 Hello everyone, today we are learning on the topic called gating system. At the end of this session, we will be able to understand the gating system and its elements and what are the types of gating system. What the contents are covered here, gating system, elements of gating system, goals of gating system and types of gating system. Now first we will look at what is gating system? Gating system, the assembly of channels which facilitates the molten metal to enter into the mould cavity is called gating system. Alternatively, it can be said the gating system refers to all passages, ways through which molten metal passes to enter into the mould cavity. The nomenclature of the gating system depends upon the function of different channels which they perform. Now we will be looking at what are the different elements of gating system. First look at this figure. What we see at this figure is first the pouring cup. This is the pouring cup where the molten metal is the first place to enter into the system to make the casting. Second we will immediately observe under the pouring cup a sprue. It connects the pouring cup with the sprue well. Generally the design of the sprue helps us to reduce the defects like erosion. The third element what is called sprue well. Generally this sprue well is placed immediately under the sprue which helps to reduce the turbulence when it is flowing from sprue to runners. Now after the metal enters from pouring cup to sprue to sprue well it runs, rushes through the runner. Runner is what it connects the sprue well to different elements of ingates. Now you see the runners are of straight section. It depends upon how much runner we give depends upon the casting weight, casting size and type of the casting which we use. From runners we use the metal rushes to the mold with the help of ingates which are also called as gates. At the end of the sprue you will see a runner well. Now this is gating system what is there. Another element a riser is there which is placed at the hot spot in the casting which is now it is not shown in the figure but which is very important element as part of whole casting. Now you see at the boat ends there is some extension is provided. This extension helps us to reduce to reduce the proper flow if it is not occurring and plus the turbulence which if it all occurs. Now coming what are the goals what are the major roles what we will see of the gating system. The main important role is to minimize turbulence to avoid trapping gases into the mold. As we know the metal when it starts flowing it has a huge turbulence and with the help of proper gating system the turbulence can be avoided and if gases are present that also with the help of gating system we can remove it otherwise these gases will create large number of defects and finally we need to throw away the castings or we have to revert the castings. Second to get enough metal into the mold cavity before the metal starts to solidify. As we know there is some solidifying there is shrinkage occurs for all metals so one of the goal of the gating system is to provide enough metal to the casting before the metal starts to solidify. Second to avoid shrinkage as I already told you. The next important goal of gating system is to establish the best possible temperature gradient in the solidifying casting so that the shrinkage if occurs may be in the gating system not in the required cast part. As we know if the casting has some defects internally it has to be thrown away. Now this kind of possible temperature gradient can be helped with the help of two first if the gating system is designed in a positive powerful manner so this can be avoided otherwise in other cases chills are been used which helps us to provide the temperature gradient. Second as we know when the metal flows throughout the system it carries some amount of debris or non-metallic inclusions and if that debris be the past of the casting it will lead to defect or the functioning can affect. So the important goal of once again the gating system is to incorporate a system for trapping the non-metallic inclusions so these are the five important gating system functions or we can say the goals of gating system. Now we will understand what are the different types of gating system before that we will understand what is gating ratio. Now gating ratio it is defined as ratio of sprue area to total runner area to total ingate area on the basis of this gating system may be classified as pressurized gating system and non-pressurized gating system. First we will look at what is pressurized gating system the total cross section area if it decreases towards the mould cavity it leads to pressurized gating system. As we can easily see or understand that cross section area if it decreases towards the mould cavity a pressure is being created so it is termed as pressurized gating system. Now back pressure is maintained by the restriction of metal flow then the important part is flow of liquid volume is almost equal from all gates back pressure helps in reducing the aspiration of sprue always runs full because of restriction the metal flows at a high velocity leading to more turbulence and charges and chances of mould erosion so this is one of the disadvantages of pressurized gating system. Now we look at what is unpressurized gating system the total cross section area in this case increases towards mould cavity restriction is only at the bottom of the sprue flow of liquid volume is different from all gates aspiration in the gating system as a system never runs full so this is one of the disadvantages of unpressurized gating system and there is less turbulence now think if the gating ratio is defined as 1 ratio 2 ratio 4 which type of gating system it is called references you can refer NPTEL PLGEN principles of foundry technology and NPTEL's latest lecture courses thank you.