JPS599257B2 - Shell mold molding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a shell mold in which a thin portion of the shell mold is reinforced by an additional shell layer.

Conventionally, when molding a shell mold using a dump type mold, corners such as the tip of the protruding part of the mold as shown in Fig. 5 have a low mold temperature, so the mold is in contact with the corner part. The fillet thickness T1 of the molded part to be formed is the thickness T of the other parts.

It has the disadvantage that it becomes thinner than the original, causing peel-back, and casting defects due to deformation. Therefore, in order to increase the fillet thickness T1, it requires a lot of molding time and the shell thickness T of the pond molded portion is increased. There is a problem that the number of shell molds increases more than necessary, which increases the manufacturing cost of the shell mold. The present invention has been made in view of the above-mentioned drawbacks, and it is possible to mold a shell mold to a minimum shell thickness using a dump type mold, and to effectively utilize the high retained heat of the shell mold immediately after molding. By sintering coated sand around the thin-walled parts to form an additional shell layer, we are able to reduce the weight of the shell mold, strengthen the necessary parts, and shorten the time required for molding. purpose.

Hereinafter, the present invention will be described in detail with reference to one embodiment.

As shown in Figures 1 to 4, 1 is a mold for molding upper shell molds 2 such as power transmission shafts in two rows, each having a corner portion 4 at the base 3 and tip. Each of the base parts 3, 3 is attached to a rotary disk 7 having a support shaft 6.

8 is the tip of the shaft forming part 9 of the upper mold shell mode 2;
10 is the additional shell layer, T2 is the build-up thickness of the additional shell layer 10 at the outer periphery of the fillet thickness T1, and T is the fillet thickness T.
1. A safe on the outer periphery of the corner part 4, which is the sum of the build-up thickness T2,
11 is a mold cavity, 12 is a dump box, 13 is coated sand for dumping, and 14 is a lower shell mold formed by another mold.

Reference numeral 15 denotes coated sand for retrofitting, which is stored in a storage tank 16 for application to the molding of the additional shell and layer 10, and the storage tank 16 is installed in a position close to the rotary disk 7.

Next, a method for molding the upper shell mold 2 will be described.

First, the molds 1, 1, .

Next, the opening of the dump box 12 containing the coated sand 13 for dumping at the bottom is directed upward, and the rotary plate is placed so that the molds 1, 1, etc. are placed upside down in the opening. 7 (FIG. 1), the rotary plate 7 is rotated 180 degrees together with the tap box 12 by linking the spindle 6 with an appropriate rotation means (not shown), and the dump coated sand 13 is placed in the mold 1. . The dump box 12 is rotated 180 degrees again to return to its original position (Fig. 3), and the dump box 12 is moved from the turntable 7.
After separating the upper shell molds 2, 2... from the molds 1, 1..., immediately
The cylindrical body 9 of the upper shell mold 2 is formed manually by an operator.
Place the tip 8 of the coated sand 1 in the storage tank 16 for retrofitting.
5 for a short time (for example, 5 to 10 seconds) to form a cap-shaped additional shell layer 1 on the outer periphery of the tip 8 of the shaft forming portion 9.
0 (Figure 4).

In addition to new sand, the coated sand 15 for retrofitting may be sand discharged during dump truck manufacturing.

Incidentally, when an upper shell mold 2 for a power transmission shaft of a motorcycle was tried to be molded according to the procedure of the method of the present invention, the following favorable results were obtained.

That is, since the phenolic resin coated on each coated sand 13, 15 melts at 98 to 102°C, the tip 8 of the shaft forming part 9 of the shell mold 2 can be maintained at a temperature close to the mold temperature. By handling within the specified time, the additional shell layer 10 can be easily formed on the outer periphery of the tip 8 to strengthen the weak fillet thickness T1, so that the shell of other structural parts of the upper shell mold 2 can be easily formed. The thickness can be formed as thin as within the allowable strength range.

According to the method of the present invention, a shell mold is sintered and molded using a metal mold, and the tip of the shell mold is immersed in coated sand stored in a storage tank while the shell mold is still at high temperature. Since an additional shell layer is formed at the tip of the mold, even if the fillet thickness at the tip of the shell mold is insufficient, the strength of the shell mold manufactured by the dump type mold is maintained by the additional shell layer. This reduces the weight of the shell mold by reducing the wall thickness of other structural parts (shell thickness) to the allowable strength, and also improves work efficiency by shortening the time required for molding. Moreover, it has the excellent effect of eliminating casting defects and significantly improving productivity.

[Brief explanation of the drawing]

Figures 1, 2, and 3 (illustrating embodiments of the method of the present invention) are central vertical cross-sectional views showing the operation of the dumb box to which the tap-type mold is attached, and Figure 4 is the additional shell. A vertical cross-sectional view showing the relative position of a storage tank and a shell mold to explain the layer molding process, and FIG. 5 is a central vertical cross-sectional view of the shell mold. 1... Mold, 2... ...Upper shell mold, 8...Tip, 15...Coated sand for retrofitting, 16...Storage tank.

Claims (1)

[Claims] 1. Sintering and molding a shell mold with a metal mold, burying the tip of the shell mold in coated sand stored in a storage tank while the shell mold is still at high temperature, and applying an additional shell layer to the tip of the shell mold. After it was formed,
A shell mold manufacturing method characterized by taking out a shell mold from coated sand.