1 ANSI/ASQ Z1.4 Acceptance Sampling Plans Devised in 1942 at Bell LabsLater became MIL-STD-105EISO-2859ANSI/ASQ Z1.4 (The American National Standard Institute and American Society for Quality Control Z1.4)Wording & terminology changesAdditional tables added1
2 ANSI/ASQ Z1.4Intended to be used for a continuing series of lots, but may be designed for isolated lots.Standard provides for single, double, and multiple sampling plans.ANSI/ASQ Z1.4 is also provided for normal, tightened, or reduced inspection.Plan is specified by the AQL, and sample-size code.2
3 ANSI/ASQ Z1.4Normal inspection is used at the start of inspection with changes being a function of recent quality history. (แผนนี้ใช้เมื่อเริ่มทำการสุ่มตรวจล็อต และสามารถเปลี่ยนการตรวจเป็นแบบแผนผ่อนปรน (Reduced inspection) หรือเข้มงวด(Tightened inspection) ซึ่งขึ้นอยู่ประวัติของคุณภาพของสินค้าที่ทำการตรวจ)Tightened inspection:Generally used when producer’s recent quality history has deteriorated. (ใช้เมื่อประวัติของคุณภาพของสินค้าแย่มาก)Reduced inspection:Used when the producer’s recent quality history has been exceptionally good.3
7 ExampleFor a lot size of 2000, an AQL of 0.65%, and an inspection level of III, determine the single sampling plans for normal, tightened, and reduced inspection.
8 ANSI/ASQ Z1.4 Normal, Tightened, and Reduced Inspection Start with normal inspectionSwitching ProceduresNormal to tightenedInstitute when 2 out of 5 consecutive lots not accepted on original inspectionTightened to normalInstitute when 5 consecutive lots acceptedIf not, then discontinue inspection under this plan24
9 ANSI/ASQ Z1.4 Switching Procedures Normal to reduced Institute when: (all of the following)Preceding 10 lots on normal inspection have been acceptedTotal nonconforming in preceding 10 samples is less than number identified in Table 10-5.Production is at a steady rateReduced inspection is considered desirable by responsible authority25
10 ANSI/ASQ Z1.4 Switching Procedures Reduced to normal Institute when: (any of the following)A lot is not acceptedSampling procedure terminates with neither acceptance or rejection criteria have been metProduction is irregular or delayedOther conditions26
Your consent to our cookies if you continue to use this website.