Significance of Metrology with Respect to Engineering - Book Report/Review Example

Metrology Significance of Metrology with respect to Engineering Metrology is generally termed as the science behind measurement and measuring techniques. It has become a fundamental part of different measuring and manufacturing industries. Let us take an example of a manufacturing industry and see how metrology plays its role. In a manufacturing industry precision and accuracy is extremely important. In a manufacturing industry metrology is applied on two scenarios, one being the post process measurement and the other on process measurement (Majcen and Taylor, 2010). Post process measurements are done in order to check for the accuracy of the manufactured product that is to check whether the product lies within the tolerance limit. If not, then it has to be re-examined so that accurate results are obtained. Among the post process measurement different measurement techniques and instruments are used. Usually block gauge, micrometer, profile projector and coordinate measurement machines are used for post measurement techniques. A block gauge consists of different sizes of lengths, holes, depressions, diameters, rectangle cross sections of perfect measurement. So a parts length or shape could be determined by comparing with a block gauge. Micrometers are also used in the post process measurement, they measure the outside and the inside diameters as well as thickness of the product. Profile projectors are used in a manner to project the part magnified on a screen, the reading on the screen will define parts dimensions. It gives a two dimensional image. Accordingly then process could be carried as whether it lies within the tolerance limit. A CMM is also used for the same purpose but being a modern machine it gives the results rather more quickly and accurately (Mainsah et al, 2001). The on process measurement consists of the direct and the indirect methods. Direct methods refer simply to measuring the part using simple instruments. Indirect methods refer to the measurement of a tool indirectly for example while radius measurement or notifying changes in the motion of the carriage, measurement could be made. The on process measurement league further expands to mechanical methods, optical methods, pneumatic methods and ultrasonic methods. The mechanical method also works on metrology and it is divided into three parts in a manufacturing industry. Caliper type, friction roller type and probe type are all types under mechanical methods used to measure parts and products in an ongoing process. Optical method uses the light pulse to measure. It is also one of the vital processes under a manufacturing industry and is divided further into scanning light beam and machine vision. Moreover pneumatic and ultrasonic methods are also used in measuring during an on process measurement process. Thus metrology forms an integrated part of a manufacturing industry (Kimothi, 2002). Standards and units form an important part of our lives. They have made our lives much easier and have a vital significance in the modern era for instance the units assists us compare quantities whether they be at a different space, time or place. Units aid us in categorizing physical quantities and measuring them. They further bring uniformity and universality to the scientific world. Moreover the use of same units across the sphere helps countries communicate and foster trade and business routines. Standard units further add significance as they have day to day use in everyone’s life for example distance covered by the car or the amount of petrol used etc all measured under standard units. Inspection is an organized method of evaluating different parts or products with a standard size or shape. It involves the measurement, examination and test of the product with respect to a certain standard or requirement ensuring that the certain target is achieved. It is categorized in the quality control area in an industry. It involves three processes; receiving inspection, in process inspection and final inspection. Whereas metrology is rather a science of measurement so it can rightly be said that inspection is basically an application of metrology. For instance physics and heat cannot be compared as heat is an application of physics in the same manner inspection is an application of metrology. The first principle alignment is used to keep the part or the product as close as possible and within the tolerance limit. During this the intermediate steps as well as any kind of indirect steps are avoided. The fundamental principle alignment works on a relative approach and an absolute approach is nullified here. Different companies such as” general electric” are working on at the first principle alignment. It is mainly aimed at displacement and length measurement though roundness and straightness could also be worked upon. It is a practice been carried on for ages now. A system that uses coordinates to determine the position of a point or geometrical figure is defined as Coordinate system. The coordinate system is divided into four main types; Cartesian coordinate system, polar coordinate system, cylindrical and spherical coordinate system and homogeneous coordinate system (Kimothi, 2002). In a Cartesian coordinate system each point is specified by a set of coordinates. These are defined by coordinates represented as (x, y). These coordinates are actually the distances from the perpendicular lines which are called as axis. In a two dimensional plane we are concerned with two points and hence two axis which are usually called as the x-axis (horizontal) and the y-axis (vertical). The point where the two axes intersect is called as the origin and represented as (0, 0). In cases when concerned with three dimensions the coordinates will be represented as (x, y, z) and there will be three axis as x-axis, y-axis and the z-axis. A polar coordinate system is a two dimensional coordinate system. Here other than the distance from a fixed point an angle from a fixed direction is also determined. The fixed point in a Cartesian coordinate system is termed as origin as defined earlier whereas in polar coordinate system it is named as pole. The distance from the pole is called as the radius and the angle is called as the polar angle. The axes are known as polar axis (Mainsah et al, 2001). Cylindrical and spherical coordinate system is a three dimensional coordinate system. The coordinates are defined by three points. The three points are the radial distance which is the distance from the pole, polar angle measured from a fixed zenith direction and the azimuth angle. Azimuth angle is the angle on a plane which passes through the origin (pole) and is orthogonal to the zenith. The polar angle in this type of coordinate system is also referred as zenith angle. The cylindrical and spherical coordinate system prefers using radians rather degrees to measure the azimuth angle. Homogeneous coordinate system is a four dimensional coordinate system. Its coordinates are represented as (x, y, z, w) and is usually used in computer graphic systems. It further allows the use of a 4 x 4 matrix to represent 3-dimensional transformations. Its main purpose is to cover infinity. Here only the ratios of the coordinates are vital and it does this so by not using infinity (Mainsah et al, 2001). Among the metrology tools comes the micrometer screw gauge which is used for very fine precise measurements. The degree of error is very less as it measures close to 0.01mm. The basic types or the common types of a micrometer are outside micrometer, inside micrometer and depth micrometer. There are also some specialized or modern types of micrometers. A gauge block is used to compare standards. Parts and products are matched with the gauge block and compared their diameters and lengths as a gauge block provides with an accurate measurement up to 0.05 micro meters. An electronic digital calliper offers easy reading as it uses an electronic screen to represent the measurement digitally. They are made of stainless steel and have an accuracy of 0.001 in or 0.02mm and a resolution of 0.0005in or 0.01mm. Vernier callipers are the primitive form of electronic digital callipers though they are still very much popular. They measure to the nearest 0.01mm and could be used both for measuring inner diameter or length and outer diameter or length. A combination square set is used for multiple purposes. It is used to check for right angles, to measure the length of a material, to measure the angle, spirit level to ensure whether a job is vertical and moreover could also be used to measure diameters. The rule used measures to the nearest millimetre whereas the protractor to the nearest angle. The calliper is similar to that used in Vernier calliper so it measures to the nearest 0.01mm. One of the pictures is of CMM calibration cap. A CMM is a 3D device and it measures using a probe. It could be manually operated but it is usually computer controlled and that is why it has a very high accuracy. It takes readings in six degrees and displays the result in mathematical form. It has a resolution to about 0.000020in or 0.5 micro meters. Metrology has aroused as one of the basics of the modern sciences and it has an imperative effect on our lives. References Kimothi, S. K. (2002). The Uncertainty of Measurements: Physical and Chemical Metrology: Impact and Analysis, London: ASQ Quality Press Majcen N., Taylor P. (2010). Practical examples on traceability, measurement uncertainty and validation in chemistry, Vol 1. UK: EU Book Shop. Mainsah, E., Greenwood, J. and Chetwynd, D. (2001). Metrology and Properties of Engineering Surfaces. NY: Springer Read More