JPH0947842A - Casting method using resin core - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure the shape precision of a product formed by casting and to easily take out a core from the product. SOLUTION: The core 2n molded with a thermosetting resin is positioned in a mold, and molten metal is poured in the mold to form the product 1, and the core 2n is taken out from the product 1 after the temp. of the core 2n becomes a decomposition temp. or above. Therefore, the core 20 is not softened with the heat of the molten metal before the molten metal is solidified and the product 1 is formed, then the shape precision of the product 1 can sufficiently be ensured. Further, when the temp. of the core 2n becomes the decomposition temp. or above, the core 2n is thermal-decomposed and becomes brittle, so that the core can easily be taken out from the product 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a casting method using a resin core, and more particularly to a method for removing the resin core from a product.

[0002]

2. Description of the Related Art A technique relating to a casting method using a resin core is described in JP-A-6-328195.
According to the casting method, the core formed of the thermoplastic resin is positioned in the mold, the molten metal is injected into the mold to form the product, and the product is taken out from the mold, and further,
The softened resin is extracted from the product.

[0003]

However, since the core of the thermoplastic resin is used in the above-mentioned casting method, the surface of the core is in a so-called wet state in which it is in a semi-molten state before the molten metal is solidified. Therefore, there is a problem in that the product cannot be sufficiently shaped with high accuracy. The technical problem of the present invention is to enable the casting using a core of a thermosetting resin to prevent the core from being deformed and improve the shape accuracy of the product. It seeks to allow easy removal of offspring.

[0004]

[Means for Solving the Problems]

[Means according to Claim 1 for Solving the Problem] The above-mentioned problem is solved by a casting method having the following features. That is, in the casting method according to claim 1, after the core formed of the thermosetting resin is positioned in the mold and the molten metal is injected into the mold to form the product, the temperature of the core is the It is characterized in that the core is taken out from the product after the decomposition temperature of the curable resin is reached or higher. Therefore, the core is not softened by the heat of the molten metal until the molten metal is solidified and the product is molded, and the shape accuracy of the product can be sufficiently ensured. Further, when the temperature of the core is higher than the decomposition temperature, the core is decomposed by heating and becomes brittle, so that the core can be easily taken out from the product.

[Means according to Claim 2 for Solving the Problems] Further, the casting method according to Claim 2 is the casting method according to Claim 1, in which the core is taken out of the product when the core is taken out of the product. It is characterized by vibrating. Therefore, the core can be efficiently removed from the product.

[Means according to claim 3 for solving the problem] Further, in the casting method according to claim 3, in the casting method according to claim 2, the specific gravity of the thermally decomposed thermosetting resin. It is characterized in that the product is vibrated in the state that a substance having a higher specific gravity is present inside the core. Therefore, the substance acts so as to break the core during vibration, and the core can be taken out of the product more efficiently.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION A casting method using a resin core according to an embodiment of the present invention will be described below with reference to FIGS. 1 and 2. Here, FIG. 1 is a drawing showing the main steps of the casting method according to the present embodiment, and FIG. 2 is a graph showing the temperature change of the product and the temperature change of the core cast in the product. In this casting method, first, the core 2n having a predetermined shape is formed from a thermosetting resin. At this time, a plurality of small-diameter steel balls 3 are mixed in the thermosetting resin. Here, a silicone resin is used as the thermosetting resin in the present embodiment. The decomposition temperature of the silicone resin is about 300 ° C. as shown in FIG. 2, and the resin can maintain a predetermined strength until the average temperature of the core 2n exceeds about 300 ° C. In addition to the silicone resin, phenol resin, melamine resin, urea resin and the like are preferably used.

The core 2n thus formed is set at a predetermined position in a mold (not shown). Then, the mold is clamped after the core 2n is mounted on the mold, and the molten metal is injected into the mold. [Casting] shown on the horizontal axis of FIG. 2 represents this timing. Immediately after casting, the temperature of the molten metal did not decrease, and the core 2n
The average temperature is close to room temperature. Therefore, the thermosetting resin that constitutes the core 2n maintains a predetermined strength, and is not deformed even when exposed to the high temperature and high pressure of the molten metal.

The molten metal injected into the mold is gradually cooled and solidified mainly by the mold, and the mold is opened when the product is molded, and the product 1 is molded together with the core 2n into the mold. Taken from. On the other hand, the thermosetting resin forming the core 2n has a small thermal conductivity, and therefore the temperature rises slowly even when the heat of the molten metal is received. Further, the weight and shape of the core 2n are designed so as not to rise to the decomposition temperature until the molten metal is solidified and the product 1 is molded. Therefore, until the product 1 is molded, the thermosetting resin forming the core 2n retains a predetermined strength and is not deformed. Therefore, the defective shape of the product 1 due to the deformation of the core 2n does not occur.

[Removal] shown on the horizontal axis of FIG. 2 represents the timing at which the mold 1 is opened and the product 1 is removed from the mold. Further, FIG. 1A shows a vertical cross-sectional view of the product 1 taken out from the mold. The product 1 taken out of the mold in this way is conveyed to a heating furnace (not shown) and heated in the heating furnace. [Furnace] shown on the horizontal axis of FIG. 2 indicates the timing when the product 1 is inserted into the heating furnace.

In this way, when the product 1 is heated in the heating furnace and the average temperature of the cores 2n cast in the product 1 exceeds the decomposition temperature of the thermosetting resin, the product 1 is taken out of the heating furnace. Be done. [Exiting the furnace] shown on the horizontal axis of FIG. 2 represents this timing. Further, FIG. 1B shows a vertical sectional view of the product 1 taken out from the heating furnace. As shown in the figure, the thermosetting resin above the decomposition temperature is brittle,
It is in a state where it easily collapses.

The product 1 thus taken out from the heating furnace is set in a vibration machine (not shown) and vibrated. As a result, the steel balls 3 mixed with the thermosetting resin at the time of molding the core 2n act so as to crush the core 2n, and the crushed pieces of the core 2n can be efficiently taken out from the product 1. Like The [core removal] shown on the horizontal axis of FIG. 2 represents this timing.
(C) shows a state in which the steel balls 3 are crushing the core 2n due to vibration and discharging from the product 1.

As described above, in the present embodiment, the core 2n is not softened by the heat of the molten metal until the molten metal is solidified and the product 1 is molded, and the shape accuracy of the product 1 is sufficiently ensured. You can Further, unlike the case of the conventional thermoplastic resin, the surface of the core 2n is not in a wet state, so that the surrounding dirt can be prevented. Further, when the core 2n is taken out from the product 1 by vibration, the steel ball 3
Since the core 2n acts to break the core 2n, the core can be efficiently taken out from the product.

Although the embodiments of the present invention have been described above, the embodiments of the present invention have the following various technical items in addition to the technical items described in the claims. Please note that. (1) A core molded of a thermosetting resin is positioned in a mold, a molten metal is injected into the mold to mold a product, the product is taken out of the mold, and the product is heated to heat the inside. A casting method, characterized in that the core is taken out of the product after the temperature of the core reaches or exceeds the decomposition temperature of the thermosetting resin. By reheating the product, temperature control for making the temperature of the core higher than the decomposition temperature of the thermosetting resin is easy, and the temperature can be quickly raised to the decomposition temperature. (2) In the casting method according to claim 3, the core is molded in a state in which a substance having a specific gravity larger than that of the thermally decomposed thermosetting resin is included in the thermosetting resin in advance. Characteristic casting method. It is less labor intensive than inserting the substance into the core later. (3) In the casting method according to claim 3, after the thermosetting resin is pyrolyzed, a material having a specific gravity larger than the specific gravity of the thermosetting resin pyrolyzed immediately before vibrating the product is used as a core. A casting method characterized by inserting. Since the substance does not affect the molding of the product, the strength may be small as long as the specific gravity is large, and the selection range of the substance is widened.

[0015]

According to the present invention, since the core is not deformed before the molten metal is solidified, the shape accuracy of the product can be improved. Further, if the temperature of the core is equal to or higher than the decomposition temperature, it can be easily taken out from the product.

[Brief description of drawings]

FIG. 1 is a drawing showing main steps of a casting method according to a first embodiment of the present invention.

FIG. 2 is a graph showing a temperature change of a product according to the first embodiment of the present invention and a temperature change of a core that is cast in the product.

[Explanation of symbols]

 1 product 2n core 3 steel ball

Claims (3)

[Claims] 1. A core formed of a thermosetting resin is positioned in a mold, a molten metal is poured into the mold to form a product, and then the temperature of the core is the decomposition temperature of the thermosetting resin. A casting method, characterized in that the core is taken out from the product after the above. 2. The casting method according to claim 1, wherein the product is vibrated when the core is taken out from the product. 3. The casting method according to claim 2, wherein the product is vibrated in a state where a substance having a specific gravity larger than that of the pyrolyzed thermosetting resin is present inside the core. Characteristic casting method.