International Journal of Advanced Manufacturing Systems Volume 2 G Number 1 G January-June 2011 G pp. 67-71 International Science Press I J A M S Heuristic Approach for Assembly Line Balancing Problems T. B. Kathoke 1, J. V. L. Venkatesh 2 and R. K. Waghchore 3 Assembly line balancing or simply line balancing is problem of assigning operation to workstations along assembly line in such a way that assignment is optimal in some sense. This paper describes Heuristic approach for software development for assembly line balancing which is never to real life problem in the sense that resources on workstation are explicitly considered. The main objective of any assembly line balancing software is to assign task to workstation so that precedence constraints and cycle time constraints are not violated. This work adds resource constraints to the problem. From the information of resource and zone requirement for different tasks and availability on workstations, it is decided which task is assignable to which workstation and problem is solved by largest candidate rule so that resource constraints, precedence constraints and cycle time constraints are not violated. 1. INTRODUCTION THE goal of assembly line designed is to create a smooth, continuous flow along assembly line with a minimum at each workstation. A well balanced assembly line has the advantage of high personnel and facility utilization and equity among employees work load. Its terminology is assembly line balancing problem. The assembly line balancing problem is how to group the assembly activities, which have to perform in an assembly task, then, put them into workstation, so that the total assembly time required at each workstation is approximately same. The cycle time of the assembly line is determined by workstation with maximum total assembly time. The main objective of assembly line balancing software is to assign task to workstation so that precedence constraints and cycle time constraints are not violated [2]. This work adds resource constraints to the problem, which is not considered explicitly in any literature. The optimization method are lengthy, time consuming and cumbersome while heuristic method are simple and faster [5]. This paper describes case study computation by largest candidate rule. The installation of an assembly line is a longterm decision and usually requires large capital investments. Therefore, it is important that such a system is designed and balanced so that it works as efficiently as possible. Besides balancing a new system, a running one has to be re-balanced periodically or 1, 3 Assistance Professor, Department of Mechanical Engineering, J.D.I.E.T, Yavatmal-445001, India, (t_kathoke@yahoo.co.in) 2 Professors, Department of Production Engineering, S.G.G.S Institute of Engineering and Technology, Nanded-431605, India.
68 International Journal of Advanced Manufacturing Systems (IJAMS) after changes in the production process or the production program have taken place [1, 3, 4]. To balance the line developed the software for assembly line balancing. 2. CASE STUDY COMPUTATION EXPERIMENT The Precedence which is selected in the study as shown in figure 6 consists of about fifteen tasks. Figure 1 Precedence Diagram The Table 1 shows task task times, zones and resources which are available for perform the operations and Table 2 shows stations with their zones and resources. Table 1 Task Table Task Code Resources Zones Time (min) Predecessors Task-01 Fixture-01 Left 0.2 0 Task-02 Fixture-02 Right 0.18 0 Task-03 Fixture-03 Left 0.35 1 Task-04 Fixture-04 Right 0.28 1 Task-05 Fixture-05 Left 0.12 2 Task-06 Fixture-06 Right 0.12 3 Task-07 Fixture-07 Left 0.15 3 Task-08 Fixture-08 Right 0.4 4,5 Task-09 Fixture-09 Left 0.21 5 Task-10 Fixture-10 Right 0.21 6 Task-11 Fixture-11 Left 0.41 8 Task-12 Fixture-12 Right 0.28 9 Task-13 Fixture-13 Left 0.18 7,11 Task-14 Fixture-15 Right 0.35 12 Task-15 Fixture-16 Left 0.28 13,14
HEURISTIC APPROACH FOR ASSEMBLY LINE BALANCING PROBLEMS 69 Table 2 Workstation Table Workstation Code Resources Zones Station-01 Fixture-01, Fixture-02, Fixture-03 Left, Right Station-02 Fixture-04, Fixture-05, Fixture-06 Left, Right Station-03 Fixture-07, Fixture-08, Fixture-09 Left, Right Station-04 Fixture-10, Fixture-11, Fixture-12 Left, Right Station-05 Fixture-13, Fixture-14, Fixture-15 Left, Right 2.1. According to Zone and Resources From the information of resource and zone requirement for different tasks and availability on workstations, it is decided which task is assignable to which workstation and problem is solved by heuristic method i.e. largest candidate rule is described below. 2.2. According to Largest Candidate Rule In this method, work elements are arranged in descending order according to their task time Assign elements to the worker at the first workstation by starting at the top of the list and selecting the first element that satisfy the precedence requirement & does not cause the total sum of task times at the station to exceed maximum allowable service time; when an element selected for assignment to the station, start back at the top of the list for subsequent assignment. When no more station element can be assigned without exceeding maximum allowable service time, then processed to the next station. Repeat steps above for the other stations in turn until all elements have been assigned [3]. The procedure of tasks assigns the works explained below with the help of flowchart. Figure 2 Flowchart
70 International Journal of Advanced Manufacturing Systems (IJAMS) From the Precedence Diagram it is observed that both task Task-01 and Task-02 are free tasks i.e. no predecessor. But the task time of Task-01 (0.2) is more than Task-02 (0.18) therefore Task-01 is assign at the top of the list of on station-01. While Assign The Task-01, Task-03 & Task-04 are get free but the zone and resources Task-04 is not found on Station-01 and Task-03 (0.35) has more Task time than Task-02 (0.18) therefore, Task-03 assigned first then Task-02 as shown below in Table 3. Repeat the Procedure for all workstation. 2.3. Cycle Time An assignment of each task to a station such that the precedence constraints and further restrictions are fulfilled the set Sk of tasks assigned to a station k (=1, m) constitutes its station load, the cumulated task time is called station time. When a fixed common cycle time c is given a line balance is feasible only if the station time of neither station exceeds c. In case of t (Sk) < c, the station k has an idle time of c t (Sk) time units in each cycle [3]. For example, Station 1 has a cycle time 1.85 min, which is the sum of the all tasks on station 1. It is observed that After comparing all workstations cycle time, the maximum cycle time is on workstation 1 i.e. 1.85 min, which is considered to be fixed common cycle time and idle time, cumulative idle time, total idle time calculated for all stations as shown in Table 3. Table 3 Largest Candidate Rule Station Code Task Code Predecessors Task Cycle Idle Cumulative Total Time Time Time Idle Time Idle Time Station-01 Task -01 0 0.2 0.73 0.17 0.17 Task-03 1 0.18 Task-02 0 0.35 Station-02 Task-04 1 0.28 0.52 0.38 0.55 Task-05 2 0.12 Task-06 3 0.12 Station-03 Task-08 4,5 0.15 0.76 0.14 0.69 0.78 Task-09 5 0.4 Task-07 3 0.21 Station-04 Task-11 8 0.21 0.9 0 0.69 Task-12 9 0.41 Task-10 6 0.28 Station-05 Task-14 12 0.18 0.81 0.09 0.78 Task-13 7,11 0.35 Task-15 13,14 0.28
HEURISTIC APPROACH FOR ASSEMBLY LINE BALANCING PROBLEMS 71 3. CONCLUSION This software can be applicable to any type of assembly line problem only if all the information about task and workstation known and can be used any personnel computer with user friendly interactive presentation, provision to store case studies [8, 9]. The future scope is that help facilities can be used to make software more user friendly thus reducing skill level of user and future modification is developed software by considering operating cost factor and utility function also. References [1] Becker C. and Scholl A. (2003), A Survey on Problem and Methods in Generalized Assembly Line Balancing European Journal of Operation Research. [2] Emanuel Falkenauer, Line Balancing in Real World. [3] Nil Boyser, Malte Fliendner, Armin Scholl (2006), Assembly Line Balancing: Which Model to Use When? Mikel P.Groover Automation, Production System and Computer Integrated A Manufacturing, Prentice-Hall India Limited, New Delhi, 1996. [4] Nils Boyser, Malte Fliendner, Armin Scholl (2006), A Classification of Assembly Line Balancing Problem. [5] PatricR. Mcmullen, Gregoryv.frazier (1997), A Heuristic for Solving Mixed Model Line Balancing Problem with Stochastic Task Durations and Parallel Station, Int J. Production Economics, 51, 177-190. [6] E. S. Buffa (1991), Modernproduction/Operation Management, Wiley Eastern Limited. [7] Mikel P. Groover (1996), Automation, Production System and Computer Integrated a Manufacturing Prentice Hall India Limited, New Delhi. [8] Mastering Visual Basic 6.0. [9] David I. Schreider, Computer Programming Concepts and Visual Basic, University of Phoenix (College of Information Systems and Technology).