JPS5927266B2 - Double-sided pressure molding method and equipment - Google Patents

Description

[Detailed Description of the Invention] In recent years, molds for mass-produced castings have been made using various high-pressure molding machines that are uniform, dense, and capable of high-speed molding due to demands for improved dimensional accuracy and productivity of products. ing.

Most of these high-pressure molding machines apply pressure from the top surface of the mold (opposite the model surface), so the pressure is increased (10~
30 kg/crrr) and using a vibrator or jolt at the same time.

Furthermore, in order to make the density of the mold uniform, a multi-segment type squeeze head is used so that the squeeze head conforms to the shape of the model.

As a result, the molding equipment is exposed to excessive pressure and vibrator.
Alternatively, a large-scale foundation that can withstand the impact of the jolt is required, and the working environment is significantly degraded by the noise of the vibrator or the jolt.

The disadvantage of such a high-pressure molding machine is that it pressurizes the area farthest from the casting surface where uniform, high-density filling is most needed, so it is necessary to compensate for the transmission loss of pressurizing force and filling due to the molding sand. This is caused by increasing the pressurizing force and using a vibrator or jolt in combination.

These drawbacks become more noticeable as the size of the mold increases, and there is a limit to the size of the mold that can be molded.

The present invention relates to a molding method which improves the above-mentioned drawbacks of high-pressure molding machines, and which produces uniform and densely packed molds with low pressure and little noise.

The present inventors conducted various tests on pressure transmission and filling properties of foundry sand, and as shown in Fig. 1, the pressure transmission rate gradually decreases as the layer thickness of foundry sand, that is, the height of the mold, increases. It has become clear that the degree of filling of foundry sand tends to decrease suddenly at a certain depth from the pressurized surface.

Looking at this at a depth of 250 mm from the pressure surface, it can be seen that approximately 65% of the pressure is transmitted, but almost no molding sand is filled.

Based on the above findings, the present inventors have developed a method of molding that can be applied even when the size of the mold is increased, by applying pressure to molding sand from both the model surface and the top surface, using low pressure and without deteriorating the working environment. Invented a method for molding.

In general, casting molds are required to have strength to withstand handling and molten metal pressure, and ventilation to exhaust gas generated during casting. The main requirement is air permeability.

However, the strength of the mold increases as it is more densely filled with molding sand, and the air permeability decreases; therefore, it is difficult to effectively adjust both properties.

However, in conventional molds that are formed only by applying pressure from the top, the filling of molding sand from the pressure surface to the casting surface becomes rough, and although the casting surface has good air permeability, its strength is low. Cast products are susceptible to casting defects such as sand encrustation, washing, and burning.

In addition, by increasing the pressure and using a vibrator or jolt to make the molding sand densely filled, the strength of the casting surface can be increased (
However, the air permeability in the center of the mold decreases, making it easier for gas defects to occur in the product.

Furthermore, judging from the degree of filling of molding sand shown in FIG. 1, no matter how high the pressing force is, the filling is not carried out beyond a certain depth.

This suggests that there is a limit to the height of the mold that can be molded, but at the same time it shows that sufficient molding is possible even with a small pressure depending on the pressurizing method.

On the other hand, according to the pressurizing method of the present invention, since pressure is applied from both the model surface and the upper surface of the mold, the casting surface and upper surface are filled with molding sand to a depth of 100 to 150 mm, providing sufficient strength and forming the mold. Since the filling in the center is rougher than the surface of the mold, the strength is somewhat reduced, but a sand inch-shaped mold with good air permeability is formed.

In addition, since it is not necessary to apply the filling of molding sand to the center of the mold, there is no loss of pressing force or filling due to the molding sand, and therefore it is possible to reduce the pressing force (surface pressure) and at the same time create a mold that can be molded. There is no limit to the height of

Next, the present invention will be explained with reference to FIGS. 2 to 8.

The structure of the present invention will be explained with reference to FIGS. 2 to 4.
is the upper squeeze head, which is connected to the rod 2 via the spherical seat 3, and the rod 2 is rotated by a hydraulic motor 5 by a rotation angle preset on the rotation angle detector 4 according to the shape of the model, and the rod 2 is raised and lowered. let

A plurality of upper squeeze heads having the above structure are installed on the upper frame 12 of the molding machine.

This structure uses multiple upper squeeze heads to pressurize the foundry sand at an arbitrary height depending on the shape of the model, and any mechanism that has this kind of action can be applied to this device. .

For example, as shown in FIG.
are connected internally and connected to the same external pressure source, and when the molding sand 8 is pressurized, the pressure inside the cylinder 15 and the reaction force applied to the upper squeeze head 1 are the same. A mechanism in which the position of the head 1 changes according to the shape of the model 9, or as shown in FIG. When actuated by another cylinder 17 connected to the source and pressurizing the foundry sand 8,
A mechanism or the like may be considered in which the position of the upper squeeze head 1 changes according to the shape of the model 9 so that the pressure inside the cylinder 16 and the reaction force applied to the upper squeeze head 1 are the same.

Reference numeral 6 denotes a flask fixing device, which can be adjusted according to the height of the flask 7 by a hydraulic cylinder or screw mechanism.

10 is a lower squeeze head which has a mechanism to stop at an arbitrary position of the lower frame 13 according to the amount of compression of the molding sand, and is installed in the lower frame 13 by a cylinder 11, and the molding sand is squeezed through the model 8 or directly. Pressurize.

14 is a support for the molding machine. Next, the molding method according to the present invention will be explained with reference to FIGS. 5 to 8.

First, the casting flask 7 is carried into a predetermined position in the molding machine, and the model 9 is
After fixing the upper surface of the lower squeeze head 10 on which the molding sand 8 is installed at a position lower than the lower surface of the flask by the amount of compression of the molding sand, molding sand 8 is introduced.

(Figure 5). Next, the flask 7 is fixed with the flask fixing device 6, and then the hydraulic motor is rotated to the scale of the rotation angle detector set according to the shape of the model 9, and the father squeeze head 1 is set to the hydraulic or pneumatic pressure, etc. When raising and lowering with
is lowered to pressurize the foundry sand 8 (Fig. 6).

Then, with a certain time difference, lower squeeze head 1
0 is raised until the upper surface of the molding flask T is approximately at the same position as the lower surface of the flask T, and the molding sand 8 is pressurized (FIG. 1).

After the molding sand 8 is pressurized, the upper squeeze head 1
At the same time, the lower squeeze head 10 is gently lowered to remove the mold, and then the flask fixing device is raised,
Carrying the mold out of the molding machine (Fig. 8) In the present invention, as described in detail above, molding sand is molded by pressurizing it from above and below, so that only the surfaces that require strength are filled uniformly and densely. Although the strength of the center of the mold is lower than that of the surface of the mold, a mold with good air permeability can be obtained.

In addition, since the model surface is directly pressurized, there is no need for devices such as vibrators or jolts to tightly fill the molding sand, which reduces noise and improves the working environment.
The structure of the molding machine is also simplified, and large-scale foundation work is not required.

Furthermore, since pressure is applied directly to the surface that requires strength, there is no loss of pressure force due to pressure transmission from the molding sand, and a mold similar to the conventional high-pressure molding method can be produced with a small pressure force.

[Brief explanation of drawings]

Figure 1: Relationship between the depth from the pressurizing surface, the pressure transmissibility of the sand, and the dust filling of the sand, Figure 2: Front view (partial sectional view) of the device according to the present invention, Figures 3 to 4 : A sectional view of the upper squeeze mechanism according to the present invention, FIGS. 5 to 8: Process diagrams of the molding method according to the present invention. 1... Upper squeeze head, 2... Rod, 7... Casting flask, 8... Molding sand, 9
...Model, 10...Lower squeeze head, 15,16...Cylinder.

Claims (1)

[Claims] 1. Lower the lower squeeze head on which the model is placed into the frame from the bottom surface of the flask by a height corresponding to the amount of compression of the molding sand, then pour in the molding sand and fix the flask. After this, a plurality of upper squeeze heads are lowered and a lower squeeze head is raised to perform pressure molding from both the upper and lower surfaces of the mold. 2. A plurality of upper squeeze heads with a mechanism that can pressurize the foundry sand by independently varying the amount of descent according to the model shape, and a plurality of upper squeeze heads that can be stopped at any position within the frame depending on the amount of compression of the foundry sand. A double-sided pressure molding device comprising a lower squeeze head having a mechanism capable of pressurizing foundry sand and a plurality of flask fixing devices installed at positions facing the upper surface of the flask.