 Hello everybody and welcome to this course on metrology. Before I formally start telling you about metrology, I would like to introduce myself. I am Sadash Bapa, working as a professor in Babuji Institute of Engineering and Technology, Dhawan Giren. Metrology is the science of measurement, which mainly deals with measurement of size, form, and positions. In general, for any kind of quantity to be measured, there must be a unit of measurement and it should be possible to express the quantity in numbers. Hence, metrology is concerned with the establishment of units of measurements and their standards. It is concerned with establishing methods of measurement and it also deals with different kinds of measuring instruments. In a broader sense, it is concerned with industrial inspection. It deals with inspection of raw materials to inspection of finished components with the help of standard measuring tools and gauges. Metrology is used in many areas such as machine tool, building, automobile engineering, biomedical engineering, space applications, building science, marine science, and many other scientific and engineering fields. In the present course, we will be mainly dealing with the dimensional metrology wherein we will be learning about precise measurement of lengths, angles, forms, and positions. This course is spread across 44 lectures arranged in the 12 modules. We will be learning about basic definitions and terminologies related to metrology, different measurement standards, units, methods of measurements, errors in measurements, and calibration aspects in module number one, that is introduction to metrology. And in module number two, we will be dealing with usage of different measuring instruments such as one-year caliber, micrometer, angle measuring devices. In module three, we will be discussing about limits, fits, and tolerances. What is the need of tolerance? What are the different kinds of fits available? How to select a proper fit for a given application? Such things we will be discussing in module number three. And in module number four, we will discuss about the measurement of geometrical features. Mainly, we will be discussing about straightness measurement and squareness measurement. And then we will move on to measurement of surface finish and screw thread element measurements, gear element measurements, tapered measurement, and radius measurement. And in module number nine, we will be discussing about use of interferometry for measurement of flatness of precise surfaces. We will be discussing about construction and application of different interferometers available. And in module number ten, we will discuss about different types of comparators and their use in dimensional metrology. In module number eleven, we will be discussing about different alignment tests conducted on lathe and drilling machines. Finally, we will move to advanced metrology, wherein we will be discussing about universal measuring machines, coordinate measuring machines, in process gauging, stage position metrology, nanotechnology, instrumentation such as atomic force microscopy. And finally, we will discuss about optical system designing. I wish you happy learning through this course. Thank you. Now, let us start the first lecture of the series. Now, let us understand what is the meaning of the measurement. Let us have a look at our daily activities like buying things like grocery, gold, petrol and cloth, measuring emission level of vehicles, inspecting workpieces produced in a shift, drug delivery to a patient, measuring blood pressure, body weight, body temperature, etc. In all these activities, we are trying to measure a physical quantity like pressure, volume, length, etc. Now, let us take a simple example of buying things like cloth. And let us understand the measurement process in detail. When we go to a cloth shop and ask for a certain length of material, immediately the shopkeeper will take the material and he will take a measuring tape and he measures the cloth of the required length and cuts it and gives it. Now, in this process, we can understand that in the process of measurement, a physical quantity is required for which we had to give the value. And then we require a standard or a reference for measurement process. And then there is a comparison process. That means the shopkeeper will open the cloth, he will spread the cloth on a table and then the length of the cloth that is to be cut is the physical quantity. And then the shopkeeper takes the measuring tape and this is the reference for us to measure the length. And then he compares the cloth length with the measuring tape. This is the process of comparison. That means in any measurement process, we have three entities. First one is the physical quantity in our example length and then a reference for measurement that is measuring scale and then process of comparison. That means comparing length of cloth with the measuring tape. So, that is the third entity. Now, let us look at this simple picture and try to understand the measurement process in detail. So, we have the datum on which the measurement process takes place and then we have work piece. The length of the work piece is to be measured and then we have a butt plate against which the work piece is pressed. And then we need a reference for example a steel rule or a measuring tape. And again the steel rule is placed on the work piece and it is pressed again as the butt plate. Now, we start measuring the length of the work piece from this point, from this edge of the work piece. So, this is the reference point and then we look for the coinciding division on the steel rule, which division on the steel rule is coinciding with the other edge. So, this becomes the measurement point. The difference between the reference point and the measurement point is the length of the work piece. That is the physical quantity that is to be measured. If the measurement process is very simple like measuring the length of a work piece or a diameter of work piece, using the micrometer we can do that, we can just hold micrometer in our hand and we can take the work piece in our other hand and then we can measure. So, in this case datum is not required. So, in some cases datum will be required, in some cases datum will not be required. Now, let us try to understand the importance of measurement process. So, I gave some examples of our daily activities wherein measurement is carried out in all activities. That means measurement is everywhere and it is playing a vital role in our lives. Now, measurement is very essential to ensure safety and effectiveness of health care diagnosis and treatment. We measure many parameters when we go to a hospital like blood pressure measurement, blood composition measurement etc. etc. The measurement that is carried out should be accurate and it should be precise, so that proper treatment can be given to the patient. Then when we take the example of manufacturing industry, we measure the composition of material. We look for maybe carbon percentage in steel and other alloying element composition. So, if the measurement of these composition is proper, then we can build good products. Then to ensure safe operation of vehicles and machine tools, we measure parameters like speed of the vehicle or machine tool. What is the feed rate of various slides of the machine tool? What is the vibration level of machine tools or vehicle? Whether the machine tools and vehicles are under safe condition, safe running condition. So, to ensure that measurement is very essential. Also, to ensure proper food supply, whether any dangerous substances are included in the food supply. To ensure that we need to measure the food that is supplied. Then to ensure consistency of time standards, so that we can have comfortable communication between two different places or two different countries. To ensure fairness between buyer and seller, measurement is very important. We gave the example of buying a cloth. The seller takes a measuring tape and he measures and he gives the cloth. Now the buyer also can take another scale and he can cross check whether the length that is supplied is correct or not. That means both the scales used by buyer and seller should be comparable. That means they should be comparable to some national or international standards, so that there will not be any dispute between buyer and seller. Now to evaluate newly developed products and processes, we need to conduct measurement. After the completion of the assembly, we have to check what is the performance level with respect to the cutting parameters or the vibration level or the health of the machine tool. We need to conduct many kinds of measurements. To get accurate and precise data in scientific research, we should have measurement process. Now let us move to understand the definition of the metrology. It is the science of measurement and there are national metrology institutes around the world to make sure that the measurement we use are fit for the purpose. Now metrology has three basic activities. The first one is defining the internationally accepted units of measurement. For example, length, time, etc. Then realization of the units of measurement in practice. For example, we have defined the length. Now how to realize it so that we can use it for the commercial purpose or for the benefit of the society and then establishing traceability linking measurements made in practice to reference standard. That means whatever instruments we make should be comparable to the national and international standards. Now metrology has the following three basic subfields. Scientific or fundamental metrology applied technical or industrial metrology and the third one is legal metrology. Now let us understand these three subfields. The first one is scientific or fundamental metrology. So this deals with the establishment of quantity systems, unit systems, units of measurement, the development of new measurement methods, realization of measurement standards and transfer of traceability from these standards to users in society. In India, National Physical Laboratory is the custodian of various primary standards. Now we can see this photograph which is concerned with thermal imaging metrology for health care. A lot of research work is going on in the thermal imaging which is used to detect cancer in earlier stages or the fever scanning or the healing process in the body. So such research activities and establishing corresponding measurement methods and measurement standards is the activity which is carried out in scientific metrology. What kind of measuring instruments should be used for such newly developed methods? What kind of environment should be provided? Whether any specific conditions are there with regard to temperature, humidity pressure or in the vibration proof datum surfaces are needed and how to conduct the measurements? What are the guidelines for conducting the measurement process? How to report the measurement results? These are some of the activities which come under scientific metrology. Now we will move to applied technical or industrial metrology. It deals with the application of measurement science to manufacturing processes and their use in the society. It ensures the suitability of the measurement instruments selected and their calibration and quality control of the products. So in this area, emphasis is given on the measurement themselves and traceability of the calibration of the measuring devices to ensure confidence in the measurements. We can take the example of this drawing and we will try to understand more about industrial metrology. I can see in this figure, we have various parameters to be measured like diameter of the component. There are three holes of different diameter. There is one bigger hole at the centre and then we have depth that is to be measured. Resus is there for which we have to measure. The depth of the research, resus or width of the resus we have to measure and various lengths we have to measure and there is a threaded portion here. We need to measure the thread elements like pitch of the thread, flank angle, measured diameter, minor diameter etc etc. Now to measure all these parameters, we need to select appropriate instruments. Sometimes we may require the measurement of parallelism between two surfaces and then perpendicularity between two surfaces and then what is the form of the drilled hole whether there is any taper or whether it is bell shaped or drum shaped or whether any out of roundness is there. Such parameters we need to measure for which appropriate selection of instrument is necessary. So industrial metrology helps in all these activities. Sometimes we may have to measure inspection. We have to make inspection fixtures so that the inspection can be carried out easily. So all such things are carried out in industrial metrology. Now we will move to legal metrology which deals with the activities which result from statutory requirements. It is concerned with legal requirements of measurement processes, units of measurement, measuring instruments and methods of measurement to establish necessary rules and regulations on qualities and control of measuring instruments and their use. Now statutory requirements might arise from the needs of protection of health, public safety, the environment, enabling taxation, protection of consumers and to establish fair trade. This helps in detecting frauds in measurement and to book offender for trials wherever necessary. Now let us try to understand the forensic metrology which is a part of legal metrology. This applies to forensic sciences, forensic laboratories perform numerous measurements and tests to support both criminal and civil legal actions. The examples of forensic metrology activities are given below the measurement of blood or breath alcohol content, the quantification of controlled substances both for net weight and purity. For example, what is the purity of gold? So that can be checked in forensic metrology. Then length measurements of firearm barrels. So I can see here in this picture we have a firearm barrel. The length of the barrel we need to check, the diameter of the barrel, the surface finish, the various the form of the barrel we need to check. And then latent print examination, for example, fingerprint examination, question document examination like to check whether there is any forgery of signature and DNA analysis to establish biological relationships. Then 3D laser scanning of crime scene can be taken so that it can be visited again and again to study the crime scene. Now the results of forensic measurements are used to determine if a person is charged with a crime or may be used to determine a statutory sentencing enhancement. Now there is recently there is a another kind of metrology which is evolved because of the advancement in nanotechnology area. Now we need to measure nanoholes in the nanostructured particles for which we have to design and develop nanoprobes which can enter into nanoholes to measure diameter, distance between the two holes etc. Nanoparticle characterization like what is the shape of the nanoparticle, what is the size of the particle, what is the pace between two particles, such things we need to measure to characterize the newly developed composite materials, nanocomposite materials. Then in the last few decades various measurement methods have been developed for the characterization of nanomaterials like nanocm is developed which physically measures the MEMS products and nanoproducts and then scanning electron microscopy, X-ray diffraction, tunneling electron microscopy, atomic force microscopy, all these are developed which will aid the characterization of nanoparticles, nanodevisors etc. And then recently laser based systems are developed which aid in inspection of nanodevisors and there is a need to establish nanometrology standards so that in all parts of the world same standards can be used and the measurements that is carried out in the nanometrology will be comparable and usable throughout the world. Now let us try to understand what is the role of metrology in the innovation. Now the manufacturing industries always try to develop new kinds of methods, new kinds of products and then manufacturing of precision engineering components which are used in aircrafts and spacecrafts have very very tight specifications. So we need to design and develop new methods of metrological methods and new kinds of metrological instruments which will be able to measure the tight specifications. Now if you study this diagram we will come to know that whenever there is a new idea generated a lot of R&D work will be carried out on that new idea that is generated and computer aided design and analysis will be carried out on that particular idea to develop various models and to prepare the drawings. Once the drawings are created there we move for computer aided manufacturing where we manufacture the components as per the computer aided drawing that is provided using different kinds of inputs. Now if the components are new type of components having very complicated structures or profiles we have to develop new methods of measurement, new instruments for measuring that complex profile so we should have innovative metrology we should invent new kinds of instruments in we should invent new kinds of fixtures inspection fixtures so that measurement becomes or inspection of the component becomes fast and accurate. Now the metrology is also applied in the assembly and testing of the new products that is developed finally the components and products are packed and dispatched. Now let us try to understand what are the various objectives of metrology. Metrological instruments are used in various sections of a manufacturing organization they are used in tool room, used in machine shop, foundry shop, standards room, press shop, electroplating shop, paint shop at all places the metrological instruments are used in such a big organization the metrology will have many objectives we will study some of the objectives to determine the type of measuring instrument needed by the plant and to ensure that they are well maintained in the plant by periodical calibration depending upon the type of activities going on in the shop they have to suggest the quality control department will have to suggest what type of instrument is required whether in process gauging is required or off process gauging is required what should be the range of the instrument what should be the accuracy level of the instrument and then any special type of equipments are needed for example I will write a sketch here say we have a component which has an internal groove like this I am just writing the sketch so there is a workpiece with internal groove like this then the quality control department should suggest appropriate instrument so this so in the places like this one can use an inside micrometer caliper of this type and also sometimes we may be having some workpieces having some boards like this which are very deep then the quality control department will have to suggest some gauges or inspecting measuring instruments so that the depth of the groove can be measured or the diameter of the groove can be measured or sometimes surface finish of that groove can be measured in that case you may have to use some long probes like this so the quality control department will suggest appropriate measuring instruments needed by the plant and also it ensures that say every instrument will undergo some sort of wear wear and tear due to continuous usage at regular intervals we need to inspect all those instruments to check for whether there is any wear if there is any wear they should be compared with the accurate instrumentation available in the standards room and the amount of error that is there in the instrument should be recorded on the instrument so when we take the readings using such calibrated instruments we should account for the error that is mentioned on the instrument and then the quality control department will have to see what is the process capabilities of newly developed process whether the new process developed are really capable of doing what is expected or whether they are going out of the process or what kinds of changes are necessary so that the process capability increases now another objective of the metrology is standardization of measuring methods used with reference to the prevailing standards that means whenever new products are developed we need to measure we need to develop new methods of measurement and then what are the prevailing standards we should consult and then we should suggest the measuring instruments that means we should standardize the various kinds of methods as per the prevailing standard and then metrology department have to provide proper solution to the measuring problem arising in the shaft floor sometimes the operator will ask for suggestions how to check the particular parameter is unaware of using the instrument and some sort of training is to be provided to the new operators so quality control department will teach them how to use the instruments and how to come out of the problem that arise in the workshops and sometimes very complicated components like rotor blade will have to be inspected so in such cases we need to devise special inspection features one such example is shown here we have the rotor blade which is having very complex shape so we need to design and fabricate a holding device for holding the rotor blade and then we have indicator to measure the various parameters of the rotor blade and then application of statistical quality control techniques to the various processors to study whether the processors are under control or not we can see this diagram wherein we have upper control limit lower control limit and x axis time and y axis is variable and we have various measuring points and then the center line indicates the average of variable size now the measurement points are scattered well within the upper control limit and lower control limit this indicates that the process is under control whenever a measuring point goes beyond the upper control limit or beyond the lower control limit then necessary actions should be taken so that the process is brought back under control the action necessary action may be in the form of changing the machine setup or changing the computer programs etc now let us try to understand what is the need of measurement or inspection now let us try to understand what is the difference between measurement and inspection so in the manufacturing area we need to produce various kinds of components having various types of features like depth length breadth surface finish palism etc etc now all these features we have to measure and we have to quantify them so such a process is called measurement sometimes we have to inspect the workpieces to just accept or reject whether the workpiece is okay or not only that information is required and no need of us measuring the physical variable so such a such an activity is known as inspection in the industrial sense both the terminologies are used identically now to ensure that the products supplied to the customer are within the agreed specification so whenever a customer gives order he will give what are the various specifications of the product what type of activity is required what is the size what is the weight what functions are needed expected out of the products all those things he will explain now before we supply the product to the customer we should compare what are the specifications of the customer and what is that we are supplying if they match then only we should supply the product to the customer now inspection is also needed to monitor the process performance this will ensure that the number of rejects is as small as is economically practical that means the whenever the process goes beyond the control now we may have to do some changes in the process so that it is brought back to the control now to ensure that the raw materials purchased parts and components conform to the purchasers specification the manufacturing industries place order for various kinds of raw materials for example steel aluminum etc of different length and different shape they also place order for purchase parts like fasteners electric motors etc etc and some components now before we accept the components or the raw materials are purchased parts we should check whether they are as per our specifications then only we should accept them so that defective parts will not move to the assembly area or the manufacturing area now there is a concept called interchangeability the mating parts are made at different places and different countries due to the mass production concept and all these mating parts when randomly selected and when we match them they should fit properly without any individual fitting operation this is known as interchangeability so to achieve interchangeability it is very essential that we produce the various components and parts as per the standard using standard instrumentation and to evaluate the possibility of rework of defective parts now the inspector has rejected some parts now we have to really check whether the some rework can be performed so that they can be accepted again so for that we need to inspect defective parts and to exclude sources of error deficiencies in the process we need to conduct the measurement process sometimes we go for limit gauging to establish limit gauging we need to inspect sometimes in the manufacturing area what happens is we need not have to actually measure the size of the variable for example the diameter of the bore or length of the bore or the depth like that what is needed is whether they are within the acceptable limit or not so actual measurement is not required so such a system is called limit gauging to establish limit gauging also we need to conduct inspection so this is this indicates that there is a need for inspection to establish limit gauging now to achieve reverse engineering also measurement is very very essential sometimes we have the part but corresponding drawings are not available in that case we have to inspect the component that is available for its composition for its the physical sizes like length depth breadth the size of the hole or the surface finish that is prevailing etc all these things we have to measure by conducting the inspection and then we have to prepare the drawing and then we can go for producing such components now to augment the reputation of the manufacturer and to help him to become what last manufacturer measurement is very very essential we need to conduct measurement may be 100% inspection if the components are critical or batch type of inspection and we have to eliminate remove all the defective parts and only good components should be good products should be supplied to the customer so that the customer will be happy and we get repeated orders from the customer now let us try to understand the classification of inspection how the inspection procedures are classified so one type of classification is depending upon the labor that is involved that is manual inspection visual inspection automatic inspection in manual inspection what happens is the operator will take the workpiece that is to be inspected you will take the appropriate measuring instrument and you will check the parameter for example length or diameter of hole or surface finish so the this is called the manual inspection so this process sometimes becomes very slow and it is subjected to the effects of fatigue of the operator and in the visual inspection no instruments are used the workpieces are inspected by the operator for any defects like the presence of burrs or so presence of any cracks blow holes etc etc no instrumentation is used at the most the operator may use a magnifying lens the third type of inspection is automatic inspection so this can be contact type inspection or non-contact type inspection so in this process the intervention of the operator is not there after the production of the component it is cleaned and then it is placed on the measuring machine for example a coordinate measuring machine wherein the probe will touch the various parts of the component and the various physical quantities are measured in non-contact type light based measurement systems are used and the various parameters like surface finish diameter of the component etc are measured without any contact with the workpiece so this non-contact type automatic inspection can be used during the process it's in process gauging is also possible now the second type of classification is based upon the area of inspection where the inspection is carried out so we have different types like receiving inspection first-piece inspection process inspection batch inspection final inspection and tool and gauge inspection now the receiving inspection is the manufacturing industry places order for various raw materials and parts so when we receive them we have to inspect them for all the physical parameters the composition etc etc so this is known as receiving inspection if there are any defective parts supplied by the supplier we have to reject them so that defective components will not move into manufacturing and assembly area then cat to part analysis or first-piece inspection now based upon the cat that is provided we produce the first piece and now we have to use the different kinds of instruments to measure the various kinds of physical parameters to check whether all the parameters are as per the CAD drawing if there are any errors we need to make some changes in the CAD and again we have to produce the piece and again we have to adopt the first-piece inspection till we get the first piece which is acceptable and then we can start the mass production of that component now the process inspection is during the process itself we can conduct the inspection for example I gave the example of non-contact inspection of inspection process wherein the parts are inspected during the machining process we can take the example of a grinding process so whenever the grinding process is going on without stopping the grinding machine we can use a laser light laser light will fall on the workpiece and when the workpiece achieves attains the correct size the light that is reflected amount of light that is reflected is sensed and then proper instruction are given to the machine tool for stoppage of the machine tool and then we have batch inspection a batch of components are collected and they are based upon the formalities and then the decision is taken to accept the batch or not and in the final inspection once all the process are or processes are completed we need to and then when all the components are assembled to make the product final inspection we need to carry out to check whether painting is over or not whether all sub assemblies are properly assembled whether the movement of all parts moving parts is correct or not or whether there is any leakage or vibration levels are exceeding the limits so such things are inspected before we dispatch the product to the customer and then tool and gauge inspection all instruments are subjected to wear so at regular intervals we need to calibrate the instruments with the help of instruments available in the standards room and then we need to record what is the amount of error so when we use such instruments we have to account for the error that is mentioned on the gauges now let us conclude the first lecture now let me summarize the lecture in this lecture we tried to understand what is the measurement process and then what are the various objectives of methodology what is the need for measurement process what are the different kinds of inspection processes in the next lecture we will continue with the other basic concepts thank you