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Outlook


Medical Implant OEMs Set Their Sights on Ceramics


Practically all of the major medical implant OEMs are actively pursuing, in one way or another, the viability of manufacturing various common im- plants from ceramic materials. Ceramics are perfect for implant use. Tey provide much higher levels of strength, wear resistance, smoothness and biocompat- ibility when compared with metals and polymers. However, ceramics lack one very important quality—machinability. Mention ceramics and most people


visualize dinner plates or coffee mugs that easily shatter when dropped on a hard surface. Medical ceramics are much tougher, denser, and therefore not as brittle and, unfortunately, not easy to machine using conventional methods. Tankfully, lasers may offer a remedy. Currently, a very select few of ceram-


ic implants are being produced. Tey are simplistic in shape because they are produced using grinding machines with diamond wheels that have limited capabilities when it comes to accessing contours, pockets and other complex part shapes. Such grinding is also slow, making manufacturing costly and, in turn, the implants extremely expensive. Te majority of implants produced


today are made from titanium, cobalt chrome or stainless steel. Te most common implants are for knee and hip replacements, but femoral, articular and tibular components are also prevalent. Te average lifespan of metal im-


plants depends on use. Te more active the implant recipient is, the faster the implant will wear. In some instances, this may only be about 10 years, possibly 25 years for a less active person. Tis means that, for younger recipients of


metal implants, the initial implant would quite possibly have to be replaced one or two additional times in the course of the person’s life. And the rehabilitation for such orthopedic-type operations is quite painful and extensive. Now consider ceramic implants,


which would last on average 75 years— basically a person’s lifetime. An implant recipient would undergo only one surgery and recuperation period. Plus, there would be no implant abrasion to generate foreign particles in the body, as occurs when metal implants wear.


Medical ceramics are not easy to machine using conventional methods. Lasers may offer a remedy.


But none of the benefits of ceramic


implants will be realized until the mate- rial can be cost-effectively machined, making those implants more readily available and affordable. Tis is why manufacturers, universities and other research facilities have been explor- ing and testing different approaches to machine ceramics using conventional machine tools. One technique, involving a laser, is generating promising results. Key elements of this process are


specially designed cutting inserts and a radical use of a laser mounted on a multitasking machine tool. Te ma- chine precisely positions the laser beam ahead of the cutting insert to plasticize the workpiece material, making it easier to cut. Developments in cutter technologies


that are advancing the cost-effective machining of ceramics include poly- crystalline diamond (PCD) and cubic


Don Graham


Manager, Education & Technical Services Seco Tools Troy, MI


boron nitride (CBN). CBN shows strong potential in several ceramic applications. Additionally, extremely hard carbide tooling has been tested for ceramics. To date, laser-assisted machining has


made it possible to successfully turn, mill and thread ceramic materials such as silicon nitride, zirconium and alu- mina. But most significantly, the system increases cutting tool life and reduces processing times for these materials, while also allowing parts to be produced that were previously impossible to make. Tose entities involved with the de-


velopment of laser-assisted machining techniques will continue to gain a better overall understanding of the ceramic cutting process, and great strides will be made in the use of ceramics within the medical industry, as well as for other applications such as automotive and aerospace engine components and bearings. Currently, however, there must be more testing to gain a bet- ter understanding of cutting tool edge preparations and chemical interactions between cutting tools and specific ceramic materials. Further testing will also help increase efficient use of the laser to heat the ceramic materials faster and with better precision. If progress with the laser-assisted


method continues at its current pace, the machining of ceramics could replace diamond-wheel grinding in much the same way that hard turning replaced grinding 20 years ago. And while the method is in its infancy, a major milestone has been passed in the quest to reduce the cost of manufacturing medical implants and components from industrial ceramics.


Medical Manufacturing 2013 27


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