Investigation of significant parameters in gear hobbing

Abstract

This study was carried out in order to investigate the effect of cutting parameters on the conventional hobbing process in which the response is analysed and practically tested. The investigation is n six sections: (i) Assessment of cutting torques and power consumed during hobbing. (ii) The study of the variation of gear teeth surface roughness (iii) Investigation of generated vibrations during hobbing (iv) Analysis of the mechanics of uncut-chip (v) The study of tool wear and tool life (vi) A general viewpoint of the economic problem in hobbing. In section (i) tests were conducted in order to assess readily a method of determining cutting torque encountered by hob shaft. Power consumed during hobbing was also measured by changing various cutting parameters. Observations were taken when hobbing spur and helical gears. Unlike others, the effect of cutting speed was shown to have a significant effect both upon cutting torques and power consumed. In section (ii) the nature of gear teeth surface was discussed. Axial feed, hob speed and hob D.P. were seen to have a highly significant influence on surface roughness. In section (iii) investigation was carried out into the effect of cutting parameters upon the machine tool vibration. Stability was shown to depend strongly upon speed, feed and hob D.P. In section (iv) a practical method to calculate volume of metal removed during hobbing is presented and a theoretical analysis of uncut-chip thickness and width is attempted. In section (v) the wear mechanism in hobbing is discussed, "rake face" wear proved to oe a suitable tool-life criterion when cutting materials less than (20 HB) under normal cutting consitions. Cutting speed was seen to have the highest significant influence on tool life, while axial feed was not significant. Section (vi) combines all the previous effects of cutting parameters to give a general viewpoint of the economic problem in hobbing, where power, surface roughness and tangential cutting force were the only constraints restricting the operability region for the given machining conditions.