AS 1199.1 pdf download – Sampling procedures for inspection by attributes Part 1: Sampling schemes indexed by acceptance quality limit (AQL) for lot-by-lot inspection
5 Acceptance quality limit (AQL)
5.1 Use and application The AQL, together with the sample size code letter (see 10.2), is used for indexing the sampling plans and schemes provided in this part of ISO 2859. When a specific value of the AQL is designated for a certain nonconformity or group of nonconformities, it indicates that the sampling scheme will accept the great majority of the lots submitted, provided the quality level (percent nonconforming or nonconformities per 100 items) in these lots is no greater than the designated value of AQL. The sampling plans provided are so arranged that the probability of acceptance at the designated AQL value depends upon the sample size for a given AQL, being generally higher for large samples than for small ones. The AQL is a parameter of the sampling scheme and should not be confused with the process average that describes the operating level of the manufacturing process. It is expected that the process average will be better than the AQL to avoid excessive rejections under this system. CAUTION: The designation of an AQL shall not imply that the supplier has the right knowingly to supply any nonconforming item.
5.2 Specifying AQLs The AQL to be used shall be designated in the contract or by (or in accordance with the prescription laid down by) the responsible authority. Different AQLs may be designated for groups of nonconformities considered collectively or for individual nonconformities as defined in 3.1.5. The classification into groups should be appropriate to the quality requirements of the specific situation. An AQL for a group of nonconformities may be designated in addition to AQLs for individual nonconformities, or subgroups, within that group. When the quality level is expressed as percent of nonconforming items (3.1.8 and 3.1.9), AQL values shall not exceed 10 % nonconforming. When the quality level is expressed as number of nonconformities per 100 items (3.1.10 and 3.1.11), AQL values up to 1 000 nonconformities per 100 items may be used.
5.3 Preferred AQLs The series of values of AQLs given in the tables are known as the preferred series of AQLs. If, for any product, an AQL is designated other than one of these values, these tables are not applicable.
6 Submission of product for sampling
6.1 Formation of lots The product shall be assembled into identifiable lots, sub-lots, or in such other manner as may be laid down (see 6.2). Each lot shall, as far as is practicable, consist of items of a single type, grade, class, size and composition, manufactured under uniform conditions at essentially the same time.
6.2 Presentation of lots The formation of the lots, the lot size and the manner in which each lot shall be presented and identified by the supplier shall be designated or approved by, or according to, the responsible authority. As necessary, the supplier shall provide adequate and suitable storage space for each lot, equipment needed for proper identification and presentation, and personnel for all handling of product required for drawing of samples.
7 Acceptance and non-acceptance
7.1 Acceptability of lots Acceptability of a lot shall be determined by the use of a sampling plan or plans. The term “non-acceptance” is used in this context for “rejection” when it refers to the result of following the procedure. Forms of the term “reject” are retained when they refer to actions the consumer may take, as in “rejection number.”
7.2 Disposition of non-acceptable lots The responsible authority shall decide how lots that are not accepted will be disposed of. Such lots may be scrapped, sorted (with or without nonconforming items being replaced), reworked, re-evaluated against more specific usability criteria, or held for additional information, etc.
7.3 Nonconforming items If a lot has been accepted, the right is reserved to not accept any item found nonconforming during inspection, whether that item formed part of a sample or not. Items found nonconforming may be reworked or replaced by conforming items, and resubmitted for inspection with the approval of, and in the manner specified by, the responsible authority.
7.4 Classes of nonconformities or nonconforming items Specific assignment of nonconformities or nonconforming items to two or more classes requires using a set of sampling plans. In general, the set of sampling plans have a common sample size, but different acceptance numbers for each class having a different AQL, such as in Tables 2, 3 and 4.