Transcript IENG 486 Lecture 19: MIL Standard 105E

IENG 486 - Lecture 19
Introduction to Mil Std 105E
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Assignment
 Reading:
 Chapter 15
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Sections 15.1 – 15.2.4: pp. 632 - 646
Sections 15.4 – 15.4.3: pp. 655 – 663
 Homework:
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Download and complete Last Assign: Acceptance Sampling
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Requires MS Word for Nomograph
Requires MS Excel for AOQ pp.
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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
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We will consider single sampling plans for this course
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Inspection Types
 Normal Inspection
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Used at start of inspection activity
 Tightened Inspection
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Instituted when vendor’s recent quality history has deteriorated
Acceptance requirements for lots are more stringent
 Reduced Inspection
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Instituted when vendor’s recent quality history has been exceptionally
good
Sample size is usually smaller than under normal inspection
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Switching Rules
Start
AND conditions
- Production Steady
- 10 consecutive lots accepted
- Approved by responsible
authority
Reduced
2 out of 5 consecutive lots
rejected
Normal
Tightened
OR conditions
- Lot rejected
- Irregular production
- Lot meets neither accept
nor reject criteria
- Other conditions warrant
return to normal inspection
5 consecutive
lots accepted
10 consecutive lots remain
on tightened inspection
Discontinue
Inspection
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Procedure for
MIL STD 105E
 STEP 1: Choose AQL
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MIL STD 105E designed around Acceptable Quality Level, AQL
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Recall that the Acceptable Quality Level, AQL, is producer's largest
acceptable fraction defective in process
Typical AQL range:
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0.01%  AQL  10%
Specified by contract or authority responsible for sampling
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Procedure for
MIL STD 105E
 STEP 2: Choose inspection level
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Level II
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Level I
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Requires about one-half the amount of inspection as Level II
Use when less discrimination needed
Level III
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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
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Four special inspection levels used if very small samples necessary
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Procedure for
MIL STD 105E
 STEP 3–Determine lot size, N
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Lot size most likely dictated by vendor
 STEP 4: Find sample size code letter
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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
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Decide if Single, Double or Multiple sampling plan is to be used
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Procedure for
MIL STD 105E
 STEP 6: Find Sample Size, n, and Acceptance Level, c
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Given sample size letter code, use Master Tables: 15-5, 15-6,
and 15-7 on pp.658-660
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Find n and c for all three inspection types:
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Normal Inspection
Tightened Inspection
Reduced Inspection
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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.
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Normal Insp. Level
Lot Size
= 2000
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AQL
Plan K
Sample 125 units.
Ac = 2, accept if defects ≤ 2.
Re = 3, reject entire lot if defects ≥ 3.
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AQL
Plan K
Sample 125 units
Ac = 1, accept if defects ≤ 1.
Re = 2, reject entire lot if defects ≥ 2.
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AQL
Plan K
Sample 50 units
Ac = 1, accept if defects ≤ 1.
Re = 3, reject entire lot if defects ≥ 3.
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Questions & Issues
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