Billet Molding

Relatively simple equipment is used for billet molding. It consists of a stainless steel mold and hydraulic press for fabrication of the preform, and an oven for sintering. A lathe and skiving blades are required for preparation of film and sheet. 

With sheet molding, the procedures are very similar to those used as described above for billet molding except for the shape and size of the molding. This process is used for sheeting above 2.5 mm (0.1 in.) up to large blocks. The latter are used for a block method skiving operation similar to that used traditionally for cellulose nitrate. 

Magnesium alloys are available in a variety of metal forms, including cast ingots, slabs, and billets sand, permanent-mold, die, and investment castings forgings extmded bars, rods, tubes, stmctural and special hoUow and soHd shapes and roUed sheet and plate. Magnesium alloys are used widely in a great variety of appHcations. 

Converters who manufacture EPS parts and components for packaging are called shape molders. Others who mold large billets, eg, measuring 0.6 X 1.2 X 2.4, are called block molders. The package user can obtain EPS parts without the benefits of a mold parts can be fabricated from billets by... 

Molding. Mol ding is the older of the two forming methods and is used to form products ranging in size from bmshes for motors and generators to billets as large as 1.75 m diameter by 1.9 m in length for use in specialty appHcations. 

The precerammed billets, already having appropriate tooth color, are loaded into a dedicated high temperature press and transfer-molded at 1100°C into phosphate-bonded molds. 

In a continuous casting machine, molten steel is poured into a reservoir at the top of the machine. It passes at a controlled rate into a water cooled mold where the outer shell of the steel becomes solidified. The steel is drawn down into a series of rolls and water sprays, which ensure that it is both rolled into shape and fully solidified at the same time. At the end of the machine, it is straightened and cut to the required length. Fully formed slabs, blooms, and billets emerge from the end of this continuous process. 

FIGURE 4.1 Mold assembly for small to medium size billets. (Reprinted from Compression Moulding, Technical Information, with permission from DuPont Fluoropolymers)... 

FIGURE 4.2 Compression molding press for PTFE billets. 

Two principal PS foams that are fabricated are extruded foam and expanded for molded foams. PS foams are light, closed-cell foams with low thermal conductivities and excellent water resistance. They provide for low-temperature insulation and buoyancy media. The extruded PS foam is fabricated as billets and boards. They are made by extruding molten PS containing a blowing agent, under elevated temperature and pressure, into the atmosphere, where the mass expands. Billets and boards can be used directly or can be cut into many different forms.254... 

In a typical molding procedure the molding powd is heated in a steam oven at 112° for 2—4 hrs, then pressed to shape at 120° using 30000psi with 5mins dwell time under a vac of at least 4mm. A billet of PBX is thus produced with a compressive strength of at least lOOOOpsi (Refs... 

To prepare billets for the solid-state extrusion experiments, the materials were injection molded at 15 to 30 °C above the respective melting temperature. The billet materials... 

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