Transfer molding preforming technique

Preformed material is placed on mold or into mold feeder mechanism Molding by compression, transfer, or injection techniques... 

Dow-United Technologies Composite Products Inc (Dow-UT), Wallingford, Connecticut, developed an advanced resin transfer molding (AdvRTM) process for production of complex and flight-critical airframe and engine structures in RPs. The process has been further developed to improve the quality of RP aerospace components substantially at the point where two or more sections are molded together. A patented technique of shaped unidirectional fiber preforms... 

Resin transfer molding (RTM) n. A variation of matched-metal-die molding in which, after placing the preformed reinforcement in the heated mold, premixed, quickcuring resin is injected while the mold is closing or after it has closed. The technique has been used to make body parts for specialty cars and aircraft components. 

Little preforming is required for transfer molding, which is used for the production of very small parts. However, this technique often requires excessive amounts of material. Flow requirements are high, but fluorocarbon elastomers are available that can be used with this technique. 

A recent development of the dry-laid techniques can be ascribed to the preformed GMT produced by a fluidized bed process [3]. In this case, fiber rovings are cut and mixed with thermoplastic powder, conveyed and deposited by air stream onto a mold. The loose web formed on this mold is heated by hot gas stream prior to being transferred to a matched die compression mold. So, in this case, the web (i.e. the GMT preform) is consolidated and formed simultaneously in the compression molding... 

With the extrusion blow stretch process, the parison is shaped and temperature-conditioned in a preform cavity in the same way a bottle is extrusion blow-molded. From this preform cavity, the parison is transferred to the bottle cavity where a rod and air pressure combine to stretch and expand the resin. PVC is most oft n stretch blow-molded with this process. Although the one-step method is the most common (see Fig. 39), a two-step technique, in the same fashion as the others, is feasible. 

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