances has led to improvements in machine control systems. In early CNC machines, rotary shaft encoders equated a certain number of shaft revolutions with a certain amount of machine movement. For example, an encoder might have operated on the assumption that four shaft revolutions equaled an inch of motion. But if the shaft became worn, four revolutions might no longer produce an inch of movement.

Therefore, new machine designs include glass scales that use sensors to check machine motion. "The sensor is taking an actual reading of the distance moved," LaVezzi says. "This is much more accurate than the old method."

With accuracy more important than ever, firms like LaVezzi Precision also must find ways to minimize the effects of heat on machine tools. "You don't want heat to build up in the spindle," LaVezzi says. "Heat causes expansion, and expansion causes distortion in the machine axes."

To beat the heat, fluid-flow systems circulate coolants through the machines. In addition, equipment manufacturers now use concrete and a variety of composite materials that transfer heat more slowly than steel for machine beds.

Accuracy also gets a boost from more rigid machines. So machine manufacturers are adding rigidity to components such as the workpiece, spindle, and cutting tool. "If you've got rigidity, you can put in a hole much faster, deeper, and straighter," LaVezzi says.


Xact Wire EDM Corp.'s facilities in Waukesha, WI. The company's headquarters, pictured here, are designed specifically for wire electrical-discharge machining.

With medical parts getting ever smaller, some manufacturers are turning to wire electrical-discharge machines (EDM). At Xact Wire EDM Corp. (Waukesha, WI), machines feature cutting wires with diameters as small as 0.004 in. These tiny wires don't subject parts to cutting forces, making wire EDM suitable for machining fragile parts such as thin-walled tubes, according to Jeff Gubbins, co-owner of Xact.

To prevent cutter wear, fresh wire is continuously fed into the machine. This results in a consistent, repeatable machining process, Gubbins says. The process also produces parts with burr-free finishes.

According to Gubbins, new wire EDM units feature faster cutting speeds than their predecessors. In addition, the new machines can automatically switch from one wire size to another in the middle of a job. So after a large wire quickly cuts the basic part features, the machine can switch to a small, slower-cutting wire to produce fine details.

As holes and other part features shrink, Oehlerking expects laser machining to become more popular. Today, lasers are used to cut through-holes in medical parts such as stents and tubing. Soon, however, manufacturers may be able to control the depth of laser cutting, which would let them produce features such as blind holes. "That [capability is] going to be pretty revolutionary once it's figured out," Oehlerking says.


Precision skim-cutting of 0.010-in.-wide slots using 0.006-in.-diam wire.

New machines are turning out multifaceted parts that can be extremely difficult to inspect. So LaVezzi Precision relies on high-tech inspection tools such as multiaxis coordinate-measuring machines. These machines feature rotating dynamic heads that can pivot at any angle to check unusual holes and other tough-to-inspect features.

Machining firms are also turning to computerized optical inspection systems. These automated processes save time and reduce labor requirements, Oehlerking says. What's more, he adds, they can be a necessity when inspecting small parts: "In many cases, the parts we're making are so small that you could damage them if you took a measurement with a standard micrometer."

At Xact, the most accurate video inspection system has 0.1-µm scales and can magnify part features more than 300 times. The video system can rapidly check the locations of thousands of points, according to Gubbins.

Capable as they are, Haen believes inspection systems may soon be overtaxed by demands for ever-tighter tolerances. "I think we're getting to the limits of inspection machinery," he says. "At this point, you have to use light bands in some of your measuring techniques. That requires very capital-intensive equipment. And even with that equipment, you might not be able to repeatably inspect what the designers are asking for."

Besides inspection, automation is taking over some finishing processes. MedSource uses robotic systems to deburr parts and produce the required surface finishes. By taking the human element out of the finishing process, these robotic systems give the company more control over process parameters. But the costly systems are only used in high-volume operations. "We can't buy a robot when we're only going to manufacture 10,000 or 20,000 components," Oehlerking says.


The machining of additional features on the part at left after a 90º rotation.

Changes in machining equipment have been matched by changes in the industry itself. For example, many medical device companies have reduced the size and increased the frequency of part orders placed with contract machining firms. This lets medical companies make design changes without saddling themselves with large quantities of obsolete parts, Gubbins explains.

Medical firms are also placing orders that call for more incremental deliveries. "Five years ago, they might have taken an order for 5000 implants in two 2500-piece lots over 60 days," recalls Bill Heath, director of sales and marketing for Jeropa Swiss Precision Inc. (Escondido, CA), a contract machining firm. "But now, they might want five 1000-piece lots over 5 months."

For medical device companies, there are several advantages to this method of ordering. They get a price break because of the size of the total order, but they don't pay the contractor until after the units are shipped. In addition, this arrangement forces the contractor to carry the inventory burden during the contract period. "To serve the customer, we're carrying more inventory, on a percentage basis, than we ever have," Heath says.

Though outsourcing to firms like Jeropa is increasing, many medical device companies are reducing their vendor count. One MedSource customer found that it was dealing with 4000 different vendors. To cut administrative costs, the company decided to slash that number to 100. Other large firms are making reductions on a similar scale, Ellerkamp reports.

To cut costs, many medical device companies are working with foreign outsourcing partners. What do they get from machining outfits in Mexico or China? "I've seen a lot of junk," LaVezzi says. "But I've also seen some very good products. And you certainly can't knock the price."

When it comes to machining commodity products, medical device firms "are just looking for the cheapest source of labor. So cheaper stuff has been going overseas," LaVezzi says. "But the more complex, high-end parts stay here."

But for how long? Foreign operations "don't have high-end tooling and automation technology yet," Kartsonis says, "but they're gaining all the time." In fact, he adds, U.S. firms are transferring machining expertise to plants they're operating in other countries.


Since foreign machining companies charge rock-bottom prices, U.S.-based firms have been forced to find lures other than price to attract and retain customers. "We can bring a lot more to the table than just the parts themselves," says Keith Metzger, sales manager for Micro Med Machining (Miramar, FL), which offers extras such as engineering services.

Some U.S. contractors deal with foreign competitors by not playing in their ballpark. "We focus mostly on small- and medium-sized runs," says Jean-Louis Paroz, CEO of Jeropa Swiss Precision. "The foreign [contractors] want to see volume."

To trump foreign competition, CoorsTek combines parts into assemblies for its customers. The firm separates the parts in these assemblies into two categories: critical parts and commodity parts. Critical parts with tight tolerances are machined at the company's U.S. facilities, while commodity part production is subcontracted to low-cost foreign suppliers.

Is it only a matter of time before foreign outfits are machining complex parts as well? "I don't know if it's inevitable," Haen says. "As products get tougher [to make], medical device designers want to work with local people."

Proximity to a contractor can also reduce turnaround time. If customers need something quickly, Kartsonis says, "we can get it done because we're right in their backyard."


In recent years, change has come to virtually every aspect of machining. Materials, equipment, and processes have improved to satisfy demanding medical device firms. In addition, contract manufacturing companies are offering new services and special deals in an effort to survive in an intensely competitive industry. As a result, their customers are getting more for less, and getting it faster than ever before. Says Kartsonis, "That's what everybody expects now."

William Leventon is a freelance writer living in New Jersey and a frequent contributor to MD&DI.

Copyright ©2002 Medical Device & Diagnostic Industry

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