Forschungs- & Entwicklungsinformationsdienst der Gemeinschaft - CORDIS

Final Report Summary - OP3MET (Optical 3D MetrologyAutomated in-line metrology for quality assurance in the manufacturing industry)

In industrial metrology, there is growing demands for measurements with higher accuracy and speed. Although optical three-dimensional (3D) metrology fulfils the speed requirement in most cases, this is often at the expense of accuracy and traceability of the measurements. OP3MET focused on the development of innovative equipment for automated in-line 3D metrology. A main objective in OP3MET was to develop an integrated 3D laser scanner and software solution for the verification of dimensional and geometrical tolerances, including free-form surfaces, on metallic and plastic parts with dimensions up to 200 x 200 x 200 mm. The system, besides ensuring the automatic reconstruction of complete surface models, will be designed to guarantee user-friendliness (one-button operation), versatility, reliability and speed. The new system's price will be one-third of that of comparable existing equipment.

3Shape, DME, IPU, and DIMEG have completed ISO tests on the current 3Shape scanner. Here, it was a particular challenge to adapt the ISO procedures - originally developed for tactile CMMs - to optical systems. Several inaccuracies were identified in the 2007 3Shape scanner, so it is has been possible to pinpoint the sources of inaccuracies in the mechanical design, and these have been improved. By the end of the project, according to VDI norm 2617, the maximum permissible error of form at 60 mm is 16 µm. So the success criterion has been met. End-users, however, are really looking for something not covered by any norm, best termed 'detail level' - the sharpness of edges, the smallest gaps still discernible. OP3MET has shown that standards for these criteria are still missing. This need will be brought to the attention of the relevant bodies by IPU and DIMEG.

Two types of scanners have been developed during this project. The first is an improvement of 3Shape's 2007 scanner with a measuring volume of 80 x 80 x 80 mm. This scanner is now being marketed. For larger object, a second, entirely new scanner has reached prototype stage. It uses a robot arm and has a measuring volume of 300 x 300 x 300 mm. The first prototype design has turned out too unstable, so a redesign has been started towards the end of OP3MET, and will be continued past the project by 3Shape. A patent application for some principles in the scanner is being prepared at the time of this writing. The new line generator developed by NPL, COS, and 3Shape is revolutionary. It has been demonstrated to be able to scan non-homogeneous and even metallic surfaces, a completely novel achievement that will give 3Shape a significant competitive advantage. A patent application has been submitted.

3Shape has developed software to simulate a scan given just the Computer assisted design (CAD) model of the part. This has drastically reduced the time needed for defining a scan sequence with full coverage. 3Shape has completed the automated feature extraction software. The industry survey (IPU, JDeus, Askoll, Sinterom) and workshops with other potential end users at 3Shape have indicated that the scan sequence must be fully defined and reproducible. This requirement prevents the adaptive scanning algorithm proposed in the original solution, because it results in a unique scan sequence for every realisation of the part. Accordingly, the scan simulation software is now the cornerstone in fulfilling the full coverage requirement.

NPL and COS have identified means to eliminate laser speckle. The first is to operate the laser below threshold. This has the advantage of simplicity, but limits the amount of power available for illuminating an object. This could become a problem if fibre coupling is used to direct light from the source to the object. It could also be a problem when scanning dark objects. The second way is to use a rapidly scanning mirror. When this is done on timescales must faster than the camera shutter time, the effect is to reduce or eliminate speckle by time-averaging a changing speckle pattern. The scanning mirror is unfortunately rather costly. The scanning mirror developed by NPL and 3Shape has been proven excellent; it is part of the patent application. The hardware is significantly more expensive than a fixed laser, but the advantages are significant as well, so the market is expected to be willing to pay the price. The blue laser developed by COS creates sharper lines than the 660 nm laser used by 3Shape so far. Unfortunately, it cannot yet supply the same power level, and will thus not be considered for serial production in the first round. COS and 3Shape hope to be able to improve this issue in the future, though.

For 3Shape, the new scanner is the most important outcome of OP3MET. It is being commercialised by 3Shape, with COS potentially becoming a supplier of laser light source units. The scanner is described in detail in the DoW. Given the one remaining problem with stabilising the robot arm, only the smaller version with traditional axes is available so far, along with the OP3MET metrology software. This smaller package has been marketed since early December 2008, with two sales appearing likely at the time of this writing. The robot arm version is expected to be completed in 2009.

3Shape markets the scanner as part of its line of commercial scanners. 3Shape has distributors in over 40 countries world-wide. However, 3Shape will need to expand its marketing organisation beyond its traditional fields, dental and hearing aid applications. For quality control, the market is much more diverse, and the number of units sold per customer will be smaller. Therefore, 3Shape has employed a product manager for the OP3MET scanner, starting 15 January 2009.

The market for 3D scanners for quality control is not virgin; there are already about ten players, many of them much larger companies. However, the novelty of the scanner developed in OP3MET is so significant that 3Shape can hope to enter the market. Sales targets are 50 units in 2009 and 150 units in 2009. The first sale was closed at the end of 2008.

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