321

Case Problems

• Problem A– Parts Out of Specification– Solution: Poor Quality

• Problem B– Capacity Issue– Solution: Utilize Idle Machine 1 9

10

Today

Problem A - Quality

Problem Statement:Customer has recently found 121 Torsion Bars (T-Bar) with the Diameter out of specification. This issue is a recurring issue and is driving high scrap and sort costs.

Torsion

UCL – 0.2190 mmLCL – 0.2177 mm

Fishbone Diagram

T-bar Torsion

Section Is Too Close

To The UCL

Process

MeasurementPeople

Operator Bias

Gage R+R Too High

Shot Peen Increases Torsion Size

Gage Repeatability and Reproducibility Before Correction

Parts Operator A (mm) Operator B (mm) Range ǀA-Bǀ (mm)

1 0.21858 0.21861 0.000030

2 0.21862 0.21864 0.000020

3 0.21864 0.21865 0.000010

4 0.21866 0.21886 0.0002

5 0.21867 0.21883 0.00016

Sum of Range: 0.00042

Gage Error = Sum of Ranges Spec. Limit: 0.0012 (Note: Gage Error equals the sum of ranges only for 5 pc. Study)

Gage Capability = Gage Error / Spec. Limit 35.0%

Beyond 10% Approval

Gage Repeatability and Reproducibility After Correction

Parts Operator A Operator B Range ǀA-Bǀ

1 -0.012 -0.013 0.0001

2 -0.002 -0.003 0.0001

3 -0.011 -0.011 0

4 -0.009 -0.009 0

5 -0.003 -0.003 0

Sum of Range: 0.0002

Gage Error = Sum of Ranges Spec. Limit : 0.005

(Note: Gage Error equals the sum of ranges only for 5 pc. Study)

Gage Capability = Gage Error / Spec. Limit 4.0%

Under 10% Approval

Fishbone Diagram

T-bar Torsion

Section Is Too Close

To The UCL

Process

MeasurementPeople

Operator Bias

Gage R+R Was Too High

Shot Peen May Increase Torsion Size

T-Bar Process Analysis

Pack110

Q Q Q Q Q

Dept. 30 Dept. 53

Cut Length

Rough Grind

Wash Shot Peen

Paint Serrate Finish Grind

Wash10 40 50 60 70 80 90 100

Quality Check Station Inventory

Sample Analysis (59 T-Bars)Bottom Half

Gage Diameter (mm) Occurrences

0.21770 0

0.21775 0

0.21780 0

0.21785 0

0.21790 0

0.21795 0

0.21800 0

0.21805 0

0.21810 0

0.21815 0

0.21820 0

0.21825 0

0.21830 0

Top HalfGage Diameter (mm) Occurrences

0.21835 0

0.21840 0

0.21845 0

0.21850 1

0.21855 8

0.21860 18

0.21865 22

0.21870 5

0.21875 1

0.21880 2

0.21885 1

0.21890 1

n

xx

n

ii

1

Six Sigma Analysis

where

xi = observation of a quality characteristic (such as time)n = total number of observationsxbar = mean

ΣSix Sigma Analysis

where

xi = observation of a quality characteristic (such as time)n = total number of observationsxbar = mean

59

59i = 10.21863 mm

xi =

Six Sigma Analysis

0.21750

0.21760

0.21770

0.21780

0.21790

0.21800

0.21810

0.21820

0.21830

0.21840

0.21850

0.21860

0.21870

0.21880

0.21890

0.21900

0.21910

UCL 0.21890

xbar 0.21863

LCL 0.21757

T-Bar X Chart

T-Bar Samples

T-Ba

r Gag

e Di

amet

er (m

m)

Capable process, but shifted to the high end of the specification

Target (0.21830)

Six Sigma Analysis

0.21775

0.21780

0.21785

0.21790

0.21795

0.21800

0.21805

0.21810

0.21815

0.21820

0.21825

0.21830

0.21835

0.21840

0.21845

0.21850

0.21855

0.21860

0.21865

0.21870

0.21875

0.21880

0.21885

0.218900

5

10

15

20

25

Must Move This Way

)28613.0(x

Left Torsion Right Left Torsion RightMicro Micro Micro Micro Micro Micro

USL 7.645 USL 5.560 USL 7.645 USL 7.645 USL 5.560 USL 7.645LSL 7.595 LSL 5.530 LSL 7.595 LSL 7.595 LSL 5.530 LSL 7.595Tol. 0.050 Tol. 0.030 Tol. 0.050 Tol. 0.050 Tol. 0.030 Tol. 0.050 Part Left Torsion Right

7.605 5.545 7.604 7.629 5.56 7.6280.29952 (7.608) 0.21852 (5.550) 0.29968 (7.612) 0.29981 (7.615) 0.21873 (5.556) 0.29999 (7.620)

(0.003) (0.005) (0.008) 0.014 0.004 0.0087.604 5.543 7.603 7.627 5.558 7.625

0.29951 (7.608) 0.21847 (5.549) 0.29956 (7.609) 0.2998 (7.615) 0.21852 (5.550) 0.29963 (7.611)(0.004) (0.006) (0.006) 0.012 0.008 0.014

7.604 5.544 7.604 7.628 5.559 7.6260.29953 (7.608) 0.21849 (5.550) 0.2996 (7.610) 0.2999 (7.617) 0.21884 (5.559) 0.29994 (7.618)

(0.004) (0.006) (0.006) 0.011 0.000 0.0087.605 5.545 7.604 7.626 5.562 7.626

0.2996 (7.610) 0.21853 (5.551) 0.29966 (7.611) 0.29989 (7.617) 0.21863 (5.553) 0.29989 (7.617)(0.005) (0.006) (0.007) 0.009 0.009 0.009

7.605 5.545 7.605 7.629 5.56 7.6260.29957 (7.609) 0.21852 (5.550) 0.29965 (7.611) 0.29989 (7.617) 0.2188 (5.558) 0.29991 (7.618)

(0.004) (0.005) (0.006) 0.012 0.002 0.0087.605 5.543 7.604 7.63 5.559 7.628

0.29956 (7.609) 0.2185 (5.550) 0.29969 (7.612) 0.29992 (7.618) 0.218777 (5.557) 0.3 (7.620)(0.004) (0.007) (0.008) 0.012 0.002 0.008

7.605 5.546 7.605 7.629 5.561 7.6290.29957 (7.609) 0.21854 (5.551) 0.2996 (7.610) 0.29993 (7.618) 0.21877 (5.557) 0.30004 (7.621)

(0.004) (0.005) (0.005) 0.011 0.004 0.0087.603 5.543 7.605 7.63 5.561 7.627

0.29956 (7.609) 0.21857 (5.552) 0.29963 (7.611) 0.29978 (7.614) 0.21871 (5.555) 0.29994 (7.618)(0.006) (0.009) (0.006) 0.016 0.006 0.009

7.603 5.542 7.603 7.628 5.56 7.6290.2996 (7.610) 0.21853 (5.551) 0.29966 (7.611) 0.29986 (7.616) 0.21888 (5.560) 0.29997 (7.619)

(0.007) (0.009) (0.008) 0.012 0.000 0.0107.603 5.544 7.604 7.6247 5.562 7.626

0.29966 (7.611) 0.21854 (5.551) 0.29963 (7.611) 0.29989 (7.617) 0.21875 (5.556) 0.29984 (7.616)(0.008) (0.007) (0.007) 0.007 0.006 0.010

Average 0.02387 0.0162 0.0229Laser to Micro Max Deviation

0.009

Laser to Micro Max Deviation

0.0160.006

Laser to Micro Average Deviation

0.0217 0.018 0.022

Laser to Micro Average Deviation

0.008

0.027 0.018 0.022

0.025 0.018 0.026

0.025 0.016 0.024

0.024 0.015 0.024

0.022

0.021 0.017 0.022

0.024 0.015 0.021

10

Δ Dia. After Shot Blast

0.0240.0150.024

0.023 0.015

1

2

3

4

5

6

0.022

0.024 0.015

Spec

1

2

3

4

After Grind / Before Shot Blast After Shot Blast

Part Laser Laser LaserLaser LaserLaserPart

1

2

3

4

Spec

7

8

9

10

5

6

5

6

7

8

9

10

7

8

9

Process Study – Grind to Shot Peen

Difference Between the Sizes

Difference Between the Sizes

Difference Between the Sizes

Difference Between the Sizes

Difference Between the Sizes

Difference Between the Sizes

Difference Between the Sizes

Difference Between the Sizes

Difference Between the Sizes

Difference Between the Sizes

Diameter grew by an average of 0.016 mm after the shot peen

Problem A Conclusion

• Define– T-Bar diameter Too Close to UCL

• Measure– Gage R+R was Poorly Calibrated

• Analyze– Xbar Chart

• Improve– Decrease Rough Grind by 0.016 mm

• Control– Keep Gage R+R Under 10%

Problem B: Capacity Issue

Problem Statement: Part B orders were eliminated, and an increase in Part A orders occurred. The department will be operating inefficiency.

OP170Wash

IncomingFrom Heat

TreatOP130

OP140OD Grind

(12.3 sec/pc)

OP140OD Grind

(12.3 sec/pc)

OP160Ball Groove

Grind(84 sec/pc)

OP160Ball Groove

Grind(84 sec/pc)

IncomingFrom Heat

TreatOP130

IncomingFrom Heat

TreatOP130

IncomingFrom Heat

TreatOP130

Bottleneck

Capacity issueDocument Process

Dept.1

Dept.9

Dept.10

Today

Part A

Part A

Part B

Evaluating the Process• Cycle Time

• Productivity

• Parts Produced

84 sec/part x 80 parts per cycle 1 hour 52 minutesWheel/dress cycle + 04 minutes Total 1 hour 56 minutes

Parts/Hour 40.0Operational Activity (Hours) x 6.3

252 Parts/Shift/MachineMachines/Shift x 2Total Parts Produced 504 Parts/Shift

Productivity 90.0%Shift Time x 7.0 hoursOperational Activity 6.3 hours

Products Manufactured v. Product Demand

504

612

108

Products Produced

Product Demand

Short of Demand

Demand – Manufactured = Surplus/Deficient of Parts 612 – 504 = 108

17.6%

Recommendations

3) Don’t Change2) Buy A New Machine1) Reprogram Idle Machine

Dept.1

Dept.9

Dept.10

Today

Part A

Part A

Part B

Redesigning The Process

1) Manufacture at Full Capacity2) Produce According To Demand

Dept.1 Dept.

9

Dept.10

Proposal

Part APart A

Part A

Problem B Solution

Minimal Costs Associated

Use Idle Machineand

Produce According To Demand

Inexpensive Change Over Process

Reprogram Machine Replace Part B Pads With Part A Pads

Impact of Labor Costs Using Two Machines v. Three Machines

Labor Cost/Hour $16.00Hours/Shift x 7.00Labor Cost/Shift $112.00Shifts/Year x 365.00Labor Cost/Year $40,880.00

Deficit/Shift 108 PartsTime Needed for Each Part x 84 SecondsOver Time Needed to Complete Order 1.29 HoursEmployee Wage 16.00/HourOvertime Employee Wage x 2.00Labor Cost/Day $41.28Days/Year x 365.00Over Time Labor Cost/Year $15,067.20

Total Annual Cost $55,947.20

Case Problems

• Problem A– Parts Out of Specification– Solution: Poor Quality

• Problem B– Capacity Issue– Solution: Utilize Idle Machine

1 9

10

Today

Part A

Part A

Part B

Questions?