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. 

These improvement potentials lay in different technologies (Polymer Polyamide routes, Adipic acid - Hexamethylenediamine, lost core/twin shell. Aluminum Form of anode (only of interest at primary production), cleaning step during recycling, recycling material percentage)... 

FIG. 2. EB cured honeycomb structure fabricated with Lost Core tooling. 

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... 

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. ... 

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)... 

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 . 

This technique is where components are placed in an injection mould and are then moulded over with another material. The term over-moulding covers both insert moulding and lost core moulding. This technique is not confined to plastics and over-moulding of metal inserts, such as to produce scissor handles and plastics on ceramics is commonplace. 

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. 

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