 Hello friends, myself, Dr. N. S. Kartikar, Assistant Professor, Department of Mechanical Engineering, Valachandra Institute of Technology, Solapur. Today, we are going to see the discussion and presentation on Welding of Plastic, Part 3. The learning outcome of this presentation. At the end of this session, the student will be able to understand the need and importance of welding of plastics. Student will be able to apply welding techniques in real time. The content of the presentations are containing the following topics. Initially, we will see the introduction in general. Need of Welding of Plastics, Classification of Plastic Welding, Friction Welding, one of the type of plastic welding, another type laser welding. In the introduction, let us see the little bit discussion about the plastic material. Need of plastic material for the various products, the plastic part manufacturing and their categorization. As we know, for any particular product, rather the product design, the material, material selection is the very important critical stage. In consideration with all the advantages and their optimized properties, the material is get selected for the fulfillment of working and environmental condition of that particular product. The plastic material is carrying the n number of positive optimized properties. Like the various properties concerned with moldability that is easily moldable, non-magnetic, bad conductor of electricity, non-corrosive and so on. Because of the same, the plastic material can be selected for the fulfillment of various needs of the products. Whenever the plastic part manufacturing is to be considered, it is going to be produced either as a single part, single product or it can be considered after joining the distinct raw material plastic elements or produced plastic elements. Need of welding of plastics. As we had seen just now, every individual part produced by the different means may be of plastic material is required to be get connected, joined together so that a useful product will be there and that can be used for the required conditions. So summarizingly, need of welding of plastic that is for assembly, repair and maintenance for packaging, the dissimilar material joining processes and to fulfill the need of situation. Now the joining of plastic can be fulfilled by the different means like mechanical joining. So in that we had seen earlier also with the nut, bolt, screws, pin rivets, we can go with the mechanical joints. The second one is the adhesive bonding. With the various kind of chemical adhesives, the plastic can be joined together and the third one is important one which we have to discuss for few of the types that is the welding. With the intentional addition of heat, energy or particularly and or pressure, we are going to join the two distinct plastic elements. At this stage of this session, I am going to ask one question to you, a little bit small task. Are you able to recall, share some of the application of welding of plastic joints which you had used or seen earlier anywhere in real time? Just think about an endless. I suppose we had enlisted the various products where you had seen the welding of plastic. Classification of plastic welding. Welding process can be categorized by two means, external heating and internal heating. In the external heating, the convection and conduction of heat energy is going to be carried out for particularly welding purpose where the hot tool, hot gas, extrusion, implant induction and so on types are there. In internal heating, the conversion of mechanical energy into heat energy through the maybe for example surface friction is going to be used for joining the two distinct elements. Those are categorized like ultrasonic, friction, laser which we are going to see few of the type of the same. Now out of that, let us go with the friction welding. The friction welding of thermoplastic also called as the spin welding is based on the same principle as that of employed for welding metals. In this process, one of the substrates is fixed and while the other is rotated with the controlled angular velocity. When the parts are pressed together, friction heat causes the polymer to melt and weld is created on after the cooling. Let us see this particular diagram where you can see that the blue, the blue part, plastic part is clamped over piece which is stationary one and the rotating element is here you can visualize in a green color. So one element is fixed, another element is in a rotary condition, it is in rotary condition. When this particular element is in rotary condition, it is going to be pressed, it is going to be pressed, applied pressure will be there to the weld surfaces and after specific period of time the heat energy generation will be there and the weld joint can be possible. The friction welding further, major welding parameter includes the rotational speed, friction pressure, force pressure, weld time and burn off length. These are the major parameters which are further required to be controlled. The four main variations are linear welding, orbital welding, spin welding and angular welding depending on the particular nature of weld joints either of the welding variation can be used over there. Let us see the advantages of the friction welding, high welding quality and simplicity and reproducibility of the process. The similar materials can be joined very easily, particularly useful in the aerospace where it is used to join lightweight aluminum stock to the high strength steels. Some of the limitations of friction welding, it is suitable only for applications in which at least one of the components is circular and requires no angular alignment, joint design limitations, impossibility of forged workpieces consisting of non-forgeable materials, difficulties associated with experimental materials, cost of FRW equipment is high and high capital cost is there. Let us see some of the applications. It is used to make the thermoplastic manifolds for the automotive industries, cryogenic fluid piping and containment vessels also. The one of the second type we will see that is laser welding. There are two modes of laser beam welding, first is surface heating and second one is through transmission infrared, which is very well known as TTIR welding. In the surface heating, the surface of the component to be joined are heated by direct laser exposure for a sufficient length of time to produce a molten layer, usually for 2 to 10 seconds. Once the surface is fully melted, the laser tool is withdrawn from the between the parts. The parts are forced together and the melt is allowed to solidify. This particular diagram is going to be self-explanatory regarding the laser welding. As we know the laser, the beam laser is going to be used to produce or to transfer the heat energy to the expected surfaces and very precisely the particularly heat energy generation can be controlled. Now here the advanced one of the welding technique, laser welding you can see over here that is the two pieces are shown over here and this is the laser beam focal spot is there and one is transparent polymer another is absorbing polymer. So moving direction you can see that linearly this laser beam is going to be transferred from one end to the other end and this weld seam is going to be took place over here in the second case also you can see that wherever this laser beam stuck to the in between surfaces of two plastic sheets over here the heat energy generation and as it travels it is going to be carrying out the seam welding as such. The TTR welding it is based on the concept of passing laser radiation through one of the component to be welded. While having the second component absorb the light at the interface, this absorption results in heating and melting of the interface and allows the part to be welded. Semiconductor diode lasers are typically used in plastic welding wavelength in the range of 808 nanometer to 980 nanometer can be used to join the various plastic material combinations. Power levels from less than 1 Watt to the 100 Watt are needed depending on the material thickness and desired process speed. Sample list of material that can be joined polypropylene nylon ABS and so on. Advantages it is a preassembled method speed and flexibility are the advantages it can be weld unsupported internal walls with a complex curvature no micro nozzles to get it clogged because of the same no liquid or fumes to affect the surfaces no consumables and higher throughput time is there. Limitation one of the component must be relatively transparent that is the major limitation. In the application let us see the specific application includes the sealing or the welding or joining of cathode back, the medical container, atom while remote control keys, hard pacemaker casings, syringe temper evident joints and so on. Few of the references for these presentations are as follows. Thank you.