Speculation about the future of surface treatment for medical applications tends to suggest advancements that are both amazing and years away. The application of nanocoatings to miniature implantable devices, to name one example, could eventually lead to healing patients on the cellular level. The prospect is undoubtedly intriguing, and many companies and researchers are working to advance this and other almost unimaginable innovations. But other companies are taking a more modest—though no less important—approach to surface treatment. They are developing and refining technologies in order to improve existing manufacturing methods and products. The biggest challenge? Making OEMs aware that their tried-and-true processes may no longer be the best options available.
Bonding with Atmospheric Plasma
Enercon’s Plasma3 VCP system is suitable for treating minimally contoured components such as tubing and wire.
Although atmospheric plasma technology has been around for several years, not all medical device OEMs are up to speed on what it can offer, says Tim Nimmer, product manager at Enercon Industries (Menomonee Falls, WI; www.enerconind.com). “We’ve made site visits to potential customers’ facilities and have been shown some pretty convoluted fixes they’ve set up to bond unresponsive materials together,” he says. “We demo our system and it comes as a surprise that bonds this strong can be made with a tool this fast.”
Enercon offers corona, corona gas, and atmospheric plasma treatment systems, which enables company developers to speak from firsthand experience about the comparative benefits of the latter for bonding and etching, according to Nimmer. “We observe that substrates that are plasma treated, rather than corona treated, hold their treatment levels longer,” Nimmer says. “Longer treatment life will allow converters to plasma to increase inventory life and enhance their manufacturing flexibility.”
Furthermore, plasma systems can enable processing of difficult-to-treat surfaces. For example, fluoropolymer-based materials, such as Teflon, do not respond to the corona process, but do respond to plasma treatment. Effective treatment of thick substrates is another potential benefit of plasma. “While substrates that are thicker than 0.125 in. usually don’t respond well to the corona process, they can be treated by our Plasma3 systems,” Nimmer says. “Films, foams, and metals are all candidates for plasma treatment.”
The company, which recently introduced a new system—the Plasma3 VCP—specifically for minimally contoured components such as tubing and wiring, offers application-specific testing of its latest technologies in its surface-treatment laboratory. “We want to show [customers] the concrete results of the various processes so that they can make an informed decision,” Nimmer says. “We’re confident that after testing a plasma system, a number of companies will decide that they need this tool in their shop.”
The Openair plasma system from Plasmatreat is designed for high-throughput processing.
Nimmer isn’t alone in noticing an information gap between atmospheric plasma system suppliers and medical OEMs. “A lot of medical device manufacturers are using autoclaving oven systems when they could be using atmospheric plasma for more-efficient large-scale production runs,” says Ron Jamieson, business manager at Plasmatreat North America Inc. (Mississauga, ON, Canada; www.plasmatreat.com).
As a cleaning process, there are benefits to autoclaving technology, as Jamieson is quick to acknowledge. It is conceptually simple, it only consumes water, and it’s effective on most surfaces. But it still involves a separate batch process requiring cycle times that are typically 15 minutes or more in duration, making it difficult to apply the technology to larger manufacturing processes that might include molding, bonding, and etching. Atmospheric plasma, in contrast, eliminates the need for discrete batches. “Plasma can be applied in-line with other processes to increase productivity,” Jamieson says.
The company’s Openair plasma system is designed for high-throughput processing and is characterized by threefold action: surface activation by selective oxidation processes, simultaneous discharging, and the microfine cleaning achieved separately by autoclaving systems. Also, some materials are damaged or lose important characteristics from exposure to steam, which occurs during autoclaving processes. In an atmospheric plasma process, the only exposure the materials undergo is to plasma formed by the electrical excitation of air.
The bonding capabilities of the Openair system could also eliminate the need for other inefficient processes. Plastics and elastomers offer many benefits to engineers, but bolting, clamping, and welding can come at a high cost and may restrict design flexibility. Plasma treatment, however, can activate polymer surfaces and drastically improve adhesion, sometimes 30 to 50 fold, according to the company. Activation occurs only at the surface, so the integrity of the material is maintained.
Still, what manufacturing process or equipment a company chooses should always depend on the application at hand. “If I’m advising a group who is preparing a short run of a product, then I might say that an autoclave oven is a better option for them,” Jamieson says. “But it’s more common to run into someone who doesn’t realize that they stand to benefit from [atmospheric plasma].”
Plating Technology Keeps the Rust Off
“There’s a widespread belief that stainless steel doesn’t rust,” says Chris Blaszczyk, manager of product development at Misumi USA (Schaumburg, IL; www.misumiusa.com). “But that’s not true; it just rusts at a relatively slow pace, creating a false perception of resistance.”
Also, Type 440C stainless steel—a common grade used for automation equipment and cutting tools, specialties of Misumi USA—has a martensitic microstructure, which exhibits undesirable magnetic qualities and provides less corrosion resistance than other stainless-steel grades. These drawbacks become evident after years of use, Blaszczyk says.
To help manufacturers overcome these shortcomings, the company is offering a low-temperature, black-chrome (LTBC) plating process for components. The technology is already used by many companies in Japan where it was first developed, but has been slow to gain traction in North America. The plating process involves using an electrochemical reaction below 0°C to form an alloy-like diffusion layer at the outer margin of the part, allowing chrome particles to integrate the base material and create a bond that can’t be peeled or flaked off. The end result is a uniform, rust-resistant film layer that offers a service life exceeding 10 years, and in some cases, 20 years, according to the company. LTBC plating is available for various hardware components.
The company, which offers 52100 bearing-steel and 440C stainless-steel components in addition to LTBC plating, has conducted tests comparing the performances of each. “The test samples really show the difference,” Blaszczyk says. “Any company that is seeking greater longevity for their equipment should consider taking a look.”