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Understanding Quality Inspection Systems in Industry

This lecture covers four key quality inspection systems used in the industry: the 4-point system, the 10-point system, the Clock-wise garment inspection system, and Acceptance Sampling. The 4-point system assesses fabric defects based on size and significance, while the 10-point system is outdated. Acceptance Sampling, first introduced during WWII, is an efficient method but poses risks of type-I and type-II errors. Key concepts such as Acceptance Quality Level (AQL), Lot Tolerance Percent Defectives (LTPD), and OC Curve are explained along with inspection level classifications.

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Understanding Quality Inspection Systems in Industry

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Presentation Transcript

  1. Lecture 26 Quality inspection systems

  2. Quality Inspection Systems • There are four systems which are used in industry • 4-point system • 10 point system • Clock-wise garment inspection system • Acceptance Sampling

  3. 4-point system • This is a fabric inspection method for different type of faults. This is issued by The American Society for Testing and Materials with reference to the designation:(ASTM D5430-93) • Faults are scored with penalty points of 1, 2, 3 and 4 according to their size and significance.

  4. 4-point system • We can also assess fabric fault/defect rates against other systems as required by the client, for example jersey fabrics are often expressed in meters per fault/defect.

  5. 10-point system • This is an old system and not being used now a days

  6. Clock-wise garment inspection system • See last page (Photocopy is attached)

  7. Acceptance sampling • This a different technique. • This technique was first time used in 2nd world war • This is a time saving technique • But in this technique there is a possibility of type-I error (Producer’s risk) and type-II error (Consumer’s risk)

  8. Acceptance Sampling Plans … • Single sampling plans • Double sampling plans • Multiple sampling plans • Sequential sampling plans • Skip lot sampling plans

  9. Important definitions … • Acceptance quality level (AQL) • Lot tolerance percent defectives (LTPD) • OC Curve (Operating Characteristic) • Average outgoing quality (AOQ)

  10. OC Curve • OC curve means operating characteristic curve • X-Axis : % non-conformity • Y-Axis : Probability of acceptance

  11. Inspection Levels… • Special Inspection Levels • There are 4 levels (S1, S2, S3, S4) • They are used for small sample sizes • General Inspection Levels • There are 3 levels (I, II, III)

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