Improved productivity in printed wiring board assembly by cellular manufacturing

Abstract

This thesis is to improve the productivity of Printed Wiring Board Assembly (PWBA) production by the use o f a cellular manufacturing. The current production system is use of the conveyor belt that is a batch manufacturing and fixed on one single output rate. The continuous running of the conveyor belt can mask many production wastes. The hand mount process is the key process in PWBA production. It holds the highest number of manpower and only this process that carries out the value added job; the parts assembly. In cellular manufacturing, a loop is designed to group all hand mount parts to be assembled on a board completely before lay the board onto the conveyor belt. This can reduce the material handling along the long conveyor belt so it saves the space and the work in process is reduced. The rest of the processes are modified to have the group technology concept. The touch up process is modified to work in series as a group and uses the manual sliding rails instead of the conveyor belt. The In-Circuit-Test and Circuit-Board-Adjustment processes have been combined to minimize the waiting time waste during machine-controlled time. The final inspection and packing processes’ layouts are rearranged to integrate 2 processes for more compact. The non-value added movement is reduced automatically. In addition, the movement of the hand mount is studied and changed from the “Symmetrical Movement” to “Together Movement”. The parts supplied into the box, which is an indirect job, has been removed out of the production line to eliminate the idle time of the other direct operators during refilling parts. The part box is redesigned to facilitate the grasp motion and reduce the frequency of part supply. The new refilling method is set to be from external loop to eliminate the operation disturbance. The Just-In-Time concept is introduced by standard stock control in between processes. This can reduce the work in process and improve the sensitivity in the irregular quality issues. The cellular manufacturing can serve the fluctuation of the customer order without any big change in process or layout design that is the great benefit to the supply chain management. The One-Man-Operation that can complete all jobs within a loop by use of one operator is extremely flexible for the output rate adjustment. The cellular manufacturing can improve the productivity from 72% to 86% of the operational productivity. Consequently, the manpower is reduced from 18 operators to 15 operators. The space is reduced from 32 m2 to 24 m2, which is 24% reduction. The work in process is reduced from 45 boards to 27 boards, which is 40% improvement.