Understand Gage R&R
& Understand Gage R&R
Figure 1. The total variation (TV) report analyzes the gage study data as a percentage of total variation. The report is divided into sections presenting the equipment variation, appraiser variation, part variation and the gage R&R. Source: InfinityQSAny quality professional worth his keep knows that gage repeatability and reproducibility (R&R) studies are a critical part of a successful process control system, but it is amazing how many do not understand how to properly conduct a study or how to interpret the results. Quality professionals know that measuring manufactured products is critical to maintaining the customer specification. They also know that measuring products is necessary for statistical process control systems designed to improve the manufacturing process itself. What is sometimes forgotten is that the data is only worthwhile if the measurement system itself is adequate. A gage R&R study will tell operators if the measurement system is acceptable for its intended use. The gage study also shows which part of the measurement system is contributing the most to the variation of the measurements and helps operators plan improvements to the system. Measurement systems contain variation from three main sources: the products themselves, the appraiser taking the measurements and the equipment used to perform the measurement. The gage study shows the contribution of each of these areas. In an adequate measurement system, one would expect to find most of the variation within the products. If the bulk of the variation is created by the appraisers or the equipment, then the system may not be suitable.
Conducting the StudyThe gage study consists of several parts that are repeatedly measured by multiple appraisers. While the numbers can vary, most studies use 10 parts and three appraisers who measure the parts at least three times each. The repeated measurements are called trials. Calculations are then made to determine the level of variation between the appraisers, parts and across the trials. It is not necessary to go into the actual calculations here since there are numerous software programs and templates available to assist operators. Instead, let’s focus on how to perform a valid study and how to interpret the results.Selecting part samples is perhaps the most critical step in performing a successful study-and probably the most misunderstood. Part samples used for gage studies should represent the true variation of the production process. A common mistake is trying to select production samples that are similar. Some instructions for gage studies even state that samples must be from the same batch. The truth is that using products that do not represent the variation of the process will cause the gage study results to be worthless. If necessary, operators may even select samples over a period of days or weeks to get samples that truly represent the process. Always remember that it is the measurement system that is being evaluated here, not the products. Now it is time to start measuring. Here are a few guidelines for the measuring process:The operators should share one calibrated gage or measurement system.Five or more samples that represent the range of the process variation should be used. Do not use one part or parts that have little variation. Samples should be measured in random order if possible. There should be at least two trials or measurements taken from each operator.
Figure 2. The average and mean report includes not only the measurements and calculations, but also a graph charting the appraiser results. This chart is useful in pinpointing appraiser training or method issues. Source: InfinityQSEvaluating the Gage StudyLet’s take a closer look at the various reports used to evaluate the gage study.The TV ReportThe total variation (TV) report analyzes the gage study data as a percentage of total variation. The report is divided into sections presenting the equipment variation, appraiser variation, part variation and the gage R&R.Equipment variation (EV) represents the repeatability of the equipment or measurement device. On the TV chart, it is presented as a percentage of the total variation of the system. See Figure 1. The equipment variation percentage is 17.6% of the total variation of the system. While the result in the example is low, a high percentage, greater than 30%, would tell operators that they have issues with the measurement equipment itself that must be resolved. The gage may need maintenance or perhaps the fixture holding the part for measurement is not adequate.Appraiser variation (AV) represents the reproducibility of the system. The TV chart also reports the AV as a percentage of the total variation of the system. A high percentage here, greater than 30%, indicates a large operator-to-operator difference. A possible cause could be operators not following proper measurement procedure, not trained properly or perhaps trained in different methods.Part variation (PV) represents the variation of the products or parts used to conduct the gage study. In the example, the PV% is 96.4%. One would expect to see a high percentage of the total variation from the parts on an adequate system where the parts truly represent the range of the process variation. If the PV% is low, less than 30%, the parts selected do not represent the full variation of the process.Gage repeatability and reproducibility (GR&R) represent both the equipment variation and the appraiser variation. The GR&R% returned in the TV report is the percentage of the total variation of the system used by the measurement system. In Figure 1, GR&R% is 26.7%. This means that 26.7% of the total variation is due to the measurement system itself. Rule of thumb for GR&R is that a result of 10% or less means that the system is acceptable. Most of the variation is from the parts and not the measurement system. If the GR&R is less than 30%, the system may be accepted, but there should be some plan to review the system for improvement. A GR&R result of greater than 30% shows that the system must be improved as the appraisers and equipment contribute to more than 30% of the system variation.Another critical calculation in determining if the gage study is valid is the number of distinct categories (NDC). The NDC is the calculation for the number of non-overlapping 97% confidence intervals that span the product variation. In other words, it is basically the part variation divided by the GR&R result and multiplied by a constant. The NDC should be five or greater for the study to be considered valid. As discussed earlier, a common problem with gage studies is that the part variation does not represent the expected process variation. If the part variation is too small, then the NDC will be below five and the study should not be considered valid. In this case, operators may sample again to obtain parts that do represent the full range of process variation. Remember to evaluate both part variation and gage R&R. If the gage R&R itself is too large, then the NDC will be low as well. If this occurs, operators could have an issue with AV, EV or the measurement system itself.When evaluating the TV report results, remember that these results are calculated against the process variation only. In the example, the GR&R% is 26.7% of the total variation. This report shows which section of the measurement system may need improvement, but it does not show how the system works within the actual tolerance of the parts. To evaluate the measurement system against the tolerance, one must use the total tolerance report.The TT ReportThe total tolerance (TT) report analyzes the gage study against the production tolerance of the part that the system is being evaluated to measure. While the categories are the same (EV%, AV%, GR&R% and PV%), the results are percentages of part tolerance. If the system is being evaluated for a particular purpose, then this report gives a true understanding of whether the measurement system is adequate.If the study is to determine if a measurement system is adequate for a specific purpose, then the results should be evaluated as a percentage of tolerance and the total tolerance report should be used.The Average and Mean ReportThe average and mean report includes not only the measurements and calculations, but also a graph charting the appraiser results. See Figure 2. This chart is useful in pinpointing appraiser training or method issues. Average and mean charts should not be read as a control chart. The data is plotted by sample number and not time sequence. Each chart plots the mean of each sample part and the range of each sample part by operator. In the example, one can tell that all operators have similar averages on all 10 however, the second operator, Justin Thom, has much more variation on each part. The next step here would be to determine if Justin is following the correct procedures or if he has been properly trained.Understanding how to properly conduct a gage R&R study and how to interpret the results is a key skill for quality professionals. For more detailed information, consult AIAG’s Measurement Systems Analysis, third edition, 2002, and Evaluating the Measurement Process, Wheeler and Lyday, 1984. Q
Tech TipsHere are a few guidelines for the measuring process:
The operators should share one calibrated gage or measurement system.
Five or more samples that represent the range of the process variation should be used. Do not use one part or parts that have little variation.
Samples should be measured in random order if possible.
At least two trials or measurements should be taken from each operator.
Quality OnlineFor more information on gage R&R, visit
to read the following:
Did you enjoy this article?
to subscribe to Quality Magazine.&
Recent Articles by
Rick Sloop is the senior application engineer at InfinityQS International Inc. (Chantilly, VA). For more information,& e-mail
or visit .
in order to post a comment.
Thank you for helping us to improve our forums. Is this comment offensive? Please tell us why.
Check out the May 2017 edition of Quality: Standard Gage or Custom?Minitab中测量系统分析(扩展)
GageR&R研究可以告诉你当前的测量系统测出的数据是否是真实可信的。遗憾的是，精确的数据要求和其它的限制条件让测量系统分析变得分析起来十分复杂，也可能对一些重要因子无法解释，Minitab中的Gage
R&R（扩展）工具让这些障碍成为过去。
R&R研究能告诉我们什么
测量系统是否有足够的灵敏度？
你的测量工具是否稳定的？
是否选用了一致的测量系统？
(扩展)提供什么额外的功能？
分析除了部件和操作员外，可以分析的因子增加到8个
可以分析不完全数据（不平衡设计）
因子类型包括固定的和随机的，更具灵活性
包含两个以上因子的Gage
&&传统的来说，Gage
R&R分析只关注两个因子：部件和测量人员，但是如果你还想知道是否有其它因子会影响测量系统呢？如果你不包含这些因子，你将永远不知道它们对测量系统变异的影响程度，你的测量系统看起来比实际情况更好或更糟，Minitab中Gage
R&R(扩展)中最多将因子增加到8个，所以你可以研究和评估可能对你测量系统有重要影响的因子。
因为他们在高温的产品线上，研究者关注调节生产速度会影响测量结果，增加速度为一个因子到测量系统的研究中，了解更改速度是否会影响测量结果而不是怀疑。
对不完整的或非平衡数据执行测量系统分析
&&传统测量系统分析要求严格的“平衡”设计，虽然在实际数据收集中经常不是这样完美，可能通常并不需要测量人员对每个部件测量相同的次数，也可能有些数据丢失，测量系统分析（扩展）允许分析此类数据，甚至是不平衡的结构，不需要手工计算或预处理缺失数据。
比如：&&&&
在完成测量系统分析后，研究者意识到测量系统丢失一些内容，而测量系统不能简单被重新操作因为这些产品已经被运输了，研究者利用测量系统分析（扩展）来处理这些不平衡的数据而不是把这些部件的数据从当前表格中移除。
更灵活：包括固定和随机因子
& & 在测量系统分析中，如果你特意选择一些感兴趣的类型（像最有经验或最没有经验的操作员），这样的话因子就是固定的，如果你随机选择水平来代表整体的情况，因子就是随机的，典型的测量系统分析结果默认因子是随机的，但是把固定因子当作随机因子可能导致减弱或增强因子的重要程度。GageR&R
(扩展)允许你指定哪些因子是固定的，哪些是随机的，更精确的分析测量系统。
审计结果上看超出公差限的部件主要问题可以追溯到测量设备的精度，进一步了解是两个测量人员的原因，为了更好的了解该问题，质量经理打算主要针对这两个测量人员安排一测量系统。因为人员是经过筛选的而不是随机选取的，经理需要指定该因子是固定的来分析。
已投稿到：
以上网友发言只代表其个人观点，不代表新浪网的观点或立场。你的浏览器禁用了JavaScript, 请开启后刷新浏览器获得更好的体验!
请问，对检查测量的设备，都会定期进行校正，但顾客方提出还要进行Gage R&R，请问各位DX，
两者的区分是什么？又如何进行Gage R&R？特别是一些破坏性试验的设备又如何进行？
如果是检测功能/性能的设备，则用交叉分析法（计数型）去分析，判定准则是：利用kappa值大于75%以确定一致性；破坏性的设备可用双性分析，方法是：三个人在很短的时间分别对30个零件的质量特性进行测量（各一次），得到30个数据，进行分析；判定准则是：R&R值小于50%则可接收。
9 个回复，游客无法查看回复，更多功能请或
扫一扫微信订阅
浏览: 1877
关注: 0 人
6SQ质量日刊
服务号: Lsqdnet
6SQ质量周刊GR&R_中文培训-海文库
全站搜索：
您现在的位置：&>&&>&物理
GR&R_中文培训
Gage R&R1Gauge Repeatability & Reproducibility TrainingCFMA Q1&Export STA 王明阳Gage R&R2课程内容安排一：MSA(测量系统分析)简介 二：GR&R 三：GR&R示例,使用Minitab作GR&R分析 四：II.5.量具校准和使用(Manufacture Site Assessment)Gage R&R3课程目标到本课程结束时，学员应能：? ? ? ?知道为什么要做测量系统分析 理解GR&R 了解使用Minitab作GR&R. 理解Q1-MSA II.5的要求Gage R&R4一：MSA介绍Gage R&R5测量系统分析的目的测量系统分析的目的是什么？●测量系统分析的目的是确定所使用的数据是否可靠 测量系统分析还可以： C评估新的测量仪器 C将两种不同的测量方法进行比较 C对可能存在问题的测量方法进行评估 C确定并解决测量系统误差问题●Gage R&R61:测量系统用来对被测量特性定量测量或定性评价的仪器或量具、 标准、操作、方法、夹具、软件、人员、环境及假设的 集合；●●用来获得测量结果的整个过程。Gage R&R72: 测量数据的质量数据的类型 C计量型数据 C计数型数据 如何评定数据的质量 C测量结果与“真值”的差越小越好(bias) C用多次测量的统计结果来进行评定(variance)Gage R&R8计量型数据的质量 C均值与真值（基准值）之差 C方差的大小 计数型数据的质量 C对产品特性产生错误分级的概率低质量数据最普遍的原因之一就是变差太大，变差一般都是 由于测量系统及其环境相互作造成的。Gage R&R93:测量结果-数据的用途测量数据通常有那些用途？●用于判断产品是否合格.●用于分析生产过程。●用于确定两个或多个变量之间是否有显著关系Gage R&R104:测量过程测量：给具体事务赋以数值，以表示它们之间关于特 定特性的关系。 ● 赋值过程定义为测量过程，而赋予的值定义为测量值。●测量结果由一个数字和一个标准的测量单位构成。测量结果是测量过程的输出。应将测量看成一个制造过程，它产生数据作为输出。人 设备 材料 方法 环境测量 过程数据输入输出Gage R&R115:测量过程变差源测量过程中的变差源有那些？S I标准 仪器W 工件(如,零件) P 人/程序 E 环境S W I P EGage R&R用来对被测量特性定量测量或定性评价的仪器或量具、 标准、操作、方法、夹具、软件、人员、环境。12Gage R&R136:测量系统变差类型根据变差的来源和特点，可分为:●位置变差(准确度)：偏倚，稳定性和线性；●宽度变差(精确度)：重复性和再现性。Gage R&R偏倚（BIAS）参考值 测量结果的平均值与参考 值的差异 参考值是一个预先认定的 参考标准. 该标准可用更 高一级
上一篇： 下一篇：
All rights reserved Powered by
copyright &copyright 。文档资料库内容来自网络，如有侵犯请联系客服。}