7- qc tool

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QUALITY

CONTROL

8/3/2019 7- QC tool


What are the diff erent dimensions of quality?

Sl No

Dimension of pr oduct / Service

Meaning Measures Pr oduct Example Service Example

(Stereo Amplifier) (Checking Accoun at a bank )

1 Per for mance Pr imary pr oduct or service

character istics

Signal-to-noise ratio,

power

Time to pr ocess customer

requests

2 Features Added touches, bells and

whistles, secondary

character istics

R emote Contr ol Automatic bill paying

3 R elia bility Consistency of per for mance

over time

Mean time to f ailure Time var ia bility to pr ocess

requests 4 Dura bility Useful lif e Useful lif e (with re pair) K ee ping pace with industry

trends

5 Servicea bility R esolution of pr oblems and

complaints

Ease to re pair R esolution of err ors

6 R es ponse Character istics of human-to-

human inter f ace (timeliness,

Courtesy, Pr of essionalism

etc.)

Courtesy of dealer Courtesy of teller

7 Aesthetics Sensory character istics (e.g.

Sound, Feel, Look etc.)

Ok -finished pr oduct Appearance of bank lobby

8 R e putation Past per for mance and other

intangibles

Public opinion,

Advertisement

Past exper ience

9 Cost Competitive cost compared to

other competitors similar ty pe

of pr oduct (s)

Moderate cost R easona ble pr ocessing time

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Why should we now be concerned with

Quality?

Customer satisf action

To impr ove pr oductivity

To impr ove competitive position

To stay in business

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Quality Assurance / Quality Contr ol

Pr ocess

Man

In put Out put

Machine Mater ial Method Measurement Envir onment

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What is Quality Contr ol ?

Quality contr ol is ³the pr ocess

thr ough which we measure actual

quality per for mance, compare it with

a standar d, and act on the

diff erences´.

Tak en f r om quality Planning and Analysis by Juran

8/3/2019 7- QC tool


7 Quality Control (QC)tool

1. Check Sheet ---- Used for data collection. Decision-making and actions.(Mean you have some check point with blank s pace)

2 . Flow Chart ----- Pr ocess ste p by ste p. (Sequence of activity)

3. Cause-and-Effect Diagram (Fish bone Diagram/ Ishik awa Diagram)--- To

figure out any possible causes of a pr oblem.(R elation of eff ect with cause)

4. Histogram ----- Bar chart of accumulated data and pr ovides the easiest way toevaluate the distr ibution of data.(Pictor ial view of data)

5. Pareto Chart ---- Used to define pr oblems, to set their pr ior ity.

6. Scatter Diagram -----Shows a pattern of co-relation between twovar ia bles.(R elation Diagramme² only R elation with each other)

7. Control Chart -----Pr ovides contr ol limits whether pr ocess is in contr ol or not

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BENEFITS

ÁImproved work flow

ÁReduction in costs

ÁPrevention orientedÁDevelopment of a quality

consciousness

ÁWork with facts rather than opinions

ÁImprove decision making

8/3/2019 7- QC tool


1.CHECK SHEET

Used for data collection. Decision-making

and actions.

Mean you have some check point withblank space

Check point²visual

inspection/specification (L,W,H,M/Cing,etc)

USE THE COMMON SENSE

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2.FLOW CHART

Pr ocess ste p by ste p. (Sequence of activity)

START TO ENDSTART &END

ACTIVITY

DECISION

DIRECTION

HOLD

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3. Cause-and-Effect Diagram

(Fish bone Diagram/ Ishik awa Diagram)

To figure out any possible causes of a

pr oblem.(R elation of eff ect with cause)

M1 M2 M3

M4 M5 E

CAUSE EFFECT

8/3/2019 7- QC tool


HISTOGRAMPictor ial view of data

ÅR(R ange) =Max-Min

ÅClass(k ) =1+3.22log10 nÅClass Width=R+W/K

ÅW=Least count of measur ing infor mation

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4. HISTOG

RAM

Purpose of histograms:

ÅFact findingÅVisualization of data

ÅPr ovides a simple and common language

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ta bles.no Class

boundry

Tally

mar k s

f requency

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Height of a gr oup is 10,12,12,13,15,16,16,16,10,15,

Mak e a Histogram

Calculate std. deviation

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Constr uction of Histogram

Ste p 1: Gather the data or infor mation.

Ste p 2: R ank or der and tally data

Ste p 3: Pre pare the vertical and hor izontal axis of the

histogram.

Ste p 4: Fill in numer ic values on hor izontal axis.

Ste p 5: Fill in f requency values on vertical axis.

Ste p 6: Draw each f requency bar corres ponding to each

value.

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5.PARETO DIAGRAM Pareto analysis is based on the pareto

principle.

this principle was named for an italian

Economist.

His ideas was 80% problems can be races

to 20% of the causes

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PARETO

DIAG

RAM

Following steps are necessary to construct

a pareto chart.

Decide the number of classification

Calculate category percentage

Rank categories in descending order

Calculate the cumulative percentage

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6.SCATTER PLOT

This is only relation diagram

Only relation with each other

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Scatter Diagram shows relation between 2 variables.Positive correlation

An increase in y depends on increases

in x. If x is controlled, y naturally will

be controlled

Positive Correlation may be present

If x increases, y will increase

somewhat, but y seems to have causes

other than x

No correlation

There is no correlation between X and Y

Variable.

SCATTER PLOT

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Negative Correlation may be present

An increase in x will cause a tendency

for a decrease in y.

Negative correlation

An increase in x will cause a decrease in

y.

Therefore, as with positive correlation, xmay be controlled instead of y.

By knowing the relationship between X and Y variables, variation in one of them

can be predicted by knowing the other.

SCATTER PLOT

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7. CONTROL CHART

(VAR IABLE

&

ATTR IBUTE)

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Average & R ange chart ( X & R )

Ste p 1: Select subgr oup per iod & sample size

Ste p 2: R ecor d the data on the contr ol chart for mat.

Ste p 3: Calculate Mean ( X) and R ange (R ) for each

sample.

Ste p 4: Test distr ibution for Nor mality

Ste p 5:Calculate the central lines

R = R 1 + R 2 +««.. + R k

k X = X1 + X2+.««...+ Xk

k

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ANSWER S QUESTIONS BEFOR E CHOOSING A

CONTROL CHART ?

zWhat character istic is to be investigated ?

zWhat testing devise of gauges will be required ?

zWhat is the pur pose of the contr ol chart ?

zWhich chart will most eff ectively accomplish the pur pose:

A: Var ia ble Contr ol Chart [Moving R ange, Average

R ange ( X & R ), Average SD.( X & S), Moving

Average, Median R ange, Pre-Contr ol]

B: Attr ibute Contr ol Chart [Def ective ( p, n p), Def ect (c,u)]

zWhat sample size should be drawn? ( Risk, Sample to sample var iation, Within sample var iation, Cost)

zHow of ten sample should be drawn?

zHow sample will be drawn? ( Consecutive, R andomly)

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Difference between Common & Assignable Cause

Common Cause Assignable Cause(1) Inherent Var ia bility & remain (1) They occur inf requently in constant over time. an un predicta ble manner .

(2) Example: (2) Example:

i) Out put f r om a single esta blished i) Between operators /machine machines / diff erent batches of raw mater ial.

ii) Due to Tool wear / set up.

(3) Only a change in the system (3) They can be found,

will reduce that var ia bility. measured & eliminated.(4) Only management has the a bility (4) The machine operator is best a ble to mak e changes. to discover andmak e changes.

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How to decide which are important

characteristic?

zCustomer Cr itical

zPr oduct Cr itical

zPr ocess Cr itical

zUnder Study for Quality Impr ovement

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Nor mal distr ibution and standar d deviation

68%

95%

99.73%

1W 1 W 1W 1 W 1 W 1 W

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Purpose of Data gathering

ÁCan we mak e it r ight? (Machine / Pr ocess

Ca pa bility)

ÁAre we making it r ight? (Pr ocess Contr ol)

ÁHave we made it r ight? (Pr ocess Audit)

ÁCan we mak e it better? (Pr ocess Impr ovement)

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Intr oduction to Basic Statistics

Total for Member 2000

Mean (Average) = ------------------ = ------ = 400

Number of Members 5

Median (Middle Value) : Middle value in a gr oup when arranged

f r om lowest to highest.Mode (Most Occurr ing Value) : Mode is the most f requent

occurr ing value in a gr oup. When the data is arranged into a

histogram, the highest bar re presents the mode.

R ange : Diff erence between the lowest and greatest value.Standar d Deviation: W = § (X - X)2 /n (Population SD)

s = § (X - X)2 /n-1 (Sample SD)

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Organizing the f acts

Trend Chart

ÅSimple and basic tool

ÅShows a per iod-to- per iod picture

ÅUsed to monitor , what is ha ppening on certain

operations

ÅUsed to predict, what will ha ppen in the future.

7- qc tool

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