Optical inspection and measurement of workpieces

Grinding tools require precise fine tuning. The Prosilica GT supports the complex manufacturing process by providing high-resolution images for optical inspection and measurement.

Only if a (diamond) grinding wheel has the specified surface structure and shape, can the grinding tool be optimally used in the envisaged grinding machines. In order to ensure the quality of the used tools, gear grinding machine manufacturers usually not only manufacture the machines, but also produce their own grinding tools for these machines.

These grinding tools are manufactured based on precise CAD drawings. Throughout the manufacturing process, a continuous alignment between the workpiece and the corresponding CAD drawing must be carried out. To ensure error-free production of the grinding wheels, an automatic quality inspection system is used for the optical inspection of workpieces. The system was developed by ASinteg GmbH. The company, headquartered in Schwerin, Germany, specializes in application development and system integration in the field of industrial image processing and intelligent image analysis. Their quality inspection systems are equipped with cameras from Allied Vision.

High-precision measurements

The 16 megapixel Prosilica GT4905 continuously generates high-resolution images during the production process of the diamond grinding wheels. Equipped with ON Semiconductor KAI-16050 TRUESENSE Gen 2 CCD sensor, the camera delivers outstanding image quality. At full resolution, the camera achieves a frame rate of 7.5 fps. The combination of telecentric lenses, telecentric illumination and the high-resolution Prosilica GT4905 enables high-precision measurements, which form the basis of the optical inspection system.

The high-resolution images supplied are compared live with the data in the CAD drawing by superimposing them optically. This image analysis and the optical comparison is carried out in the software developed by ASinteg, which uses specially programmed evaluation algorithms. Even the smallest deviation is recorded. The real object is measured with an accuracy of up to 5.5 µm so that even the smallest deviation can be detected and corrected during the manufacturing process. Successful inspection eliminates the need for post-processing on a separate measuring system and saves time.

Continuous adjustment for an error-free result

The software developed by ASinteg also calculates an envelope curve from the recorded outlines and outputs it to an ASCII file. The envelope curve is generated during a rotation of the disk by several images of the recorded outer body edges of the diamond disk. It is used as a set of curves to enclose the diamond disk and, thus, represents the maximum outer contour of the body. It can be determined whether the calculation should be based on one or n measurements.

Various tools produced and installed in machines can be tested and precisely manufactured with the help of the quality inspection system. Manufacturers of gear grinding machines save working and set-up times that would be incurred if measuring machines without a comparable automatic optical inspection system were used. Only the corresponding CAD or DXF data of the workpiece to be inspected must be called up in the system. If contours and conditions do not correspond to the specifications, detailed adjustments can be carried out.