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 Size of defect (Length in inches) Penalty points 0 - 3 1 3 - 6 2 6 - 9 3 9 and above 4  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 2 nd 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)

12. Acceptable Quality Levels for Normal Inspection (% defective) Lot Size/ Sample Size.01.015.025.04.065.10.15.25.40.651.01.52.54.0 Lot Acceptance (Ac) Number (maximum number of rejects to accept the lot) LS=2 to 8 SS=2 00000000000000 LS=9 to 15 SS=3 00000000000000 LS=16 to 25 SS=5 00000000000000 LS=26 to 50 SS=8 00000000000011 LS=51 to 90 SS=13 00000000000011 91 to 150 SS=20 00000000000012

13. 151 to 280 SS=32 00000000000123 281 to 500 SS=50 00000000001234 501 to 1200 SS=80 00000000012357 1201 to 3.2K SS=125 000000001235710 3201 to 10K SS=200 0000001123571014 10001-35K SS=315 00000012357101421 35001-150K SS=500 0001112357101421- 150001-500K SS=800 000112357101421 -.01.015.025.04.065.10.15.25.40.651.01.52.54.0