Six Sigma Case Study

1. IMPROVING PROCESS PERFORMANCEIMPROVING PROCESS PERFORMANCE
BY REDUCING INPROCESS BY REDUCING INPROCESS
REJECTION USING SIX REJECTION USING SIX
SIGMA METHODOLOGYSIGMA METHODOLOGY

2. CONTENTSCONTENTS
INTRODUCTIONINTRODUCTION
METHODOLOGYMETHODOLOGY
CASE STUDYCASE STUDY
ANALYSIS AND RESULTSANALYSIS AND RESULTS
CONCLUSION AND RE COMMENDATIONS.CONCLUSION AND RE COMMENDATIONS.

3. INTRODUCTIONINTRODUCTION
As international competition is growing, every As international competition is growing, every
industry is trying to improve quality of the industry is trying to improve quality of the
product and in turn reduce rejection.product and in turn reduce rejection.
In-house rejection should be controlled as it In-house rejection should be controlled as it
affects COQaffects COQ
Six sigma methodology discussed in this paper is Six sigma methodology discussed in this paper is
the business philosophy that enables world-class the business philosophy that enables world-class
quality and continuous improvement.quality and continuous improvement.
This paper discusses the success story carried out This paper discusses the success story carried out
by the authorsby the authors

4. SIX SIX σσ METHODOLOGY METHODOLOGY
DMAIC Methodology is central to six sigma DMAIC Methodology is central to six sigma
improvement process.improvement process.
Specific tools are used to turn a practical problem Specific tools are used to turn a practical problem
into statistical problem,genrate a statistical into statistical problem,genrate a statistical
solution and then convert back into practical solution and then convert back into practical
solutionsolution

5. DMAIC FLOW CHARTDMAIC FLOW CHART
DEFINE
MEASUR
E
ANALYSE
PROCESS
OPPORTUNITY
LIKELY
BENIFITS
CURRENT
PERFORMANCE SOURCES OF
VARIABILITY
KEY VARIABLES RELATIONSHIPS
IMPLEMENTED
SOLUTION
PREDECTED
RESULTS IMPROV
E
CONTROL
CONTROL
VARIABLES
PLAN FOR
STABILITY

6. CASE STUDYCASE STUDY
A manufacturing unit producing wheel cylinder A manufacturing unit producing wheel cylinder
was facing a problem of rejection. The jobs were was facing a problem of rejection. The jobs were
rejected due to several reasons.rejected due to several reasons.
After studying the statistics of rejection data ,it After studying the statistics of rejection data ,it
was decided to Solve the problem by DMAIC was decided to Solve the problem by DMAIC
approach.approach.

7. DEFINE PHASEDEFINE PHASE
In this phase all the parameters related with the
process flow were studied.
The process flow chart is as follows,
Receiving casting from foundry department
Loading the casting at station 1 by
pneumatic feeder
continue

8. Mounting hole drilling operation
Drilling operation by Φ 3 drill
Tapping operation by M6 tap
Main bore drilling by Φ 15 solid carbide tool
Followed by reaming by Φ 15.87 reamer
Boot grooving operation by form tool
Unloading the job and placing it to
storage bin

9. MEASURE PHASEMEASURE PHASE
358620557161November
412429070319October
580434459265September
PPMRejected jobsTotal productionMonth

10. 02812Poor finish
351485M 6 damaged
01519Acidic etching
01025Groove undersize
7815Groove steps
82516Bore or tool mark
152509Face damaged
507076M 10 damaged
9085107Main bore shift
NO. OF JOBS REJECTEDDEFECT
DEFECTWISE REJECTION

11. ANALYSIS PHASEANALYSIS PHASE
Pareto for month of November.Pareto for month of November.
C
o
u
n
t
P
e
r
c
e
n
t
C1
Count
24.4 17.1 7.3 3.9 3.4
Cum % 43.9 68.3 85.4 92.7
90
96.6 100.0
50 35 15 8 7
Percent 43.9
O
t h
e r
b
o r e
t o o
l m
a r k
f a
c e d
a m
a g
e d
M
6 d
a m
a g
e d
T
h
r e a d
d
a m
a g
e d
M
a i n
b
o
r e s h
i f t
200
150
100
50
0
100
80
60
40
20
0
Fig.2 Pareto Chart of defects

12. Main causes of rejectionMain causes of rejection
From pareto diagram it can be seen that the From pareto diagram it can be seen that the
prime elements causing rejection of the jobs are,prime elements causing rejection of the jobs are,
1) Main bore shift.1) Main bore shift.
2) M10 damaged.2) M10 damaged.
Hence it was decided to find out the root causes Hence it was decided to find out the root causes
for this defects by plotting fishbone diagram.for this defects by plotting fishbone diagram.

13. Analysis of main bore shiftAnalysis of main bore shift
Cause and effect diagram for main bore shiftCause and effect diagram for main bore shift
BORE
SHIFT
Methods
Material
Machines
Personnel
lack of skill
new operator
belt tension
spindle feed
slide feed rate
hyd.oil leakage
casting defect
slide feed rate
predrilling
coolant flow
tooling
Fig.3 cause and effect diagram for bore shift

14. Analysis of M10 shiftAnalysis of M10 shift

Cause and effect diagram for M10 shiftCause and effect diagram for M10 shift..
m/o
shift
Methods
Material
Machines
Personnel
no fixed
operator
lack of skill
runout of slide
air pressure
belt tension
casting defect
tool material
clamping pressure
Fig.4 cause and effect diagram for M10 shift

15. IMPROVEMENT PHASEIMPROVEMENT PHASE
Implementation planImplementation plan
ImplementedHydraulic leakage
corrected
Hydraulic leakage
causing pressure
drop
Bore shift
ImplementedV block rework
for perfect
clamping
V block damagedBore shift
ImplementedProper fettling of
liquid metal
during casting
process
Excess material
job
M 10 shift
ImplementedReservoir added
to reduce
pressure drop
Air pressure drop
below 0.8 Mpa
M 10 shift
Present statusCorrective actionCurrent statusConcerned
parameter

16. ResultResult
Improvement in sigma ratingImprovement in sigma rating
3.6215250.001525899090December
2.9235860.0035857161205November
2.9641240.0029770288299October
2.7558040.0058459265344September
Sigma
rating
ppmRejections
per unit
No. Of
Units
Produced
No. Of
rejections
Month

17. Saving in materialSaving in material
Approximate annual rejection before study=3840 unitsApproximate annual rejection before study=3840 units
Approximate proposed annual rejection after Approximate proposed annual rejection after
implementation=1080 unitsimplementation=1080 units
Proposed reduction in annual rejection raty=2760 unitsProposed reduction in annual rejection raty=2760 units
Proposed saving=2760 x 15.5 =Rs.42780/annumProposed saving=2760 x 15.5 =Rs.42780/annum

18. CONCLUSIONCONCLUSION
The purpose of this study is to give more insight The purpose of this study is to give more insight
to six sigma methodology.to six sigma methodology.
Comprehensive quality management system is Comprehensive quality management system is
required to achieve six sigma levelrequired to achieve six sigma level
Case study shows that sigma level for a Case study shows that sigma level for a
manufacturing unit increased to 3.62,hence more manufacturing unit increased to 3.62,hence more
emphasis is required to improve the quality.emphasis is required to improve the quality.