JPS63192534A - Molding method for mold - Google Patents

Abstract

PURPOSE:To make sound mold having high strength by covering a film after packing molding sand, sucking the molding sand toward surface direction of pattern and pressurizing to the molding sand from upper part of the film. CONSTITUTION:The molding sand 8 is packed in a space for packing the molding sand, while making inside of the packing space 1 for the molding sand to negative pressure by working a sucking device. Next, the upper opening part of the molding sand 8 is covered by the flexible film 9, and the molding sand 8 is sucked toward surface direction of the pattern 3 by working the sucking device. The molding sand 8 is pressurized and made to hard by four pieces of stamping rods 10, etc., moving by a piston vertically and shifting to front and rear direction. After that, the stamping rods 10, etc., are taken out, and the heating gas is supplied on the molding sand 8 to shape the mold. In this way, the molding sand can be packed at high density even in the narrow space in the packing space and the sound mold having high strength can be made.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for making a mold used for manufacturing a casting. In particular, the present invention relates to a mold making method that has good filling properties with molding sand.

[Conventional technology]

There are various methods for making a mold, but there is a method in which a binder is added to the foundry sand, and the foundry sand is sucked into the space formed by the combination of the mold and the mold (in other words, the method described above). A method of supplying and filling the space with negative pressure may also be adopted. This method is particularly often used when forming a mold by supplying a gas or heating a catalyst to harden the binder. and,
When molding is performed by heating, it is necessary to add a liquid curing catalyst to the foundry sand in addition to the binder.

[Problem that the invention seeks to solve]

However, when a binder is added to foundry sand as described above, its fluidity generally tends to be poor, making it difficult to densely fill the narrow gaps (four parts of the model) in the space. If the molding sand is insufficiently filled, the strength of the mold in this part will be weakened, and defects will easily occur in the castings manufactured using this part.

[Means for solving problems]

The present invention was made with the aim of solving the above-mentioned problems in the mold making method by suction filling molding sand. a filling step of filling molding sand containing a binder; a suction step of covering the upper open part of the filled molding sand with a flexible film; and a suction step of sucking the molding sand toward the surface of the model; The present invention provides a method for making a mold, comprising a pressurizing step of applying pressure to the foundry sand from above the flexible film.

To carry out the method of the present invention, first, a molding sand filling space formed by a combination of a casting flask and a model is filled with a molding sand containing a binder for molding sand and, if necessary, a hardening agent (hardening catalyst). Carry out the filling process to fill with sand. In carrying out this filling step, the molding sand filling space is normally made to have a negative pressure as in the conventional method, molding sand is supplied there, and the supplied molding sand is sucked toward the surface of the model. Note that this filling step may be carried out without making the molding sand filling space negative pressure.

Next, a suction step is performed in which the upper opening of the filled molding sand is covered with a flexible film and the molding sand is sucked toward the surface of the model. The material of the flexible film used in this suction step is not particularly limited as long as it is not damaged by the foundry Sunagawa binder, and various plastic films such as polyvinyl chloride, polyethylene, and polypropylene, or Various natural and synthetic rubbers can be used. Since this film is subjected to external force and strongly pressed against the foundry sand in the pressurizing process described below, it is preferable to use rubber, which has high elasticity among the above materials. It is more preferable to use a material that has good mold releasability from the binder, such as silicone rubber. Further, the suction of the foundry sand in this suction step can be performed in the same manner as in the above-mentioned filling step.

In the method of the present invention, while performing the suction step, a pressurizing step is performed in which pressure is applied to the foundry sand from above the flexible film. When the pressurizing process is performed while the suction process is being performed in this way, the synergistic effect of the suction action and the pressurizing action will cause the narrow void in the casting filling space (
The molding sand can be filled with high density even in the model recesses.
A strong and healthy mold can be produced.

When applying pressure in the pressurizing step, in order to ensure high-density packing as described above, it is preferable to
It is preferable to apply pressure intermittently and locally at least from above the molding sand filled in the model recess in the molding sand filling space, and intermittently and locally from above the filled molding sand. It is best to apply pressure locally.

Moreover, it is particularly preferable that the pressure in the above-mentioned pressurizing step be applied using a tamping rod that moves up and down.

To explain in detail the case in which the above-mentioned pressurizing step is carried out using a tamping rod, first, the material of the tamping rod used may be any material as long as it has appropriate strength, and various metals, wood, plastics, etc. may be used. be able to. There are no particular restrictions on the shape of the tamping rod, but since the tip of the tamping rod will be strongly hit against the film, it should preferably have a shape that does not easily damage the film, such as an arcuate shape. Further, the number of tamping rods to be used is not particularly limited, and may be appropriately selected depending on the size and shape of the mold to be molded.

The above-mentioned pressurizing step using a tamping rod can be performed manually, but it is preferable to use a pressurizing device that incorporates a tamping rod into a cylinder and automatically moves the piston. When carrying out the compaction process, in addition to making sure that a particular tamping rod always tamps only one point, the tamping rod can also be moved to the left, right, back and forth, or in a circular motion to tamp different points. You may try hardening it. When compacting only one point, it is effective to position a narrow gap (model recess) to be filled with molding sand as described above directly below or near the point to be compacted.

In any case, the above-mentioned tamping work should be done manually or by a machine, the position of the tamping rod should be fixed or variable over time, or the timing of the vertical movement of the tamping rod ( The degree of intermittent timing of the pressurizing force can be appropriately selected in consideration of the size and shape of the mold to be molded, the required molding speed, etc.

In addition, in the method of the present invention, after the pressurization step as described above,
The process of removing the flexible film, sucking up the foundry sand again, and supplying a flame, heated gas, etc. from a gas burner to the foundry sand from above the foundry sand can be carried out as necessary.

Next, a preferred embodiment of the mold making method of the present invention will be described with reference to FIG.

In Fig. 1, 1 is a molding sand filling space formed by a combination of a casting flask 2, a model 3, and a surface plate 4, and 5 is a molding sand filling space arranged below the surface plate 4, and the molding sand is A suction box 7 that makes the inside of the sand filling space 1 a negative pressure is a suction port to which a suction device (not shown) is connected to reduce the pressure of the suction box 5 .

To carry out the present invention, first, the suction device is activated to create a negative pressure in the molding sand filling space 1, and the molding sand 8 containing a binder and a hardening agent for molding sand is poured into the molding material. Fill the sand filling space 1.

Next, the upper open part of the filled molding sand 8 is covered with a flexible film 9, and while the molding sand 8 is sucked toward the surface of the model 3 by the operation of the suction device, from above the flexible film 9, Four tamping rods 1 that move in the vertical direction and in the front-back direction (direction perpendicular to the page)
The molding sand 8 is tamped with the tamping rod 10 of the pressurizing device having a pressure of 0, and an external force is reliably and intermittently applied to the model recess 1) in the molding sand filling space 1, and the molding sand 8 is tamped into the model recess 1). Fill.

Thereafter, the pressurizing device including the tamping rod 1o and the like is removed from the flask 2, the flexible film 9 is removed, the molding sand 8 is sucked again, and heated gas is applied from above the molding sand 8 to the molding sand. By supplying molding sand 8 to molding sand 8 and leaving it for several minutes to bind molding sand 8, molding sand 1 is sufficiently applied to the model recess 1).
It is possible to obtain a strong and sound mold filled with .

As mentioned above, in order to make the piston movement of the tamping rod 1o in the vertical direction and to move it in the front and back direction, the tamping rod 1o is
0 are each fixed to a cylinder 13 for driving a tamping rod that is vertically installed on a cylinder support plate 12, and the cylinder support plate 12 is fixed to the lower end of a height adjustment cylinder 14, and is movable in the front and rear direction. However, the mechanism for pistoning the tamping rod 10 and the mechanism for sliding the cylinder support plate 12 are not particularly limited, and any mechanism commonly used to generate such movement may be used. Just use it. Further, numeral 15 is a mounting portion for the pressurizing device placed on the flask 2.

〔Example〕

An example of the present invention will be described below.

Example 1 Mogami No. 5 silica sand was used as the foundry sand, a urea-modified furan resin was used as the binder, an aqueous acid solution mainly consisting of xylene sulfonic acid was used as the curing agent, and a silicone rubber film was used as the flexible film. It was carried out according to one embodiment described above using the apparatus shown in the figure. As a result, model recess 1
) was also sufficiently filled with molding sand 8 to obtain a strong and sound mold.

〔Effect of the invention〕

As described above, the mold making method of the present invention applies pressure from above to the molding sand containing a binder in the molding sand filling space while suctioning it. For example, due to the synergistic effect of the suction action and the pressurizing action, the molding sand, which generally has poor fluidity, can be filled with high density into the narrow voids (model recesses) in the molding sand filling space. Therefore, a strong and healthy mold can be produced.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram for explaining one embodiment of the present invention.

Claims (4)

[Claims] (1) A filling step of filling a molding sand filling space formed by a combination of a molding flask and a model with molding sand containing a binder for molding sand, and covering the upper opening of the filled molding sand with a flexible film. and a suction step of sucking the molding sand toward the surface of the model, and a pressurizing step of applying pressure to the molding sand from above the flexible film. Method. (2) The method for making a mold according to claim (1), wherein the pressure in the pressurizing step is applied intermittently and locally from above the molding sand filled in the model recess in the molding sand filling space. . (3) The method for molding a mold according to claim (1), wherein pressure in the pressurizing step is applied intermittently and locally over the entire filled molding sand. (4) The mold making method according to any one of claims (1) to (3), wherein the pressure in the pressurizing step is applied using a plurality of tamping rods that move up and down.