1. 4/24/2015IENG 486 Statistical Quality & Process Control 1 IENG 486 - Lecture 19 Introduction to Mil Std 105E

2. 4/24/2015 IENG 486 Statistical Quality & Process Control2 Assignment  Reading: Chapter 15 Sections 15.1 – 15.2.4: pp. 632 - 646 Sections 15.4 – 15.4.3: pp. 655 – 663  Homework: Download and complete Last Assign: Acceptance Sampling Requires MS Word for Nomograph Requires MS Excel for AOQ pp.

3. 4/24/2015 IENG 486 Statistical Quality & Process Control3 Military Standard 105E (MIL STD 105E) (ANSI/ASQC Z1.4, ISO 2859)  Most widely used acceptance sampling system for attributes  MIL STD 105E is Acceptance Sampling System collection of sampling schemes  Can be used with single, double or multiple sampling plans We will consider single sampling plans for this course

4. 4/24/2015 IENG 486 Statistical Quality & Process Control4 Inspection Types  Normal Inspection Used at start of inspection activity  Tightened Inspection Instituted when vendor’s recent quality history has deteriorated Acceptance requirements for lots are more stringent  Reduced Inspection Instituted when vendor’s recent quality history has been exceptionally good Sample size is usually smaller than under normal inspection

5. 4/24/2015 IENG 486 Statistical Quality & Process Control5 Switching Rules

6. 4/24/2015 IENG 486 Statistical Quality & Process Control6 Procedure for MIL STD 105E  STEP 1: Choose AQL MIL STD 105E designed around Acceptable Quality Level, AQL Recall that the Acceptable Quality Level, AQL, is producer's largest acceptable fraction defective in process Typical AQL range: 0.01%  AQL  10% Specified by contract or authority responsible for sampling

7. 4/24/2015 IENG 486 Statistical Quality & Process Control7  STEP 2: Choose inspection level Level II Designated as normal Level I Requires about one-half the amount of inspection as Level II Use when less discrimination needed Level III Requires about twice as much inspection as Level II Use when more discrimination needed S-1, S-2, S-3, S-4 Four special inspection levels used if very small samples necessary Procedure for MIL STD 105E

8. 4/24/2015 IENG 486 Statistical Quality & Process Control8  STEP 3–Determine lot size, N Lot size most likely dictated by vendor  STEP 4: Find sample size code letter From Table 15-4, p 657 Given lot size, N, and Inspection Level, use table to determine sample size code letters  STEP 5: Determine appropriate type sampling plan Decide if Single, Double or Multiple sampling plan is to be used Procedure for MIL STD 105E

9. 4/24/2015 IENG 486 Statistical Quality & Process Control9  STEP 6: Find Sample Size, n, and Acceptance Level, c Given sample size letter code, use Master Tables: 15-5, 15-6, and 15-7 on pp.658-660 Find n and c for all three inspection types: Normal Inspection Tightened Inspection Reduced Inspection Procedure for MIL STD 105E

10. 4/24/2015 IENG 486 Statistical Quality & Process Control10 Example  Suppose product comes from vendor in lots of size 2000 units. The acceptable quality level is 0.65%. Determine the MIL STD 105E acceptance-sampling system.

11. 4/24/2015 IENG 486 Statistical Quality & Process Control11 Normal Insp. Level Lot Size = 2000

12. 4/24/2015 IENG 486 Statistical Quality & Process Control12 AQL Plan K Sample 125 units. Ac = 2, accept if defects ≤ 2. Re = 3, reject entire lot if defects ≥ 3.

13. 4/24/2015 IENG 486 Statistical Quality & Process Control13 AQL Plan K Sample 125 units Ac = 1, accept if defects ≤ 1. Re = 2, reject entire lot if defects ≥ 2.

14. 4/24/2015 IENG 486 Statistical Quality & Process Control14 AQL Plan K Sample 50 units Ac = 1, accept if defects ≤ 1. Re = 3, reject entire lot if defects ≥ 3.

15. 4/24/2015 IENG 486 Statistical Quality & Process Control15 Questions & Issues