One way implant manufacturers can improve operations is by selecting the proper abrasive for finishing operations. “Finishing orthopedic implants can include four to six steps, from grinding, to finishing, to polishing,” says John L. Barry, senior technical service engineer at 3M Abrasive Systems, St. Paul, Minn., (3m.com). “They require strict tolerances because implants must imitate the intricate movements of the human body. Defects from substandard finishing — including wild scratches and grinding out of tolerance — are typically not noticed until late in manufacturing, or even in the OR. If an implant is deemed defective, it's trashed,” he says.

The right abrasive can eliminate some work and help assure a high quality finish. “Selecting abrasives should be based on what condition the part is in, whether it will be handled manually or robotically, as well as the implant's design and materials,” he adds.

Harder substrates that lengthen implant life make abrasive finishing more challenging. “When finishing a harder substrate, such as cobalt chrome, makers should consider an aggressive mineral for gate removal. Ceramic minerals work well at this because they can be made tough enough to stand up to harder substrates,” he says.

Zirconium implants present their own finishing challenges. “After baking or oxidizing, Zirconium implants are so hard no additional finishing is possible. So if the finish doesn't meet specs, the implant is scrapped. “But ceramic minerals are man-made, so several formulations are available. The more friable ceramics would be a good choice for removing material from unoxidized Zirconium,” says Barry. “In this instance, abrasive manufacturers adjust the mineral content so belts cut well and break down consistently on softer materials.”

Most ceramic-mineral belts have stiff X or Y-weight backings to support the mineral, increase the cutting rate, reduce dulling, and improve the consistency of the belt's performance.

When finishing a surface, consistency and quality of finish are critical. “Implants call for engineered or structured abrasives with minerals such as aluminum oxide,” says Barry. “Some aluminum-oxide belts ensure fresh mineral is uniformly exposed, extending the belt's life while maintaining a consistent cut level. Predictability makes belts easier to work with and reduces rework from out-of-spec finishes. And longer belt life means lower overall costs and reduced belt inventory,” he adds.

Conventional abrasive belts typically have only one mineral layer. “They wear as the mineral becomes rounded and dull, and don't last as long as structured abrasive belts,” says Barry. “Structured abrasive belts usually have a flexible backing to blend contours. Eliminating steps in abrasive finishing means less debris and a cleaner workplace,” he adds.