Strength of Spur Gear Teeth with Small Modules of the Order of 0.1 mm. 1st Report. Nature of Tooth Failure.

Abstract

There is an increasing interest in the research and the development on micro machines and small gears as their components. It has also been an attempt to produce small gears as a technical challenge. A successful operation of those gears is doubtful in view of gear design, as there has been no consideration on their mechanical properties. It is essential to define the failure mode when discussing the gear strength but very little is known about gear teeth failure of small gears. Thus the strength of spur gear teeth with small modules of the order of 0. 1 to 1 .0 mm has been studied by using a specially designed gear test rig. Higher precisions in alignment is achieved which is appropriate for small gears. The failure mode of gear teeth was observed for both tempered and soft nitrided gears. A sign of uneven contact along face width was found only for very small gears of modules 0.1 and 0.2 mm, which is very unlikely for such high precision in alignments of gear axes. This resulted in the tooth breakage after extended period of operation. A characteristic failure at tooth tip, also on the tooth crest, was found.