 In this lecture, let us learn about inspection, testing and quality control. First let us learn about inspection and testing, then we will be learning about the quality control. Now this inspection and testing is carried out at the following stages. The first one is controlling the composition of the metal, I mean the molten metal which is poured into the metal cavity. Second one is the dimensional inspection. What are the dimensions? Are they as per the what say specifications of the customer? So that is the testing of the dimensional accuracy that is the dimensional inspection. Third one is the examination of surface quality and finish. Fourth one is the testing of mechanical properties of the casting and finally non-destructive testing. Internal sometimes there may be internal what say defects will be there internal cracks or blow holes and some other defects. So this will be what say detected using non-destructive testing. First we will see the controlling and composition of the metal. So this controlling and composition of the metal is done using spectroscopy. In the optical emission spectroscopy technique atoms in a sample are excited by energy that comes out to form a spark formed between the sample and the electrode. By measuring the intensity of the peaks in the spectrum the analyzers can produce qualitative and quantitative metal analysis. Next one let us see the dimensional inspection. Dimensional inspection again is carried out what say in two types one is manual inspection and the other one is the using coordinate measuring machine. There is no what say much to learn about the manual inspection. So let us see little about the coordinate measure machine. Using coordinating what say coordinate measuring machine a coordinate measure machine CMM is a device for measuring the physical geometrical characteristics of an object. This machine may be manually controlled by an operator and it may be computer controlled. It can be manual or computer controlled. Measurements are defined by a probe attached to the third moving axis of this machine. Now what about the probe? Probes may be mechanical, optical, laser or white light amongst the others. The machine takes readings in 6 degrees of freedom and displace them in mathematical form. So here we can see a typical coordinate measuring machine. So here we can see this is the probe and this is the component. So these components dimensions are being examined. Next one examination of surface quality and finish. This is carried out using a profilometer. A profilometer is a device used to measure the roughness of a surface. It gives the difference between the high and low point of a surface in nanometers. There are two types of profilometers. One is non-contact profilometer and the other one is the contact profilometer. Next one testing of mechanical properties of the cast component or the cast specimen. So these are the mechanical properties that are normally measured strength, ductility, hardness, impact resistance, elasticity, toughness. Now this strength is determined through tensile testing. This is the load a metal can withstand without fracturing. In fact, this is the maximum load it can withstand and the next property is ductility. It is also determined through tensile testing. It is the property of the metal which enables to be drawn into what is a thin wires easily. Next property hardness is determined through Brinell hardness testing. It is a measure of metals resistance to wear or erosion. Next property is the impact resistance and it is determined through impact test. This is the measure of resistance to impact of the metals. Next property elasticity. It is determined through tensile testing. It is the measure of the property of the what is a material to regain its original condition after being subjected to a load under its yield point and finally the toughness. It is determined through impact test. Toughness is the resistance to both elastic and plastic deformations. So these are the what is a testing of the mechanical properties of the component or the what is a specimens. Finally we come to the non-destructive testing. It is very important. Non-destructive testing is carried out in different ways. One is the visual inspection. Second one is the radiography. Third one is the magnetic particle inspection. Fourth one is the liquid penetrant inspection. This is also known as dipenetrant inspection. Next one is the ultrasonic inspection. Finally we have the eddy current inspection. So first we will see the visual inspection. Visual testing VT is the oldest and most widely used non-destructive testing method. Mechanical or optical aids may be necessary to perform this visual testing. The specimen should be well illuminated and its surface cleaned. Often visual inspection eliminates the need for further testing and the associated costs. There are three types of visual inspections. One is the direct visual testing. Second one is the remote visual testing and the third one is translucent visual testing. First one let us see the direct visual testing. Direct visual testing may usually be made when access is sufficient to place the eye within 600 mm of the surface to be examined. Sometimes when the what say object to be examined is closed within 600 mm then only we can use this technique direct visual testing. The visual angle between the plane of vision and surface being tested shall not be less than 30 degrees. Miners may be utilized to improve the angle of vision. Next one remote visual testing. In some cases remote visual examination may have to be substituted for direct examination. Remote visual examination may use visual aids such as mirrors, telescopes, fiber optics, cameras or other suitable instruments. Remote visual testing personal shall demonstrate SNELN 20 by 20 vision or better means the operator should have a good vision to carry out this testing. Next one translucent visual testing. It is a supplement of direct visual examination. The method uses the aid of artificial lighting which can be contained in an illuminator that produces directional lighting. The illuminator shall provide light of an intensity that will illuminate and diffuse the light evenly through the area or the region under examination. The ambient lighting must be so arranged that there are no surface glares or reflections from the surface under examination. What are the advantages of visual inspection? It is inexpensive, it is highly portable, we can get the results immediately there is no question of analysis and so on. Next one it can be done with minimum training. Next one this can be what say done where the it does not require what say so much of part preparation with minimum part preparation we can carry out this inspection. Now these are the disadvantages or the drawbacks of the visual inspection. The accuracy of visual inspection depends largely on the experience and knowledge of the inspector. So the inspector should have enough knowledge and experience. Next one the visual inspection is limited to detection of surface discontinuities. One is surface what say discontinuities can be detected. What about the internal cracks or internal blow holes those cannot be detected using visual inspection naturally. Next one only large discontinuities can be detected. If there are discontinuities which are very small in nature that may go undetected. Possibility of misinterpretation of scratches as cracks sometimes there will be some scratches will be there and the operator and if he does not have sufficient experience he may think that these scratches are the cracks. So in the non-destructive testing we have completed the visual inspection. Now let us see the radiography. This technique is suitable for the detection of internal defects in ferrous and non-ferrous metals and other materials. X-ray and gamma ray radiographic inspection are the two most common forms of this inspection technique. So in this radiography we use the X-ray and gamma rays for the examination of the materials. Now this is the principle of the radiography and here we can see this is the radiation source from here what say either X-rays or gamma rays will be emitting. Now this is the what say component to be examined. Now you can see here this component is having an internal crack here. Now this is the what say film, this is the what say film X-ray film and this is the top view of that film and here we can see and here what happens. So white means it is less exposure, black means dark means more exposure and here we can see the whole film there is less exposure that is why it is appearing as white. But here we can see where there is a crack there there is more exposure. So once there is a what say any what say place if we see more exposure means we can presume there is a defect or a crack. So here density varies with the amount of X-rays reaching the detector. So that is how the what say defect or the crack can be easily what say found out on the X-ray film. So this is the principle of the radiography and here we can see a portable iridium carrier and time controlled exposure unit in use for the gamma radiography. And here we can see gamma ray what say they are exposed and these are all the components and behind the components there is X-ray film. So what is the advantage of this gamma ray inspection at a time several components can be examined with one source of the gamma ray. Now these are the advantages of the radiography. Surface detects as well as internal defects can be detected information is presented pictorially suitable for any material ferrous materials non ferrous materials even non metals can be examined can inspect assembled components intact like a full shoot case no need to separate the parts. Film surface preparation is required sensitive to changes in thickness and density a permanent record of the result is obtained because it is exposed on the film. Now these are the disadvantages of radiography many safety precautions are to be taken if the precautions are not taken these radiations can go and harm human orientation between incident X-ray and flaw is critical otherwise sometimes the crack or the defect may go undetected. Next one many hours of technician training prior to use the technician must be given regress training prior to the actual application. Next one film processing and viewing facilities are necessary and these are expensive and time consuming. Next one determining flaw depth is impossible without additional angled exposure. Next one inexpensive initial expensive initial equipment cost the equipment is very costly that is how the initial what say cost will be very high. So we have completed visual inspection and radiography. Next one is the magnetic particle inspection how does magnetic particle inspection work a ferromagnetic test specimen is magnetized within a strong magnetic field created by a magnet. A ferromagnetic what say component or a material is the one which can be magnetized easily under the influence of a magnet. Now this ferromagnetic specimen is magnetized with a strong magnetic field created by a magnet. Now if the specimen has a discontinuity the discontinuity will interrupt the magnetic field flowing through the specimen and leakage field will occur. Now this here we can see this is the specimen if the specimen within the specimen if there is no crack if there is no defect and here we can see there are the two poles here this is the south pole and these are these are the north pole. On the other hand if there is a discontinuity if whether it is external discontinuity or internal discontinuity what will happen here also where there is a discontinuity there also north pole and south pole will be created. Then what we will do fine milled iron particles coated with pigment are applied to the test specimen. Now these particles are attracted to leakage fields and will cluster to form an indication directly over the discontinuity. So when we what say coat or when we sprinkle finely milled iron particles over the cast component or the specimen so no doubt here is the south pole and here is the north pole. On the poles or above the poles there will be more attraction of the this iron powder but if there is a discontinuity where there is a discontinuity there also this iron powder will be attracted. These particles are attracted to leakage fields and with cluster to form an indication directly over the discontinuity. Here we can see again iron powder is sticking here where there is discontinuity. This indication can be visually detected under proper lighting conditions and this is the schematic arrangement for detecting longitudinal defects using current flow through the component. Next one schematic arrangement for detecting circumferential and transverse defects using encircling coil. Now these are the advantages of magnetic particle inspection inexpensive and simple operation sensitive to small discontinuities immediate results moderate skill is enough not as in the case of the what say x-ray or the radiography moderate skill is enough. Next one surface as well as the surface discontinuities can be detected if the discontinuities are on the surface or even internally if they are existing these can be detected using the magnetic particle inspection. Next one relatively fast now these are the disadvantages of magnetic particle inspection surface must be accessible otherwise how can we go and sprinkle the what say iron powder. Next one rough surface interfere with the test path preparation is required ferromagnetic particle components only can be examined why because only ferromagnetic components can be magnetized under the influence of a magnet components must be demagnetized after the inspection. So this is time consuming. So we have completed the first three what say NDT methods. Next one is the liquid penetrant inspection this is also known as dipenetrant inspection what is the principle the dipenetrant inspection process detects surface what say connected cracks or other flaws such as laps or pores in all the metals as well as in most plastics and ceramics. Now important steps involved are what say clean the surface next one apply dipenetrant remove excess dipenetrant apply developer inspect the surface. So in this method we use three reagents one is the what say penetrant second one is the what say remover and next one is the developer first one dipenetrant next one cleaner and third one is the developer. So how to use three reagents or the three liquids so we will see now first step is the clean the part thoroughly using a suitable cleaner a stone aqueous degreasing and so on. So these are the what say reagents which are used to clean the surface very cleanly no dirt should be there on the component. Second one apply the penetrant to the surface being inspected we have seen that we will be using three liquids which are available in some containers one is the penetrant second one is the cleaner and the third one is the developer. Now we are taking the first reagent or the first liquid that is the penetrant apply the penetrant to the surface being inspected. So this is the component and here there might be a what say external what say defect or cracking is there but it is invisible to the naked eye. Now what we have done is we are applying this penetrant on the surface of the cast component. So the penetrant will be flowing all over the surface of the cast component. Now there is a crack now to this into this crack also this penetrant is going inside means it is penetrating through the leaks or the cracks third step remove excess penetrant using a cleaner and clean dry what say lint free cloth. Now here we can see this is the surface of the component the excess what say penetrant which is there everywhere must be cleaned and it must be removed. Now what about this crack the crack which is not visible to the naked human eye it has trapped the penetrant. Now this penetrant in here you see next step apply non aqueous developer. So this is the second reagent we will be using now this is the third reagent we will be using. Now you can see here this developer is falling on the surface of the component and there must be a distance of 6 to 12 inches from the developer can to the surface of the casting. Then what will happen the evaluation should occur using proper lighting now lighting is applied once this developer falls on this what say this penetrant it will be illuminating you see under the light it will be until now it is invisible this penetrant has gone inside the crack but it is not visible once we put this developer it is visible outside. So that is the principle of the liquid penetrant inspection now what are the advantages of the liquid penetrant examination one is it is highly portable what are the equipments only three reagents are the three liquids one is the developer second one is the cleaner sorry first one is the penetrant first one is the penetrant second one is the cleaner third one is the developer only three reagents and they are available in this kind of size cans. So we can take them anywhere in the plant so that way this process is highly portable. Next one inexpensive these reagents are not very costly since due to small discontinuities even a small discontinuity can be examined using this inspection inspection can be completed in less than 30 minutes. Now moderate skill is enough highly skilled what say personal or not required to carry out this inspection now what are the disadvantages of liquid penetrant inspection only surface defects can be detected what about the internal defects internal cracks now they cannot be examined using liquid penetrant testing. Next one rough or porous surfaces interfere with the test part preparation is required it must be cleaned very thoroughly very clean next one high degree of cleanliness is required. Now let us see the ultrasonic inspection the principle is in some respects similar to the echo sounding a short pulse of ultrasound is generated by applying an electric charge to a piezoelectric crystal the sound waves have the ability to travel a considerable distance in many metals and here we can see this is the schematic of the ultrasonic inspection. So this is the transducer a piezoelectric transducer means what does it mean so it generates the electric pulse so this is the component so we generate the what say pulses and ultrasonic waves will be coming and they will be passing through the component. So if a normal what say ultrasonic wave will be coming and it will go up to the extreme surface end of the cast component and it will be coming back now here we can see this is the initial pulse and after the wave ultrasonic wave comes back so this is the back surface echo this one this one. Now it is possible that at this somewhere there is a crack so this is the crack that be the case what will happen the wave will return little earlier than the original wave so here we can see this is the crack echo. So a sound what say specimen will be examined initially and how much time it is taking for the what for a return of the wave it will be recorded how many seconds or how many what say milliseconds it is taking. Now once there is a component will be what say change changing from time to time it is examined one after other now if there is any crack in a particular component we get the echo what say crack echo very quickly. So this is how the ultrasonic inspection is carried out. Now what are the advantages of ultrasonic inspection it is sensitive to both surface and subsurface discontinuities lens up to 10 meters can be examined no consumables required and less running cost naturally even in the liquid penetrant testing we were using three types of what say liquids and their consumables that is how the process is not what say highly cheap it is little expensive but here the running cost is almost zero no consumables required less running cost only single sided access is needed both the sides we do not have to access the component. Minimal part preparation is required next one it provides instantaneous results now it is capable of being fully automated it is non hazardous to operators or nearby personnel. So this is one of the what say good what say merits of this process in the case of the what say radiographic examination or the dipenetrant testing what happens. So the radiographic rays the x rays or the gamma rays are harmful to the human operators even in the case of the liquid penetrant testing. So these reagents cause strains to the human hands or to the workers. So that way it is non hazardous to the operators or nearby personnel its equipment can be highly portable or highly automated it is highly what say portable. Now these are the disadvantages of ultrasonic inspection surface must be accessible to transmit ultrasound. Next one skill and training is more extensive sometimes it is very difficult to what say discriminate the crack wave or the original wave. So only a highly experienced person person can differentiate between the what say crack wave and the original wave it normally requires a coupling medium to promote the transfer of sound energy into the test specimen. Materials that are rough irregular in shape very small or not homogeneous or difficult to inspect. Sometimes if the material is not homogeneous let us say what will happen at some place the density is less at some place at a particular place the density is very high then what will happen at that place where the density is very high it will take more time to penetrate and it will take more time for the return. That is how it causes the operator to get confused. Next one cast iron and other coarse grain materials are difficult to inspect due to low sound transmission. Next one linear defects oriented parallel to the sound beam may go undetected calibration of equipment and the characterization of flaws is required initially the equipment has to be what say calibrated otherwise it is very difficult to discriminate or to what say assess the flaws. So now let us come to the last one that is the eddy current inspection eddy currents can be produced in any electrically conducting material that is subjected to an alternating magnetic field. The magnitude of the eddy currents generated in the product is dependent on conductivity permeability and the setup geometry any change in the material or geometry can be detected by the excitation coil as a change in the coil impedance. Now here we can see the principle of the generation of the eddy current. Now this is the what say cast specimen now this is the primary coil the blue colored one is the primary coil normally wound over the secondaries. Now here is the secondary coil the red one is the secondary coil so in this setup we see there are two types of coils one is the primary coil and the other one is the secondary coil and through the primary coil we will be passing the current we will be passing the current then what will happen when this current passes through the primary coil eddy currents are generated that is the electromagnetic induction. So because of the electromagnetic induction eddy currents are generated and these eddy currents will be passing through the secondary coils. So this is the principle of the what say eddy current inspections what say method. Now how that what say defect will be examined now if let us assume there is no crack there is no defect internally for the cast specimen then what will happen as we send certain amount of primary current through the primary coil what say proportionate amount of eddy current will be generated for a sound cast specimen. Now as long as we change the what say what say specimens as long as there is no what say defect inside the cast component the same amount of secondary eddy current has to be generated so that is the principle. Now if there is any crack in a particular specimen then what will happen there will be change in the secondary current secondary eddy current that is how we can measure or we can detect the defect or a crack internal crack inside a cast specimen. So this is the simple principle of the eddy current inspection. Now what are the advantages of the eddy current inspection extremely compact and portable units are available this is very what say compact there is no heavy machinery involved. Next one suitable for the determination of a wide range of conditions of conducting materials such as defect in detection composition hardness conductivity permeability and so on surface as well as subsurface defects can be detected. Now this is the most interesting feature of this inspection what is that interesting feature not only that we can detect the cracks. Now composition now this generation of the eddy current will be depending on the composition in a particular cast specimen if there is a change of extreme change in the composition even then in such a case also the what say output of the eddy current will be different then we can know that there is a change in the composition and also when the hardness is changing abruptly changing at a particular place then also the amount of eddy current that is flowing through the secondary coil will be different. Now again depends upon the conductivity the secondary eddy current will be depending on the conductivity permeability and so on. So the secondary eddy current will be showing so many parameters so these are all the parameters which we can assess using the secondary eddy current. Now surface as well as the surface subsurface defects also can be detected no consumables you see no consumables are used as in the case of the liquid penetrant testing except probes which sometimes can be or to be changed. So these probes are semi consumables may be once in a while we have to change them otherwise the running cost is almost 0. Next one results we get immediately there is no question of processing if it is the you take for example the radiographic examination initially we expose the what say radiographic waves are the rays the x rays are the gamma rays on the photographic film and this photographic film has to be processed so that takes some time at least few hours but here we get the results immediately. Next one sensitive to small discontinuities also not only long discontinuities can be examined even a very small discontinuities can be examined using eddy current inspection. Next one these are the disadvantages of eddy current inspection surface must be accessible next one rough surface interferes with the test only electrically conductive components can be inspected so that is the drawback highly skilled of persons are required because sometimes there will be small what say variation in the output what say secondary eddy current. So that time the operator must be in a position to what say assess the change and he must be in a position to tell what is the reason for that is it internal crack or change in the composition or change in the hardness and so on he must be in a position to interpret the signal from a required parameter example crack can be masked by an unwanted parameter hardness and so on that is possible because of the hardness there is a variation in the output eddy current but it is possible that the operator may mistake that it is due to a crack that is that is how that is how a highly experienced person is required to conduct this what say eddy current inspection. Now this requires considerably more time now let us see the quality control quality control is carried out at the following stages quality control in pattern making and mould making quality control in melting of the metal quality control in heat treatment quality control in fettling and cleaning quality control in final inspection in all these cases the quality control has to be done. So what is this quality control is the what say molten metal is as per the required composition or not next one is the heat treatment is proper or not and next one what about the fettling and cleaning is it proper and next one final inspection does the cast what say component has the required surface finish does the cast component have the required surface finish. So these are all the what say things to be examined under the under the quality control first let us see the quality control in pattern making and mould making what is this how it is done the patterns should be checked for dimensions and other pattern elements does the pattern have the required dimensions are not does the pattern have the required pattern elements like the machining elements shrinkage elements draft elements tapper elements right and what say wrapping elements. So all these what say elements are to be given to the pattern. So does the pattern have all these elements are not so that is to be checked next one that dovetail pins of the moulding boxes should be checked against wear now generally we use the two moulding boxes the cope the upper one and the drag the lower one. So these two must be aligned properly these two boxes will have brackets at the middle now through the brackets we insert a dovetail pin and the dovetail pin must go and exactly through the two brackets of the two boxes and when we insert the dovetail pin there must not be any gap between the bracket hole and the dovetail pin. Sometimes it is possible that when we use these pins for several what say components then what will happen these pins will undergo wear if there is a wear of 1 mm then what will happen the moulding boxes can displace by 1 mm that be the case there will be a what say misarrayment between drag and the cope that is why we always have to check whether the dovetail pins are in good condition or they are worn out if they have already worn out we must replace them. So that is the quality control in the maintaining of the moulding boxes and the moulding what say dovetail pins next one moulding sand should be tested for different mould properties before ramming different tests must be conducted what is the moisture content what is the active clay content what is the permeability what is the hardness what is the green compression strength what is the dry compression strength. So likewise we have to conduct different what say tests before the moulding sand is rammed into the moulding boxes core oven temperature should be controlled carefully next one cores should be positioned carefully. So these are all the what say quality control what say in pattern and mould making next one quality control in melting metal charge should be melted in an appropriate furnace there are different furnace are available we have already seen and an appropriate furnace should be taken next one metal charge should be clean and dry sometimes it is possible that people take this scrap and they used to dump in the furnace and this scrap may contain what say unwanted what say oils lubricants and so on then the composition will be changing or hydrogen will be evolving because of the carbons or the hydro carbons present on the surface of the what say scrap. So the metal charge should be clean and dry fluxes and other additives should be dry if the moisture is present it must be what say dried out before they are used next one fluidity temperature should be carried out next one online analysis of molten metal should be carried out means as the molten metal is being melted so parallely we must examine it is the composition what is the composition does it possess all the required what say elements alloying elements or not molten metal should be degassed using different degassing techniques. So these are the what say different what say features of the quality control in melting. Next one quality control in heat treatment the heat treatment is carried out to the cast component after it is taken out from the molten metal. Next one then heat treatment should be carried out at correct temperatures rate of heating should be controlled to prevent crack formation sometimes if this what say temperature is not maintained properly during this heat treatment to cycle the cast component can undergo cracking. So that is why it should be controlled to prevent crack formation rate of cooling of casting should be controlled carefully if the what say casting is cooled abruptly again there will be cracking. Next one quality control in fettling and cleaning what is this fettling fettling means we take the what say we break this end take the casting outside then what will happen the casting will have what say the gating system the razor the sprue everything will be there these are not the parts of parts of the casting we do not want this. So these sprue the runner the gating system must be razor must be removed from the casting so that operation is known as the fettling gates razor etcetera should be removed with care so that cracks are not developed in the casting sometimes it is possible that as we are trying to crack the razors gating system the casting the actual casting can undergo cracking that should not happen. Next one chisel marks should be removed using grinding as we are what say cutting them sometimes there will be unwanted chisel marks will be there on the casting so they must be removed using grinding. Next one grinding should not cause any burning of the burning of marks so this is the quality control in fettling and cleaning. Next one quality control in final inspection the appearance and dimensions of the finished castings are to be checked as per the drawing. So does the casting possess the required dimensions as per the specifications given by the customer so that is the what say final checking as per the drawing. Next one after the test the surface of the casting may be given a preservative or a electropelating coating to prevent rusting. So this is very important after the casting has the required surface finish and the required what say geometrical tolerances then it must be given the preservative or an electropelating coating to prevent the rusting otherwise it will be of no use. So very soon it will be rusting before it is shipped to the customer it will become useless. So friends in this lecture we have seen the inspection and testing and also the quality control and in the inspection and testing we have learned different ways of inspection and testing that those are the controlling the composition of the metal we have seen. Next one how to what say inspect the dimensional inspection we have seen. Next one examination of surface quality and finish that also we have seen. Next one testing of different mechanical properties we have seen. Next we have seen non-destructive testing like visual inspection, radiographic inspection, magnetic inspection, ultrasonic inspection, liquid penetrant inspection, eddy current inspection we have seen. So with this we have completed the inspection and testing finally we have learned about the quality control. Quality control is carried out at different stages. Quality control in pattern and mould making, quality control in melting, quality control in heat treatment, quality control in fettling and cleaning, quality control in final inspection. So with this we are completing this lecture. Thank you.