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Defects in graphite shafts. Over the last year, a company
Chapter 13, Problem 88SE(choose chapter or problem)
Defects in graphite shafts. Over the last year, a company that manufactures golf clubs has received numerous complaints about the performance of its graphite shafts and has lost several market share percentage points. In response, the company decided to monitor its shaft production process to identify new opportunities to improve its product. The process involves pultrusion. A fabric is pulled through a thermosetting polymer bath and then through a long heated steel die. As it moves through the die, the shaft is
cured. Finally, it is cut to the desired length. Defects that can occur during the process are internal voids, broken strands, gaps between successive layers, and microcracks caused by improper curing. The company’s newly formed quality department sampled 10 consecutive shafts every 30 minutes, and nondestructive testing was used to seek out flaws in the shafts. The data from each 8-hour work shift were combined to form a shift sample of 160 shafts. Data on the proportion of defective shafts for 36 shift samples are presented in the table above.
a. Use the appropriate control chart to determine whether the process proportion remains stable over time.
b. Does your control chart indicate that both common and special causes of variation are present? Explain.
c. Data on the types of flaws identified are given in the table below. [Note: Each defective shaft may have more than one flaw.] To help diagnose the causes of variation in process output, construct a Pareto diagram for the types of shaft defects observed. Which are the “vital few”? The “trivial many”?
Questions & Answers
QUESTION:
Defects in graphite shafts. Over the last year, a company that manufactures golf clubs has received numerous complaints about the performance of its graphite shafts and has lost several market share percentage points. In response, the company decided to monitor its shaft production process to identify new opportunities to improve its product. The process involves pultrusion. A fabric is pulled through a thermosetting polymer bath and then through a long heated steel die. As it moves through the die, the shaft is
cured. Finally, it is cut to the desired length. Defects that can occur during the process are internal voids, broken strands, gaps between successive layers, and microcracks caused by improper curing. The company’s newly formed quality department sampled 10 consecutive shafts every 30 minutes, and nondestructive testing was used to seek out flaws in the shafts. The data from each 8-hour work shift were combined to form a shift sample of 160 shafts. Data on the proportion of defective shafts for 36 shift samples are presented in the table above.
a. Use the appropriate control chart to determine whether the process proportion remains stable over time.
b. Does your control chart indicate that both common and special causes of variation are present? Explain.
c. Data on the types of flaws identified are given in the table below. [Note: Each defective shaft may have more than one flaw.] To help diagnose the causes of variation in process output, construct a Pareto diagram for the types of shaft defects observed. Which are the “vital few”? The “trivial many”?
ANSWER:
Step 1 of 5
The given data is regarding the proportions of the defective shafts for 36 shift samples.
a) Now we have to construct the appropriate control chart to determine whether the
process proportion remains stable over time. For this, the appropriate control chart
is p-chart since the data is of attribute nature. By using the MINITAB, we get the
chart as follows;
1) Type or Import data into the worksheet (named Week, number tested and
number with leaks)
2) Select P chart... from the attributes Charts and sub group size in
Control Charts of Stat ribbon.
3) Specify variables as Defects, and type 500 in the sub group size box.
4) Check all the tests for the special causes in Tests ribbon of p -chart
Options... tab.
5) Click Ok.