JPH0747443A - Lost wax casting method - Google Patents

Abstract

PURPOSE:To provide a lost wax casting method which dispenses with using a ceramic core or a water soluble core which is expensive and inferior in productivity, and can make a hollow casting at low cost and with high productivity. CONSTITUTION:A resin mold is formed so that an inside surface shape roughly coincides with a shape of a hollow part. The resin mold is set in a metallic mold having a shape of an external form of a product. By injecting wax between the metallic mold and the resin mold, a wax model formed integrally with the resin mold is formed. By convering this wax model with a refractory material, an unburned casting mold is made. From this unburned casting mold, wax is dewaxed. This unburned casting mold is burned. A molten metal is poured into the burned casting mold. Subsequently, by disjointing the mold, finish is executed. The resin mold can be made by an optical molding method, or a heat melted resin lamination molding method, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lost wax casting method for casting a hollow casting.

[0002]

2. Description of the Related Art When making a hollow casting by the lost wax method, a core (core) is set in a mold, and wax is injected between the core and the mold to make a wax model in which the core is wrapped.

Ceramics are used for iron-based castings.
A core is used, and the core is melted in an alkaline salt bath at the time of unmolding after pouring. For aluminum alloy castings, the casting itself is exposed to molten alkali, so a ceramic core is not used, but a water-soluble material is used to form the core.

[0004]

[Problems of the prior art] Conventional ceramic cores are made by solidifying and firing a refractory material according to the shape of the hollow portion. The refractory material used here is one having a large coefficient of thermal expansion such as silica sand. Instead, it is necessary to use a refractory material having a small coefficient of thermal expansion such as alumina, chamotte, zircon sand, mullite, or fused silica.

Conventional water-soluble cores usually have polyethylene glycol as a main base material and a suitable additive (filler).
And a material in which sodium hydrogen carbonate is mixed are used. However, the materials used for these ceramic cores and water-soluble cores are expensive.

Further, not only must each core be fired after molding, but when molding with a mold, it takes time and effort to remove burrs formed between the split surfaces of the mold, resulting in poor productivity. There was a problem.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is not necessary to use an expensive and poorly productive ceramic core or water-soluble core, and it is possible to produce a hollow casting at low cost with high productivity. It is an object of the present invention to provide a lost wax casting method capable of

[0008]

According to the present invention, this object is achieved by a lost wax casting method including the following steps. (a) Mold the resin mold so that the shape of the inner surface substantially matches the shape of the hollow portion; (b) Set the resin mold in a mold having the outer shape of the product; (c) the metal mold Wax is injected between the mold and the resin mold to form a wax model integral with the resin mold; (d) the wax model is coated with a refractory material to form an unfired mold; (e) From the unfired mold Dewaxing the wax; (f) Baking the unfired mold; (g) Pouring the molten metal into the baked mold; (h) Demolding and finishing.

In the resin mold, a photo-curing resin liquid is irradiated with light to be molded into a substantially hollow shape, or a heat-melting resin is jetted along the substantially hollow shape to cure the resin. It can be made by using a hot melt resin laminating method for laminating. It may also be made by a blow molding method.

When making a plurality of castings, a plurality of wax models may be brazed to the sprue bar to form a wax model tree. The present invention includes not only the ceramic shell molding method but also the solid molding method.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory diagram showing the first half of the process of the present invention, FIG. 2 is an explanatory diagram showing the latter half of the same, FIG.
Is a conceptual diagram of an optical molding method as a method for molding a resin mold, FIG. 5 is a conceptual diagram of a hot melt resin lamination molding method, and FIG. 6 is a conceptual diagram of a blow molding method.

In this method, as shown in FIG. 3, it is first necessary to mold the resin mold 10 (step 100). The resin mold 10 is molded so that the inner surface shape thereof substantially matches the shape of the hollow portion of the hollow casting. The resin mold 10 can be manufactured by, for example, an optical molding method, a hot-melt resin laminated molding method, a blow molding method, or the like.

The optical molding method uses a resin mold 10 as shown in FIG.
The three-dimensional model is input to a computer, and light (for example, laser) is applied to the photo-curable (for example, ultraviolet-curable) resin liquid along substantially the shape of the hollow portion to cure the resin liquid.

In FIG. 4, reference numeral 12 is a resin liquid tank, and 14 is an elevating table that moves up and down in the resin liquid tank 12. Reference numeral 16 is a laser emitting device, and 18 is a computer. The laser emitter 16 is movable in the horizontal direction above the resin liquid tank 12, and its position and laser emission are controlled by a computer 18. The resin liquid tank 12 is filled with ultraviolet curable resin liquid up to a predetermined height.

Data of the three-dimensional model of the resin mold 10 is input to the computer 18 in advance. Note that this data may be designed on the computer 18, or data read by another three-dimensional data reader or the like may be input.
The computer 18 moves the laser emitting device 16 along the shape of the resin mold 10 while lowering the elevating table 14 from the height of the liquid surface.

At this time, the resin mold 10 is hardened by irradiating a laser only on the position on the contour line where the resin mold 10 is thinly sliced. Then, the three-dimensional resin mold 10 is molded by repeating this operation while lowering the elevating table 14.

As shown in FIG. 5, the hot melt resin laminating method is a method of stacking a resin hot melted from an injector 20 on a base 22. At this time, the ejector 20 is position-controlled in the horizontal and vertical directions by the computer as in the case described with reference to FIG. Then, the resin is injected into a position on a contour line obtained by slicing the resin mold 10, and the resin is cured and laminated to form the resin mold 10. Reference numeral 24 is a reel around which a resin wire 26 is wound, and the resin wire 26 is supplied to the injector 20 from here.

In the blow molding method, as shown in FIG. 6, a resin bag (parison) 30 is sandwiched in a mold 34 of a mold 32, and compressed air is sent into the bag 30 to move the bag 30 to the inner surface of the mold 34. It is made to adhere and cure.

Needless to say, the resin mold 10 may be manufactured by a method other than the above method. For example, it can be made by a vacuum casting method. In this vacuum casting method, first, a highly accurate rubber mold is obtained from (master model) using a two-component silicone rubber for molding. Then, in this mold, a two-liquid type casting resin material (non-foaming polyurethane resin,
Thermosetting resin such as epoxy resin) is injected and cured to make a replica of the master model.

According to this vacuum casting method, the bubbles of the material can be removed, and the casting material can be penetrated to the details in the silicone mold. Further, by releasing the vacuum and introducing the outside air after the material injection, the material can be sufficiently pushed into every corner of the mold by utilizing the atmospheric pressure.

As a result, it is possible to easily obtain a beautiful molded product which does not contain air bubbles in the product and is free from short mold (state in which the material is not completely filled). In addition, even if there is some undercut using the elasticity of the rubber mold, it can be easily released, and there is almost no "sink" due to uneven thickness, and it is possible to mold thin products. Is.

The resin mold 1 thus produced by various methods
No. 0 is positioned in the mold 42 of the wax model 40 as shown in FIG. 1 (A) (step 102 in FIG. 3), and the wax is injected into the space between the mold 42 and the resin mold 10 (step 0). Step 104). By removing the mold 42, the wax model 40 in which the resin mold 10 is integrally adhered to the inner surface is obtained.

A large number of wax models 40 taken out of the mold 42 are shown in FIG.
It is fixed by a runner 46 made of wax. A wax model tree 48 is created by fixing a large number of wax models 40 to the sprue bar 44 (step 106).

The tree 48 is dipped in a slurry tank, sprinkled with stucco grains, and this operation is repeated an appropriate number of times to coat the refractory material to a predetermined thickness (step 108). At this time, the refractory material also enters the inside of the resin mold 10, and this portion 50 functions as a core as described later. In this way, the green mold 52 is produced.

The unfired mold 52 is turned upside down as shown in FIG. 2 (D) and rapidly heated by an autoclave or the like. As a result, only the wax portion of the wax model 40 flows out and is removed (step 110). In this state, the resin mold 10 remains in the mold 52.

The mold 52 is put into a firing furnace (not shown) and fired (step 112). Resin mold 1 at this time
0 disappears at the same time, and the portion 50 in the hollow portion is also fired at the same time to form the refractory material 50A serving as the core. The mold 52A fired in this manner has a sprue 5 as shown in FIG.
4 is held up, and molten metal is poured into this sprue 54 and cast (step 114).

Thereafter, the mold is released (step 116).
That is, the mold 52A is removed and the refractory 5 in the resin mold 10 is removed.
OA is also removed. At this time, the portion 50A corresponding to the core is
Since it is made of the same material as the outer portion of the mold 52, it can be easily removed. Then, a portion corresponding to the runner 46 is cut (step 118) and a finishing process is performed (step 12).
0), undergoes inspection and product is completed (step 12)
2).

Although the above embodiment has been described with reference to the ceramic shell molding method, the present invention is not limited to the solid shell molding method.
It may be a molding method. Also without tree 48 1
Of course, it can be applied to a method of continuously casting.

[0029]

As described above, according to the invention of claim 1, when a resin model having an inner surface shape substantially matching the shape of the hollow portion is set in the mold to form a wax model and a refractory is coated, Since the refractory is also filled in the inner core portion of the resin mold at the same time, the core portion is also fired at the time of firing the mold.

Therefore, the refractory of the mold can be used without using a special expensive refractory for the core, which is inexpensive.
Further, productivity is remarkably improved because deburring and firing of the core are not required as in the case where only the core is separately prepared.

The resin mold used here can be manufactured by various methods, for example, optical molding method (claim 2), hot-melt resin laminated molding method (claim 3), blow molding method (claim 3). ), Or vacuum casting method is suitable.

[Brief description of drawings]

FIG. 1 is an explanatory view of the first half of the method of the present invention.

[FIG. 2] Similarly, an explanatory diagram of the latter half

[Fig. 3] Process flow chart

FIG. 4 is a conceptual diagram of the optical molding method.

FIG. 5 is a conceptual diagram of a hot melt resin laminating method.

FIG. 6 is a conceptual diagram of the blow molding method.

[Explanation of symbols]

 10 Resin Mold 40 Wax Model 42 Mold 48 Tree 50, 50A Part Corresponding to Core 52 Unfired Mold 52A Fired Mold

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Claims (4)

[Claims] 1. A lost wax casting method for casting a hollow casting, comprising the following steps: (a) a resin so that an inner surface shape thereof substantially matches the shape of the hollow portion. Molding a mold; (b) setting the resin mold in a mold having the outer shape of the product; (c) injecting wax between the mold and the resin mold to integrate the resin mold. Molding a wax model; (d) coating the wax model with a refractory to make a green mold; (e) removing wax from the green mold; (f) baking the green mold; g) Pour the molten metal into the baked mold; (h) Remove the mold and finish. 2. The lost wax casting method according to claim 1, wherein the resin mold is formed by an optical molding method in which a photocurable resin liquid is irradiated with light substantially along the shape of the hollow portion. 3. The lost wax casting method according to claim 1, wherein the resin mold is made by a hot-melt resin lamination molding method in which the hot-melt resin is jetted along substantially the shape of the hollow portion while being hardened and laminated. 4. The lost wax casting method according to claim 1, wherein the resin mold is made by blow molding.