 Welcome, friends. In the previous class, we have been learning about the multiple raisering and in this multiple raisering, we have seen the concept of what is a end effect and the raisering effect and we have seen the need for adopting multiple raisers if the feeding length is less than the casting length. Now let us continue this. Now we will come across three more terms called feeding distance, feeding length and center line shrinkage. Of course, this feeding distance we have already seen. Now let us learn feeding length and the center line shrinkage. Now there is a difference between feeding distance and feeding length. For example, say this is the casting, this whole thing is the casting and this is the raiser, this is the raiser. Now around the raiser, there is a raiser zone is there, means in this zone, in this circle there is no shrinkage because the raiser is present. Now outside this raiser zone, you can see here EZL means end effect zone, end zone or simply so that we can see here this much say starting from the end. So this is the end of the casting, starting from here up to here, this dotted portion is the end zone means in this portion there is no shrinkage cavity because it is covered by the end effect and this much is covered by the raisering effect. Now here we can see EZL means end zone length. So this is the EZL, you can see this is the end zone length. Next one, RZL that is the length covered by the raiser effect. So this is that one, RZL, RZL. Next one, feeding distance, feeding distance means it is the sum of raiser effect and end effect. Here we can see, so here this much is the what is the raiser effect, RZL which is the feeding distance which is covered in the what is the raiser zone, this is the raiser effect, this is the raiser effect. Now from here to here, so from this end to this end you see this is the end zone up to this point this is the end effect. So the sum of end effect and raiser effect is known as the feeding distance. Now what is the feeding length? Now in this case feeding distance is equal to feeding length means the length of the casting is equal to means this portion, this portion the length diagonally is equal to feeding distance. That is why feeding length is equal to feeding distance in this section means casting section is just covered by the raiser zones and the end zones. Now we will see the difference between the what is the feeding distance and feeding length more clearly. Now let us see here, now the length of the casting is little more than the previous one. Now the length is such that this is the end zone, the end zone length is this much. This much is the raiser zone length from here but if we start from here and measure like this from here to here this much portion is the RZL means start from here and you end here. So this is the raiser effect. Now where is the end effect? End effect starts from here, here to here so that is the end effect. So this sum of end effect and raiser effect is the feeding distance. Now you can see there is a gap means that including that there means sum of this raiser effect, sum of this end effect and sum of that gap, sum of these three components is known as the feeding length means that is the actual length in the casting measured diagonally in this case. So here what we can conclude, feeding length is greater than the feeding distance, shrinkage porosity forms in the shaded sections of the casting not covered by the raiser zone or the end zones. For example you see up to this much portion the casting it is covered by the raiser zone. So there is no possibility of formation of the shrinkage cavity up to here. Now this much portion is the end zone. So in this there is no chance of formation of the shrinkage cavity because of the end effect. What about to this portion starting from here say this shaded portion, this is not covered by the raiser effect, this is not covered by the end effect. So there will be shrinkage cavity will be there. Why a shrinkage cavity is there? Because in this case the feeding length is greater than the feeding distance. So there should not be any gap between EZL and RZL where EZL is the end zone length and RZL is the raiser zone length. But unfortunately in this case this is the what say EZL and this is the RZL there is a gap. So that is how a shrinkage can take place in this case. Now let us see some cases feeding distance is equal to the feeding length means the length of the casting is such that the what say that section to be fed by the raiser is equal to the feeding distance. Then what will happen? No shrinkage along the feeding length. Say for example this is the casting, this is the casting and this is the raiser. Now there will be raiser effect will be there, the raiser effect will be 2t means the what say distance covered by the raiser to prevent shrinkage that is 2t here we can see. Now this is end effect, what is that end effect? Distance covered by the edges of the casting to prevent the shrinkage cavity. So this is 2.5t. So some of these components is known as the feeding distance and that is equal to 4.5t. One side it is 4.5t and the other side is also it is 4.5t where t is the thickness of the what say slab or thickness of the section of the casting to be fed by the concerned raiser. Now let us see another case where 2 raisers are used. In this case also the feeding distance is equal to feeding length. Here we can see from here right this is one raiser, one side there is 2t that is the raiser effect and the other side there is 2t that is the raiser effect. And the distance total distance or the total feeding distance between these two raisers is 2t plus 2t that is 4t and we have arranged the raiser such that the distance between these two raisers is exactly equal to 2t. So there is no question of formation of the shrinkage cavity. Now let us see another case feeding length is greater than the feeding distance. You see here this is the casting and there is single raiser is there this is the raiser. Now this is the length of that section to be fed by this casting this raiser. Now here we can see raiser effect is there means distance covered by the raiser to prevent the shrinkage cavity that is 2t and this is the end effect 2.5t that is the distance covered by the edge of the casting to prevent the shrinkage cavity. So this is 2.5t. So in this portion there is no shrinkage cavity because of the end effect. In this portion there is no shrinkage cavity because of the raiser effect. Now what about this portion this portion is not covered by the raiser or it is not covered by the raiser effect and it is not covered by the end effect then what will happen there will be shrinkage will be there. You can see this is known as the center line shrinkage. So center line shrinkage can takes place when feeding length is greater than the feeding distance. Feeding length means the actual length falling under the load of the raiser. So this whole length is the feeding length whereas feeding distance is the sum of the end effect and the raiser effect. So in this case the feeding length is greater than the feeding distance. So that is how a center line shrinkage cavity what is the defect is arising here. And we can see another case where there are two raisers and for this one raiser one side there is 2t that is the raiser effect. So there is no question of shrinkage cavity in this region and this is another raiser and here there is raiser effect 2t where t is the thickness of the section. Now in this region also there is no shrinkage cavity because of the raiser effect. Now what about this portion this is not covered by the this raiser the left side raiser this is not covered by the right side raiser then what will happen of course there is no question of the end effect because there is no edge only two raisers are there on both sides then what will happen the center portion which is not covered by either of the raisers there will be shrinkage cavity here also feeding length is greater than the feeding distance. Now here what is the feeding distance the feeding distance is here it is 2t and here it is 2t the total feeding distance between these two raisers is 40 whereas the feeding length the actual distance falling under the two raisers is greater than the feeding distance that is how a shrinkage what is a cavity will take place. So we will call it as the center line shrinkage here also. So this is the center line shrinkage ways to increase the feeding distance. Now we just now we have seen that when the feeding length is greater than the feeding distance what is a center line shrinkage defect will arise. Now at any cost we have to see that the feeding distance we have to increase or to improve how to improve we can place a chill here for example this is the casting and this is the raiser and again here you can see there is 2t that is the raiser effect and here there will be 2.5t that is the end effect and we can increase the end effect by placing a chill here. So chill is a steel block which is placed on the side of the mould wall then what will happen it will rapidly increases the heat because of that more what say part of the casting will be solidifying in lesser time that is how the end effect will be more compared to the case where there is no chill. So by placing a chill on the inside the mould we can increase the feeding distance thus we can also increase the efficiency of the raiser. Next one let us see we are what say learning about the modification of the design so instead of going for a single raiser if we go for multiple raisers we can have a better efficiency that is what we have seen under the multiple raisering. Now we will see another what say topic called bottle raisering by incorporating bottle raisering we can improve the raiser efficiency what is this bottle raisering or what is a bottle raiser bottle raisering a primary shrinkage hole a pipe is created quickly in a raiser so this what say pipe because of this pipe the metal will be forced inside the mould cavity a pipe is created on the sides of the raiser because of that the molten metal which is present in the raiser will be pushed inside because of the atmospheric pressure if the liquid metal in the raiser is not open to the atmosphere then the raiser will not function. So because of the atmospheric pressure once a pipe is created on the both the sides around the what say what say surface the molten metal will be pushed inside the cavity. Atmospheric pressure is necessary to push the metal into the casting a bottle raiser it is also known as hain raiser has such a small area at the top diameter that will begin to pipe very quickly what is the specialty of a bottle raiser it is a top diameter will be very small. So because of that the what say piping takes place very quickly means a pipe will be created at the top means the what say molten metal near the mould wall will be solidifying quickly a circular pipe is created and inside there will be liquid metal that will be pushed into the molten what say cavity. So in order to have sufficient feed metal volume these raisers must be taller than the classical design. So usually we have seen that especially in the NRL method what is the H by D ratio it will be between 0.5 to 1 the H by D ratio should not be greater than 1. But here the length of the what say raisers will be more than the conventional raisers the height to diameter ratio is 1.5 to 1. So this is the typical height to diameter ratio for a bottle raiser. Now this is the typical appearance of a bottle raiser you can see this whole thing is a bottle raiser. See it is slanted at the bottom this is the bottom diameter you can see raiser bottom diameter is this much starting from here to here whereas this is the top diameter you see top diameter is very small whereas bottom diameter is very large. And here we can see this is the gate right through this gate right molten metal enters and this is this side is the casting and this is the height of the raiser you can see this is the height of the raiser. Now we come across a another interesting term called significant modulus of the casting. What is this significant modulus? This significant modulus we can see say there is a difference in the diameters of the raiser at the top it is very small at the bottom it is very large. Now there is a difference between the what say diameters both at the top and the bottom. Now half of this difference in the diameters is known as the significant modulus right half of that difference that is indicated by MS. Now at the bottom it will be 2 MS and this side there will be 2 MS formula for bottle raiser how to design the bottle raiser right raiser bottom diameter is equal to 4 into MS plus raiser top diameter. The casting feed metal required is equal to 4 percent of the casting weight. Raiser feed volume determined by the raiser top diameter and height to diameter ratio. Use the tallest raiser possible for the flask size and raiser height is equal to h by d ratio into raiser top diameter. Now this is the what say feed metal table for bottle raiser in different cases means when the h by d ratio is changing in different cases. So these are the what say feed metal what say diameters in different cases here we can see h by d ratio is equal to 8 is to 1. Now when the top diameter is 10 say what say mm the feed weight is equal to 44 grams. When the top diameter 20 mm the feed weight is equal to 352 grams when the top diameter is 30 mm it is 1186 grams when the top diameter is 40 mm the feed weight is 2813 grams and when the top diameter is 50 mm the feed weight is 5495 grams. So these are the cases when h by d ratio is equal to 8 is to 1. Now h by d ratio is 6 is to 1 that be the case when the top diameter is 10 mm the feed weight is 32 grams, when the top diameter is 20 mm the feed weight is 264 grams, when the top diameter is 30 mm the feed weight is 890 grams, when the top diameter is 40 mm the feed weight is 2110 grams, when the top diameter is 50 mm the feed weight is 421 grams. So these are the cases when h by d ratio is equal to 6 is to 1. Now let us see another case where h by d ratio is equal to 5 is to 1, when the top diameter is 10 mm the feed weight is 28 grams, when the top diameter is 20 mm the feed weight is 219 grams, when the top diameter is 30 mm the feed weight is 741 grams, when the top diameter is 40 mm the feed weight is 1758 grams, when the top diameter is 50 mm the feed weight is 3434 grams. So this is the case when the h by d ratio is equal to 5 is to 1. Now let us solve a problem the weight of your casting is 85 kilograms the height of the cope is 330 mm, if the significant modulus of the casting MS is 15 mm design the bottle raiser for the casting. Now we have to design the bottle raiser casting weight is equal to 85 grams given, cope height is equal to 330 mm, significant modulus of the casting MS is equal to 15 mm, feed metal required formula we have already seen 4 percent of the casting weight that is equal to 3400 grams. So this is the feed metal, now we need to for this feed metal we need to find out the dimensions of the bottle raiser. First from the table the raiser top diameter and h by d ratio corresponding to 3434 grams of the feed metal. So this is the what is a standard table for the bottle raiser and here we can see that much what say feed metal we can see here in this case 3434 grams, so means so this is the diameter top diameter of the bottle raiser and say this is the h by d ratio 5 is to 1 accordingly we can design the bottle raiser that be the case then what will happen raiser top diameter corresponding to 3434 grams of feed metal is equal to 50 mm, h by d ratio is equal to 5 is to 1. Now raiser bottom diameter is equal to 4 into MS plus raiser top diameter where MS is the significant modulus now that is equal to 4 into 15 mm plus 50 that is equal to 110 mm. So the raiser height is equal to h by d ratio is 5 is to 1, so raiser height is equal to 5 into 50 that is equal to 250 mm. So this is the raiser height and what about the bottom diameter bottom diameter is 110 mm, what about the top diameter 50 mm. So this is the design for the bottle raiser in this case. Now we are seeing learning about the case how to modify the design of the raiser to improve the raiser's efficiency under that we have seen we can go for the multiple raisers and also we can go for the bottle raiser. Now there is a term called another topic called safety margin by what say incorporating the safety margin by what say carefully designing the safety margin we can improve the raiser's efficiency. Now let us see what is this safety margin you can see this one this is the casting and this is the raiser. Now once we what say pour the molten metal immediately this much portion right a pipe is created here on the sides. Now inside the liquid metal and it flows this liquid metal here and it will be feeding the casting thus there is a what say cavity will be created here a cavity will be created. So this much portion there is a cavity and this is the solidified portion. Now this cavity is like a right pipe and it comes and it is stopping here. Now what is this this is the safety margin safety margin SM is defined as the distance from the raiser casting contact surface to the tip of the raiser pipe. So this is the safety margin now what does this indicate now when the if this safety margin is just touching the what say casting no problem. Because if this safety margin is going below the casting surface means what does it mean there is shrinkage cavity is there on the other hand if the safety margin is too much what does it mean means from this raiser you see only this much length of the raiser is utilized for the feeding of the casting. What about this this much length of the casting starting from the surface of the casting to here that much portion of the raiser is not involved in the feeding of the casting. Now if the safety margin is more and more what will happen that extra portion or that extra length of the raiser is not involved in feeding of the casting means that say waste is only. So the safety margin should be minimum it should not be too much on the other hand it should not be 0, 0 means it will be just touching and it should not be negative. Safety margin for different alloys is to be found out by experimentation the height of the raiser should be such that the safety margin does not exceed 2 to 5 centimeters. If the safety margin is more than 5 centimeters certainly there would not be any shrinkage cavity but that is a wastage of the raiser material. Whatever what say length of the raiser covered in that safety margin is a waste and on the other hand it should not be too less the in such a case there may be a shrinkage cavity and it should not be negative. So the height of the what say the length of the safety margin should be between 2 to 5 centimeters. So this safety margin by properly designing the safety margin by conducting the experiments and we have to find out the safety margin for different cast alloys accordingly we have to fix up the what say height of the raiser then the efficiency of the raiser will be improved. If the safety margin is negative then the raiser pipe extends into the casting in such a case shrinkage cavity will arise in the casting. Next one there is another topic called raiser necking. So this is also a modification to the raiser design with this also with this raiser necking also we can improve the efficiency of the raiser. What is this raiser necking? Now you can see here so this is the raiser and the casting is this side now the raiser is given a necking here. So this will improve the efficiency of the raiser. Now here we can see T is the thickness of the casting of the or the section to be fed by the raiser and D is the diameter of the raiser, HN is the thickness of the neck this much portion is the HN is the thickness of the neck that is equal to 0.6 to 0.8 times the thickness of the casting or the thickness of the section to be fed. Next one LN is the radius of the neck this is the LN that is equal to D by 3 where D is the diameter of the raiser. Next one WN is equal to width of the neck that is equal to 2.5 times LN plus 0.18 D. So by incorporating raiser necking we can improve the efficiency of the raiser finally tapering is there by tapering means by giving a taper to the casting we can improve the raiser's efficiency. Here we can see this is the casting this is the casting this is the casting and this is the raiser. Now a taper is provided you can see here here the thickness is more and slowly the thickness is reduced this will definitely improve the performance of the raiser. Now here we can see this is the end zone length end effect and here we can see this is the raiser zone length and here a taper is given. So because of this taper the what say efficiency of the raiser will be certainly improving. Now how to choose this taper and this is the what say graph available to us and here we can see on the x axis width to thickness ratio W by T on the x axis and the y axis we can see taper that is equal to height by length height of the taper divided by length of the taper and here we can see the width to thickness ratio 1, 2, 3 up to 9 and here we can see the taper height divided by L so it is this much. So by what say considering this graph we can successfully what say design the taper for the casting which will definitely improve the efficiency of the raiser. Now computers in design in raiser design so far we have been learning about the different methods of the raiser design. We have seen the Keynes method which was very tedious and time consuming. Next we have seen the modulus method the modulus method right it requires that we need to find out the surface area of the casting. Of course in the in these lectures we have what say considered some simple shaped castings so that is how we were able to find out the what say surface area of the castings very easily but in practice the surface area would be very complex. In such a case calculating the surface area would be very tough that is how even the modulus method has got certain practical difficulties and finally we have seen the NRL method the naval research laboratory method where the what say time what say required would be very less within no time we can design the raiser right. So this surface area does not come into picture but still we need to check the what say our design using the feed volume concept whether what we have designed is proper or not that way that also takes time but fortunately the computers have what say come into picture in the raiser design using the computer softwares we can also design the raisers. So we will see certain important source what say computer softwares that have been developed around the world to for the raiser design important softwares for the raiser design one is the magma soft another one is the auto cast another one is the solid cast another one is the pro cast and another one is the cast CAE and there are more softwares which are available for the raiser design. Let us quickly review what the softwares are magma soft right it was developed by magma Germany magma soft predicts the following characteristics right it predicts the raiser and gating system we can design raiser and gating system internal porosity is predicted by this software magma soft residual stresses are predicted by this software hot tiering that is a defect which is a what say cracking of the casting during solidification. So this hot tiering is also predicted by magma soft finally the microstructure which is very important as far as the properties are concerned that is also predicted by magma soft but though it has got to several components one component is the what say design of the raiser ring and gating. So we can using this magma soft we can design the raiser ring and gating and this is an what say an example using the magma soft method right. So this is the computational model of the original rigging as used in the magma soft simulation you can see yes these are all the sleeves where sleeves are used and here we are you placing the chills and this is the pouring cup and this is the sprue and it will successfully predict the what say design of the raiser in different cases when sleeves are used, when sleeves are not used, when chills are there, when chills are not there likewise in different cases what should be the dimension or the design of the raiser it will be successfully predicting. Next one there is another software called AutoCast. So this was developed by 3D Foundry Tech private limited Mumbai in India right it has got 3 modules one is part module, second one is the mould module, next one feed module and gate module and so on. Now the feed module helps the Foundry man to optimally design the raiser and to optimally locate it in the right position right. So this software we can use and this feed module will help us to design the raiser not only to design the raiser to locate the raiser in the right position so this software can be used. So this is an important software produced in India and this is the optimization of the raiser size and evaluation of the insulating sleeve by AutoCast feed module here we can see right. So here the size of the raiser is optimized and where in insulating sleeve is used. Next one next software SolidCast it contains the raiser design wizard and gating wizard design wizard it can be used to simulate castings poured in gray cast iron, ductile cast iron, steel, aluminum, copper based alloys, nickel based alloys and almost any other alloys and here we can see the what is a simulation using this software under what is a raiser shrinkage predicted in gray iron casting simulated with SolidCast. Next one we have the ProCast software it was developed by ESI group it has different modules like quick cast right, SAIL, SA3D etcetera right. Among these modules SAIL, SA3D helps to calculate the raiser size gating and running systems especially for high pressure die casting process. Here we can see simulation using ProCast. Next one cast CAE so this is another software developed by Finland company this tool has different modules cast design, cast check and so on. Among these modules cast design is a simulation package that helps in designing the raisering system for the casting and here we can see simulation using cast CAE. Friends till now what we have learned we have seen in these two lectures we have seen the feed volume concept right. So, alpha into V C plus V R is equal to eta f into V R where V C is the volume of the casting and V R is the volume of the raiser and alpha is the percentage volumetric shrinkage of the cast metal and this is different for different cast alloys and eta f is the raiser efficiency. What is raiser efficiency? It is the ratio of feed metal available to the total volume of the raiser. We have also seen the methods to improve the raiser efficiency. The raiser efficiency can be improved by direct achieving directional solidification. Again directional solidification can be achieved using insulating sleeves. Directional solidification can be achieved using chills. Directional solidification can also be achieved using exothermic materials. Next one the raiser efficiency can be improved by adopting blind raisers. So, this is what we have learned. Finally, we have learned that modification of the raiser's design also helps us to improve the efficiency of the raiser. How to modify the raiser design? One is the multiple raisering, second one bottle raisering, safety margin and we have seen the other factors which will be helping us to improve the modify the design. And this is the fifth lecture I am delivering on the design of the raisering system. In this five lectures what we have learned, we have seen the Keynes method and in the Keynes method we have to find out the freezing ratio and also we have to find out the what say surface sorry we have to find out the freezing ratio and accordingly we have to find out the design of the raiser. And we have seen that Keynes method is tedious and time consuming. And we have seen the modulus method where the what say freezing ratio does not come into picture, but we have to what say calculate the modulus of the casting and modulus of the raiser where modulus is the volume to surface area ratio of the volume to surface area. And surface area we need to calculate and finally, we have seen the Neville research laboratory method. So, this was developed by the US Navy and here the what say modulus does not come into picture, the surface area of the casting does not come into picture only shape factor comes into picture. And using the shape factor we can directly find out the what say design of the raiser using the raiser curve and also the raiser what say height selection charts that is what we have learned in these five lectures finally, we have seen how to what say improve the raisers efficiency. So, with this we are closing the design of the raisering system and in the next class I will be delivering the lecture on the design of the gating system. Thank you.