質量管理七大手法 (2)ppt課件

1、QC 7 ToolsWhat is 7 tools?Check sheetLevel diagramHistogramPareto diagramCause-and-effect diagramScatter diagramControl chartImportance of 7 toolsWhy “MADE IN JAPAN - Automobile, electronic, chemical, exactitude equipment, etc.The concept “QC 7 tools is raised by Kaoru Ishikawa.“QC 7 tools played an

2、 important part in Japans economic recovery and development.QC 7 Tools - Check SheetWhat is check sheet?A table which lists out all items need checking.Check sheet includes, but not limited to: diagnoses, questionnaire, record, statistics, etc.Check Sheet - Key pointsKey points:1. Verify the items t

3、o check;2. Verify the frequency to check;3. Verify the personnel to check.Implement procedure1. Verify the object;2. Frame the check sheet;3. Check and record;4. Request a improvement aiming at the NC items5. Verify the improvement6. Summarize periodically and improve persistently. Level DiagramWhat

4、 is level diagram?Sort all opinions, views or thoughts by specific topic and group the collected data or information.Implement procedure1. Identify the topic to study;2. Frame the level diagram and collect data;3. Sort the data to various levels;4. Analyze the data.QC 7 Tools - HistogramWhat is hist

5、ogram?A histogram is a simple frequency distribution. It is a plot of the actual data showing the data values versus the number of occurrences for each value. Judge the Process Capability (Cp) from the histogramCp is just OKCp is better than specCp is lean to leftCp is lean to rightToo scattered CpI

6、mplement Procedure1. Collect data; For example: Gear dimension produced by ABC factory as below; specification of this gear is 24.56mm:1234567891022.123.422.627.722.923.724.521.324.721.225.824.523.221.321.624.124.817.421.920.323.924.624.322.724.626.730.026.023.124.622.821.822.624.025.122.419.323.923

7、.621.525.023.624.924.826.423.926.618.323.225.321.725.023.521.724.327.229.025.023.822.322.228.024.621.625.224.826.727.628.525.824.625.322.527.525.524.824.623.818.819.925.124.822.626.624.125.023.420.621.326.322.924.421.523.123.428.922.4Implement Procedure2. Count the range: R=Xmax Xmin = 3

8、0.0-17.4=12.63. Set the group:Total data50-100100-250250Groups6-107-1210-20We set 10 groups in this example.Implement procedure4. Verify the min measurement unit: It is decided by decimal digits. Minimum measurement unit in this example is 0.1.5. Count h; h=R/10=12.6/10=1.261.3Implement procedure6.

9、Count the upper limit and lower limit: Lower limit of first group=17.4-(min measurement unit/2)=17.4-0.1/2=17.35; Lower limit of 2nd group=17.35+1.3=18.65; Detail Upper/lower limit: 1st group:17.35-18.65; 2nd group:18.65-19.95 3rd group:19.95-21.25; 9th group:27.75-29.05; 10th group:29.05-30.35Imple

10、ment procedure7. Count median; Group median=(Group upper limit + Group lower limit)/2 1st group median=(17.35+18.65)/2= 18.00 The rest may be deduced by analogy.Implement procedure8. Fill frequency table:groupUpper/lower limit valueMedianFrequencies117.35-18.6518.002218.65-19.9519.303319.95-21.2520.

11、605421.25-22.5521.9016522.55-23.8523.2020623.85-25.1524.5029725.15-26.4525.8012826.45-27.7527.108927.75-29.0528.4041029.05-30.3529.7019. Draw histogram.Implement procedure10. Analyze the histogram. This histogram belongs to normal distribution, so the process is considered as stable.QC 7 tools - Par

12、eto DiagramWhat is Pareto diagram?It is a diagram based on histogram and used to identify the “critical minor.Pareto diagram can be used to find out the major problem on quality, cost, lead time, safety (phenomenon); operator, machine, material, working (process).Pareto diagram procedureTake the def

13、ects found in a figure production for example, total 15854 products, including 216 defectives.1. Collect data2. Sort order (descending), and count accumulative percentage.NoCategoryDefectDefect %Accumulative Defect %1Dirt Mark7534.7%34.7%2Paint migration4721.8%56.5%3Scratch mark3918.1%74.5%4Excessiv

14、e flash2813%87.5%5Insufficient glue177.9%95.4%6White mark73.2%98.6%7Other31.4%100.0%Total216100.0%100.0%Pareto diagram procedure3. Draw X axis and Y axis and marking scale.4. Draw histogram.5. Draw accumulative curve.6. Analyze Pareto diagram and take corrective action. (Very important).QC 7 tools -

15、 Cause-and-effect diagramWhat is Cause-and-effect diagram?It is a tool to analyze the quality characteristics (effect) and the potential factor to effect the characteristics (cause).Key points1. Personnel from different Dept;2. Analyze the cause as detail as possible;3. Each quality characteristic n

16、eeds a cause-and-effect diagram;4. Verify the problem can be solved or not; if not, subdivide the cause.Implement Procedure1. 3-6 various dept representatives to form a group;2. Topic: for example, why does dimension of gear vary?3. Draw out the rib, set the major causeWhy does dimension of gear var

17、y?ManMachineMaterialMethodEnvironmentImplement Procedure4. Find out the detail cause and add to the diagram (“Brain Storm is recommended);5. Mark the cause that may be the root of the problem and take corrective action.Why does dimension of gear vary?ManMachineMethodEnvironmentMaterialWrong operatio

18、nNot enough trainingNo timely checkingPatrol interval too longLax disciplineInsufficient hardnessVarious hardnessDifferent suppliersImpure materialEquipment precisionHard to adjustInstable voltagePoor fixtureNo timely maintenanceNo operation instructionNoise Temperature variesInsufficient lightAnaly

19、sisFind out 3 major problems:1. Material: 5 different suppliers, not the same quality, and not stable;2. Person: New workers, not enough training results in wrong operation; 3. Method: No WI or WI content not related to actual work.QC 7 Tools - Scatter DiagramWhat is scatter diagram?A diagram to fin

20、d out whether there is any relationship between two variables by plotting the data in X-Y axle coordinates.Types of scatter diagramGenerally there are 4 types of scatter diagram:Positive correlation (X, Y);Negative correlation (X, Y);No correlation;Curve correlation.Key point1. Check if there is abn

21、ormal dot, find out the cause of the abnormal;2. Data should be enough (at least30)3. As data is always varying due to man, machine, material, method, environment, etc, we should sort the data to avoid effect. (level diagram).Implement procedure1. Verify the 2 variables to check and collect the data

22、 (at least 30 groups);2. Mark the dot on the X-Y coordinates;3. Judge the relationship.ExampleScatter diagram of motor continuous operation time (T) and velocity (V): Fig.4TVTVTVTVTV1330732513250192102517123208285142442020426165330893001523721197271594311102701623122191281515304112641722523185291456

23、29712257182182417830133QC 7 Tools - Control ChartWhat is control chart?Control charts are a means of graphing variation patterns from process or product characteristics so that corrective action may be taken if required.Normal distributionNormal distribution is a curve of which the center is protrud

24、ed, two sides of the curve are lower and symmetrical. We use two parameter to describe the normal distribution; (Mean value) and (standard deviation).Parameter and The normal curve moves to right when increases.=2.5=1.0=0.4Quality characteristics become more scattered accompanied with the increase o

25、f the value of .Theoretic basis to set UCL and LCLThe Central line (CL) of control chart is the mean value; Upper Control Limit (UCL) is mean value +3 and Lower Control Limit is mean value -3.+3+2+1-1-2-3CLUCLLCLRelationship between and defective percentage1 2 3 4 5 6 69.77%30.87%6.68%6210PPM233PPM3

26、.4PPM*Considering influences from various factors.*4.5 represents 0ppm defectives.Comparing 6 and 3, defective percentage reduced 20,000 times!Motorola request his supplier provide products with 6 quality; 3 and 6 3 6 Missing 20,000 E-mail per hourMissing 7 E-mail per hour15minutes unsafe drinking w

27、ater per day1minute unsafe drinking water per 7 months5000 incorrect surgical per week1.7 incorrect surgical per weekTwice wrong landing on main airport per dayOnce wrong landing on main airport per 5 years20,000 wrong prescription per year68 wrong prescription per year7 hours power cut per month1 h

28、our power cut per 34 yearsWhich kind of control chart to choose?How to choose control chart?Total SizeAttribute CharacteristicCL PropertyX-Rm ChartSample SizeUnit Sizec Chartu Chartnp Chartp ChartSample Sizex R Chartx Chart x R ChartVariablesAttributes1 UnitDefectivesDefectsStableVaryfixedVaryxxn1010n25Implement procedure1. Collect data; Generally data should be 100.2. Group the data; Group into 25 groups, 5data/group.3. Count x mean and t