Novel method and device to minimize the high-order roundness error of large cylindrical rotors

Large cylindrical rotors are used in continuous manufacturing processes to form sheet-like materials, such as steel, non-ferrous metals, cardboard and paper. Runout and roundness of these rotors directly affect the process reliability and quality of the end product. In reconditioning process the rotors are ground to remove wear and damage induced by the continuous manufacturing process. A periodic waviness error is a common wear pattern present in the roundness profile of a rotor. These undulations become problematic at few micrometer amplitude and lead to vibrations in the machinery. A tool was developed to grind the rotor to a minimal roundness error, while removing minimal quantity of material from the rotor surface. The tool consists of a curved contact face that has equal radius to the rotor. The working principle of the tool is that the 300mm long contact face touches only at the undulation peaks of the runout profile, thus removing the material from the high spots. The large contact area additionally has elastic averaging effect, as the contact pressure is highest at the contact points on the undulation peaks. A test rotor with 800mm diameter and 1800mm length was prepared by grinding an error profile at 33^rd harmonic, meaning 33 undulations in the profile. The amplitude of the ground initial error was 10.6 µm. The rotor was ground using a free belt grinding tool and the developed grinding tool and the runout profile was measured periodically. The grinding was continued until the runout amplitudes did not reduce. The results show that using the developed tool, the errors at 33^rd harmonic amplitude can be removed almost completely. However, while using a free belt grinding, 1.4 µm amplitude undulation was left to the rotor surface. The developed tool had also a positive effect on improving the roundness at low harmonics, reducing the errors at 2^nd harmonic significantly. The developed tool performed substantially better in reducing the roundness error than the free belt grinding method.