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

Quality characteristic

Measurement characteristic

Counting characteristic

Classification of quality characteristic

Measurement characteristic

the nominal the better

the smaller the better

the larger the better

m 2

1m

or

0x

x

Methods to Determine the Parameters

Parameter designQuality function deploymentReliability 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(HO

Q)

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 functionSafety coefficient

Quality loss function

The quality loss function of the nominal the better characteristic:

The quality loss function of the smaller the better characteristic:

The quality loss function of the larger the better characteristic:

2( ) ( )L y K y m

2( )L y Ky

2

1( )L y k

y

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.

Thus:

So, loss coefficient:

20 0A K

020

Ak

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:

00

A

A

Example

The target value of the output voltage of the television power circuit is 115V, the functional limit , the loss of losing functionality yuan.

A 、 Determine the loss coefficient of the loss function;

25o V

300oA

02 20

3000.48

25

Ak

• B 、 If the rework cost of the unqualified product A=1 yuan, the specification limit of the quality characteristic can be determined.

• Thus, the technical parameter and specification limit of the output voltage of the television power circuit:

00

125 1.4

300

AV

A

115 1.4V

Quality loss model of the smaller the better characteristic

20 0A K

020

Ak

00

A

A

Quality loss model of the larger the better characteristic

20 0K A

2

1( )L y k

y

00

A

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:

Generally, safety coefficient .

0A

A

4 ~ 5

the nominal the better

The relationship between the specification limit and the functional limit △ △0 of the nominal the better characteristic:

Then, the specification limit :

00

A

A

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