Detection system and method suitable for three-piece can weld joint external supplementary coating

The invention relates to the technical field of can making supplementary coating, and discloses an external supplementary coating detection system and method suitable for a three-piece can weld joint, the external supplementary coating system comprises a spray gun and a pneumatic control loop, the detection system comprises a photoelectric detection electric eye and a programmable controller, the spray gun and the photoelectric detection electric eye are fixed on an L-shaped mounting bracket, and the programmable controller is connected with the spray gun and the pneumatic control loop. The fan-shaped surface of the paint sprayed by the spray gun is over against the straight welding seam of the can body, and the light emitted by the photoelectric detection electric eye is over against the fan-shaped surface of the paint; during use, the spray gun sprays a coating fan-shaped surface to carry out external supplementary coating on a straight welding seam of a can body, the photoelectric detection electric eye em