Multi-cycle and multi-product Integrated and two objectives model for Production Planning and maintenance considering storage capacity limitations and minimizing the work force changes approach

The problem of production planning and Maintenance is one of the most important decision in production industries and because of their interaction, it is necessary to be studied simultaneously. These two problems are sometimes studied separately that causes to lose ideal result. In this study, a two objectives model is presented for the problem of multi-cycle and multi-product Integrated Production Planning considering storage capacity limitations and Repair and Maintenance. The first objective is minimizing total cost elements that is a known objective in this field, and the second is minimizing work force changes. Although usually the cost of work force changes is considered as an element in total cost, but for some important factors such as social impact, continuous loss of knowledge and skills, and so on it is necessary to considered work force changes as an independent objective. So, at first problem definition via objective functions, parameters, and decision variables are presented. Then mathematical model in multi objective is developed. Since, this problem has been proved as NP-Hard, two approximation methods are also developed based on Non-dominated Sorting Genetic Algorithm II (NSGA-II) and Multi-Objective Imperialism Competitive Algorithm (MOICA). Finally in order to analyze result, this problem is solved with standard data obtained from references. The result show good performance of MOICA in comparison to NSGA-II. However time solution of NSGA-II is better than MOICA.