IENG 486 Lecture 19: MIL Standard 105E
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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
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
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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
We will consider single sampling plans for this course
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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
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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
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:
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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
Level II
Level I
Requires about one-half the amount of inspection as Level II
Use when less discrimination needed
Level III
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
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
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Procedure for
MIL STD 105E
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:
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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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