GB621854A - Improvements in methods of making dies for casting or moulding articles - Google Patents

Abstract

621,854. Moulding processes; patterns. AHERNE, J., SHAW, J., and HOCKING, L. N. Jan. 19, 1946, No. 1890. [Class 83 (i)] Dies, e.g. for making wax injection models for casting turbine blades, are made by forming templets 10, Fig. 4, having contours complementary to the cross-section at successive points along the length of a die, assembling the templets in a jig 12, filling in the intermediate spaces, and taking a casting of the face thus formed. The templets may be made by photographic reproduction from enlarged drawings on to sensitized metal plates 1, Fig. 1, the drawings preferably including split lines 6, 7 and die datum lines 4, 5 and cutting out, each templet including the cross-sectional form A of the article so that the lower templet is cut along the line 2 as shown in Fig. 3. Each templet may be checked by projection on to the enlarged drawings and corrected by filing. The templets are held against flanges 14 of the jig by a plate 15 and screws 16, a machined model 17 of a turbine blade root is added if desired, and plaster of Paris is filled in and strickled to the contour of the templets. Casting processes.-This assemblage B is inverted and attached to the head 22, Fig. 23, of a press by which it is lowered or pressed into a bath 25 of tin-bismuth or other low-melting- point metal preheated by a thermostaticallycontrolled resistance and then cooled by circulated fluid. This casting forms one of the required dies and the other may be made in the same way but, to avoid difficulty in matching the split lines 6, 7 it is preferably made from the assemblage B by cutting a slot adjacent each templet 10 to receive the corresponding upper templet 30, Fig. 11, these being held by a bar 32. Casting composite articles.-A casting 36, Fig. 12, is made, as before, from this assemblage, the templets 30 becoming embedded in the casting. The machined root 17 is then removed from the assemblage B and placed in its print P in the casting 36, plaster is strickled to the contour of the templets 30 as shown in Fig. 13 and a casting 37 is made, as before, from this to form the second die.