Casting gating system

The process steps are depicted in Figure 2.38. They begin with the manufacture of expendable wax patterns, by injecting molten wax into an aluminium or epoxy die to form a pattern that is virtually an exact replica of the desired casting. The wax may contain fillers. For smaller castings, several wax patterns are attached to a wax gating system. Water soluble die release agents are used to facilitate the wax model take-out. 

Figure 2.49 Casting with running and gating system [237, HUT, 2003]...

Electrodeposition, casting, photoetching, and spark erosion are used to provide textured mould surfaces. The faithful reproduction of a textured surface is obtained with a low resin viscosity and good elasticity to permit the withdrawal of the textured surface. The role of the taper will be increased in these cases, as well as the gating system, since merging flow fronts can cause surface defects on the moulded product. 

With use of gating systems several castings in a single mold possible. 

With sand casting, probably the most common method, ordinary sand is used as the mold material. A two-piece mold is formed by packing sand around a pattern that has the shape of the intended casting. A gating system is usually incorporated into the mold to expedite the flow of molten metal into the cavity and to minimize internal casting defects. Sand-cast parts include automotive cylinder blocks, fire hydrants, and large pipe fittings. 

The gating and riseting system for cast aluminum bron2e is extremely important and must be arranged to iatroduce the metal quietly at the lowest portion of the mold. The alloys shrink well hence the gating and riseting must be well adapted to the particular casting. See Table 12 for properties of these alloys. Alloys C 95300, C 95400, and C 95500 are heat-treatable for iacreased mechanical properties and the last two should be temper-aimealed if used ia a corrosive environment. 

The final example is shown in Fig. 10.86. Several workers are breaking gates off of castings on the conveyor by hand. Much dust is generated by this operation and the dust rises due to buoyancy. To remove the dust, an exterior hood was placed beside the conveyor and a supply inlet was placed above the workers. The supply airflow is blown toward the breathing zone of the workers and the dust source. In this case, as the workers and the dust source are located within the supply airflow, the airflow functions to supply the workers with clean air and to transport the dust toward the exhaust inlet. The velocity of supply air is relatively low, 1.1 m s , and the exhaust velocity at the hood face is 2.75 m s . The dimensions of the system are indicated in the figure, and the depth of the device is 6.0 m (compare with Sections 10.3.3 and 10.4.6). 

Pur-Fect Tool . [Ciba-Geigy] Polyurethane casting system used for assembly jigs, backfilling, core boxes, foundry gates and risers, laminating molds, mold cores, pattern plates, prototypes. 

CEHW [such as Field-Programmable Gate Arrays (FPGAs), Application Specific Integrated Circuits (ASICs), and other custom micro-coded devices] are often just as complex as S/W-controlled microprocessor-based systems (CAST-27 paragraph 2a). 

Alkali breakdown is usually carried out as a simple batch operation in mild-steel, cast iron or stainless-steel vessels. The reaction products may assume the form of a viscous paste and suitable agitation is necessary to maintain intimate mixing. The design of stirrer system is simpler than for breakdown by concentrated sulphuric acid since corrosive fumes are not present to attack bearings or motors, etc., and corrosion of the stirrer blades and vessel by the reactants or products is also much less serious. A simple gate stirrer of mild steel or stainless steel is usually satisfactory. The reaction vessel may require to be tipped if the products are solids or viscous pastes, but in other circumstances a bottom outlet might be satisfactory. 

The gating and riser system is attached to the part and fixed in a mold box with tape (Figure 1.278). Thereafter, the casting frame with the initial model is filled with the silicone mass (Figure 1.279). These are special impression materials which have a low viscosity and do not create air voids and air pores in the silicon molds. 

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