A Novel Error Detection and Compensation Method of Hourglass Worm Gear Hob

The double enveloping hourglass worm gear pair is a type of transmission, which has many traits, such as more teeth in mesh for transmission, higher contact quality, better lubrication condition and so on. Therefore, it has higher efficiency of transmission, stronger bearing capacity and longer work life. But the manufacturing difficulty of the worm gear hob has limited its popularization and application. Unlike the traditional worm gear hob which can use the principle of optical projection to detect the hob shaft section and compare with its mathematical model, currently, there is no standard mathematical model to detect the shaft section of hourglass worm gear hob. Hence, the accuracy of hourglass worm gear hob can’t be guaranteed during manufacturing process, and the accuracy of hourglass worm gear can’t be guaranteed too. Thus, the transmission performance of the manufactured double enveloping hourglass worm gear pair will be affected. The paper puts forward a novel detection method for hourglass worm gear hob on the basis of the detecting method for traditional worm gear hob and established the mathematical model of the shaft section of hourglass worm gear hob. The manufacturing error of hourglass worm gear hob can be obtained through such detection. The paper also points out that the error is mainly produced during the grinding of hob teeth, because the grinding wheel is worn out and the blank hob is thermally deformed. At last, a method for error compensation is advanced during the process of hob grinding. The paper presents a test to verify the feasibility of this method and the test result shows that the manufacturing error of hourglass worm gear hob is reduced from 30.15μm to 10.3μm.