QMT Features: May 2011
White light scanning
White light scanning  of complex tooling processes  provides a much better understanding of the entire surface and how material moves through the tooling cycle.


Medium to large volume metrology is changing rapidly. Precision engineering users in sectors from automotive and rail to marine and aerospace are looking for much higher resolution data – millions of points across a surface versus hundreds - to ensure components correspond to CAD specification, or for the purposes of reverse engineering where components are no longer available.

Meanwhile, manufacturers of high-volume, low-tolerance or high-value items need rapid verification that manufactured products are the shape and size they should be, to prevent material waste - and the associated costs - and delays in meeting ever tighter delivery deadlines.

In particular, high-resolution point measurements are increasingly critical in many metal and composites forming industries. Complex tooling processes in particular require a much better understanding of the entire surface and how material moves through the tooling cycle. This may require a combination of surface image information to track feature movement as well as measurement data.

These increasingly stringent parameters mean longer-established measurement technologies such as mechanical co-ordinate measuring machines (CMMs) and laser scanners are increasingly a bottleneck in the design, manufacturing and quality inspection process owing to the relatively small amounts of sample data they gather and the speed of collection. CMMs can gather only a very small number of points at a time, meaning a detailed virtual representation is labour-intensive and may take days or weeks to create, while laser scanning is highly reliant on operator skill and expertise  - and invariably requires time to be built in for ‘patching’ together individual scans due to the small area that can be scanned at one time.

However, the latest white light large volume metrology systems from Leicestershire-based Phase Vision offer the ability to collect several million measurement points across a surface within a matter of seconds, with minimal operator training required in gathering information, and patching completed automatically and almost instantaneously.

A unique way of using light
The key is in the phrase white light which itself implies a broad spectrum. While the use of different light sources each emitting a specific part of the colour spectrum can be used to help overcome certain environmental problems – for example the need to filter out fluorescent or HID lighting - Phase Vision’s technology differs in that it emits a broad spectrum of light and then uses advanced algorithms in its firmware to process the image information.

This enables a single scanner to handle a much wider range of end applications, as it is less prone to interference from narrow-band light sources. Broad spectrum light and the ability to gather high contrast data are also critical in the measurement of shiny surfaces – an area where Phase Vision is particularly strong, as is the technology’s ability to measure larger objects.

Meanwhile, the ability of Phase Vision’s scanners to overcome issues around ambient light enables the technology to be used in even the most demanding environments – aircraft hangars, docksides and busy production facilities – conditions where some other measurement technologies, designed for use in laboratory environments, will struggle to cope and may deliver either zero or highly inaccurate, unusable data.

White light measurement technology also offers the flexibility to meet highly varied individual client needs in terms of measurement volume, speed and accuracy. Phase Vision’s scanners enables these parameters to be dynamically interchanged so that each solution is “tuned” to the specific needs of the individual application, or alternatively one solution can replace several alternative measurement steps.

This flexibility and scalability is increasingly important, especially in the current economic environment where capital expenditure budgets are still generally quite tight.

Integration into manufacturing
The speed offered by this technology is also seeing white light scanners being introduced into manufacturing production lines where they can take all necessary measurements on products within just a few seconds and compare them against CAD. Systems can be programmed to alert operatives if the measured objects are approaching or exceeding pre-agreed tolerances, with production able to be halted if required to adjust the process.

This is a major breakthrough at a time when manufacturing companies are constantly seeking to optimise their production processes, by increasing efficiency, reducing waste and so maximising output.

Rapid reverse engineering
One example of how white light scanning has helped drastically save cost and time is at Leicestershire-based Tower Tool Company, a specialist engineering toolmaker which was commissioned by a leading polymer manufacturer to reverse engineer a tool used to produce components for a helicopter.

Once the tool was designed, Tower Tool had to verify its accuracy – as is common within aerospace, and increasingly so in automotive applications. Key to this was developing a highly accurate representation of the new tool, for which Tower Tool investigated a number of methods. The use of a CMM was discounted because of the inability of CMMs to measure more than one point at a time. Laser scanning also considered and while speed was not an issue, there were concerns over the accuracy of the results produced.

However, by employing the Phase Vision Quartz range of white light scanners, speed and accuracy were combined, delivering a set of readings within a few minutes which created a highly accurate CAD model of the new tool to be produced. An inspection report was then produced to show compliance to the requirements of the original CAD representation.

Myles Ball of Tower Tool commented: “While the cost of the component was not enormous – about £500 – accuracy was key as it was to be used in a state-of-the-art aerospace application. We couldn’t afford to wait for accurate readings from a CMM and weren’t convinced by laser scanning either – but the Phase Vision equipment delivered on both speed and accuracy and allowed us to prove that our new tool was in line with the CAD requirements.”l
 www.phasevision.com.

 

  
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