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Fall 20001 Exam #2 Key ISAT 211 Fall 2000 Sections 1 & 2
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Fall 2000ISAT 211 Dr. Ken Lewis2
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Sketch and carefully label the product process matrix and place the letters A, B, C, … corresponding to the following production system at their appropriate places. A. A small manufacturer of custom racing bicycles. B. A flexible manufacturing system C. A mass producer of refrigerators D. A ship yard E. An oil refinery Project Job Shop Batch Assembly line Continuous flow D A B C E Flexibility high, unit cost high Flexibility low, unit cost low Volume
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Fall 2000ISAT 211 Dr. Ken Lewis4 ISAT Industries agreed with its principal supplier of dry erase pens on a consumer’s risk of 10% and a producer’s risk of 5%. The two parties also agreed that the number of defects in a lot should be controlled with AQL of 2% and LTPD of 7%. A.) Help ISAT industries set up the acceptance test. Determine the parameters required for the acceptance test. Producers risk = 5%Consumeers risk = 10% AQL = 0.02LTPD = 0.07 n = sample size and c will be the number of defects allowed before the lot is rejected. From the table, c = 5 and n AQL = 2.61 B) Merely sample 130 units and reject the lot if 5 or more defects are observed.
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Fall 2000ISAT 211 Dr. Ken Lewis5 A manufacturer is conducting a capability study of a process. The mean of measurements of a key variable in the process is 12.42 and its standard deviation is 0.147. The design specification for the measured variable is 12.5 ± 0.5. A) What are the upper and lower tolerance limits? The tolerance limits are the slack or size deviation allowed. In this case, the designer specified ± 0.5 so… Upper tolerance limit = UTL = 12.5 + 0.5 = 13.0 Lower tolerance limit = LTL = 12.5 - 0.5 = 12.0
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Fall 2000ISAT 211 Dr. Ken Lewis6 A manufacturer is conducting a capability study of a process. The mean of measurements of a key variable in the process is 12.42 and its standard deviation is 0.147. The design specification for the measured variable is 12.5 ± 0.5. B) What is the process capability ratio? The process capability ratio is simply:
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Fall 2000ISAT 211 Dr. Ken Lewis7 A manufacturer is conducting a capability study of a process. The mean of measurements of a key variable in the process is 12.42 and its standard deviation is 0.147. The design specification for the measured variable is 12.5 ± 0.5. C) What is the process capability index? The process capability index is the lesser of
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Fall 2000ISAT 211 Dr. Ken Lewis8 A manufacturer is conducting a capability study of a process. The mean of measurements of a key variable in the process is 12.42 and its standard deviation is 0.147. The design specification for the measured variable is 12.5 ± 0.5. C) What is the process capability index 2 ?
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Fall 2000ISAT 211 Dr. Ken Lewis9 A manufacturer is conducting a capability study of a process. The mean of measurements of a key variable in the process is 12.42 and its standard deviation is 0.147. The design specification for the measured variable is 12.5 ± 0.5. D) Is the Process capable of producing defect-free products? Why? Yes it is. The PCR is >1 so the 6 sigma is within the tolerance limits. Note: Having a PCR > 1.33 merely makes the process easier to control.
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Fall 2000ISAT 211 Dr. Ken Lewis10 A manufacturer is conducting a capability study of a process. The mean of measurements of a key variable in the process is 12.42 and its standard deviation is 0.147. The design specification for the measured variable is 12.5 ± 0.5. E) What should the manufacturer do? He can do either nothing… or Since his C pk = 0.9524, he might try to raise the variable average. This could be tricky. I think I would just sit on it for the moment
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Fall 2000ISAT 211 Dr. Ken Lewis11 In order to establish a preliminary control chart for monitoring defects in a process, 10 samples of 40 units each were inspected. The number of defective units in each sample is shown in the table below. A) What is the average number of defects in the samples? The average number of defects is the total number of defects divided by the Total number of items sampled. Sample number 12345678910 Defectives 2130201210
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Fall 2000ISAT 211 Dr. Ken Lewis12 In order to establish a preliminary control chart for monitoring defects in a process, 10 samples of 40 units each were inspected. The number of defective units in each sample is shown in the table below. B) What are the process control limits for 99.7% confidence level? First we need the standard deviation: Z for 99.7% confidence = 3
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Fall 2000ISAT 211 Dr. Ken Lewis13 In order to establish a preliminary control chart for monitoring defects in a process, 10 samples of 40 units each were inspected. The number of defective units in each sample is shown in the table below. C) Is the process in control? The highest fraction defective is 3/40 = 0.075 This is less than the control limits, so yes the process is in control.
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Fall 2000ISAT 211 Dr. Ken Lewis14 In order to establish a preliminary control chart for monitoring defects in a process, 10 samples of 40 units each were inspected. The number of defective units in each sample is shown in the table below. D) Is the process capable? Sure, it’s capable. The highest fraction defective is well within the process control limits.
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