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Because the alternative process plans have significant contributions to the production efficiency of a manufacturing system, researchers have studied the integration of manufacturing functions, which can be divided into two groups, namely, integrated process planning and scheduling (IPPS) and scheduling with due date assignment (SWDDA). Although IPPS and SWDDA are well-known and solved problems in the literature, there are limited works on integration of process planning, scheduling, and due date assignment (IPPSDDA). In this study, due date assignment function was added to IPPS in a dynamic manufacturing environment. And the studied problem was introduced as dynamic integrated process planning, scheduling, and due date assignment (DIPPSDDA). The objective function of DIPPSDDA is to minimize earliness and tardiness (E/T) and determine due dates for each job. Furthermore, four different pure metaheuristic algorithms which are genetic algorithm (GA), tabu algorithm (TA), simulated annealing (SA), and their hybrid (combination) algorithms GA/SA and GA/TA have been developed to facilitate and optimize DIPPSDDA on the 8 different sized shop floors. The performance comparisons of the algorithms for each shop floor have been given to show the efficiency and effectiveness of the algorithms used. In conclusion, computational results show that the proposed combination algorithms are competitive, give better results than pure metaheuristics, and can effectively generate good solutions for DIPPSDDA problems.

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Traditionally process planning, scheduling, and due-date assignment functions are applied sequentially and separately. Since these three functions affect each other and if we don't integrate, then they will become poor input for downstream and overall performance will be poor. In this competitive era, we must be competitive also. Integrating these functions will improve overall performance. In this study, we investigated the benefit of integration. We tested different integration level. First, we looked at unintegrated results and later step by step three functions are integrated and finally, we integrated these two functions with WATC (Weighted Apparent Tardiness Cost) Dispatching. In this study, we observed that as integration level increases the solution becomes better. Integrating due-date assignment or scheduling with process planning improves overall performance and if we integrate WATC dispatching with these two functions then we get the best performance. In addition to integration levels, we also compared the benefit of search techniques, especially genetic (directed) and hybrid (semi-directed) searches. At this study every customer has weight and they are scheduled by considering weights to improve performance value.

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