Intelligent cutting-off of pipes and bars

Traditionally, automatic cutting-off machines, of metallic pipes or bars, use a constant cutting velocity mode. This mode of operation, constant cutting velocity combined with different profiles of materials to be cut, exposes the cutting saw to variable cutting forces. Therefore, the cutting off machine is usually set for the worst expected conditions, otherwise excessive wear of the saw and machine will occur. Further, traditional cutting-off machines require the adjustment of the position of a limit switch in order to automatically detect when the cut of a piece has been completed. The aim of this paper is to study the application of control algorithms to the process of cutting-off of metallic pipes or bars, with variable profiles implemented in an industrial cutting-off machine, commercially available. The presented algorithm concern real-time cutting control and automatic detection of the cutting end. The algorithms are implemented in a low cost programmable logic controller (PLC), allowing its use in industrial applications without significant increase on machine cost. All algorithms were developed having in mind safety issues relative to the operation of the cutting machine in order to prevent catastrophic failure. Also, all process related relevant parameters are monitored on a personal computer using OPC (object linking and embedding - for process control).