OPTIMAL ASSEMBLY PART POSITIONING ON TRANSFORMABLE PIN-JIGS BY ACTIVE PIN MAXIMIZATION AND JOINING POINT ALIGNMENT

Department of Mechanical EngineeringThe production flexibility is an ability to produce several types of products in the same manufacturing system. On the other hand, the fixturing quality refers to the degree of suppression of defects from the jig and fixture system during the manufacturing process, so the quality of the product is proportional to the fixturing quality. The transformable pin-jigs, which is one of the transformable jig systems, is highly flexible, but the products assembled through this jig system are difficult to pass the quality standard because it is hard to obtain the optimal fixturing quality in the transformable jig system. Therefore, we firstly investigated the fixturing quality factor of the transformable pin-jigs to solve this problem. When considering screwing and ultrasonic welding, which are mainly used in the assembly process, the fixturing quality factors are defined as the number of active pins and the joining point alignment. The active pin is a pin that participates in the creation of a jig shape. On the other hand, the joining point is the position where the assembly process is performed, and the alignment is the proximity between the joining point and the corresponding pin-jig point. Since these two factors are determined by the loading position of the product on the transformable pin-jigs, we have proposed the method for optimal assembly part positioning to obtain the optimal fixturing quality that minimizes the assembly defects. The proposed method is based on the iterative closest point (ICP) algorithm and is improved to consider the fixturing quality factors of the transformable pin-jigs. Three case studies have been conducted to verify the improvement of the proposed assembly part positioning compared to the classical ICP algorithm. The result shows improved number of active boundary contact pins and improved joining point alignment. Deformation analysis using the Finite Element Method was also performed to validate the proposed method increases the fixturing quality. The result shows a reduction of the stress and deformation at the optimal position.clos