Toshiba Production Case

We analyzed a Toshiba assembly line plan for a new subnotebook computer. The engineering section manager, Toshihiro Nakamura, wants to make changes to the line process as designed by the engineers. The basic assembly line equipment and space already exist within the Toshiba plant, so the subnotebook assembly process must conform to those preexisting constraints. Specifically, the assembly line is a straight 14.4-meter conveyor system that can accommodate 8 to 12 workers plus one supporter to aid in the assembly process. The employees work at assembling for 7.5 hours a day. The computers are assembled from inventory provided by separate employees. Because it is well managed, there is no concern about supply for the line.

Production quantities for the subnotebook computer are to begin at 150 units per day and increase to 250 in a week with the ultimate goal of 300 computers per day. We used a number of analysis calculations in our decision support model to show the capacity and relative efficiency of different iterations of the assembly line. We have also shown a possible solution to the main problem of the case: As the process is designed, it is impossible to attain 300 computers in a 7.5-hour shift using only one line. The decision support model shows one option for how this can be solved with a given set of assumptions.

Discussion

The decision support models consisted of an Excel spreadsheet that utilized mathematical equations as explained in our spreadsheet showing the formulas that we used. The concept employed was a timeline of assembly where the goal was to minimize the maximum cycle time. We defined cycle time as the time between movements of the conveyor. We called the employee position of maximum cycle time the bottleneck position. The bottleneck position changed as different numbers of employees were used on the line; in some cases, there were multiple worker positions with the same bottleneck time, making it more critical that they all work within the time constraints. We used certain additional formulas to achieve the results that were not required but increased our understanding of the situation as we more extensively analyzed the efficiencies of the assembly line.

We started by analyzing what the case study was asking of us. The goal of the case that presented a problem was to be able to produce 300 computers in a day with a 7.5-hour workday. This means that we needed to produce at least 40 computers an hour, which, according to our bottleneck theory, meant that every 90 seconds we needed to complete the production of a computer. Therefore, we had to establish a bottleneck time of 90 seconds or less for all of the given operations otherwise we would not be able to accomplish the 300 computers that we needed to complete.

Based on the information we gathered and on the assumptions that are outlined below, we are able to reach our goal. In the case that these assumptions are either impossible or not applicable, we would need to resort to working overtime or adding an additional assembly line for the subnotebook. Either of these two options can easily achieve the goal of 300 computers per day, but Toshihiro did not want to use overtime and we have assumed only one line is to be used.

The assumptions we used are an important part of the case; they were either given directly in the Toshiba case or inferred by us. We assumed that we could not physically lengthen the line and therefore could not add more than the 12-employee maximum of the line we were given to work with. Before making any major modification to the process, we assumed that individual operations could not be split from the engineers' plans.

Other assumptions that we made for the case study were that we could only use the 7.5-hour workday and one line of production. We also assumed that we were limited to the range of 8 to 12 people stated in the problem. Because we are making complex equipment, we assumed that we could not change the order of the operations themselves but that we could have a station do varying combinations of operations. The projections in the Excel spreadsheet also assume that the engineers' specified times would be accurate once production begins. Regarding the hardware testing operations, the activities are to be performed on three computers concurrently, so we divided the operation times by three to arrive at the true operation times.

Once we began our changes, we had to make more assumptions since we realized that we had to be able to divide the first operation into two parts, as the operation time was 100 seconds, greater than the maximum cycle time needed (90seconds) to achieve our goal of 300 computers in a shift. We also assumed that with an upgrade, we could change the hardware testing software activity time to 50% of the original time. We also assumed we could change the screwing operations to decrease the needed time by changing the action to using plastic rivets. We felt that plastic rivets offer an important advantage over screws because they are easier to install and do not require the use of a tool. The only disadvantage to their use is the needed removal and replacement of them if problems arise for consumers in the future.

Since the assembly line is 14.4 meters and separated into 1.2-meter intervals, it can accommodate a maximum of 12 workers (14.4/1.2=12). If less than 12 workers are utilized, then they should be bunched to the front of the conveyor system