Casting processes simple

Fig 9 3 A simple laboratory set-up for observing the casting process directly. The mould volume measures about 50 X 50 X 6 mm. The walls are cooled by putting the bottom of the block into a dish of liquid nitrogen. The windows are kept free of frost by squirting them with alcohol from a wash bottle every 5 minutes. 

This is the earliest and the most commonly used casting process. It has the advantages of wide metal suitability, low cost, and simple operation. It uses sand as a refractory material. Many types of sand are utilized by the foundry industry. However, because of its wide availability and relatively low cost, silica sand is the one that makes most metal castings. Silica sand is composed of the mineral quartz (Si02), which has a fusion point of approximately 1670°C (3090°F), which is often lowered by the presence of appreciable quantities of minerals with lower fusion points. 

The mechanical setup of the doctor blade tape casting process is shown in Figure 4.7. In this process, the slip is deposited in excess on the carrier surface, typically in a confined reservoir. The carrier surface is then moved under the doctor blade, which wipes the excess material back into the reservoir, leaving a thin layer of fluid on the carrier. The mechanics of the doctor blading process are, in theory, quite simple. In practice, however, controlling all of the variables to... 

Simple shoe molds made from cast aluminum or tin alloys are filled from the top in a casting process. In case of the closed mold filling (Figure 1.130), the two-parted... 

Slush molding is a simple variation of the casting process. The low-viscosity material, such as, plastisol is poured into a hot mold and after a thick casting is formed on the wall of the mold cavity, the excess material is poured out. In order to ensure uniform coating, the mold is often rotated. 

Preparation of films can be achieved by two main processes the "wet" and "dr) approaches. The "wet process" involves biopol5mier dispersion or solubilization in a film-forming solution (solutioncasting) followed by a second step, the suspension or film-forming solution is placed in a suitable mold and the solvent is evaporated under controlled conditions (Ciannamea et al., 2014 Hernandez-Izquierdo and Krochta, 2008). The result of the casting process depends mainly on the mixing conditions temperature, time, type and concentration of solvent, plasticizer and pH, and the dr nng relative humidity and temperature (Gallstedt et al., 2004). Most of the studies on polysaccharide-based films use this method because it is simple, reproducible in most laboratories, and useful as a first approximation to the formation of edible films. 

Although the continuous casting of steel appears deceptively simple in principle, many difficulties are inherent to the process. When molten steel comes into contact with a water-cooled mold, a thin soHd skin forms on the wall (Eig. 10). However, because of the physical characteristics of steel, and because thermal contraction causes the skin to separate from the mold wall shortly after solidification, the rate of heat abstraction from the casting is low enough that molten steel persists within the interior of the section for some distance below the bottom of the mold. The thickness of the skin increases because the action of the water sprays as the casting moves downward and, eventually, the whole section solidifies. 

The encapsulation of electrical components provides an interesting extension to the use of plastics materials as insulators. Components of electronic systems may be embedded in a single cast block of resin (the process of encapsulation). Such integrated systems are less sensitive to handling and humidity and in the event of failure the whole assembly may be replaced using seldom more than a simple plugging-in operation. Encapsulation of miniaturised components has proved invaluable, particularly in spacecraft. 

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