Patent WO-2020015230-A1 (WO)
Title: Static four shaft shoulder friction stir welding stirring head with auxiliary pull cord apparatus and method for simultaneously welding butt-joint weld seam of four surfaces of hollow profile
Inventor: NI PINGTAO
IPC: B23K20/12
Filed: 2018-10-29
Abstract: A stirring head integrating the advantages of static shaft shoulder friction stir welding and double shaft shoulder friction stir welding and capable of high quality and high efficiency simultaneous welding of four surfaces of upper and lower wall panels of a hollow profile provided with a rectangular cavity or a cavity of another shape, an auxiliary pull cord apparatus thereof, and a method for simultaneously welding the butt-joint linear or nearly linear smooth curve butt-joint weld seam of the four surfaces of the hollow profile. Four static shaft shoulders (6, 8, 10, 13) are used for the four surfaces of the upper and lower wall panels (7, 12) of the hollow profile, the upper two shaft shoulders (6, 8) corresponding to two surfaces of the upper wall panel (7) of the profile and the lower two shaft shoulders (10, 13) corresponding to two surfaces of the lower wall panel (12) of the profile; a plurality of pull cords (20, 21, 34, 35) are added for the four shaft shoulders (6, 8, 10, 13), the pulling force of each pull cord (20, 21, 34, 35) being equal to the sum of the dry friction resistance generated by the corresponding shaft shoulder (6, 8, 10, 13) and the friction surface of the workpiece and the forward resistance generated by the workpiece on a corresponding stirring needle (1), to make the main body part of the stirring needle (1) as close as possible to only being subjected to the action of the pure torque borne due to rotation, the shaft shoulders (6, 8, 10, 13), the stirring needle (1), a moving gantry or a moving platform or a moving base of a welding robot moving together with the pull cords (20, 21, 34, 35), the magnitude of the forward velocity being the same, and the forward velocity of the pull cords (20, 21, 34, 35) being the suitable welding velocity. Constant velocity movement can be implement by means of combining a fixed sliding group with the pull cords (20, 21, 34, 35). However, for a nearly linear smooth curve butt-joint weld seam, welding is implementing by means of the base (33) of a stir welding robot having multiple degrees of freedom moving along a guide rail, the base (33) of the robot being provided with an automatic travelling apparatus; or the welding robot is directly mounted on a gantry provided with an automatic travelling apparatus, the gantry moving forward along a guide rail. In addition, the robot must also be provided with a weld seam tracking system and a stirring needle (1) longitudinal force sensor; when the force detected by the longitudinal force sensor is greater than a prescribed value, the stirring needle should be perturbed in the opposite direction to the forward direction, such that the pulling force of the shaft shoulder pull cords (20, 21, 34, 35) increases; however, as the forward velocity of the base (33) of the welding robot is far greater than the perturbation velocity, the combined velocity of the stirring needle (1) is still forward, and the stirring needle (1) will not go backward.