Development Of An Automatic TIG Butt Welding Equipment For Joining Of Water-supply Copper Tube In High-speed Train

The joining of water-supply copper tube in high-speed train demands replacing manual flame brazing by automatic TIG welding.Based on the analysis of conventional automatic butt welding equipment for joining of tube to tube,a new automatic TIG butt welding machine for joining of elbow to elbow/tube is developed to realize rapid loading and unloading,self-centering and rotating the work piece a circle during welding.The clamping mechanism,supporting mechanism and control system is analyzed and redesigned,thus the quick clamping,rotation and automatic welding of elbows or tubes are obtained.Moreover,the joined tubes can automatically be unloaded from the machine after welding.First,on the analysis of automatic TIG welding technology for joining of watersupply copper tubes in high-speed train,mechanisms of welding equipment are decomposed and studied.A welding fixture with U groove that is capable of loading and unloading automatically is designed.The smooth and continuous rotation process is realized by planetary gear mechanism which is combined with the gear ring with U groove and three gears.The supporting mechanism of copper tube uses four rollers to support the copper tube at the same time,which ensure a stable supporting for elbows and pipes,a smooth rotation,and a quick location.At the same time,the abrasion of the copper tube during rotation is greatly reduced.Then the finite element analysis of straight pipe and elbow clamped by the threejaw chuck is performed to investigate influences of wall thickness and pipe shape on tube deformation during the welding.The finite element model of straight pipe and elbow is established by using ANSYS to study the deformation of straight pipes and elbows under the action of clamping force.The regression equation of the relationship between the deformation and maximum stress and the wall thickness of the straight pipe and the elbow are obtained by using Matlab.At the same time,both kinematic and dynamic analyses of the welding fixture are performed by using ADAMS.Comparisons between simulation results and theoretical results indicate the design validity of the welding fixture.Finally,according to the technical and quality requirements for automatic TIG welding for water-supply copper tubes,PLC is chose as the control system in the welding equipment.The PLC control system reduces the number of control system wiring,and it is easy to be changed with shorter working hours.The touch screen instead of the operating panel is applied to set welding parameters,which has advantages such as more convenient and practical.The main program is simulated and debugged,and then the functions of the program are modified and perfected.