# 7 QC tools (PowerPoint)

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```					          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
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%
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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 views: 474 posted: 2/11/2012 language: English pages: 10
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