FPGA implementation of a tool breakage detection algorithm in CNC milling machines

In this paper, an on-line tool breakage detection algorithm in CNC milling machines is implemented into a single 32,000-gate FPGA from Actel. The tool breakage detection algorithm is based on three pipelined processing units: a two-channel modulo operator, a one dimension wavelet transform and an asymmetry correlator. The two-channel modulo operator performs two twelve-bit square operations and a 25-bit square root. The one dimension wavelet transform performs a 256x8 point matrix per a 256 point vector multiplication over the incoming data from the modulo operator. The third processor performs an asymmetry correlation over the wavelet data to give a single value which contains the estimation of the tool condition. The overall processing unit cost is kept low by using optimized numeric digital structures, suited to fit into a 32,000-gate FPGA while allowing the system to give on-line tool condition estimation. Results are presented in order to show overall system performance.