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Medical Metrology


grinders, as well as three and five-axis machine tools in the machining portion of their business. Today OVT operates 24 hours a day, six days a week to


manufacture its own line of carbide cutting tools developed for machining titanium cobalt chrome and stainless steel materials. OVT also works closely with medical OEMs, oſten at the design phase with product engineers, to develop cutting geometries required for OEMs’ surgical cutting devices. OVT’s unique design capabilities set it apart in the orthopedic cutting tool industry and allow it to improve on what is currently available. OVT has also expanded to include a global reach by becoming a sister company to SGS Tool, the global leader in production of carbide cutting tools.


A Break with Tradition To provide high-quality products that meet or exceed


customer expectations, the part inspection process must be accurate and reliable. Dahms said, “As we were growing and expanding our manufacturing capabilities, we were finding that the traditional optical comparators we had been primarily using to check the parts were not well-suited to meet OVT’s increasing requirements.” OVT was not satisfied with the accuracy they were getting and also disliked the limitations of using overlays (also called templates or Mylars).


Optical comparators require overlays to allow operators to


verify that parts are in tolerance. Overlays are not well-suited for quick turnover jobs and present a number of problems which include the requirement to be physically stored and managed, as well as repeatability challenges from operator to operator (including the possibility of generating errors due to operator subjectivity). In addition, overlays can be dam- aged, can only be used at a single magnification and require periodic recalibration. Te accuracy of optical comparators is also oſten insuf-


ficient to meet today’s ever-tighter tolerances. At OVT, the company is typically meeting tolerances of 0.001" (0.0254 mm) and less. Other limitations include the fact that 30" (762 mm) optical comparators have a large footprint and take up a lot of precious floor space. Also, optical comparators can only inspect parts that fit


within their optical field of view. So for example, a 10× mag- nification 30" comparator can only check parts that measure 3" (76.2 mm) or less against an overlay. At OVT this presented a problem. For example, when manufacturing reamers, which can be as long as 28" (711.2 mm), they required a larger field of view. Dahms wanted a better way to check parts. Hearing of


the success that some of his own customers—large medical device and orthopedic implant OEMs—were having with the VisionGauge Digital Optical Comparator, Dahms looked into this instrument’s capabilities and he liked what he saw during a demonstration. Tis led to OVT purchasing the digital opti- cal comparator.


Increased Productivity through Digital Technology Te VisionGauge Digital Optical Comparator, developed


by VISIONx (Pointe-Claire, Quebec) and distributed in North America by Methods Machine Tools Inc. (Sudbury, MA), is a fully-digital drop-in replacement for traditional analog optical comparators. It is available with the same range of magnifications and can accommodate the same part fixtures. OVT selected a versatile system configuration that includes 10×/ 20×/ 50× multi-mag optics capable of an accuracy of better than ±0.0001" (0.00254 mm) and an extended 24" (609.6-mm) travel stage to accommodate long parts. With this configuration, OVT can quickly, easily and accurately inspect and measure the entire array of parts that they produce. Parts range from a submicron-based solid carbide substrate tool— designed to cut cobalt chrome, titanium and stainless steel—to taper ball end mills. VisionGauge offers many benefits including the ability to


Oak View Tool President Matt Dahms uses the VisionGauge Digital Optical Comparator on the shop floor to compare a just-made part to its CAD data.


76 Medical Manufacturing 2013


work directly with CAD data, completely eliminating all of the problems having to do with the production, storage and management of overlays. Also, the CAD overlay “tracks the part” when you move the stage, allowing parts comparison to


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