Contents lists available at ScienceDirect Journal of Manufacturing Systems journal homepage: www.elsevier.com/locate/jmansys Technical Paper Automated fexible transfer line design problem: Sequential and reconfgurable stages with parallel machining cells Cong He a , Zailin Guan a , Yeming Gong b , Chuangjian Wang c , Lei Yue a, ⁎ a State Key Laboratory of Digital Manufacturing Equipment and Technology, School of Mechanical Science and Engineering, Huazhong University of Science and Technology, Wuhan, Hubei, China b EMLYON Business School, Ecully, France c School of Machinery and Automation, Wuhan University of Science and Technology, Wuhan, Hubei, China ARTICLEINFO Keywords: Automated fexible transfer line Decomposition method Branch and bound Line design Cycle time ABSTRACT A novel production line with high automation, fexibility, reliability and reconfgurability, which is designed for the smart factory and named as automated fexible transfer line (AFTL), is studied in this paper. Diferent from the other production lines, AFTL consists of sequential and reconfgurable stages which are grouped by multiple machining cells, and each machining cell is composed of a single robot and several machines. This special line structure contributes to the complexity of the non-linear line cycle time relations, and the cost of the line contains the cost of machines, robots and stages. The aim is to balance and confgure the AFTL in minimal cost with a given line cycle time, which is equivalent to fnd the appropriate subsets of operations and assign each of them to the stage with an optimal confguration. Three novel and efcient lower bounds in diferent levels based on solving the set partitioning problem in AFTL design problem are presented and an efective algorithm is developed. The experimental results and case problem results prove that the proposed algorithm together with the lower bounds are efective and applicable for the industrial cases. 1. Introduction and motivation Most of the new factory concepts share attributes of smart net- working [1]. Thus, to consider the manufacturing system as cyber- physical system (CPS) has become a crucial and timely topic. CPS often incorporates elements from both information and material subsystems which are integrated and decisions in them are cohesive [2]. In addi- tion, such systems evolve through adaptation and reconfguration of their structures, that is through structure dynamics [3,4]. Smart fac- tories Industry 4.0 on the basis of CPS represents a future form of in- dustrial networks, and Industry 4.0 represents a smart manufacturing networking concept where machines and products interact with each other without human control. Dynamics in manufacturing system, such as product change, demand fuctuation, uncertainty in machine failure, etc., have challenged the manufacturing system structure. This requires a dynamic manufacturing structure which can be quick response to the change of environment, which is regarded as an opportunity for the current research. Manufacturing systems are often designed and optimized based on their product types and production volume requirements, and diferent types of production lines have been used in diferent situations based on their features. Nowadays, product cycle has become shorter and shorter, especially for the electronic products. Products are changed generations by generations, and consumers will buy the available pro- ducts with high quality, since most of products are alternative. Thus, manufacturers have to produce one new kind of product in high volume due to the heavy demand in sudden, and at same time provides the ability to produce diferent kinds of products. Meanwhile, producing with high quality and high reliability are also important factors which must be considered. Under the consideration of potential failures caused by the humans and the times it takes in learning skills, using robots and automatic equipment is a trend. However, a production line for a given product family is a signifcant investment, and to design an intelligent and reliable manufacturing system is critical for most man- ufacturers. Since machining tandem line (transfer line) is often used in the automotive industry [5,6], this paper provides a choice to the manufacturers by designing a transfer line with high fexibility, relia- bility and reconfgurability, which satisfes the requirements above and named as automated fexible transfer line (AFTL), is introduced. Dif- ferent from other transfer lines, the proposed AFTL has the following advantages: https://doi.org/10.1016/j.jmsy.2019.05.005 Received 24 August 2018; Received in revised form 2 January 2019; Accepted 11 May 2019 ⁎ Corresponding author. E-mail address: leileyok@hust.edu.cn (L. Yue). Journal of Manufacturing Systems 52 (2019) 157–171 Available online 19 July 2019 0278-6125/ © 2019 The Society of Manufacturing Engineers. Published by Elsevier Ltd. All rights reserved. T