Torque reduction and workpiece finishing effects due to voltage sags in turning processes

Abstract

The use of computer numerical control machine tools allows the industries to reduce costs and operating time while increasing the quality of the manufactured products. However, any malfunction in the equipment can partially affect the manufacturing process or even provoke the complete production interruption. For this reason, studies about phenomena that could affect the machinery are of interest for the manufacturing industry. In this sense, any disturbance in the electric system could either damage or affect the correct machine operation. The contribution of this work is to estimate the repercussion of voltage sags in conventional turning processes. This study is centered in the parameters of spindle motor torque and workpiece rugosity. A methodology and an analysis procedure are proposed to achieve the mentioned task. The methodology consists of estimating the values of power and torque during the electrical disturbance and establishing their relationship with the surface roughness index, Ra. The input parameters are the voltage, current and spindle speed that are monitored in a computer numerical control lathe affected by different levels of sags; also, the measurement of the workpiece surface roughness is used in the methodology. The analysis consists of calculating torque and rugosity variations due to induced voltage sags in order to find the effects of the sags in the machine performance. Results show that there exists a relationship between the voltage sags, the variations in torque and the rugosity.