Your company, ABC Company, uses 100% inspection for all materials and requires zero defect quality of all its vendors. If bad parts are found, it cost $1.00 per part to inspect the entire lot. A decision then must be made to accept or reject the lot.
Suppose vendor XYZ sends a lot of materials with 5% defective parts to ABC Company although it is required to send "zero defects". ABC inspects the lot and decides to use the materials. However, accepting the bad lot of material causes problems which costs ABC
Company $60 per bad part to correct.
If the lot size is 10,000 pieces then
What is the cost associated with 100% inspection of the lot? =
What is the cost associated with not inspection of the lot? =
PROBLEM 2
If average fraction defect produced in a process is 0.03 and standard deviation of defect is 0.001 then find the upper control limit and lower control limit of the p-chart for process control (see page 315 13th ed for details).
UCL of p = p + 3 x (std. dev). =
LCL of p = p - 3x ( std. dev) =
PROBLEM 3
A lathe machine which has a natural variation due to vibration given by std. dev (sigma) = 0.0001". This machine has been chosen to machine a straight pin of 1.000" diameter (nominal design) with a tolerance of +/- 0 .0001".
45 samples are tested and the grand mean ( x double bar) is determined to be 1.000" . The subgroup size for the test samples is 3. (A2 comes from the table on page 320 for subgroups of 3). R bar for the range is given as .005. Use the formulas on page 320 and 325 to calculate the items below.
Specification limits are the nominal design plus the tolerance (upper specification limit) and the nominal minus the tolerance (lower specification limit)
Determine:
• 1. Upper specification limit =
• 2. Lower specification limit =
• 3. Upper Control Limit (UCL) for X bar =
• 4, Lower Control Limit (LCL) for X bar =
• 5. Process Capability CP= (USL-LSL)/6 (sigma) =