Study of running-in of spiral bevel gears

Sammanfattning: Hand held power tools have enabled craftsmen and skilled workers in general to increase their productivity while cutting, assembling, and grinding. Atlas Copco Tools has been at the vanguard of ever increasing product performance in hand held power tools. One product module which has been thoroughly studied is the bevel gear transmissions present in Atlas Copco angle head nut runners. For these gears a large variation of service life has been observed due to difference in the running procedures and different service intervals.To extend the service life of nut runners, Atlas Copco Tools has started to investigate the effects from running-in of gears. Running-in is a procedure of reducing the surface roughness which can help to enhance the contact conditions. The impact of running-in can be measured either by the steady state of wear or steady state of friction.In this master thesis, different procedures of running-in have been investigated. The changes in contact pattern, surface roughness values and efficiency losses were measured step-vice during the different running-in setups. In addition, the minimum lubricant film thickness has been calculated analytically and a commercially available gear software provided the contact pattern for perfectly smooth gears which was compared with the real contact situation.The different running-in procedures resulted in one optimized running-in procedure where an increase in gear life was found. The biggest change in surface roughness happens at the very first running-in step. Hence, running the gears for one longer period of time, with low torque and specific speed range, gives the best running-in effects. Moreover, starved lubrication conditions were found which are most likely linked to the present gear design. A redesign is suggested to further increase the gear life.