Parts prove a whole new business

Reverse engineering of obsolete parts has lifted one business into a whole new dimension – aerospace and beyond – as Tom Shelley discovers

Geoff Le Good has built up a thriving business by creating something out of nothing –scanning in parts and tools to recreate what, in one sense, may no longer even exist.
“Often, there are no CAD models,” he says. “Sometimes there are no drawings either.”
His main markets are aerospace and motorsport, particularly for what he describes as heritage projects: making new parts for old aircraft and new parts for new aircraft to old designs. Another area where there is a call for his skills is in hand-modified parts.
“There is a lot of toolmakers’ licence involved here,” says Le Good. “We quite often scan items to capture what people are actually making, rather than what they think they are making. Parts are often modified to fit better for final assembly.”
Optimised wind tunnel models also require solid models to be scanned in – in fact, the possibilities are vast and numerous. “Once you have the CAD model of the real part, you can use it for whatever you want”. By way of example, he mentions design, analysis, machining, simulation, inspection, gaming, film and television.
In terms of his mode of operation, parts can be scanned, glued together (if broken) or the tools themselves can be scanned if they still exist. Of course, scanning old parts always runs the risk of remanufacturing worn components, while gathering measurement data from parts that involve complex curved surfaces, as are common in both aerospace and motorsport, is impractical using trigger probes. Le Good’s company, Admeasure Scanning of Northwich, uses a Faro laser line probe, in conjunction with a Faro 7 axis arm and Geomagic Qualify software. Once the CAD model of a ‘good part’ is in the system, it is possible to scan subsequent parts and compare the cloud of points generated during the scanning process with the CAD model. A subsequent analysis can include colour contour maps, projected on to the part model to show the magnitude of deviations from the nominal condition.
Admeasure Scanning is a UK reseller for Geomagic’s software which, among other things, was used on the 2005 NASA Discovery Space Shuttle mission to assess the state of the heat-resisting tiles. As the shuttle neared the space station, it rolled over to expose its underside. Video surveys and detailed 3D scanning inspections, using a 50-ft extension of the Discovery’s robot arms, were able to determine damage to the tiles underneath the wings.
The plan was that scan data would be transmitted back to base at Houston where Geomagics Studio would be used to process the data and create a 3D model of the damaged tiles. The 3D model was to be used to provide data to create tool paths for cutting facsimiles of potentially dangerous damage into an array of test tiles. The reproductions of the damaged tiles could then be tested at NASA’s ArcJet facility to see if they could withstand the heat and stress of re-entry. If the damage was considered too extensive for safe re-entry and return to earth, a spacewalk by astronauts could be used to make repairs. In this case, the test tiles could be used to develop a step-by-step repair process that would be used during the spacewalk.
In the event, there was no major damage, but two thermal protection tile gap-fillers were spotted jutting out of the shuttle’s underside, and the astronauts and experts on the ground devised a plan to prevent the protrusions from "tripping the boundary layer," causing higher temperatures on the shuttle during atmospheric re-entry. Ground controllers sent up plans to the shuttle station complex for astronaut Steve Robinson to ride the station robotic arm beneath the shuttle and pull out the gap fillers. The shuttle returned safely to earth.


* Scanning is particularly useful for capturing the shape of old or new parts that do not exist as 3D models or whose 3D models no longer represent what they really are

* Having gathered the correct model, it can be used in the analysis or manufacture of new parts

* 3D laser scanning is the only practicable way of capturing complex curved forms or soft parts, such as seats

Tom Shelley

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