Random Sampling Service

Many magnet users, especially the small and middle sized companies, do not have the capability and resources to manage and test the quality of their products efficiently due to the large geographical distance. W-testing provides an on-site inspection service before shipment, in order to add an another security for the purchasing process.

Random sampling service provides:  

  • customized solution for random sampling

  • representation of client and on-site execution of random sampling

  • Sending to client specified institute

Especially to confirm whether the quality of the products fully fulfills the specification as regulated in the sales contract, can help the clients to prevent many unnecessary risks and disputes.

Sampling Process

What is sampling process? In industry there are two standards for quality inspection being used nowadays: 

W-testing provides single sampling process in accordance with DIN ISO 2859. Other process shall be designed by request:

  • Double sampling process in accordance with DIN ISO 2859-1

  • Single/Double sampling process in accordance with DIN ISO 3951

  • customized sampling process

DIN ISO 2859-1 Single Sampling Inspection Process

With customer confirmed acceptance quality limit - AQL, inspection level and lot size the followings will be calculated:

Three party sampling agreement regulates:

W-testing coordinates and conducts sampling process in accordance with agreement, and issues/arranges:

  • Sample size

  • Acceptance number

  • Time, Location

  • Standard, process, contract institute

  • Acceptance/rejection conditions

  • Documentation of sampling processes

  • Report of Inspection (depending on contract institution)

  • Suggestion of acceptance/rejection

Comparison of Sampling Plans

By changing the parameter of different plan, customer can reduce the cost in a acceptable range. For example:

  • Plan A: if process average is better than AQL, customer can switch to a reduced inspection level (I), in oder to reduce the sample size.

  • Plan B: if there is no process average available, generally the normal inspection level (II) shall be used. However once process average is found lower than the AQL after several inspection, a tighter inspection level shall be chosen.

  • Plan C: a suitable AQL can help both sides reduce the cost and rejection possibility.

Plan A

Plan B

Plan C

AQL

0.4%

AQL

0.4%

AQL

 0,65%

Lot size N

 10001-35000 pc

Lot size N

10001-35000 pc

Lot size N

10001-35000 pc

Inspection level

I

Inspection level

II

Inspection level

II 

Sample size n

125 pc

Sample size n

315

sample size n

315

Acceptance number; Rejection number

1 pc ; 2 pc

Acceptance number; Rejection number

3 pc ; 4 pc 

Acceptance number; Rejection number

5 pc ; 6 pc