Robust balancing of straight assembly lines with interval task times [star] (original) (raw)

Balancing straight and U-shaped assembly lines with resource dependent task times

International Journal of Production Research, 2011

The basic assumption of assembly line balancing is that every task's time is fixed. However, in practice, different processing alternatives may be available to process a task with different times. The problem in this case is to assign tasks and resources to work stations that minimise total cost and so-called resource dependent assembly line balancing (RDALB) in the literature. This study proposes a new integer programming formulation for RDALB. This formulation is then modified to develop a formulation for RDULB problem in U-shaped assembly lines. To the best knowledge of the authors, this study is the first RDULB study and the developed formulation is the first RDULB formulation. The proposed formulations are illustrated and validated using several examples. An experimental analysis is also conducted to examine the percent improvement in total cost when the line layout is switched into the U-shaped from the straight line shape. Experimental results show that an improvement in total operating cost is obtained when the straight line is switched into the U-shaped line configuration. Results also show that percentage improvement in total operating cost is significantly greater for problem instances having a large number of tasks and having greater values for the strength of the precedence relationships among tasks.

Balancing and scheduling tasks in assembly lines with sequence-dependent setup times

European Journal of Operational Research, 2008

The classical Simple Assembly Line Balancing Problem (SALBP) has been widely enriched over the past few years with many realistic approaches and much effort has been made to reduce the distance between the academic theory and the industrial reality. Despite this effort, the scheduling of the execution of tasks assigned to every workstation following the balancing of the assembly line has been scarcely reported in the scientific literature. This is supposed to be an operational concern that the worker should solve himself, but in several real environments, setups between tasks exist and optimal or near-optimal tasks schedules should be provided inside each workstation. The problem presented in this paper adds sequence-dependent setup time considerations to the classical SALBP in the following way: whenever a task is assigned next to another at the same workstation, a setup time must be added to compute the global workstation time. After formulating a mathematical model for this innovative problem and showing the high combinatorial nature of the problem, eight different heuristic rules and a GRASP algorithm are designed and tested for solving the problem in reasonable computational time.

A decomposition based solution algorithm for U-type assembly line balancing with interval data

Computers & Operations Research, 2015

Balancing U-type assembly lines under uncertainty is addressed in this research by formulating robust problem and developing an optimization model to design assembly lines that hedge against disruptions. U-type assembly layouts are shown to be more efficient than conventional straight lines. A great majority of the studies on these production systems assume deterministic environments and ignore uncertainty, such as the variations in operation times. We aim to fill this research gap and to the best of our knowledge, this study will be the first application of robust optimization to U-type assembly planning.

Assembly line balancing under uncertainty: Robust optimization models and exact solution method

This research deals with line balancing under uncertainty and presents two robust optimization models. Interval uncertainty for operation times was assumed. The methods proposed generate line designs that are protected against this type of disruptions. A decomposition based algorithm was developed and combined with enhancement strategies to solve optimally large scale instances. The efficiency of this algorithm was tested and the experimental results were presented. The theoretical contribution of this paper lies in the novel models proposed and the decomposition based exact algorithm developed. Moreover, it is of practical interest since the production rate of the assembly lines designed with our algorithm will be reliable as uncertainty is incorporated. Furthermore, this is a pioneering work on robust assembly line balancing and should serve as the basis for a decision support system on this subject.

Comparative Analysis of Different Heuristics for Cost Oriented Assembly Line Balancing Problems

Abstract— Assembly line balancing problem consists of a finite set of tasks, where each of them has a duration time and precedence relations, which specify the acceptable ordering of the tasks. Line balancing is an attempt to locate tasks to each workstation on the assembly line. The basic ALB problem is to assign a set of tasks to an ordered set of workstations, so that the precedence relationships were satisfied, and performance factors were optimized. This paper shows the comparison of different heuristics for cost oriented assembly line balancing problem which has been taken from literature. Comparison is done on the basis of their smoothness index, cost and line efficiency. The computational results show that the proposed heuristic performs better and minimizes the production cost.

Assembly line balancing with task division

2019

In a commonly-used version of the Simple Assembly Line Balancing Problem (SALBP-1) tasks are assigned to stations along an assembly line with a fixed cycle time in order to minimize the required number of stations. It has traditionally been assumed that the total work needed for each product unit has been partitioned into economically indivisible tasks. However, in practice, it is sometimes possible to divide particular tasks in limited ways at additional time penalty cost. Despite the penalties, task division where possible, now and then leads to a reduction in the minimum number of stations. Deciding which allowable tasks to divide creates a new assembly line balancing problem, TDALBP (Task Division Assembly Line Balancing Problem). We propose a mathematical model of the TDALBP, an exact solution procedure for it and present promising computational results for the adaptation of some classical SALBP instances from the research literature. The results demonstrate that the TDALBP som...

An improved mathematical program to solve the simple assembly line balancing problem

International Journal of Production Research, 2009

The Simple Assembly Line Balancing Problem (SALBP) has been extensively examined in the literature. Various mathematical programs have been developed to solve SALBP type-1 (minimizing the number of workstations, m , for a given cycle time, ct) and SALBP type-2 (minimizing ct given m). Usually, an initial pre-process is carried out to calculate the range of workstations to which a task i may be assigned, in order to reduce the number of variables of task-workstation assignment. This paper presents a more effective mathematical program than those released to date to solve SALBP-1 and SALBP-2. The key idea is to introduce additional constraints in the mathematical program, based on the fact that the range of workstations to which a task i may be assigned depends either on the upper bound on the number of workstations or on the upper bound on the cycle time (for SALBP-1 and SALBP-2, respectively). A computational experiment was carried out and the results reveal the superiority of the mathematical program proposed.

Literature review of assembly line balancing problems

The International Journal of Advanced Manufacturing Technology, 2014

Mass production system design is a key for the productivity of an organization. Mass production system can be classified into production line machining a component and production line assembling a product. In this paper, the production line assembling a product, which is alternatively called as assembly line system, is considered. In this system, balancing the assembly line as per a desired volume of production per shift is a challenging task. The main objectives of the assembly line design are to minimize the number of workstations for a given cycle time (type 1), to minimize the maximum of the times of workstations for a given number of workstations (type 2), and so forth. Because this problem comes under combinatorial category, the use of heuristics is inevitable. Development of a mathematical model may also be attempted, which will help researchers to compare the solutions of the heuristics with that of the model. In this paper, an attempt is made to present a comprehensive review of literature on the assembly line balancing. The assembly line balancing problems are classified into eight types based on three parameters, viz. the number of models (single-model and multi-model), the nature of task times (deterministic and probabilistic), and the type of assembly line (straight-type and U-type). The review of literature is organized as per the above classification. Further, directions for future research are also presented.

Robust U-Type Assembly Line Balancing Problem: A Decomposition Based Approximate Solution Algorithm

17th International Working Seminar on Production Economics

We investigate balancing U-type assembly lines under uncertainty. We formulate the robust problem and develop an optimization model to design lines that hedge against disruptions. Offering more alternatives to group the operations, U-type assembly layouts are shown to be more efficient than conventional straight lines. As a result, they have been widely investigated in literature. However, a great majority of the studies assume deterministic environments and ignore various sources of uncertainty, like variability in operation times. We address this research gap.