The Common Methods to
Determine the Parameters of
Technical Standards
Zhang Yue-yi
China Ji Liang University
Content
 Introduction
 Classification of quality characteristic
 Methods to determine the technical parameters
 Methods to determine the specification limits
 Conclusion
Introduction
There are always some technical
parameters and specification limits
in the technical standards.
The technical parameters and
specification limits of each
characteristic are all different.
Classification of quality characteristic
Measurement
characteristic
Quality
characteristic
Counting
characteristic
Classification of quality characteristic
the nominal the better
m
Measurement
characteristic
or
2
1
m
the smaller the better
x  0
the larger the better
x 
Methods to Determine the Parameters
Parameter design
Quality function deployment
Reliability design
Parameter design
 Parameter design is the chief component of the
Taguchi’s three stage design.
 The basic idea of the parameter design is to determine
the optimal level of all technical parameters by using
the orthogonal array and S/N ratio, including raw
materials, electronic parts and components.
 Meanwhile, in order to minimize the quality
fluctuation, we must decrease the influence of all
kinds of interference by the parameter design.
Quality function deployment
Quality function deployment(QFD) is
the method of product design and
development driven by customer, it
adopts certain method to accurately
transform the customer demands into
the technical and process parameters.
The house of quality(HOQ)
Reliability design
Reliability is the ability of the product
or system to perform and maintain its
functions in routine circumstances, as
well as hostile or unexpected
circumstances.
Reliability design is to solve product
reliability at the design stage.
Methods to Determine the specification limit
Quality loss function
Safety coefficient
Quality loss function
The quality loss function of the nominal the
better characteristic: L( y)  K ( y  m)2
The quality loss function of the smaller the
better characteristic: L( y)  Ky 2
The quality loss function of the larger the
better characteristic: L( y )  k 1
y2
Quality loss model of the nominal
the better characteristic
A
0
Method to determine the loss
coefficient k
When the product becomes out of
use, that is to say, the quality
characteristic value is beyond the
functional limit, the loss is A0 yuan.
2
Thus:
A  K
0
0
So, loss coefficient:
A0
k 2
0
Method to determine △
If the product is unqualified, the
rework cost of the product is A
yuan, the specification limit of the
quality characteristic is:

A
 0
A0
Example
The target value of the output voltage of
the television power circuit is 115V, the
functional limit o  25V , the loss of losing
functionality Ao  300 yuan.
A、Determine the loss coefficient of the
loss function;
A0 300
k  2  2  0.48
0 25
• B、If the rework cost of the unqualified
product A=1 yuan, the specification limit of
the quality characteristic can be determined.

A
1
 0 
 25  1.4V
A0
300
• Thus, the technical parameter and specification
limit of the output voltage of the television
power circuit:
115  1.4V
Quality loss model of the smaller
the better characteristic
A0  K 
2
0
A0
k 2
0

A
 0
A0
Quality loss model of the larger the
better characteristic
1
L( y )  k 2
y
K  A0  02

A0
 0
A
Safety coefficient
A: the loss of the unqualified product;
A0: the loss of the product that the
characteristic value is beyond the
functional limit.
Safety coefficient:

A0
A
Generally, safety coefficient
  4 ~ 5.
the nominal the better
The relationship between the specification
limit △ and the functional limit △0 of the
nominal the better characteristic:

A
 0
A0
Then, the specification limit :  
0

Conclusion
As the customer demand is becoming
higher and higher, not only for product
performance, but also for security,
economy, reliability, appearance quality,
service, etc.
The technical parameter and specification
limit of every characteristic need to be
determined by certain methods.
Thank you!
zyysh@163.com