The Research And Design Of The Control System Of Bar Shearing Machine

The production line of steel bar rolling runs continuously to cut the head and tail of the rolled piece in a high speed. These pieces with irregular shape or low temperature will be excluded for the next step.This process is carried out by the flying shear which needs the most complex and accuracy control in automatic rolling. Therefore, the study on flying shears control system is meaningful and it would improve the control of rolling.In order to improve the control of flying shear in Xilin Iron and Steel Group Co. Ltd., this study was performed to investigate the control system of flying shear and to make some technology improvements.Considering the flying shears system served as part of the steel bar production system, an investigation on the whole technology and process was implemented before the study. The effect of edge trajectory, network structure and the scan time of PLC of flying shear system on the cut accuracy was analyzed to improve the control of flying shear and the probability of successful production.We proposed a technology improvements on the edge of 3# flying shears(double length shears). And the location accuracy was increased from 5.6% to 0.3%, which means the error angle decrease from 20 degree to 1.7 degree. The delay time of the short shears cutting the tail piece was also analyzed, so it could be decided by operator based on thesituation. By accumulation of the PLC system scan time, the error caused by function module delay was disappeared, so the error of cut length of double length shears was reduced by 33.6cm. Communication fault inside the system could be diagnosed by PLC program, which was based on the analysis of principles and settings of the communication of the flying shear system.A study was performed on the selection and parameter stings of the original flying shears control system 6RA70, while the technology improvements was carrying out. The PLC was optimized by changing S7-300_S7400 control mode into S7-200_S7-300_S7-400 control mode to short the communication with S7-200. So the reaction time and the spare parts costs both reduced.At last, the program was wrote in STEP7 v5.5 and the user interface was designed in WINCC6.2. It ran well in the actual production process.The cut accuracy and probability of successful production were all increased.