Molding lost-core

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

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. 

Other recent modifications include lost-core injection molding and gas-assisted injection. The former involves inserting in the mold a low melting metal alloy insert over which the polymer is injected. After solidification and ejection of the part, the insert, which has a melting point lower than that of the polymer, is melted away to yield a hollow part. Gas injection also makes it possible to manufacture hollow parts. After injection of a small volume of polymer, but before its solidification, gas is injected in the mold through a different gate. The gas pushes the molten material... 

This technology is also called fusible core molding, soluble core technology (SCT), lost-wax molding, loss core molding, etc. This technique is a take off and similar to the lost wax molding process used... 

Different materials can be used for bladders, giving larger, equal, or smaller diameter than the largest diameter of the hollow component. These can be fixed (polyolefins) or flexible (silicones) and an auxiliary core can be used to pre-drape the reinforcement. It is possible to match the possible variations to each specific molding project. IKV tested a number of options in transparent (polymethyl methacrylate) molds, looking also at lost core systems, in which the bladder or core remains in the hollow molding, and possibilities of automation. 

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. ... 

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. 

The generally rotationally symmetrical mold, which gives the final component its shape, is called the mandrel. It is either directly or with the aid of special adapters fixed to the driving spindles of the winding system (three jaw chucks). Mandrels can be reusable (depending on the component geometry) or remain in the finished part as so-called lost cores . 

Generative processes are also used to produce cores and molds for sand casting, lost models, molds for investment casting, and master models for a variety of molding processes, preferably in soft (silicone) molds. Molds for sand and investment castings are not discussed in the context of this book, molding techniques are discussed in Section 1.11. 

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