This standard describes the calculation and application of the process capability index for both double-sided and single-sided specification limits. The process capability index is used to indicate the degree to which the process capability meets the specification, so as to analyze and judge the process capability status. This standard is applicable to processes whose main quality characteristics are metrological characteristics that follow a normal distribution. JB/T 3736.7-1994 Commonly used statistical tools in quality management Process capability index JB/T3736.7-1994 Standard download decompression password: www.bzxz.net

Machinery Industry Standard of the People's Republic of China
JB/T 3736.1~-3736.8--94
Statistical tools commonly used in quality management
1994-12-09 Issued
Ministry of Machinery Industry of the People's Republic of China
1995-10-01 Implementation
Mechanical Industry Standard of the People's Republic of China
Statistical tools commonly used in quality management
Process capability index
! Content and scope of application
This standard specifies the calculation and use of process capability index JB/T 3736.7-94
[R 3Y3.X
1. The process capability index is used to express the degree of process capability without standardization, so as to classify and delineate the process capability status. Wood standard is suitable for the main quality of the disk from the general market design of the most characteristic process. 1 symbol
process: intercept value:
sample standard deviation 1
T.: specification upper limit;
T... specification lower limit
T: specification range T=Tu-Ti!
M: specification product center value M=o+
, center shift profit
up; wave shift coefficient
C: double state specification limit, center element shift process: capability index:! The main energy index of the worker when the double-sided specification limit is moved: 1-character energy index of the single-line upper limit: CL: The process energy index of the single-line specification limit: 3 calculation formula
3.1 Identify the specification limit on both sides, when the center is not biased, the worker's floating energy index formula is 3.2 Double-sided specification limit, when the center moves (square 1), the worker's capacity index is: -r29
3.1 Single rigid specification limit cancer
3.3.1 Only from the upper limit of the specification, the process capability index calculation formula is: C||t t||3.3.2 When there is a lower limit of the specification, the calculation formula of the production capacity index is: Ministry of Machinery Industry 1994-12-(09 ​​approved
1995-10-012 standard
4. The new criteria for judging the capacity of the work bed
The new criteria for judging the capacity of the work bed are stipulated in Table 1.
The upper capacity makeup sound
Serious lack
5. Application steps
Determine the quality value to be analyzed:
The current measured value of the property set, the number of 30
JB/ 3736. 7 -94
Process whole index
C,tCa,Cru.CL)c,0. 67
0.67sC,(G,Ca.C)
1C,(CCC11. :3
1. 33,(CC,C.31. 7
C,(C,Cu.Cu.>1. 0?
Judge whether the process quality is in a stable state. The process capability index can be calculated only when it is in a stable state! Judge whether the observed value is normal: calculate the mean and standard
Calculate the process capability index, judge the process capability status: check Table 2, Table 3 or Table, estimate the total qualified product rate. Table 2C. The corresponding total forest unqualified product rate table c..5
C 0598
U,0002
E6, BF
J11/3736.7-94
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Cu,C, 2G-12
-3- 341
, fon!
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6Using example
JB/T 3736.7—94
The basic dimension requirement of the base part is 1C28. According to the measurement, the dimension of the 48-point part is as shown in Table 5. Table 5
10 c50
1C C4S
After judging that the process pressure is out of the stable state, the above capability index can be calculated, and the value of the test is from the positive population. According to the method of TB/T3736.4, the normal probability paper is used for judgment. The data table of the standard test is sorted and listed into a format (see Table 2 of JB/TA736.4), and the points are set on the normal probability paper. The normal distribution is shown in Figure 2 of JB/T3736. It can be inferred that the quality characteristic value obeys the normal distribution. Therefore, the following steps can be performed,
d, the single weekly value three standard waste 5, the white normal probability paper can be estimated: yuan = 10.0499
calculate the process capability index.
Because the mean is in the center of the tolerance zone: there is no bias, so
6 x0.0018
f. The process energy is divided into zone C, and the value is less than 1. Check table 3. The overall defective rate is U.4%. If the process is slightly insufficient, it should be modified appropriately (small deviation) to improve the ability of the factory and ensure that the product quality can be most stable and meet the requirements of the specifications. The example of the preparation of the "process strength analysis disk" with comprehensive diagrams and tables is shown in Table 5.45
Completion date
3 Customer
（) Long term () Short term
5 Product standard/hour
8 Characteristics
? Inspection/test method
11 Specifications must be changed
12 Sufficient force
, 9 yuan
Measured value 2
Number of accumulation periods
Increment rate
Nominal size three
JB/T 3736.7—94
Table 6 Workshop capacity analysis
2 Piece scale
6 Measurement unit
Category Safety item
Lower limit-
—3a=
1 Select the basics
Close the slow work
Important item
10 Applicable period
Upper sheet=
19.04510.04710.04910.05110.05310.05513.046
19.05215,65
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Attached explanation:
1B/T3736. 7—94
This standard is issued by the Ministry of Industry and Machinery Standardization Research Institute, and is supported by the First Machine Tool Factory of Beijing, the Ministry of Industry and Machinery Standardization Research Institute, Shenyang No. 3 Machine Tool Factory, and Shenyang Hu Type Machine Factory.
The main drafters of the standard are Zhang Baosheng, I Xie Zhang, Guan Yuejing, Xiao Zongxiang, Fu Ya, 47
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