Casting vacuum

Vacuum casting is a variation of sand casting, is used for aluminium alloys and is known in the industry as V-casting. The process uses dry 

In parts where amounts of entrapped air must be kept to an absolute minimum, the process may be carried out under full vacuum. The unit consists of two chambers, one for mixing the prepolymer, curative, and other ingredients, and the lower chamber for the mold. 

The mixing is done under vacuum, and the fully degassed mix is poured into the mold using remote handling equipment. As both chambers are under vacuum, there is no air to be displaced and the mold is filled completely with no entrapped gasses. In certain units, the mix can be pressure-transferred to 

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After another short mixing period ( 15 min) the expl compn is poured into the desired molds. Vacuum casting has not been found necessary to obtain good density, provided that the mold design is not too intricate or the height-to- diam ratio not too great (Ref 38)... 

The method of choice for the preparation of Pu metal on the multigram to kilogram scale is metallothermic reduction of PUF4 or PUO2 by Ca metal (69), followed by electrorefining with TaC electrodes and vacuum casting. This method produces metal 99.9 at % pure. An... 

The mixture leaving the apparatus must be de-aerated. The air is removed from the solid s-liquid dispersion by a centrifugal separator before the propellant is vacuum cast and cured. 

L.Jameson, "Electrical Measurements in Detonating Pentolite and Composition B , BRL Memo Rept 1371 (September 1961) 33)W.Kegler, Ex-plosivst 1961, 2, 27-30 (Examination of vacuum -cast RDX-TNT charges) 34)US Military Specifications ... 

Quickmix. A production system, developed by Rocketdyne, for the manuf of composite pro-pint. The solid ingredients, such as oxidizer and fuel additives, are placed in a dilute slurry with a low viscosity, volatile and immiscible carrier. These slurries, a minimum of two, and the fluid polymer and curing agent streams are metered to a continuous fluid mixer. The effluent from the mixer then flows to a separator and vacuum casting site where the carrier must be removed from the diluted proplnt... 

The heptane is removed by decantation and the proplnt is vacuum cast into a mod or motor. 

Pouring liquid metal into the mold requires a steady hand and constant attention. When the mold containing liquid metal is placed in a centrifuge, hot metal can fly out of the centrifuge. This is why it is preferable to use the vacuum casting method, for which a centrifuge is not needed. 

One essential difference between casting and molding processes is that pressure need not be used in casting (although large-volume, complex parts can be made by low pressure and/or vacuum casting methods). Another difference is that the starting material is usually in liquid form rather than the usual solid plastic used in other processes. There is also the difference that the liquid could be a monomer rather than the plastic used in most other processes and in turn the monomer is converted to a polymer/plastic (Chapter 1). 

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