A newer product especially targeting critical jet engine
blades is Renishaw’s OSP60 SPRINT high-speed scanning analog probe for use on machine tools. Te sensor resolution is 0.1 µm and the probe is capable of delivering 1000 points per second over its infrared transmission link. Te head itself can travel at 15 m/min while taking data.
Inspection as a Bottleneck “Te bottleneck in production flow today is inspection,”
said Danny Shacham, chief technology officer for Nextec Laser Metrology LLC (Eastlake, OH). Aſter reviewing existing touch probes, Nextec felt something better was needed. Its solution was to develop a unique laser probe to replace traditional
“On these large CNC machines, aircraft manufacturers have developed some clever techniques to re-establish datums and perform metrology checks on the parts.”
Renishaw also recognized that a complete solution is more
than just the probe. Te Blade Toolkit solution is soſtware integrated with the SPRINT probe to help manufacturers spe- cifically machine blades, blade tips, and blend roots of bladed disks, according to the company. “Jet engine blades can have long machining cycles, 20–30 hours,” explained Somerville, “making a mistake can be very expensive.” Te Blade Tool- kit not only helps with original blades, but also helps repair blades that may no longer have a CAD model associated with them. Te soſtware extrapolates where the machining surface needs to be, providing data to the CNC controller to provide an optimum blend, said Somerville. While accuracy is important, speed of measurement is
also an issue when using probes on a precision CNC ma- chine tool. “When you have to probe, you are losing produc- tion time, so if you probe, you want to do it as quickly as possible,” said Jon Kulikowski, of Blum LMT (Erlanger, KY). To satisfy the need for both speed and accuracy, he pointed to their TC model probes, and to their TC64-Digilog analog touch probe for in-process workpiece inspection for special applications. “Te Digilog probe is a combination of a digital touch trigger probe and analog probe,” he said. It collects data at a speed of 2 m/min and with a repeatability of 0.4 µm (two sigma), according to data from the company. Measure- ment data is communicated via Blum’s BRC wireless radio transmission technology. Te advantage of the combined probe is in scanning bores or shaſts for true roundness, scan- ning surface contours for deviations from a master part or generally scanning for flatness. Kulikowski describes an ideal scenario is to use the probe
in comparative measurements. “A master part is scanned ahead of time, those measurements are stored, and then dur- ing production, a comparative measurement can be made to know whether the part is within its tolerances before it is removed from its fixturing,” he said. An application where the TC64-Digilog has been found to be particularly useful is in precision gear grinding, turbine blades, and blisks. “It is ideal for the low-volume, very-high-value parts one oſten finds in aerospace,” he explained.
probes used on CMMs. Nextec also understood that a funda- mental problem with lasers as metrology instruments is their sensitivity to optical properties of the part. Color, reflectivity, material, surface finish, and viewing angle all can adversely affect the accuracy of simple laser measurements. Enter the WIZprobe, which combines a laser with image
processing, performing what Shacham calls an infinite num- ber of triangulations simultaneously through a toroidal lens. “Te lens looks like a bagel,” he explained. Te probe is adap- tive, so it modulates both the laser power and the sensitivity of the CCD camera, performing self-calibration on-the-fly in response to changing conditions during the scanning pro- cess. Advertised key benefits include measuring highly shiny surfaces, soſt material, edges, and sharp angles among others. He describes the output as similar to that of a touch probe, a single, highly accurate point, in contrast to scanning technolo- gies that produce a cloud of thousands to millions of points within seconds, oſten with embedded noise. It collects data at 50 points per second to an accuracy of 2 µm at two sigma (described as a best-fit accuracy over 100 points). Combining their probe on a CMM chassis with spe-
cial purpose soſtware tailored for jet-engine turbine blades resulted in the WIZblade inspection system. Te soſtware au- tomatically compares actual measurements to part CAD data for easy reporting, with special emphasis on important turbine blade features. Why? “Te leading edge of the blade is critical to the fuel-efficiency of the engine,” he said. Engine efficiencies are becoming ever more critical, since companies he serves, like Rolls-Royce or Pratt & Whitney actually have to commit to a stated engine efficiency—or pay penalties if their engines do not meet agreed-to fuel consumption targets. “Using that data to create cross sections or make scan processes gives all the data the inspector needs.”
Automation Plus Scanning Equals Speed Johan Gout, director of operations for Capture3D (Costa
Mesa, CA) reports that automating inspections of jet engine components ranging from turbine blades to fan casings is also growing. “Te great news is that noncontact scanning and
Aerospace & Defense Manufacturing 2014 93
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