ASQ-S1-1996.pdf
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1、 K Q C SL 96 E 0759506 0003846 4T9 E ANSVASQC SI -1 996 AMERICAN NATIONAL STANDARD An Attribute Skip-Lot Sampling Program AMERICAN SOCIETY FOR QUALITY CONTROL 611 EAST WISCONSIN AVENUE MI LWAU KEE, WISCONSIN 53202 Copyright American Society for Quality Provided by IHS under license with ASQ Licensee
2、=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 04/18/2007 11:01:15 MDTNo reproduction or networking permitted without license from IHS -,-,- ASQC S1 9b = 0757506 0001847 335 ANSVASQC S1-1996 AMERICAN NATIONAL STANDARD An Attribute Skip-Lot Sampling Program Reaffirmation of ANSUASQC SI-
3、19871 Prepared by American Society for Quality Control Standards Committee for American National Standards Committee Z- I on Quality Assurance An American National Standard Approved on January II, 1996 An Attribue SipLot Sampling Program provides procedures for reducing the inspection effort on prod
4、ucts that satisfy supplier and production qualification criteria. The standard is to be used oniy with ANSi/ASQC 21.4-1993. American National Stun b. Components and r a w materiais; c. seMces; d . Materiaisinprocess; 1.1 Scope The purpose of this publication is to provide procedures2 for reducing th
5、e inspection effort on products submitted by those suppliers who have f. Data0rrecords;and g. Adminishative procedures. These procedures are intended only for a continuing series of lots or batches and sha not be used for isolated lots. AU lots i n the Senes are expected to be of a similar quaiity a
6、nd there should be reason to believe that the lots not inspected are of the same quality as the ones inspected. 1.2 Field of Application 21.4. Its hat 10 consec- utive lots are accepted with a total sample size equal to 1400 units; and that a t o t a l of four nonconforming units are found in the 10
7、 lots, Suppose the l a s t two lots each have a sample size equal to 125 units with one nonconforming unit in each sample. The requirements of Table I are met because the minimum cumulative sample size in Table I for four nonconfomities and AQL of 0.65 is 1306 u n i t s . The requkments in Table II
8、are met for each of the last two lots because the acceptance number for a sample size of 125 units is one nonconformance. Hence, the product qualifies for skip-lot inspection. 5.0 SKIP-LOT PROCEDURES A product which meets the qualification requirements of Sections 4.1 and 4.2 sha be eligible for ski
9、p-lot inspec- tion. nie structure of the skip-lot procedures is outlined in Figure 1. Ihere are t h r e e basic states: 1. State 1: Lot-by-lot inspection; 2. State 2 Skip-lot inspection; and 3. state 3: skip-lot interrupt. The inspection program for product starts in State 1, lot- by-lot inspection.
10、 When the suppiier and product quafy for skiplot inspection (see Section 4.1 and 4.2), the pro- gram switches to S t a t e 2. Skiplot inspection may be tem- poraiily interrupted (see Section 5.5) resulting in a transfer to State 3. In State 3, the product may requalify under less stringent procedure
11、s with a resultant transfer of the pro- gram back to State 2 (see Section 5.6). Alternately, the product may be disqualified for skip-lot inspection while the program is either in State 2or State 3. In this case, the pmgm switches to State 1 and the product must again satisfy the complete requiremen
12、ts of Sections 4.1 and 42. 5.1 Determining the Initial Skip-Lot Inspection Frequency Figure 2 is asummaty of the algorithm used todetermine the i n i t i a l inspection -equency. Data fbm the last 10 or more l o t s shall be used to determine t h i s quency. These data co11sist of a running record o
13、f the number of units inspected and the number of nomnformities found in each sample. More han 10 lots may be needed to meet the requimnents specified in the next pmagraphs because the sample sizes are not large enough to satis the t a b u l a t e d values in Table I. Authorized i n i t i a l inspec
14、tion frequencies are: a) 1 lot inspected in 2 submitted b) 1 lot inspected in 3 submitted c) 1 lot inspected in 4 submitted If m m than 20 lots are needed to qualify, a fr-equency of 1 in2shallbeused. If 20 o r fewer lots are needed to qualify, and each lot satis- f i e s the requirements of Table I
15、I, an i n i t i a l fkequency of 1 in4shallbeused. * O p t i d Annex A, Item 4. lo Multiple sampling is allowed during the qualification period (State 1). More than 10 lots will be needed when the cumdative sample size requirements o f Table I have not been met i n 10 lois. 3 Copyright American Soci
16、ety for Quality Provided by IHS under license with ASQ Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 04/18/2007 11:01:15 MDTNo reproduction or networking permitted without license from IHS -,-,- ASQC S1 96 W 0757506 0001855 401 ANSYASQC S1-19% If u) or fewer lots are needed to
17、 qualify, but one or more lots did not meet the requirements of Table II, an i n i t i a l fre quency of 1 in 3 s W be used. The responsible authority must approve the i n i t i a i inspec- tion frequency. 5.2 Examples of Initial Frequency Determination Continue the example from Section 4.3, and con
18、sider three scenarios. In scenario (a), assume that the product quaiies in the rst 10 lots and that the lot size are 1250 to 9500. Sample sizes for these lots are either 125 or 200 and the number of non- conformances in each sample is aiways 1 o r less. Thus, h m Table II for an AQL of 0.65, ail 10
19、lots meet the require- ments of t h a t table. Hence, the i n i t i a i frcluency is 1 in 4. In scenario ), assume that the fst lot sample of 125 con- t a i n s two nonconformances. Hence the Table II criterion for the lot is not met. Also assume that the product quaii- fies in the first 10 lots. Th
20、en, the i n i t i a i frequency is 1 in 3. i n scenario (c), assume that lots 3 and 11 are rejected, but the product qualifies at lot 21. In this case the initiai f m quency is 1 in 2 because more than u) lots are needed for qualification. 5.3 Reducing the Frequency of Inspection The auhorized frequ
21、encies are: 1. 1 lot inspected in 2 submitted, 2. 1 lot inspected in 3 submitted, 3. 1 lot inspected in 4 submitted, and 4. 1 lot inspected in 5 submitted. The frequency 1 lot in 5 is not available as an i n i t i a l h- quency. The frequency of inspection may be shifted to the next lower frequency
22、of ulqiecton (e.g., om 1 lot in 3 to 1 lotin4) i f all o f the following conditioI1s are met: (1) since the l a s t fre- quency shift, data h m the last 10 or more ccmsecutive lots inspectedandaccepteddirringthecurrentSMte2(lotin- spection) equals or exceeds the quiements in Table I, and (2) the sam
23、ple results o f each o f the l a s t t w o lots inspected meet the nonconformance limits of Table II. The responsible m or nonexistent for purposes Of the procedures in E. The responsible authority desires t o r e m t o lot-by-lot However, if a lot is inspected by the inspection agency, rejected, an
24、d later accepted as nonconfoming by the responsible authority, the inspection resuits shaU be used. inspection (for example, a customer complaint is received, vadakd, and determined to have a serious effect on the quality of the product or service; or the 55 Interrupt Procedures procedm shift betwee
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