Operation Management - Tom Pulling Toys - Essay Example

Two data sets on colour of the dolls manufactured and their sizes have been recorded. Appropriate control charts have been used for the analysis of two datasets. It is found that both the processes are out of control. A trend is observed in the x bar chart for the size of the dolls making it a focus area for the company.There have been a lot of customer returns due to inconsistencies in the colour and the size of the dolls manufactured in the plant. In order to analyze the situation, the company recorded 2 sets of data.

The first set contains the number of colouring defects over a period of 30 days. The second set contains the sizes of 3 dolls selected at random daily over a period of 30 days. The company needs to find out whether its processes are in control or not.2. MethodologyC-chart is the most appropriate control chart for the number of defects found if the sample size remains the same throughout. For the first data set the sample size for testing in each of the 30 subgroups is 200. Thus, using a c-chart makes absolute sense.

The 3 sigma control limits for a c-chart are calculated as:Control Limits = c bar ± 3(c bar)^.5where c bar is the mean of the number of defects of each of the 30 subgroups.The control chart can then be obtained using the number of defects and control limits.x bar and R charts can be used for the second table because these charts are used when the actual quantities or observations are given. The 3 sigma control limits for the R chart are given by:Lower Control Limit = D3 * R barUpper Control Limit = D4 * R barwhere R bar is the mean of the range of height of the dolls for each of the 30 subgroups.

The control chart can then be obtained using the height range and control limits.The 3 sigma control limits for x bar chart are given by:Control Limits = x bar ± A2 * R barwhere x bar is the mean of the height of the dolls for each of the 30 subgroups.The control chart can then be obtained using the height mean and control limits.A2, D3 and D4 are the control chart constants that can be derived from standard tables (Table of Constants for Control Charts).In the c-chart for a number of defectives, it is seen that one of the observations lies outside the upper control limit.

Hence, the process is out of control. The manufacturing process of the toy plant is out of control for both the number of defectives in colour and the heights of the dolls. Since only 1 observation is out of limits for colour defects, it may be considered as a one-off deviation and can be neglected. However, the company must still aim to decrease the mean number of defects. This could be done by replacement of the machine which would require capital expenditure. The ultimate aim of the company must be to go for zero defects as proposed by quality experts.

This is also a key philosophy of Lean Management and Six Sigma.From the point of view of the heights of dolls, the process is completely out of control. Sharp trends are visible in the R chart and x bar chart. This implies a problem with the production process. This variation is a controlled variation and rectifying the production process will control the variation (Introduction to Statistical Process Control).Several quality tools can be used to study this problem. Fish-bone diagram, 5 Whys approach and Root Cause analysis can be used for the same.

The Use of scatter diagrams and process maps is also suggested to support this analysis. (Heizer & Render 2010).5. ConclusionIt is more important to identify the underlying cause of these problems. For this, the effective use of other quality tools must be done by the company.