Evaluation of infeed strategies for turning of large thread profiles

Abstract

Several infeed strategies for multipass threading operations on CNC lathes are well known and they are implemented in form of apropriate canned cycles in system software of CNCs. These strategies are especially suitable for triangular profiles of thread. Paper presents method developed for analysing of infeed strategy in threading operations for arbitrary geometry of thread profile and geometry of tool profile, including trapezoidal threads and worm wheels. Proposed method uses two criteria for evaluation of specific infeed strategy in multipass turning of threads. The first one is the measure of balance of uncut chip area in subsequent passes (implemented application in Matlab is described). Calculation of chip area is based on numerical integration The second criterion is referred to predicion of cutting forces and their distibution in subsequent passes.. Cutting force estimation is based on specific cutting forces and engaged chip area acting on discretized lenghts of cutting edges.