Development of a System for Measuring the Thickness of Free Curved Plates – Measurement Posture Planning Using C-Space –

Abstract

Although it is important to evaluate the thickness of a product made on a press in order to evaluate the mold, there is currently no appropriate system for measuring the thickness of a free curved plate. This study details the development of an automatic measurement and evaluation system for measuring the thickness of free curved plates. The system uses laser displacement gauges and an industrial robot to measure the thickness of a plate. While the system has been capable of measuring workpieces with relatively simple shapes, there have been collisions between the laser path and workpieces with more complicated shapes, owing to geometrical limits of the gauges in terms of measuring posture. This paper proposes a new method of detecting and avoiding collisions by changing the posture on the basis of CAD data when measurements are taken. In this method, not only the geometrical characteristics of the laser path but also the measuring error characteristics of the gauges stemming from measuring posture are considered. In addition, a continuous measuring path with changes in posture to avoid collision is devised. Experimental results confirm that the proposed method does make it possible to measure the thickness of workpieces with complicated shapes.