SIMULATION MODELING AND ANALYSIS OF PRODUCTIVITY ENHANCEMENT IN MANUFACTURING COMPANY USING ARENA SOFTWARE SITI HARTINI BINTI AB WAHAB

Transcription

1 SIMULATION MODELING AND ANALYSIS OF PRODUCTIVITY ENHANCEMENT IN MANUFACTURING COMPANY USING ARENA SOFTWARE SITI HARTINI BINTI AB WAHAB Thesis submitted in fulfillment of the requirements for the award of the degree of Bachelor of Engineering in Manufacturing Faculty of Manufacturing Engineering UNIVERSITI MALAYSIA PAHANG JUNE 2013

2 vii ABSTRACT Every manufacturing company wants to improve and adapt their operating system in order to survive the industry competition. In manufacturing organizations, to improve their system it might mean to reduce the operating costs that come from the wastes in production line. By using the ARENA simulation in this study, the productivity improvement can be experimented without physically affect the real system and reduced the cost because designing, building, testing, redesigning, rebuilding and retesting can be an expensive project. This study focus on the flow in the production line processes in one piston manufacturing company. The existing plant layout was studied and formulated into ARENA simulation software as well as to enhance the productivity rate by improving certain parameters. The problems identified in this production line are the effect of the bottleneck process which resulting some idle time in some workstations and the increased piston demands from the customers. The data acquired and was translated into the ARENA simulation software and studied in order to simulate the existing plant layout design. Hence, the problems occurred in the production line can be seen clearly to determine room for productivity improvement. New designs are proposed by constructing several models to acquire the best solution to improve productivity capacity and meet the forecasting demand of customer. In these proposed models, the parameters of the actual system are modified accordingly in the terms of material handling such as human resources, machine cycle time, the number of machines, shape and area of plant layout. From the simulation results, the significant contribution factor that influenced the rate of productivity was by adding certain machines to do the same process to cover the buffer while the material handling did not have a huge effect on the production line.

3 viii ABSTRAK Setiap syarikat pembuatan ingin memperbaiki dan menyesuaikan sistem operasi mereka untuk terus bersaing dalam industri yang mencabar ini. Bagi organisasi pembuatan, untuk memperbaiki sistem mereka, ia bermakna, mereka mesti mengurangkan kos operasi yang tidak bermanfaat. Tumpuan kajian ini adalah untuk mendalami aliran dalam proses pengeluaran dalam syarikat pembuatan omboh. Susun atur kilang yang sedia ada dikaji dan ditafsirkan ke dalam perisian simulasi ARENA untuk meningkatkan kadar produktiviti dengan meningkatkan parameter tertentu. Antara masalah-masalah yang dikenal pasti dalam pengeluaran ini adalah kesan akibat kesesakn proses tertentu yang menyebabkan masa terbiar di beberapa stesen kerja dan juga permintaan omboh sentiasa meningkat daripada pelanggan. Data yang diperolehi akan dikaji dan diterjemahkan ke dalam perisian simulasi ARENA untuk simulasi reka bentuk susun atur kilang yang sedia ada. Oleh itu, masalah-masalah yang berlaku dalam proses pengeluaran dapat dilihat dengan jelas dan kawasan di mana peningkatan produktiviti yang boleh dibuat dapat ditentukan. Reka bentuk baru dicadangkan dengan membina beberapa model untuk memperoleh penyelesaian terbaik bagi meningkatkan keupayaan produktiviti dan memenuhi ramalan permintaan daripada pelanggan. Bagi model cadangan, parameter sistem sebenar diubahsuai dengan sewajarnya seperti pengendalian bahan seperti sumber manusia, masa kitaran mesin, bilangan mesin, bentuk dan bidang susun atur kilang. Daripada laporan simulasi, faktor yang paling mempengaruhi kadar produktiviti penambahan mesin tertentu untuk melakukan proses yang sama bagi menampung kesesakan dalam pemprosesan, manakala, faktor pengendalian bahan tidak memberi kesan yang besar pada kadar pengeluaran produk.

4 ix TABLE OF CONTENTS EXAMINER APPROVAL DOCUMENT SUPERVISOR S DECLARATION STUDENT S DECLARATION DEDICATION ACKNOWLEDGEMENTS ABSTRACT ABSTRAK TABLE OF CONTENTS LIST OF TABLES LIST OF FIGURES LIST OF ABBREVIATIONS Page ii iii iv v vi vii viii ix xiii xiv xv CHAPTER 1 INTRODUCTION 1.1 Preface Background of Study Company Background Project Background Project Objectives Project Scopes Problem Statements 6 CHAPTER 2 LITERATURE REVIEW 2.1 Introduction Productivity Material Handling Facility Layout 10

5 x 2.5 Simulation Simulation Process Simulation Benefits Disadvantages of Simulation Application Areas Simulation Tools ARENA Simulation Software 17 CHAPTER 3 METHODOLOGY 3.1 Introduction Project Methodology 21 CHAPTER 4 RESULTS, ANALYSIS AND DISCUSSION 4.1 Introduction Data Collection Simulation Model Model 1 (Simulation of Actual Layout Design) Model 2 (Experimental Design) Model 3 (Experimental Design) Model 4 (Experimental Design) Model 5 (Experimental Design) Model 6 (Experimental Design) Model 7 (Experimental Design) Model 8 (Experimental Design) Model 9 (Experimental Design) 53 CHAPTER 5 CONCLUSION AND RECOMMENDATIONS 56 REFERENCES 59 APPENDICES A1 Gantt Chart For FYP 1 62 A2 Gantt Chart For FYP 2 63

6 xi B1 Production Plant Layout 64 B2 Plant Layout For Piston Machining Cells 65 B3 Capacity Study For Piston Model PN B4 Capacity Study for Piston Model CE B5 Example of Simulation Parameter (Process & Resource) 68 B6 Example of Simulation Parameter (Queue) 69 B7 Model 1 Animation (1 Hour Run) 70 B8 Model 1 Circuit (1 Hour Run) 71 B9 Model 1 Animation (1 Month Run) 72 B10 Model 1 Circuit (1 Month Run) 73 B11 Model 2 Animation (1 Hour Run) 74 B12 Model 2 Circuit (1 Hour Run) 75 B13 Model 2 Animation (1 Month Run) 76 B14 Model 2 Circuit (1 Month Run) 77 B15 Model 3 Animation (1 Hour Run) 78 B16 Model 3 Circuit (1 Hour Run) 79 B17 Model 3 Animation (1 Month Run) 80 B18 Model 3 Circuit (1 Month Run) 81 B19 Model 4 Animation (1 Hour Run) 82 B20 Model 4 Circuit (1 Hour Run) 83 B21 Model 4 Animation (1 Month Run) 84 B22 Model 4 Circuit (1 Month Run) 85 B23 Model 5 Animation (1 Hour Run) 86 B24 Model 5 Circuit (1 Hour Run) 87 B25 Model 5 Animation (1 Month Run) 88 B26 Model 5 Circuit (1 Month Run) 89 B27 Model 6 Animation (1 Hour Run) 90 B28 Model 6 Circuit (1 Hour Run) 91 B29 Model 6 Animation (1 Month Run) 92 B30 Model 6 Circuit (1 Month Run) 93

7 xii B31 Model 7 Animation (1 Hour Run) 94 B32 Model 7 Circuit (1 Hour Run) 95 B33 Model 7 Animation (1 Month Run) 96 B34 Model 7 Circuit (1 Month Run) 97 B35 Model 8 Animation (1 Hour Run) 98 B36 Model 8 Circuit (1 Hour Run) 99 B37 Model 8 Animation (1 Month Run) 100 B38 Model 8 Circuit (1 Month Run) 101 B39 Model 9 Animation (1 Hour Run) 102 B40 Model 9 Animation (1 Month Run) 103

8 xiii LIST OF TABLES Table No. Page 2.1 Simulation software that available on the market Piston models for customer NK Comparison between Actual System and Model Comparison between Actual System and Model Comparison between Actual System and Model Comparison between Actual System and Model Comparison between Actual System and Model Comparison between Actual System and Model Comparison between Actual System and Model Comparison between Actual System and Model Comparison between Actual System and Model The comparison of productivity capacity between the models and actual system 57

9 xiv LIST OF FIGURES Figure No. Page 2.1 The life cycle of a simulation study Model application window in ARENA simulation software Example of airport security application model Example of airport security application model simulation run Flowchart of project methodology Features of the piston model Critical features of the piston Overall piston production flow Piston machining process flow in Line Machining cell Line 4-4 and 4-5 layout The view of Model 1 in ARENA simulation The view of Model 2 in ARENA simulation The view of Model 3 in ARENA simulation The view of Model 4 in ARENA simulation The view of Model 5 in ARENA simulation The view of Model 6 in ARENA simulation The view of Model 7 in ARENA simulation The view of Model 8 in ARENA simulation The view of Model 9 in ARENA simulation 54

10 xv LIST OF ABBREVIATIONS BASIC C++ CAD CAM CNC DRB-HICOM FORTRAN KPI OEM Perodua Proton Edar REM VBA WIP Beginner s All-purpose Symbolic Instruction Code C with Classes (programming language) Computer-aided Design Computer-aided Manufacturing Computer Numerical Control Diversified Resources Berhad The Heavy Industries Corporation of Malaysia Berhad The IBM Mathematical Formula Translating System Key Performance Indicator Original Equipment Manufacturer PERusahaan Otomobil kedua PeRusahan OTOmobil Nasional Replacement Equipment Manufacturer Visual Basic for Applications Work In Progress

11 1 CHAPTER 1 INTRODUCTION 1.1 PREFACE This chapter will discuss on the background and rationale of this study. It also covers on research background which is significantly related to the project objectives, project scopes, and problem statements. 1.2 BACKGROUND OF STUDY Nowadays, the automotive industry in Malaysia is recognized as one of the freshest and provides most steadily growing markets, where it provides the world needs widely except for America and Continental Europe. Malaysia is stated as the third South-East Asian auto maker where it produced more than half a million vehicles over a year assisted by Japan and Korea. Proton Edar (PeRusahaan OTOmobil Nasional), Perodua (PERusahaan Otomobil kedua), and DRB-HICOM (Diversified Resources Berhad The Heavy Industries Corporation of Malaysia Berhad) are among the most notable automotive giants in Malaysia industry. Parallel with the growing and the establishment of the automotive industry, the automotive component industry also rapidly evolved in order to support and provide the industry with the automotive partial components. Because of that, the demand of automotive parts increased tremendously as the most of automotive parts; from small to large parts, and sophisticated parts have been localized for internal fabrication.

12 2 Consequently, many automotive components suppliers or vendors from Malaysia and foreign countries have placed a large sum of money to raise plants and support the automotive manufacturers in Malaysia and entrusted the local vendors to supply the automotive partial components to them. As the demand increased in automotive components, the companies are forced to determine the solution to increase their productivity in order to satisfy the customer requests. Various existed and fully developed techniques, methodologies and productivities strategies are available but yet still can be improvised to suit the current situation in order to determine the ultimate productivity approaches. Of course, as today's industries competitive, every company must create a quick but efficient decision to improve and adapt their operating system in order to survive the global challenges and be on top in their respective discipline. In manufacturing organizations, to improve their system it might mean to reduce the operating costs that come from the wastes in production line. Waste is defined as any activity that does not add any value to the products or services. The activity that does not add value to the products or services means that the client is not willing to pay more money for this activity. Waste can be viewed as the single obstacle that can define a business over time, unless they are identified and systematically wiped out. Waste elimination is one of the most effective ways to increase profitability in manufacturing. To eliminate waste, it is important to understand exactly what waste is and where it exists. While products differ in each factory, the typical wastes found in manufacturing environments are quite similar. Generally, there are 7 forms of wastes identified in lean manufacturing; overproduction, transportation, motion, waiting, processing, inventory and defects. This paper focus on the two of the forms; motion (people or equipment moving or walking more than is required to perform the processing) and waiting (waiting for the next production step). These wastes can be triggered by various factors such as incorrect plant layouts, lack of proximity of machines and waiting workers, machines and

13 3 materials. Plant layout design and material handling methods will be the main focal point of this study due to its large contribution in waste elimination. The plant layout is a very critical role in running an efficient and cost effective business. All work areas, production lines, material storage facilities, etc. should be designed to perform to its highest rate and the corresponding to the shortest cycle time. When designing a plant layout, it is necessary to take into account all the functions within the production plant. The pattern must include not only the needs for the present production levels but should also have provisions for future expansion. This is included to avoid frequent and costly changes to the design as demand increases. The efficient layout design is important for reducing the operations and management costs. The basic objective of layout is to ensure a smooth flow of work, material, and information through a system. Although, there are several indicators and objectives to the facility layout problem, the most commonly used objective is the reduction of material handling. Material handling is defined as the art and science of moving, packing, and storing of substances in any form. Material handling is a very vital component of the design and the needs of a manufacturing facility. Efficient material handling is important to manufacturing operations. Materials must be unloaded, moved through inspections and it needs to be properly stored and transferred to and from workstation/centers with a view towards minimizing the movement and avoiding harm to the merchandise. These motions do not add value to the product but they do add value to the production cost. The cost of this being implemented incorrectly could affect the profitability of the business and also could endanger the employees. In some instances special handling equipment may be necessary to ensure that the material is handled properly.

14 4 Nowadays, simulation studies are widely used for applications in engineering industry as a tool to increase the capacity of manufacturing and the profit of a company by avoiding the company making an error in building non-effective layouts and using wrong approaches. By the simulation also, the company can reduce the time needed to grow the plants and there is no try-and-error situation because through the simulation, all the details can be seen and examined thoroughly. As the proof, the simulation studies are widely used in manufacturing, material handling, delivery, business operations, and transportation as they has not only assisted in understanding the details of the processes, but the graphical modeling tools and animated run like those in ARENA simulation software, also ease the involvement of the management in the development and the decision making processes. In this paper, a simulation study using ARENA simulation software was conducted in order to overcome some of the problems at production line in a manufacturing factory, particularly the plant layouts, the waiting time at the various processes due to high cycle time at some stages and material handling. 1.3 COMPANY BACKGROUND This research will focus on the productivity on one of the automotive component vendors in Malaysia which produces and supplies car piston parts to the automotive manufacturers in Malaysia, and also the customer in foreign countries such as Japan and Europe. The piston is a one of the most important and critical components in car production which are installed in the engine transmission system, and plays a significant role as the key contribution to drive the car movement. Its efficiency can be judged by the movement driven by the combustion in a locomotive. This piston plant is located in Selangor and has been operated for about 30 years. They specialize in various kinds of gravity aluminum casting and machining parts. The plant also fabricates other automotive components such as piston pin, valve housing,

15 5 pinion housing, mounting brackets, compressor bracket, etc. They produce pistons for cars, trucks and motorcycles in which the plant runs the fabrication process from the beginning stage includes melting, casting, heat-treatment, machining, washing, coating and packaging. 1.4 PROJECT BACKGROUND This project focuses on the study of the flow in the piston production line processes in this automotive component vendor company. In this project, the first step to take is to examine the existing plant layout and the details before applying that layout design into the application of ARENA simulation software in order to simulate the plant layout design. This project is also aiming to develop a process flow simulation model of the existing plant layout to identify problems occurred in the production line and determine where the productivity improvement can be realized. The problems and wastes in the processes are investigated and analyzed. The application of ARENA simulation software enables the productivity problems occurred in the production floor being highlighted. Several new plant layout designs are developed to encounter the problems occurred in the original plant layout and simulated using ARENA simulation software. From the analysis and the simulation results, a summary of comparison between the design options is made to determine which option shows the best solution, and then, the best approach is selected as the best option to be implemented in the chosen company. 1.5 PROJECT OBJECTIVES 1. To study the existing production layout using ARENA simulation software in the automotive component vendor company that produces piston. 2. To improve the productivity by ameliorate the plant layout and material handling in the company by simulation using ARENA simulation software.

16 6 1.6 PROJECT SCOPES This project focuses on the productivity improvement of piston production processes in the automotive component company. To ensure the objectives are achieved, some of important elements must be considered. These are: a) Studying the production processes and present time study for the piston production processes. b) Study and applying ARENA simulation software in order to simulate the process flow in the piston production line. 1.7 PROBLEM STATEMENTS Nowadays, due to the continuous positive increment in the automotive market, the automotive component vendors also taking the heat as they are required to increase their productivity to meet the demands of the automotive manufacturers which are their clients. The designs and the demands of the components keep changing from time to time depends on the customer requirement and market situation. These conditions will lead to the tighten time frame to the production. In addition, many of automotive vendors racing with each other to improve their production technology and enhance the production rate as the outcome from the increase of production cost and competitiveness due to economic globalization. The outcome of these situations is there are many researches and developments have been performed to create and modified new equipment/machines, methods, and systems. One of the methods developed is system modeling by using simulation software, where in this study will be used ARENA simulation software. The main problem that occurred in this piston manufacturing line is that they are struggling to keep up with the demand for piston parts from customer NK. The constraint is on the production volume to meet the requirement by the delivery date fixed by this customer. In the year of 2012, an average of 2,500 sets of piston was

17 7 required per month for all Original Equipment Manufacturer (OEM) models and 1,000 sets for Replacement Equipment Manufacturer (REM) and this was done hardly on time. Currently, for the January 2013 order, with an increase on the figure of the new car models introduced, the customer increased the order by added the order for OEM pistons for model PN 17 to a total number of 7,000 sets, which leading them to increase in overtime in order to conform to the demand on time. One set of piston has 4 pieces of pistons; therefore they are required to produce 28,000 pieces of pistons. The forecast of demand for customer NK for the piston model PN 17 in May, June, and July 2013 are expected to have increment from the current demand which are 15% (8,050 sets), 25% (8,750 sets), and 27% (8,890 sets). The piston machining processes also contributed to large total lead time in the manufacturing processes. It was due to some processes having much longer machining time than the other. So, the next process would have to wait until the part was done in the previous stage before proceeding. This situation produced some idle time for machines and operators at several workstations at the time. Therefore, in this inquiry, it is important to improve the productivity enhancement in this production plant up to the level that can fulfill all the customer needs in not only in the short term but also in the long term. The design must be suitable for the long term so the company would not cost much money to change the design frequency. Hence, the simulation modeling analysis by using ARENA simulation software has been chosen as a method of improvement to the production plant in term of plant layout, machining processes, and material handling.

18 8 CHAPTER 2 LITERATURE REVIEW 2.1 INTRODUCTION This chapter will discuss in detail regarding the literature used in order to conduct and completed this research. The primary reason for the literature reviews is to identify the right concept and the definition which related to the research title. Each definition and the concept must be entirely understandable, so when the research is done, the problems can be discovered easily and the objectives of the research can be achieved. The resources of this literature review obtained from several secondary resources such as online journal, books, articles, and related sites. 2.2 PRODUCTIVITY Productivity can be defined as the measurement of the production line efficiency of the company. According Aini (2009), productivity is the ratio of outputs (goods and services) divided by the input (resources, such as labor and capital). It is important to improve the company s productivity, so that the company can remain competitive with other competitors and be on top of their field. In order to improve the productivity, the company must firstly improve the efficiency of their production line. It was essential to minimize or it could, eliminate the waste, so the goal of improvement can be seen prominently. An organizational survival was affected by the level of productivity improvement increased through production loss

19 9 reduction and labor efficiency and these efforts can be driven through a host of productivity improvement initiatives (Longenecker and Standsfield, 2000). Kaydos (1991) reported that in order to maximize and improve productivity continuously, the system is required to align their resources to their maximum capabilities and combined the work study such as scientific analysis, methods, and logical flow of the process. It is important to generate the process that can meet the level of productivity and quality required. From a manufacturing standpoint, productivity improvement is most often translated as: faster cycle time, lower cost, maximized machine utilization, and also maximized floor space utilization. 2.3 MATERIAL HANDLING Material handling systems are recognized as one of the basic components in a manufacturing organization. Material handling can be defined as the activities, equipment, and procedures that involved in the movement, storage, control and protection of materials and products throughout the manufacturing processes, distribution, and disposal. The systems exist for supporting the overall manufacturing process. It should be understood that part movement does not add value to the product, and any unnecessary movement should be eliminated wherever it is possible (Askin and Standridge, 1993). Material handling equipment encompassed a diverse range of tools, vehicles, storage units, and appliances and can be categorized as four main categories such as storage, engineered systems, industrial trucks and bulk material handling. The storage equipment usually used to hold or buffer materials during downtimes or when the materials are not being transported. It may refer to pallets, shelves or racks onto which materials may stacked in an orderly manner while wait for transportation or consumption. Whilst, the engineered systems are covering a variety of units that work cohesively to enable storage and transportation and often automated. Good examples of this system are conveyor and robotic delivery systems.

20 10 In other hand, industrial trucks are referred as different kinds of transportation items and vehicles used to move materials and products in material handling systems. The common type falls under this category are hand trucks, pallet jacks, walkie stackers and platform trucks. The final category is the bulk material handling equipment. It referred to the storing, transportation and control of materials in loose bulk form. These materials included food, fluid, or minerals. The common types of equipment under this category are conveyor belts, stackers, and hoppers. For the entire plant, the material handling system acts as the circulating system, dispatching vital material in all the plant cells. The objective need not be to determine a minimum cost material handling system, instead, the system that satisfies all the plant requirements to be effective and efficient manufacturers (Meyers and Stephens, 2000). 2.4 FACILITY LAYOUT Facilities layout is the arrangement of areas within a facility (Russell and Taylor, 2000). The arrangement is made physically consists of everything needed for the product or service, including machines, personnel, raw materials, and finished goods. Therefore, a facility layout design is responsible in minimizes the total cost of products and compete against competition and increases the factory s productivity, business performance, the effective utilization of manpower, space and infrastructure. The designed facilities should be flexible to maximize the benefits in an organization when there are future changes in product design, process design, schedule design and facility expansion. An effective layout can utilize space and labor efficiently, facilitate the entry, exit, and placement of material, products, and people, eliminate bottlenecks, reduce manufacturing cycle time, minimize material handling costs, and increase productivity, throughput or profitability (Gupta et al., 2004). Manufacturing facility layouts can be divided into two categories: basic layouts and hybrid layouts. The basic layouts consist of process, product, and fixed-position

21 11 layouts and the hybrid layouts consist of cellular layouts, flexible manufacturing systems, and mixed-model assembly lines. Patterns of flow may be viewed from the perspective of flow within workstations, within the department, and between departments. There are four general types of general flow pattern: Straight line, U- shaped, S-shaped, and W-shaped. 2.5 SIMULATION One of the gurus of simulation Shannon (1975) historically defined simulation as the process of designing a model of a real or imaginary system and conducting experiments with this model for the purpose either of understanding the behavior of the system or of evaluating various strategies (within the limits imposed by a criterion or set of criteria) for the operation of the system. This primitive definition highlights the general framework of simulation principles and gives a clue of the roadmap that simulation has gone through within the last century. Each and every word and phrase in the definition should be further emphasized for exact comprehension of the term simulation. The first sentence of the definition mentions the types of systems that simulation studies can be conducted on. The systems can be real or imaginary, which means that there can create a physical facility or a process to be modeled, or the model can be a modification of the existing system or it can be completely imaginary. The imaginary systems refer to the ones that are planned as alternatives to existing systems and entirely original systems Simulation Process As Shannon (1975) stated, simulation is a continuous process rather than a one-time create-and-use application. Especially computer simulation is an iterative method that includes several stages as Kelton et al., (2004) identified. Firstly, the simulation study is started by understanding the existing system and identifies the goals

22 12 of the study. The next step is creating the formulation of the model representation usually in terms of mathematical models or flowcharts before transferring into modeling software. Once a simulation is created, it is necessary to verify the simulation to ensure right things is done. The following stage is to validate the simulation to familiar subject that represented the system so that the simulation works in accordance with the conceptual model faithfully, supporting the validation work with statistical tests can be of critical importance at this stage. Experimentation with the developed model is done by designing experiments to identify the critical performance measures to be used with equal confidence and running these designed experiments by using the computers effectively. The last stages take account of analyzing the results, getting an insight of the results to evaluate the outcomes of the results and to assess the potential benefits. Finally, documentation is necessary for the inheritance of the work done for other simulation staff and also to clearly transmit the findings and recommendations to related management levels with precision and confidence. The life cycle of a simulation study has also been identified in detail by Balci (1990). This life cycle has been divided into 10 processes, 10 phases and 13 credibility assessment stages. Figure 2.1 provides the details of those identifications and the precedence and succession relations between them. According to (Sadowski, 1999) a successful simulation project is the one that delivers useful information at the appropriate time to sustain a meaningful conclusion, which means that there are three key elements of success in the simulation; decision, timing and information.

23 13 Figure 2.1: The life cycle of a simulation study Source: Balci (1990)

24 Simulation Benefits Simulation has many benefits for the users as outlined by Banks (2000). Designing, building, testing, redesigning, rebuilding then retesting can be an expensive project. Simulations take the building/rebuilding phase out of the loop by using the model that already created in the design phase. Most of the time, the simulation testing is cheaper and faster than performing the multiple tests of the design each time. With simulation, the problems of complex systems can be diagnosed that are nearly impossible to handle within the actual environment, identify constraints that act as a bottleneck for operations, visualize the plan using the animation capabilities of the software used that results in a more presentable design. Simulation is also beneficial to build consensus among the members of the decision makers and to prepare for changes by considering the potential what if scenarios. The simulation can be extensively applied as an off-line decision making tool for aiding the management with production planning issues such as efficient capacity utilization, sequencing and scheduling and allocation of resources in manufacturing and production Disadvantages of Simulation Banks (2000) underlines four main disadvantages of simulation: 1) To use the simulation application it requires special training and it is highly unlikely that models generated by different modelers about the same system will be the same. 2) The simulation results are difficult to be understood because most simulation outputs are essentially random variables based on random inputs, it may be difficult to find out whether an observation is a result of system interrelationships or randomness.