Abstract— 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 cut- ting saw to variable cutting forces. Therefore, the cutting off machine is usually set for the worst expected conditions, oth- erwise excessive wear of the saw and machine will occur. Fur- ther, 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 metallic pipes or bars, with variable pro- files, implemented in an industrial cutting-off machine, com- mercially available. The presented algorithms 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 applica- tions without significant increase on machine cost. All algo- rithms were developed having in mind safety issues relative to the operation of the cutting machine in order to prevent catas- trophic failure. Also, all process related relevant parameters are monitored on a Personal Computer using OPC (Object Linking and Embedding – for Process Control). Index Terms— Intelligent Cutting-off pipes. I. INTRODUCTION 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 oc- cur. On one hand, if the cutting velocity is too high the worn of the saw as well as the components of the machine are too high. On the other hand, if the cutting velocity is too slow the cutting time significantly increases, reducing productiv- ity of the automatic cutting machine. Further, traditional cutting-off machines require the ad- justment of the position of a limit switch in order to auto- matically detect when the cut of a piece has been com- pleted. In this work, new control algorithms were developed and applied in order to optimize the cutting process by diminish- ing cutting times and maximizing duration of the saw and components of the machine. Also, a new method for auto- matic detection of the completion of the cutting of a piece was developed, therefore neither the limit switch nor its ad- justment are any longer necessary [1]. II. DESCRIPTION In Figure 1 and Figure 2, respectively, the profile of a tube and a rod are shown. If materials with such profiles were to be cut, the exact amount of material that had to be removed at a specific point is also shown, assuming that cutting is performed by a linear saw. The amount of material to be removed is closely linked to the required torque to be applied on the saw. The cutting torque requirements depend on the profile of the pipe, rod or bar, as shown in Figures 1 and 2. In Figure 1, the required cutting torque is higher at the beginning and at the end of the profile rather than in the middle of the pipe. In the middle region of the pipe, the re- quired torque has its lowest value, because in this region the Carlos MACHADO 1 , José MENDES 2 , and Jaime FONSECA 3 1,2,3 Dept. of Industrial Electronics, University of Minho, Portugal, Phone: +351253510190, Fax:+351253510189 e-mail:{carlos.machado | jose.mendes | jaime.fonseca }@dei.uminho.pt 2 Addressee for correspondence Intelligent Cutting-off of Pipes and Bars Cutting Mater i al -24 -20 -16 -12 -8 -4 0 4 8 12 16 20 24 -4 0 4 8 12 16 20 24 28 32 36 40 44 Pipe Profile Cutting Direction Fig1- Pipe Cutting Cutting Mater i al -24 -20 -16 -12 -8 -4 0 4 8 12 16 20 24 -4 0 4 8 12 16 20 24 28 32 36 40 44 Rod Profile Cutting Direction Fig2 - Rod Cutting 0-7803-7912-8/03/$17.00 © 2003 IEEE