Metrology & Statistical Quality Control 5 th Term, Batch: /01/20111Lec:1 & 2

Recommended Books: 1.Metrology & Gauging By: S.A.J. Parson……..any latest edition 2.Engineering Metrology & Instrumentation By: R.K. Rajput 2.Metrology for Engineers By: J.F.W. Galyer & C.R. Shotbolt……any latest edition. 3.Practical Metrology By: G.H. Sharp……..any latest edition 4.Quality Control By: D.H. Besterfield, Pearson Edition. 5. Introduction to Statistical Quality Control By: Douglas C. Montgomery. 20/01/2011Lec:1 & 22

Course Objectives & Scope Objectives: The course exposes the students to the principles of measurement, gauges and modern quality concepts and their practical use. This will also refresh the basic statistical & probability techniques and their usages in quality application. 20/01/2011Lec:1 & 23

Course Objectives & Scope (Cont..) Scope: At completion of degree with the course of Metrology and Statistical Quality Control, students find confidence for applying the jobs in testing, inspection and quality control. 20/01/2011Lec:1 & 24

Introduction Definition of Metrology: - Metrology in literal sense, means the pure science of measurements. But for engineering purpose it is restricted to measurement of length and angles & other quantities which are expected in linear or angular terms 20/01/2011Lec:1 & 25

Introduction (Cont..) In metrology we are primarily concerned with methods of measurement based on agreed units & standards Practice of metrology involves precise measurement requiring the use of apparatus & equipments to permit the degree of accuracy 20/01/2011Lec:1 & 26

Introduction (Cont..) In broader sense, metrology is not limited to length measurement but is also concerned with the industrial inspection & its various techniques. Inspection is carried out with the gauges & the metrologist is initially concerned with the design, manufacture & testing of gauges of all types 20/01/2011Lec:1 & 27

Objectives of Metrology 1.Complete evaluation of newly developed products 2. determination of the process capabilities & ensure that these are better than the relevant component tolerances 3.Determination of the measuring instruments capabilities & ensure that they are quite sufficient for their respective measurement 20/01/2011Lec:1 & 28

Objectives of Metrology (cont..) 4.Minimizing the cost of inspection by effective & efficient use of available facilities 5. Reducing the cost of rejection & rework through application of statistical quality control techniques 6. To standardize the measurement methods 7. To maintain the accuracies of measurement 8. To prepare designs for all gauges & special inspection fixtures 20/01/2011Lec:1 & 29

Measuring & Gauging When manufacturing large quantities of work pieces on basis of interchangeability, for instance, a considerable amount of time could be wasted if actual measuring were carried out. Instead that gauging should be substituted Eg: gauges in the form of limit gauges, are used for determining whether or not a particular feature, such as mating diameter, is, or is not within the dimensional magnitude stated on the drawing 20/01/2011Lec:1 & 210

Measuring & Gauging (cont..) Features of working parts are never made exactly to size. Invariably, they have a manufacturing tolerance, permitting the feature to be dimensionally correct, even though the sizes vary. This variation must not exceeds the tolerance provided Gauging there fore differs from measurement, since the latter aims at determining the size of a particular feature, whilst gauging merely determine the dimensional accuracy of a feature, without reference to its actual size 20/01/2011Lec:1 & 211

Measuring & Gauging (cont..) Common types of Gauges: 1.Master Gauge: From the Mfg point of view, is an ultimate reference controlling the size of components which are being produced. Such a gauge would only be available for comparing, & transferring its size to a reference gauge, & it would be solely used by the standards room 20/01/2011Lec:1 & 212

Measuring & Gauging (cont..) Common types of Gauges: (cont..) 2.Reference Gauge: As name implies is used for reference in the control of working gauges (both workshop & inspection), & it may be used for components 3. Working Gauges: Such gauges are made and dimensionally controlled through the use of reference gauges, which in turn, are checked by means of Master gauges, & the later are related to fundamental standards 20/01/2011Lec:1 & 213

Precision Measurement –Its Need While manufacturing accurate size of components/products it is essential that the accuracy required should be built into the machine tools, jigs & fixtures which produce them Precision measurement is concerned with the precise determination of linear, angular, & non linear functions of the machine surfaces of the tools & devices used to produce engineering components 20/01/2011Lec:1 & 214

Precision Measurement –Its Need (cont..) It has been observed that precision measurements are always required in the manufacture of press tools, & much the same can be said for the manufacture of machine tools such as lathes, milling machines & drilling machines Dimensional & Geometric accuracy of the components produced using the above machine tools is proportional to the inherent accuracy built into the machine tool & thus the operator is able to produce which is accurate 20/01/2011Lec:1 & 215

Standards of Measurement For the Linear measurement the various standards are known as: 1.Line standard 2. End Standard 3. Wave length Standard /01/2011Lec:1 & 216

Standards of Measurement (cont..) 1.Line standard: a yard or metre is defined as the distance b/w scribed lines on a bar of metal under certain conditions of temperature & support. These are the legal lined standard a. The Metre is defined as wave lengths of the orange radiation in vaccum of Krypton-86 isotope b. The Yard is defined as metre. This is equivalent to wave lengths of the same radiation 20/01/2011Lec:1 & 217

Standards of Measurement (cont..) 2. End Standard: End standards are developed into two basic forms; a) Small block (slip) gauges: i.e, up to 5 inch used for relativey short lengths. Invariably their ends are flat b) Length bars: for large (i.e more than 5 in) lengths these are the bars of circular crossection, the ends of such can be flat or spherical 20/01/2011Lec:1 & 218