Measurement & Inspection
image accurately with conventional optics. Stem tibia, knee, and hip implants, stents, or highly polished bone plates with rounded edges,” he said. Profile and other Geometric Tolerances define the complex and compound curves of orthopedic implants. These require a dense data set, which in turn requires analysis software to match it to the original CAD data, Murray said. OGP offers SmartProfile software to aid in the analysis. Other types of medical parts, such as molded plastic items, microelectronics, and even eyewear present different sorts of measurement chal- lenges. Syringes and surgical stapler components, for example, require special illumination sources and fixturing to reliably image or provide access to critical features.
adoption in the medical industry. These early adopters are using ShapeGrabber scanners because their requirements are so pressing they have to turn to a fast laser system.” The strength of systems like their Ai310 is speed and data den- sity—the ability to collect a million points within a few seconds to about a minute. “These are good for complex, curved shapes such as you find in orthopedic implants, ergonomic tools, and medical enclosures and housings,” said Aubrey. Aubrey noted that their 3D laser scanners have resolutions down to 2 µm and accuracies down to 16 µm (ISO 10360 method), making them ideal for items with unusual shapes with reasonably tight but not extreme accuracy require- ments. A number of biomedical devices, from pace makers to implantable drug-delivery pumps have intricate, small parts which may have very tight accuracy requirements. These small parts are typically enclosed in a housing or attached to a frame. “The ShapeGrabber Ai310 automated scanner is ideal to measure such housings. Parts inside the enclosure—flat gears, valves, and other prismatic parts—are probably best measured using other sensor modalities that can attain tighter tolerances,” he said.
The heart of Orthoflex from Marposs is a visual system that collects data as it scans the surface of super-finished spherical shoulder and hip joints.
Murray also reports that medical customers choosing mul- tisensor vision-based systems usually ask for three sensors. These include their telecentric vision system, a TeleStar TTL laser, and touch probe.
General Systems, Shop-Floor Applications For companies with fewer, more advanced metrology devices in their portfolio, finding the right niche within the industry sometimes requires educating their potential users. “The medical device community is getting more interested in 3D scanning,” said Pierre Aubrey, President of ShapeGrab- ber (Ottawa, ON, Canada). The company specializes in 3D laser line scanners. “We are still in the early days in terms of
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Another category of often-used metrology equipment is the venerable Optical Comparator, recently upgraded into an all-digital version by VISIONx (Pointe-Claire, Quebec, Canada distributed in North America by Methods Machine Tools Inc.; Sudbury, MA). The company’s VisionGauge system uses the part’s CAD data to produce a high-contrast image for com- parison, eliminating the need for Mylar overlays. The company also claims that it is more accurate, enables faster measure- ment, and has a smaller footprint compared to traditional opti- cal comparators. “Our system shines where tight tolerances need to be measured on complex geometries and where there are many small-lot productions because there is virtually no setup time,” explained Patrick Beauchemin, president and CEO for the company. “That describes many medical manu- facturing applications.” Measured accuracies are as fine as 0.0001" to 6 σ, Beauchemin said. An optional laser is offered for depth and height measurements.
“Where we are seeing the most enthusiastic adoption of our system in the medical industry are bone screws and larger implants, such as knee and hip replacements,” Beauchemin said. “Knees and hips have both plastic and metal, and on traditional optical comparators the plastic surfaces have glare that our system completely eliminates.” A large depth of field on their system, up to 4" (100 mm), allows them to measure
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