60 CHAPTER 4 CASE IMPLEMENTATIONS 4.1 INTRODUCTION The Six Sigma approach to quality and process improvement has been used predominantly by manufacturing organisations since its inception. Presently, many service organisations are also utilising this methodology primarily because of its customer-driven basis. Manufacturing organisations build their Six Sigma efforts on an established foundation of measurable processes and set quality management programmes. In service organisations, the Six Sigma programme is introduced to establish and map the key processes that are critical to customer satisfaction. There are numerous manufacturing companies applying the Six Sigma to their diverse non-manufacturing processes, such as human resources, payroll, accounting, customer relations, supply chain management, safety and hazard engineering, organisation change and innovation because many of the methods used in Six Sigma are applicable to both manufacturing and non-manufacturing industries or services. All these methods are practiced to minimise not just process variation in manufacturing but also the variation of expectations to perception in service organisations. The differences between goods and services lead to service firms and goods-producing firms having different success factors for Six Sigma. The extent to which Six Sigma fulfils the quality gaps, leads to the improvement of the product or service quality. This is dependent on the
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60
CHAPTER 4
CASE IMPLEMENTATIONS
4.1 INTRODUCTION
The Six Sigma approach to quality and process improvement has
been used predominantly by manufacturing organisations since its inception.
Presently, many service organisations are also utilising this methodology
primarily because of its customer-driven basis. Manufacturing organisations
build their Six Sigma efforts on an established foundation of measurable
processes and set quality management programmes. In service organisations,
the Six Sigma programme is introduced to establish and map the key
processes that are critical to customer satisfaction. There are numerous
manufacturing companies applying the Six Sigma to their diverse
non-manufacturing processes, such as human resources, payroll, accounting,
customer relations, supply chain management, safety and hazard engineering,
organisation change and innovation because many of the methods used in Six
Sigma are applicable to both manufacturing and non-manufacturing industries
or services.
All these methods are practiced to minimise not just process
variation in manufacturing but also the variation of expectations to perception
in service organisations. The differences between goods and services lead to
service firms and goods-producing firms having different success factors for
Six Sigma. The extent to which Six Sigma fulfils the quality gaps, leads to the
improvement of the product or service quality. This is dependent on the
61
apparent challenges posed by the very nature and core premises of the
industry. Hence, it is necessary that the performance of the TPE model in both
manufacturing and service sectors be verified before a decision regarding its
suitability is taken.
Two case implementations are conducted to assess the performance
of the TPE model, one in the manufacturing industry and the other in the
service industry. In the manufacturing industry, this TPE model is
implemented to minimise the defect probability of the die casting operation
with the core objective of improving the productivity. In the service industry,
it is used to minimise the gap between customer expectations and perceptions
within an automotive service operation. The details of the studies are
presented in the subsequent sections of this chapter.
4.2 CASE IMPLEMENTATION - 1
4.2.1 About the Company
A South-India based automobile horn manufacturing company is
considered suitable for the application of this TPE model. The company
undertook casting of aluminium components to cater to the needs of various
industrial sectors. The apprehension of the company due to the rejections of
cast products has been tackled through use of the TPE model. A variety of
casting techniques are used by the company including aluminium pressure
casting of automotive components for their domestic as well as international
clientele.
The production process followed a batch-type production with
different lot sizes for the different components. The product range for instance
included governor housing for fuel injection pumps, heat-sink and field
moulds for alternators, oil pumps and pump body covers, fixing brackets for
62
car starters, and pivot housing for wiper motors. The company’s present
production facility is expanded to make castings for the textile and medical
field and created ring holders for ring frames, iron sole plates for electric
irons, and clam shells for surgical interconnect systems.
The major domestic clients of the company are Lakshmi Machine
Works (LMW), Lucus- India, MICO, Philips India, Pricol, TVS Motor
Company Limited and Wipro Infotech; while the international clients
consisted of TRICO, UK and Zinser, Germany to whom nearly 20% of the
overall production is supplied. The present production capacity of the
company is estimated at 920 tonnes per annum with state-of-art techniques in
the present production set-up. The production schedule is prepared against the
client order.
The company prefers to be one of the best suppliers by improving
quality of the product and meeting the order delivery commitments. The
company had its well equipped quality control department to assess the
quality of the castings in terms of dimensional variability, various casting
defects and handling damages. However, they were looking for a systemised
methodology for optimising the casting process to reduce the occurrence of
loss of productivity and the costs incurred in rejections and in payment of
penalties to the concerned customers.
4.2.2 About the Process
The various production processes surrounding components include
die casting, sand casting, permanent mould casting and investment casting.
The most widely practiced casting method is die casting because of its
inherent properties like a high volume of production at a low cost, high
precision rates, and excellent surface finish which eliminate post machining
63
requirements. However, a high cost of die and porosity in the cast product are
the issues that plague this industry.
The vital components of a typical aluminium pressure die casting
process are shown in Figure 4.1. The die casting process involves the use of a
furnace, raw material, die casting machine and die. The metal is melted in the
furnace and then, injected into the dies in the die casting machine. After the
molten metal is injected into the dies, it rapidly cools and solidifies to take its
final form, called the casting. The entire die casting process is pasteurized in
Figure 4.2.
Figure 4.1 Aluminium die casting process
64
Figure 4.2 Die casting process flow chart
The process cycle for die casting consists of five main stages,
which are explained below. The total cycle time is very short, typically
between 2 seconds and 1 minute.
4.2.2.1 Clamping
Preparation and clamping of the two halves of the die constitutes
the first process. Each die half is cleaned initially and lubricated to facilitate
the ejection of the next part. The lubrication time increases with the size of
the component, as well as the number of cavities and side-cores. Lubrication
may be required after 2 or 3 cycles, depending upon the material. Post
lubrication, the two die halves, attached inside the die casting machine, are
closed and securely clamped. Sufficient force must be applied to the die to
Raw Material
Preheating Ingots
Melting the Ingots
Keeping molten metal at set temperature
Furn
ace
Die cleaning
Die lubrication
Die closing
Die
Pouring molten metal in shot
chamber
Injecting molten metal into the die
Solidification
Die opening
Ejecting the casting
Trimming the casting
Final product
Rec
ondi
tioni
ng a
nd
addi
ng w
aste
to m
eltin
g
Die
cas
ting
mac
hine
65
keep it securely closed while the metal is injected. The time required to close
and clamp the die is dependent upon the machine. Larger machines (those
with greater clamping forces) require more time and this can be estimated
from the dry cycle time of the machine.
4.2.2.2 Injection
The molten metal, which is maintained at a set temperature in the
furnace, is subsequently transferred into a chamber where it is injected at high
pressures into the die. Typical injection pressures range from 1,000 to
20,000 psi. This pressure holds the molten metal in the dies during
solidification. The amount of metal that is injected into the die is referred to
as the shot. The injection time is the time required for the molten metal to fill
all the channels and cavities in the die. This time is short, typically less than
0.1 seconds, in order to prevent early solidification of any one part of the
metal. Proper injection time can be determined by the thermodynamic
properties of the material, as well as the wall thickness of the casting.
4.2.2.3 Cooling
The injected molten metal starts to cool and solidify as soon as it
enters the die cavity. The final shape of the casting is formed when the entire
cavity is filled and the molten metal solidifies. The die cannot be opened until
the cooling time has elapsed and the casting is solidified. The cooling time
can be estimated from several thermodynamic properties of the metal, the
maximum wall thickness of the casting, and the complexity of the die. A
greater wall thickness will require a longer cooling time. The geometric
complexity of the die also requires a longer cooling time because the
additional resistance to the flow of heat.
66
4.2.2.4 Ejection
The die halves are opened and an ejection mechanism pushes the
casting out of the die cavity after the predetermined cooling time has elapsed.
The time to open the die can be estimated from the dry cycle time of the
machine and the ejection time is determined by the size of the casting’s
envelope and should include time for the casting to fall free of the die. The
ejection mechanism must apply some force to eject the part since the part may
shrink and adhere to the die during cooling. Once the casting is ejected, the
die can be clamped shut for the next injection.
4.2.2.5 Trimming
The material in the die channel solidifies during cooling along with
the casting. This excess material, along with any flash that has occurred, must
be trimmed from the casting either manually via cutting or sawing, or through
the use of a trimming press. The time required to trim the excess material can
be estimated from the size of the casting’s envelope. The scrap material that
results from this trimming is either discarded or can be reused in the die
casting process. Recycled material may need to be reconditioned to the proper
chemical composition before it can be combined with non recycled metal and
reused in the die casting process.
4.2.3 Scope of the Study
The company being studied manufactures 58 varieties of products
of which invariably there is a higher defective percentage. Problems
persisting consist of the loss in productivity and customer orders not being
met on time. To keep the company on track, the production department used a
strategy of producing more components than the ordered levels to compensate
67
for the rejections. This exercise increased the cycle times for each component
and thereby, a loss in ROI. The nature of casting defects may be of two types:
one, the defect that is noticed immediately after casting the molten metal.
Such defects may be un-filling, gate broken; damage, weld, crack, un-wash,
rib broken, and metal peel off. The second category of defects is not
noticeable until the post machining processes are completed. Those defects
are porosity, blow holes etc. Eventually, these defects cause greater losses
than the former category in terms of money since they involve post machining
processes. Improving the organisational productivity is the foremost objective
for the research model being proposed in this situation. A cross functional
team is therefore, formed by the Head of the Quality Assurance department in
the company. The organisation’s objective is taken as the driver for this study
and iterated using the QFD concept to coincide with what needed
modification / improvement / reduction to achieve the goal. Then, the selected
improvement project is analysed and improved in the subsequent stages of the
research model. The flow chart deployed in Figure 4.3 depicts a summary of
the step-by-step activities undertaken.
4.2.4 TPE Stage 1: QFD Process
QFD technique intends to identify the possible ways to accomplish
the objective through the analysis of the HoQ matrix. The development of the
customer information table (horizontal matrix) is simplified with a single
objective as the requirement. In this study, the CCP analysis has not been
performed since the requirement considered in the matrix is of a unique
nature.
68
Generating solutions using 39 problem parameter and 40 inventive principles
Improve the problem
Control activities End
Is measurement
system available?
Contradiction matrix
Measure the problem
Analyze the problem
Contradiction analysis
Preparation of Innovative situation questionnaire
Function Modeling
Selection of viable project
Define the problem
Objective
Strategies
Strategy
Project plans
Start
Figure 4.3 TPE model in case implementation 1
That is, it would not fetch any useful information because each
organisation could have different objectives to run their business. A cause and
effect (C&E) analysis is carried out to sort the strategies to find out which
would influence the objective. In Figure 4.4, the strategies chosen from the
C&E analysis are cross referred with the objective. In the HoQ matrix shown
in Figure 4.4, the strategies S1 and S4 are found equally important to fulfil the
necessary objective. As a thumb rule, the strategy S1 (minimising the
defective fraction) has been chosen in order to continue.
69
S4 81 27 27
S3 27 9 27
S2 27 9 27
S1 27 27 81
S1 S2 S3 S4
Im
port
ance
Wei
ght
Min
imiz
ing
defe
ctiv
e f
ract
ion
Im
prov
ing
proc
ess
q
ualit
y
Im
prov
ing
empl
oyee
p
rodu
ctiv
ity
Min
imiz
ing
CO
PQ
Objective di Wi Strategies
Improving productivity 9 1 9 3 3 9
Weight Wj 0.375 0.125 0.125 0.375
Priority I II II I
Figure 4.4 QFD matrix – objective Vs strategies
4.2.4.1 Developing project plans to realise the strategy S1
The previous history of records showed that the rate of rejection
ranged from 0.72% to 14.53% of production due to various defects, but the
company target is 1.5%. Nearly 25 casting defects are reported in their record
as reasons explaining the defective products.
With the information in hand, the following project plans have been
formulated to mitigate the occurrence of defects in casting:
1. Process parameter optimisation
2. Die design analysis
3. Component design evaluation
4. Equipment capability analysis
70
Each project is explained in details to the top management as
shown below:
4.2.4.2 Process parameter optimisation
The die casting process handles hot metal. The metal temperature is
the first and foremost important process parameter which has greater
influence on defect formation like un-filling, and flash like the others. Other
operational parameters are injection pressure (first and second stages), die
coat and metal mixing ratio. For the case company, the aluminium alloy is the
principal material used for most of the components at different proportions.
A variation in temperature of the hot molten metal has greater
affinity to cause defects in the final product. Low temperatures result in
improper solidifications, whereas high temperatures cause excess casting
hardness, leading to defects like cracks. Next, an equally important parameter
is the injection pressure, which refers the pressure applied on molten metal
while pushing it into die cavity from shot chamber. Low pressure may result
in a partial solidification of casting due to delay in cavity filling. Excess
injection pressure may however, damage the gate or increase the gate
velocity, which contributes to the casting defect like porosity.
The next parameter of interest is the die coat, which is the medium
used to lubricate the hot die for the purpose of easy ejection after the
solidification process. With respect to the die coat, the attention is paid to
frequency of die coating and die coat material. Last but not the least, the metal
mixing ratio is one other important process parameter, which might contribute
to gas inclusions in the casting due to contamination of the recycled materials.
The ratio in which the scrap or trimmed materials are mixed with the new raw
material in furnace is however, of real interest.
71
The scope of this project proposal is to estimate the optimum
setting of the chosen parameters to obtain high quality casting with
reduced or eliminated defects.
4.2.4.3 Die design analysis
Dies are the custom tools used in this process where the molten
metal is injected to form a casting. The fundamental arrangement of a die is
illustrated in Figure 4.5. It is composed of two halves: the cover die, which is
mounted onto a stationary platen, and the ejector die, which is mounted onto a
movable platen. This design allows the die to open and close along its parting
line.
Figure 4.5 Die structure and design features
Once closed, the two die halves form an internal part cavity. The
cover die allows the molten metal to flow from the injection system, through
an opening, and into the part cavity. The flow of molten metal into the part
cavity requires several channels like venting holes, sprue, runners,
overflow-well and gates.
72
Apart from these hot metal channels, there are also cooling
channels designed in the dies to allow coolant medium water or oil to flow
through the die. These are located adjacent to the cavity and remove heat from
the die. Apart from these structural design parameters, there are other design
issues like the draft angle, and undercuts to ensure easy flow of molten metal
and accommodation of complex casting features. Selecting the material is
another aspect of designing the dies. Dies can be fabricated out of many
different types of metals. High grade tool steel is the most common and is
typically used for 100-150,000 cycles. However, steels with low carbon
content are more resistant to cracking and can be used for 1,000,000 cycles.
Other common materials for dies include chromium, molybdenum, nickel
alloys, tungsten and vanadium.
In a nutshell, the essential design features of dies are:
Hot metal channel; sprue, runners, gates and overflow
well
Air channel, venting holes
Cooling channels, coolant paths
Structural parameters, draft angle and undercut and
Die material.
A project may be formulated to evaluate the influence of
stated die design features on defect occurrences through the Six Sigma
and the TRIZ processes.
4.2.4.4 Component design evaluation
The production of defect free components in the pressure die
casting process solely depends on product design and development factors
73
like die design, operational parameters and materials used. But the probability
of defect occurrence is highly depending on the design complexity of the
product. For instance to cast components with high wall thickness, the
injection pressure should be more than enough to fill the deep cavity. But it
has the adverse effect on casting quality like gas bubble inclusion and
porosity.
Likewise, external rib-like shapes create extra designs on the die to
accommodate external slides, which not only increase the cost of die but also
the operational complexity. Some of design flaws resulting casting defects are
illustrated in Figure 4.6.
Poor part design Good part design Poor part design Good part design
The confidence interval for the population is calculated using the
Equation (4.8).
;1;Ve ee
1CI F Vn
(4.8)
where
;1;VeF = F ratio required for α (risk)
ve = error degree of freedom
Ve = error variance
ne = experiment trails = 54
In this study,
α risk is taken as 0.10
Confidence = 1 - risk
ve – degrees of freedom for error variance is 41 from table 5.1
Ve = 1929.65 from table 5.1
Fα (1, 41) = 2.84 (taken from f – ratio table)
110
Hence,
1CI (2.84) (1929.65)54
CI = 10.1
The estimated mean response is 489.58 and at 90% CI, the
predicted optimum output is estimated as:
[µGood - CI] < µGood
< [µGood + CI]
[489.58 – 10.1] < µGood < [489.58 + 10.1]
479.5 < µGood < 499.7
4.3 SIX SIGMA CONTROL STAGE
The real challenge for this research approach lies not in making
improvements to the process but in providing sustained improvement in
organisational productivity through process optimisation. Standardisation,
constant monitoring and control of the optimized process are needed to
maintain the improvements. Process control limits are obtained using the
optimum parameter levels for maintaining the process to free of defects.
Implementation of the aforementioned optimum factor levels resulted in an
improvement of process yield and reduction in defect probability. Moreover,
an iterative fashion in implementing the TPE model is found to be more
indispensable.
An extensive training programme for the personnel connected by
the process changes is conducted within the company to ease the
implementation of the TPE model. It is well known that real improvement
comes only from the shop floor. Process sheets and control charts are made so
111
that the operators could be prepared to take preventive action before the
critical process parameters and critical performance characteristics strayed
outside of the control limits. A complete database is prepared to maintain the
improvements to the results. Proper monitoring of the process helped to detect
and correct out-of-control signals before they resulted in a loss of
productivity.
4.4 CASE IMPLEMENTATION – 2
4.4.1 About the Company
Company ABC Ltd. (real name of the company is not revealed
here as per the Memorandum signed with the management) is an Authorized
Service Centre for TATA Motors’ range of passenger cars since 1995.
Located in a major industrial city in southern India, it is an exclusive five star
rated service centre by TATA Motors to cater to the service needs of the
TATA range of passenger cars—Sumo Grande, Safari, Aria, Indica, Vista,
Manza and Nano—with comprehensive in-house facilities and trained
manpower. The company services about 750 TATA cars every month and
puts in the best effort to offer a delightful service experience to each and
every customer.
The company provides the best possible assistance through a
dedicated and trained staff so that the customer can get more value out of the
car at all times. The primary services offered by this organisation are basic
services, mechanical overhauling, body repair works, painting and polishing,
followed by documenting services like insurance, reimbursement in case of
accidents and maintenance of previous service records. The service centre is
equipped with special tools and TATA original parts to support scheduled
maintenances, the running of repairs, major overhauls, body repairs and
painting jobs.
112
Design data collection medium
Identify target
customers
Selection of customers
and competitors
Customer data
collection
Data analysis
Priorit izing requirements
Ranking and weighing requirements
Choosing rectification
factors
Customer input planning
Customer centric process
Company centric process
Constructing HOQ
Ranking and
weighing
Correlation
Cus
tom
er p
lann
ing
mat
rix
Com
pany
pla
nnin
g m
atrix
Rel
atio
nshi
p m
atrix
Cor
rela
tion
mat
rix
Selection of Customer CTQ
QFD Process
4.4.2 Scope of the Study
The company has to be responsive to all customer issues and react
swiftly when satisfying them. Though the customised approaches are put into
effect at the service centre to address customer problems, the dynamic
behaviour of customer grievances made it difficult to address all of them
successfully. Given this situation, we implemented the TPE model designed
by this research study to improve customer satisfaction.
4.4.3 QFD Process
The activities undertaken in this step are summarised in the flow
chart depicted in Figure 4.20.
Figure 4.20 Activities in QFD process
113
This process started with customer input planning and progressed
with customer voice collection and analysis; rectification factors
identification, ranking and correlating the rectification factors, and ended with
the construction of a final HOQ. To begin with, the TPE model
implementation comprised of a series of meetings has been conducted in the
company with a deployment team being organised to introduce the model to
the company.
4.4.3.1 Customer input planning
Customer input planning involved the design of a data collection
medium, identification of target customers, choosing potential competitors
and examining the volume of data to be collected. There are many data
collection mediums available to collect customer requirements. The most
preferred way, however, is the Survey Design to record the real thoughts of
the customers. An important task in this phase entailed identifying “Who is
the customer?” for which, a brainstorming session is conducted to arrive at a
decision. A conclusion is drawn to collect information from the customers
visit the company to service their cars. It is decided that two potential
competitors C1 and C2 who are the real thrush-hold service providers on par
with company ABC Ltd. would be included. A survey is undertaken for 10
days within premise.
4.4.3.2 Customer centric process
The customers are supplied with the questionnaire format enquiring
about their present complaint/reason for their dissatisfaction, what they
expected, how the aforementioned competitors are performing compared to
ABC Ltd. and the latter’s overall performance.
114
The questionnaire was designed with nine headings: service
initiation, service advisor, in-service experience, service delivery, service
quality, user-friendly service, problems experienced, value added services and
service cost. Each section had three questions with a 10 point scale rating
starting from “1” for unacceptable quality; “5” for average quality and “10”
for outstanding quality. The customers are requested to rate the performance
of ABC Ltd. At the end of day 10, out of 430 customers visiting ABC Ltd.,
398 survey forms are filled and collected by the team.
The reason 32 forms are missing could be attributed to the lack of
interest on the part of the customers to provide information, or because the
customers are new. The survey forms are analysed as per the different aspects
illustrated in Figure 4.21 to assess the reliability of the data collected.
Figure 4.21 Survey contributions
115
It is noted that a major share of the contributions in the survey is
occupied by the most experienced operators. It is understood from the figures
that 42% of the input is from the operators who covered more than 1, 00,000
kilometres driving of their cars. Moreover, 50% of the survey results are
obtained from vehicles aged more than three years.
These two factors are assumed as the criteria for service
complaints. With respect to the levels of satisfaction, we proposed the
“Customer Satisfaction Index” (CSI) metric. If a customer is fully satisfied in
all aspects, then the customer can award rating “10” for all the 27 questions.
Hence, a total of 270 would indicate his CSI level (CSI = 270). All
the 398 results are arranged into four groups with respect to the percentage of
CSI as shown in Figure 4.22. The individual group analysis showed that the
average CSI is 19% for Group 1, 39% for Group 2, 65% for Group 3 and 88%
for Group 4 as given in Figure 4.23.
Figure 4.22 Customer satisfaction index
116
Figure 4.23 Average customer satisfaction index
The Customer-Competitive Performance (CCP) analysis is
performed to compare the performance of ABC Ltd with its competitors. The
statistics have been displayed in Table 4.14.
117
Table 4.14 Competitive performance analysis
Q.No. Question Company
ABC Ltd Competitor
C1 Competitor
C2 CSI Factor – Service Initiation
1 Rate time to speak service advisor 7.2 7.7 7.6 2 Reasonable time to schedule visit 9.0 8.5 8.9 3 Overall service initiation 8.3 8.7 8.6 CSI Factor – Service Advisor (SA)
4 Knowledge expertise 7.3 8.6 8.4 5 Understood problem with vehicle 7.1 8.3 8.9 6 Explanation of service to be done 8.4 8.9 8.1 CSI Factor – In-Service experience
10 Promptness in delivering vehicle 7.4 9.1 8.9 11 Processing for paying for service 8.4 8.1 8.4 12 Time to service vehicle 7.5 8.4 7.9
CSI Factor – Service Quality 13 Thoroughness in fulfilling requests 7.4 8.5 7.2 14 Quality of service performed 8.3 9.3 8.9 15 Availability of spare parts 9.2 9.1 9.3
CSI Factor – User-Friendly Service 16 Convenience of operating hours 9.2 9.1 8.3 17 Fairness of charges 8.4 8.8 8.1 18 Annual maintenance contract 7.6 8.9 8.2
CSI Factor – Problem experienced 19 Trouble free operations 8.4 8.8 8.1 20 Freedom from squeak and rattle 9.3 9.1 7.9 21 Ease of maintenance and repair 8.1 8.9 7.9
CSI Factor – Value added services (VAS) 22 On-road assistance 7.6 8.1 8.8 23 Mishap partnership 7.2 8.4 8.4 24 Provision of float units 8.3 8.2 8.5
CR4 Minimum time to service 7 0.163 7 8 7 8 1.143 B 5
CR5 Improve service quality 8 0.186 7 9 8 9 1.286 A 3
CR6 Nominal cost of service 7 0.163 7 8 7 8 1.143 B 6
128
Table 4.20 Potential customer CTQs
Priority RFj Rectification Factor W(RFj) Target
1 RF8 Work time management 0.23694 To improve
2 RF6 Supervision strategy 0.14927 To improve
3 RF5 Work schedule 0.14232 To improve
4 RF10 Man power adequacy 0.13452 To be enough
5 RF7 Layout/Facility planning 0.12929 To modify
Since all the selected CTQs have a strong cooperative relation
with CR3, it is required that one be selected from among them for
improvement in the next stage. The relative importance of each CTQ on rows
is expressed in the form of a percentage of the grand total in Table 4.21. It is
inferred that the real CTQ for ensuring the vehicle’s delivery as promised is
RF7 - LAYOUT / FACILITY PLANNING since it had the highest percentage
(51.16%) in terms of the relative importance with respect to CR3. The decision
on CTQ selection is also supported in the Correlation Matrix in which, RF7
had a cooperative correlation with the rest of the CTQs. Hence, any further
improvement in RF7 would result in an improvement in RF5, RF6, RF8 and
RF10.
129
Table 4.21 Relative importance matrix
Column Total Grand
total
Row
total 11.2 25.2 16.1 15.4 0.5 68.4 100
RF8 - Work time management 0.2 1 5 0.2 6.4 9.36
RF6 - Supervision strategy 5 0.1 0.2 0.1 5.4 7.90
RF5 - Work schedule 1 10 0.2 0.1 11.3 16.52
RF10 - Man power adequacy 0.2 5 5 0.1 10.3 15.06
RF7 - Layout / Facility
planning 5 10 10 10 35.0 51.16
CR3
Prompt vehicle delivery
RF 8
- W
ork
time
man
agem
ent
RF 6
- Su
perv
isio
n st
rate
gy
RF 5
- W
ork
sche
dule
RF 1
0 - M
an p
ower
ade
quac
y
RF 7
- La
yout
/ Fa
cilit
y pl
anni
ng
Row
tota
l
Perc
enta
ge
4.4.4 Six Sigma – TRIZ Process
4.4.4.1 Six Sigma Define phase
In this phase, a statement of the problem prevalent at present is
developed using the TRIZ Ideal Final Result (IFR) concept. Since IFR insists
on an ideal state of the problem, it makes problem solving akin to moving
from perfection to practice. In this case, the customer complaint regarding the
timing of vehicle delivery is found to have been greatly affected by the factor
“Layout and facilities planning”. Using IFR principles, the problem statement
is developed as:
130
“To plan and develop trouble-free, stakeholder-friendly
environment to assure customer satisfaction”
4.4.4.2 Six Sigma measure phase
In this phase the Sigma quality levels for customer complaints is
calculated. The objective is to compare the performance improvement after
the study with the past performance to justify the improvements, which could
result through this research approach. The total number of customer
complaints regarding dissatisfaction except those arising from vehicle–related
problems is collected from the company database and the Sigma quality level
is computed as follows:
Total number of complaints [C1]: 10648 Number of customers involved in the complaints [P1]: 6120 Average number of complaints per customers [P2]: C1 / P1
= 10648 / 6120 = 1.739 (Complaints)
Total number of customers visited during the year [P3]: 13600 Total number of possible complaints [C2]: P3 * P2
= 13600 * 1.739 = 23662 (Opportunities) Possible number of complaints per million customers [CPMO]: = (10648/ 23662)*1,000,000 = 450 000