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There has been a high level of research activity on how to determine the optimal AS/RS dwell-point strategy. One could presume that research activity in this area is high because it is believed that the dwell-point location of the S/R machine (when idle) greatly affects the system response time. However, it is hypothesized that the difference between the performance of optimal versus simple dwell-point strategies is marginal for systems where the response time needs to be minimized (i.e. when the system is highly utilized) due to limited opportunities to travel to a dwell-point. Therefore, several dwell-point strategies are investigated here through the use of simulation. It is concluded that the dwell-point strategy has an insignificant impact on the relative system response time when the system is highly utilized (i.e. the percentage reduction is typically <2% and no more than 5% for highly utilized systems) and has an insignificant impact on the absolute response time (i.e. <10 s) for typical systems of any utilization level.

Job shop scheduling problem is well known NP-hard problem, this problem is difficult to find the good solution but industrials require the solution to competition and survive in the market. This paper focuses on developing algorithm to solve job shop scheduling problem. The new algorithm is called Future Makespan Heuristic. The concept of new algorithm is jobs are evaluated the makespan before selection one job to the schedule. Each iteration of selection, the new makespan is less than or equal to the makespan of the previous iteration. Iteration makes decision tree by using the candidate jobs (available jobs). Each branch of tree, the candidate jobs are evaluated the makespan by using basic heuristic such as dispatching rules. By this technique, the makespan is improved for all time of scheduling. The experiment reveals the solution is highly improved when comparing with original dispatching rules. Moreover, the computation time of new algorithm is short. The mathematic proof shows that the new algorithm can find the high quality solution in polynomial time algorithm if the evaluating procedure is polynomial time algorithm.

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