QMT Features: August 2014
Fast car, fast inspection
Parts for a unique British sports car are inspected using a high accuracy 3D scanning system


The British-designed and manufactured Ariel Atom 3.5 may not have luxuries like doors, roof, or windscreen, but it can accelerate to 100mph (160km/h) in under seven seconds. Powered by a 2 litre Honda i-VTEC engine, with the option of a 310 bhp supercharged version, the two-seater Atom is equally at home as a serious track racer and road-going sports car. 

But as well as exhilarating performance, the car has also been recognised for its build quality. Indeed, the editor-in-chief of the UK motoring magazine Autocar said: “I don’t know any affordable ultra-low volume car so beautifully made.” The person at Ariel Motor Company with ultimate responsibility for ensuring this high level of build quality is managing director, Simon Saunders. And one of the technologies that he has at his disposal is a Solutionix Rexcan CS+ 3D scanning and inspection solution.

“As a small design and manufacturing company producing a technically advanced, low volume product, it’s a real bonus to have access to the sort of accurate 3D measurement capabilities that the Solutionix Rexcan CS+ provides,” says Saunders. “This type of inspection and measurement system wasn’t readily available to small companies like us when we started making the Atom back in 2000,” he adds. The Rexcan CS+ provides a complete, integrated hardware/software 3D scanning solution that can sit on a desk. Using Solutionix’ Blue LED Technology to provide high resolution, high accuracy structured light scanning, rather than the laser technology found in most other scanners, the scanner in the Rexcan CS+ system features interchangeable dual lens sets to provide different degrees of resolution and accuracy – up to 0.035mm point spacing (resolution) with better than 10-15 microns accuracy - depending on what is required. 
The system used at Ariel Motor Company also includes automated 3D measurement and inspection software in the hardware/software bundle.
Ensuring accuracyOne of the first components to be inspected at Ariel using the Solutionix system was a fabricated sheet metal part, known as an upright. This forms part of the Atom’s front suspension system. 
The upright was positioned on the integrated turntable and the scanner was set to look down on it at 45 degrees. With Solutionix ezScan software controlling and coordinating the turntable’s motion and the scanner’s data capture processes, scans of the upper surface of the part were then taken automatically at increments of 10 degrees as the turntable rotated through 360 degrees. The part was then turned over and the process was repeated in order to capture the opposite surface. 
The raw scan data was converted, on the fly as it was captured, to a polygon mesh using Solutionix’ ezScan software, which also merged the individual mesh models together to create one complete polygon mesh model of the part. In order to speed up subsequent processing of the data, curvature-based sampling of the mesh model was performed with the ezScan software to reduce the polygon count in areas of low curvature while retaining it in high curvature areas. This reduced the overall polygon count without losing any of the fine detail.
The whole scan to final mesh model process was completed in less than half an hour and the model was then ready to be taken forward into the automated inspection process.Simple, fast inspection processBefore using the Solutionix solution, parts were inspected in the traditional way at Ariel, using micrometers, vernier calipers and CMMs, or they were sent to an outside company to inspect.  This traditional method requires collecting individual measurements at specific points on the part. Those points are then analysed for any deviation from the nominal as defined on the corresponding 2D part drawings. Inspection can therefore be a long and laborious process, which often means that only a selection of points on the part can be inspected in the available time. With the Solutionix Rexcan CS+ solution things are very different.  The mesh model of the part and its corresponding nominal 3D CAD model are brought into the same 3D virtual space. Datums and features upon which the inspection is going to be based are identified on the CAD model and the two models are aligned with each other using both the automatic and the manual alignment tools in the inspection software.

With the models aligned, the 3D scan data model is automatically analysed against the 3D CAD model to identify and measure any deviations between the physical part and its counterpart 3D CAD model, as well as for GD&T purposes. The software automatically assigns a colour-map to the 3D model, with the different colours representing different degrees of deviation. Actual deviation values are also shown, along with GD&T call-outs.

Generally speaking, surface form errors at Ariel Motor Company are 0.2mm maximum for complex shapes. If appropriate, whisker plots of cross-sections and wall thickness analysis results can also be calculated and displayedInspection reports, which can be formatted according to Ariel’s specific requirements, can be saved or output as PDFs automatically for use by Ariel’s own engineers or for sending to the original part manufacturer for any required remedial action on their part.
If design changes, or analysis such as CFD and/or FEA, or design optimization is required, the scan data can also easily be used to reverse engineer the as-produced part.  
The result of the new inspection process is that what could take days previously can now be completed in just a few hours, meaning that more parts can be inspected in less time – and more thoroughly. 
“The accuracy and speed with which parts can be inspected with the Solutionix system, plus the fact that it’s portable so we can take it to where the job needs to be done rather than needing a dedicated inspection area, is of great benefit to a small manufacturing company like Ariel,” says Saunders. “Not only does it give us the capabilities that until recently have only really been available to large corporations, but it helps us to attain and maintain the high build quality we strive for in a car that’s a world beater.”www.solutionix.com
  
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Rob Tremain Photographer
www.4exposure.co.uk
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