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Shainin technique - Overview

Dorian Shainin , an American famous statistician has developed thesetechniques based upon more than 50 years of his experience. There is afamous saying at Motorala, wherein these techniques are used to attain “sixsigma”

Shainin Philosophy is that

“Do not let the engineers do the Guessing,

Let the parts do the Talking”.

�Without Deming, the US, would not have had a quality philosophy;

�Without Juran, it would not have had a quality direction;

�Without Shainin, it would not have solved quality problems;

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Definition of Problem

Starter takes high current during load test(Run torque)in Starter

performance test stage in manufacturing assembly line.

� Result in Assembly Line rejection.

� Increase in Internal failure cost

�What is the problem ?

�What is the Effect of the problem?

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Shainin Problem solving

Speed, Efficiency and flexibility

Analysis

Shainin Tools : 1.Shainin Iso plot 2. Component Search

3. Paired Comparison 4. Shainin Full factorial 5. Scatter plot

GREEN Y – Current drawn more than specification in the Starter

Shainin Philosophy is that “Do not let the engineers do the

Guessing, Let the parts do the Talking

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�To ensure the capability of the

measurement equipment-

Performance test rig shainin

isoplot plotted.

� 30 Samples Performance

current values during load test

measured on two separate

occasions and plotted as shown

in fig.

�The result confirmed that the

discrimination ratio is greater

than 5 hence the accuracy of

the measurement system is

good.

Shainin’s Isoplot Method

316

318

320

322

324

326

328

330

332

334

336

338

340

342

344

346

348

350

316

318

320

322

324

326

328

330

332

334

336

338

340

342

344

346

348

350

Measurement 1 (Amps)

Measurement 2 (Amps)

M

Discrimination Ratio

D = Range / M

D = 31.7 / 4.87 = 6.50

M

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1st 2nd 3rd 4 th 5th

CHECK CHECK CHECK CHECK CHECK

1 331.9 332.0 332.2 332.6 333.2

2 332.5 334.2 334.6 333.5 332.0

3 335.2 332.4 335.5 334.5 336.2

4 333.6 334.5 335.2 334.2 334.2

5 333.5 332.6 330.3 333.6 332.5

6 332.4 333.2 332.5 334.5 335.1

7 358.2 358.6 359.4 360.2 360.5

8 362.3 360.2 356.6 358.2 356.2

9 359.6 357.5 359.2 358.2 358.2

10 360.2 362.5 359.6 358.2 359.2

11 359.2 358.2 357.2 356.8 358.6

12 357.4 357.2 358.2 356.5 356.5

SL.NO

Ball Park stage : 6 Good and 6 Bad Starters were taken for selecting Best of Best

(BOB) and Worst of Worst (WOW) samples for study .

SAMPLEINITIAL

READING

FIRST

READING

SECOND

READING

BOB 330.3 332.6 334.2

WOW 362.5 360.4 359.4

CONFIRMS

NOT ASSY

VARIATION

Component Search method

D = (Median WOW – Median BOB) = (359.4-332.6)

d = (Range of WOW + Range of BOB)/2=(3.1+3.9)/2

D/d = 26.8/3.50= 7.65

D/d ratio > 1.25,

Red X is not due to

Assembly variation

D/d Ratio:

Good remains Good

& bad remains bad

after reassembly

D/d ratio used to check whether the group of best and bad unit selected for experimentation really contains the Red X or Pink X.

Stage:1 Disassembly & Reassembly:

Stage:2 Test of significance:

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Sl No SWAPPING ON PRIORITY IN BOB IN WOW

1 INITIAL RUN 334.2 359.4

2 Fixing Bracket assembly 334.6 358.4

3 Reassemble and Rechecking 333.4 357.2

4 CE Bracket assembly 335.2 359.4

5 Reassemble and Rechecking 335.9 361.1

6 Armature assembly 337.6 360.5

7 Reassemble and Rechecking 335.6 359.4

8 Yoke assembly 358.9 332.4

9 Reassemble and Rechecking 336.2 359.2

10 Switch assembly 335.8 357.4

11 Reassemble and Rechecking 335.2 357.9

Component Search method

Elimination Stage :

Fixing bracket

assembly

Yoke

assembly

CE bracket

assembly

Armature

assembly

The following sub assemblies selected for swapping based on the

experience & knowledge and swapped in the assembly sequence.

Switch

assemblyReversal

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Component Search method

320

325

330

335

340

345

350

355

360

365

370

375

380

INITIAL RUN

Fixing Bracket

assembly

Reassemble

and

Rechecking

CE Bracket

assembly

Reassemble

and

Rechecking

Arm

ature

assembly

Reassemble

and

Rechecking

Yoke assembly

Reassemble

and

Rechecking

Switch

assembly

Reassemble

and

Rechecking

Yoke assembly

Reassemble

and

Rechecking

AMPS

Control Decision Limits : Mean (Bad)±2.776 d

UCLWOW

LCLWOW

UCLBOB

LCLBOB Control Decision Limits : Mean (Good)±(2.776 d

bar/1.81)

d bar = BOB range + WOW range / 2

Capping

Run

Capping Run

Capping

run test

conducted

to

reconfirm

the

Swapping

results are

repeated

Swapping result - Graph

� The decision limit for Swapping and product specification for Good & Bad are not same.

� This decision limit is decided based on the variation during disassembly and reassembly

of the chosen pair of Good and bad.

� It decides whether their response are interchanged during swapping.

� The decision limit will be different for different pairs of good & bad Whereas product specification

will remains same for all units.

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Paired comparison method

.

All the Parameters in

yoke assembly are

verified and results

are written in

ascending order and

the end count

counted to know the

significance impact of

the parameter

measured. From

Tukey test the

magnetic flux in yoke

assembly is the root

cause with

confidence level of

99.7%

This is comparing

both specified and

unspecified

features of good &

bad to find

presence of

significanct

difference if any.

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B (Better) VS C (Current) TEST

Flux

kM

Current

Amps

168.6 334.2

170.2 332.6

169.6 333.2

167.6 335.6

168.0 334.9

166.7 336.6

164.6 338.2

167.6 335.6

Suspected Good Flux

Flux

kM

Current

Amps

153.1 359.4

153.8 358.9

154.6 357.9

151.2 361.2

152.6 359.9

153.2 359.3

155.2 356.4

153.5 359.2

Suspected Bad Flux

� Magnetic flux (Kilomaxwells) indirectly proportional to the current when torque remains constant

� Lower the magnetic flux higher the current drawn for the same torque

Inference:

B vs C test is done to verify and confirm the findings. 8 Pairs of starters having flux of suspected

better and current values are assembled and Tukey test applied on the response-current drawn

Flux Current

170.2 332.6

169.6 333.2

168.6 334.2

168.0 334.9

167.6 335.6

167.6 335.6

166.7 336.6

164.6 338.2

155.2 356.4

154.6 357.9

153.8 358.9

153.5 359.2

153.2 359.3

153.1 359.4

152.6 359.9

151.2 361.2

16Endcount

With the

confidenc

e level of

99.98%

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Shainin - Full Factorial

� Shainin “Full factorial” can tell the direction in which the significant factor has to be modified

to get the best output when the factor is less than or equal to four.

� The Selection of Factor Levels - Adequacy of levels confirmed - through D/d Test Before

experiment

� Confirmation of Significance – through B vs C Test

� The details of the experiment results are shown in the Table

Factors Possible range

Voltage 800 – 900 V

D/d test used

To select levels of factor

To check whether the group of best and bad unit selected for experimentation really contains the Red X or Pink X.

Low

level

High

level

Low

level

High

level

Low

level

High

level

Low

level

High

level

800V 825V 800V 850V 800V 875V 800V 900V

156 160 152 163 153 164 152 172

152 153 156 156 158 160 156 168

148 158 148 160 150 167 148 165

Experiment-1 Experiment-2 Experiment-3 Experiment-4

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Test for Significance - D/d Test

Levels Experiment -1 Experiment -2 Experiment -3 Experiment -4

800 - 825 V 800 - 850 V 800 - 875 V 800 - 900 V

Low 156 152 153 152

Low 152 156 158 156

Low 148 148 150 148

High 160 163 164 172

High 153 156 160 168

High 158 160 167 165

D 6 8 11 16

d 7.5 7.5 7.5 7.5

D/d ratio 0.80 1.07 1.47 2.13

Advantage

� Voltage level of 825 – 850 as high level Not adequate for experiment- In case

experiment has been conducted with this level – we will find insignificance at the

end of experiment only – D/d ratio helps in avoiding that.

High level

between

875 to 900

to be chosen

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Voltage level from 875V to 900V gives best results with the

confidence level of 99%

Voltage Flux

875 164.6

880 166.7

885 168.5

890 168.9

895 170.2

900 171.6

Expected Good Voltage

Voltage Flux

800 152.1

805 153.1

810 154.2

815 155.4

820 156.6

825 158.1

Expected Bad Voltage

B (Better) VS C (Current) TEST

Tukey Test - End count calculation Voltage Flux

800 152.1

805 153.1

810 154.2

815 155.4

820 156.6

825 158.1

875 164.6

880 166.7

885 168.5

890 168.9

895 170.2

900 171.6

Endcount 12Inference:

With the

confidenc

e level of

99.7%

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334.48

339.5

349.2

355.4

359.4

152.2

160.4

168.4

164.2

158.0

145

147

149

151

153

155

157

159

161

163

165

167

169

800 825 850 875 900

Voltage

Magnetic Flux 1

330

335

340

345

350

355

360

365

370

Current

Realistic Mfg.

Tolerance

Target Value

Min

Max

�The purpose of scatter plot is to fine tune optimized parameter & determine the

design center and also the realistic tolerances of process parameter.

�Scatter plot drawn with voltage, magnetic flux and current value

�The result clearly indicates that the voltage value nominal 880V and maximum

voltage 898V gives better results

Shainin – Scatter Plot

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Implementation of Corrective Action

� Voltage specification fine tuned from 800V / 900V to

880V / 898V in the magnetizing process of yoke assembly.

� Poka Yoke introduced to prevent the process start when the

voltage is less than 880V. (Process starts only when the voltage

reaches 880V)

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Summary

� PROBLEM

� First the adequacy of the measurement system confirmed through Isoplot

� To identify what is wrong in the Red X - Paired comparison between good and

bad units is done. It revealed the deficiency in the specification of Magnetic flux.

� Automobile Gear reduction Starter takes high current during load test in performance stage

� Analysis summary

� Then to narrow down quickly on the part contributing to the defect - Component

search is done. Yoke assembly is found as a Red-X

� The finding is confirmed through B Vs C test

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Summary

� ACTION TAKEN

� RESULT

� Lower magnetic flux in Yoke assembly resulting high current in Gear reduction starter

� Magnetizing process specification optimized

� High current during load test problem eliminated.

� ROOT CAUSE

� The tolerance for the Significant process parameter is set using Scatter plot

� The process parameter contributing to the Flux level of the product is ascertained

through Factorial experiment

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� This paper explained the use of Shainin Technique to solve chronic issue

by modifying the process specification

� This case study emphasis's the Shainin principle of

“conformance to specification does not guarantee good quality” and

“Never hesitate to question the specification in case of problem

� In manufacturing industries, to eliminate the vital waste, the chronic

issues are to be eliminated by making the process more robust.

� Elimination of wastage is must for “All inclusive growth”.

Conclusion

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