A GENERALIZED APPROACH TO DESIGN OF • MACHINE TOOL GEAR BOX ELEMENTS FOR A GIVEN SPEED CHART

Abstract

The housing of gear box should have proper seals or packings at points where the shafts extend from the housing and at the joints of all covers to prevent oil leakage, dirt and abrasive particles. When designing a machine tool gear box, or in the design analysis of an existing one, the following related aspects must be kept in mind. Firstly all the machine parts of the gear box must be so proportioned and related to each other as to provide proper motion. Secondly, each part must be able to withstand the forces/ torques imposed on it. The nature of part movement does not depend upon the strength or absolute dimensions of the parts. Therefore the gear box design methodology can be dealt with under the following two seperate heads [ 23): Kinematic Design This deals with the study of motion, and forms of elements of the gear box [ 25] . 4 Mechanism Design it involves determination of forces, moments and torques. acting •on different elements of the gear box, and selection of appropriate materials, etc. It also involves selection of an optimum speed chart which helps in determining the values of transmission ratios for all the transmission drives to obtain the required discrete speed steps [ 101. 1 The gear boxes in machine tools are employed for stepped regulation of r.p.m. of machine drive. They should provide a series of spindle speeds between minimum and maximum specified values and also transmit power of an amount dictated by the purpose of the machine tool. The provision of regulating the spindle r.p.m. is an essential requirement of a machine tool to ensure economic machining of workpieces of different materials and sizes by cutting tools of different shapes and compositions.........