Development of new features for automotive glass inspection in-line & off-line

Transcription

1 Mutual efforts pay off Development of new features for automotive glass inspection in-line & off-line Traditionally, in-line and off-line inspection systems for transmitted distortion were developed to measure automotive windshields. Therefore, the online SCREENSCAN-Faultfinder system has seen many worldwide installations on windshield lines in the automotive glass manufacturing industry. The sophisticated multi-functional LABSCAN-Screen system is an established tool for the off-line measurement of automotive glass, frequently found in Research & Development Centers or in Quality Control Departments. In 2003, the LABSCAN-Screen system was first deployed in a manufacturing environment, purely for the measurement of backlites, thereby giving birth to a new challenge. Not only for ISRA GLASS VISION, but also for the glass manufacturers and in turn their customers. The first question was: what could be done with the heating wires? The heat grids caused some trouble, especially when the screen was measured at higher installation angles. The second question was: How to prove process stability with the given software functions? In this case, the system was capable of evaluating and qualifying the results in the specified zones, e.g. with the maximum value found for optical distortion. However, the value was subject to change, and not Page 1

2 only the value itself, but also the position. Consequently, the existing functionality at the time was not sufficient to fulfill the requirements. The third question was even more complex: What specification is both applicable and feasible for backlites? In consideration of the above points, it was clear a new era for application in these systems was coming. Together with the customers, the situation was analyzed in detail and the required measurements defined. This procedure ensured the development of improvements directly addressing customer requirements. As a result of this effort, the following new functions were developed at the beginning of the year: Software: Backlite functionality to blend out the heating wires Software: Measurement Point function to control process stability Hardware: High precision frame holder for the LAB- SCAN-Screen These individual features are described briefly in the following: Backlite functionality The backlite functionality is a specially developed software tool to eliminate the optical disturbances caused by heating wires. With a special filter running from top to bottom the software detects the heating wire based on a certain intensity level threshold. In the next step, the software blends out the heat grid and its immediate vicinity, depending on the filtering methods used. Page 2

3 In the operator display, the heat grid will be visualized in gray color. For the measurement results, all values of the masked area are simply set to empty. Measurement point function The measurement point function allows the definition of an unlimited number of measurement points on the screen. The size of the measurement point, its position and its tolerances are entered explicitly in a dialog box. Also, a descriptive name can be given to the individual measurement spots. After establishing this pattern, it is stored and can be loaded for the evaluation of specific models. For example, during the start up phase of a new model, a random sample of screens is taken out of production to be measured. A comparison of the values yields a trend: stable or unstable. It is a quick and easy way to check if changes made to the process parameters actually improve the quality of the screens. High precision frame holder Together with the development of these two functions, it was observed that the positioning accuracy of the frame had to be improved to meet the requirements for repeatability and reproducibility. In addition, close attention was also paid to ergonomic aspects, to ease the handling of the screens and allow for more effective use of the system. Conclusion: The two new software functions have resolved the first two challenges. Both are available for the LABSCAN-Screen and the SCREENSCAN-Faultfinder. For the in-line system, the measurement Page 3

4 point function is limited in the number of measurement points due to cycle time constraints. What about the third question? An ever increasing number of complex designs are found not only found in the front of the car, but also in the rear. Furthermore, the shape varies greatly from model to model. So, the same facts valid for windshields are also valid for the evaluation of backlites: The specification should take into consideration the specific footprint of each model. It may even be necessary to make the occasional adaptation to the specification. The new software tools perfectly support the need for more flexibility for single screen type evaluation. What s next? Based on this successful mutual effort, the work did not stop. A new software function is on its way to improve the evaluation of the areas in the immediate proximity of the black print on the screens. Page 4

5 Images High precision frame holder (High precision frame.jpg) Measurement point function (Measurement point.jpg) Page 5

6 Measurement of lites with heating wires (Heating wire.jpg) Page 6