Question: Varians Controls manufactures a variety of different electric motors and drives. One step in the manufacturing process involves cutting copper wire from large reels into smaller lengths. For a particular motor, there is a dedicated machine for cutting wire to the required length. As a part of its regular quality improvement activities, the continuous process improvement team at Varians took a sample size of 5 cuttings every hour for 30 consecutive hours of operation. At the time the samples were taken, Varians had every reason to believe that its process was working as intended. The automatic cutting machine records the length of each cut, and the results are reported in the file Varians Controls.
a. Develop the appropriate 3-sigma control chart(s) for this process. Does the process appear to be working as intended (in control)?
b. A few weeks after the previous data were sampled, a new operator was hired to calibrate the company's cutting machines. The first 5 samples taken from the machine after the calibration adjustments (samples 225 to 229) are shown as follows:
Based on these sample values, what can you say about the cutting process? Does it appear to be in control?