JPH0147267B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for making a mold using foundry sand mixed with a water-soluble binder.

In recent years, there has been a problem with the disposal of used foundry sand, a rise in the price of synthetic resin binders, and problems such as the generation of foul-smelling gases, harmful gases, and corrosion of these devices in the shell molding method, cold boxing method, hard boxing method, etc. Problems such as touching are occurring. For this reason, the molding method using water-soluble glue as a binder has recently been reviewed, and various improvements in this type of molding method have been proposed. However, in both cases, the mold hardness is insufficient, and when increasing the amount of water-soluble binder added to increase the mold hardness, the fluidity of the sand decreases and the filling properties of the sand deteriorate, and the casting process due to gas defects. There were problems such as defects occurring, and furthermore, the drying and curing time became longer, which lowered productivity, and mold costs increased due to the increase in the amount of binder.

The present invention was made in view of these problems, and an object of the present invention is to provide a mold making method that can obtain a mold with high hardness without increasing the amount of water-soluble binder added. It is something to do.

The present invention will be explained below based on examples.

As shown in FIG. 1, a casting flask 2 is placed on the upper surface of a wooden model board 1, and the molding board 1 and the casting flask 2 are placed on top of the wooden model board 1.
Foundry sand S (hereinafter referred to as foundry sand) is prepared by adding and kneading water-soluble binders such as roasted dextrin, oxidized starch, alpha starch, starch ester, starch ether, and high amylose into the space defined by ) was packed while compacting to fill the molding sand S to a predetermined density, and after raking the top surface of the molding sand S so that it was approximately flush with the top surface of the flask 2, as shown in FIG. A plate material 5 has a sheet packing 3 attached to its lower surface, a plurality of ventilation holes 4 penetrating through the bottom surface of the sheet packing 3, and a vent plug (not shown) embedded in the ventilation holes 4.
is placed on the upper surface of the casting flask 2 via the sheet packing 3 in an airtight manner, and the model plate 1 with model, the flask 2, and the plate material 5 are integrally inverted, and a model is made from the molding sand S. Release the attached model plate 1 (third
figure). At this time, since the foundry sand S is packed to a predetermined density and the viscosity of the water-soluble binder acts between the sand particles, even if the model plate 1 with model is released from the mold, It never loses its shape. Next, as shown in FIG. 4, an aqueous solution of a water-soluble binder or an aqueous solution of a water-soluble binder and heat-resistant aggregate mixed in an appropriate ratio is sprayed onto the mold surface of the foundry sand S using a spray device 6. and let it permeate uniformly onto the mold surface of the foundry sand S. After coating, a cover member 8 equipped with an air supply hole 7 is placed to cover the molding sand S in the flask 2, and then normal temperature or heated compressed air is supplied into the cover member 8 through the air supply hole 7. The compressed air passes through the molding sand from the surface of the molding sand impregnated with the aqueous solution and is exhausted to the outside from the vent hole 4. In this way, when compressed air is passed into the molding sand from the mold surface for a predetermined period of time, the molding sand is dried and hardened sequentially from the mold surface, and eventually a mold M in which the entire mold is dried and hardened is formed. In particular, the hardness of the surface of the molding sand impregnated with the aqueous solution is much higher than that of the inside of the mold. After that, plate material 5
As shown in FIG. 6, the cover member 8 is removed and the other half of the mold, which has been hardened and molded in the same manner as described above, is stacked to form a pair of completed molds. In addition, as shown in Fig. 7, it can also be used as a back-up type mold M' in which the ventilation time of compressed air is shortened and only the mold surface of the molding sand S impregnated with the aqueous solution is hardened and the unhardened portion is removed. good.

In addition, in the above embodiment, the model plate with model 1
The molding sand S is placed in the space defined by the flask 2 and the molding flask 2.
Although the material is packed to a predetermined density while being compacted, it may also be filled to a predetermined density by blowing, squeezing, vibration, etc. Further, in the above embodiment, after inversion, the model plate with model 1 was released from the molding sand S, an aqueous solution was applied to the mold surface of the molding sand S, and then the molding sand was dried and hardened. However, after filling the space defined by the model plate 1 with model and the flask 2 with molding sand S to a predetermined density, the model plate 1 with model is inserted without inverting the flask 2. It is also possible to immediately release the mold from the molding sand S, apply an aqueous solution from below the molding flask 2 to the mold surface of the molding sand S, and then dry and harden the molding sand S from the mold surface.

As is clear from the above description, according to the present invention, the space defined by the model plate with model and the casting flask is filled with molding sand containing a water-soluble binder. After cutting out the mold, on the mold surface of the foundry sand,
An aqueous solution of a water-soluble binder or an aqueous solution containing a water-soluble binder and a heat-resistant aggregate in an appropriate ratio was applied almost uniformly, and then the foundry sand was dried and hardened. The mold surface of the foundry sand can be molded to a predetermined mold hardness using a water-soluble binder, and since there is no need to use a large amount of a water-soluble binder, the fluidity of the foundry sand is improved, and teeth,
It has the effect of eliminating casting defects due to gas defects and contributing to improved productivity, making it a significant contribution to this type of industry.

[Brief explanation of drawings]

FIGS. 1 to 7 are process diagrams showing an embodiment of the present invention. 1: Model board with model, 2: Casting flask.

Claims (1)

[Claims] 1. After filling the space defined by the model plate with model and the casting flask with molding sand mixed with a water-soluble binder to a predetermined density, the model plate with model is removed from the molding sand. While releasing the mold, an aqueous solution of a water-soluble binder or an aqueous solution containing a water-soluble binder and a heat-resistant aggregate in an appropriate ratio is applied to the mold surface of the foundry sand.
A mold making method characterized by applying the foundry sand substantially uniformly and then drying and hardening the foundry sand.