IENG 486 Lecture 19 Introduction to Mil Std

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IENG 486 - Lecture 19 Introduction to Mil Std 105 E 11/23/2020 IENG 486

IENG 486 - Lecture 19 Introduction to Mil Std 105 E 11/23/2020 IENG 486 Statistical Quality & Process Control 1

Assignment w Reading: n Chapter 15 l l Sections 15. 1 – 15. 2.

Assignment w Reading: n Chapter 15 l l Sections 15. 1 – 15. 2. 4: pp. 632 - 646 Sections 15. 4 – 15. 4. 3: pp. 655 – 663 w Homework: n Download and complete Last Assign: Acceptance Sampling l l 11/23/2020 Requires MS Word for Nomograph Requires MS Excel for AOQ pp. IENG 486 Statistical Quality & Process Control 2

Military Standard 105 E (MIL STD 105 E) (ANSI/ASQC Z 1. 4, ISO 2859)

Military Standard 105 E (MIL STD 105 E) (ANSI/ASQC Z 1. 4, ISO 2859) w Most widely used acceptance sampling system for attributes w MIL STD 105 E is Acceptance Sampling System n collection of sampling schemes w Can be used with single, double or multiple sampling plans n We will consider single sampling plans for this course 11/23/2020 IENG 486 Statistical Quality & Process Control 3

Inspection Types w Normal Inspection n Used at start of inspection activity w Tightened

Inspection Types w Normal Inspection n Used at start of inspection activity w Tightened Inspection n n Instituted when vendor’s recent quality history has deteriorated Acceptance requirements for lots are more stringent w Reduced Inspection n n Instituted when vendor’s recent quality history has been exceptionally good Sample size is usually smaller than under normal inspection 11/23/2020 IENG 486 Statistical Quality & Process Control 4

Switching Rules 11/23/2020 IENG 486 Statistical Quality & Process Control 5

Switching Rules 11/23/2020 IENG 486 Statistical Quality & Process Control 5

Procedure for MIL STD 105 E w STEP 1: Choose AQL n MIL STD

Procedure for MIL STD 105 E w STEP 1: Choose AQL n MIL STD 105 E designed around Acceptable Quality Level, AQL l n Recall that the Acceptable Quality Level, AQL, is producer's largest acceptable fraction defective in process Typical AQL range: l l 11/23/2020 0. 01% AQL 10% Specified by contract or authority responsible for sampling IENG 486 Statistical Quality & Process Control 6

Procedure for MIL STD 105 E w STEP 2: Choose inspection level n Level

Procedure for MIL STD 105 E w STEP 2: Choose inspection level n Level II l n Level I l l n Requires about one-half the amount of inspection as Level II Use when less discrimination needed Level III l l n Designated as normal Requires about twice as much inspection as Level II Use when more discrimination needed S-1, S-2, S-3, S-4 l 11/23/2020 Four special inspection levels used if very small samples necessary IENG 486 Statistical Quality & Process Control 7

Procedure for MIL STD 105 E w STEP 3–Determine lot size, N n Lot

Procedure for MIL STD 105 E w STEP 3–Determine lot size, N n Lot size most likely dictated by vendor w STEP 4: Find sample size code letter n n From Table 15 -4, p 657 Given lot size, N, and Inspection Level, use table to determine sample size code letters w STEP 5: Determine appropriate type sampling plan n Decide if Single, Double or Multiple sampling plan is to be used 11/23/2020 IENG 486 Statistical Quality & Process Control 8

Procedure for MIL STD 105 E w STEP 6: Find Sample Size, n, and

Procedure for MIL STD 105 E w STEP 6: Find Sample Size, n, and Acceptance Level, c n n 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: l l l 11/23/2020 Normal Inspection Tightened Inspection Reduced Inspection IENG 486 Statistical Quality & Process Control 9

Example w Suppose product comes from vendor in lots of size 2000 units. The

Example w Suppose product comes from vendor in lots of size 2000 units. The acceptable quality level is 0. 65%. Determine the MIL STD 105 E acceptance-sampling system. 11/23/2020 IENG 486 Statistical Quality & Process Control 10

Normal Insp. Level Lot Size = 2000 11/23/2020 IENG 486 Statistical Quality & Process

Normal Insp. Level Lot Size = 2000 11/23/2020 IENG 486 Statistical Quality & Process Control 11

AQL Plan K Sample 125 units. Ac = 2, accept if defects ≤ 2.

AQL Plan K Sample 125 units. Ac = 2, accept if defects ≤ 2. Re = 3, reject entire lot if defects ≥ 3. 11/23/2020 IENG 486 Statistical Quality & Process Control 12

AQL Plan K Sample 125 units Ac = 1, accept if defects ≤ 1.

AQL Plan K Sample 125 units Ac = 1, accept if defects ≤ 1. Re = 2, reject entire lot if defects ≥ 2. 11/23/2020 IENG 486 Statistical Quality & Process Control 13

AQL Plan K Sample 50 units Ac = 1, accept if defects ≤ 1.

AQL Plan K Sample 50 units Ac = 1, accept if defects ≤ 1. Re = 3, reject entire lot if defects ≥ 3. 11/23/2020 IENG 486 Statistical Quality & Process Control 14

Questions & Issues 11/23/2020 IENG 486 Statistical Quality & Process Control 15

Questions & Issues 11/23/2020 IENG 486 Statistical Quality & Process Control 15