The ABC company, a manufacturer of windows for residential buildings, hired a quality consultant to train the shift supervisors and selected line workers in statistical process control methods. As a trial project, the plant manager wants to evaluate the capability of a critical cutting operation that he suspects might be the source of the gap problem. The nominal specification for this cutting operation is 25.500 inches with a tolerance of 0.030 inches. Thus, the upper and lower specifications are LSL = 25.470 and USL = 25.530 inch. The consultant suggested inspecting five consecutive window panels, per operator, in the middle of each shift over a 15-day period and recording the dimension of the cut. The data is below which shows 15 days’ data collected for each shift, by the operator. 

a) Establish statistical control limits and evaluate the process capability of the process to meet specifications. 

You may consider the following questions: 

What do the initial control charts tell you? 

Do any out-of-control conditions exist? 

If the process is not in control, what might be the likely causes, based on the information that is available? 

What is the process capability?

 What do the process capability indexes tell the company? 

Is ABC facing a serious problem that needs to address? 

b) The plant manager implemented the recommendations that results from the initial study. Because of the success in using control charts, The ABC company made a decision to continue using them on the cutting operation. After establishing the control limit, additional samples were taken over the next 20 shifts, shown in the second part of the table below. Evaluate whether the process remains in control, and suggest any actions that should be taken. 

Consider the following issues: 

Does any evidence suggest that the process has changed relative to the established control limits? 

If any out-of-control patterns are suspected, what might be the cause? What should the company investigate?