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Hawker Beechcraft Corporation (HBC) is an aircraft producer with a paced assembly line, which means that an aircraft was moved to the next workstation on the assembly line after certain period of time (cycle time) even if work in a previous workstation had not completed. The company suffered chaos and low efficiency because of the lack of a quantitative approach in managing the assembly line. In order to improve the efficiency of the assembly line, the researcher of the article developed a model based on linear programming and assembly-line balancing principles.
The specific goal of the researcher’s model was to minimize the out-of-station work and work in progress, which helps to reduce the number of workstations. The researcher divided the aircraft into 15 independent zones so that every workstation could be regarded as the sum of 15 independent zone areas. Tasks from different zones could be performed simultaneously in the same workstation. The model started with the current HBC solution and was consisted of 6 main steps.
First, the researcher obtained tasks’ duration, its predecessor and the zone to which it is assigned from the current solution.
Second, the researcher reassigned tasks to a zone of a workstation with the principle that they were in the earliest possible workstation and that each task’s predecessors was assigned to the previous or the same workstation. Then, He placed remaining tasks that are not in desired workstation for a latter reassignment.
Third, the researcher used critical path method to establish a network model for each independent zone from different workstations to calculate the minimum duration of an independent zone given the constraints that the time between two nodes is greater or equal to the sum of these two tasks’ duration. If the minimum duration for an independent zone exceeded the cycle time, label the zone as needing modify.
Fourth, the researcher modified the labeled zones using a linear programming model to minimize modifying costs with labor hourly rates and allowable modified time per task.