Computer aided design of involute gear shaper cutters

Abstract

The global market competition has put a pressure on the industry to reduce lead time and increase quality of parts. In particular, the area of gear cutting tool design requires capability to rapidly produce tool designs with increased tool geometry precision. The aim of this research is to explore the field of gear shaper cutter design and produce a model and software that would enable creation of more precise cutter designs, faster. A literature survey of involute cylindrical gearing geometry highlights deficiencies in addressing industry requirements of tool manufacturing, as most of the research in the area is focused on problems of gear design, but not tool design. This research, therefore, focuses on the process of gear manufacturing using the gear shaper cutters. It attempts to develop an analytical model and a set of tools that are able to aid the design process of gear shaper cutter. With cylindrical gear being essentially " at" and therefore easier to express an- alytically, the focus of recent papers has shifted to non-cylindrical and non-involute gear trains. Yet the geometry of the tools used to produce cylindrical gears remains largely untapped area, in particular the geometry of gear shaper cutters. The knowl- edge about the profile of the cutter teeth and the profile cut by the cutter in the gear blank are essential for high precision gear manufacturing. The gear shaper cutter is a metal cutting tool and therefore should be re-sharpened on a regular basis. These re-sharpening operations change the profile of the tool and, consequently, the profile of the gear it cuts. The changes in the cutter and gear geometry are analysed in this thesis and a way to calculate the life span of the tool is suggested. Gear shaper cutter profiles usually have one or more modifications to the theoret- ical ideal involute profile applied. Some of these modifications are used to produce a better cutter profile, while other should in turn produce modifications to the gear profile, and, finally, some are used to overcome generated gear profile constraints. Computer-Aided Design (CAD) software for gear shaper cutter design should be able to show the profile of the cutter and the profile cut by the cutter with arbitrary modifications applied. The analysis and visualisation of gear shaper cutters profiles cut by these cutters is impossible without a clear understanding of the principles of operation of gear generation hardware, generating motion and different machine geometry, all being covered in this thesis. In order to verify the analytical model and the CAD software case studies of the real-life gear shaper cutter designs were performed.