ARCHIVES
of
ISSN (1897-3310)
Volume 11
Issue 2/2011
22–28
FOUNDRY ENGINEERING
5/2
Published quarterly as the organ of the Foundry Commission of the Polish Academy of Sciences
Application of the Pareto chart and Ishikawa
diagram for the identification of major
defects in metal composite castings
K. Gawdzińska a, *
Institute of Basic Technical Sciences, Maritime University of Szczecin, ul. Podgórna 51/53, 70-205 Szczecin, Polska
* e-mail: k.gawdzinska@am.szczecin.pl
P
a
P
Otrzymano 11.04.2011; zaakceptowano do druku 26.04.2011
Abstract
This author discusses the use of selected quality management tools, i.e. the Pareto chart and Ishikawa fishbone diagram, for the description
of composite casting defects. The Pareto chart allows to determine defect priority related with metallic composite castings, while the
Ishikawa diagram indicates the causes of defect formation and enables calculating defect weights.
Key words: quality management tools, composite casting defects.
1. Introduction
Metallic composite castings find numerous applications in
many industries due to their enhanced desired properties, e.g.
reduced mass and higher durability of the ready product or
increased thermal resistance. These materials are constantly being
improved. The results of research on metallic composite castings,
with topics from properties to recycling, are available in a wide
range of publications at home and abroad [1–9].
Manufacturers face new challenges concerning the quality of
composite materials as technologies continue to be developed.
Quality control, due to the complex structure of composites [3, 6–
7, 9], is sometimes very difficult, requiring the proper choice of
diagnostic methods and the identification of quality determinants
in terms of materials and technology.
Good product quality is best confirmed by the user, while the
manufacturer is obliged to make a good product, i.e. the one that
meets the expectations of the user. Products have to be checked
for quality. Quality inspection as defined in [10] is checking
whether the product satisfies specific requirements.
Management tools used for the collection and processing of data
related with various aspects of quality [10–11, 13] are helpful in
quality inspection. These are instruments for monitoring and
diagnosing the processes of design, manufacturing, control,
assembly and any other activities that take place in the product
life cycle. These tools include [10, 14-15]: block diagrams,
control sheets, Ishikawa fishbone diagrams, Pareto charts,
histograms, variable correlation diagrams and Shewhart control
cards.
This work makes use of control sheets for making the Pareto
chart and fishbone diagram, which helped identify causes of
defects occurring in metallic composite castings. The objective
was to prioritize these defects, a basis for further research aimed
at the defect description by selected research methods, fully
specifying the quality properties of composite castings.
ARCHIVES OF FOUNDRY ENGINEERING Volume 11, Issue 2/2011, 23–28
23
2. Description of the problem
The Pareto chart is based on empirically ascertained
regularity that in many cases in nature, technology, human
activities etc. 20–30% of causes (factors) results in 70–80% of
effects (Fig. 1). In case of quality control, the identification of
these major causes allows to determine directions of actions that
may very effectively contribute to the improvement of processes
and product quality enhancement [11]. The chart is built in the
following stages [10, 13-14]:
– gathering the relevant information on the process under
examination;
– identification of the quantity enabling measurement of the
process result in view of the problem considered;
– prioritization of causes, from the gathered information and
knowledge of the process, based on the impact on the
process result;
– determination of cumulative percentage values of each
cause;
– drawing a line connecting the points representing the
cumulative values;
– analysis of the chart in order to indicate the group of
primary causes that should be examined (or eliminated,
restricted etc.).
problem and the analysis of the results (effects) caused by these
interrelations. The method was created to recognize the relations
between customer requirements and the quality of the final
product, facilitating the identification of the product properties
[10–12, 16]. The diagram puts logically and chronologically the
causes of or actions related to the defined problem (Fig. 2).
However, the classical Ishikawa diagram does not contain
quantitative data. The works [10–11] suggest, while the work [12]
successfully implements the suggestion to supplement the
diagram with weights of each cause. Following the identification
of the set of main causes and the set of subcasues, each main
cause and sub-cause is attributed a relevant weight, then absolute
values of sub-cause weights are calculated. Finally, the Ishikawa
chart is supplemented with individual weights [12-14]. The
weights of individual causative factors are determined by using
the matrix of pair comparison based on the principle: if one of the
comparable factors is found to be more important, it is marked as
1; the other factor gets 0. If both factors are regarded as equally
important, both are valued at 0.5. To make the evaluation more
precise, the marking scale may be extended [10,12–16], by
adopting the values 0; 0.25; 0.5; 0.75; 1.
Cause 2
Cause 1
Subcause 1.1.
Cause 3
Subcause 3.1.
Subcause 2.1.
Subcause 3.2.
PROCESS RESULT
OR EFFECT
Subcause 4.1.
100%
80%
3 causes lead to
80% effects
50%
Cause 4
Cause 5
Cause 6
Fig. 2. The Ishikawa chart [11,14]
3. Research
1
2
3
4
5
6
cause no
Rys. 1. The Pareto chart illustrates the non-homogeneity of causeeffect distribution and indicates that relatively few causes bring
about most of the effects [11]
Another tool of quality management used in this work is the
cause and effect diagram, also known as the fishbone diagram or
Ishikawa diagram [10]. Applied in graphically represented cause
and effect relationships, it helps separate the effects from causes
of a problem and to perceive the complexity of the problem.
Ishikawa [11,13–15] developed the cause and effect diagram in
which the analysis starts from the identified effect (e.g. defect,
failure or another undesired condition) and leads towards the
identification of all possible causes of that effect. Among the
causes, Ishikawa identified five main components – referred to as
5M: manpower, methods, machinery, materials, management.
Each component breaks down into individual causes that should
be considered separately as problems to be solved [11]. The
cause-and-effect diagram is a graphical analysis of the impact of
various factors and their interrelations causing a definite quality
HT
24
Nearly all defects of metal composite castings can be
described by methods characterizing casting defects in traditional
materials [16]. However, some defects occurring in composite
castings are specific for this group of materials, e.g. variable
dimensions of the reinforcement phase particles, insufficient
infiltration of metal in the reinforcement structure or
reinforcement fractures. This work aims at separating the most
important (i.e. most common) composite casting-specific defects
and the identification of the causes of their occurrence.
Table 1.
List of specific defects in metal composite castings based on
a control sheet
TH
Defect
Distribution non-homogeneity of reinforcement
phase in casting
Shape non-homogeneity
of reinforcement phase
Size non-homogeneity of
reinforcement phase
Cumulative values
mass
%
[kg]
Notation
Defective
casting
mass [kg]
%
1A
14.341
41.63
14.341
41.63
2A
7.348
21.33
21.689
62.93
3A
4.816
13.98
26.505
76.94
ARCHIVES OF FOUNDRY ENGINEERING Volume 11, Issue 2/2011, 23–28
Quantitative nonhomogeneity of
reinforcement phase
Gas porosity
Shrinkage cavities
Incorrect matrix structure
Reinforcement fractures
Reinforcement broken
off
Precipitated gas bubbles
Occluded gas bubbles
Foreign body in
composite structure
Matrix structure not
bonded
Delaminations
4A
1.508
4.38
28.013
81.32
8C
8D
7B
5A
1.343
1.140
1.005
0.871
3.90
3.31
2.92
2.53
29.356
30.496
31.501
32.372
85.22
88.53
91.45
93.98
5B
0.742
2.15 33.114
96.13
8B
8A
0.493
0.338
1.43 33.607
0.98 33.945
97.56
98.54
7A
0.248
0.72 34.193
99.26
6A
0.176
0.51 34.369
99.77
6B
0.079
0.23 34.448
100.00
Based on data from control sheets, defective composite
castings were classified by mass in the decreasing order as shown
in Table 1. The other columns of this Table include, respectively,
cumulative values needed to make the Pareto chart, presented in
Figure 3.
100%
50%
0
1A 2A 3A 4A 8C 8D 7B 5A 5B 8B 8A 7A 6A 6B
Fig. 3. The Pareto chart for specific defects of castings of metal
composite materials based on Table 1
It follows from the Pareto chart that approximately 80% of the
mass of defective castings stem from three defects: distribution nonhomogeneity of reinforcement phase in the casting, shape nonhomogeneity of reinforcement phase and size non-homogeneity of
reinforcement phase. The remaining defects had no influence on the
defect indicator, as they appeared sporadically.
Table 2 presents the weights of each primary cause, calculated
from comparison matrices [10–11] broken down according to 5M
approach.
Table 2.
Matrix diagram for the three defects: 1A (distribution nonhomogeneity of reinforcement phase in the casting), 2A (shape nonhomogeneity of reinforcement phase), 3A (size non-homogeneity of
reinforcement phase)
Factor
1A
2A
3A
Σn
Σn
Σn
Material
0.5
0.142 0.75
0.2
1
0.266
Method
0.5
0.142
0.5
0.133
0,5
0.133
Manpower
Management
Technological
stand
Total
0.75
1
0.214
0.285
0.5
1
0.133
0.266
0.75
3.50
0,5
0,75
0.133
0.2
0.214
1
≈1
3.75
0.266
1
0.266
≈1
3,75
≈1
Standardized weights of the main causes (factors) are placed in
the Ishikawa diagram (Figures 4, 5, 6) in the circles (under the
terms: manpower, material, method, management, technological
stand (machinery)). The upper value in the circle represents the
relative weight referring to the given factor, the lower value
represents the absolute weight referring to the whole group. In case
of the primary causes both weights in the circle are equal. The
comparison matrix was used (Tables 3, 4, 5) in determining
secondary causes (subcauses). Their relative and absolute weights
are given in the circles placed in the Ishikawa chart (Figures 4, 5,
6).
Table 3.
The matrix diagram of the causes leading to the defect
‘distrubution non-homogeneity of reinforcement phase in the
casting’
1A
Management
Σn
No information flow
0.5
0.166
No proper communication between workers
0.5
0.166
Too high work pace required
0.75
0.25
Incorrectly prepared technological
0.75
0.25
documentation
Lack of motivation in workers
0.5
0.166
Total
3.0
≈1
1A
Manpower
Σn
Insufficient qualifications
1
0.363
Insufficient technological regime
1
0.363
Workers mentally and physically unfit
0.75
0.272
Total
2.75
1
1A
Method
Σn
Improperly developed technological process
0,75
0.428
Improper methods of technological process
1
0.571
control
Total
1.75
1
1A
Materials
Σn
Inadequate properties of the matrix material
0.75
0.375
Inadequate reinforcement phase
0.5
0.25
Inadequate wetting angle in the
0.75
0.375
reinforcement phase-matrix system
Total
2.0
≈1
1A
Technological stand (Machinery)
Σn
Improper calibration (causing e.g. too fast
1
0.363
gas flow)
Too high or too low temperature of the heater
0.75
0.272
Improperly selected technological machinery
0.5
0.181
Improperly selected technological fittings
0.5
0.181
Total
2.75
≈1
ARCHIVES OF FOUNDRY ENGINEERING Volume 11, Issue 2/2011, 23–28
25
IIncorrectly prepared
technological documentation
0,25
0,071
Too high
work pace
required
No proper
communication
between workers
0,166
0,047
0,363
0,077
Lack of motivation
in workers
0,166
0,047
0,25
0,071
Insufficient
qualifications
Inadequate wetting angle
in the reinforcement phasematrix system
No information
flow
Insufficient
technological
regime
0,166
0,047
Workers mentally
and physically unfit
0,272
0,058
0,363
0,077
Management
Inadequate
properties of the
matrix material
0,375
0,053
0,375
0,053
0,25
0,035
Materials
Manpower
0,285
0,285
0,142
0,142
0,214
0,214
0,214
0,214
Technological
stand (Machinery)
Improperly selected
technological machinery
Improper calibration
(causing e.g. too fast
gas flow)
0,363
0,077
0,181
0,038
0,181
0,038
0,272
0,058
0,142
0,142
DISTRIBUTION NONHOMOGENEITY OF
REINFORCEMENT
PHASE IN CASTING
Method
Improper methods of
technological process
control
Improperly selected
technological fittings
Too high or too low
temperature of the
heater
Inadequate
reinforcement
phase
0,571
0,081
0,428
0,060
Improperly developed
technological process
Fig. 4. Weighted Ishikawa diagram for the defect: distribution non-homogeneity of the reinforcement phase in the casting
Table 4.
The matrix diagram of the causes leading to the ‘shape nonhomogenity of reinforcement phase in the casting’
1A
Management
Σn
0.5
025
No information flow
0.25
0.125
Too high work pace required
Incorrectly prepared technological
0.75
0.375
documentation
0.5
0.25
Lack of motivation in workers
Total
2
≈1
1A
Manpower
Σn
0.5
0.333
Insufficient qualifications
0.5
0.333
Insufficient technological regime
0.5
0.333
Workers mentally and physically unfit
Total
1.5
1
26
Method
Improperly developed technological process
Improper methods of technological process
control
Total
Materials
Inadequate properties of the matrix material
Inadequate reinforcement phase
Total
Technological stand
Improper calibration (causing e.g. too fast gas
flow)
Too high or too low temperature of the heater
Improperly selected technological machinery
Improperly selected technological fittings
Total
ARCHIVES OF FOUNDRY ENGINEERING Volume 11, Issue 2/2011, 23–28
1A
0.5
Σn
0.4
0.75
0.6
1.25
1A
0.75
1
1.75
1A
1
Σn
0.428
0.571
≈1
Σn
0.75
0.333
0.5
0.5
0.5
2.25
0.222
0.222
0.222
≈1
Incorrectly prepared
technological documentation
0,375
0,099
No
information
flow
0,25
0,066
Too high work
pace required
Inadequate
reinforcement phase
Lack of motivation
in workers
0,25
0,066
0,571
0,114
Inadequate
properties of the
matrix material
0,125
0,033
0,333
0,044
0,333
0,044
0,428
0,085
Management
Insufficient
qualifications
Insufficient
technological
regime
Manpower
Materials
0,266
0,266
0,133
0,133
0,2
0,2
0,266
0,266
Improperly selected
technological fittings
Improperly selected
technological machinery
0,222
0,059
Technological
stand
0,222
0,059
0,222
0,059
0,333
0,088
Workers mentally
and physically unfit
0,333
0,044
0,133
0,133
SHAPE NONHOMOGENEITY OF
REINFORCEMENT PHASE
Method
Improper methods of
technological process
control
Too high or too low
temperature of the
heater
0,6
0,079
0,4
0,053
Improperly developed
technological process
Improper calibration (causing
e.g. too fast gas flow)
Fig. 5. Weighted Ishikawa diagram for the defect: shape non-homogeneity of the reinforcement phase in the casting
Table 5.
The matrix diagram of the causes leading to the defect ‘size nonhomogeneity of reinforcement phase in the casting
1A
Management
Σn
No proper communication between workers
0,.5
0.25
Too high work pace required
0.25
0.125
Incorrectly prepared technological
0.75
0.375
documentation
Lack of motivation in workers
0.5
0.25
Total
2
≈1
1A
Manpower
Σn
Insufficient qualifications
0.5
0.333
Insufficient technological regime
0.5
0.333
Workers mentally and physically unfit
0.5
0.333
Total
1.5
1
1A
Method
Σn
Improperly developed technological
0.5
0.4
process
Improper methods of technological process
control
Total
Materials
Inadequate properties of the matrix material
Inadequate reinforcement phase
Inadequate wetting angle in the
reinforcement phase-matrix system
Total
Technological stand
Improper calibration (causing e.g. too fast
gas flow)
Too high or too low temperature of the
heater
Improperly selected technological
machinery
Improperly selected technological fittings
Total
ARCHIVES OF FOUNDRY ENGINEERING Volume 11, Issue 2/2011, 23–28
0.75
0.6
1.25
1A
0.75
1
1
Σn
0.333
0.444
0.5
0.222
2.25
1A
≈1
Σn
0.75
0.333
0.5
0.222
0.5
0.222
0.5
2.25
0.222
≈1
27
Too high or too low temperature
of the heater
Improper calibration
(causing e.g. too fast
gas flow)
0,222
0,059
0,333
0,088
Improperly selected
technological fittings
0,222
0,059
Incorrectly prepared
technological documentation
0,375
0,075
Improperly selected
technological machinery
No proper
communication
between workers
0,222
0,059
Technological
stand
Improper methods
of technological
process control
0,25
0,05
0,25
0,05
0,125
0,025
Too high work
pace required
Lack of
motivation in
workers
Improperly developed
technological process
0,6
0,079
Method
Management
0,266
0,266
0,133
0,133
0,2
0,2
0,266
0,266
0,133
0,133
Materials
Inadequate wetting angle
in the reinforcement
phase-matrix system
Inadequate
reinforcement phase
0,444
0,118
0,4
0,053
0,222
0,059
Manpower
Workers mentally
and physically unfit
0,333
0,088
SIZE NON-HOMOGENEITY
OF REINFORCEMENT
PHASE
Inadequate properties
of the matrix material
0,333
0,044
0,333
0,044
0,333
0,044
Insufficient
qualifications
Insufficient technological
regime
Fig. 6. Weighted Ishikawa diagram for the defect: size non-homogeneity of the reinforcement phase in the casting
4.Summary
Each of the weighted Ishikawa diagrams may be analyzed in
detail to obtain quantitative information on the cause of defect
occurrence [12]. For instance, in reference to the causes resulting
from management (Fig. 4) the upper weight equal to 0.25 is the
relative weight and means that the given subcause brings about
28.5% of the effects caused by improper management. However, if
we refer the figure 25 % to the weight of the whole group of cuases
termed management (0.285), the resulting absolute weight of that
subcause equals 0.071 i.e. 7.1%.
The application of the Pareto chart and Ishikawa diagram may
significantly contribute to the description of material and
technological determinants of the quality of metal composite
castings.
wych kompozytów z nasycanym zbrojeniem, Archiwum
Technologii Maszyn i Automatyzacji, 26 [1], 2006, s.77–86.
[6] K. Gawdzińska, Z. Pędzich, J. Grabian, Próba określenia
porowatości zbrojenia metalowych kompozytów nasycanych,
Archiwum Technologii Maszyn i Automatyzacji, 25/1
(2005) s. 15–12.
[7] K.B. Lee, H.S. Sim, S.Y. Cho, H. Kwon, Reaction products
of Al–Mg/B 4 C composite fabricated by pressureless
infiltration technique, Materials Science and Engineering
A302 (2001).
[8] K. Naplocha, K. Granat, Materiały kompozytowe na osnowie
stopu aluminium umacniane kształtkami Al 2 O 3 /Ti/C, Kompozyty (Composites) 10: 1 (2010), 25–29.
[9] A. Olszówka-Myalska, J. Szala, J. Cwajna, Characterization
of reinforcement distribution in Al/(Al 2 O 3 ) p composites,
Proc. of Sixth Intern. Conference – Stereology and Image
Analysis in Materials Science, Kraków 2000, str. 291–300.
[10] A. Hamrol A., W. Mantura, Zarządzanie jakością. Teoria i
praktyka, wyd. trzecie, uaktualnione, PWN, Warszawa 2006.
[11] A. Hamrol, Zarządzanie jakością z przykładami, PWN,
Warszawa 2005.
[12] W. Łybacki, K. Zawadzka, Wspomaganie diagnostyki wad
odlewów narzędziami zarządzania jakością, Archiwum
Technologii Maszyn i Automatyzacji, Vol. 28, nr 1, 2008, s.
89–101.
[13] E. Kindlarski, Kontrola i sterowanie jakością, Oficyna
Wydawnicza Politechniki Warszawskiej, Warszawa 1991.
[14] A. Gwiazda, Koncepcja ważonego wykresu Ishikawy,
Problemy Jakości, kwiecień 2005.
[15] K. Szestak-Zawadzka, Zastosowanie narzędzi zarządzania
jakością do eliminacji wad odlewów, praca dyplomowa,
Politechnika Poznańska 2007 (maszynopis). A. Tabor, J.
Rączka, Nowoczesne zarządzanie jakością Tom IV Systemy
zarządzania jakością w praktyce, Wyd. CSiOSJPK, Kraków
2004.
B
B
B
B
Literature
[1] E. Fraś, A. Janas, A. Kolbus, Odlewany kompozyt aluminiowy in situ umacniany cząstkami borków tytanu,
Kompozyty (Composites) 1, PTMK 1(2001), s. 23–27.
[2] H.L. Han, Z.G. Wang and Sun Lizhi, Effects of
Reinforcements Size on low Cycle Fatigue Behaviour of SiC
Particle Reinforced Aluminium Matrix Composites, Scripte
Metallurgica et Materiale 33(5), 1995.
[3] J. Jackowski, Porowatość odlewów kompozytowych wytwarzanych przez nasycanie zbrojenia metalem, Wydawnictwo
Politechniki Poznańskiej, Rozprawy nr 380, Poznań 2004.
[4] Z. Konopka, M. Cisowska-Łągiewka, A. Zyska, Właściwości
trybologiczne kompozytu AK9-Pb, VI Międzynarodowa
Sesja Naukowa Nowe Technologie i osiągnięcia w metalurgii
i inżynierii materiałowej, Częstochowa 2005, 161–164.
[5] D. Nagolska, P. Szymański, Z. Pędzich, Rola parametrów
struktury kształtki zbrojącej w procesie recyklingu metalo-
28
ARCHIVES OF FOUNDRY ENGINEERING Volume 11, Issue 2/2011, 23–28
B
B
B
B
B
B
B
B