Computerized Determination and Analysis of Cost and Production Rates for Machining Operations. Part 1—Turning

Abstract

Two of the most important factors in any machining operation are the cost per piece and the production rate. Equations have been developed which enable one to calculate these two factors for a given machining operation on a given part and machine tool. Generalized equations for cost and production rate are presented for turning, milling, drilling, reaming, and tapping. The items which make up the cost and production rate can be readily evaluated in each of the equations. The generalized cost per piece and production-rate equations for turning are then expanded to cover brazed and throwaway carbide tools and solid HSS tools. In order to use these equations, it is necessary to have available pertinent tool-life data for each of the tools under the actual machining conditions. Typical tool-life data have been generated and are shown here for a variety of alloys. All of the aforementioned equations have been programmed on a computer so that the cost and production rates can be readily calculated for specific parts, operations, and machine-tool combinations. The computer will print out not only the cost and production rate but also a detailed cost breakdown. A visual examination of each of the cost and production-rate factors makes possible a rapid analysis of the significance of each of the items making up the total cost and production rates. In addition, the cost and production-rate equations for turning have also been optimized. Thus calculations can be made to determine the minimum cost per piece and the maximum production rate for the cases where a mathematical expression, such as the Taylor equation, can be applied relating tool life and cutting speeds. Any projection beyond experimental data would have to be verified to serve as a guide for shop use.