JPH0471752A - Method for forming hollow core - Google Patents

Abstract

PURPOSE:To increase degree of freedoms to shapes of hollow core to be possible to form and selection of forming methods thereof by shrinking foam resin-made pattern with reaction of petroleum series solvent in hardener contained in sand and the foam resin and forming the hollow part in a core. CONSTITUTION:After setting the foam resin-made pattern 3 to the prescribed position in the core mold 5, and sand 7 packing is executed. The pattern 3 is shrunk with the reaction of the petroleum series solvent in the hardener contained in the sand 7 and the foam resin to form the hollow part in the core 1. Reacted gas and unreacting gas are discharged with the air and introduced to an exhaust cleaning vessel 8 and cleaned. By this method, the hollow core having the prescribed shape can be molded by adopting the optimum molding method under consideration of advantage/disadvantage to the shape accuracy and cost, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a hollow core molding method applied to foundry cores having a hollow part, and in particular, to a method for molding a hollow core using a cold hox method, a self-hardening mold, etc. Concerning methods suitable for molding children.

Conventional technologyThe core, which is placed in a predetermined position in the main mold to create a hollow part in the casting, is made hollow in order to reduce the weight of the core itself and to prevent gases generated during casting. is common.

Therefore, the conventional hollow core molding method will be briefly explained based on FIGS. 4 and 5. Figure 4 shows a molding method using a mandrel (nested core), in which the mandrel 9 is set in a predetermined position of the core mold, and after sand-filled molding, the hollow core l
The hollow part 2 is formed by punching out the mandrel 9 from the mandrel 9. Fig. 5 shows a hollow core molding method using the shell mold method, in which shell sand is blown into a heated core mold 5', and after a certain period of time, the core mold is turned over to remove any unremoved residue inside. By discharging the hardened sand 10, the part where the shell sand was present becomes the hollow part 2 of the hollow core l.

Problems to be Solved by the Invention The conventional hollow core molding methods described above all have the following problems.

In other words, in the case of the first conventional example in which a hollow part is formed by pulling out a mandrel, there are restrictions on the shape of the core to which this can be applied. It was difficult to apply it to objects with complex shapes. For this reason, when the hollow core molding method of the first conventional example cannot be applied, the hollow core is formed by an inverted drop method using the Fermold method, as shown in the second conventional example. However, modeling of hollow cores using this inverted drop method could not be applied when using a cold box method or a self-hardening mold.

The present invention was made in view of the above-mentioned circumstances, and its purpose is to be able to mold a hollow core using a cold box method or a self-hardening mold without depending on the shape of the core. An object of the present invention is to provide a hollow core molding method.

Means for Solving the Problems The present invention solves the above-mentioned problems. After placing a foamed resin model in a predetermined position of a core mold, it is filled with sand, and a curing agent contained in the sand is removed. This hollow core molding method is characterized in that the model is contracted by a reaction between a petroleum solvent and a foamed resin to form a hollow part of the core.

Effect According to the above-mentioned method, a model made of foamed resin is placed at a position corresponding to the hollow part of the hollow core and filled with sand, so that the petroleum solvent in the hardening agent contained in this sand is removed. The foamed resin reacts with the molded resin, and the foamed resin model contracts, forming a hollow part in the core.

Embodiment An embodiment of the hollow core molding method according to the present invention will be described with reference to FIGS. 1 to 3c. 1 and 2 are cross-sectional views for explaining the formation of the hollow part of the hollow core, and FIGS. 38 to 3C are diagrams showing the procedure for molding the hollow core by the cold box method.

The core that forms the hollow part in the casting is hollow to reduce weight and prevent gas release. When molding this hollow core 1 by the cold box method, first a model 3 having a shape corresponding to the hollow part 2 of the hollow core 1 is manufactured from a foamed resin such as foamed polystyrene or foamed polymethacrylic. The foamed resin is very light (for example, the specific gravity of foamed polystyrene is 0.02 to 0.04) and has good processability.

Next, the produced model 3 made of foamed resin is placed in a predetermined position of the core mold 5 using the mandrel 4 as a supporting member. After this,
The core mold 5 is filled with sand, and this sand filling may be done by using a blow molding machine 6 or by manual molding. The sand 7 used in the cold box method is a mixture of silica sand with appropriate amounts of phenol resin and polyisocyanate (M, D, 1.) added as hardeners (binding agents). . After sand filling is completed in this way, by blowing amine gas such as triethylamine into the hollow core L formed on the outer periphery of the model 3, the Angus reacts with the hardening agent of the sand 7, and the hollow core L is instantly hardens to. Furthermore, after the curing is completed, the reacted gas and unreacted gas are discharged by air and introduced into the exhaust purification tank 8 for purification.

By the way, foamed resins such as foamed polystyrene have the property of shrinking by reacting with the petroleum-based solvent in the curing agent contained in the sand used in the cold box method. Therefore, when the core mold 5 is filled with sand, the foamed resin model 3 comes into contact with the sand 7 and slowly shrinks due to the reaction with the petroleum solvent contained in the sand. As shown in FIG. 1, when the shrinkage of the model 3, which is surrounded by instantaneously hardened sand 7 on the outer periphery of the model 3, is completed, a hollow space is formed at the position where the model 3 was, as shown in FIG. 2 is formed. Thereafter, the mandrel 4 is removed and the molding of the hollow core 1 is completed.

At this time, the shrunken model 3' is left in the hollow portion, but this does not interfere with the weight reduction or degassing of the hollow core l.

Moreover, when it is desired to promote the contraction of the model 3, it is effective to heat the hollow core l integrated with the model 3 to about 80 to 120°C.

When the hollow core molding method described above is adopted, a model made of foamed resin is made to fit the hollow part of the desired shape, and after hardening the sand blown around the outer periphery of the model in the core mold, oil The model reacts with the solvent and shrinks to form a hollow part, so even if the hollow part has a complicated shape or a shape that makes it impossible to secure a hole for the mandrel, Core molding by the cold box method can be easily carried out without having to worry about the shape of the core or hollow part.

In addition, although the above-mentioned example showed and explained the case where the hollow core molding method according to the present invention was applied to the cold box method,
It goes without saying that the present invention is applicable not only to the cold box method but also to self-hardening molds using sand containing petroleum solvents.

Effects of the Invention According to the present invention described above, it becomes possible to form a hollow portion of a desired shape using a cold box method or a self-hardening mold, increasing the degree of freedom in selecting the shape of a moldable hollow core and its moldability. . Therefore, it becomes possible to mold a hollow core of a desired shape by adopting the most suitable molding method, taking into consideration the advantages and disadvantages of the shape, precision, cost, etc.

[Brief explanation of drawings]

The drawings show an embodiment of the hollow core molding method according to the present invention, and FIGS. 1 and 2 are diagrams for explaining the formation of the hollow part of the hollow core, and FIG. 1 shows the hollow part. Figure 2 is a cross-sectional view before forming the hollow part, Figures 3a to 3 are cross-sectional views after forming the hollow part.
Fig. c shows the procedure for forming a hollow core by the cold box method, and Figs. 4 and 5 show conventional examples. ! ...Hollow core, 2.Hollow part, 4. Core metal, 5.Hollow type, 6.. 7.Sand, 8.Exhaust septic tank, 9.

Claims (1)

[Claims] After a foamed resin model is placed in a predetermined position in the core mold, it is filled with sand, and the foamed resin shrinks due to the reaction between the petroleum solvent in the hardening agent contained in the sand and the foamed resin. A hollow core molding method characterized by forming a hollow part of the core.