Operation managment (Exercises) Essay Example | Topics and Well Written Essays - 4500 words

Operation managment (Exercises) - Essay Example Both the -charts and R-charts are used to determine whether the output of the process fall within a certain range. These measures may focus specific features such as the net weight of the product. Alternatively they may also analyze the process as a whole such as the average output (Heizer and Render). However, what these two charts often do not measure is the defect rate. For this reason, p-charts and c-charts are present to do such analysis. The difference between the two is that the former can be used to describe the proportion of the population which is defective (Reid and Sanders). On the other hand, c-charts are used to analyze the raw quantity of defects which occur. In the case presented, only the number of defects is readily available for analysis. It is therefore necessary to use c-charts in analyzing data. There can be two approaches to analyzing the said data. To view the process as a whole, the total daily defect count can be computed. Using the daily defect count, the mean may be obtained. Subsequently, the upper and lower control limits for the c-chart may be constructed and analyzed. Tables 1 and 2 present the daily defect data for the standard material and the super plastic material. These two control charts reveal some interesting features of the two processes. The process for manufacturing the standard material shows a stable operation. ... Knowing these quantities, the control charts shown in Figure 1 and 2 may be constructed. Figure 1. Control Chart for the Defects in the Standard Material Figure 2. Control Chart for the Defects in the New Material These two control charts reveal some interesting features of the two processes. The process for manufacturing the standard material shows a stable operation. The points in the control chart are centered on the mean value and fluctuate above and below the central tendency. Also, no spikes can be seen in the chart. It can therefore be said that the original process is in control. The second chart shows a trend quite similar to the original process. As with the first chart, there are no spikes above or below the control limits. Also, the data fluctuates as with any normal process. However, it should be noted that near the start of the production process, the points are generally below the control limit. As each successive day in the production process passes, the total number of defects appears to be increasing. In fact, at the second half of the data, the points tend to be above the mean. The control chart in Figure 2 therefore reveals a drift towards the upper control limit. While this process is currently in control, it may eventually shift above the upper control limit. It therefore warrants further investigation (Heizer and Render). To isolate the nature of the defect, it becomes helpful to analyze each type of defect. That is, a control chart may be constructed for each particular type. The said defect counts are shown in Tables 3 and 4. Table 3. Individual Defect Count for the Standard Material Standard Uneven Crack Scratch Bubbles Thickness Week