An advanced measuring technique for in-process inspection of spiral bevel gearing utilizing a computer controlled multi-axis precision coordinate measuring machine has been developed at Sikorsky Aircraft under sponsorship of the U.S. Army Aviation Systems Command, St. Louis, MO, out of AVSCOM Propulsion Laboratory, Cleveland, Ohio.
This paper describes both the current state-of-the-art inspection technique and an advanced production technique for the in-process inspection and manufacture of high quality spiral bevel gearing. The inspection method currently used for the control of spur and helical tooth profiles is not feasible for spiral bevel gears because the tooth shape and thickness varies over its face width instead of being constant as in the case of spur and helical gears. Spiral bevel gears are currently inspected on Gleason test machines which provide rotating check simulating no-load operation under specified gearbox mounting conditions. Tooth contact patterns are observed by painting the teeth with a marking compound and running the gear with its mating master control gear in a Gleason tester with a light brake load. The gear typically exhibits a localized composite tooth bearing contact pattern which, ideally, should spread out under the operating load, filling the working area of the tooth. The inspection task is a subjective one to ascertain an acceptable full load pattern from a localized composite pattern. The machine operators task is even more difficult because he must make a judgment to change the machine settings in order to correct an undesirable feature in the test pattern.
The advance production measuring technique involves mapping of spiral teeth over their entire working surfaces using a precision coordinate measuring machine and quantitatively comparing surface normals with nominal master gear values or with theoretical values at some 45 grid points. In addition, this technique features a means for rapidly calculating corrective grinding or cutting machine setting changes for controlling the tooth profile geometry within specified tolerance requirements.
Both the gear designer and the gear manufacturing Engineer will have more options in the analysis and manufacture of bevel gearing due to the positive control of the tooth profile geometry and related gear dimensions as made possible by the advanced technique.