Allocating optimal index positions on tool magazines using genetic algorithms

Abstract

This paper presents an optimisation system software developed for the determination of optimal index positions of cutting tools on the automatic tool changer (ATC) or turret magazine of CNC machine tools. Position selection is performed using a genetic algorithm (GA) which takes a list of cutting tools assigned to certain machining operations together with total number of index positions available on the ATC or turret magazines and, catalogue value of indexing time as the input, and then randomly generates an initial population of position sets (chromosomes). New chromosomes are generated using genetic operators: crossover, reproduction and mutation. A fitness function is used to evaluate the goodness of each chromosome in terms of total tool-indexing time. Based on the fitness values, the next generation is formed from the newly generated sequences and old population. As the iterations are continued, the better sequences with higher fitness values (lower total-indexing times) dominate and the system converges to an optimal positioning set. The system is implemented in C programming language and on a PC. It can be used as stand-alone system or as an integrated module of a process planning system called OPPS-PRI ( Optimised Process Planning System for PRIsmatic parts) developed for prismatic parts.