MSA

X1 = 0.75 X6 = 0.80 X2 = 0.75 X7 = 0.75 X3 = 0.80 X8 = 0.75 X4 = 0.80 X9 = 0.75 X5 = 0.65 X10 = 0.70 真实值True measurement = 0.80 公差Tolerance = 0.70 Compute for the bias and the % bias.
介绍Introduction :
我们想当然认为大量的检查和测试结果提供准确的尺寸,然而,计量和 测试产品的过程常常遭受到变差就像制造过程中常遭受到变差一 样…It is often assumed that the numerical results of inspections and tests provide an exact indication of the characteristic being measured. However, the process of gauging and testing products is subject to variation just as manufacturing processes are subject to variation…. 变差的来源是计量器具或测试设备本身,操作员和环境. Sources of variation are the gage or the test equipment itself, the operator, and the environment. 如果不了解测量变差,那么基于计量器具和测试数据上的决定可能是 不正确的. Unless this measurement variation is understood, decisions based on the gage and the test data may be incorrect.
偏倚 & 准确度Bias & Accuracy
如果偏倚过大,以下可能的原因:If accuracy is relatively large, it may indicate: • 标准或基准值误差 The master has an error • 工件磨损 The parts are worn-out • 制造的仪器尺寸不对 The gage is made to the wrong dimension • 仪器测量了错误的特性. The gage is not measuring the proper characteristic。 • 仪器校准不正确. Instrument not calibrated properly • 评价人员操作仪器不当. Instrument used improperly by appraiser
测量值 基准值
不准确或偏差
X T
偏倚 & 准确度Bias & Accuracy
Procedure程序: 1. 获得工件的可接受的参考值. Obtain an accepted reference value of the part. This can usually be done with tool room or layout inspection equipment. This measurement will be regarded to as the True value. 2. 一位评估者使用被校正过的测量仪器测量样品至少10次, Have one appraiser measure the sample part a minimum of 10 times, using the gage being evaluated. 3. 计算读数的平均值。Calculate the average of the readings. 4. 计算偏倚，参考值和观测值之间的差异。Calculate Bias, ie, the difference between the reference value and the observed average .
Aside: JMP
Procedure: 3.To add a row
1.You may do any of the following
• Select Rows > Add Rows. Then enter the number and location of rows you want to add. By default, new rows appear at the end of the table. • Click in a cell anywhere below the last row in a table and begin typing. Then press Enter (or Return) to automatically generate new rows up to and including the row with the value you typed. • Double-click an empty row number area below the last row to add that many empty rows.
议程Agenda :
• 介绍Introduction – 质量测量数据的重要 Importance of Quality Measurement data • 测量系统变差的类型: Type of Measurement System Variation: • 分析测量系统Analysis of the Measurement System – 测试程序Procedure of performing the test – 分析数据Analysis of data – 接受标准Acceptance Criteria • 运用 JMP 软件Application using JMP software
Aside: JMP
A New Data Table
Procedure: 1.Open the JMP file by clicking at the JMP button. 2.Create a new data table.
• Select File > New>Data Table. This displays an empty data table with no rows and one numeric column, labeled Column 1. • Move the cursor onto a cell. • Click the cell. The cursor becomes an Ibeam ( ), as shown in “A New Data Table”. • Enter a value.
多少偏倚是可以接受的? How much bias is acceptable? 如果误差小于这个等级仪器公差，这台测量仪器被认为是准确的。 a measuring equipment is considered accurate if the error is less than the tolerance for that grade of instrument 测量仪器应该有能力测量产品公差1/10或10% (单凭经验的方 法) 。The measurement equipment should have the ability to measure to 1/10 or 10% of the total product tolerance (rule of thumb) 测试仪器的公差是测量结果的2% (单凭经验的方法) 。In some test equipment the tolerance is about 2% of the measurement. (rule of thumb)
5 种测量系统的变差5 Types of Measurement System Variation
a) b) c) d) e) 偏倚 & 准确度 Bias & Accuracy 线性 Linearity 稳定性 Stability 重复性 Repeatability 再现性 Reproducibility
偏倚 & 准确度Bias & Accuracy
定义Definitions : 偏倚是指可接受的参考值与观测值 之间的不同。Bias is the difference between the average of a set of values and the true value of the characteristic being measured. - the distance X T is referred to as the error, bias or inaccuracy距离就是偏 倚，不准确度 - 不准确度或偏倚是测量仪器超出 范围的程度。This inaccuracy or bias is the extent to which the measuring instrument is out of calibration
Aside: JMP
Procedure: 3.To add a column (continued)
• You may do any of the following • Select Cols > Add Multiple Cols.
3.To add a column (continued)
• Double-click the upper triangular area in the upperleft corner of the data grid.
Measurement Systems Assessment
测量系统评估
11/22/05
目的Objective
• 认识测量系统的重要性和在产生数据过程中不可替代的 作用.Recognize the importance of the measurement system and its fundamental role in data generation • 量化来自测量系统的变差. Quantify variation from the measurement system • 评估测量系统是否可行.Assess if the measurement system is capable