Possibility for improving the performance of a differential pneumatic comparator by inclining the measuring nozzle

Abstract

Pneumatic control has found irreplaceable applications in the control of machine parts, where high accuracy is required. One of the problems that occur with the long-term use of pneumatic comparator is the fouling of its head. This requires interruption of pneumatic comparator’s work for maintenance, i.e., cleaning the device from accumulated impurities. Fouling of the comparator head is the consequence of the vacuum in the area between the measuring nozzle and the measured workpiece. This paper studies the possibility of vacuum reduction — both in its size and strength by varying the measuring nozzle inclination angle. The research is conducted experimentally via test rig designed for this purpose. The inclination angle of the measuring nozzle was varied from 1°to 7°, with the steps of 1°. The analysis comprises the influence of the measuring nozzle inclination on both radial and the axial pressure distribution on the workpiece surface, as well as the corresponding consequences on the comparator’s pneumatic sensitivity and its application range. Experimental results for four different supply pressures and six axial distances between the measuring nozzle front cross-section and the workpiece surface are presented. It is shown that it is possible to reduce the size of the vacuum zone and decrease the vacuum by inclining the measuring nozzle by a certain angle, depending on the supply pressure po. For a certain value of the supply pressure, it is also possible to move the vacuum zone away from the measuring nozzle’s axis when the nozzle is inclined by the optimal angle. On the downside, inclination of the measuring nozzle leads to a decrease in the application range of the comparator.