JPH11156484A - Manufacture of metallic mold for forming and gypsum mold used for it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a metallic mold for forming having fidelty to a master model for product in high precision at a low cost even in the case of being the complicate rugged pattern, in a gypsum mold casting method. SOLUTION: This manufacturing method is composed of a process for forming the product model where a product master rigid model M1 having the same shape as the product shape is formed with machining, a process Y2 for forming a metallic mold model where a metallic mold master rubber model M2 having the same shape as the metallic mold for forming is formed by molding the product master rigid model M1 using a liquefied rubber, and a process for forming the gypsum mold where the gypsum mold reversed with the metallic mold master rubber model M2 is formed by molding the metallic mold master rubber model M2 using the gypsum.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a molding die capable of producing a molding die for producing a molded article having a complicated uneven pattern on its surface with high precision and at low cost, and a method for producing the same. It relates to a plaster mold to be used.

[0002]

2. Description of the Related Art Many molding dies for producing molded articles such as rubber and plastic are generally formed by die casting in which molten metal is injected under pressure into a metal mold. Created by law.

However, as shown in FIG. 9, when a mold splitting die for forming a molded product W such as a rubber ball having a complicated uneven pattern c on the surface is directly formed by a die casting method. As shown in exaggeration in FIG. 10, a convex portion c1 near the split surface b of the uneven pattern c transferred to the molding die a is formed inside the metal mold d. Therefore, it is difficult to remove the molding die a from the metal mold d, or the concave and convex pattern c such as the convex portion c1 may be damaged.

As described above, in the die casting method, it is difficult to form a molding die a having a complicated concavo-convex pattern c in the vicinity of the cut surface b with a pattern shape faithful to the molded product W. Therefore, in the prior art, the irregular pattern c
Is formed with or without a shallow surface, and the concave and convex pattern c is additionally corrected by hand processing or the like on a molding die a after casting.

However, in this case, not only does the pattern accuracy decrease at the correction points, but also the correction points are aligned on both sides of the split surface, so that the pattern accuracy of the molded product W is more remarkably reduced, and the molded article W has a good appearance. In addition, the quality of products and the like are significantly impaired.

[0006] As one of the precision casting methods, a show process method, a ceramic casting method, a gypsum mold casting method, and the like are also known. However, the above-mentioned show process method and the ceramic casting method have disadvantages such as being expensive. is there. In addition, the gypsum mold casting method is inexpensive, but is inferior in transfer accuracy when forming a gypsum mold from a product master model, and furthermore has a problem of strength,
Due to problems such as surface defects caused by gas when pouring molten metal, it has not been used for casting a molding die having a complicated uneven pattern.

Therefore, the present invention provides a method of forming a plaster mold from a product master model, once forming a mold master rubber model having the same shape as a molding die using liquid rubber, and then using the mold master rubber model. In addition, in the gypsum mold, based on providing a surface layer made of high-strength gypsum on the surface of a main body made of foamed gypsum reinforced with short glass fibers, even when having a complicated uneven pattern, it is faithful to the product master model. It is an object of the present invention to provide a method for producing a molding die capable of producing a highly accurate and inexpensive molding die and a gypsum mold used for the method.

[0008]

In order to achieve the above object, a first invention of the present application is a method for producing a molding die, which has a copying surface having the same shape as a product shape by cutting. A product model forming step of forming a product master rigidity model; and a mold model forming step of forming a mold master rubber model having the same shape as a molding die by molding the product master rigidity model using liquid rubber. When,
Gypsum-molding the mold master rubber model, thereby forming a gypsum mold for forming a gypsum mold for molding die casting by inverting the mold master rubber model. .

A second invention of the present application is a gypsum mold used in the first invention, comprising a surface layer having a surface forming a mold forming surface, and a main body holding the surface layer. Is made of high-strength gypsum having a thickness of 2 to 3 mm after drying, and the main body portion is made of foamed gypsum containing short glass fibers and having an increase rate of 170 to 250%.

A plurality of vacuum holes extending from the bottom surface of the gypsum mold toward the molding surface of the gypsum mold are provided in the main body of the gypsum mold, and the vacuum holes are provided with a pressure resistance of not more than a maximum internal pressure of 32 Hg. It is preferable to terminate at a position at a distance of 3 to 5 mm from the molding surface. The gypsum mold is dried in two steps of a preliminary drying step and a main drying step, and the residual moisture content after the main drying step is 0 to 3%.
It is preferable that

[0011]

Embodiments of the present invention will be described below with reference to the drawings. The first invention of the present application is a method for producing a molding die for producing a molded product such as rubber or plastic. In this example, as shown in FIG. 9, complicated surfaces such as dimples and seams are formed on the surface. A case will be described in which a molding die 1 for molding a molded product W, which is a soft baseball having an uneven pattern c, is formed.

As shown in FIG. 1, the molding die 1 includes upper and lower split dies 2 and 2 forming a closed molding chamber by abutting a split surface 2S. Formed from material. Each split mold 2 has, for example, a half-shaped cavity 5 that is surrounded by a molding surface 4 having a concavo-convex pattern c at one end of a cylindrical mold main portion 3.

The method for preparing the split mold 2, which is the molding die 1, includes a product model forming step Y1, a mold model forming step Y2, and a gypsum mold forming step Y3.

In the product model forming step Y1, as shown in FIG. 2, a male product master rigidity model M1 having a copying surface S1 having the same shape as the molded product W is formed.

More specifically, by cutting a cuttable material such as metal, wood, synthetic resin, and gypsum, in this example, a block material 6 of gypsum by various NC processing machines 7 such as an engraving machine, A product master rigidity model M1 is formed on a base 8 with an elaborate copying body 9 having the same shape as the half of the molded product W protruding therefrom. At this time, the copying body portion 9 is formed at a dimensional ratio in consideration of the heat shrinkage of the mold material (aluminum in this example).

The product master rigidity model M1 is
This is used to create the cavity 5 that is the inner part of the split mold 2. In this example, the outer mold part m <b> 1 is used to create the outer part of the split mold 2.

As shown in FIG. 3, the mold outside model m1 has a concave portion 10 having the same shape as the outside portion of the split mold 2.
A is a female mold recessed in a rigid block 10 such as gypsum, and is formed by the following mold outer model forming step Z1.

The mold outer model forming step Z1 is the same as that shown in FIG.
As shown in (1), first, an outer rigid model m0 having the same shape as the outer portion of the split mold 2 is formed by NC-cutting a machinable material such as gypsum, and the outer rigid model m0 is once formed. Step P2 of copying to the rubber model n0 of the same shape, and after casting and curing the plaster 12 in a wooden frame 11 surrounding the rubber model n0, the rubber model n0 is removed and the mold outer model m1 is removed.
And step P3 of forming In addition, the bottom wall of the mold outside model m1 is provided with the gypsum mold in step P3 (or in the processing after the mold) in FIG.
As shown in FIG. 1, an injection port 13 for injecting liquid rubber is provided.

In the step P2, as shown in FIG. 4, a female mold 15 is prepared by pouring a liquid rubber such as silicon rubber into a wooden frame 14 surrounding the outer rigid model m0. Recess 15A of rubber female mold 15
Then, another liquid rubber, for example, a polysulfide rubber is poured thereinto to form a rubber model n0. At this time, the female mold 15 may be formed of polysulfide rubber, and the rubber model may be formed of silicone rubber. As another method, after forming the female mold 15 of polysulfide rubber, a silicone release agent is applied to the inner surface of the recess 15A,
Thereafter, a rubber model n0 can be formed by pouring a polysulfide rubber into the recess 15A. However, in the latter case, it is preferable to mold using a different type of liquid rubber as in the former case, since the mold accuracy varies due to the uniformity of the release agent application.

In the mold outside model forming step Z1, the mold outside model m1 can be directly cut and formed by NC cutting according to the required outside shape of the mold.

Next, as shown in FIG. 5, the mold model molding step Y2 is a step of forming the mold master rubber model M2 by molding the product master rigid model M1 using liquid rubber. It is.

In this embodiment, the mold model forming step Y2
After the product master rigidity model M1 and the mold outside model m1 are abutted, the copying body 9 and the recess 10
A mold master rubber model M2 having the same shape as that of the split mold 2 is formed by injecting and curing liquid rubber from the inlet 13 into the space 16 between the mold A and the space A. At the time of injection, the injection port 13 is turned upside down so that the injection port 13 faces upward. Here, as the liquid rubber, various materials such as urethane rubber can be used as long as they solidify after pouring, such as the silicone rubber and polysulfide rubber, but polysulfide rubber is used from the viewpoint of shape transferability. Is more preferred.

The gypsum mold forming step Y3 is a step of forming the gypsum mold 21 by molding the mold master rubber model M2 using gypsum, as shown in FIG.

In the present embodiment, the gypsum mold forming step Y3 includes:
After the mold master rubber model M2 is placed in the wooden frame 22, a high-strength gypsum 24 having a substantially constant thickness T is formed on the inner surface of the concave portion 23 of the mold master rubber model M2 corresponding to the cavity 5. After spray coating and coagulation, the foamed gypsum 25 containing short glass fiber is added at an increasing rate of 170 to 250.
%, And further poured to form a male gypsum mold 21. Therefore, the gypsum mold 21 according to the second invention of the present application comprises a surface layer 26 made of high strength gypsum 24 and forming a mold forming surface 26S,
6 and a main body 27 made of foamed gypsum 25.

After the gypsum mold 21 is removed from the wooden frame 22, the gypsum mold 21 is preliminarily dried in a known hot air circulating exhaust type electric drying furnace until it becomes a hemihydrate gypsum state. Then, as shown in FIG. 8, a plurality of vacuum holes 29 extending from the bottom surface 27S of the main body portion 27 toward the mold forming surface 26S are dispersed at regular intervals in the main body portion 27 of the gypsum mold 21 by post-processing. After the formation, the main drying heat is performed again using a hot air circulation exhaust type electric drying furnace until the residual moisture content becomes 0 to 3%. The residual moisture content means the weight ratio of the residual moisture to the gypsum weight of the gypsum mold 21.

At this time, the thickness T of the surface layer 26 after the main drying heat is in the range of 2.0 to 3.0 mm, and the tip of the vacuum hole 29 is located at a distance from the mold forming surface 26S. Terminate at a distance L in the range of 3-5 mm. Note that the distance L means the shortest distance from the mold forming surface 26S having the irregularities. The vacuum hole 29 preferably has a strength (pressure resistance) that can withstand a substantially vacuum internal pressure of 32 Hg or less. For this reason, in this example, the content of the glass short fibers is set to 5 to 10 parts by weight, and the diameter of the vacuum hole 29 is 3 to 5 mm.
It is formed in a small hole. The short glass fiber has a fiber diameter of 10 to 10 in terms of reinforcing effect, moldability, and workability.
Those having a size of 15 μm are preferred.

As the gypsum mold 31 for forming the outside of the mold, the outside mold m1 can be used. As shown in FIG. 7, the gypsum mold 31 is placed in a wooden mold 32 surrounding the mold master rubber model M2. 12 may be formed by casting.

The split mold 2 is provided with the plaster mold 2
It is created by a casting process Y4 using the components 1 and 31.

In the casting step Y4, as shown in FIG. 8, the plaster molds 21 and 31 are placed on the casting platen 33 in abutting manner, and the plaster mold 21 is sucked by the vacuum 34 from the bottom surface 27S of the plaster mold 21. , From the injection port 35 to the internal space 36
Then, the molten metal is poured. At this time, it is preferable that the time required for removing the gypsum mold 21 from the hot-air circulating exhaust-type electric drying furnace and pouring it is within 10 minutes in order to maintain a high surface property of the molding die. .

In the present embodiment, a layer 37 made of a gas-permeable material such as glass wool is formed with a substantially constant thickness between the casting platen 33 and the gypsum mold 21 in this embodiment. The sealing is performed by sealing the side surface other than the connecting portion with the sealing agent 39.

As described above, since gypsum is used as the material of the product master rigidity model M1 in this embodiment, cutting is easy, and mistakes during the cutting are repeated by applying the gypsum liquid again. Handling is convenient, for example, processing can be performed.

Further, from the product master rigidity model M1,
Since the plaster mold 21 is formed via the mold master rubber model M2 using liquid rubber, even when a complicated and deep uneven pattern c is arranged in an undercut shape in the vicinity of the split surface 2S, the mold is removed at the time of demolding. In addition, the mold master rubber model M2 is elastically deformed, and the precise uneven pattern c faithful to the product master model M1 can be accurately transferred to the gypsum mold 21.

The gypsum mold 21 may be crushed after casting the split mold 2 and damage the split mold 2 by removing gypsum powder which adheres to the molding surface 4 of the cavity 5 with, for example, high-pressure water. And can be easily taken out.

Further, since the mold master rubber model M2 is interposed, the plaster mold 21 having the completely same shape can be repeatedly duplicated from this one mold master rubber model M2, and a plurality of molding dies are used. It can be suitably used for mass production of the molded article W.

On the other hand, the gypsum mold generally contains moisture in the gypsum even after being dried, so that the molten metal is heated by pouring the molten metal into steam gas, and a part of the gas flows out from the surface of the gypsum mold. As a result, the surface properties of the transferred mold are significantly inhibited.

On the other hand, the gypsum mold 2 of the second invention
In No. 1, since the surface layer 26 other than the mold forming surface 26S is formed of the foamed gypsum 25 with a weight increase rate of 170% or more, the entire water content is suppressed low, and the foamed pores allow the steam gas to escape. To function as a place, the mold forming surface 26S
Outflow of steam gas from the fuel cell can be further suppressed. In particular, the combined use of the suction through the vacuum hole 29 can more effectively and surely suppress the outflow of the steam gas, and can form the molding surface 4 of the molding die 1 more precisely and with higher precision. .

In order to reduce the generation of steam gas itself,
As described above, it is preferable to dry the residual moisture content to the range of 0 to 3%. Usually, when over-dried to 3% or less, the gypsum strength is significantly reduced and it becomes brittle and easily collapsed.
In this example, since the reinforcing member is reinforced by short glass fibers, the required strength can be maintained even in the over-dried state, and the pressure resistance in the vacuum hole 29 can be sufficiently exhibited.

The thickness T of the surface layer 26 is 2.0 mm
If the distance L is less than 3.0 mm, and if the distance L is less than 3.0 mm, the pressure resistance at the tip of the vacuum hole 29 becomes insufficient. vice versa,
When the thickness T is larger than 3.0 mm and the distance L is larger than 5.0 mm, the effect of suppressing the outflow of steam gas by the intake air decreases. On the other hand, if the amount of foamed gypsum exceeds 250%, it is difficult to maintain strength, and if the content of short glass fibers exceeds 10 parts by weight, moldability and workability are impaired.

It should be noted that the high-strength gypsum referred to in the present application is a gypsum obtained by adding a refractory agent to a gypsum for casting, as is well known, for example, Gypsum Y-15 made by San-Es.

The foamed gypsum is formed by putting a foaming agent in a gypsum and foaming the gypsum itself in a sponge shape, as is well known, for example, Gypsum GIA made by Noritake.

The method for preparing a molding die and the gypsum mold of the present invention can be applied to the preparation of a molding die for a molded product W having various shapes and patterns without being limited to balls.

[0042]

Since the present invention is configured as described above,
Even when having a complicated uneven pattern, a molding die faithful to the product master model can be produced with high precision and at low cost.

[Brief description of the drawings]

FIG. 1 is a perspective view showing one embodiment of a molding die produced by the present invention.

FIG. 2 is an explanatory diagram showing a product model forming process together with a product master rigidity model.

FIG. 3 is an explanatory diagram showing a mold outer model forming step together with a mold outer model.

FIG. 4 is an explanatory diagram showing a step of copying an outer rigid model to a rubber model of the same shape.

FIG. 5 is an explanatory diagram showing a mold model molding step together with a mold master rubber model.

FIG. 6 is an explanatory view showing a gypsum mold forming step.

FIG. 7 is an explanatory view showing a step of forming a gypsum mold for forming the outside of the mold.

FIG. 8 is an explanatory view showing a casting step.

FIG. 9 is a front view showing an example of a molded product.

FIG. 10 is a cross-sectional view illustrating a conventional technique in casting a molding die.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Molding mold 12 Gypsum 21 Gypsum mold 24 High-strength gypsum 25 Foam gypsum 26 Surface layer 26S Mold forming surface 27 Main body 27S Main body bottom 29 Vacuum hole M1 Product master rigidity model M2 Mold master rubber model S1 Copying surface T Surface layer thickness Y1 Product model forming process Y2 Mold model forming process Y3 Plaster mold forming process

Claims (4)

[Claims] 1. A product model forming step of forming a product master rigid model having a copying surface of the same shape as a product shape by cutting, and forming by molding the product master rigid model using liquid rubber. A mold model molding step of forming a mold master rubber model having the same shape as the mold, and a mold master rubber model inverted by molding the mold master rubber model using gypsum. A method for forming a gypsum mold for forming a gypsum mold for mold casting. 2. A gypsum mold used in the method for producing a molding die according to claim 1, wherein the surface layer forms a die molding surface;
A main body that holds the surface layer, the surface layer is made of high-strength gypsum having a thickness after drying of 2 to 3 mm, and the main body contains short glass fibers and has a weight gain of 170 to A gypsum mold comprising 250% foamed gypsum. 3. The main body has a plurality of vacuum holes extending from a bottom surface of the main body toward the molding surface.
The gypsum mold according to claim 2, wherein the vacuum hole has a pressure resistance of an internal pressure of 32Hg or less and terminates at a position separated by a distance of 3 to 5mm from the molding surface. 4. The gypsum mold is dried in a hot air circulating exhaust air drying oven in two steps, a predrying step and a main drying step, and the residual moisture content after the main drying step is zero. The gypsum mold according to claim 2, wherein the amount is 3% to 3%.