Involute Spur Gear Template Development by Parametric Technique Using Computer Aided Design

Abstract

There are many methods available for developing profiles of gear and spline teeth. Most of the techniques are inaccurate because they use only an approximation of the involute curve profile. The parametric method
developed in this paper provides accurate involute curve creation using
formulas and exact geometric equations. In addition, the involute curve by
equation technique allows using either Cartesian in terms of X, Y, and Z or
cylindrical coordinate systems to create the involute curve profile. Since
spur gear geometry is controlled by a few basic parameters, a generic gear
can be designed by three common parameters namely the pressure angle (a), the module (m), and the number of teeth (z). Most of the present day CAD systems have no built-in tool for designing such gears. This paper is an attempt in utilizing the concept of parametric technology to develop a
template gear. The gear so developed has true involute profile, which is a
realistic design. This will allow making changes to the gear design by using parametric input. If one gear file is developed using this parametric
technology, with which, different size and variety of spur gears can be
created. The specific objective is to design and develop a template spur gear with 3 module, 30 Teeth, 20° pressure angle based on parametric technique by using CATIA V5R14 package. The later portion it is shown how this model may be retrieved and utilized for developing gears of different modules and number of teeth with change in these input parameters.
Keywords: Parametric design, Template gear, involute curve, x and y coordinates, Laws for x and y co-ordinates, Extrapolated spline, circular
pattern, extrusion