Impact of a Robot Manipulation on the Dimensional Measurements in an SPC-Based Robot Cell

Abstract

In our study a robot was used to deliver objects for measurement into the Equator gauging system. To investigate the robot’s manipulation influence on dimensional measurements, the robot’s tasks were divided into basic functions. Based on these basic functions, nine different robot-manipulation scenarios were defined, i.e., from zero to full robot manipulation, for two measuring objects (named Magnet and PKR) and six measurement characteristics (rectangular and spherical). The robot’s manipulation influence was determined on the basis of the statistical parameters Cp, R, and the 6σ obtained from a measurement system analysis (MSA) type-1 study. The results show that the degree of implemented manipulation of the robot affects the scattering of the measurement data. However, the effect is much more pronounced in the case of length measurements than with spherical geometries. Different measuring methods (touch-triggering or scanning measurement mode, number of sampling points) were used, which showed similar measurement data. This directly indicated the influence of the robot’s manipulation on Cp, R and 6σ. Increasing the degree of the robot’s manipulation decreases the Cp value and increases the R and 6σ values for the length measurements. There is no such pronounced course in the spherical geometries, where the values of Cp, R and 6σ remain approximately the same. The main influential factor for decreasing the Cp value with increasing robot manipulation was the angular misalignment of the object’s orientation in the fixture.

Keywords

• CMM
• robot
• manipulation
• SPC
• dimensional measurement
• comparative measurements