CONTENTS........................................................................................................................................1 Terms of Reference ............................................................................................................................2 Metal sheet part..................................................................................................................................2 Scanning The Part ............................................................................................................................3 Import CAD data, Definition of reference points ............................................................................3 Projection of reference points to the scan shell................................................................................4 Constrained RPS registration ...........................................................................................................4 Creating of Whole Deviation Plot....................................................................................................5 Dimensioning ...................................................................................................................................8 Reporting..........................................................................................................................................9 Gap Measurement............................................................................................................................10 Conclusions .......................................................................................................................................11
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Technical Case Study Skoda
Terms of Reference The QC department of Skoda (Mlada Boleslav, Czech Republic) decided some time ago to invest in one optical 3D measurement system. The system should be used for inspection and mould making reasons. On the 19th of October 2004 the VI-9i and RapidForm 2004 were tested by Skoda in Germany in the office of CEBAS GmbH (Achim Smailus). This case study is supposed to be an example and kind of technical aid for similar application in the inspection area. Of course the way of proceeding can be changed according to the customer requirements.
Metal sheet part The visitors from Skoda brought a metal sheet part from a car door and a CAD data set for this part created in CATIA V4. The part had dimensions of approximately 1000 x 20 cm.
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Scanning The Part The scan job was done with 9 shots and with telelens in order to reach high accuracy. No photogrammetry was used for this part so all single shots were assembled with the best fit method. The part was sprayed with normal white developer spray.
Import CAD data, Definition of reference points After importing the CAD data the reference points which were given on a paper sheet had to be defined. The reference points on the CAD model were the points which the scan data had to be fitted to.
From the CAD data a STL model was created to be able to use all advantages of shell to shell registration. (SURFACE/Tool/Convert To Shell) In order to create the reference points on the scan shell, the CAD data and the scan data were registered first with Quick- and then with Whole Register With Polygon (INSPECT/Inspection/Register/ Whole Register With Polygon)
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Technical Case Study Skoda Projection of reference points to the scan shell After registration the defined CAD points were projected to the scan data with the Min. Distance option. (Ref. Geometry/Create/Points/Project On Shell)
Constrained RPS registration One of requirements to the software was the possibility to use constrained RPS registration method. As the RapidForm has this option, the constrained RPS registration was used for final registration of CAD and scan data (INSPECT/Inspection/Register/Constrained RPS)
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According to the given distribution of priority among the reference points different weight was given to respective points. Afterwards the scan shell was registered to the CAD data. No aches were constrained.
Creating of Whole Deviation Plot After the constrained RPS registration had been performed the whole deviation plot was created (INSPECT/Inspection/Whole Deviation/Create with Polygon).
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The sampling ratio was reduced to 5% and the Turn-on-Light button was activated.
On some important spots annotations were added ((INSPECT/Inspection/Annotation/Add/By Picking)
After that several possibilities of sectional deviation were shown to the customer (INSPECT/Inspection/Section Deviation/Create with Polygon) ADr
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Technical Case Study Skoda Dimensioning Also the possibility of RapidForm to create linear and angular dimensioning on both scan and CAD data was very interesting for all visitors (INSPECT/Inspection/Dimension/Linear or Angular)
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Technical Case Study Skoda
Reporting One another requirement to the software was the ability to generate reports on deviations between CAD and scan data. To show that the RapidForm software has a variety of flexible reporting tools several reports in RF were generated (HTTP, Excel and PDF – (INSPECT/inspection/Report/3D HTML/Annotated Vertices)
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Technical Case Study Skoda
Gap Measurement The Skoda representatives wanted additionally to check the ability of our scanner to measure gaps between doors or between a door and a wing on an accomplished car.
The scan job was done outside using a small tent to preserve the scanner and the scan area of direct sunlight on a car of the sales rep. of KM Germany Knut Lehmann. The surfaces were sprayed in order to prevent noisy data due to glossy car lack. After two scans had been done the fine registered data could be evaluated. The measurement was done with the help of linear dimensioning function (INSPECT/Inspection/Dimension/Linear). The scan results were compared with the measurement results made by a calliper. The deviation amounted 0.2 mm which was absolutely acceptable for Skoda people because of bad scanning conditions.
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Technical Case Study Skoda
Conclusions Especially flexibility and short time of scanning could convince the customer. After evaluating the scanner under working conditions the customer plan to buy a second unit. The only critical point from the customer was that it is necessary to spray glossy surfaces. If customers don’t have experience with optical scanners (like Skoda people) it looks strange to them that shiny surfaces have to be sprayed. Our job is to explain to them that this is a general problem of all optical scanners and that VI-9i has fewer problems with shiny objects than e.g. structured light systems. On the other hand we have to mention that the thickness of the spray film can affect the accuracy up to 20 µm.
