NBR 5429

The inspection of productions and entries that use the inspection procedures by sampling plans, referencing the norm NBR 5429 by means of an unknown variability, that follow a specific system treatment.

How to use NBR 5429?

The usage of the NBR 5429 is simple. Procedures used for the adoption of plans type NBR 5426, Internal, Zero Defect are valid also for the NBR 5429.

The following procedures show a method of using plans type NBR 5429 for Process Inspection modules (QIP) and Entry Inspection (QIE):

On the Product Specification Register - QIP and Product Specification - QIE

1. To define the NBR 5429 Sampling Plan to confirm the inclusion of Product Specification, will be shown on the screen to be entered usage operation scrips on the specification. Next, link tests to each operation through the folder specifications.
2. In case of data that make reference to the test, to have the sampling plan associated to the test, complete the field:
3. Sampl. Pl. with the letter B, that indicates the usage of the NBR 5429.
3. After the selection of the plan, a window will be shown to enter the fields:
4. Sampling (Inspection Type);
5. Sampling Level (Plan Inspection Level);
6. NQA (Acceptable Quality Level).
4. By means of the query [F3], will be shown data to be used on the NBR 5429. In case of tests for Plan association, the following procedures should be repeated.
5. After the confirmation, the plans will be defined for Product x Revision, Test (on QIP) and Supplier x Product x Text (on QIE), where on the following Production Orders to be inspected, will be analyzed the sampling plans defined on the specifications.

On the routine Results - QIE

6. The analysis of the Sampling Plan that uses the NBR 5429 is done by the Results routine after collection measures and definition of the Lab Report. A particularity on the analysis applied by the NBR 5429 is that the rejection is not defined by means of non-conformity counting, such as on NBR 5426, but on the estimation of defective percentage, based on the collected measurements.
7. Entered the measurements, select the folder Labs inResults, referent to operations associated to the Lab, next the analysis NBR 5429 will be applied automatically.

How is it calculated?

There is the following product:

Code

001

Revision

01

Description

Blue Pen

 

With the following specification:

Nominal value

10 mm

LIE

 5 mm

LSE

 8 mm

 

Therefore:

LIC

15 mm

LSC

18 mm

 

Where the following Sampling Plan should be defined for the Test: 001

Norm

NBR 5429

Level

II (two)

NQA

2.5

Inspection Plan

Unknown variability - Normal

 

Data make reference to material production to be inspected:

Supplier

F001

Product

001

Batch Size

580 units

 

On the production order analysis, inspected in Results, there is the following application history for the Sampling Plan:

Sample

40

Acceptance

0

Rejection

6.81

 

Collected measurement values:

1st.

15 mm

2nd.

16 mm

3rd.

17 mm

4th.

15 mm

5th.

18 mm

 

With these information, the calculation will be made through the System as such:

1. Obtain average measurements:

d63c712b-4779-4dbc-acc9-11a0b6f47727

Where:

n = number of measurements

Xn = measurement value

1c12756b-d6bf-4d64-99b5-708d19cba908

2. Obtain Standard Deviation, where:

337703d8-7b07-4364-982b-ccddd9e3dc5d

3. Obtain Qi, where:

0dfb9659-2a56-4c80-98e3-47996af5a589

4. Obtain Qs, where:

d704e258-ce82-4359-a9e8-d416f0cbb853

5. After the definition of Qi and Qs will be found Pi and Ps, by means of inquiring the table for estimating defective percentage on the lot (EPD), the search is made as follows:
• Sample size = 40, and, respectively, values of Qi = 0.92 and Qs = 1.38.
• With these data it is possible to find values for Pi and Ps:

Qi

Sample

found

Pi

0.92

40

17.90

 

Qi

Sample

found

Ps

1.38

40

8.27

 

• Considerations on the calculation of Pi and Ps:
• If Qs > 3,89, Ps = 0 (zero)
• If Qs < 3,89, Ps = 100
• If -3,89 ≤ Qs < 0, Ps will be the module value found
• If Qi > 3,89, Pi = 0 (zero)
• If Qi < 3,89, Pi = 100
• If -3,89 ≤ Qs < 0, Pi will be the module value found
• The analysis of the result will be done as follows:

Qi

+

Qs

=

R

17.90

8.27

26.17

 

• The result found will be compared to the rejection will be defined on the table:

Result

>

Rejection

26.17

6.81

 

• Therefore, the report should be rejected, because the percentage of defects is greater than the specifications on tables 27 to 34 of the NBR 5429.
• The procedure for the analysis of the following sampling plans remain unchanged: in case of renewal of any of the lab test, by normal inspection or by sampling plans, the rejection rule for this report remains the same.