Research On Automatic Wire Feeding Control Technology Of Ultra-fine Bridge Wire Automatic Welding System

As a commonly used pyrotechnic product in the industrial and military fields,bridge wire electric detonators are widely used in fuze of weapons and ammunition.Bridge wire welding is an important process in the production of electric detonators.The quality of bridge wire welding directly affects the detonation performance of electric detonators.For a long time,the degree of automation of bridge wire welding in China is relatively low.Most manufacturers use manual welding.For welding thicker bridge wires,a few manufacturers have developed semi-automatic welding solutions.There is no mature production equipment for ultra-fine bridge wire,so the development of a new ultra-fine bridge wire automatic welding solution has great application value.The main factors that affect the performance of an electric detonator are the location of the welding point,the surface quality of the bridge wire after welding,and the gap between the surface of the electric detonator and the bridge wire during welding.Based on the analysis of automatic welding and tension control of bridge wires at home and abroad,it is pointed out that the key problems in the automatic welding of micron-sized ultra-fine bridge wires are timing control and wire feeding stability.An automatic welding system for ultra-fine bridge wire based on tension control and stable wire feeding was proposed.The software and hardware combined control method is used to design a sequence control automatic welding controller.Signal formats such as wire feed motor start-up,pinch position,welding gun movement,welding operation,pad motor drive,and pay-off barrel start are determined.Determine a welding cycle timing control sequence: The pay-off motor and take-up motor run synchronously,stop,pneumatic compaction,stop,welding torch and robot movement,stop,welding operation,stop,welding torch and robot return,buffering,pressing return,stop.A sequential timing controller is designed.The simulation results show that each action in the welding process meets the timing requirements.The motion model of the wire feeding system was established,and the expressions related to the tension of the bridge wire and the movements of the pay-off wheel and take-up wheel were obtained,and the expression of the maximum pay-off length adjustable by the buffer device was obtained.According to the sufficient and necessary conditions for the stability of ultra-fine wire feeding,the critical deformation value of the bridge wire elongation was determined through analysis.A method for controlling the tension of the bridge wire to adjust the pay-off radius of the pay-off wheel speed was proposed,and a negative tension feedback control system based on the digital PID control principle was designed.A hardware controller system was built,and the pay-off motor was selected as an integrated AC servo motor.Based on the relationship between the actual online tension value and the output value of the tension sensor,a programmable logic program was written,and the decimal integer processing was performed after the signal analog-to-digital conversion.Simulation experiments verify the tension stability control performance.The results show that the tension value can be controlled to be less than the maximum safe tension value of the bridge wire of 0.08 N,which satisfies the stability conditions of fully automatic welding wire feeding of ultra-fine bridge wires.