Why do you and your clients need quality insurance services?
Quality control is a key success factor for companies dealing with all suppliers who provide production and services.
Our highly qualified management team and technicians provide the best possible advice when a problem is encountered and we can provide guidance on the most cost-effective quality assurance procedures. Our team understands both the technical standards operating in international markets and the requirements of the marketplace.
1. BST on-site quality inspections and factory audit services throughout China help businesses to reduce risks associated with poor quality, loading, storage, transportation and non-compliance with regulatory requirements, ensure that contractual obligations are met: specifications, packaging, marking and delivery.
2. BST quality inspection hires the inspectors who are responsible, careful, honest and professional to lower your risk of receiving defective goods.
3. Consistent customer-centeredness and flexible operations will win more time and space for you.
4. Reduce your business trip expenses and other miscellaneous expenses resulting from goods inspections carried out by yourself.
What is critical defects, major defects and minor defects?
Defects found in inspection are classified into three categories: critical defects, major defects and minor defects:
1) Critical defects:
Critical defects could result in hazardous or unsafe conditions for individuals using or maintaining the product, as well as defects contravening legal regulations.
2) Major defects:
Major defects may affect the duration of product or reduce the ability to use the item (poor functioning, item incomplete or broken, etc.) or give it a flawed appearance which may affect the product value.
3) Minor defects:
Minor defects are unlikely to reduce the use of the product but nevertheless may influence the visual aspect.
BST uses the MILITARY STANDARD 105E (MIL-STD-105E),tables, which are recognized standards by every industrial company.
This American standard now has equivalents in all national and international standardization organizations (ANSI/ASQC Z1.4, ISO 2859, NF06-022, BS 6001, DIN 40080).
This standard is a proven method to accept or reject a production lot by inspecting a randomly selected number of products.
This method is called 'AQL'(Acceptable Quality Level):
As a quality control company in China, BST uses the Acceptable Quality Level (AQL) to establish a maximum allowable error rate or variation from the standard. Acceptance testing will cease immediately if the failure rate of the product being tested exceeds the minimum Acceptable Quality Level.
NB: It is important to note that Acceptance Sampling cannot provide 100% perfect products. The only way of achieving this is to produce 100% perfect products.
MIL STD 105E table:
Practically, BST Quality Standards use the MIL-STD-105E tables that are summarized below:
SAPLE SIZE COOELETTERS
Lot batch size | Special inspection levels | General inspection | |||||||
S-1 | S-2 | S-3 | S-4 | Ⅰ | Ⅱ | Ⅲ | |||
2 | to | 8 | A | A | A | A | A | A | B |
9 | to | 15 | A | A | A | A | A | B | C |
16 | to | 15 | A | A | B | B | B | C | D |
26 | to | 50 | A | B | B | C | C | D | E |
51 | to | 90 | B | B | C | C | C | E | F |
91 | to | 150 | B | B | C | D | D | F | G |
151 | to | 280 | B | C | D | E | E | G | H |
281 | to | 500 | B | C | D | E | F | H | J |
501 | to | 1200 | C | C | E | F | G | J | K |
1201 | to | 3200 | C | D | E | G | H | K | L |
3201 | to | 10000 | C | D | F | G | J | L | M |
10001 | to | 35000 | C | D | F | H | K | M | N |
35001 | to | 150000 | D | E | G | J | L | N | P |
150001 | to | 500000 | D | E | G | J | M | P | Q |
500001 | and | over | D | E | H | K | N | Q | R |
SINGLE SAMPLING PLANS FOR NORMAL INSPECTION
Sample size code letter | Sample size | |||||||
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 | ||
A B C |
2 3 5 |
0 1 | 0 1 | 0 1 | 0 1 | 0 1 | ||
D E F |
8 13 20 |
0 1 | 1 2 | 1 2 2 3 |
1 2 2 3 3 4 | |||
G H J |
32 50 80 |
0 1 | 1 2 | 1 2 2 3 |
1 2 2 3 3 4 |
2 3 3 4 5 6 |
1 2 2 3 3 4 |
1 2 2 3 3 4 |
K L M |
125 200 315 |
1 2 2 3 3 4 |
2 3 3 4 5 6 |
3 4 5 6 7 8 |
5 6 7 8 10 11 |
7 8 10 15 14 15 |
10 11 14 15 21 22 |
14 15 21 22 |
N P Q |
500 800 1250 |
5 6 7 8 10 11 |
7 8 10 11 14 15 |
10 11 14 15 21 22 |
14 15 21 22 |
21 22 | ||
R | 2000 | 14 15 | 21 22 |
Practically, BST Quality Standards use the MIL-STD-105E tables that are summarized below:
What can I find out from the AQL tables?
Let's take a lot of 2,500 units to inspect, with an AQL of 2.5%.
According to Table B, the sample size is therefore 125 units, and the corresponding acceptance number is 7.
In other words:
If the number of defective units is more than 7, the lot has to be rejected.
If the lot is accepted, it is commonly perceived that there is a maximum of 2.5% of defective units in the lot (with a failure risk percentage of less than 5%).