MIL-STD-1916抽样标准
一、 前言
为强调过程品管与持续不断改进的重要性，美军于1996年推出新版的抽样标准：MIL-STD-1916，用以取代MIL-STD-105E作为美军采购时主要选用的抽样标准。本标准的目的在鼓励供应商建立品质系统与使用有效的过程控制程序，以取代最终产品的抽样方式，希望供应商远离以AQL(Acceptable Quality Level)为主的抽样计划，而以预防性的品质制度代替它，故本标准之愿景在建立不合格过程改进之制度，而非最终检验品质之水准。
MTL-STD-1916与MIL-STD-105E抽样标准不同之处，主要有以下几点：
1、 抽样计划以单次抽样（含加严、正常及减量）为主，删除双次与多次抽样，抽样以“0收1退”（ZBA Zero Based Acceptance）当做判定标准，强调不允许不良品之存在。 2、 建立持续不断改善之品质系统制度与善用多项品质改善工具。 3、 以预防代替检验，在过程中执行统计过程品管（SPC）。
4、 对计数、计量及连续性抽样作业均可适用（分别有三种抽样表），不再像以往MIL-STD-105E仅限于计数值抽样，MIL-STD-414仅限于计量值抽样与MIL-STD-1235仅限于连续性抽样（以上标准美军均已废止）。
5、 把抽样视为一种浪费的行为，如供应商可提出不同产品的接收计划，如获顾客同意后，则可按约定的接收方式办理验收。
6、 MIL-STD-1916强调供应商品质系统的建立，以预防为主，而MIL-STD-105E强调顾客的抽样技术， 避免接收不合格件。
此外，以往最常用的MIL-STD-105E抽样标准，使用的查检表上就有加严、正常及减量等对应查检表数十个，在运用上并不是很方便，而MIL-STD-1916所使用的表格（含计数、计量及连续性抽样），就只有4个，在使用的简便性上，已有大大的改善。 二、 适用范围
1、 本标准所提供的品质计划与程序，不能减轻供应商满足顾客需求的责任，供应商必须建立品质系统，包括制造程序，品管监控等作业，用以生产符合顾客品质要求的产品。 2、 本标准的抽样计划不适用于破坏性试验或无法筛选的产品。 三、 定义
•严重品质特性 Critical characteristic
MIL-STD-1916抽样标准（中文）
该特性不符合要求时，则在使用与维护的过程中将造成人员危害或不安全。 •关键不合格件 Critical nonconforming unit
不符合严重品质特性要求的不合格件，不符合事项中包含一项以上的重要品质特性。 •主要品质特性 Major characteristic
该特性不符合要求时，将导致产品失效或者降低使用性 •主要不合格件 Major nonconforming unit
符合所有严重品质特性，但不符合主要品质特性要求的不合格件，不符合事项中包含一项以上的主要品质特性。
•次要品质特性 Minor characteristic
该特性若不符合要求时，不会造成产品失效或者降低产品使用性。 •次要不合格件 Minor characteristic unit
符合关键与主要品质特性，但不符合次要品质特性的不合格件，不符合事项中包含一项以上的次要品质特性。
•生产期间 Production interval
在同一生产期间，其产品品质必须具有均一性，通常属常态性偏移，一般以单班生产的时间为定义，但亦可将生产期间订为一天（最大值不超过一天），期间所产生偏移量的改变，并不影响产品品质。 •品质计划 Quality program
产品从研发到生产期间，利用成本分析手法有效的规划、组织及管理各项活动或计划，使产品达成品质目标。
•水准 Verification level
顾客对产品品质所需求的“重要性水准”或“品质特性有效性”的陈述，是一项生产者努力品质保证的衡量方式，主要品质特性比次要品质特性需要更多的努力程度，VL-VⅡ表示生产者需要最高层级的努力水准，努力层级逐次降低至最低层级的VL-I。 四、 一般需求
1、 本标准当被纳入合约之中，则要求供应商执行抽样检验，然而必须认知的是，抽样检验并不能控制与改善品质，生产品质源自于适宜的过程控制方法，当此方法发挥效用时，抽样检验可视为次要的程序和不必要的成本浪费，供应商必须建立可接受的品质系统和证实有效的过程控制方法，作为执行抽样检验的先期条件。
2、 合约中应提及取代抽样检验的加一个可接受方法，此方法必须与抽样检验相互评估之后方可使用。
MIL-STD-1916抽样标准（中文）
该方法必须包括生产期间的过程能力分析与控制；另必须定期加以评估与监测。应至少达到严重品质特性之Cpk≥2，主要品质特性之Cpk≥1.33,次要品质特性之Cpk≥1，一旦此项要求被接受且证实已达成，则供应商可降低或删除抽样计划。
3、 供应商应建立顾客可接收的品质保证方法，如MIL-Q-9858，ISO9000，QS9000及SPC等，或其它经政府机构或顾客许可的品质系统。 4、 判定标准及不合格处理：
各项抽样计划均不允许不良品的发生，如发生则处理方式如下： ① 计量及计数型抽样计划，该批拒收，且需即进行纠正及预防措施。 ② 连续型抽样计划，该批拒收，并应执行全数筛选与即进行纠正及预防措施。 5、 抽样方法
采取随机抽样或按比例抽样，并应尽可能避免采取固定模式的抽样方式。 6、 被判定拒收，供应商必须进行下列行动：
① 对不合格件进行隔离，并进行必要的返修或重加工，经纠正的产品供应商必须先行筛选后，再重新抽样检验。
② 确定不合格原因，执行适当的过程变更。 ③ 执行正常、加严与减量检验的转换法则。
④ 各项纠正措施必须告知政府机构或顾客，并再次将重新筛选批送政府或顾客执行评估。 7、 对严重品质特性，除非另有规定，供应商必须执行自动化筛选作业，并且使用VL-VⅡ层级的抽样计划，若检验发现一项以上的不合格件，则需进行下列行动： ① 不得运交且通知政府机构或顾客。
② 确认原因，执行纠正措施，并执行100%筛选。 ③ 维持纠正措施的记录，以备政府机构或顾客的查验。 五、 品质管理系统的需求
1、供应商应建立以预防为主的品质系统，除了当作另一个可接受的方法外，亦展示供应商持续不断品质改进的决心。
2、 品质系统必须文件化，其内容至少要包括组织机构、权责、作业程序、工作道次与生产资源，供应商并且要持续改善此项品质系统，以确保运作的有效性与正确性。
3、 品质系统的独立，可依据ISO9000、MIL-Q-9858等标准加以规划，无论选择哪一种标准，品质系统必须以预防为主题，且需符合下列的目标：
MIL-STD-1916抽样标准（中文）
a) 影响品质的工作者必须了解品质系统的运作程序。 b) 产品必须符合或超越顾客需求。
c) 强调预防性的过程差异分析与不良率分析。
d) 当疵病发生时，必须立即寻找失效的产生原因与疵病来源，并且采取有效的纠正措施。 e) 使用统计分析方法与问题解析手法，用以降低过程变异量，改善过程能力与产品品质。 f) 保存记录，用以证实品质计划与过程控制的有效性。
4、 供应商必须对产品生产的相关过程加以研究与了解，通过文件化的程序证实供应商可以达成： a) 品质具有一致性，且执行完善的过程控制。 b) 降低设备变异，原料及其它输入源所产生的变异。 c) 只有标准化的操作程序以减少过程变异。 d) 进行过程设计，在目标值下提高精密度。
e) 具有不断过程改善的制度，通过过程变更与统计分析手法，达到过程预防与改善。 5、 程改善可使用的手法
a) 利用制造程序图规划重要控制点，用以阻止或侦测疵病之产生。
b) 过程不良原因的分析工具，如PDCA循环（Plan-Do-Check-Action）、FMEA(Failure Modes and Effects Analysis)、柏拉图分析(Paroto Analysis)及要因分析(Cause and Effect Analysis)等。 c) 过程改善过程的评估工具，如趋势分析、品质成本、生产效率、不良品率及6个标准差(6-sigma)的能力。
d) 利用实验计划，降低变异源产生之机率，改善生产力。 6、 过程控制可使用的手法
a) 确认过程控制技术的使用范围，如统计过程品管（SPC）、自动化、量具、预防保养、目视检验等。 b) 过程控制计划（Process control plan）必须包括SPC。 c) 通过资料分析，显示供应商过程控制措施是有效性的。 d) 根据工作的需要，执行适宜的教育训练。
e) 确认各单位在SPC相互作用上的权责与工作内容。
f) 使用控制图之前，必须先行确定每次抽样数与抽样频率，并建立修正控制界线的作业程序与律定超出控制范围的准则。
g) 确认所指定品质特性的关键参数，并找出影响关键参数的生产程序。 h) 律定过程改进的权责，对纠正措施进行追踪，直至失效原因被消除为止。
MIL-STD-1916抽样标准（中文）
i) 执行量测系统分析（MSA Measurement System Analysis），了解量仪具的变异量。 7、 产品符合性可使用的手法
包括使用控制图，利用记录与纠正及预防措施，执行过程能力分析（如CPK、CP），或通过过去统计资料进行趋势分析，最后则100%检验。 六、 如何进行抽样计划
1、抽样计划的步骤：
① 根据品质要求指定不同等级之VL（共有7个等级）， ② 选定抽样的形式（计量、计数、连续抽样）
③ 根据批量大小或生产期间生产量与VL决定样本代字CL(Code Letter)。 ④ 执行转换程序（正常、加严、减量）。
表1样本代字（CL）对照表
批量 2-170 171-288 289-544 545-960 961-1632 1633-3072 3073-5440 5441-9216 9217-17408 17409-30720 ≥30721
Ⅶ A A A A A A A B C D E
Ⅵ A A A A A A B C D E E
验证水平（VL）
Ⅴ A A A A A B C D E E E
Ⅳ A A A A B C D E E E E
Ⅲ A A A B C D E E E E E
Ⅱ A A B C D E E E E E E
Ⅰ A B C D E E E E E E E
MIL-STD-1916抽样标准（中文）
表2计数值抽样计划
验证水准（VL）
T
Ⅶ
Ⅵ
Ⅴ
Ⅳ
Ⅲ
Ⅱ
Ⅰ
R
样本代字（CL）
A B C D E
样本大小
3072 4096 5120 6144 8192
12801536204825603072
512 640 768 10241280
192 256 320 384 512
80 96 128 160 192
32 40 48 64 80
12 16 20 24 32
5 6 8 10 12
3 3 3 4 5
1、当批量比样本量小则100%检验
2、加严检验在正常检验VL左边之隔栏，减量检验则为右边之隔栏。
MIL-STD-1916抽样标准（中文）
表3计量值抽样计划
验证水平（VL）
样本代字（CL）
加严
Ⅶ
A B C D E A B C D E A B C D E
0.14 0.13 0.13 0.13 0.13
0.150.140.140.140.14
0.160.150.150.150.15
3.51 3.58 3.64 3.69 3.76
3.273.323.4 3.463.51
113 122 129 136 145
87 92 100 107 113
64 69 74 81 87
44 49 54 58 64 Ⅵ
Ⅴ
Ⅳ 样本大小
29 32 37 41 44
18 20 23 26 29
9 11 13 15 18
4 5 7 8 9
2 2 2 3 4
Ⅲ
Ⅱ
Ⅰ
减量
K法（适用单边规格或双边规格者） 3 3.073.123.213.27
2.692.792.862.913
2.4 2.462.562.632.69
2.052.142.212.322.4
1.64 1.77 1.86 1.93 2.05
1.21 1.33 1.45 1.56 1.64
1.2 1.2 1.2 1.2 1.21
F法(适用双边规格者) 0.170.170.170.160.16
0.190.190.180.180.17
0.220.210.210.2 0.19
0.27 0.25 0.24 0.23 0.22
0.37 0.33 0.3 0.28 0.27
0.710.710.710.440.37
1、如批量比样本数小时，100%检验
2、加严检验在正常检验VL的左边，减量检验则右边
MIL-STD-1916抽样标准（中文）
表4连续性抽样计划
样本代
验证水平（VL）
加严
Ⅶ
Ⅵ
Ⅴ
Ⅳ
Ⅲ
Ⅱ
Ⅰ
减量
字（CL）
A B C D E A B C D E
筛选阶段：筛选数量
3867 7061 11337 16827 26912
2207 3402 5609 8411 11868
1134 1754 2524 3957 5709
527 842 1237 1714 2605
264 372 572 815 1101
125 180 246 368 513
55 83 116 155 228
27 36 53 73 96
NA NA NA NA NA
抽样阶段：频率
37624 37728 37627 37669 37633
37728 37627 37669 37633 37638
3762737669376333763837645
376693763337638376451/34
3763337638376451/34 1/48
37638 37645 1/34 1/48 1/68
37645 1/34 1/48 1/68 1/96
1/34 1/48 1/68 1/96 1/136
1/48 1/68 1/96 1/1361/192
3、 一般注意事项：
① 在合约或产品规格中指定VL，一项VL可使用在不同的品质特性。表1的批量与VL决定样本代字CL，表2计数值抽样、表3计量值抽样与表4连续性抽样的VL和CL决定产品的抽样计划，用以评估产品符合合约和规格需求的程度，抽样合格的产品可通过转换法则在下次抽样时执行减量检验。 ② 抽样水准分成正常检验、加严检验与减量检验等三阶段，除非另有其它规定，VL值以正常检验为启始，加严检验的VL在表2与表3的左边，减量检验则在右边，而表4的执行方式则较复杂，请参照表4附注说明。每一项品质特性的抽样水准不能改变。除非执行转换法则。
③ 正常检验、加严检验及减量检验的转换法则系根据不同的VL在表2、3与4中执行抽样检验，转
MIL-STD-1916抽样标准（中文）
换法则的运作与纠正的结果（复验）无关，仅与初检的结果有关。 4、 各项抽样标准执行说明： ① 计数值抽样：
正常检验、加严检验与减量检验的抽样计划如表2所示，表中样本大小需随从批中随机抽出，经检验若无不合格件产生（零不良），则该批允收。 ②计量值抽样：
A、 正常、加严检验与减量检验的抽样计划如表3所示，计量值抽样不能任意使用，它必须假设数据的来源（量测结果）是独立性的且符合常态分布，在相同条件下（CL及VL）计数值的检验结果，并不保证与计量值的检验结果具有一致性。
B、 计量值抽样结果若属允收，除必须所有样本的测量结果均在规格之内，且符合表3的K法（不良率的估计）或F法（过程变异量占公差的百分比）的判定准则，若上述两者无法同时满足则拒收。 K法：适合单边规格与双边规格的产品
·单边规格：若（U-Xbar）/δ≥K或（Xbar-L）/δ≥K，则产品允收。 ·双边规格：若（U-Xbar）/δ≥K且（Xbar-L）/δ≥K，则产品允收。 F法：适合双边规格之产品者 若δ/（U-L）≤F，则产品允收。
Xbar=样本平均值，δ=样本标准差，U=规格上限，L=规格下限。 ③连续性抽样：
1. 执行连续性抽样的前提： a) 移动性的产品。
b) 在检验站或检验站附近，有足够的空间、设备、人力可执行100%检验。 c) 此过程可生产出品质稳定的产品。 2. 连续性抽样计划步骤：
执行时首先应依照表4筛选阶段执行100%检验，当符合下列条件时，可依表4进入抽样阶段。 a) 全数筛选的同型态产品处在稳定的状态。 b) 达到表4所规定的筛选数量。
当下列条件发生后，应停止抽样阶段，而改为100%检验的筛选阶段。 a.此生产过程被中断三个工作天以上。 b.当此同型态产品处在稳定的状态。
MIL-STD-1916抽样标准（中文）
c.在抽样时有任何的不符合项目被发现。 3. 对严重品质特性的额外要求
如在抽样阶段发现严重品质特性的不合格件，自上次合格件后的所有产品，均应执行100%检验。 4、转换法则：
① 正常检验转换加严检验：当发生下列任一条件，则必须由正常检验转换加严检验： A、 计数值及计量值抽样：最近2-5批中有2批被拒收。
B、 连续性抽样：在目前的抽样计划（不论是抽样或筛选阶段）期间，于执行5倍的样本大小过程中（此处的样本大小，应依照表2方式赋予）发现2个以上的不合格件。
② 加严检验转换正常检验：当下列两条件均符合时，则由加严检验转换正常检验： A、 不合格件的疵病原因已完成纠正。 B、 计数值及计量值抽样：且连续5批被允收。
C、 连续性抽样：在目前的抽样计划（不论是抽样或筛选阶段）期间，于执行5倍的样本大小过程中，无任何的不合格件。 ③ 正常检验转换减量检验：
当下列四条件均符合时，则由正常检验转换减量检验： A、 计数值及计量值抽样：连续10批被允收；
连续性抽样：在目前的抽样计划（不论是抽样或筛选阶段）期间，于执行10倍的样本大小过程中，无任何的不合格件。 B、生产是在稳定的阶段。
C、品质系统正常运作，且表现被政府机构或顾客认为满意。 D、政府机构或顾客同意减量检验，始可进行。 ④ 减量检验转换正常检验：
当发生下列任一条件，则必须由减量检验转换正常检验
A、 计数值及计量值抽样：有1批被拒收。连续性抽样：有任何不合格被发现； B、 生产情况不规则与延迟。
C、 品质系统运作表现被政府机构或顾客认为不满意。
D、 政府机构或顾客因其它生产条件之故，认为应回复正常检验。
MIL-STD-1916抽样标准（中文）
七、范例说明
1、 计数值抽样：
合约对品质的要求指定为VL-Ⅳ，供应商的交运批量可依需要弹性调整，表5为最近10批依计数值抽样的检验结果。 2、 计量值抽样：
合约对品质的要求指定为VL-Ⅰ，检验项目为操作温度，规定下限为180ºF，规格上限为209ºF，该批产品的批量为N=40，从表Ⅰ之VL及批量查到CL为A，从表3之VL及CL查到样本大小为n=4。假设此4件样本的量测数据为197、188、184及205，计算结果如下所示： Xbar=193.5, δ=9.399
（U-Xbar）/δ=1.649 （Xbar-L）/δ=1.436，δ/（U-L）=0.324
•K法： 从表3之VL-I及CL（A）查出K=1.21,计算结果1.649与1.436均≥K. •F法 从表3之VL-I及CL(A)查出F=0.370,计算结果0.324 批号 1 2 3 4 5 6 7 8 9 10 批量 样本样本不合格品质判定5000 900 3000 1000 1000 900 2000 2500 3000 5000 D A C B B A C C C D 160 80 128 256 256 192 320 320 128 160 2010000000 拒收允收拒收允收允收允收允收允收允收允收 抽样等级正常正常正常加严加严加严加严加严正常正常 备注 开始为正常检验 最近2-5批中有2批不合格，采用Ⅳ左边V之样本大小 过程已得到纠正，连续5批均回到Ⅳ之样本大小 MIL-STD-1916抽样标准（中文） 表6连续性抽样检验范例 频率或 产品序号 样本代字 1 1 8 124 170 C C C C 1 1 1 1/48 抽样 事件/行动 等级 正常 正常 正常 正常 开始生产，进行116件之筛选 发现1件不合格件，重新计数 连续116件合格，转为抽样阶段，频率为1/48 第一批选取的随机样本：结果合格 1.连续200件（10倍的样本大小）抽样：样本合格 9697 C 1/48 正常 2．转减量检验，频率为1/68 （注：据表2，在CL=C及VL-Ⅱ时，样本大小为 9769 C 1/68 减量 随机样本抽取，频率1/68，结果合格。 1.生产批量增加三倍(2100至2400件) 13982 C 1/68 减量 2.结束CL=C而以CL=E（重依批量查表1）阶段进3．另因现在VL-Ⅱ及减量阶段，查表4，频率为 14121 E 1/136 减量 在新频率1/136下,第一件随机样本抽取,结果合格,1.发现一件不合格品， 16290 E 1/136 减量 2.转回正常抽样 3．开始筛选阶段,进行数量228件之筛选,因目前处 16518 E 1 正常 连续228件均合格，开始抽样阶段，频率1/96 MIL-STD-1916抽样标准（中文） 八、 VL值的指定及选用 在MIL-STD-1916中，并没有特别指出VL如何指定，其实可以利用OC曲线分析，对表2进行转换，计算其不良率的估计值（在N≥10n状况下），如表7所示，顾客可根据产品品质要求，对照此表的不良率，制定合约所需的CL与VL，用以决定交付产品的抽样数，同样的亦可利用OC曲线分析，将表2所显示的允收概率加以估计，如表8所示，在相同不良率与允收水准（Ac=0，Re=1）下，允收机率愈小对品质要求愈严格。 表7计数值抽样（允收概率L(Pc)=0.9 ,Ac=0,Re=1）的不良率(%) 样本代字CL 验证水平VL T Ⅶ Ⅵ Ⅴ Ⅳ Ⅲ Ⅱ Ⅰ R 不良率% A B C D E 0.003 0.002 0.002 0.001 0.001 0.008 0.006 0.005 0.004 0.003 0.02 0.016 0.013 0.01 0.008 0.05 0.04 0.03 0.03 0.02 0.13 0.11 0.08 0.07 0.05 0.33 0.26 0.22 0.16 0.13 0.87 0.66 0.53 0.44 0.33 2.1 1.74 1.31 1.05 0.87 3.45 3.45 3.45 2.6 2.1 表8计数值抽样(P0=0.5%,Ac=0,Re=1)的允收率L(Pc) 验证水平VL 样本代字CL T Ⅶ Ⅵ Ⅴ Ⅳ Ⅲ Ⅱ Ⅰ R 允收概率L（Pc） A B C D E 0 0 0 0 0 0.002 5E-04 4E-05 3E-06 2E-07 0.077 0.04 0.02 0.006 0.002 0.38 0.28 0.2 0.15 0.08 0.67 0.62 0.53 0.45 0.38 0.85 0.82 0.79 0.73 0.67 0.94 0.92 0.9 0.89 0.85 0.97 0.97 0.96 0.95 0.94 0.99 0.99 0.99 0.98 0.97 MIL-STD-1916抽样标准（中文） OC曲线--批不合格率与接收概率的函数 计数抽样OC计算公式： MIL-STD-1916抽样标准（中文） MIL-STD-1916抽样标准（中文） MIL-STD-1916抽样标准（中文） MIL-STD-1916抽样标准（中文） MIL-STD-1916抽样标准（中文） 计量抽样计划有关公式的关系： 量值抽样计划的K参数统计量(Xbar-L)/s;(U-Xbar)/s;min(Ql,Qu)是反映规格值偏离平均值范围与特性值波动离散程度（标准差）的比。（即产品的规格值偏离中心值（均值）有多少个标准差数。查标准正态分布表可知偏离的标准差数对应的不合格率。而F值参数统计量s/(U-L),是规格范围与标准差的比,反映了规格的波动性. 由工序能力指数计算公式：（s为标准差） Cpl=(Xbar-L)/3s; Cpu=(U-Xbar)/3s; Cpk=min(Cpl,Cpu) Cp=(U-L)/6s=T/6s, Cpk=(1-2|M-Xbar|/T) Cp = (1-2|(U+L)/2-Xbar|/(U-L))((U-L)/6s) 可知,K,F参数都与Cpk有联系。 选用VL详细的请参看MIL-HDBK-1916 九、结语 希经由本文的介绍，使国内产业界可明了MIL-STD-1916的精神与执行方式；另希望企业可以舍去传统的抽样方式（如MIL-STD-105E），因为这不仅浪费人力、物力去执行抽样作业，对产品亦无加值的作用。 此外，由于MIL-STD-1916所着重的重点，已不再着重在事后的抽样，而是希望供应商能建立持续改善的品质管理系统，使缴交顾客的产品均为合格品，达到预防于先的效果，相信在通过持续与供应商之间的良性互动，可达到企业与供应商双赢的目的。 NOT MEASUREMENT SENSITIVE MIL-STD-19161 April 1996 DEPARTMENT OF DEFENSETEST METHOD STANDARD DOD PREFERRED METHODSFOR ACCEPTANCE OF PRODUCT AMSC N/AAREA QCIC DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. MIL-STD-1916 F O R E W O R D 1.This Military Standard is approved for use by all Departments and Agencies of theDepartment of Defense (DoD). 2.Beneficial comments (recommendations, additions, deletions) and any pertinent datawhich may be of use in improving this document should be addressed to: Commander, U.S. Army Armament Research, Development and Engineering Center, ATTN: AMSTA-AR-EDE-S,Picatinny Arsenal, NJ 07806-5000, by using the self-addressed Standardization DocumentImprovement Proposal (DD Form 1426) appearing at the end of this document or by letter.3.DoD procurement practices encourage industry innovation and provide flexibility toachieve the benefits of continuous improvement. 4.There is an evolving industrial product quality philosophy that recognizes the need forquality policy changes that will provide defense contractors with opportunities and incentivestoward improvement of product quality and cooperative relationships between the contractor andthe Government. 5.Process controls and statistical control methods are the preferable means of preventingnonconformances, controlling quality, and generating information for improvement. An effective process control system may also be used to provide information to assess the quality ofdeliverables submitted for acceptance. Suppliers are encouraged to use process control andstatistical control procedures for their internal control and to submit effective process controlprocedures in lieu of prescribed sampling requirements to the Government for approval.6.Sampling inspection by itself is an inefficient industrial practice for demonstratingconformance to the requirements of a contract and its technical data package. The application ofsampling plans for acceptance involves both consumer and producer risks; and increasedsampling is one way of reducing these risks, but it also increases costs. Suppliers can reducerisks by employing efficient processes with appropriate process controls. To the extent that suchpractices are employed and are effective, risk is controlled and, consequently, inspection andtesting can be reduced. 7.a.b.c. The following points provide the basis for this standard: Contractors are required to submit deliverables that conform to requirements and togenerate and maintain sufficient evidence of conformance. Contractors are responsible for establishing their own manufacturing and processcontrols to produce results in accordance with requirements. Contractors are expected to use recognized prevention practices such as processcontrols and statistical techniques. 8.This standard also provides a set of sampling plans and procedures for planning andconducting inspections to assess quality and conformance to contract requirements. Thisstandard complies with the DoD policy of eliminating acceptable quality levels (AQL's) andassociated practices within specifications. ii MIL-STD-1916 C O N T E N T S PARAGRAPHPAGE 1.SCOPE ................................................................................................................. 1.1Scope.................................................................................................................. 1.2Applicability ....................................................................................................... 1.3Applications........................................................................................................ 1.4Product requirements.......................................................................................... 1.5Limitations.......................................................................................................... 2.APPLICABLE DOCUMENTS.............................................................................. 2.1General............................................................................................................... 2.2Non-Government publications............................................................................. 2.3 Order of precedence............................................................................................ 3.DEFINITIONS...................................................................................................... 3.1Acronyms used in this standard........................................................................... 3.2Acceptance......................................................................................................... 3.3Contract quality requirements.............................................................................. 3.4Critical characteristic........................................................................................... 3.5Critical nonconforming unit................................................................................. 3.6Government contract quality assurance................................................................ 3.7Inspection........................................................................................................... 3.8Major characteristic............................................................................................. 3.9Major nonconforming unit................................................................................... 3.10Minor characteristic............................................................................................ 3.11Minor nonconforming unit................................................................................... 3.12Nonconformance................................................................................................. 3.13Nonconforming unit............................................................................................ 3.14Production interval.............................................................................................. 3.15Quality................................................................................................................ 3.16Quality assurance................................................................................................ 3.17Quality audit....................................................................................................... 3.18Quality program.................................................................................................. 3.19Screening inspection............................................................................................ 3.20Traceability......................................................................................................... 3.21Verification level (VL)........................................................................................ 4.GENERAL REQUIREMENTS............................................................................. 4.1Acceptance by contractor-proposed provisions.................................................... 4.1.1General............................................................................................................... 4.1.2 Requirements and procedures.............................................................................. iii 1 11112333455555566666666666667778888 MIL-STD-1916 C O N T E N T S PARAGRAPHPAGE 4.1.3 4.1.3.1 4.1.3.2 4.1.4 4.2 4.2.1 4.2.2 4.2.3 4.2.4 4.2.4.1 4.2.4.2 4.2.4.3 4.2.4.4 4.3 4.4 4.5 5. 5.1 5.1.1 5.1.2 5.1.3 5.1.4 5.1.4.1 5.1.4.2 5.1.4.3 5.2 5.2.1 5.2.1.1 5.2.1.2 5.2.1.3 5.2.1.3.1 5.2.1.3.2 5.2.1.3.3 5.2.1.3.4 5.2.1.4 5.2.2 5.2.2.1 5.2.2.1.1 Submission and incorporation..............................................................................Submission..........................................................................................................Incorporation......................................................................................................Withdrawal of approval of alternates...................................................................Acceptance by tables...........................................................................................Preferred sampling plans......................................................................................Formation and identification of lots or batches.....................................................Determination of sampling plan...........................................................................Sampling of lots or batches..................................................................................Selection of units.................................................................................................Representative (stratified) sampling.....................................................................Process of sampling.............................................................................................Non-conforming product.....................................................................................Disposition of nonconforming product................................................................Critical characteristics.........................................................................................Special reservations for critical nonconformance..................................................DETAILED REQUIREMENTS............................................................................Acceptance by contractor proposed-provisions ...................................................Quality system plan.............................................................................................Prevention-based quality system..........................................................................Process focus of quality system...........................................................................Objective evidence of quality system implementation and effectiveness................Examples of evidence regarding process improvement.........................................Examples of evidence regarding process control..................................................Examples of evidence regarding product conformance.........................................Acceptance by tables...........................................................................................Sampling inspection............................................................................................Verification level specification.............................................................................Sampling procedures...........................................................................................Switching procedures..........................................................................................Normal to tightened............................................................................................Tightened to normal............................................................................................Normal to reduced..............................................................................................Reduced to normal..............................................................................................Discontinuation of acceptance.............................................................................Preferred sampling inspection tables....................................................................Attributes sampling plans for lot or batch inspection............................................Acceptability criterion......................................................................................... iv 9 99999910101010101011111112121212121313131414141415151516161616171717 MIL-STD-1916 C O N T E N T S PARAGRAPHPAGE 5.2.2.2 5.2.2.2.1 5.2.2.2.2 5.2.2.2.3 5.2.2.3 5.2.2.3.1 5.2.2.3.2 5.2.2.3.3 5.2.2.3.3.1 6. 6.1 6.2 6.3 6.4TABLE I II III IVAPPENDIXFIGURE 1 2 3 4 5 Variables sampling plans for lot or batch inspection.............................................Limitations on use...............................................................................................Nonconforming unit............................................................................................Acceptability criteria...........................................................................................Continuous attributes sampling inspection plans..................................................Conditions for continuous sampling procedures...................................................Continuous sampling inspection procedure..........................................................Acceptability criterion.........................................................................................Special reservation for critical nonconforming unit..............................................NOTES..................................................................................................................Intended use........................................................................................................Issue of DoDISS.................................................................................................Supersession data................................................................................................Subject term (keyword listing)............................................................................. Code letters (CL) for entry into the sampling tables.............................................Attributes sampling plans....................................................................................Variables sampling plans.....................................................................................Continuous sampling plans..................................................................................Examples of sampling plan use............................................................................Attributes sampling inspection log.......................................................................Computations for single specification limit case...................................................Computations for double specification limit case..................................................Continuous sampling inspection log.....................................................................Procedure to determine a valid f..........................................................................CONCLUDING MATERIAL................................................................................v 17 17181820202121212222222222 1517192023 242526272829 MIL-STD-1916 1. SCOPE 1.1 Scope. The purpose of this standard is to encourage defense contractors and othercommercial organizations supplying goods and services to the U.S. Government to submitefficient and effective process control (prevention) procedures in place of prescribed samplingrequirements. The goal is to support the movement away from an AQL-based inspection(detection) strategy to implementation of an effective prevention-based strategy including a comprehensive quality system, continuous improvement and a partnership with the Government.The underlying theme is a partnership between DoD and the defense supplier, with the requisitecompetence of both parties, and a clear mutual benefit from processes capable of consistentlyhigh quality products and services. The objective is to create an atmosphere where every noncompliance is an opportunity for corrective action and improvement rather than one whereacceptable quality levels are the contractually sufficient goals. 1.2 Applicability. This standard, when referenced in the contract, specification, orpurchase order, is applicable to the prime contractor, and should be extended to subcontractorsor vendor facilities. The quality plans are to be applied as specified in the contract documents,and deliverables may be submitted for acceptance if the requirements of this standard have beenmet. 1.3 Applications. Quality plans and procedures in this standard may be used whenappropriate to assess conformance to requirements of the following: a.b.c.d.e.f.g.h. End items Components or basic materialsOperations or servicesMaterials in processSupplies in storageMaintenance operationsData or records Administrative procedures Note, use of the word \"product\" throughout this standard also refers to services and otherdeliverables. 1.4 Product requirements. The contractor is required to submit product that meets allcontract and specification requirements. The application of the quality plans or procedures ofthis standard does not relieve the contractor of responsibility for meeting all contract productrequirements. The contractor’s quality system, including manufacturing processes and qualitycontrol measures, will be established and operated to consistently produce products that meet allrequirements. Absence of any inspection or process control requirement in the contract does not 1 MIL-STD-1916 relieve the contractor of responsibility for assuring that all products or supplies submitted to theGovernment for acceptance conform to all requirements of the contract. 1.5 Limitations. The sampling plans and procedures of this standard are not intended foruse with destructive tests or where product screening is not feasible or desirable. In such cases,the sampling plans to be used will be specified in the contract or product specifications. 2 MIL-STD-1916 2. APPLICABLE DOCUMENTS 2.1 General. The documents listed in this section are specified in sections 3, 4, and 5 of thisstandard. This section does not include documents cited in other sections of this standard orrecommended for additional information or as examples. While every effort has been made toensure the completeness of this list, document users are cautioned that they must meet allspecified requirements documents cited in sections 3, 4, and 5 of this standard, whether or notthey are listed. 2.2 Non-Government publications. The following documents form a part of this documentto the extent specified herein. Unless otherwise specified, the issues of the documents which areDoD adopted are those listed in the issue of the DoDISS cited in the solicitation. Unlessotherwise specified, the issues of documents not listed in the DoDISS are the issues of thedocuments cited in the solicitation (see 6.2). AMERICAN NATIONAL STANDARDS INSTITUTE/AMERICAN SOCIETY FORQUALITY CONTROL (ANSI/ASQC) ANSI Z1.1/ASQC B1ANSI Z1.2/ASQC B2ANSI Z1.3/ASQC B3ANSI/ASQC Q9000ANSI/ASQC Q9004 -Guide for Quality Control Charts.-Control Chart Methods of Analyzing Data. -Control Chart Method of Controlling Quality DuringProduction.-Quality Management and Quality Assurance StandardsGuidelines for Selection and Use.-Quality Management and Quality System ElementsGuidelines. INTERNATIONAL ORGANIZATION OF STANDARDS (ISO) ISO 8402ISO 9000ISO 9004 -Quality - Vocabulary. -Quality Management and Quality Assurance Standards - Guidelines for Selection and Use.-Quality Management and Quality System Elements - Guidelines. (Copies of DoD adopted non-Government Standards are available to Military activitiesthrough the DoD Single Stock Point, Standardization Documents Order Desk, Bldg. 4D, 700Robbins Avenue, Philadelphia, PA 19111-5094. Military activities may obtain copies of non-DoD adopted documents from the sponsoring Industry Association. Non-military activities mayobtain copies of non-Government standards and publications from the American Society forQuality Control, PO Box 3066, Milwaukee, WI 53201-3066 and the American NationalStandards Institute, 1430 Broadway, New York, NY 10018, as appropriate.) 3 MIL-STD-1916 2.3 Order of precedence. In the event of a conflict between the text of this documentand the references cited herein, the text of this document takes precedence. Nothing in thisdocument, however, supersedes applicable laws and regulations unless a specific exemption hasbeen obtained. 4 MIL-STD-1916 3. DEFINITIONS 3.1 Acronyms used in this standard. The acronyms used in this standard are defined asfollows a.b.c.d.e.f.g.h.i.j.k.l.n.o.p.q. ACOANSIAQLASQCCLDFARSDoDDoDISSDoDSSPFARFMEAISOPDCAQARSPCVL - Administrative Contracting Officer.- American National Standards Institute.- Acceptable Quality Level. - American Society for Quality Control.- Code Letter. - DoD Federal Acquisitions Regulation Supplement.- Department of Defense. - DoD Index of Specifications and Standards.- DoD Single Stock Point.- Federal Acquisitions Regulation.- Failure Modes and Effects Analysis. - International Organization for Standardization.- Procurement Contracting Officer.- Plan-Do-Check-Act. - Quality Assurance Representative.- Statistical Process Control.- Verification Level. m.PCO 3.2 Acceptance. The act of an authorized representative of the Government by whichthe Government, for itself or as agent of another, assumes ownership of existing identifiedsupplies tendered or approves specific services rendered as partial or complete performance ofthe contract. (FAR 46.101) 3.3 Contract quality requirements. The technical requirements in the contract relating tothe quality of the product or service and those contract clauses prescribing inspection, and otherquality controls incumbent on the contractor, to assure that the product or service conforms tothe contractual requirements. (FAR 46.101) 3.4 Critical characteristic. A characteristic that judgment and experience indicate mustbe met to avoid hazardous or unsafe conditions for individuals using, maintaining, or dependingupon the product; or that judgment and experience indicate must be met to assure performanceof the tactical function of a major item such as a ship, aircraft, tank, missile, or space vehicle.3.5 Critical nonconforming unit. A unit of product that fails to conform to specifiedrequirements for one or more critical characteristics. 5 MIL-STD-1916 3.6 Government contract quality assurance. The various functions, including inspection,performed by the Government to determine whether a contractor has fulfilled the contractobligations pertaining to quality and quantity. (FAR 46.101) 3.7 Inspection. Examining and testing supplies or services (including, when appropriate,raw materials, components, and intermediate assemblies) to determine whether they conform tocontract requirements. (FAR 46.101) 3.8 Major characteristic. A characteristic, other than critical, that must be met to avoidfailure or material reduction of usability of the unit of product for intended purpose. 3.9 Major nonconforming unit. A unit of product that fails to conform to specifiedrequirements for one or more major characteristics, but conforms to all critical characteristics.3.10 Minor characteristic. A characteristic, other than critical or major, whose departurefrom its specification requirement is not likely to reduce materially the usability of the unit ofproduct for its intended purpose or whose departure from established standards has little bearingon the effective use or operation of the unit. 3.11 Minor nonconforming unit. A unit of product that fails to conform to specifiedrequirements of one or more minor characteristics, but conforms to all critical and majorcharacteristics. 3.12 Nonconformance. A departure from a specified requirement for any characteristic.3.13 Nonconforming unit. A unit of product that has one or more nonconformances.3.14 Production interval. A period of production under continuous sampling assumed toconsist of essentially homogeneous quality. It is normally a single shift. It can be a day if it isreasonably certain that shift changes do not affect quality of product, but shall not be longer thana day. 3.15 Quality. The composite of material attributes including performance features andcharacteristics of a product or service to satisfy a given need. (DFARS 46.101) 3.16 Quality assurance. A planned and systematic pattern of all actions necessary toprovide adequate confidence that adequate technical requirements are established; products andservices conform to established technical requirements; and satisfactory performance isachieved. (DFARS 46.101) 3.17 Quality audit. A systematic examination of the acts and decisions with respect toquality in order to independently verify or evaluate the operational requirements of the qualityprogram or the specification or contract requirements of the product or service. (DFARS 46.101)3.18 Quality program. A program which is developed, planned, and managed to carryout cost effectively all efforts to effect the quality of materials and services from concept 6 MIL-STD-1916 through validation, full-scale development, production, deployment, and disposal. (DFARS46.101) 3.19 Screening inspection. An inspection process whereby every unit is checked and allnonconforming units are removed; also referred to as 100 percent inspection. 3.20 Traceability. The ability to trace the history, application or location of an item oractivity, or similar items or activities, by means of recorded identification. (ISO 8402)3.21 Verification level (VL). Prescribes the level of significance or utility of acharacteristic to the user. The amount of effort to assure conformance can be allocated on thebasis of importance to the user. (Major characteristics will require more verification effort thanminor characteristics.) VL-VII requires the highest level of effort, and the effort decreases asthe VL decreases to the lowest level, VL-I. 7 MIL-STD-1916 4. GENERAL REQUIREMENTS 4.1 Acceptance by contractor-proposed provisions.4.1.1 General.a. This standard, when referenced in the contract or product specifications, requires thecontractor to perform sampling inspection in accordance with paragraph 4.2 and theproduct specification. However, it is recognized that sampling inspection alone doesnot control or improve quality. Product quality comes from proper product andprocess design and process control activities. When such activities are effective,sampling inspection is a redundant effort and an unnecessary cost. Contractors thathave an acceptable quality system and proven process controls on specific processesare encouraged to consider submitting alternate acceptance methods for one or morecontractually specified characteristics. In addition, contractors that have a successfulquality system and a history of successful process controls relevant to theproducts/services being procured in this contract, are encouraged to consider submitting a systemic alternate acceptance method for all the contractual samplinginspection requirements associated with paragraph 4.2. Submissions shall describe the alternate acceptance methods, the sampling inspection provision to be replaced, and an evaluation of the protection provided bythe alternate methods as compared with the inspection requirement to be replaced.The alternate acceptance method shall include evidence of process control andcapability during production together with adequate criteria, measurement, andevaluation procedures to maintain control of the process. The acceptability of thealternate acceptance methods is dependent upon the existence of a quality system,the demonstration of its process focus, and the availability of objective evidence ofeffectiveness. b. 4.1.2 Requirements and procedures.a. Contractors currently operating quality systems in accordance with such models asMIL-Q-9858 enhanced with Statistical Process Controls (SPC), ANSI/ASQC Q9004, or others that are deemed satisfactory to the Government representative arequalified to apply for alternate acceptance methods if demonstration of process focusand objective evidence of effectiveness exists. The contractor shall include in his request for approval of an alternate acceptancemethod an assessment plan to periodically verify process stability, capability, andother conditions under which the alternate acceptance method was developed. Thecurrent minimum values of process capability are equivalent to a Cpk of 2.00 forcritical characteristics, 1.33 for major characteristics, and 1.00 for minor 8 b. MIL-STD-1916 characteristics. Upon approval of the assessment plan, the contractor may reduce oreliminate inspection sampling when the plan criteria are met or exceeded.4.1.3 Submission and incorporation.4.1.3.1 Submission. There are two ways of submitting alternate acceptance methods:a. Submission of individual alternate acceptance methods for one or more contractuallyspecified sampling inspection requirements through the Government qualityassurance representative (QAR) to the procuring contracting officer (PCO) forapproval at any time during the contract period of performance. Submission of a systemic alternate acceptance method to the PCO prior to contractbeing awarded. This pre-approval allows the contractor to adopt alternate acceptance methods throughout the length of the contract. After contract award,submissions of a systemic alternate acceptance method should be made through theadministrative contracting officer (ACO) to the PCO. b. 4.1.3.2 Incorporation. All approved alternate acceptance methods shall be incorporatedinto the contractor’s manufacturing and quality program plans or other vehicles acceptable to thecontracting agency, as applicable. 4.1.4 Withdrawal of approval of alternates. The Government reserves the right towithdraw approval of alternate acceptance methods that are determined to provide less assuranceof quality than the inspection requirements originally specified or when the inability to maintainprocess stability and capability over time becomes apparent. 4.2 Acceptance by tables.4.2.1 Preferred sampling plans. This standard establishes three sets of matched samplingplans for the sampling inspection of product submitted to the Government for acceptance. Thesesampling plans provide for inspecting the samples from lots or batches by attributes or variablesmeasurement and for continuous sampling by attributes measurement. The three sets of matchedsampling plans are indexed by seven specified verification levels (VL) and five code letters(CL), which are determined by the lot or production interval size. The sampling plans arematched between corresponding VL and CL combinations to result in essentially similarprotection. The contractor has the option to utilize the type of plan, at the same verificationlevel, that best complements the production process. 4.2.2 Formation and identification of lots or batches. The product shall be assembledinto identifiable lots, sublots, or batches, or in such other manner as may be prescribed. Each lotor batch shall, as far as practicable, consist of units of product of a single type, grade, class, size,and composition, manufactured under essentially the same conditions, and at essentially thesame time. The lots or batches shall be identified by the contractor and shall be kept intact in 9 MIL-STD-1916 adequate and suitable storage space. Although lot or batch size is not used to select a continuoussampling plan, the formation of lots or batches may remain desirable for reasons ofhomogeneity, shipping convenience, and facilitation of payment. 4.2.3 Determination of sampling plan. A sampling plan is determined by:a.b.c.d. Verification level (VL) as specified. Type of sampling (attributes, variables, or continuous).Lot or production interval size code letter (CL) from Table I.Switching procedure (normal, tightened, reduced). For lot acceptance situations (attributes or variables), the occurrence of one or more nonconformances shall result in withholding acceptance of the product submitted and initiationof corrective action. When continuous sampling is in effect, the occurrence of a nonconformingunit while in a sampling phase results in withholding acceptance of that unit, a return toscreening, and initiation of corrective action. If a nonconforming unit is found while in ascreening phase, acceptance is withheld for that unit and screening is continued until therequirements of paragraph 5.2.2.3.2 are satisfied. 4.2.4 Sampling of lots or batches.4.2.4.1 Selection of units. Units of product drawn from a lot for a sample shall beselected at random from the lot without regard to their quality. Random sampling requires thateach unit in the lot, batch, or production interval has the same probability of being selected forthe sample. 4.2.4.2 Representative (stratified) sampling. When appropriate, the number of units inthe sample shall be selected in proportion to the size of sublots or subbatches, or parts of the lotor batch, identified by some rational criterion. When representative sampling is used, the unitsfrom each sublot, subbatch, or part shall be selected at random. 4.2.4.3 Process of sampling. A sample may be drawn after all units comprising the lotor batch have been assembled, or sample units may be drawn during assembly of the lot orbatch, in which case the size of the lot or batch shall be determined before samples are drawn.When the lot or batch passes the sampling plan, such lots or batches are acceptable and may besubmitted to the Government. 4.2.4.4 Non-conforming product. When sample units are drawn during lot or batchassembly and nonconforming units are found, the contractor shall withhold from acceptance thatportion of the lot completed and all additional production occurring prior to the initiation andverification of corrective action. For lots or batches withheld from acceptance, the contractorshall take the following actions: 10 MIL-STD-1916 a.Screen the lots or batches and dispose of all nonconforming units in accordance withparagraph 4.3.b.Determine the cause of the nonconformances and implement appropriate processchanges.c.Initiate the switching requirements of paragraph 5.2.1.3. d.Advise the Government representative of actions taken and resubmit the screened lotor batches to the Government for evaluation/consideration. 4.3 Disposition of nonconforming product. All units of product found to benonconforming by the contractor shall be removed and kept apart from the flow of production orotherwise identified or segregated to preclude submission to the Government. The contractormay rework or repair these units unless the contract excludes such activities. Corrected productshall be screened by the contractor and resubmitted to the Government apart from the regularflow of the product. 4.4 Critical characteristics. Unless otherwise specified in the contract or productspecifications, the contractor is required for each critical characteristic to implement an automated screening or a fail safe manufacturing operation and apply sampling plan VL-VII toverify the performance of the screening operation. The occurrence of one or more criticalnonconformances requires corrective action as specified in paragraph 4.5. 4.5 Special reservations for critical nonconformance. When a critical nonconformanceis discovered at any phase of production or during any inspection, the following immediateactions are required: a.b.c.d.e. Prevent delivery of critical nonconforming units to the Government.Notify the Government representative.Identify the cause.Take corrective action.Screen all available units Records of corrective actions shall be maintained and made available to the Government representative. 11 MIL-STD-1916 5. DETAILED REQUIREMENTS 5.1 Acceptance by contractor-proposed provisions. In order for an alternate acceptancemethod to be considered, the contractor shall establish and implement an internal prevention-based quality system as a means of ensuring that all products conform to requirements specifiedby the contract and associated specifications and standards. The acceptability of the qualitysystem as part of the request for alternate acceptance method(s) is dependent on its compliancewith an industry-accepted quality system model, demonstration of its process focus, and theavailability of objective evidence of its implementation and effectiveness. 5.1.1 Quality system plan. The quality system shall be documented and shall be subjectto on-site Government review throughout the contract. It shall include, at a minimum, a description of the organizational structure, responsibilities, procedures, processes, and resources.Such documentation is hereinafter called the quality system plan. The contractor shall maintain,disseminate, update, and improve the quality system plan in order to ensure its continued use andaccuracy. The design and documentation of the quality system plan shall allow for ease of use,review, and audit by internal as well as Government personnel. 5.1.2 Prevention-based quality system. The quality system shall be prevention-based.Common quality system models that reflect this philosophy include the ISO 9000 series, MIL-Q-9858 enhanced with SPC, and many industry specific total quality standards and programs. Thequality system shall also reflect additional needs in accordance with the requirements of thisstandard. Regardless of the model chosen, the quality system shall demonstrate its prevention-based outlook by meeting the following objectives throughout all areas of contract performance: a.The quality system is understood and executed by all personnel having any influenceon product or process quality.b.Products and services meet or exceed customer requirements.c.Quality is deliberately and economically controlled. d.Emphasis is on the prevention of process discrepancies and product nonconformances.e.Discrepancies and nonconformances that do occur are readily detected, and root causecorrective actions are taken and verified.f.Sound problem solving and statistical methods are employed to continuously reduceprocess variability and, in turn, improve process capability and product quality.g.Records are maintained and indicate implementation of the quality plan andeffectiveness of the control procedures. 5.1.3 Process focus of quality system. To demonstrate a process focus, the contractorshall demonstrate that the manufacturing process and its related processes have been studied andare understood, controlled, and documented to show that they are: a.Consistently producing conforming product. 12 MIL-STD-1916 b.Controlled as far upstream as possible. c.Robust to variation in equipment, raw materials, and other process inputs, anddesigned to yield a quality product.d.Operated with the intent to constantly strive to reduce process/product variability.e.Designed to utilize manufacturing equipment with objectives of minimum variabilityaround targeted values.f.Managed for continuous improvement. g.Designed and controlled using a combination of manufacturing practices andstatistical methods in order to ensure defect prevention and process improvement.5.1.4 Objective evidence of quality system implementation and effectiveness.5.1.4.1 Examples of evidence regarding process improvement.a.Process flow charts showing the key control points where action is taken to preventthe production of defective product.b.Identification of process improvement techniques and tools used, e.g., Plan-Do-Check-Act (PDCA) cycle, Failure Modes and Effects Analysis (FMEA), ParetoAnalysis, and Cause and Effect Analysis.c.Identification of the measures used, e.g., trend analysis, cost of quality, cycle timereduction, defect rates, 6-sigma capability.d.Results of the improvements from the use of these process improvement tools.e.Results of properly planned experiments that led to reduced common cause variabilityof a process and improved productivity5.1.4.2 Examples of evidence regarding process control.a.Identification of the scope of use of process control techniques, e.g., SPC, automation, gages, set-up verification, preventative maintenance, visual inspection.b.Process control plans, including the improvement goals and statements ofmanagement commitment to SPC. c.Approaches and supporting data used to determine if suppliers have adequate controlsto assure defective product is not produced and delivered.d.Descriptions of the required training in SPC and/or continuous improvement, i.e., thenumber of courses and their content, courses required for personnel at each organizational level and function associated with the quality plan, the qualifications ofthe instructors or trainers for SPC classes, support by management to attend suchcourses, and information demonstrating the effectiveness of the training. 13 MIL-STD-1916 e.Identification and definition of the interrelations of all departments (e.g., production,engineering, purchasing, marketing, administration, etc.) involved in SPC and qualityimprovement, their responsibilities, and the use of teams.f.When applying control charts, the reasoning behind establishing rational subgroupsand sampling frequency; the procedures for determining and updating control limits;and the criteria for determining out-of-control conditions.g.Identification of key parameters used in lieu of one or more specified characteristics,verification of the correlation of such parameters to those characteristics, anddescription of the manufacturing process steps responsible for these parameters.h.Identification of personnel responsible for process-related corrective action. i.Proper gage measurement studies showing measurement variations relative to the totalvariation.j.Traceability of the product and process corrective action(s) taken when the processwent out of statistical control, showing how the root cause was identified andeliminated.5.1.4.3 Examples of evidence regarding product conformance.a.Control charts showing the process in statistical control in accordance with the criteriaasked for in paragraph 5.1.4.2.f.b.Records of product and process corrective action(s) taken when nonconformancesoccur.c.Process capability studies consisting of the correct calculation and interpretation ofindices, such as Cp and Cpk.d.History of product inspection results reinforced by statistical data and analysis.e.Results from in-process control methods, such as 100 percent automated assemblyand/or inspection.5.2 Acceptance by tables.5.2.1 Sampling inspection. When acceptance is to be accomplished using the samplingtables provided in this document, the following considerations apply. 5.2.1.1 Verification level specification. The VL's are specified in the contract or productspecifications. A VL may be specified for individual characteristics, for a group of characteristics, or for subgroups of characteristics within the group. The VL and code letter (CL) from Table I determine the sampling plan required to assess product compliance to contractand specification requirements. Contractors are expected to produce and submit product in fullconformance to all requirements. Lots, batches, or production intervals of product thatconsistently meet or exceed all requirements will be accepted by the sampling plans of thisstandard and will result in qualifying for reduced sampling levels. 14 MIL-STD-1916 TABLE I. Code letters (CL) for entry into the sampling tablesLot or productioninterval size2–170171–288289–544545–960961–16321633–30723073–54405441–92169217–1740817409–3072030721 and largerVerification levelsVIIAAAAAAABCDEVIAAAAAABCDEEVAAAAABCDEEEIVAAAABCDEEEEIIIAAABCDEEEEEIIAABCDEEEEEEIABCDEEEEEEE5.2.1.2 Sampling procedures. Sampling is performed at one of three stages callednormal, tightened, and reduced. Unless otherwise specified, the VL stated in the contract shallbe considered the normal stage of inspection and shall be used at the start of inspection. Thetightened and the reduced stages are then defined as the stages to the immediate left and right,respectively, of the initial stage. The sampling inspection stage in effect shall continueunchanged for each group of characteristics or individual characteristic except where the switching procedures given in paragraph 5.2.1.3 require change. The switching procedures shallbe applied to each group of characteristics or to individual characteristics. 5.2.1.3 Switching procedures. The procedures for switching among normal, tightened,and reduced inspection are given as Note (2) in Tables II, III, and IV. The switching procedures are independent of the results of any remedial action, such as screening, additional samples, etc., resulting from the occurrence of sample nonconformancesand withholding of acceptance. Some Table IV switching criteria depend upon a corresponding Table II entry. These entries have been denoted by na(N) and na(T) in the descriptions that follow. na(N) representsthe Table II sample size used for normal sampling at the VL and CL currently in effect.Likewise, na(T) represents the tightened sample size. 5.2.1.3.1 Normal to tightened. When normal inspection is in effect, tightened inspection shall be instituted when one of the following conditions occurs, depending on the type ofsampling plan being used: Lot or batch sampling (Tables II and III): 2 lots or batches have been withheld from acceptance within the last 5 or fewer lots orbatches. 15 MIL-STD-1916 Continuous sampling (Table IV): 2 nonconforming units are found within a period of inspections (whether on sampling or screening) totaling no more than 5 times na(N). 5.2.1.3.2 Tightened to normal. When tightened inspection is in effect, normal inspection may be instituted when the following conditions are both satisfied: a.b. The cause for producing the nonconformances is corrected.Lot or batch sampling (Tables II and III): 5 consecutive lots/batches are accepted.Continuous sampling (Table IV): No nonconforming units have been found within a period of inspections(whether on sampling or screening) totaling at least 5 times na(T) units. 5.2.1.3.3 Normal to reduced. When normal inspection is in effect, reduced inspection may be instituted when the following conditions are all satisfied: a. Lot or batch sampling (Tables II and III): 10 consecutive lots/batches are accepted while on normal inspection.Continuous sampling (Table IV): No nonconforming units have been found within a period of inspections(whether on sampling or screening) totaling at least 10 times na(N) units .b.c.d. Production is at a steady rate. The contractor’s quality system is considered satisfactory by the Government.Reduced inspection is considered desirable by the Government. 5.2.1.3.4 Reduced to normal. When reduced inspection is in effect, normal inspection shall be instituted when one of the following conditions occur. a. Lot or batch sampling (Tables II and III): A lot/batch is withheld from acceptance.Continuous sampling (Table IV): A nonconforming unit is found. b.c.d. Production becomes irregular or delayed.The contractor’s quality system is unsatisfactory. Other conditions warrant that normal inspection be re-instituted. 5.2.1.4 Discontinuation of acceptance. If sampling inspection of lots or batches remains in tightened inspection due to discovery of nonconformances or when, on continuous sampling 16 MIL-STD-1916 plans, there are long periods of screening due to discovery of nonconformances, the Governmentreserves the right to discontinue acceptance of the product until the causes of nonconformancesare eliminated or other means acceptable to the procuring agency have been instituted. Whensampling inspection is restarted after discontinuation of acceptance, it shall be at the tightenedinspection stage. 5.2.2 Preferred sampling inspection tables. See the Appendix for methods of computingsampling results, using switching rules, and determining compliance with requirements using theattributes, variables, and continuous sampling plans contained in this section. 5.2.2.1 Attributes sampling plans for lot or batch inspection. The preferred attributessampling plans for lots or batches are described in Table II for normal, tightened, and reducedinspection. 5.2.2.1.1 Acceptability criterion. The lot or batch shall be considered acceptable only ifno nonconforming units are found upon inspection of the random sample of the size listed inTable II. TABLE II. Attributes sampling plansVerification levelsCodeletterABCDENOTES: T30724096512061448192VII12801536204825603072VI51264076810241280V192256320384512IVSample size (na)8096128160192III3240486480II1216202432I5681012R33345(1)When the lot size is less than or equal to the sample size, 100 percent attributes inspection is required. (2)One verification level (VL) to the left/right of the specified normal VL is the respective tightened/reduced plan. Tightened inspection of VL-VII is T, reduced inspection of VL-I is R. 5.2.2.2 Variables sampling plans for lot or batch inspection. The preferred variablessampling plans for lots or batches are described in Table III for normal, tightened, and reducedinspection. 5.2.2.2.1 Limitations on use. Variables sampling is not to be used indiscriminately. Itsuse shall depend upon evidence, provided by graphical or statistical analyses, that the assumptions of independence and normality are being met. Attribute sampling shall be usedwhenever the evidence fails to warrant use of variables sampling. 17 MIL-STD-1916 5.2.2.2.2 Nonconforming unit. For the purposes of variables sampling, a unit of productshall be considered nonconforming if its variables measurement is outside the specifiedtolerance. 5.2.2.2.3 Acceptability criteria. The lot or batch shall be considered acceptable if itssample contains no nonconforming units and the applicable \"k\" and \"F\" criteria (see Table III)are met. If the sample contains any nonconforming unit, or if the sample does not meet the \"k\"criterion, or if the sample does not meet the \"F\" criterion (when applicable), the lot does notmeet the acceptability criteria. a. k criterion, single-sided specification. For a single-sided specification the quantity(x−spec limit) shall be greater than or equal to the k value specified in Table III in s order to meet the \"k\" criterion. k criterion, double-sided specification. For a double-sided specification, each of the (x−L)(U−x) and must be greater than or equal to the k valuequantities ss specified in Table III in order to meet the \"k\" criterion. F criterion (only applicable in double-sided specifications). For a double-sided s must be less than or equal to the specified Fspecification the quantity (U−L) value in Table III in order to meet the \"F\" criterion. b. c. Note:x = sample mean, s = sample standard deviation, U = upper specification limit, L = lower specification limit. 18 MIL-STD-1916 TABLE III. Variables sampling plansVerification levelsCodeletterABCDET113122129136145VII 87 92100107113VI6469748187V4449545864IVSample size (nv)29323741441820232629 9111315184578922234IIIIIIRk values (one- or two-sided)ABCDE3.513.583.643.693.763.273.323.403.463.513.003.073.123.213.272.692.792.862.913.002.402.462.562.632.692.052.142.212.322.401.641.771.861.932.051.211.331.451.561.641.201.201.201.201.21F values (two-sided)ABCDENOTES:(1)(2) When the lot size is less than or equal to the sample size, 100 percent attributes inspection isrequired. One verification level (VL) to the left/right of the specified normal VL is the respective tightened/reduced plan. Tightened inspection of VL-VII is T, reduced inspection of VL-I is R. .136.134.132.130.128.145.143.140.138.136.157.154.152.148.145.174.168.165.162.157.193.188.182.177.174.222.214.208.199.193.271.253.242.233.222.370.333.301.283.271.707.707.707.435.3705.2.2.3 Continuous attributes sampling inspection plans. The preferred continuoussampling plans for inspection by attributes are described in Table IV for normal, tightened, andreduced inspection. 19 MIL-STD-1916 TABLE IV. Continuous sampling plansVerification levelsCodeletterABCDET 3867 7061113371682726912VII 2207 3402 5609 841111868VI11341754252439575709V 527 842123717142605IV2643725728151101III125180246368513II 55 83116155228I2736537396RNANANANANAScreening phase: clearance numbers (i)Sampling phase: frequencies (f)ABCDENOTES: (1)Use of other i and f combinations are permitted provided they are computed in accordance with Appendix, paragraph 30.5.(2)During the screening phase, one verification level (VL) to the left of the specified normal VL is the tightened plan. Tightened inspection of VL VII is T. There is no reduced plan while in the screeningphase. During the sampling phase, one verification level (VL) to the left/right of the specified normal VL is the respective tightened/reduced plan. Tightened inspection of VL-VII is T, reduced inspection ofVL-I is R.(3)Sample units shall be chosen with frequency (f) so as to give each unit of product an equal chance of being inspected. The inspector should allow the interval between sample units to vary somewhatrather than draw sample units according to a rigid pattern. 1/34/171/62/171/124/171/62/171/121/171/62/171/121/171/242/171/121/171/241/341/121/171/241/341/481/171/241/341/481/681/241/341/481/681/961/341/481/681/961/1361/481/681/961/1361/1925.2.2.3.1 Conditions for continuous sampling procedures. The following conditionsmust exist before the continuous attributes sampling procedures of this section may be used forinspection. a.Moving product. b.Ample space, equipment, and manpower at or near the inspection station to permit100 percent inspection when required.c.A process that is producing or is capable of producing material whose quality is stable. 20 MIL-STD-1916 5.2.2.3.2 Continuous sampling inspection procedure. At the start of production, all unitsare inspected. Sampling inspection may be initiated at frequency \"f\" when the followingconditions are satisfied: a.All units of product are of the same configuration and produced under stable conditions.b.At least \"i\" consecutive units inspected are free of nonconformances. Sampling inspection shall be terminated and 100 percent inspection resumed if either of the following conditions occur: a.The production process is interrupted for more than three operating days. b.The requirement that all units of product are of the same configuration and produced under stable conditions is not satisfied.c.A unit having any nonconformance is found during sampling. 5.2.2.3.3 Acceptability criterion. In continuous sampling, units of product aredetermined to be acceptable or not on essentially an individual basis. While 100 percentinspection is being performed, each unit is individually inspected and categorized as aconforming or a nonconforming unit and accepted or not accepted accordingly. While inspection is being performed on a sampling basis, each unit that is inspected is categorized asacceptable or not acceptable depending on whether it is found to be conforming or nonconforming and each unit not inspected is considered to be conforming and hence accepted.(See \"Special reservation for critical nonconforming unit\5.2.2.3.3.1 Special reservation for critical nonconforming unit. In addition to theprovisions of paragraph 4.5, if a critical nonconforming unit is found while on sampleinspection, all product since the last conforming unit was found shall be inspected. 21 MIL-STD-1916 6. NOTES (This section contains information of a general or explanatory nature that may be helpful, but is not mandatory). 6.1 Intended use. This document is intended for use in contracts in place of AQL-basedsampling documents. 6.2 Issue of DoDISS. When this standard is used in acquisition, the applicable issue ofthe DoDISS must be cited in the solicitation (see 2.2). 6.3 Supersession data. The following military standards are planned to be canceledwhen this standard is approved:a.MIL-STD-414 for Percent Defective - Sampling Procedures and Tables for Inspection by Variables b.MIL-STD-1235- Single-and Multi-Level Continuous Sampling Procedures and Tables for Inspection by Attributes 6.4 Subject term (keyword listing).AttributesContinuousControlProcessSamplingStatisticalVariablesVerification 22 MIL-STD-1916 APPENDIX EXAMPLES OF SAMPLING PLAN USE 10. SCOPE 10.1 General. This Appendix is not a mandatory part of the standard. The informationcontained herein is intended for guidance only. 10.2 Purpose. This Appendix illustrates how to implement the three types of samplingplans described in paragraphs 4 and 5 of this standard. The examples explain how to use thefour tables, how to apply the switching rules, and how to do some of the requisite calculations.In addition, this Appendix explains how the contractor can modify Table IV to some extent bycalculating and using other \"i\" and \"f\" values. 20. APPLICABLE DOCUMENTS. This section is not applicable to this Appendix.30. EXAMPLES 30.1 Attributes sampling. Wing nuts are to be inspected for missing thread. Averification level IV (VL-IV) has been specified. The producer chooses to use attributes Non-conform-ances201Lot #123LotSize50009003000CodeSampleLetterSizeDAC16080128LotDispositionWithholdAcceptanceAcceptWithholdAcceptanceAcceptAcceptAcceptAcceptAcceptStageT/N/RNNNActionBegin with normal sampling,VL-IV.2 lots out of 5 fail to pass.Switch to tightened VL-IV.Check process.456781000100090020002500BBACC25625619232032000000TTTTTProcess corrected and 5consecutive lots accepted.Switch to normal VL-IV.91030005000CD12816000AcceptAcceptNNFIGURE 1. Attributes sampling inspection log.23 MIL-STD-1916 APPENDIX sampling plans from Table II. Lot sizes may vary as a result of production decisions. Asegment of the producer’s experience is shown in figure 1. 30.2 Variables sampling (single-sided specification limit case). The maximumtemperature of operation for a certain device is specified as 209 (measured in degrees F). Verification level I (VL-I) has been specified. A lot of 40 items is submitted for inspection inaccordance with variables sampling. Table III requires a sample size of nv = 4 for code letter A.Suppose the measurements obtained are as follows: 197, 188, 184, and 205; and compliance LineInformation Needed12345678910Sample sizeSum of measurementsSum of squared measurementsCorrection factorCorrected sum of squaresSample varianceSample standard deviationSample meanLower specification limitUpper specification limitLower quality indexUpper quality indexQuality Index1112Sample F valueNumber of nonconformancesk valueF value13C acceptability criterionk acceptability criterionF acceptability criterionNOTES:SymbolFormulaResult4ExplanationSee Table IIInv∑x∑xCFSSVsxLUQLQUQFCkFC = 0 ?Q≥k ?F≤F ?(x−L)/s(U−x)/ss/(U−L)277415003414976926588.3339.399193.500Not applicable209Not applicable1.649(209-193.5)/9.399(774)2/4(∑x)2/nv2∑x−CF150034-149769265/3SS/(nv−1)V∑x/nv88.333774/4min(QL,QU)1.649Not applicable01.210Not applicableYesYesNot applicableSee Table IIISee Table III1.649≥1.21The k value is the minimum allowable value for the quality index, Q.The F value is the maximum allowable value for the sample F value, F.FIGURE 2. Computations for single specification limit case.24 MIL-STD-1916 APPENDIX with the acceptability criteria is to be determined. Computations are shown in figure 2. The lotis accepted since it meets all applicable acceptability criteria. 30.3 Variables sampling (double-sided specification limit case). The minimumtemperature of operation for a certain device is specified as 180 (measured in degrees F). Themaximum is 209. Verification level I (VL-I) has been specified. A lot of 40 items is submittedfor inspection in accordance with variables sampling. Table III requires a sample of size nv = 4for code letter A (CL-A). Suppose the measurements obtained are as follows: 197, 188, 184and 205; and compliance with the acceptability criteria is to be determined. Computations areshown in figure 3. The lot is accepted since it meets all applicable acceptability criteria. LineInformation Needed12345678910Sample sizeSum of measurementsSum of squared measurementsCorrection factorCorrected sum of squaresSample varianceSample standard deviationSample meanLower specification limitUpper specification limitLower quality indexUpper quality indexQuality Index1112Sample F valueNumber of nonconformancesk valueF value13C acceptability criterionk acceptability criterionF acceptability criterionSymbolFormulaResult4ExplanationSee Table IIInv∑x∑xCFSSVsxLUQLQUQFCkFC = 0 ?Q≥k ?F≤F ?(x−L)/s(U−x)/s277415003414976926588.3339.399193.5001802091.4361.6490.32401.2100.370YesYesYesSee Table IIISee Table III(193.5-180)/9.399(209-193.5)/9.3999.399/(209-180)(774)2/4(∑x)2/nv∑x2−CFSS/(nv−1)V∑x/nv150034-149769265/388.333774/4min(QL,QU)1.436s/(U−L)1.436≥1.2100.324≤0.370NOTES:The k value is the minimum allowable value for the quality index, Q.The F value is the maximum allowable value for the sample F value, F.FIGURE 3. Computations for double specification limit case.25 MIL-STD-1916 APPENDIX 30.4 Continuous sampling. A visual inspection of stamped metal parts for the presenceof a spot weld will be performed immediately after units pass through a spot welding station.Verification level II (VL-II) has been specified. The product will be submitted for continuousattributes sampling inspection. The production interval size is an 8-hour shift, which initiallywill consist of between 700 to 800 welded parts. With VL-II and code letter C (CL-C) fromTable I, the \"i\" and \"f\" values (Table IV) are found to be 116 and 1/48, respectively. A segmentof sampling experience is shown in figure 4. ProductItemNumber181241709697CodeLetterCCCCCFrequencyStageor 100%T/N/R100%100%100%1/481/48NNNNNEvent/ActionStart production: Begin screening phase with i = 116.Find a defective unit: Reset counter.i =116 consecutive conforming units cleared: Beginsampling phase with f = 1/48.First random sample selected: Found it to conform.200 consecutive conforming sampled units observed:Switch to reduced inspection with f = 1/68. Here, 200equals 10 times the Table II sample size entry for CL-Cand VL-II.Next sample randomly selected with f = 1/68.Production interval size tripled (2100 to 2400 units): EndCL-C and begin CL-E sampling phase, f = 1/136, sinceVL-II and reduced sampling inspection are in effect.First random sample taken with new f = 1/136: Found itto conform. Continue random sampling.A nonconforming unit observed: Switch to normalinspection. Initiate screening phase with i = 228, sinceCL-E and VL-II are in effect.i = 228 consecutive conforming units cleared: Beginsampling phase with f = 1/96.976913982CC1/681/68RR1412116290EE1/1361/136RR16518E100%NFIGURE 4. Continuous sampling inspection log.30.5 Continuous sampling - plan tailoring. The producer may opt to use anothercontinuous sampling plan instead of the one specified in Table IV. The only restrictions are thatsuch a change is not allowed while inside a screening sequence and that the new plan be derivedin accordance with the procedure described below. Certain circumstances make such choices desirable. Sometimes the selection of a clearance number or frequency is application dependent, e.g., if it matters that i or 1/f be a 26 MIL-STD-1916 APPENDIX multiple of pallet size. Availability and capability of screening and sampling crews are yetfurther considerations. The plan cited in Table IV consists of the largest i number and the smallest f number combination. Plans whose i is larger than the tabulated i, or whose f is smaller than thetabulated f, are not permitted. Producers willing to sample at rates larger than f can reduce isubstantially. The procedure that allows choice is presented by way of the preceding continuous sampling example situation as initially described, subject to one modification: the producerprefers to start with a plan having an i of 50 instead of the 116 specified. The procedure todetermine a valid f is as shown in figure 5. LineInformation Needed1234Clearance numberTarget i numberAttribute sample sizeCompute f0: Step 1Step 2Step 3Step 45Valid fSymbolFormulaResult116Yes20(na+1)(1+1/na)na(it+1)(1+1/it)it ExplanationTable IV50 < 116Table II, same VL, CLiitnaS1S2S3f0 it (S1−1)/[(S2)(S3)] Any f > f0 FIGURE 5. Procedure to determine a valid f.Therefore, an i of 50 may be used in lieu of 116 if f is increased from 1/48 to 1/6. If it is f that is preselected, the corresponding i may be found by trial and error, that is, by iterative implementation of the procedure described. The printed numerical results have been rounded to 4-decimal accuracy. However, use of the procedure requires that all calculations be performed with at least 6-digit precision.Evidence supporting the validity of numerical results shall be maintained and be available forreview upon request. Proper execution of the procedure ensures Tables IV and II are comparable with respect to the average fraction inspected and the average outgoing quality limit. 27 MIL-STD-1916 CONCLUDING MATERIAL Custodians: Army - AR Navy - OS Air Force - 05 DLA - DH Review activities: Army - AT, AV, CR, EA, GL, ME, MI, MR Navy - AP, AS, CH, EC, NM, NW, SA, SH, YD-1 Air Force - 10, 11, 13, 17, 19, 70, 71, 80, 82, 84 DLA - ES 28 Preparing activity: Army - AR (Project QCIC -0146) 因篇幅问题不能全部显示，请点此查看更多更全内容