Development of a System for Measuring Dimensions Based on the Detection of Positional Vectors and Normal Vectors

This paper presents the development of a system for measuring a positional vector and a unit normal vector of a point to be measured, and proposes new measuring methods of dimensions such as a distance between parallel planes and radii of a cylinder and a sphere. The system is constructed of a CNC three coordinate measuring machine and a newly developed probe which consists of a quartz glass ball with a thin resistant film of TiN and four electrodes of Au. Since the probe is able to directly detect the contact point between the probe and an object to be measured, the system is able to measure a position vector and a unit normal vector of the contact point. The measuring accuracy of the system is 0.1 degree in the directions of θ and ϕ which are spherical coordinates to indicate the normal vector. The proposed methods are based on measurements of position vectors and unit normal vectors, and obtain two-fold and threefold measuring efficiency in comparison to conventional methods. The usefulness of the proposed methods is confirmed by experiments of measurement of a block gauge, a cylinder gauge and a steel ball.