Reactive schedule repair is a better alternative to total rescheduling of impaired job shop schedules. For ease of implementation in the job shops, heuristic-based schedule repair methods are preferred. However, the majority of the repair heuristics reported in the literature are capable of handling only a singular disruption to the schedule. On the contrary, real-world job shops are subjected to multiple complex disruptions that occur randomly over the span of the schedule. A new heuristic, modified affected operation rescheduling (mAOR), has been successfully used for repairing a majority of typical job shop disruptions such as absenteeism of workers, process time variations and arrival of unexpected jobs using a combination of generic repair steps. In the present work, the mAOR heuristic has been applied for repairing randomly occurring multiple disruptions under rigorous shop floor conditions. The relationship between the variation of shop floor conditions and the performance of the schedule repair heuristic is investigated to substantiate the effectiveness of the mAOR heuristic. The results of extensive experimentation indicate that the performance of the mAOR heuristic is superior to the right shift rescheduling heuristic (a commonly cited repair heuristic).
The increasing worldwide competition requires economical manufacture, high quality and short delivery time. The Just-In-Time (JIT) philosophy of manufacturing is increasingly being considered by manufacturing organizations, as a response to the increased pressure to supply high quality products with short delivery times and at low cost. A very simple shop floor control system that was developed by Toyota in the 1970s specifically for their Just-In-Time assembly plant, has received considerable attention in the Western World, and is known as the 'kanban' system (literally translated as 'card' system). Japan's success has prompted many scholars and practitioners, to turn their attention to Japanese management practices. This article is to address the modelling, simulation and implementation issues of Just-In-Time in flexible manufacturing environments. Priority nets are used for modelling and analysis of the kanban system. A large number of simulation runs are conducted/presented to probe the behaviour of the system, with respect to different parameter changes.
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