ORIGINAL ARTICLE Optimization of process planning with various flexibilities using an imperialist competitive algorithm Kunlei Lian & Chaoyong Zhang & Xinyu Shao & Liang Gao Received: 21 April 2011 /Accepted: 10 July 2011 /Published online: 7 August 2011 # Springer-Verlag London Limited 2011 Abstract In this paper, we investigate the optimization of process planning in which various flexibilities are consid- ered. The objective is to minimize total weighted sum of manufacturing costs. Various flexibilities, including process flexibility, sequence flexibility, machine flexibility, tool flexibility, and tool access direction (TAD) flexibility, generally exist in process planning and consideration of these flexibilities is essential for improving production efficiency and system flexibility. However, process plan- ning is strongly NP-hard due to the existence of various flexibilities as well as complex machining precedence constraints. To tackle this problem, an imperialist compet- itive algorithm (ICA) is employed to find promising solutions with reasonable computational cost. ICA is a novel socio-politically motivated metaheuristic algorithm inspired by imperialist competition. It starts with an initial population and proceeds through assimilation, position exchange, imperialistic competition, and elimination. Com- putational experiments on three sets of process planning problem taken from literature are carried out, and compar- isons with some existing algorithms developed for process planning are presented. The results show that the algorithm performs significantly better than existing algorithms like genetic algorithm (GA), simulated annealing (SA), tabu search (TS), and particle swarm optimization (PSO). Keywords Process planning . Imperialist competitive algorithm . Genetic algorithm . Simulated annealing 1 Introduction Computer-aided process planning (CAPP) is a key component of computer integrated manufacturing system (CIMS). It links computer-aided design (CAD) and computer-aided manufac- turing (CAM) by transforming a part design into a set of machining instructions. This paper addresses the process planning problem in generative CAPP systems. An important feature of the generative system is its high degree of flexibility to adapt itself to multi-variety and small-batch production environments. Therefore, optimization of process planning with various flexibilities is essential for improving production efficiency as well as system flexibility. Generally, process planning is concerned with conducting two activities, namely, operation selection and operation sequencing, simultaneously. Operation selection refers to the act of selecting necessary operations to achieve machining features of a given part and determining relevant manufacturing resources for each opera- tion, while operation sequencing is the act of determining an optimized sequence of operations subject to the precedence constraints among operations. There exist a number of flexibilities with respect to these two activities of process planning: (1) During the phase of operation selection, a manufacturing feature can be achieved through different combinations of operations (process flexibility), and alterna- tive machines, tools, and tool access directions (TAD) may exist for each operation (machine flexibility, tool flexibility, and TAD flexibility). (2) During the phase of operation sequencing, different sequences of operations result in different process plans for the same part (sequence flexibility). Although many studies, including Li et al. [1], Kim et al. [2], and Seok Shin et al. [3], dealt with some or part of these process planning flexibilities, to the best of the authors’ knowledge, there is no existing study that comprehensively considered the impact of different flexibilities on the outputs of process K. Lian : C. Zhang (*) : X. Shao : L. Gao The State Key Laboratory of Digital Manufacturing Equipment and Technology, Huazhong University of Science and Technology, Wuhan 430074, People’ s Republic of China e-mail: zcyhust@mail.hust.edu.cn Int J Adv Manuf Technol (2012) 59:815–828 DOI 10.1007/s00170-011-3527-8