L. G OCH – F EBRUARY 2011 SPC & MSA Using Minitab.

35302520151050

39

34

29

24

Observation Number

Indi

vidu

al V

alu

e

I Chart for C1

X=30.60

3.0SL=37.36

-3.0SL=23.84

L. GOCH – FEBRUARY L. GOCH – FEBRUARY 20112011

SPC & MSA Using Minitab

AGENDAContinuous & Attribute Data IMR Charts Xbar & R Charts Xbar & S Charts

MSAs Using Xbar & S Charts for MSAs Non-Destructive Variable MSAs

(NOTE: Minitab will also Analyze Destructive Variable MSAs & Attribute MSAs)

SPC & MSA using Minitab.mtb

DATA PLOTTED OVER TIME

MO

NIT

OR

ED

C

HA

RA

CT

ER

IST

IC

UCL

Center Line

LCL

UCL = Upper Control Limit / LCL = Lower Control Limit

Plotted Data

THE BASIC CONTROL CHARTKEY COMPONENTS

Control Limits are Control Limits are NOT NOT Spec Spec LimitsLimits

COMMON CAUSES VS SPECIAL CAUSES

Individual-X & Individual-X &

Moving Range ChartMoving Range Chart

CONTROL CHARTSINDIVIDUAL /MOVING RANGE

Use: When only have 1 measurement per time period When want to chart Counts. When want to chart Percentages (%’s).

Do NOT use P-Charts if the values are <10% or subgroup sample size >100 since it violates basic P-Chart assumptions.

Need a minimum of 10 data points

Variation Short Term: Measures relatively rapid changes over

time (Moving Range chartMoving Range chart) Long Term: Measures relatively gradual changes over

time(Individuals chartIndividuals chart)

Charts are Based on a Subgroup Size of 1

I / MR CHART: STAT > CONTROL CHARTS > I-MR

Open worksheet Exh_QC.mtwExh_QC.mtw

I-MR Chart analyzes individual data over time.

I / MR CHART: STAT > CONTROL CHARTS > RUN CHART

Rule #1

Is there a shift at Observation # 25?Is there a shift at Observation # 25?

MINITAB EXERCISEINDIVIDUALS / MOVING RANGE OUTPUT

454137332925211713951

1050

1000

950

900

850

Observation

Indiv

idual V

alu

e

_X=936.9

UCL=1010.9

LCL=862.8

454137332925211713951

100

75

50

25

0

Observation

Movin

g R

ange

__MR=27.8

UCL=91.0

LCL=0

11

2

2

2

2

6

1

1

6

5

1

2

2

22

22

2

1

222

22

66

6

1

I-MR Chart of Weight

MINITAB EXERCISEINDIVIDUALS / MOVING RANGE OUTPUT

Group Group ColumColumn n AddedAdded

MINITAB EXERCISEINDIVIDUALS / MOVING RANGE OUTPUT

Press Press <Ctl> <Ctl> ee

MINITAB EXERCISEINDIVIDUALS / MOVING RANGE OUTPUT

454137332925211713951

1050

1000

950

900

850

Observation

Indiv

idual V

alu

e

_X=905

_X=973.3UCL=974.4

UCL=1041.8

LCL=835.6

LCL=904.8

1 2

454137332925211713951

80

60

40

20

0

Observation

Movin

g R

ange

__MR=26.09

__MR=25.75

UCL=85.23 UCL=84.13

LCL=0 LCL=0

1 2

5

6

5

1

5

I-MR Chart of Weight by Group

Xbar & R ChartXbar & R Chart

CONTROL CHARTSX BAR / R CHART

AdvantagesAdvantagesSensitive to changes in data

Limitation Limitation Unlike the Individual Chart, the Xbar Chart control limits do not represent the overall data range. They represent the range of the subgroup averages.

CONTROL CHARTSX-BAR / R CONTROL CHARTS

GATHERING DATAGATHERING DATADefine rational basis for subgroupingSelect sample size for the subgroupsSelect sampling frequencyNeed a minimum of 10 subgroups

VARIATIONVARIATION Short Term: Measures the variation within the

Subgroups based on the subgroup range (Range chart) Long Term: Measures the variation between the

Subgroups based on the subgroup average (X Bar chart)

XBAR-R CHARTS: STAT > CONTROL CHARTS > VARIABLES CHARTS FOR SUBGROUPS > XBAR-R

Open worksheet Camshaft.mtwCamshaft.mtw

MINITAB EXERCISE - XBAR / R CHARTS OUTPUT

What do the Charts tell us?

We need to look at the individual suppliers.

191715131197531

602

601

600

599

598

Sample

Sam

ple

Mean

__X=600.072

UCL=601.722

LCL=598.422

191715131197531

6.0

4.5

3.0

1.5

0.0

Sample

Sam

ple

Range

_R=2.860

UCL=6.048

LCL=0

1

Xbar-R Chart of Length

MINITAB EXERCISE - XBAR / R CHARTS

o Stack Data:Stack Data:Stack the 2 Suppliers so the data can be looked at together on the same chart

MINITAB EXERCISE - XBAR / R CHARTS

37332925211713951

602

600

598

Sample

Sam

ple

Mean

__X=599.548

__X=600.23UCL=600.321

UCL=602.474

LCL=598.775

LCL=597.986

Supp1 Supp2

37332925211713951

8

6

4

2

0

Sample

Sam

ple

Range

_R=1.341

_R=3.890

UCL=2.835

UCL=8.225

LCL=0 LCL=0

Supp1 Supp2

1

6

1

Xbar-R Chart of Lengths by Supplier

Xbar & S ChartXbar & S Chart

CONTROL CHARTSX BAR / S CHART

AdvantagesAdvantages Very sensitive to changes in data. Also, the center line of the S-Chart

provides a good estimate for the data’s standard deviation.

Limitation Limitation The Xbar Chart control limits do not represent the overall data range. They represent the range of the subgroup averages.

CONTROL CHARTSX-BAR / S CONTROL CHARTS

GATHERING DATAGATHERING DATADefine rational basis for subgroupingAn S-Chart is typically used when the

subgroup’s sample size is > 9Select sampling frequencyNeed a minimum of 10 subgroups

VARIATIONVARIATION Short Term: Measures the variation within the

Subgroups based on the subgroup stddev (S chart) Long Term: Measures the variation between the

Subgroups based on the subgroup average (X Bar chart)

XBAR-S CHARTS: STAT > CONTROL CHARTS > VARIABLES CHARTS FOR SUBGROUPS > XBAR-S

Open worksheet Bloodsugar.mtwBloodsugar.mtw

MINITAB EXERCISE - XBAR / S CHARTS OUTPUT

What do the Charts tell us?

We need to look at the individual people.

191715131197531

120

100

80

Sample

Sam

ple

Mean

__X=101.03

UCL=130.72

LCL=71.35

191715131197531

50

40

30

20

10

Sample

Sam

ple

StD

ev

_S=28.77

UCL=50.67

LCL=6.88

Xbar-S Chart of Glucoselevel

MINITAB EXERCISE - XBAR / S CHARTS

o Sort Data:Sort Data:Sort the data by SubjectID & Reading

MINITAB EXERCISE – I-MR CHARTS

16314512710991735537191

200

150

100

50

Observation

Indiv

idual V

alu

e

1 2 3 4 5 6 7 8 9

16314512710991735537191

60

45

30

15

0

Observation

Movin

g R

ange

1 2 3 4 5 6 7 8 9

1

1

66

6

155

51

66

5

1

1111

8

68

151

1

65

56

1

1

11

1

11

1

1

1

I-MR Chart of Glucoselevel by SubjectID

Xbar & S Charts used Xbar & S Charts used for MSA’sfor MSA’s

MSA: X BAR / S CHART

AdvantagesAdvantages Pictorial look at MSA results Measurement error can easily be calculated

% R&R and %P/T can easily be calculated Daily Calibration Data can be used

Limitation Limitation Will NOT detect measurement that varies by

nominal value (e.g. large parts having more or less measurement error than small parts)

MSA: X-BAR / S CHART

GATHERING DATAGATHERING DATANeed Multiple measurements per time periodCan use 1 or more PartsNeed a minimum of 10 subgroups

VARIATIONVARIATION S Chart: Displays the Measurement Error. A good

measurement system will be in-control Xbar Chart: Displays any Drift over time in the

average measurements. A good measurement system will be in-control for each individual Part.

MSA: X-BAR / S CHART

Multiple Multiple Measurements Measurements per Day on per Day on mostmost Days.Days.

1 Calibration Part 1 Calibration Part per Facilityper Facility

3 Facilities3 Facilities Sorted Sorted by Facility by Facility

Date & TimeDate & Time

Open worksheet Daily Calibration Daily Calibration Data.mtwData.mtw

XBAR-S CHARTS: STAT > CONTROL CHARTS > VARIABLES CHARTS FOR SUBGROUPS > XBAR-S

Open worksheet Daily Calibration Daily Calibration Data.mtwData.mtw

MSA: X-BAR / S CHART OUTPUT

Need to add the Measurement Error.

Nov-23Nov-16Nov-09Nov-03Nov-26Nov-13Nov-04Nov-29Nov-19Nov-09Nov-02

600

550

500

450

400

Date

Sam

ple

Mean

__X=511.8

__X=500.8

__X=538.8

UCL=594.3 UCL=604.2

UCL=560.2

LCL=429.3

LCL=397.4

LCL=517.5

DHM DSM GSO

Nov-23Nov-16Nov-09Nov-03Nov-26Nov-13Nov-04Nov-29Nov-19Nov-09Nov-02

100

75

50

25

0

Date

Sam

ple

StD

ev

_S=31.0

_S=27.5

_S=8.0

UCL=101.4

UCL=89.8

UCL=26.2

LCL=0 LCL=0 LCL=0

DHM DSM GSO

1

1

2222

1

1

1

Xbar-S Chart of Actual Measurement by Facility

Tests performed with unequal sample sizes

MSA: X-BAR / S CHART RESULTS

CommentsCommentsSpec is +/- 50. %P/T target is < 30%None of Facilities meet the measurement

error targetDaily Calibration Check procedures need

investigated since producing dramatically different results

Facilitly ~Sbar

Multiplier ~ Meas Error

%P/T

DHM 31.0 2.575 +/- 80 80/50 = 160%

DSM 27.5 2.575 +/- 71 71/50 = 142%

GSO 8.0 2.575 +/- 21 21/50 = 42%

Variables MSA Variables MSA (Non-Destructive Testing)(Non-Destructive Testing)

VARIABLES MSA: STAT > QUALITY TOOLS> GAGE STUDY > GAGE R&R STUDY (CROSSED)

Minimum RequirementsMinimum RequirementsMinimum 10 parts: ~3 at low end of

spec, ~4 parts in middle of Spec, ~3 parts at high end of spec (NOTE: some parts should be out of spec)

3 Operators (NOTE: if only 1 operator measures parts, 1 operator may be used for MSA)

3 Repeated Measurements

VARIABLES MSA: STAT > QUALITY TOOLS> GAGE STUDY > GAGE R&R STUDY (CROSSED)

VARIABLES MSA: STAT > QUALITY TOOLS> GAGE STUDY > GAGE R&R STUDY (CROSSED)

VARIABLES MSA: GRAPH RESULTS

Part-to-PartReprodRepeatGage R&R

100

50

0

Perc

ent

% R&R

% P/T

1.0

0.5

0.0

Sam

ple

Range

_R=0.342

UCL=0.880

LCL=0

A B C

14

12

10

Sam

ple

Mean

__X=12.201

UCL=12.551

A B C

LCL=11.852

10987654321

14

12

10

Part

CBA

14

12

10

Operator

10 9 8 7 6 5 4 3 2 1

14

12

10

Part

Ave

rage

ABC

Operator

Gage name: Gage 1Date of study: Feb 18. 2011

Reported by: Lisa GochTolerance: 8-16Misc:

67.1%

96.0%

14.6%20.9%

12.9%18.4%19.5%

27.9%

Components of Variation

R Chart by Operator

Xbar Chart by Operator

Measurement by Part

Measurement by Operator

Operator * Part Interaction

Gage R&R (ANOVA) for Measurement

VARIABLES MSA: SESSION WINDOW RESULTS

Measurement Error: +/- 0.78 (i.e. 1.55721/2 = 0.78)

Both the Part & the Operator significantly effect the part measurements.

SPC/MSA - SUMMARY

The reliability of Control Charts are dependent on the selection of Rational Subgroups. Pick the wrong subgroup and the results can be very misleading.

The reliability of MSAs are dependent on the selection of the actual Parts. Pick Parts with too much or too little variation between them and the results can be very misleading.