BALANCING PLANES

 

Salwa Ammar & Ronald Wright 

Department of Business Administration

Le Moyne College

Syracuse, NY 13214

wright@palm.lemoyne.edu ammars@palm.lemoyne.edu

 

We designed this exercise so that the assembly line product is a simplified version of LEGOS airplane model # 6536 . The use of this specific model is in no way crucial. In fact any similar assembly model can be used. The game is played in groups of six to ten and at two stages. During the first stage, each group is given a kit of plane parts ready for final assembly. This kit includes: front, body, back, right and left wings, shield, engine, and pilot (see Figure 2). The shield, engine, and pilot are defined each as a single piece while the rest of the parts are subassemblies.

 

Figure 2. Assembly line product.

 

The students determine the precedence for the final assembly. The only imposed precedence is the final task labeled "test" where the pilot is attached to the completed plane. The Game tasks are listed below. The students also estimate all task times usually by timing how long it takes them to complete each task. Based on these estimations, the students are asked to balance a line that will produce 12 planes in five minutes.

The second stage of the exercise is the implementation of the lines. One of the groups stages their line with one unit wip in each workstation. They are then asked to demonstrate the performance of the line. This game is challenging and fun. all students can make the claim of having "worked" on an assembly line. Needless to say many of the groups fail to complete the required number of planes in the five minute period. There are several contributing reasons, all of which emphasize the difference between theory and practice. One reason is that most groups fail to recognize the difference between feasible and practical task precedence. For example, although it is feasible to attach the shield to the front, it is not practical to do so until the front has been attached to the body. Another reason is that they often assign an ideal task time that is invariably an underestimate of the realistic times for completing tasks in an assembly line layout. Sometimes work stations configuration contributes to the inefficiency of the line. For example, the right and left wings share common parts and are mounted on the plane at the same time, hence it is impractical to locate these tasks at two separate work stations in different locations on the line. The first stage of the game is completed in about 30 minutes. After that we allow students 10 to 15 minutes to redesign the line. We often conclude the class by giving examples from industries that further illustrate the above mentioned reasons. For example, in a XEROX plant, tasks with an ideal time of 12 seconds are allowed a task time of 20 seconds.

 

Many variations are possible. In classes where time is shorter and/or the professor wishes to maintain more control, models can be passed out to groups of three students and they can practice each task and then determine the time required. A class consensus of the required times can be determined and the instructor can then lead the class through the exercise of balancing the line. A group of volunteers can then try to implement the line. Similar discussions will follow.

 

Task

Description

Task

Description

A

prepare front

F

attach front to body

B

prepare back

G

attach back to body

C

prepare body

H

attack wings to body

D

prepare right wing

I

attach engine to back

E

prepare left wing

J

attach shield to front

K

test (mount pilot)

 

 

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