Therapeutic symbols: Medical Manufacturing

When marking parts, multiple methods are available. When marking medical devices, especially metal implantable ones, a laser is the primary tool, according to Andrew Bourgoine, co-president and vice president of sales for Geo. T. Schmidt Inc. In addition to fiber, ultraviolet, carbon dioxide and green laser marking equipment, the manufacturer of marking systems offers options for dot peen marking; scribe marking; handheld inkjet printing; and traditional marking, including roll, rotary roll, press and steel stamps.

Dot peening has a limited place in marking medical devices, he noted, but only for items that do not go in the body, such as oxygen tank cylinders and pipes at a medical facility that are marked to assist maintenance personnel.

Although CO2 lasers are mainly for marking organic material, such as glass and wood, as well as plastics and other non-metallic materials, Bourgoine said fiber lasers are suitable for marking metal. UV lasers are for plastic, while green lasers are ideal for heat-sensitive materials, including those with reflective surfaces, delicate plastics and soft or sensitive components. For example, a large medical supply company “cold marks” plastic parts with a UV laser because the wavelength and heat from a fiber laser would melt the plastic.

To mark medical instruments and devices made of stainless steel, Bourgoine recommends using a fiber laser and creating a heat mark, which is also known as carbon migration or laser annealing. The heat from the laser during this thermos-chemical reaction alters the color of the material, resulting in a visible mark without the displacement of any material. “We are raising the carbon up out of the stainless steel, so we’re not really engraving the material. This is particularly important for medical components, where surface integrity must be preserved to deter the growth of bacteria.”

Xact Wire EDM’s customers include many medical companies that may require laser part marking as a secondary process to its wire and small-hole EDMing services. Image courtesy of Xact Wire EDM

The company, which was founded in 1895, reports that other types of marks include laser etching, or ablation, and engraving. The former displaces very little material, and the marking depth can be as little as 0.0254 mm (0.001″) and often involves removing a topcoat, such as an anodized laser, to expose material. Engraving goes deeper and is suitable for parts that experience a lot of wear, are exposed to extreme temperatures or undergo a post-processing step such as painting.

Bourgoine noted that GT Schmidt targets its marking system sales — of which medical customers account for 5% to 10% — to OEMs and suppliers to OEMs. “We really don’t supply machines to anybody that is doing contract marking.”

X Marks the Spot

Xact Wire EDM Corp. in Waukesha, Wisconsin, was started in 1984 to provide wire EDM and small-hole EDM services to customers across the U.S. A second facility was added in 1994 in Cary, Illinois. Both locations began offering laser marking services as a value-added service to complement the wire and small-hole EDM services, said Michael Raasch, business development. Xact’s customers include many medical companies that may require laser part marking as a secondary process to wire EDMing.

“Some of our projects include such items as identification with bar codes, QR codes, logos, serial numbers, patent numbers, date codes and more,” Raasch said.

Each of the company’s locations has a Zetalase fiber laser marking machine with a rotary device for 360° marking and a Minilase XL20 fiber laser marking machine.

The medical components that Xact has machined include tibial cut guides, resection cut blocks, laparoscopic graspers and forceps, bone plates, surgical needles, and alignment guides. The workpiece materials are metal because they need to be conductive for
EDMing and include titanium, medical-grade stainless, platinum, tungsten and Nitinol. “We’re set up primarily to do laser marking on metal and not plastic. Those types of jobs we would ‘no quote.'”

Xact does not target medical OEMs, who are often served by Tier 1 manufacturers, Raasch said. “Those [Tier 1 manufacturers] would be the companies that we are better suited to work with, because they’re full-service machine shops. They have the connection to the OEMs, and then a lot of times they have EDMs in-house, but they offload work to us when they’re super busy or it’s a tricky part or something that they’re not familiar with.”

GT Schmidt’s GeoMARK Pro laser marking machine can achieve a wide range of depths in metal and plastic parts. Image courtesy of GT Schmidt

Most of the medical marking Xact performs is for instruments and components used externally on a patient, Raasch explained. The company has laser-marked some implants, but those are determined on a case-by-case basis where the risk factor and level of liability play significant roles. The considerations include whether the part is for an implant or instrument, the workpiece material, the type of mark, and whether the part will fit in the marking machine.

“Those would be all the boxes we’d have to check off to look at a project for marking,” he said. “We’d have to make sure that it’s a good process or a good part for us. We may just ‘no quote’ it because there’s too much risk versus the reward.”

Compared to laser engraving, which creates marks 0.0762 mm to 0.127 mm (0.003″ to 0.005″) deep, he said the laser marking Xact performs is shallow at 0.0254 mm to 0.0508 mm (0.002″) deep. With an engraving, someone can run a fingernail along the marking and feel the depth. “That’s not what we do. We’re more at the surface.”