 Hello friends, myself Dr. N. S. Kartikar, Assistant Professor, Department of Mechanical Engineering, Valachandra Institute of Technology, Solapur. Now we are going to see the presentation on Welding of Plastics Part 2. At the end of this session, students will be able to understand the need and importance of welding of plastics. Students will be able to apply welding techniques in real time. The content for the presentation goes as follows. Introduction, need of welding of plastics, classification of plastic welding, external heating category, one of the type we will discuss, hot gas welding, internal heating category, we will discuss one of the type ultrasonic welding. Let us see, initially in the introduction the discussion about plastic material, need of plastic material products and the plastic part manufacturing particular categories. As we know the plastic material is the advanced material which is hydrocarbon polymer material because of many advantageous properties of the same nowadays is used for many wide applications. The advantageous properties like that can be easily moldable, it can be reshaped, it is having non-corrosive property, non-magnetic properties and it is also a bad conductor of electricity and so on. So with this particular n number of advantages properties, the plastic material is going to be used as a product material in many cases. Now let us see the plastic part manufacturing is going to be there by two means. One is a particular product rather the part can be manufactured as a singular element that will fulfill the need of the required as per the requirement. In the second case as we know there are limitations for manufacturing a singular product by its geometry size and other specifications. With the same limitations we are going to discrete a product into number of small elements in which those particularly elements are required to be manufacturing separately and after all it is required to assemble together for the expected working of that product. Thus the need of welding of plastic is in the areas like in the assembly case, in the repair and maintenance, in packaging for joining dissimilar materials and many a times to fulfill the need of situation. Joining of plastics can be go with the different means like mechanical joining in which the various fasteners like nut, bolt, screws, pins, rivets, keys are used for joining the two distinct plastic material elements. The second case the adhesive bondings different adhesives are used for joining the two distinct plastic elements and the third one which we are going to discuss in detail that is about the welding. At this stage of this session I am going to ask one question to you. Are you able to recall or share some of the applications of welding of plastic joints which you had used or seen earlier anywhere in real time? Just think about and enlist. I hope you had enlisted the list of various product where you have found the number of applications of welding in plastic elemental material. Let us go with classification of plastic welding. Welding process are categorized by heating method that is used. Two general categories are there external heating and internal heating. External heating it rely on conviction and conduction to heat the weld surfaces. For example, hot tool, hot gas, extrusion, implant induction, implant resistance welding and so on. In internal heating it rely on conversion of mechanical energy into heat through the surface friction. Further divided into internal mechanical, internal electromagnetic heating, ultrasonic, friction, laser welding and so on. Let us see one of the subtype initially hot gas welding. This is similar to oxyacetylene welding of metals. The only difference is that open flame of oxyacetylene welding is replaced by a stream of hot gas. This layer nitrogen, hydrogen, oxygen or carbon dioxide is heated by an electric coil as it passes through a welding gun. The process invented in the mid of 20th century uses a stream of heated gas usually air to heat and melt both the thermoplastic substrate material and thermoplastic welding rod. To ensure welding take place adequate temperature and pressure must be applied to the rod along with the use of the correct welding speed and gun positions. These are the some of the images, photographs for hot gas welding. You can observe in the first image look at to the cursor that in the right hand the welding gun is hold through which the hot air or hot gas is applied to the base material as well as the filler material which is hold into the particular left hand. The filler material is normally present in the form of wire itself. So, likewise the particularly weld run that means filler material is going to filled into the cavity of two distinct elements. Manually many a times this process is continued for the fulfillment of welding joints. Advantages easy to use thermoplastic can be welded easily whereas limitations are slow manual process cannot be used in mass production. It can be fabricate the pipelines, pond liners, wide varieties of vessels, small items like a chemical tanks, water tanks, heat exchanger, plumbing fittings and so many. Let us go with the second subtype of the welding ultrasonic welding. This method uses mechanical vibration to form the joint. The vibrations are of high frequency. The parts to be assembled are held together under pressure between the oscillating horn and an immobile anvil and are subjected to ultrasonic vibrations of frequency 20 to 40 kilohertz at right angle to the contact area. Alternating high frequency stresses generate heat at the joint interface to produce a good quality weld. Ultrasonic welding is divided into two major groups near filled and far filled. Near filled the distance between the horn and the weld interface less than 6 millimeter whereas far filled the distance between the horn and the weld interface is greater than 6 millimeter. This is the conceptual setup diagram of ultrasonic welding the image number one where you can see that ultrasonic welding consists pneumatic piston which is connected to the transducer further connected to the controller in between the sonotrode and horn the booster is there and everything is controlled and monitored through the power supply unit. On the anvil you can see the two distinct elemental plastic material pieces are kept over here yellow and pink. This sonotrode tip and horn is going to directly contact with this plastic material jobs with the frequency with the rubbing action the heat is generated you can see in the image number two how the particularly heating zone will be visualized is like this. This is the third image example of particularly welding setup and likewise high frequency generates the heat energy and converts the solid state plastic into the plastic state plastic and under a pressure there will be a fusion and joint can be fulfilled. Ultrasonic welding advantages used in mass production because the welding time are relatively short and also applicable for both amorphous and semi crystalline thermoplastic can be used to bond dissimilar material whereas limitations horn size is limited to design constraint the process and tool must be adopted to the material to be welded applications food packaging computer components challenging and critical applications is the standard disposable butane a lighter etcetera references for this presentation are as follows thank you.