GB1397821A - Moulding method and apparatus - Google Patents

Abstract

1397821 Making moulds for casting AKITA KK 18 April 1972 [27 April 1971 (2) 25 June 1971] 17902/72 Heading B3F A method of making a metal-casting mould comprises providing a mask 12, 14 (of soft or rigid synthetic resin) having a surface complementary to a surface of an article to be moulded, the opposite surface being backed by compacted heat-resistant particulate material (e.g. silica sand) and holding the mask against the material by reducing the air pressure therein. (Additional holding is obtained by the sand biting into the mask). Figs. 5 and 6 show the 0À02 mm. thick vacuum-formed synthetic resin masks 12, 14. The wooden, plaster of Paris, synthetic resin or metal patterns 4, 8, Fig. 8, are located backto-back by projection 16 and the masks 12, 14 located thereover. (Alternatively, they may be formed directly on the patterns). Flasks 18, 19 are then placed over the patterns and sand supplied through holes 20, 21. Presses 26, 27 are then advanced, the press-heads each having a ventilated plate 30, a coarse filter 32, a fine filter 34 and a ventilated plate 38. Compacting may be effected by, or increased by, vibrators 49, 50. The holes 20, 21 are closed and suction is applied through pipes 42, 43 thus holding the masks against the sand. The patterns are then removed, the mould parts moved together and the metal poured. Finally, air is re-introduced into the flasks and the casting removed, the unbonded sand dropping away. In a modification, a pattern 51 of wood, plaster of Paris, synthetic resin or metal, Fig. 14, is coated by vaporization in a vacuum chamber with a film of synthetic resin, the pattern having openings in its surface communicating with a central vent 54. Flasks are then brought together around the pattern and filled through openings 62, by blowing or pouring, and vented through ports 58. The flasks are evacuated of air through the vents 58 after covers 62 have been positioned. Instead of the covers 62, extensions of the masks 55 may be folded over. In a further modification, a sheet 76, Fig. 19, is laid over a filled flask and a shape impressed therein by a press 77, Fig. 19. In another modification, the mask consists of a bag 94, Fig. 25, placed within pattern halves 91 and vacuumformed. A perforated vent-pipe 95 covered with a filter 97 is then inserted. The internal space is filled with silica sand and then evacuated of air to form a core. The patterns may be coated with a release silicone. Modifying surface of casting.-The masks may be coated with powdered graphite, zirconium, or aluminium to affect the skin of the coating.