Question

Problem5 While efficiency in the production operation is important to profitability,ACME Valve is also known for high quality fieished products. Parts that do not meet specifications cannot be "reworked, so that both the raw material cost and the machine time to produce them are detrimental to profitability. Drills can become holes, and machines can get out of callbration as well For the parts in your department the critical dimension is the diameter of the center hole and design specifications require that tolerances be maintained within 005". To insure that quality is maintained, one part from each machine is sent to the Quality Control Lab each hour and carefully measured and its hole diameter recorded into the QC database for each machine. dull after producing so many parts, typically resulting in oversized To better learn how the QC process is coordinated with the production areas, you are spending a day in the Quality Control Lab. In looking at the data for one of the machines making aluminum flanges, you notice some variation and possibly some trending in the data. The deta points for this machine over the last 24 hours are shown in the control chart below Hole ID (in). Machine #2 2.51 2.505 25 2.495 249 2.485 1 2 3 456789 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 The individual observations are plotted by time (ie. observations 1-24). The upper and lower control limits based on required tolerances for the center hole diameter are shown by the horizontal lines. Looking at this graph, answer the following questions 1) What if anything should be done at observation 6? At what point (which sample should the QC Lab alert manufacturing that the may be out of control or nearly so 2) 3) Did this process actually become out of control and if so how many parts potentially may 4) What could account for the sudden change between samples 23 &24 ess need to be scrapped?

Answer 1

1) at Sample 6, since the cmponent went out of specification, the drill can be checked to see if it has lost its sharpness

2) at Sample 17 the manufacturing team should be alerted as the sample is close to Rework/Rejection and the delta between the hole dia and rejection threshold has been decreasing consistently since sample 8 indicating the manufacturing process has begun to go out of control

3) after sample 18, the process has gone out of control and samples 20,21,22,23 need to be scrapped

4) the drastic change between sample 23 and sample 24 could be the "Change in tool" after the earlier toll has lost its sharpness.