Assembly - January 2009 - (Page 53) Bearing surfaces. With the average age of joint replacement patients becoming younger and younger, the traditional metalon-metal implant is generating too much wear. Orthopedic surgeons are moving toward using metal-on-plastic designs until a better alternative emerges. “It will be important for companies to develop costeffective methods to manufacture devices and make them available to the market at the best price,” says Aarti Shetty, healthcare industry analyst at Frost & Sullivan Inc. (San Antonio). “Technology innovation has to be a continuous pattern in developing methods of production that can cater to the needs of surgeons and patients, and also increase the life of the implants. “Though the materials world has seen a lot of development, just as in every other sector of medical device development, there’s lot of room for improvement, particularly in areas involving device wear and the avoidance of debris that can turn a good implant into a lot of pain and anxiety for the patient. Thus, manufacturers have to be on their toes to provide a more solid solution.” Material Challenges Joint replacement implants typically have short product life cycles. Excessive material wear often causes orthopedic devices to deteriorate in approximately 10 to 15 years. “The million-dollar question that most surgeons want to know is if manufacturers can help them find an implant that can last a lifetime and still continue to provide normal joint function,” says Shetty. As a result, material selection plays a critical role in manufacturing artificial hips, knees, shoulders and other implantable devices. Metals are often prescribed, with titanium alloy widely used due to its biocompatibility with the human body. Titanium also features mechanical properties that are closer to bone when compared to other FDA-approved metals, such as stainless steel and cobalt chrome alloys. Titanium and titanium alloys can be welded using arc, spot, seam, flash, pressure, friction, electron beam and laser methods. “Laser welding is the process of choice to hermetically seal orthopedic implants,” explains George Ritter, technology leader in engineering, materials and structural integrity at the Edison Welding Institute (EWI, Columbus, OH). “Laser joining is a contact-free process, therefore minimizing mechanical load on the parts to be joined,” Ritter points out. “The controlled heat input decreases the potential for thermal damage to the highly sensitive components. Laser joining also offers flexibility, shorter processing time and higher quality.” But, titanium poses unique challenges to medical device engineers. “In general, joining procedures and equipment are similar to those used to join stainless steels and aluminum parts,” says Jose Ramirez, principal engineer at EWI. “However, because titanium and titanium alloy are extremely reactive above 1,000 F, additional precautions must be taken to shield the joint from air.” The titanium industry has experienced supply chain problems, due to extremely high demand and limited supply of The SCHMIDT Solution SCHMIDT® ServoPress Systems • Fully integrated, self-contained system For Absolute Press Control & Real Time Feedback • Closed loop control of ram force and distance accuracy of .0004” compensation • Positioning • Dynamic bending • 100% quality assurance and verification ® Call 1-800-959-1218 Visit: www.schmidtpresses.com The SCHMIDT Solution SCHMIDT® ManualPress 300 Series • Versatile, • • • • • hand-powered operation with process monitoring Sequence/Monitor controller Electronic stroke control via clutch and brake Rack & Pinion and Toggle Press models Integrated load cell and linear scale “Poke Yoke” process verification For Cost Effective Assembly with 100% QC and Stroke Control ® Call 1-800-959-1218 Visit: www.schmidtpresses.com www.assemblymag.com January 2009 / ASSE M B LY 53 http://www.schmidtpresses.com http://www.schmidtpresses.com http://www.schmidtpresses.com http://www.schmidtpresses.com http://www.assemblymag.com
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