An integrated allocation method for the PCB assembly line balancing problem with nozzle changes

There are several placement machines connected by a conveyor in a printed circuit board assembly line. The objective of the line balancing problem is to minimize the cycle time of the assembly line, which is the maximum production time of the placement machines. In this paper, the nozzle factor, which is often ignored, is considered in estimating the production time of the placement machine, and the nozzle change is also allowed. The production time of a machine is a linear function of the number of components, the number of turns and the number of nozzle changes performed by the machine, which are determined by the component allocation problem, the nozzle set allocation problem and the head allocation problem. These three allocation problems compose the line balancing problem and are solved iteratively. First, the component allocation problem is solved by proposed genetic algorithms (GAs), which generate feasible allocation solutions directly. To search efficiently, non-selective and selective allocation strategies are proposed to solve the component allocation problem. A greedy heuristic (GH) is proposed to solve the nozzle set allocation problem and the head allocation problem simultaneously. Then, the GAs for the component allocation and the GH for the nozzle set and head allocation are integrated according to their interactive relations. Finally, the efficiency of the composite algorithm is illustrated by numerical analysis.