Case 02:
The LeedSim factory is a traditional assembly facility working as a subcontractor to the
telecommunications industry. Its main product is a specialized switchboard cabinet used in network base stations. The company has been successful on the sales side, and the orders are piling up. Unfortunately, the operations department has had some problems with reaching the desired (and necessary) productivity levels. Therefore, they have decided to seek your help to create a simulation model of the involved processes as a first step towards analyzing and improving the process design.
To find the right level of detail in the model description, they want to start with a simple model and then successively add more details until a suitable model with the right level of complexity is obtained. The simulation should be run over a 3-month (12-week) period of five 8-hour workdays per week. A schematic flowchart of the manufacturing process is shown in Figure 9.35.
After the cabinets are completed and inspected, the finished cabinets leave the factory. It is noteworthy that each workstation can handle only one item at a time. Workstations 1 through 3 cannot store items. Similarly, there is no room to store items before Workstation 4, but after it, there is room to store two assembled cabinets. At Workstation 5, there is ample space to store cabinets before the workstation, but after it, there is only room to store at most two painted cabinets. At the inspection station, there is ample space to store cabinets both before and after the station. Each cabinet that is made requires one unit each of five different components
aw materials delivered to the inbound storage area. Workstation 1 requires one unit each of raw materials 1 and 2, Workstation 2 requires one unit of raw material 3, and Workstation 3 requires one unit each of raw materials 4 and 5. Table 9.18 specifies the estimated processing times in Workstations 1 through 5. Table 9.19 shows collected inspection time data that has been not yet been analyzed. This needs to be done to build a valid model of the process.
The performance measure that LeedSim is most interested in is the number of cabinets produced in a 3-month period. However, they also want to keep track of the following:
1.The WIP levels (measured in units of raw material)—the total as well as at different parts of the workshop (the mean and the standard deviation for a single run, and the mean with 95 percent confidence intervals in the case of multiple simulation runs)
2.The inbound storage levels of the raw materials (the maximum, the mean, and the standard deviation for a single run, and the mean with 95 percent confidence intervals in the case of multiple simulation runs)
3..The cycle time, measured from the instant a component a
ives to the storage area until a finished cabinet leaves the factory (the mean and the standard deviation for a single run and the mean with 95 percent confidence intervals in the case of multiple simulation runs). (Hint: Note that all components for a particular cabinet have the same cycle time)
4.The use of workstations and equipment such as the forklift truck (the mean with 95 percent confidence intervals in the case of multiple simulation runs.
Create the necessary simulations and answer questions 1-4. For each scenario in the case, a separate simulation file should be submitted.
TABLE 9.1
Observed Inspection Time Data in Minutes
No. Inspection Time No. Inspection Time No. Inspection Time No. Inspection Time
XXXXXXXXXX021s a 0343 on 152
XXXXXXXXXX @ XXXXXXXXXX
3 0169 = 243 @ 0756 % 6198
XXXXXXXXXXPY 091 % L663
5 2440 EY 008s & XXXXXXXXXX
XXXXXXXXXX% os & 20m % 0183
7 02m 7 234 & XXXXXXXXXX
5 1185 El 0458 es 207 % 0212
9 508 » 147 © 5358 % 0757
XXXXXXXXXXn oo XXXXXXXXXX
n 0590 a 0307 n XXXXXXXXXX
XXXXXXXXXXn ans 102 asm
1B XXXXXXXXXXe XXXXXXXXXX
XXXXXXXXXX104 oz
XXXXXXXXXXoats 7 121% 105 os61
XXXXXXXXXXrs XXXXXXXXXX0697
XXXXXXXXXX XXXXXXXXXX
1s 205 FY 425 » XXXXXXXXXXoss
© 285% rs XXXXXXXXXX%
2 S XXXXXXXXXX10 0357
XXXXXXXXXXst 0293 m 1143
2 206 = XXXXXXXXXXm2 3088
XXXXXXXXXX = 1268 m 0548
2% XXXXXXXXXX4 3460
5 51% XXXXXXXXXX1271
% XXXXXXXXXX16 3400
XXXXXXXXXXita 3082
x 335 EY 340 5 Los 1s 0357
» oss XXXXXXXXXX%
Fl 1992 @ XXXXXXXXXXors