AlfaQC is an independent company with more than 20 years of expertise and presence with Taiwan manufacturing industry that follows a certain set of ethics.

Our key commitments are:

  1. Integrity
  2. Confidentiality of our clients
  3. Compliance with international standards

ISO 2859-2:2020

We use the ISO 2859-2:2020 set of standards to conduct our inspections.

It is a very flexible method also called AQL (Acceptable Quality Limit), which determines two important elements:

  1. How many samples should be picked and inspected, among a batch of product or parts?
  2. Where is the limit between acceptability and refusal, when it comes to defective products?

Defect Types

In practice, we have 3 types and are often distinguished as:

  • 0% for critical defects
    • totally unacceptable: a user might get harmed, or regulations are not respected
  • 2.5% for major defects
    • these products would usually not be considered acceptable by the end user
  • 4.0% for minor defects
    • which do not limit the use of the product, but make it sub-standard and could affect sales

Understanding

Before using the AQL tables, you should know three parameters:

  1. The ‘lot size’
  2. The inspection level
  3. The AQL limits

There are basically two tables.

  • The first table tells you which ‘code letter’ to use,
  • The second table with the ‘code letter’ from above will give you the sample size and the maximum numbers of defects that can be accepted.

Table 1 – Code Letters – ANSI/ASQ Standard Z1.4 – 2008

How to read this table?

General Inspection Levels Special Inspection Levels
Lot Size I II III S1 S2 S3 S4
2 to 8 A A B A A A A
9 to 15 A B C A A A A
16 to 25 B C D A A B B
26 to 50 C D E A B B C
51 to 90 C E F B B C C
91 to 150 D F G B B C D
151 to 280 E G H B C D E
281 to 500 F H J B C D E
501 to 1’200 G J K C C E F
1’201 to 3’200 H K L C D E G
3’201 to 10’000 J L M C D F G
10’001 to 35’000 K M N C D F H
35’001 to 150’000 L N P D E G J
150’000 to 500’000 M P Q D E G J
500’001 and over N Q R D E H K

For example, let’s say there is a production of 5’000 sets of kitchenware to be controlled with a Level II.

We selected the 11th line of the Lot Size: 3’201 to 10’000

The second column on the levels (Level II) show the letter: L

For that lot with a quantity of 5’000 pieces on Level II, the Code Letter to use in the next table is ‘L’

Table 2 – Sampling Acceptance Limits

How to read this table?

SINGLE SAMPLING PLANS FOR NORMAL INSPECTION
Sample size
Code Letter		 Sample size Acceptable Quality Levels
0.065 0.10 0.15 0.25 0.40 0.65 1.0 1.5 2.5 4.0 6.5
Ac Re Ac Re Ac Re Ac Re Ac Re Ac Re Ac Re Ac Re Ac Re Ac Re Ac Re
A 2 | | | | | | | | | ↓ 0 1
B 3 | | | | | | | | ↓ 0 1 ↑
C 5 | | | | | | | ↓ 0 1 ↑ ↓
D 8 | | | | | | ↓ 0 1 ↑ ↓ 1 2
E 13 | | | | | ↓ 0 1 ↑ ↓ 1 2 2 3
F 20 | | | | ↓ 0 1 ↑ ↓ 1 2 2 3 3 4
G 32 | | | ↓ 0 1 ↑ ↓ 1 2 2 3 3 4 5 6
H 50 | | ↓ 0 1 ↑ ↓ 1 2 2 3 3 4 5 6 7 8
J 80 | ↓ 0 1 ↑ ↓ 1 2 2 3 3 4 5 6 7 8 10 11
K 125 ↓ 0 1 ↑ ↓ 1 2 2 3 3 4 5 6 7 8 10 11 14 15
L 200 0 1 ↑ ↓ 1 2 2 3 3 4 5 6 7 8 10 11 14 15 21 22
M 315 ↑ ↓ 1 2 2 3 3 4 5 6 7 8 10 11 14 15 21 22 ↑
N 500 ↓ 1 2 2 3 3 4 5 6 7 8 10 11 14 15 21 22 ↑ |
P 800 1 2 2 3 3 4 5 6 7 8 10 11 14 15 21 22 ↑ | |
Q 1’250 2 3 3 4 5 6 7 8 10 11 14 15 21 22 ↑ | | |
R 2’000 3 4 5 6 7 8 10 11 14 15 21 22 ↑ | | | |

Ac stand for Accepted

Re stand for Refused

In the previous example on Table 1 the code letter for a Level II for 5’000 pieces production was ‘L’.

  • So we will have to draw 200 pcs randomly from the total lot size of 5’000,
  • We set your AQL at
    • 2.5% for major defects and
    • 4.0% for minor defects

In our example the products are accepted if

  • NO MORE than 10 products with major defects
  • AND NO MORE than 14 products with minor defects are found.

If we find 15 products with major defects and 12 products with minor defects, the production of the 5’000 products is refused.

If you find 3 with major defects and 7 with minor defects, the production is accepted.