JPH0440096B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing a simple mold used for press working, resin molding, etc.

(Conventional technology) There have been various methods for manufacturing simple molds. For example, there is a general-purpose casting method ("metal press "November 1976, p. 16, 17), or the dual-form method ("Machines and Tools"), in which a sheet metal model is immersed in a molten low-melting-point alloy in a melting tank and solidified to obtain a punch and die at the same time ("Machines and Tools").
June 1975, pp. 21-25) have already been put into practical use. However, the former method is less productive because it transfers the model using plaster and sand molds rather than wooden molds, while the latter method is more productive because it solidifies directly onto the sheet metal model, but the precision required when manufacturing the sheet metal model is extremely high. The problem was that it could not easily accommodate difficult and complex design changes, and it lacked general versatility.

Therefore, as shown in Japanese Patent Publication No. 26-6455, for example, there is a method (method A) of using a wooden model as a matrix and directly casting a low melting point alloy into this wooden model to obtain a mold, or a special method. As shown in Publication No. 63-273544, silicone rubber,
A method (Method B) in which a mold is obtained by casting a low melting point alloy through a heat-resistant rubber sheet made of fluorocarbon rubber or the like is useful. According to these methods, it is possible to easily manufacture a mold using a wooden model, so that the above-mentioned problems can be solved.

(Problem to be Solved by the Invention) However, according to the method of casting a low melting point alloy into the wooden mold model, a large amount of gas (mainly water vapor) is generated from the wooden mold model due to the heat of the molten metal. In method A, cavities occur due to the entrainment of gas, while in method B, gas collects between the rubber sheet and the wooden model, causing unevenness on the surface, both of which impair casting quality. The problem was that the decline became inevitable.

In addition, so-called wooden molds for casting include, for example, as shown in Japanese Utility Model Publication No. 47-27610, a hardened layer of impregnated plastic is formed on the surface layer to prevent dimensional deviation over time; Alternatively, as shown in Japanese Patent Publication No. 52-27088, there is a method in which a silicone resin-impregnated layer is formed on the surface layer to improve mold release durability, and these techniques can be used in the wooden mold model mentioned above. It is possible that However, if these techniques are used as is, the wooden model still contains a lot of water, so there is a risk that the impregnated layer will be destroyed during casting and gas will blow out, so it is not a fundamental countermeasure. .

The present invention has been made to solve the above-mentioned conventional problems, and its purpose is to suppress gas generation from wooden models as much as possible, and to produce molds with excellent casting quality. An object of the present invention is to provide a simple mold manufacturing method that can stably obtain a mold.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a method in which a wooden model or its raw wood is left in a vacuum or kept in a heating furnace to drain moisture from inside. After that, a heat-resistant paint is applied to the wooden model or a wooden model processed from the raw wood to impregnate the surface layer of each of the wooden models, and after drying the paint, It is characterized by a structure in which a low melting point alloy is cast using the model as a master mold.

In the present invention, the heat-resistant paint is not particularly limited in type as long as it has heat resistance, and for example, silicone resin paints, epoxy resin paints, fluororesin paints, ceramic coating agents, etc. are selected. be able to. Further, the method of applying these paints to the wooden model is also arbitrary, and various methods such as brushing, spraying, and dipping can be employed. Further, the heat-resistant paint may be applied to the entire surface of the wooden model, but it is necessary to apply the heat-resistant paint to at least the surface of the product shape.

In addition, in the present invention, when draining moisture from a wooden model or its raw wood by holding it in a heating furnace, the temperature must be higher than the pouring temperature of the low melting point alloy and lower than the temperature at which the wood carbonizes. Although the temperature is not particularly limited, it is desirable to select a temperature slightly higher than the pouring temperature of the low melting point alloy. Further, in this case, the inside of the heating furnace may be set in a vacuum atmosphere to promote drainage of moisture.

Further, in the present invention, the types of the above-mentioned low melting point alloys are not limited, but Bi, Pb, Cd, Sn, Sb, In
Alloys consisting of two or more such as Bi-Sn, Bi
-Alloys such as Pb, Sn-In, Bi-Sb-Sn, etc. can be used.

(Function) In the simple manufacturing method configured as described above, the wooden model or its raw wood is left in a vacuum or kept in a heating furnace to remove moisture, thereby producing a low melting point alloy. During casting, a large amount of gas is not generated, and the impregnated layer of heat-resistant paint suppresses the gasification of residual moisture in the wooden model, making the casting stable.

(Embodiments) Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows a first embodiment of the present invention. In the first embodiment, a wooden model 1 having a product shape surface 2 is manufactured by processing raw wood in advance. First, this wooden mold model 1 is left in a vacuum for a predetermined period of time to sufficiently drain moisture from inside the wooden mold model, and then the wooden mold model 1 is coated with silicone resin paint, and the product shape is Allow the silicone resin to fully penetrate into the surface layer on the second side. Next, the surface of the wooden model 1 is irradiated using a lamp with high irradiation energy, such as a far-infrared lamp, and the silicone resin paint is sufficiently baked and dried to coat the surface of the product shape side 2 of the wooden model 1. A hard silicone resin impregnated layer 3 is formed on the portion. After that, the wooden model 1 prepared as above
are set in upper and lower casting frames 4 and 5 as shown in Fig. 1, and a low melting point alloy 7 is poured into the casting space 6 on the wooden model 1, and then cooled and solidified to form a metal. Cast the mold.

Therefore, during the above-mentioned casting, since the moisture is drained from the wooden model 1 by leaving it in a vacuum in advance, a large amount of gas is not generated during casting, and in addition, the silicone resin impregnated layer 3 Therefore, the gasification of the moisture remaining in the wooden mold model 1 is suppressed, and as a result, the occurrence of cavities due to gas entrainment in the mold is almost eliminated.

FIG. 2 shows a second embodiment of the invention. In this second embodiment, the raw wood for the wooden model was charged into a heating furnace in advance and heated to a temperature of about 250°C.
The raw wood is held for a period of time to sufficiently drain moisture from the inside of the raw wood, and then the wooden model 11 is removed from the raw wood.
Process. Then, the processed wooden model 1
A silicone resin paint is applied to the product shape surface 12 of one product by spraying, and the silicone resin is sufficiently penetrated into the surface layer on the product shape surface 12 side. After that, dry the silicone resin thoroughly, and then
After applying silicone resin paint 2 to 3 times on Step 2, the surface of the wooden model 11 is heated (250°C) and dried to form a hard silicone resin impregnated layer 13 on the surface layer on the product shape surface 12 side. do. Note that an air passage 14 is provided in this wooden model 11.

Next, wooden model 1 prepared as above
1 is placed in a die casting frame 16 together with a heat-resistant rubber sheet (silicon rubber) 15, as also shown in FIG.
Further, the back of the wooden model 11 is surrounded by a punch casting frame 17, and negative pressure is supplied into the punch casting frame 17 by operation of a vacuum pump 18. By supplying this negative pressure, the air between the product shape surface 12 of the wooden model 11 and the rubber sheet 15 is transferred to the air passage 1.
4 and is discharged to the outside, and the rubber sheet 15 is brought into close contact with the wooden model 11. A low melting point alloy molten metal 20 is held in advance in the die casting frame 16, and a pipe 21 is introduced into a reservoir 19 communicating with the die casting frame 16.
When compressed air is supplied through the die casting frame 16
The low melting point alloy molten metal 20 inside is pushed up and comes into contact with the wooden model 11, and if it is cooled and solidified as it is,
A die is cast. When casting this die, moisture is removed from the raw wood by heat treatment in advance, so gas generation from the wooden model 11 during casting is suppressed, as in Example 1 above, and the wooden model 11 Gas will no longer collect between the die and the rubber sheet 15, and the quality of the resulting die will be significantly improved.

In the second embodiment, in particular, the wooden model 11 is processed after removing moisture at the stage of raw wood, which suppresses shrinkage of the wooden model 11 during casting and improves the dimensional accuracy of the die. I come to do it. Incidentally, as a result of measuring the shrinkage rate of the wooden model, the shrinkage rate of the main wooden model 11 in the grain direction is approximately
The shrinkage rate of the conventional wooden model, which does not undergo any moisture drainage process, is approximately 1.1%, compared to 0.2%.
It was confirmed that the dimensional stability of this wooden model 11 was extremely high.

Note that after the die casting described above, the wooden model 11 is removed from the mold, and the punch casting frame 17 is used as the die as a new mother mold.
A punch can be cast by pouring a low melting point alloy into the mold and letting it cool and solidify, and the mold clearance between the die and punch thus obtained is guaranteed by the rubber sheet 15. Ru.

(Effects of the Invention) As described above in detail, according to the simple mold manufacturing method according to the present invention, water is drained from the wooden model or its raw wood in advance, and the surface layer of the wooden model is Since it is impregnated with heat-resistant paint, it is possible to suppress gas generation from the wooden model and perform stable casting, which has the effect of making it possible to obtain molds with excellent casting quality.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention;
FIG. 2 is a sectional view showing a second embodiment of the present invention. 1, 11... Wooden model, 2, 12... Product shape surface, 3, 13... Impregnated layer, 5, 6, 16, 17... Casting frame, 15... Rubber sheet.

Claims (1)

[Claims] 1. After leaving the wooden model or its raw wood in a vacuum or holding it in a heating furnace and draining moisture from inside, the wooden model or the wooden model processed from the raw wood has heat resistance. A simple mold characterized in that a paint is applied, the paint is impregnated into the surface layer of each of the wooden models, and after the paint is dried, a low melting point alloy is cast using each of the wooden models as a mother mold. Production method.