Direct Gear Design for Spur and Helical Involute Gears

analysis and design of spur and helical involute gears. Introduction Modern gear design is generally based on standard tools. This makes gear design quite simple (almost like selecting fasteners), economical, and available for everyone, reducing tooling expenses and inventory. At the same time, it is well known that universal standard tools provide gears with less than optimum performance and— in some cases—do not allow for finding acceptable gear solutions. Application specifics, including low noise and vibration, high density of power transmission (lighter weight, smaller size) and others, require gears with nonstandard parameters. That’s why, for example, aviation gear transmissions use tool profiles with custom proportions, such as pressure angle, addendum, and whole depth. The following considerations make application of nonstandard gears suitable and cost-efficient: • CNC cutting machines and CMM gear inspection equipment make production of nonstandard gears as easy as production of standard ones. • Cost of the custom cutting tool is not much higher than that of the cutting tool for standard gears and can be amortized if production quantity is large enough. • The custom gear performance advantage makes a product more competitive and justifies larger tooling inventory, especially in mass production. • Gear grinding is adaptable to custom tooth shapes. • Metal and plastic gear molding cost largely does not depend on tooth shape. This article presents the direct gear design method, which separates gear geometry definition from tool selection, to achieve the best possible performance for a particular product and application. The direct design approach that is commonly used for most parts of mechanisms and machines (for example, cams, linkages, compressor or turbine blades, etc.) determines their profiles according to the operating conditions and desired performance. Ancient engineers used the same Direct Gear Design for Spur and Helical Involute Gears