 Hello friends, I am Satish Araparyani working as Assistant Professor, Department of Mechanical Volchian Institute of Technology Shorapuram. Today, I am discussing the topic Gravity Dicasting, Learning Out. At the end of this session, students will be able to understand Gravity Dicasting which is also called as Permanent Mold Casting. What are the contents we will cover in this session? First, we will have an introduction and we will have the little bit information about the Dicasting Machine. And what do you mean by Gravity Dicasting? What are the advantages compared to sand molding and limitations and then finally the applications? First, introduction. Dicasting process, first of all, has an advantage. The main drawback of sand molding process is a mold needs to prepare for each casting produce. And the specialty of Dicasting process, which is also called as Specialized Casting Process, a metallic mold is used to prepare sand mold with which larger number of castings are made. The metallic mold is also called as a dye. So these are the basic main advantage of Dicasting compared to mold. Here we don't need to prepare mold again and again and there we need to prepare the mold generally for the castings. Generally, the mold material employed is metal or any alloy. And the Dicasting is classified into two types basically. First one is called Gravity Dicasting which we will be studying in this session which is also called as permanent molding. And second is called Pressure Dicasting which we will be studying in future lecture. And pressure Dicasting which is further classified into cold chamber pressure Dicasting and hot chamber pressure Dicasting. Unlike Gravity Dicasting, in pressure Dicasting the molten metal is forced into permanent mold which is also called as a dye cavity under pressure. The pressure varies from 20 to 2000 kgf per square centimeter and is maintained till solidification stage is reached. The pressure is generally obtained by compressed air or hydraulically. So this is an initial basic difference between Gravity Dicasting and Pressure Dicasting. But we will study. Now Dicasting Machines. Dicasting machines perform the following functions. Holding the two dye halves firmly together. Closing the dye. Injecting molten metal into dye. Opening the dye. Ejecting the casting out of the dye. These are some of the basic steps which are performed with the help of Dicasting machine. Now we will come to the Gravity Dicasting our main topic. The casting is called Gravity Dicasting because molten metal is poured into mold under gravity only. Here no external force is applied to the liquid metal into the mold cavity. The casting is also called permanent mold casting because it uses the mold which is permanent. That is the mold can be used as many of times before it is discarded or rebuilt. Now we will come to see the figure here. Now we will see Gravity Dicasting which is also called permanent mold casting. This is hydraulic operated cylinder which is open and closed the mold. This is movable mold section, movable mold section and stationary mold section. So with the help of this cylinder which we can here close the mold and spray with the help of nozzle we can spray. And mold is preheated and closed. See the mold is preheated and then closed. Now coming, now the force is applied here. So core if it is all required is placed. These are the cavities with the help of this pressure. Core if you insert in the mold is closed. This second step we can say. Now see this is called gravity as I told you. The metal is poured in the mold with the help of gravity. It fills the mold cavity with the help of gravity. So now we will see. There is no some external force is required. Just this is the stationary part of the mold. This is moving part with the help of force. This is closed and finally the molten metal is poured. And molten metal solidifies itself in the mold. Now we will come to the point permanent mold castings are made. How permanent mold castings are made? Permanent mold castings are made with the help of gray cast iron into two halves. Having the high resistance to thermal shocks, alloy steels. Why? For very high temperature and withstanding surface erosion or non ferrous alloys. Inner surface of molds are closed first and refractory and with the lamp black or coroy. This is done in order to reduce the chilling effect. Chilling effect in compared to sand molding in die casting is more because mold itself is made up of metal or alloys. So chilling effect on the cast metal and facilitate the removal of casting and to prevent the adherence of molten metal into the mold. So we are applying refractory and then lamp black or coroy into the mold. Pouring cup risers, gates, sprue are present in the mold. Now what are the advantages compared to what you can say sand casting? Here in case we in die casting we can have a very closer dimensional tolerances. Because mold itself is made of metal and easily we can achieve the same. Second, smoother surface and better appearance can be obtained. Third, fine grain metal surface because of chilling effect as I told you chilling effect is more compared to sand casting. Mass production is more economical because mold itself is made of metal or alloys. Low shrinkage and gas porosity because porosity is less or gas shrinkage. Problems are less associated with the metal casting compared to the sand mold. Now we think whether toys, small baby toys can be produced with this process? Now coming to the limitations. The first and foremost big limitation associated with this process is permanent mold cost is more compared to sand mold. Here as it is metal and some setup is required so the casting is more compared to sand mold. And the second basically it is suited for small or medium size non ferrous castings only. And the third, several defects such as stress and surface hardening may be produced due to surface chilling effect. As I told you in previous slide also the chilling effect is more compared to the sand because the mold itself is made of metal parts, alloys parts. So here in this process in die casting the chilling effect is more so the several defects like stress and surface hardening may be produced due to surface chilling effect. Since the gating system is cut in the mold halves once machine it cannot be changed. Now as the gating system as it is flowing metal is flowed through the gravity and it is in the permanent mold also through the once the gating system is cut. So it cannot be what you can say it can be repaired but it cost once again it is generally cost heavy or many times it needs to that mold itself needs to be discarded. So it costs more or generally it is not economical in that case. The extremely high temperature of the molten metal make this metal unsuitable for steel casting. Now coming to the application part the basic application or basically these processes applied for carburetor bodies of the what you can say automobiles. Refrigation castings oil pump bodies connecting rods and automotive pistons are made of from this process typewriter segments etc. Now what is basically throughout this session what we have understand is the basically the mold itself has an has a gating system in the casting in the mold itself from which molten metal is poured. Then once it is made so there are thorough design consideration needs to made because we cannot modify again and again. So generally it is suited for what you can say mass production system it is not suited generally for prototype or small production system. Basically this is and it is also as it is a gravity die casting it is also with the help of gravity only the metal pours. In the next session what we will be studying is what are the advantages or disadvantages compared with the help of pressure die casting of this process. So this process is many times suited for small to medium side castings only and because of chilling effects we need to take care many things in this case. Now the references what we have taken is from YouTube and PL Jane principle of foundry technology and the NPTEL notes. Thank you.