Auto Industry Relies on Image Processing for Quality Control
Metal forged parts such as gears, bearings, flanges or housings play an important role in the automotive industry. The parts are hot- or cold-formed from raw material in large presses, producing severe vibrations and filling the factory with heat and dust. The blanks conceal many dimensional imperfections such as irregular shapes, eccentricity of bores, burrs and cracks. Because these forged parts must be further processed, 100 percent inspection is necessary before more net value is added.
The parts inspection system installed at the Ford factory includes Zeiss telecentric lenses that allow inspection of objects with variable heights and the inside of bores.
Otto Computer Vision Systems provided a solution for forged gear blank inspection at the Ford factory in Cologne, Germany. Its PC-based system includes monochrome 752 × 582-pixel charge-coupled device cameras from Pulnix equipped with telecentric Visionmess lenses from Carl Zeiss. The lenses' telecentric range allows not only simple measurement of objects with variable heights, but also the inspection of the inside of the bores. In the second stage of the inspection, the surface shape is taken using the laser light section method. The system software includes custom gray-scale analysis algorithms.
Solving the parts-handling problem took a bit of ingenuity. The parts to be measured needed to be transferred and positioned at both stages, and precise rotation of the parts was required for complete contour measurement. This had to be accomplished with 120-mm-diameter, 50-mm-high steel blanks with a feeding speed of up to 40 parts per minute. The image processing technology itself allowed a speed increase of more than a factor of 10, according to Otto. The system automatically measures inside and outside diameter, center displacement, height and three-dimensional contour fidelity around the circumference. All parameters are measured with 0.1-mm precision and even higher reproducibility.
The introduction of machine vision technology into mass production processes requires a considerable investment and adaptation effort, even for so-called turnkey systems. But cost reductions in quality control, combined with access to statistical process control, are significant benefits.
Ford reports that the system is so successful the company is considering more installations.
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