DEVELOPMENT OF AN ALTERNATIVE APPROACH FOR CUTTING FORCE DETERMINATION IN BROACHING

摘要

Fir tree slots in turbine discs are used as an attachment between the disc and the blades. To a great extend, these slots are manufactured by broaching. Currently, the used cutting tool material is High Speed Steel (HSS). Due to its low high temperature stability, the manufacturing process is limited to low cutting speeds (v_c = 2-5 m/min) and presents, therefore, a bottleneck in the turbine manufacturing process. To increase the productivity, cemented carbide can be used as cutting tool material with cutting speeds up to five times higher than those used for HSS. Due to the high safety demands, the broaching process requires extensive process design to ensure a high process reliability. For the tool design, profound knowledge of the mechanical loads is mandatory due to its major effect on the manufactured part. Empirical research to investigate the actual mechanical load is time-consuming and expensive due to high tool costs, especially of cemented carbide broaches, and the high amount of possible tool geometry combinations. In this paper, an alternative approach to determine the cutting forces is presented. Grooving experiments were conducted in order to reproduce the engagement conditions from the broaching process. If the transferability of this approach can be shown, the amount of broaching tools as well as the availability of a broaching machine tool for the design of new broaching tools can be decrease dramatically. This would result in a reduction of tool design time and an increase in productivity for tool manufacturers.