Harrell−Ghosh−Bowden: Simulation Using ProModel, Second Edition
II. Labs
1. Introduction to ProModel 6.0
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© The McGraw−Hill Companies, 2004
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NTRODUCTIO UCTION N TO INTROD PROMODEL 6.0
Imagination is the beginning of creation. creation. You You imagine what you desire, desire, you will what you imagine and at last you create what you will. —George Bernard Shaw
ProMode ProMo dell (P (Pro roduc ducti tion on Mo Model deler er)) by PRO PROMOD MODEL EL Cor Corpo porat ration ion is a si simu mula lati tion on to tool ol forr mo fo model delin ing g var vario ious us ma manuf nufac actu turi ring ng an and d se serv rvic icee sy syst stem ems. s. Ma Manuf nufac actu turi ring ng sy syst stem emss such su ch as jo job b sho shops ps,, co conve nveyor yors, s, tr trans ansfe ferr li line nes, s, ma mass ss pr produ oduct ction ion,, as asse semb mbly ly li line nes, s, flex flexiiblee ma bl manuf nufac actu turi ring ng sy syst stem ems, s, cr crane anes, s, ju just st-i -inn-ti time me sy syst stem ems, s, kan kanba ban n sy syst stem ems, s, an and d so fort fo rth h ca can n be mo mode deled led by Pr ProM oMode odel. l. Ser Servic vicee sys syste tems ms su such ch as hos hospi pita tals ls,, ca call ll cen cente ters rs,, warehous ware housee oper operati ations ons,, tra transpo nsporta rtation tion sys system tems, s, groc grocery ery/dep /depart artmen mentt stor stores, es, inf inform ormaation ti on sys syste tems ms,, cu cust stom omer er se serv rvic icee ma manag nagem emen ent, t, sup suppl ply y ch chai ains ns,, log logis isti ticc sy syst stem ems, s, and other oth er busi businessproces nessprocesses ses als also o can be mod modele eled d effi efficien ciently tly and quic quickly kly withProMod withProModel. el. ProModel is a powerful tool in the hands of engineers and managers to test various alternative designs, ideas, and process maps before actual implementation. Improvements in existing systems or the design of new systems can be modeled and tested before committing any money, time, or other resources. Various operating strategies and control alternatives can be compared and analyzed. Typically,, most people use simulation tools to accurately predict and improve system ically performance by modeling the actual location (such as a plant floor, a bank lobby, or an emergency room) or an abstract process. Through testing various what-if scenarios, one can determine the best (optimum) way to conduct operations. ProModel concentrates on resource utilization, production capacity capacity,, productivity, inventory levels, bottlenecks, throughput times, and other performance measures. ProModel is a discrete event simulator and is intended to model discrete systems. Also, it is designed to model systems where events happen at definite points in time. The time resolution is controllable and ranges from 0.01 hours to 0.00001 seconds.
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Harrell−Ghosh−Bowden:
II. Labs
1. Introduction to ProModel
Simulation Using ProModel, Second Edition
378
6.0
Part II
© The McGraw−Hill Companies, 2004
Labs
ProModel uses a graphical user interface (GUI). It is a true Windows (XP, Me, 2000, 98, 95, or NT) based simulation tool and utilizes all the Windows features such as a standard user interface, multitasking, built-in printer drivers, and “point and click” operation. ProModel has an online help system and a trainer. Background graphics in .BMP, .PCX, .WMF, and .GIF formats can be imported into ProModel. Input data from spreadsheets can be seamlessly read into ProModel for quick and easy updates. Also, multiple-scenario analysis is possible using various input data files with the same model. Other model data may be read from or written to general text files.
L1.1 ProModel 6.0 Opening Screen ProModel can be installed in one of the following ways: a. Runtime/evaluation package. b. Standard package. c. Student package. d. Network package.
FIGURE L1.1 ProModel opening screen (student package).
Harrell−Ghosh−Bowden:
II. Labs
1. Introduction to ProModel
Simulation Using ProModel, Second Edition
6.0
Lab 1
© The McGraw−Hill Companies, 2004
Introduction to ProModel 6.0
379
ProModel’s opening screen (student package) is shown in Figure L1.1. There are six items (buttons) in the opening menu: 1. Open a model: Allows models created earlier to be opened. 2. Install model package: Copies to the specified destination directory all of the files contained in a model package file. 3. Run demo model: Allows one of several example models packed with the software to be run. 4. www.promodel.com: Allows the user to connect to the PROMODEL Corporation home page on the World Wide Web. 5. SimRunner: This new addition to the ProModel product line evaluates your existing simulation models and performs tests to find better ways to achieve desired results. A design of experiment methodology is used in SimRunner. For a detailed description of SimRunner, please refer to Lab 11. 6. Stat::Fit: This module allows continuous and/or discrete distributions to be fitted to a set of input data automatically. For a detailed discussion on the modeling of input data distribution, please refer to Lab 6.
L1.2 Simulation in Decision Making ProModel is an excellent decision support tool and is used to help plan and make improvements in many areas of manufacturing and service industries. Click on Run demo model from the shortcut panel and select any model that looks interesting to run. You can also use the main menu to select File → Open and then choose a model from the Demos subdirectory. To run a model, select Simulation → Run. To stop a simulation prematurely, select Simulation → End Simulation. Problem Statement At a call center for California Cellular, customer service associates are employed to respond to customer calls and complaints. On average, 10 customers call per hour. The time between two calls is exponentially distributed with a mean of six minutes. Responding to each call takes a time that varies from a low of 2 minutes to a high of 10 minutes, with a mean of 6 minutes. If the company had a policy that
a. The average time to respond to a customer call should not be any more than six minutes, how many customer service associates should be employed by the company? b. The maximum number of calls waiting should be no more than five, how many customer service associates should be employed by the company?
Harrell−Ghosh−Bowden:
II. Labs
1. Introduction to ProModel
Simulation Using ProModel, Second Edition
380
6.0
Part II
© The McGraw−Hill Companies, 2004
Labs
L1.2.1 Average Waiting Time First we build a simulation model with one customer service associate answering all customer calls (Figure L1.2). The average time a customer has to wait before reaching the customer service associate is 18.92 minutes (Figure L1.3). This is a much longer wait than the company policy of six minutes (average). If we employ two customer service associates (Figure L1.4), we would like to figure out what the average wait would be. The average wait drops down to 5.9 minutes (Figure L1.5), which is clearly a much more acceptable result. Hence the decision recommended to management will be to hire two associates.
FIGURE L1.2 California Cellular with one customer service agent.
FIGURE L1.3 Customer waiting time statistics with one customer service agent.
FIGURE L1.4 California Cellular with two customer service agents.
Harrell−Ghosh−Bowden:
II. Labs
Simulation Using ProModel, Second Edition
1. Introduction to ProModel 6.0
Lab 1
Introduction to ProModel 6.0
© The McGraw−Hill Companies, 2004
381
FIGURE L1.5 Customer waiting time statistics with two customer service agents.
FIGURE L1.6 Number of calls waiting with one customer service agent.
FIGURE L1.7 Number of calls waiting with two customer service agents.
L1.2.2 Maximum Queue Length Now we want to evaluate the policy of no more than five calls waiting for response at any time. First we look at the results (Figure L1.6) of having one customer service associate working at a time. The maximum number of customers waiting for response is 18. This is clearly not an acceptable situation. If we change the number of associates to two, the results obtained are given in Figure L1.7. The maximum number of calls waiting is five. This is acceptable according to the company policy of no more than five calls waiting. When we graph the number of incoming calls w aiting for the duration of the simulation run of 500 hours (Figure L1.8), there were only three occasions of five calls waiting. Hence, we recommend to management to hire two associates.
Harrell−Ghosh−Bowden:
II. Labs
1. Introduction to ProModel
Simulation Using ProModel, Second Edition
382
6.0
Part II
© The McGraw−Hill Companies, 2004
Labs
FIGURE L1.8 Graph of number of customers waiting versus simulation run time.
L1.3 Exercises 1. How do you open an existing simulation model? 2. What is SimRunner? How can you use it in your simulation analysis? 3. What does the Stat::Fit package do? Do you need it when building a simulation model? 4. At the most, how many locations, entities, and types of resources can be modeled using the student version of ProModel? 5. Open the Manufacturing Cost model from the Demos subdirectory and run the model three different times to find out whether one, two, or three operators are optimal for minimizing the cost per part (the cost per part is displayed on the scoreboard during the simulation). Selecting Model Parameters, you can change the number of operators from the Simulation menu by double-clicking on the first parameter (number of operators) and entering 1, 2, or 3. Then select Run from the Model Parameters dialog. Each simulation will run for 15 hours. 6. Without knowing how the model was constructed, can you give a rational explanation for the number of operators that resulted in the least cost? 7. Go to the ProModel website on the Internet (www.promodel.com). What are some of the successful real-world applications of the ProModel software? Is ProModel applied only to manufacturing problems?
