Laser surface texturing is a novel method for applying custom textures to metals, ceramics and polymers. Photo courtesy of Mound Laser & Photonics Center.

Tempo Drives Technology – Speed to Market More Vital

Machining and laser processing shops must scramble to do more with less on tighter deadlines

Frank Celia, Contributing Writer

In the world of medical device machining, the most expensive thing you can do is move a part from one machine to another. It eats up time, adds labor costs and, more than that, lowers quality, making tolerance goals tougher to meet and increasing the risk of an accident that could damage a part on which a great deal of money, time and expertise have been lavished.

Hence the trend in orthopedic machining shops of purchasing units that can perform more than one task without removing the part—milling and turning in one step, for instance, or being able to work along additional axes. The downside of this trend is the expense. Machines that perform more than one task are extraordinarily costly—sometimes more than double the price of mainstay devices—and finding qualified operators to run them is no easy task.

Increasingly, industry experts are predicting laser processing will step in and play a bigger role, helping to streamline and simplify manufacturing procedures—which are coming under ever-tighter deadlines from OEMs. This is occurring not so much in heavy-duty metalworking on implants as it is with orthopedic surgical instruments. For example, laser welding can fuse two parts together without adding additional material to a joint, as is the case with conventional welding. On implants, laser processing continues to make headway in more tangential areas, such as using lasers to imprint lot numbers and company logos on components.

Machining Needs

Sturdiness and durability are always valued in any medical device, but perhaps this is even more important in orthopedics, especially since implants are designed to replace human bone structure. “Twenty years ago, there was a general feeling in orthopedics: ‘In force we trust,’” said Peter J. Randall, vice president of sales at Easton, MA-based Holmed Corp., which manufactures surgical instruments. “We liked heavy-duty things that you could really put pressure on. Today, the push is toward smaller, lighter-weight instrumentation—minimally invasive instruments that allow surgeons to work through much smaller incisions. They cause less trauma and allow the patient to get up and moving faster.”

While the needs of orthopedic surgeons have changed drastically in the last 20 years, the human body has not. “There are still certain pressures required to drill a screw into a bone, and the instrumentation still has to withstand certain torques or pressure requirements,” explained Randall, “and yet we are doing this with lighter instruments through a smaller incision. It’s a challenge.”

Medical device coatings have been NAMSA tested for biocompatibility and are ISO 10993 compliant. Photo courtesy of Electrolizing Corp. of OHIO.

In addition, speed-to-market issues continue to put pressure on manufacturers. Spurred by predictions of a burgeoning orthopedics market, many firms are rushing to get their products to the market before their competition beats them to it and captures market share. Thus, a universal complaint among those who work in machine shops is the challenge of product turnaround.

One way to save time is to perform more than one operation at once. “The niche we have is, in addition to tight tolerances, we are able to do milling within our Swiss turning centers,” said Dan Stefano, general manager of micro-machining at Norman Noble, Inc. of Cleveland, OH. “This is very unique and capable equipment that allows us to do all our machining within one complete setup. This process optimizes efficiencies while maintaining world caliber quality standards.”

Holmed also uses multi-tasking machines. One TMC multi-turning center has double turrets that enable the working on a part at two different directions at the same time. The benefits come at a high price, though.

“The problem with these types of machines is that they are very costly, especially if your volumes are not very high,” said Randall. “And many companies are not willing to commit to the type of volumes that they used to. They would rather pay a little extra per unit.”

A fifth axis machining of an aluminum instrument. Photo courtesy of Medicine Lodge.

Rather than order hefty volumes, some larger companies are starting to supply vendors like Holmed with forecasting predictions that they once kept to themselves, hoping the vendor will invest in technology that can be used at some point in the future. “They want us to anticipate their needs and help reduce lead times, and it gives us a chance—depending on the product and who the customer is—to take a gamble,” Randall explained.

Keeping up with the latest machining technology is not easy, but it is worth it, said Stefano. All of the machines on Norman Noble’s factory floor are less than two years old. “Our success has generated the capital to continue to grow along with our customers,” he said. “As they grow, they don’t have to go to multiple contract manufacturers because we can grow with them.” Recently, for example, the company purchased an additional 120,000 square feet of factory space.

At MedicineLodge, a contract manufacturer based in Logan, UT, company officials have recently invested in multi-tasking machining device called an Integrex, which allows for five-axis control multi-face machining. “This allows us to build most parts in one piece,” said Peter Goble, sales and marketing manager. “This means fewer setups, so we can return quicker lead times to our customers.”

Coatings Add Ease

Like manufacturers, surgeons are under increased time pressure. Part of how they streamline their operations is by keeping their operating rooms organized and easy to use. Color-coated instruments and implants are important because they increase a surgeon’s ability to perform quickly and precisely and minimize mistakes (color coating also reduces errors in assembly). This sounds like a simple idea until you realize that slapping a coat of red paint on a spinal screw designed to stay inside a body for 30 years is not a viable option. That is why many shops need to be familiar with titanium anodizing.
Anodizing hardens and colorizes the surface of titanium components without altering the surface properties of the metal. It accomplishes this by adjusting oxide levels, changing the spectrum of light reflected from the metal, resulting in a perceived color. Technically speaking, this process is not a “coating” at all because nothing is actually applied to the surface—ie, no dyes or paints are used. Instead, the molecular structure of the metal is changed without affecting the integrity and properties of the material nor its suitability in biomedical applications.

The Electrolizing Corp. of Ohio, based in Cleveland, is known as a top-notch provider of this service, as well as other coatings. The company has developed several proprietary coatings ranging from performance coatings to aesthetic coatings for the orthopedic industry. Many of these coatings have been NAMSA tested for biocompatility and are ISO 10993 compliant. A large portion of Electrolizing’s business is in the orthopedic industry, according to Raymond M. Harris, director of sales. Many of the coatings can solve problems in the orthopedic device industry, he said. Some can provide corrosion resistance, others wear resistance or lubricity. Some colors are added purely for aesthetic reasons, he noted.

Lasers Gain Ground

When it comes to lasers being used to cut and weld large metalworking jobs, orthopedics does not seem to be the field of choice at first glance. Norman Noble, known as the largest laser micromachining facility in the world, does very little laser cutting on orthopedic implant devices. “Requests from orthopedics companies tend to be milling and turning,” said Stefano. “Typically when we use a laser it is for tubular or flat work, and that really doesn’t have much application for orthopedic jobs.”

Virtually all laser work done on orthopedic devices in his shop involves marking parts with lot numbers or company logos. This is an important step because permanent markings on medical products provide important tracking capabilities for warranty, replacement and legal liability.

Over the years a variety of methods have been used to mark medical devices: electro-chemical etching, pin stamping, mechanical stamping, ink and labels.

In addition to laser marking, electro-chemical etching is currently a popular method of marking devices. Many in the industry view laser marking as a better choice, though. Electro-chemical etching marks the metallic substrate using a corrosive electrolytic solution combined with electricity. During the process, parts of the device not meant to be marked must be covered to ensure they are not affected by the chemicals. The downside is that the chemicals involved are not usually environmentally friendly and the mark provided by electro-chemical etching is not as well defined as that produced by a laser. Also, because electro-chemical etching involves an aggressive chemical reaction, it carries a potential risk as an initiation site for future corrosion.

Because laser marking does not require the steps involving the addition of chemicals, it usually can be done more quickly. Further, because the laser marking process is completely non-contact, it is easily automated and repeatable. Proponents of laser marking say it is more flexible regarding the images that can be produced. Virtually any image file or alpha-numeric character set can be laser-marked onto a part, including company logos, part numbers and even one- and two-dimensional bar codes.

Another laser application gaining ground in the orthopedics market is laser welding, which is most often used in machining surgical instruments. Laser welding has been around for more than 30 years but is gaining popularity now because it excels at joining parts that are extremely small—and medical components keep getting smaller every day. Mainstay welding processes such as gas-tungsten arc welding (GTAW) and plasma arc welding (PAW) have gone about as far as they can in terms of their ability to assist in micro-fabrication.

Laser welding is ideal for small parts because of its ability to deliver very precise amounts of energy. Also, because no filler material is added and the process is performed under an inert atmosphere, the weld is often indistinguishable from the base material. It can be used on most joint configurations and on most metals, including carbon steel, stainless steel, aluminum, titanium and nickel.

One company at the forefront of laser technology is Mound Laser & Photonics Center, Inc., based in Miamisburg, OH. For the past three years, the company has been exploring various areas of material surface modification using lasers in orthopedic implant devices, according to Kevin Hartke, manager of sales and marketing (see sidebar, “Federal Government Helps Finance New Technology,” to learn more about how companies such as Mound Laser are strengthening technology offerings via government funds).

“Surface textures are being explored in two areas. One is improved bone adhesion and the other is reduced wear on the surface of the implant,” Hartke said. The custom textures can be applied to metals (titanium, tungsten, stainless steel, aluminum, cobalt chrome, carbon steel, nickel, nickel alloys and tool steel), ceramics (alumina) and polymers (polyimide and PEEK).

The surfacing process involves use of a Nd:YVO4 diode-pumped laser system, which produces 1,064 nm and 355 wavelengths. The company has integrated this process into a five-axis work station, he said, adding that this provides maximum flexibility. Because the laser system produces two different wavelengths, it is  capable of producing a wide range of  features (~10 µm to 1,000 µm). The short pulse duration of the system (~35 ns) allows for superior ablation efficiency of the material without putting extra heat into the part.

Although other surfacing techniques exist for orthopedic implants, they add material to the device and require a second step in the form of a heat treatment. This heat treatment changes the physical size of the implant and requires extra labor, according to Mound Laser. Laser surfacing requires no additional processing and no materials need to be added to the implant, the company says. It simply ablates material from the surface and does not alter the chemistry of the device, a clear advantage over previous surfacing methods, according to Hartke. In addition, because the procedure is essentially non-contact, straightforward automation is easier to accomplish.

Like many other companies, Mound Laser is a newer entrant to the field of orthopedics. A few years ago, company officials took a look at the projected market for orthopedic devices and saw huge growth potential. As many companies jump into this market, machine shops that have been in the orthopedics business for 30 or 40 year now face competition from high-tech firms such as Mound Laser—and these companies all must confront tighter deadlines on ever-smaller components.

But  business challenges are not always a negative. The trend toward smaller, more challenging parts actually helps Electrolizing Corp., according to Harris. “The smaller or more complex the part is, the more difficult the job,” he said, “and that keeps our competition out, because we have the superior technology and experience. Our advantage is knowing how to handle difficult jobs that other platers do not know how to process.”