Force-position Control Of Aluminum Foil Fin Insertion Into Cu-tube For Air-conditioning Heat Exchanger

Aluminum foil Fin-tube heat exchanger is the most commonly used in air conditioning industry. The thickness of aluminum foil is lmm and the diameter of aluminum foil fin hole is7.3mm and the diameter of the U-tube is7.0mm. Due to the above and the deformation of U-tube and the fin and other defects, the difficulty of automatic insertion is very high. According to the process characteristics of aluminum foil fin insertion into U-tube, this paper focuses on the assembly of aluminum foils and Cu-tube. The fin-tube insertion automatically is put forward, which is a very important theoretical and practical significance for realizing the automated production of heat exchangers and improving the competitiveness and realizing industry structure adjustment from labor-intensive to technology-intensive in air conditioning industry in China.According to the process and the characteristics of heat exchanger manufacturing, the process defects of aluminum foil fin and U-tube are analyzed and the influence on insertion automatically is analyzed. It is concluded that the force-position of fin-tube assembly is necessary. The wear experiment of fin and Cu-tube is carried out. The results show that:with the increase of insertion times from0to70, the wear width of fin expands from45μm to210μm and the depth expands from4μm to18μm, and the wear of the fin meets the process requirements.Based on the contact position of fin and U-tube in the process of insertion, the mechanical behavior of fin-tube insertion is analyzed. And a model of position judgment and adjustment is built, in which the input are feedback force F from sensor and the angle of the cone cap α, and the output are angle of hole axis and tube axis β and the axis deviation e. Based on the mechanical model, the force-position control strategy of fin insertion into U-tube is put forward.In accordance with the fin-tube insertion operating process, the experimental platform of fin-tube insertion is designed including the claw and the clamp of U-tube. The fin force experiments and fin-tube insertion experiment are carried out. The influence of speed and step on stress of fin is analyzed. It is concluded that the optimum speed is1.2m/min and step is4mm and the maximum force is21N. After the experiments, when the insertion distance is45mm, the adjustment time is1.6s and the cost time of fin-tube insertion is4.1s, providing parameter for automation equipment development.