Molding automation

This work is supported by Taiwan Green Point Entaprise Co., Ltd., Mold Automation Education Resoiu-ce Center, Ministry of Education, Taiwan, and National Science Council in Taiwan (Grant NSC 95-2627 - E - 033-001)... 

More complex shapes can be made by cold isostatic pressing (CIP). CIP uses deformable mbber molds of the required shape to contain the powder. The appHcation of isostatic pressure to the mold suspended in a pressure transfer media, such as oil, compacts the powder. CIP is not as easily automated as uniaxial pressing, but has found wide appHcation in the preparation of more complex shapes such as spark plug insulators (26). 

Traditionally, this process has been utilized primarily for simple soap bars because it tends to be time-consuming and thus somewhat limited for large-scale bar production. However, advances have been reported in automating this approach (14). Furthermore, the process requires fluid cmtcher compositions for flow into the molds. This typically requires the formulation to contain either a high level of solvents, including water, glycerol, and alcohol, and be at elevated temperatures (>80° C) when poured into the frames. Despite these limitations, it has proven to be the preferred route to producing certain specialty products, for example, transparent bars. 

In this process, resin is injected into a closed mold containing the reinforcement preform. The resin can be injected either under pressure [22] or under vacuum [23]. The potential advantages of this process are (I) low mold cost, (2) inserts can be incorporated, (3) low pressure requirements, (4) accurate fiber orientation, (5) automation possibilities, and (6) versatility. The resin formulation and process variables are selected so that no significant polymerization occurs until the mold cavity has been completely filled. This is achieved by the ad-... 

Thermoplastic RPs (RTPs), even with their relatively lower properties when compared to thermoset RPs (RTSs), consume about 55wt% of all RP products. Practically all of the RTPs are injection molded with very fast cycles using short glass fiber producing highly automated and high performance products. 

For higher throughput applications, injection-molded plastic microtiter plates have served as the formats of choice for automated assay development. Thermoplastics such as polystyrene, polycarbonate, and polypropylene are used for a variety of purposes including storage and assay plates, lids, pipette tips, and Eppendorf PCR tubes. Polystyrene plates are used for cell culture and ELISAs. Polycarbonate reagent bottles are popular, while polypropylene storage plates and PCR tubes are standards. 

Figure 18.11 contains a sketch of an extrusion blow-molding scheme. Here a heat-softened hollow plastic tube, or parison, is forced against the walls of the mold by air pressure. The sequence of material introduction into the mold and subsequent rejection of the material from the mold is generally rapid and automated. Approximately 1 million tons of thermoplastics are produced by this technique annually. 

Several layers of dry, continuous-strand mat, woven roving, or cloth called preform are placed in the bottom half of a two-part mold, either by a hand-layup or by an automated technique (see Figure 7.90). The mold is closed, and a catalyzed liquid... 

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