line_balancing

# line_balancing - OPIM 301 In-class Exercise Instructions...

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OPIM 301 In-class Exercise Instructions November 5, 2009 In this exercise, you will develop an Excel Solver model to perform assembly line balancing. The objective is to understand how a relatively more complicated problem like this can be modeled using Integer Programming features of Solver. The problem you will work on is the same problem solved in class by the Professor. Pre-requisites: You must have Excel 2007 with the Solver add-in installed. If you do not have this, follow the steps provided in the previous in-class exercise. Instructions for the Exercise 1. Log on to SUCourse OPIM 301 website, go to Assignments section and click Week 6 In-class Excel Exercise . Download the attachment line_balancing.xls . The file line_balancing.pdf includes the instructions you are reading now. 2. Open the line_balancing.xls Excel file. The contents of the file should be seen as in the picture below: 3. Recall that In Excel Solver-based optimization, you need to perform two main steps: a. Develop the Excel model – where you define all relationships in your problem – Steps 4-8 b. Develop the Solver model – where you provide Solver specific instructions – Steps 9-14 4. Before you start developing the Excel model, always check to see if the problem input is completely on your Excel sheet. In this case, notice that the upper-left table includes details about individual tasks, their durations and precedence relationships. One missing information is the workstation cycle time . We have calculated this in class as 4.2 minutes, so enter this information in cell O24 .

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5. The first and the most crucial step of the first phase is to figure out the decision variables of the problem. In this problem, the unknown you are trying to find out through optimization is which task is assigned to which workstation . In the Excel sheet, a tabular range ( G15:N23 ) has been created for you to calculate and store this information. The rows of this range correspond to tasks, and the columns correspond to workstations. The values inside the matrix are the actual binary decision variables . A binary variable means the value can only be 0 or 1. In this case, 1 means the corresponding task is assigned to the matching workstation # in the top row; 0 means the task is not assigned. Recall that your objective in this problem is to minimize the number of workstations used. This is something that would typically be represented as the target cell in Solver, so it’s a good idea to use a dedicated cell for this quantity. Let us use cell E14 for this purpose. For reasons that will be explained later, this cell must also be a decision
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line_balancing - OPIM 301 In-class Exercise Instructions...

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