JPH0339775B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method of manufacturing a casting mold suitable for manufacturing a pair of split molds having concave molding surfaces by precision casting.

(Prior art) In order to manufacture a pair of split molds with a concave molding surface called a cavity mold by a casting method, each mold is usually cast separately. Due to causes such as variation and warping of the cast product, warping occurs on the dividing surface during mold matching, and dimensional errors in the molded surface mating part often increase, causing problems in terms of dimensional accuracy. It was hot.
For this reason, the conventional method has had the disadvantage that processing for dimensional correction after casting requires a lot of time.

(Problems to be Solved by the Invention) The present invention solves the above-mentioned conventional problems and provides a method for manufacturing a casting mold that can cast a pair of split molds having concave molding surfaces with high dimensional accuracy. It was completed with the purpose of

(Means for Solving the Problems) In manufacturing a pair of split molds having concave molding surfaces by a casting method, the present invention uses a pair of preliminary split molds whose shape is transferred from a master model so that their molding surfaces face each other. After integrating these pre-split molds with a cutting allowance of 0.1 to 10 mm on the split surface, a ceramic mold is formed inside the pre-split mold by a composite molding method, and the pre-split molds are molded into a ceramic mold. After releasing the mold, the ceramic mold is placed in a flask and molten metal is poured into it to produce an integrally cast product, and then the integrally cast product is cut at a portion corresponding to the cutting allowance to form a pair of split molds. It is characterized by this.

Next, the present invention will be explained in more detail by using as an example the manufacturing process of a split mold for manufacturing a shift lever boot for an automobile as shown in the drawings.

(Example) First, as shown in FIG. 1, a master model 1 with dimensions that take into account the shrinkage of the cast product is created, and this is set on a master base 2 with the dividing plane cut off as shown in FIG. 2. It is preferable that this master base 2 is provided with a protruding boss 3 for facilitating positioning work in a subsequent process. Next, as shown in Fig. 3, a preliminary divided mold 4 whose shape is transferred from this master model 1 and master base 2 with silicone rubber
The master model 1 is pulled out from the master base 2 with the master model 1 fitted into the preliminary divided mold 4, and then a preliminary divided mold 5 is manufactured which is also transferred using silicone rubber as shown in FIG. After the preliminary split molds 4 and 5 obtained in this way are once separated, a sheet 6 with a thickness of 0.1 to 10 mm is pasted on the split surface excluding the molding surface as shown in FIG. 5, and the molding surfaces are made to face each other. In this state, they are integrated again to form an integral preliminary mold 7.

Next, as shown in FIG. 6, a ceramic mold 8 is made inside the integral preliminary mold 7 by a composite molding method. This ceramic mold 8 has a work layer made of a material in which the molten metal comes into contact with the molten metal during casting 8a is made of a material mixed with about 10 mm thick zircon-based refractory as an aggregate and ethyl silicate as a binder. It is made of a material with water glass added as a binder. The thus obtained ceramic mold 8 is separated from the integral preliminary mold 7, subjected to primary firing with a gas burner, and set in a casting flask 9 consisting of a work layer 9b and a backing part 9c made of the same material as shown in FIG. Perform secondary firing at 900℃. After that, for example, carbon steel cast steel (JIS
By casting a material (equivalent to SCC5), a monolithic cast product 10 is produced in which a pair of concave molds are integrated with their molding surfaces facing each other and a cutting allowance of 0.1 to 10 mm is provided on the dividing surface, as shown in Figure 8. obtain.

After annealing this integrally cast product, through-holes 11 are formed in the four corners thereof in a direction perpendicular to the dividing surface, and the cutting margin is cut by, for example, a wire cutting method, and the cut surfaces are ground. By removing the cutting allowance, a pair of split molds 12, 12 having concave molding surfaces as shown in FIG. 9 can be obtained. Note that such a pair of split molds can be easily matched using the previously provided through hole 11 as a reference.

(Function) As explained above, the present invention manufactures an integrally cast product in which two molds are integrated with their molding surfaces facing each other and with a cutting allowance of 0.1 to 10 mm provided on the dividing surface. After that, the splitting surface is cut to obtain two split molds, so the surface accuracy of the splitting surface of each split mold depends on the machining accuracy of the cut part, making it difficult to use conventional individual castings with large warpage. Comparatively, higher surface accuracy can be obtained. Further, in the present invention, almost no dimensional errors in the molding surface matching portions of the divided molds occur because the integrally cast product is divided. As a result, when a pair of split molds with the outside diameter of the split surface of approximately 240 mm x 220 mm are manufactured by the individual casting method, it is difficult to reduce the maximum dimensional error (maximum gap amount) of the split surface to 0.5 mm or less. However, according to the present invention, 0.05
It is possible to make it less than mm.

In addition, in the present invention, the cutting allowance is set to 0.1 to 10 mm because if the cutting allowance is less than 0.1 mm, cutting becomes difficult, and conversely, if the cutting allowance exceeds 10 mm, the number of man-hours for cutting increases and the distance between the two molds increases. This is because dimensional errors occur due to variations in shrinkage.

(Effects of the Invention) As is clear from the above description, the present invention is capable of casting a pair of split molds having concave molding surfaces with high dimensional accuracy. As a manufacturing method for molds, it has an extremely large contribution to the development of industry.

[Brief explanation of drawings]

The drawings all show the steps of the embodiment of the present invention; Fig. 1 is a front view of the master model, Fig. 2 is a front view showing the state in which the master model is set on the master base, and Figs. 3 and 4 are The figure is a cross-sectional view showing the manufacturing process of the preliminary split mold, Figure 5 is a cross-sectional view showing the integral preliminary mold, Figure 6 is a cross-sectional view showing the process of manufacturing a ceramic mold from the integral preliminary mold, and Figure 7 is a cross-sectional view showing the process of manufacturing the ceramic mold from the integral preliminary mold. A cross-sectional view showing the process of manufacturing an integrally cast product using a mold, FIG. 8 is a cross-sectional view of the obtained integrally cast product, and FIG. 9 is a cross-sectional view of a pair of split molds obtained by cutting this. be. 1: Master model, 4, 5: Preliminary split type,
7: Integral preliminary mold, 8: Ceramic mold, 10: Monolithic cast product, 12: Pair of split molds.

Claims (1)

[Scope of Claims] 1. In manufacturing a pair of split molds having concave molding surfaces by a casting method, a pair of preliminary split molds whose shapes have been transferred from a master model are placed so that their molding surfaces face each other, and these preliminary split molds are 0.1 on the parting surface of the mold
After integrating with ~10mm cutting allowance,
A ceramic mold is formed inside the mold by a composite molding method, and after being released from the preliminary split mold, the ceramic mold is placed in a flask and molten metal is poured into it to produce an integrally cast product. A method for manufacturing a casting mold, characterized in that a part of the integrally cast product corresponding to the cutting allowance is cut to form a pair of split molds. 2. The method of manufacturing a casting mold as set forth in claim 1, characterized in that the integrally cast product is cut after forming a vertical through hole in the dividing surface.