Analysis of circular interpolation motions in a numerical controlled hydraulic driven system

In the study, a prototype numerical controlled hydraulic system has beendesigned and manufactured, which is believed that it will contribute to thefields of machine design and automation. This system consists of two axeswhich are assembled to each other at 90° in a configuration similar to avertical machining centre. Each axis is driven by a hydraulic cylindercontrolled by the proportional directional valve. The system is controlled bythe FM 357-2 analogue function module, which is used in the control of fouraxes CNC machine tools using closed loop system.By means of the proposed prototype, the positioning errors of circularinterpolation motions are examined according to the ISO 230-4 standardcalled "Circular tests for numerically controlled machine tools". Themeasurements are achieved in the RapidForm software by evaluating thecoordinate data obtained from 5µm linear encoder used in the closed loopcontrol of the system. As a result of the experiments, the circularinterpolation motion capability of the CNC hydraulic driven system wasdetermined and the effects of piston diameter, feed rate, radius and loadcontrol factors on the circularity error were examined. As a result of thestatistical analysis, it is found that the piston diameter is the most effectivefactor on the error and it is followed by radius, feed rate and load,respectively. Lastly, aluminium, wood and plastic materials were machinedwith the cutting device added to the system later and the circularity errorwas compared with the loadless conditions. Consequently, it was observedthat there is a 5,99% error decrease in the circularity error in the loadlessconditions. In addition, in both conditions quite similar results wereobtained in average radius.