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7 QC tools (PowerPoint)

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7 QC tools (PowerPoint) Powered By Docstoc
					          1. Pareto Diagrams: To get a handle on the real problem from among many
                                                                                           • Draw the dots ( ) clearly


                                                                                                                                  • Do not extend the line
• Fill in the period when data                                                                                                      above 100
                                         (cases)            n = 43 (cases)
  was collected, and the total                                                                      (%)
                                                            Period : March 1-30
  number of cases (n)                                                                           100
                                                      40    Author : Suzuki                                                       • Units above the scale
                                                                                                                                    numbers




                                                                                                          Cumulative percentage
                                                      30                                        80
• Make scale marks
  on the inside                  No. of problems                                                                                  • Write “ cumulative
                                                                                                60                                  percentage” here
                                                       20
                                                                                                40
• Write characteristic                                                                                                            • Decide scales so that the
  values
                                                       10                                                                           box of the finished
                                                                                                20
                                                                                                                                    diagram is approximately
                                                                                                                                    square
                                                        0                                       0
• Draw cumulative line
  for the first item                                                                                                              • Don’t forget a zero




• Don’t forget a zero



                                                                                                                                  • Even if the number of
                                 Figure 1 Pareto diagram for “Problems in QC circle activities”                                     “other” is high, it goes
                                                                                                                                    at the right

                                                   • Designate a figure number and title
         2. Cause and Effect Diagrams: To search out and organize all possible factors
                                                                                                      • Enclose the characteristic in a box
  • Select important factors, and enclose                                     • Insert numbers to
    the important ones in an oval                                               indicate the order in • Clarify the characteristic
                                      • Main branches must be                   which the important     Factor search type
             • Make about 4-8 main          independent of each other           factors seem to exert Counter measures development
               braches, and enclose                                             and influences           type
                                            • Make this angle about 75
               them in a box                                                                               • Don’t forget an arrowhead

                                          Methods                        Labor




                                                                                                                                     Watering the trees takes a long time
         4
               Don’t understand the                      Hard work,
               characteristics of trees                  so efficiency                            Needs two women
 5                                                       drops
              Wasteful watering                                                                           Hose is long
                                                                Being tired                        2
                                                                                        Hose is
  No watering standards           Don’t understand the                                  heavy      Faucets are far from trees
                                  watering conditions      Work done on hot days

         3                                                                          Hose has to be connected
                Hose has to be carried to far
                                                  Not enough           Long distance Long time needed to
     1                                          watering faucets                      connect to faucet
             Can only water with one hose
                                                                   6    Faucets are not of a standard type
                 Pipes are too small                                                       Long time needed to carry
                                  Low water pressure
                                                                       Storage area is far away
                                                   Facilities
                                                                                                       Date of work: August 10.
                                                                                                       Participants: Yanagitani, Yakushiji,
              Figure 2 Cause and effect diagram for “Time needed to water trees”                                     Ishida and Hosotani.

                  • The ends of branches must not be phenomena;
                    they must get down to the poor quality of the work        • Systematize factors                          • Note the data
                                                                                starting from main                             prepared, data
              • For medium and small branches, just a word or phrase is enough branches through medium                         revised and
              • For medium and small branches, levels are not necessary         to small                                       names of
              • Constantly ask “Why?” to increase the number of factors                                                        participants
• Draw the backbone using a heavier line
                                3. Graphs: To make data visible to the eye


Broken Line Graphs                                                                        • Draw the dots clearly           • Put in the target


• Insert the units in this position, in parentheses ( )                     (%)                    Improving dimension gauge
                                                                                      5                    Change tension
• Use a slightly heavier line for actual data




                                                                  Coil defect ratio
                                                                                      4
• Make scale marks on the inside
                                                                                      3                                             Target
• Indicate the characteristic
                                                                                      2
                                                                                            Make a jig to prevent
• If the nature of the countermeasure is indicated as                                       misalignment
                                                                                      1
  required, the relationship with line breaks will be clarified                                 Hold the core with tape
                                                                                      0
• Don’t forget a zero                                                                      1     2     3      4     5     6     7     8     9
                                                                                                                                     (months)
                                                                                      Figure 3 Broken line graph for “Coil defect ratio”
  Bar Graphs
                                                          (persons)

• Insert the units in this position, in parentheses ( )                                     80




                                                          Number of respondents (per 100)
• Indicate the characteristic                                                               60



• Make scale marks on the inside                                                            40



•Make bar width double the space between bars                                               20


                                                                                            0
• Don’t forget zero


• Arrange items in order of size, unless there is
 an inherently logical order




                                                                            Figure 4 Bar graph for “ Topics of conversation with friends”
   Pie Charts
                                                                              Very bad
                                                                                2%
• Use the topmost part of the chart as the
  point of departure                                                   Poor
                                                                       11%

                                                                                   Very good
• Indicate the name of the item                                                      19%

                                                            Ordinary
• Consider what cross-hatching patterns                       25%
  to use

• Make the hatching go from heavier to                                          Good
                                                                                43%
  lighter “very good,” “good,” etc.

• If necessary insert figures for
  percentages

• Arrange items in order of percentage,         Figure 5 Pie chart for “Evaluating of telephone manners”
  unless there is an inherently logical order
                                      Band Graphs



                      • Arrange items in order of size, unless there is an inherently logical order
                                              • Indicate characteristic


                  Did you get anything out of the QC circle conference?
                                      Percentage

                  0         20           40        60          80         100 (%)      • Insert the units

                                                                                       • Insert scale marks on
                         A lot                  Something        Not much
Keynote speech                                                                            the inside
                         (42%)                    (36%)           (22%)
                                                                                       • Join with dotted lines
                                                                       Not
                              A lot                  Something        much
Open discussion
                              (51%)                    (34%)          (15%)




  Success story                  A lot                   Something       Not
  presentations                  (61%)                     (30%)        much
                                                                        (9 %)

    Figure 6 Band graph for “Evaluating of QC circle conference program”


       • Consider what cross-hatching patterns to use          • If necessary insert figures for percentages
         (Make the more important items heavier)
4. Check Sheets: To take down data simply and prevent inspection omissions

      • Make boxes for filling in the required items
                • Decide on method of stratification
                            • Indicate items to be checked
                                           • Fill in data
                      Table 1 Check sheet for “defects in camera assembly process”
                                                                        LN 1238                     From 1 Feb.
   Product name         CS20-5D
                                                             Lot number LN 1239            Date     1992
   Process name         No.3 assembly line                              LN 1240                     To 6 Feb. 1992
                                                             Measuring _______
   Measuring Method     100 %, visual operation                                Recorded by:         Miki Tanaka
                                                             Instrument
                       Date / day     2/1           2/2          2/3        2/4            2/5       2/6
                                                                                                            Total
               Defect                 Mon.          Tue.         Wed.       Thu.            Fri.     Sat.
           Loose screws             ////         //// ////   //// ////   ///       ////    /                 33
      Dirt in distance sensor       ////                     //          //        ///                       12
        Exterior scratches          //            //// /     //          ///       ////                      18
         Soldering defect                         //                     //        /                          5
          Bonding defect            ////                     /           ////                                10
         Operating defect                         /          ///                   /                          5
             Gap defect                           //                     /                                    3
              Part lost             ///                                                                       3
             Exterior dirt                                   //                                               2
                Total                     18           20          20        17             16               91
        Number inspected            2037                                                  Percentage defects 4.5%
                                                       • Add totals
5. Histograms: To understand the form of a distribution, and compare it to a standard
                            • Indicate the number of times
                                    • Decide the horizontal and vertical scales so that the finished diagram will be approximately square
                                                            • Draw a line showing the average



                             30                                              x



                             25




                                                                                        Upper limit of standard
                                       Lower limit of standard

                             20                                                                                   n = 100
                                                                                                                  x = 300.76             • Indicate the requirement items
             No. of times




                                                                                                                  s = 7.29               n : no. of items of data
                                                                                                                                         x : average
                             15
                                                                                                                                         s : standard deviation


                             10                                                                                                          • Draw lines for the standard limits


                                                                                                                                        • The portion outside the standard
                              5
                                                                                                                                          limit may be cross-hatched for
                                                                                                                                          easier visibility

                              0
                                   270             290     300   280310    320      330 (˚C)                                             • Insert the units
                                                  Melting temperature
                                  Figure 8 Histogram for “Melting temperature of fuses”


                                                                       • Don’t forget a zero                           • Indicate the characteristic
                     6. Scatter Diagrams: To find the correlation between a paired data

                                                                           • Regression equation

                                                       • No. of items of data
                                                                • Correlation coefficient


• Insert the units                (kgf)
                                             20     n = 31
                                                    r = 0.702
                                             19

                                             18
                                                                                                y = 11.554+0.8184 x
                                             17
• Regression line
                                             16
                                  Strength




• Insert the characteristic                  15

                                             14
• Decide the horizontal and
  vertical scales so that the                13
  finished diagram will be
  approximately square                       12

                                             11

• Scale need not start at zero
                                                   1       2    3      4     5     6        7     8     9   10 (mm)
• Indicate the characteristic                                       Diameter of weld
                                             Figure 9 Scatter diagram for “Weld diameter and strength”

                                                                                                            • Insert the units
                 7. Control Charts: To investigate whether a process is stable or not
                                                                                                                     • Show points outside the control
• Indicate the kind of control chart           • Decide horizontal and vertical scales so that the                     limits by means of a    mark
  (at the centerline (CL) position)              distance between the UCL and LCL is about six
                                                                                                                           • Show explicit values for CL
     • Show subgroup size                        times the gap between subgroups
                                                                                                                             (centerline) and upper and lower
       n here                                                                                                                 control limits (UCL and LCL)
                                                        • Show points on x by means of a                  mark
              • Insert the units

                (mm)                                                                For analysis                 For control
                        n=4                                                                                        UCL = 54.117
                54

                53
            x                                                                                                        CL = 52.627
                52
                                                                                                                     LCL = 51.137
                51

                 6
                                                                                                                     UCL = 4.66
                 4                                           x                                             x
                                x x                                            xx
            R                              x             x                                                               CL = 2.04
                                                                       x                x      xx x   x
                 2                                                                  x                                x
                        x x                                      x x       x                 x                   x
                                       x        x x x
                            x
                 0
                       1           5               10               15                  20            25
                                                        Subgroup number
                                Figure 10 x - R control chart for “External diameter dimensions”

                                                                       • When the chart is for analysis, show the CL with a solid line
                     • Indicate the subgroups number
                                                                         and the UCL and LCL with dotted lines
                       (subgroup name, the data, and
                       so on may also be filled in)                    • When it is for control, show the CL with a solid line and
                                                                          the UCL and LCL with dot-dash lines (         )
    • Show points on R with an x mark; show points outside the control limits by means of a                                mark

				
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