FOUNDING. The art of making molds in sand, loam or plaster of Paris, with or without the aid of patterns. The molds thus made are filled with molten metal which is subsequently allowed to cool and solidify into a metal casting corresponding to the form of the mold.
The various founding processes are charac terized by the kinds of metal employed in the castings, such as iron, steel, brass, bronze, etc., and by the class of work produced, such as water pipes, car-wheels, ordnance, statues, bells, etc., involving the applications of special meth ods in the work of molding; in the melting of the metal; in the filling of the mold with the molten metal; and in the manner in which the metal is allowed to cool.
Molding in Sand.— The process of mold ing in sand by means of patterns embedded in flasks containing sand, is substantially as fol lows: The flasks, which are box-like arrange ments provided with suitable handles by which they may be lifted and moved around, are gen erally used in pairs—the upper flask being commonly designated the °cope,* and the lower one, the °drag' or "swivel.) The pafterns, usually of wood, are made either in one piece when the design of the casting is simple, or in several pieces when the form of the casting is more complicated. In molding, the drag is filled with sand and the pattern embedded in it. The cope is then placed over the drag and the sand rammed in tightly around the pattern. The pair of flasks is then turned over and the loose sand taken out of the drag and replaced by sand firmly rammed in its place. The flasks are now returned to their original position; the cope is taken off and the pattern removed. The cope is then replaced upon the drag, and the mold is thus made ready to receive its filling of molten metal. This is accomplished by pour ing the metal through suitably formed gates or holes which extend through the cope and con nect with the molded spaces in the drag.
The use of a separate appliance for a drag is very often dispensed with, the pattern being embedded in a bed of sand upon the foundry floor. This method is especially applicable when a large number of small castings are made at each pouring. Also, very often the patterns are made in two parts, that is, divided in the mid dle horizontally, so that one-half of the mold is made in the drag and the other half in the cope. In the case of hollow cylindrical castings such as water pipes and the tubes of heavy ordnance, a cylindrical core of the proper di mensions is suspended in the drag mold before the cope is placed in position, and the annular space between the core and the interior walls of the mold is filled in with the molten metal.
Molds are made either in green or in dry sand. Those in green sand are suitable for the making of small and simple castings; but molds in dry sand are employed in the produc tion of castings of large size and great intricacy of design. In such cases, after the molds have been finished, they are placed in drying ovens until they are thoroughly dried.
Molding in In this process: the molds instead of being made by the embedding of patterns in sand, are formed by means of cores of metal or of brickwork which are covered by several coatings of loam — mixed sand and day, to correspond with the form and dimensions of the desired castings. An outer shell constructed around the core thus thick ened, provides the annular space for the re ception of the metal. The method is especially applicable to the founding of hollow cylinders, bells and statues. Consult Sharp, 'Modern Foundry Practice'(190D) ; Hall, 'The Steel Foundry' (1914). See FOUNDRY AND FORGE SHOP TERMS.