At the beginning of assembly industry, the popular type of multi-variety production and short run batch quantity production is facing customers’ different requirements. But in the practice of the production and operation process, the large quantity flowing production’s efficiency is very high. This style is also the important tool to face the market competition at that time. The total process is divided into a lot of procedure station which is work station.
Each of which is distributed with a lot of short operations. Every center can be done by less proficient workers or by automatic convey belt. The parts can be conveyed to the next center after the operation or assembly. Each worker has a role to run alone or some workers can work in group to accomplish their duty. And they are not allowed to transfer or leave their locations unless authorized. Production line was one of trend at that time.
The procedure for creating work station of production line and assign tasks to them is call line balancing. Each production line has one special configuration which is depend on the product, infrastructure of company and so on, that is why we have amount kind of production line. And the first problem of production line which many authors faced is line balancing.
This problem attracts them to solve it during recent decades.
In designing repetitive flow process, we have to divide the whole process into element task; each of them will present a separate of works. For each task, it is necessary to estimate how long it takes to perform it. This estimate time may be based on experimentation or established work standard. Furthermore, these times depends on the several factors such as the number of people who are working at station, employee skill and motivation, and their supporting equipment and resource. Generally, the task time usually analysis with the assumption of standard time which is time of average worker with reasonable support equipments.
Along with the estimated time, the precedence requirement for each task has to determine by designer. Although, all products require essentially the same process in the same sequence, at the design step, there is some flexibility in the each sequencing of tasks. The precedence requirements specify which task must be complete before another task can be
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started. In the whole precedence requirement describes which task must be done sequentially and which could be done concurrently.
Other many other authors also try to find the solution for this problem. First of all, Jay van Zyl and A J Walker (2001) based on experience to get an empirical approach to balance features across product lines. In their paper, criteria were set up for the production line and rely on their experience to find the best choice for production line. Furthermore, some authors have been researched other methods such as using methodology, genetic algorithm, ant algorithm to balance production line. Liya Gu, Sophie Hennequin, Alexandre Sava and Xiaolan Xie (2007) proposed an new algorithm based on an estimation of distribution to solve one special kind of assembly line balancing problem. The type II assembly line balancing problem have been solved and given number of workstations so that the cycle time is minimized and the precedence constraints between the operations are satisfied. Bai Ying, Zhao Hongshun, and Zhu Liao (2009) used the Hybrid Genetic Algorithm to balance the Mixed-model Assembly Line Balancing. Zhang RuiJun ,Chen DingFang , Wang Yong, Yang ZhongHua , and Wang XinXin (2007) have studied on Line Balancing Problem Based on Improved Genetic Algorithms. In this paper, a feasible solution was brought forth for ALB-2 problem by designing an improved genetic algorithm, in which fitness, selection strategy, probability of crossover and mutation are improved. The platform is achieved with PowerBuilder as a development tool; architecture and main data structure for the platform are also given. The platform can be migrated smoothly for its rational set of database and data structure. The one case of special production line, bin packing, also has been solved by E.Falkenauer, ADelchambre (1992) by using genetic algorithm. The other algorithm, Ant Colony Algorithm, also use to balance Parallel Assembly Lines is introduce by Adil Baykasoglu', Lale OzbakIr, Latife Gorkemli, Beyza Gorkemli (2009). In this paper, an ant colony optimization based algorithm is proposed for balancing multi product parallel assembly lines. The proposed ant colony based algorithm is also the first soft computing approach for solving the present problem which is known as a NP-hard problem.
The assembly line balancing problems in simple form have been analyzed by a number of researchers, and about ten or so major algorithms have been developed for determining either the exact or an approximate balance. The problems in simple form attempt to minimize the number of operators for a given cycle time or to minimize the cycle time for a given number of operators with the assumptions that the element times are deterministic, that an element may be performed at any station, that only one uniform product is made, that the operator performance does not vary during the working period or from station to station, that
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group size or cycle time has no significance on line performance, and that balancing is independent of learning of operators and the quality level of parts and equipment.
How to balance for some kinds of line is other problem of line balancing. These are some special kinds of production line such as the U-shape line, hybrid assembly line, mix model assembly line, flexible assembly systems, and so on. For U-shape assembly line, there are two algorithms used to solve this problem, Genetic Algorithm and Heuristic approaches because, the U-shape layout is different from the traditional layout. The traditional assembly line balancing, the manufacturing process of a product is specified in terms of a sequence of tasks that need to be assigned to workstations. In contrast, The U-shaped assembly line balancing problem is a relatively new problem derived from the traditional assembly line balancing problem. The U-shaped assembly line is an attractive alternative for assembly production systems since operators (workers) become multi-skilled by performing tasks located on different parts of the assembly line. Moreover, since the U-shaped line disposition allows for more possibilities on how to assign tasks to workstations, the number of stations needed for a U-shaped line layout is never more than the number of stations needed for the traditional straight line. Debora A. Ajenblit Roger L. Wainwright (1998) applied genetic algorithm to this kind of assembly line. This research provides a framework which can be used to deal with the two possible variations of U-shape assembly line, minimizing total idle time, and balance of the workload among stations, or a combination of both. They found the results each of these assignment algorithms proved to have merit. The results show our GA to be an excellent technique for this problem. In the 61 standard test cases, our GA obtained the same results as previous researchers in 49 cases, superior results in 11 cases, and in only one case did worse. Similarly, Ulises Martinez and William S. Duff (2004) solved the U-shaped line balancing problem by heuristic approaches. The paper address the another kind of U-shaped line. And these heuristic approaches compared with the optimal of near optimal solutions. These results also showed that some very simple heuristic rules produced the good solution. With the simple implementation of a genetic algorithm it is possible to sometimes obtain optimal solutions in the first iteration.
B. Rekiek and A. Delchambre (2001) described another kind of production line Hybird Assembly Line. In many assembly lines the operations can be executed either manually, by robots or by hard automated equipments. These lines are called hybrid assembly lines. To balance this kind of assembly line, many kind of algorithm is used. The authors use a grouping genetic algorithm to tackle the problem and hybridized with a branch and cut algorithm and a multi-criteria decision-aid method. Finally, this method was illustrated by one
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case study. In addition, the architecture of the proposed model shows how to incorporate industrial features in the algorithm.
Recently, the mix-model assembly line is one of conspicuous problem to authors as well as companies. The mixed model assembly line is a more complex environment in which several variants (kind) of the product, referred to as models, are assembled simultaneously on the line. The line balancing problem in a mixed model environment involves the assignment of tasks of all models to the workstations. S.M.J Mirzapour AI-e-hashem 1, M.B Aryanezhad 2, H. Malekly 3, S.J. Sadjadi (2009) try to figure out some key point of this problem. In this paper, a common assumption in on mixed model assembly line balancing problem is that the task duration is known and deterministic but may differ among various models. The authors presented a robust optimization formulation to dealing with take duration uncertainly in a mix model assembly line balancing problem in which task can vary in a specific range.
Aiming to understand more about the line balancing as well as the application of its.
There are some paper sum up all of the conceptions and applications. J. Driscoll, D.
Thilakawardana introduced the definition of assembly line balancing difficulty and evaluation of balance solution quality. Author show the potential for a leaning approach, selection models to suit problems using the measures of difficulty. One of software, Assembly Line Management, was introduced which analysis the line balancing efficiency as well as pre-line balancing precedence can diagram. Finally, it can simulate the production pre-line and parameter of line. This software package for line balancing used existing heuristics and a learning approach to find the adequate solutions in under development and benefit from the new problem assessment measures. The use of genetic algorithm approach to balancing has shown considerable promise when use on some test cases problem or studying as well as researching.
During my dissertation, I will concentrate on how to design of production line. The first requirement is understand clear about the current situation. One of paper is close which the this case is Research on Assembly Line Balance of Jiu Wei Mechanical and Electronics Enterprise Base on the standard time, Yan Xu Qun Liu (2009). This paper introduces the theory of assembly line balance and researches the production system and assembly line balance emulation issues. The key enterprise—Jiu Wei Mechanical and Electronic Enterprise is the work-shopping, making to stock and export. Relying on advantageous technology, experience in administration, diversified product, thick funds, upper commerce prestige, these invested company, represented by the studied company in this paper, have grasped profit in developing countries by using cheap labor force and resources.
19 2.2 Grouping problem
Grouping problem is known as the other name, Group Technology, which is old concept based on principle that products have similar characteristics or requires similar processing will be gathered into group which is called families part. Their similarities can be exploited in many areas of production, including product design, process design layout and scheduling. One of simple group of parts family is shown in the figure 2.1. All parts in the figure have same processing of making hole in the center of part. This definition has been introduced by Gombinski (1968) and John L. Burbidge, Heinemann (1975) which was initial introduction of Group Technology. Sunderesh S. Heragu (1994) provided a thorough survey of papers on group technology and cellular manufacturing system design. There are some lessons about Group Technology summarized by Production Engineer Journal (1980).
Furthermore, the benefit of Group Technology also showed in this journal in order to introduce the new concept in Industrial Engineering. Recently, this methodology has been studied and researched by Asian authors such as Yanhai Hu, Feifan Ye, Zhimei Fang (2000).
They are looking for the integration of Lean Production and Group Technology aim to find the benefit of this manufacturing system and to understand it is either suitable for Asian Industry or not. This can be seen that by contrast to traditional production method, LP based on GT will shorten production cycle, reduce particular checking process, lower inventory, improve product quality, and cut product cost down. The implement of Group technology can get the biggest benefits of the whole company.
Figure 2. 1 Group of parts family
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The group technology principle is based on many other technologies, such as computer-aid-design (CAD) and cellular manufacturing. To implement Group Technology, first procedure is assigned the numerical code for each part that can describe its character.
This procedure is to make the grouping process more convenience and easy. The application of Group Technology can find in some papers to proof the benefit of this methodology. J. D.
Tedford and T. J. Ferris (1976) used this concept at the production planning phase of a new product. W. T. Whitfield (1972) applied Group Technology to Peterman Auto Components, of which 50% so grouped required only one operation for completion. He found that the small batches are optimum, quite large savings. Group Technology can use one medium to large batch components. During 70 decades, a consideration of work had been carry out by many authors in every field. For example, one special field - Plastic Moulding also applied Group Technology and it was introduced by C.C. Gallagher, T.J. Grayson, W. Colier and P.Moore.
Finally, GT can be use for scheduling jobs. Job within the same family parts not only requires the same type of processing on the same machines but also the machine setups are usually similar. They often use the same fixtures and components and they require the same human tasks and quality check. So, even within a job-shop process and certainly, similar job should be schedule to run successively whenever possible. This reduces the amount of spend time on setup and make the human activities more efficient and higher in quality. Mark T.
Leung, Rolando Quintana1, An-Sing Chen have proposed a general approach that can be used to assist the design of layout and to evaluate the quality of the layout plan with A Paradigm for Group Technology Cellular Layout Planning in Just-In-Time (JIT) Facility. Furthermore, Group Technology is one of tool to simplify the some scheduling problems. J.M. PROTH (1986) propose a way to reduce the amount of computation necessary for solving the scheduling problems in production management. In this paper, the author propose one algorithm able to decompose a production system into productions subsystems as independence as possible from the point of view of the short term management.
In addition, Group Technology also is a management philosophy that attempts to group products with similar design and/or manufacturing characteristics. This term have relative with Cellular manufacturing (CM), in other hand CM can be defined as an application of GT and involves grouping machines or processes on the basis of parts or part families they process. It is a relatively recent concept and has been applied in many manufacturing environments successfully. There are significant benefits that can be achieved as a result of implementing a Cellular Manufacturing System. A number of companies surveyed in have witnessed the following:
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• Setup time reduction
• Work-in-process inventory reduction
• Material handling cost reduction
• Equipment cost and directed and undirected labor cost reduction
• Improvement in quality
• Improvement in material flow
• Improvement in machine utilization
• Improvement in space utilization
• Improvement in employee morale
The main difference between a traditional job shop environment and a cellular manufacturing environment is in the grouping and layout of machines. In a job shop environment, machines are typically grouped based on their functional similarities. On the other hand, in a cellular manufacturing environment, machines are grouped into cells so that each cell is dedicated to the manufacture of a specific part family. Typically, machines in each cell are dissimilar in their functions. Such an arrangement in which sets of machines are dedicated to specific part families allows easier control of a CMS. To understand clearly with detail, Cellular Manufacturing system is introduced in the next section.
2.3 Cellular Manufacturing System (CMS)
Cell Manufacturing is a manufacturing approach that challenges the traditional Job Shop approach for a organizing a factory. In traditional Job shop, manufacturing system is organized by process or production layout. When a product is manufactured it usually built in a large batch which is then routed thought each of station, finally move to the stock. Therefore, under the traditional Job Shop system components and products are continuously manufactured in excess and at the wrong times. This approach creates excessive Work in Process (WIP) inventory and lengthy manufacturing lead-times. To understand about Cellular Manufacturing, one survey was held in 1976 by R. D. Pulled with the help of London Business School of 99 cells in 14 companies in the mechanical engineering field. He found that there is reason to be optimistic about the continued and wide application of Cellular Manufacturing System. It also showed that with the industry having such a poor delivery performance some more use to be made of the cell system to improve the situation and that the applications be organized. D.J. Stockton, R.J. Lindley and N. Bateman (1994) consider the
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problems involved in implementing such as a system. One series of benefits of cell was found in that application. So, Cellular Manufacturing is one trend of industry and a crucial topic.
Figure 2. 2 Arrangement of cells in a cellular manufacturing system
Cellular Manufacturing is not a product-orientated approach. Manufacturing facilities are organized to build specific products or families or products in work cells. These work cells are design to be product focused and arranged to contain each of resources necessary such as machines, people, tools, etc… to build a product or product family to complete from start to finish. If a product can be built completely in the same cell, this cell is called a
“Product Cell”. This is the simple definition of Cellular Manufacturing. We can see one critical example in the IBM about the “Going Cell”. Thomas Conway (2003) described the introduction of Cellular Manufacturing with some detail such as parts and product flow, optimization, cellular model, implementation and so on. The figure 2.2 is one example of cell layout which was mention in this paper. In this layout, the machine is grouped to become cell, and the part is processed by each cell.
Company can benefit when they convert even small proportion of their job-shop to work cells. When companies can convert a majority to cellular form, the saving can be enormous due to the advantage of Cellular manufacturing. W. P. McLaughlin introduces the Cellular Manufacturing at Bomford Turner. Many aspects were described such as Cellular Manufacturing implementation, Manufacturing Strategy, managing of the change.
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Cell manufacturing has definite benefit for the company in current market. One cell operates like an independence business with total responsibility for quality, processing and delivery product to customers. More than that, every cell has resource within their tool to
Cell manufacturing has definite benefit for the company in current market. One cell operates like an independence business with total responsibility for quality, processing and delivery product to customers. More than that, every cell has resource within their tool to