Product Quality Inspection
By: Erik Martin
Penn Sate University
What will be covered
This presentation deals with the
question of describing and
evaluating product quality
inspection processes.
What is to be discussed


Classification of
characteristics proposed
for describing the effects
of industrial processes.
Formulation of definitions
of the effectiveness and
efficiency coefficients of
quality inspection
processes.

Practical examples of
effectiveness and
efficiency analysis,
using numerical data.
Designating the effects of the
process

Ontological
designations
-describe the effect of
the process in respect
of quantity, quality, or
financial value.

Axiological
-the determination of the
relative worth of the
process results.
Organizational usefulness
 Using some simple mathematical
equations and some data from earlier
productions, one can use those particular
figures to demonstrate the practical
usefulness of the characteristics of the
effectiveness of the quality inspection
process.
How it works
 Taking concepts and data; inspection
processes are very important in many
companies.
Notation for the main characteristics of the
quality inspection process.

Of(0), If(0) - are, respectively, the rejection losses and the
total outlay for the inspection and preventive
actions in the previous calculation period.

OFA, IFA
- are the expected losses and planned outlay in
the present period.

OFP, IFP
- are the actual losses and costs in the present
period.
Selection of the most effective or the most efficient
system of inspection and preventive action.
Designations of
the process
Type of
designation
assessment
effectiveness Efficiency
ontological Ex-ante
EOA= Of(0) - OFA
SOA = OF(O) –OFA/
IFA
ontological Ex-post
EOB= OF(0) - OFP
SOB=OF(O) –OFP/
IFP
axiological Ex-post
EAB = OF(O)-OFP/
OF(O) - OFA
SAB = (SOB)(SOA)
The mathematical model for the optimization of the
effectiveness of a quality inspection process takes
2 forms.
 Minimize the total expected loss OFA
 Maximize the expected efficiency SOA
Examples of 2 quality inspection
processes process A
Number of
the
production
phase
Process
fraction
defective
Actual
inspection
operation
Actual
rejection
probability
Actual outlay
1
.2
None
0
0
2
.2
None
0
0
3
.3
Type 3
8
300
Second example Process B
Number of
the
production
phase
Process
fraction
defective
Actual
inspection
operation
Actual
rejection
probability
Actual outlay
1
0
none
0
0
2
.077
Type 2
.95
166,490
3
.087
Type 2
.932
224,130
4
.073
Type 2
.947
427,200
Actual values of the outlay and the rejection losses
in the previous period were
 Process A : IFP = 300; OFP = 4790
 Process B : IFP = 817,820
OFP= 5,282,180
Results of investigations
Production
process
Expected
Obtained
effectiveness
Efficiency
effectiveness
Efficiency
EOA
SOA
EOB / EAB
SOB / SAB
A
345.6
1.15
170 / .49
.57 / .49
B
25,481,000
31.16
25,528,820 /
1.00
31.22 / 1.00
Conclusion of process A
 The actual system of inspection operations
for the production process A is both
ineffective, since the real effect is half as
high as the expected result, and inefficient,
since the decrease in the rejection losses
is lower than the outlay for the inspection
performance; the real efficiency is half as
high as the expected result.
Conclusion of process B
 The actual organization of the quality
inspection is much better: the real effect is
nearly equal to the expectations (EAB = 1);
the efficiency of quality inspection is both
near to the expected efficiency (SAB = 1) and
also high in absolute numbers (SOB = 31.22,
I.e. one unit of the outlay produces 31 units
of the effect, which means a reduction in
losses.
summary
 Quality inspection is useful
 Quality inspection is effective
 Quality inspection is efficient
 Quality inspection is necessary
references




Hall, M. and Winsten, C., 1965. A dictionary of the Social
Sciences. New York.
Lubicz, M., 1983. On the problem of optimization of a quality
inspection process structure.. Int. J. Prod. Res., 21(3): 369.
Lubicz, M., 1979. Investigations of decision premises for
product quality formation. Ph. Thesis, Techn. Univ.
Wroclaw.
Milward, G.E., 1960. Organization and Methods. MacMillan,
London.