 Hello friends. I am Satish Arparyani, assistant professor working in the mechanical department Vulture Institute of Technology, Sholapur. Today we are discussing on the topic called shell molding. At the end of this session, students will be able to understand shell molding, its advantages and what are the limitations. Also, we will touch over the application part. The content which sequence we will follow is, first we will discuss about shell molding. Then, we will discuss in depth about the procedure of what is involved in the shell molding. Next, we will discuss the advantages and limitations involved in shell molding process. And finally, we will discuss the topic called applications of the shell molding. First, what do you mean by shell molding? The shell molding, this process was invented by Dr. Croning in Germany. Hence, is also called as Croning process. It is a process in which sand mixed with thermosetting resin. I repeat, this sand is mixed with thermosetting resin, is allowed to come in contact with heated metallic pattern. So, here the metallic pattern is heated and sand with thermosetting resin is used which forms a thin and strong shell of the mold is formed around the pattern. Then, shell is removed from the pattern and cope and drag are removed together and kept in a flask with necessary backup material. After that, molten metal is poured in the mold. In short, we have discussed what do you mean by shell molding. Now, we will go through the process of involved in shell molding. Here, the metal is heated up to 175 to 350 degrees centigrade depending upon the what are the constraints, what is the size, what are the design parameters involved in that part. So, 175 to 350 is the range generally used which is clamped over the box containing sand mixed with thermosetting resin such as the thermosetting resin such as phenol formaldehyde, ura formaldehyde or polyesters. The box and the pattern are inverted for the short time. The mixture when it comes in contact with the hot pattern it causes an initial set as the as the thermosetting resin is used and builds up a coherent sand shell next to the pattern. The thickness of the shell is about 6 mm to 18 mm and is dependent on pattern temperature and sand mixture. This takes only 5 to 20 seconds. Then, box and pattern are brought in its original position. The shell of the resin bonded sand is retained on the pattern surface while unaffected sand falls into the box. The shell still on the pattern is cured by heating it in an oven from 250 degrees centigrade to 350 degrees centigrade for about 1 to 3 minutes. The assembly from the oven and the shell is stripped from the pattern by ejector pins in order to obtain the clean stripping a silicone parting agent may be sprayed on the pattern. The shell halves are assembled with the help of clamps and backing material as the name itself suggests shell which is very the thickness is very thin. So, during when we start clamping it we may have the chances that it can break it. So, backing material first is provided very clearly in that. Shell now after that backing material the shell which are assembled now with that shell once the shell assembled the shell molding is ready for pouring. Now, we will go through the diagram as we see here this is the hot pattern right these are the hot pattern and this is the cell sand here and this is which is called as dumping box. This is our handles which are used in that. This is the step one which is called sand mixer in the box here mixer is there. This pattern is now heated. Now in the step two sand resin mixture dumped over the heated pattern. This is inverted you see you see inverted. Now what will happen? This is the heated pattern here after heating the pattern is there. So, here now the resin which is thermosetting resin it comes in contact with the heated pattern simple process very. Now coming to the third part again it is brought to the same position as in the step one. Now you will see the green layer what we can see here it is called shell which is formed. It is very thinner. So, see this is the thin part because it was heated pattern thermosetting resin was used and what which the sand is not used again it comes back to the box. This is called unused sand which can be used for in further process. Now this after sand this fourth step with the help of ejector pins see ejector pins this has been removed. Now as we can see there is chances of ejector pins are applied with some forces. The chance is that this thin can have not a clear surface. So, some agent can be applied so that the line where it is being parted off be very clean or to some extent but in good condition we can say. Now after this this in similar way this first half and second half are joined together here we can see. These are this is the flask this is the clamp we can see these are filler materials which have been used and these are in shape and now this these are called shell now the shell melding is very much ready for pouring. So, we can pour and this kind of shape what we will get get as a part. So, what we have to understand very simple process a heated pattern is there these are the thermosetting resin sand mixture once it is inverted a thin shell is formed the new sand comes back up then with the help of ejector pins these are been removed first half second half are assembled with the help of clamps and then it is almost ready for pouring. Now coming after seeing the what are the advanced seeing the procedure now we will go through what are the advantages involved in shell molding. First and foremost big advantage which is involved in shell molding is dimensional accuracy. The process has an ability to produce casting to tight dimensional tolerances hence machining allowance can be reduced which ultimately helps in reduction of fettling and finishing cost. See once we will give if the dimensional accuracy is good. So, we cannot give more allowance what you when for what you can say machining allowance or something. So, the cost finally you see materials we are losing in machining. So, which is again involves some cost to finally that cost is being waved off in that case. So, it is good and finally costing is also coming less the shell molding process accommodates easily deep drawer patterns with less tapers than conventional production process. Second hollow cores with the shell molding hollow cores and thin profile molds can be possible. The characters involve economics in sand usage and ease of handling hollow cores increase the permeability hence usage of very fine sand is also possible. Permeability again this the role of permeability is related to what are the what you can say casting defects it is related if the good to good extent if the permeability is not there we can have a good casting defects. So, this process has an very good advantage that it has good permeability and so fine sands can be easily possible. Then comes the excellent surface finish shell molding process has ability to produce casting with excellent surface finish because as we have seen the very thin parts thin surface can be produced and capacity to produce very fine detail sand to metal ratio this is one of the very important factor. This is the unique process that gives hollow cores and thin wall molds which results in substantially weight reduction hence material saving the normal sand to metal ratio is one ratio one which is much lower than other processes. Longer shelf life when properly stored the shell sands have the indefinite shelf life hence these sands can be stored and used as needed in the foundry. Then coming to the big advantages is ease of handling the molds and the cores made by the shell molding have exceptional resistance to damage during storage and handling they have a very very high resistance to humidity and can be easily stored for a long period. So, once if these molds and cores made which were made with the help of shell molding have exceptional resistance to damage means they can be stored or a handle again and again again finally it results so less cost we can see. And next important advantage is resistance to moisture pickup the shell molding has a higher resistance to moisture and can be stored in humid conditions for months together. This is again we can see in the upper point handling storing resistance to moisture pickup these are the superb advantages available with this kind of process the resin used in shell molding process is very stable and moisture resistance. Next come the big advantage is excellent flowability the dry coating on the sands give better flowability and blowing ability compared to process based on wet sandmixtures this property helps in producing intricate cores and molds which can be blown to greater density. Cores for the water jacket examples these are lesser pattern wear as most of the patterns are made from the cast iron very little or no wear is observed which results in higher pattern life. This helps in producing large number of catans casting sorry these this helps in producing large number of castings without much difficulty. Now we have seen there are so many advantages but there are certain disadvantages which are associated with the this process first pick disadvantages high cost of the process the phenolic resins which we use for the shell molding process are very costly the percentage of resined uses is also very high compared to other processes hence this process requires a very tight control over a shell thickness else the competitive news all of all the process will be sacrificed. High tolling cost the shell molding is thermos set in nature thereby requiring higher curing temperature the pattern used are of cast iron smooth surfaces and a very low expansion coefficient. So, there is tolling cost is high cost of this process itself is high because of phenolic resins use and the percentage of resins use if it is to greater extent the competitive will be totally lost. Then comes the cycle time compared to the cycle time required for shell molding is more either box or carbon dioxide process limited casting weight the as we see the shell itself the name shell itself as I told in the previous slides also the thickness is very small the shell molding process is best suited for use in small intricate and lightweight casting the process can effectively use for casting weights up to maximum you can say 80 kg reuse of sand is difficult certain casting shapes are unsuitable when properly parting and gating is not available. Now coming after seeing the disadvantages will come to the application parts to some extent we will see it is well suited for ferrous and both non ferrous alloys casting in the range of 0.1 to 10 kg alloys that can be easily cast by shell molding are aluminum alloys copper alloys cast iron stainless steels component cast by the shell molding are smaller pipes camshaft bushings wall bodies paces brackets bearing caps shafts and gears automotive rocker arms and walls etc to some extent what I have shown here the application of shell molding now please think and list the parameters which can affect the quality of the shell molding take some time and please think and list the parameters which affect the quality of shell molding the references are used in this session are from NPTEL PL Jane and Wikipedia thank you