Fabricated sheet metal mold

Figure 15.8 Fabricated sheet metal mold (upper and lower halves). (Courtesy Rivers Metal Molds, Inc.)...

Cast aluminum is the most widely used mold material. Small to medium articles are molded with a cast mold. Cast aluminum has good heat transfer, and is cost-effective when several moldings of the same article are required. Cast molds can be porous, however, and are easily damaged. Sheet-metal molds are normally used for larger parts. They are easy to fabricate frequently the sections of the molds only have to be welded together. Sheet-metal molds are cost-effective for large articles. Other molds, such as electroformed nickel molds, give a product... 

Figure 12-10 An example of an injection-molded one-piece housing (left) that replaced a fabricated sheet-metal housing (right) where many separate parts were required and had to be assembled.

Sheet metal can be used to produce prototype and production molds. They are often used when a single cavity mold is required to produce large cavities. Sheet metal molds are frequently fabricated in-house by custom molders. The various pieces of the mold are welded together. Their advantages include lightweight and uniform thin walls. 

Another fabrication methodology is via the freeze drying (FD) method. The aqueous solution of gelatin is obtained via sonication as described in flie previous section. However, the solution in this case is not foamed by frothing as described in Fig. 3.12. Instead, the silica aerogel granules are mixed in the solution for about 10 min till a tacky mix is obtained. Thereafter, the mixture is casted onto a 100 mm diameter petri dish or in a metal mold of 75 mm x 50 mm by 25 mm laid witii a porous sheet. The composite mold is covered with transparent porous foil and... 

As with blow molding, the process is capable of producing very large three-dimensional shapes such as those found in recreational equipment and agricultural tanks. Because rotational molding operates with open molds at essentially ambient pressure, tooling is economical and can be fabricated from sheet metal. 

Use Calendered sheet and film extruded and molded items electrical wire insulation coatings for wood, metal, fabrics, and paper. 

Notable among the thermoplastic materials are polyethylene, polypropylene, polyvinyl chloride, the styrene synthetic rubber blends, the acrylics, and the fluorocarbons. Notable among the thermosetting reinforced materials are the polyesters, epoxy, and the furan resins as custom-made reinforced materials, and the phenolic and epoxy resins molded, filament-wound, and/or extruded with reinforcement. AU these materials are available as piping, sheet stock, and miscellaneous molded and fabricated items. These materials, particularly polyvinyl chloride, polypropylene, and reinforced polyesters, are now being used extensively for ventilating ductwork in handling corrosive fumes. They have proved to be economically improved over metals such as stainless steel, lead. 

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