Processing lost-core

Soluble core molding The soluble core technology (SCT) is called by different names such as soluble fusible metal core technology (FMCT), fusible core, lost-core, and lost-wax techniques (3). In this process, a core [usually molded of a low melting alloy (eutectic mixture) but can also use water soluble TPs, wax formulations, etc.] is inserted into a mold such as an injection molding mold. This core can be of thin wall or solid construction. 

The Bell/Boeing V22 Osprey tilt-rotor aircraft uses carbon fiber-reinforced polyether etherketone (PEEK) for doors and housings of the engine air particle separator and for fuel vent tanks (Figure 6.44). TP polyimide (TPI) forms the basis for an injection-molded spline adapter in the drive train which tilts the rotors. Costs were reduced some 22%. The parts were developed by RTP Company with Bell Helicopter and molder RAM Inc., Texas. The tanks are molded by the lost core process. 

FIGURE 1.24 Lost-core injection molding process. ... 

Metal Core Technology (MCT), Lost-core molding process, CoreTech Associates, Inc. 

As with thermoset injection molding, heavily fiber-reinforced parts are also molded from thermoplastics. Such parts still may exhibit creep during prolonged mechanical stress, but they are nevertheless considerably stronger and tougher than the nonreinforced products. Glass-reinforced nylon, for example, is used with the lost-core process for a complex air-intake manifold on a current automotive engine. 

FIGURE 1.20 Intake manifold, produced in the lost core process (source BAYER AG, Leverkusen)... 

In this process, a component termed a preform is placed into the tool of an injection moulding machine. A second material is then moulded onto or around the preform. Two methods fall imder this category insert moulding and lost core moulding. 

Table 10.6 Process attributes of lost core moulding ...

As the blackpowder core of a safety fuse bums, it produces gases which must escape. At the same time the heat of the combustion melts the bitumen and plastic and thus produces side venting through the textile layers. This results in the production of an increased but constant gas pressure, determined by the equilibrium between gas generation and gas lost sideways. As the rate of burning of blackpowder depends markedly on the pressure, it is this process of equilibration which determines the speed of burning of the fuse. 

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