1 - Primitive instancing: (Solid Modelling)
(Old)
The modeling system defines a set of primitive 3D solid shapes that are relevant to the application area.Primitive instancing is often used for relatively complex objects, that are tedious to define in terms of boolean combination of simpler objects, yet are readily characterized by a few high level parameters.In primitive instancing no provisions are made for combining objects to form a new higher level object.Thus the only way to create a new kind of object is to write the code that defines it.Similarly the routines that draw the objects or determine their mass properties must be written individually for each primitive.
(James D. Foley, computer graphics: principles and practice,p:539)
(New and better)
The pure primitive instancing technique is based on considering an object that has the same topology as a potential primitive (also called generic primitive) but different geometry. By predefining the topology of the primitives, the user is required to provide only the geometry of an object and the family to which it belongs. For example, a bolt can be defined by bolt (number of sides, length, pitch, diameter) the other dimensions are generated automatically and the topology is predefined. This scheme is basically the philosophy of group technology. It is easier to use and create unambiguous and unique solids.
the main disadvantage is clearly the limited domain of objects that can be handled. The method is restricted to the primitives predefined in the system and they are quite limited. Another problem is lack of generality to develop any algorithm to infer the properties of the represented solid.
(Computer Aided Design And Manufacturing By Lalit Narayan Et Al., p. 219)
2 - Digital Mock Up: (Computer Aided Design)
(Old)
In particular, digital mock-up (DMU) allows designers to investigate the assembly feasibility of a product and the constraints imposed by manufacturing processes. DMU allows the user to represent the structure of a product and the accurate position of its geometry, and enables a multidisciplinary presentation of assembly processes and analysis (design ‘in context’) such as insertion, view and collision. Through DMU, it is possible to obtain a virtual representation of a product and simulate the shape, function and spatial positioning of its components or subsystems, as well as of the necessary production tools. By providing the basic representation of a product, DMU permits to share the core product data that the different company areas and disciplines use to collaborate.
(Corallo et al., “Digital Mock-up to Optimize the Assembly of a Ship Fuel System”, Journal of Modelling and Simulation of Systems, Vol.1-2010, Iss. 1, page 5)
(New and better)
A major proportion of the development costs of a new car corresponds to prototype building and testing: newest development projects take advantage of DMU to lighten part of this burden with the so called virtual prototypes and virtual tests, providing an enormous advantage through the increasingly detailed graphical representation of real parts.
A DMU system permits the study of the interaction between each component with the assembly, in order to search for potential interference in their final position or during assembly, dis-assembly or motion according to their function. It is therefore a virtual representation of objects supporting the development process of both product and production tools.
(The Automotive Body: Volume I: Components Design By Lorenzo Morello, Lorenzo Rosti Rossini, Giuseppe Pia, Andrea Tonoli, p.69)
3 - Plasma Beam Machining (Types of machining)
(Old)
In
plasma machining a continuous arc is generated between a hot tungsten
cathode and the water-cooled copper anode. A gas is introduced around
the cathode and flows through the anode. The temperature, in the narrow
orifice around the cathode, reaches 28,000°C, which is enough to produce
a high-temperature plasma arc. Under these conditions, the metal being
machined is very rapidly melted and vaporized. The stream of ionized
gases flushes away the machining debris as a fine spray creating flow
lines on the machined surface. The removal rates by this method are
substantially higher than those of conventional single-point turning
operation. Plasma machining systems are divided into plasma arc, plasma
jet, shielded plasma, and air plasma.
(Advanced Machining Processes, Hassan El-Hofy; Page:166)
(New and better)
Plasma beam machining is based on the use of low temperature open plasma, which is applied to increase operational properties of machined components such as wear resistance, corrosion stability, thermal stability, etc. Such an amelioration is carried out in order to attain the formation of functional coatings from corresponding materials, generated by a plasma jet, plasma welding, and plasma depositing. Furthermore, plasma is used in some combined plasma-mechanical processes, in particular in plasma mechanical machining.
(Springer Handbook of Mechanical Engineering, Volume 10 By Karl-Heinrich Grote, Erik K. Antonsson, p.655)
4 - Mechanical Agitation: (Chemistry, Metallurgy)
(Springer Handbook of Mechanical Engineering, Volume 10 By Karl-Heinrich Grote, Erik K. Antonsson, p.655)
4 - Mechanical Agitation: (Chemistry, Metallurgy)
(Old)
Mechanical agitation is necessary when you
must add materials a portion at a time so that they have immediate
intimate contact with the bulk of the solution. Efficient mechanical
agitation reduce the time for completion of reaction, can be used to
control rate of reaction, and improves yields of products.
( Chemical
technicians' ready reference handbook - Greshon J. Shugar, Jack T.
Ballinger, Linda M. Dawkins- page 229)
(New and better)
Mechanical agitation is conceptually simple. For example, a tank equipped with a rotary agitator can be filled with a liquid containing the reactants. Powdered catalysts can be added to the tank and maintained in suspension in the liquid by agitation. This simple case can be illustrated as shown in Fig. 6.20. If a gas phase is also needed to introduce some of the reactants, the gas can be bubbled through the liquid. The technology can be used either for a batch reactor or a conventional or multistage CSTR. In the case of continuous operation, the difficulty lies in separating the catalyst from the reactor effluent and recycling it to the reactor. (Dashed line in figure)
(Chemical Reactors: From Design to Operation By Pierre Trambouze, Jean-Paul Euzen, p.399)
5 - Percussion Welding (Welding, Manufacturing)
(New and better)
Mechanical agitation is conceptually simple. For example, a tank equipped with a rotary agitator can be filled with a liquid containing the reactants. Powdered catalysts can be added to the tank and maintained in suspension in the liquid by agitation. This simple case can be illustrated as shown in Fig. 6.20. If a gas phase is also needed to introduce some of the reactants, the gas can be bubbled through the liquid. The technology can be used either for a batch reactor or a conventional or multistage CSTR. In the case of continuous operation, the difficulty lies in separating the catalyst from the reactor effluent and recycling it to the reactor. (Dashed line in figure)
(Chemical Reactors: From Design to Operation By Pierre Trambouze, Jean-Paul Euzen, p.399)
5 - Percussion Welding (Welding, Manufacturing)
(Old)
The process appears in several forms but in every variation a short-time high-intensity arc is formed by the sudden release of energy stored generally, but not invariably, in capacitors. Subsequently very rapid or "percussive" impacting of the workpiece to form the weld is required. The difference should be noted between this process and the capacitor discharge resistance welding method in which a capacitor is discharged into the primary of a transformer and heat is generated by resistance and not an arc.
The main point of difference between the variations of percussion welding is in the method of initiating the arc. Three methods are used: (1) low-voltage with drawn arc; (2) high-voltage breakdown; (3) ionization by a fusing tip. With each method the energy source can be a bank of capacitor, possibly as part of delay line, which is charged by a variable voltage transformer/rectifier unit. Both charging voltage and capacity are variable so that the energy available and the shape or the current-time curve can be adjusted.
(Houldcroft P.T., Welding Processes, pg.95, Kayra Ermutlu)
(New)
Percussion welding is resistance welding process in which heat required for coalescence is obtained from an intense discharge of electrical energy applied to the locality of the proposed weld for an extremely short time. Pressure is applied percussively (rapidly) during or immediately following the electrical discharge.
Percussion welding machine comprise of means of converting alternating current from the mains into direct current (in the form of a transformer and a rectifier), a storage medium and a suitable spot welder. The storage medium allows electrical energy to be stored and built up until the appropriate moment for welding.
The entire operation of percussion welding is as follows:
The workpieces to be welded are cleaned and clamped into the machine. (Fig 1.27) By application of force, the two workpieces are brought near each other and an arc is struck between the two, which heats the surfaces to be joined. At this point of time, pressure is applied which extinguishes the arc and hold the workpieces together till the weld cools. In this way, the weld is completed. The main advantage of percussion welding is that there is extremely shallow depth of heating and time cycle is very short. The process is used only for butt welding of parts having small cross-sectional areas. The process is useful for welding materials having low resistivity, such as aluminum and its alloys, copper and its alloys, etc. It can be used for welding large number of dissimilar metals.
(Manufacturing Technology, EEE/CHMT International Electronic Manufacturing Technology Symposium, M Adithan, p. 29)
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