JPH01184107A - Preparation of resin mold - Google Patents

Abstract

PURPOSE:To prevent leakage of a liq. resin and to attempt to decrease after- treatment of a molded item, by forming a rubber part at least at an apex part of a surface of a projected pin, expanding the rubber part at a curing temp. of a resin and thereby bringing the expanded rubber part into close contact with a circumferential guide hole of the projected pin. CONSTITUTION:A master model 1 is placed on an aluminum plate 2 and the surface of this master model 1 is coated with a water-soluble releasing agent by using a brush. After drying as it is, a low m.p. zinc metal is flame-sprayed. After cooling, a frame is placed around the aluminum plate and a resin compsn. wherein an aluminum fine powder and a liq. acrylic resin are mixed is cast on the flame-sprayed substance. A cavity-mold 3 and a core-mold 4 are thus prepd. When casting, a resin feeding hole 5 is inserted in the cavity-mold 3 and adhered therewith and a silicone rubber part 6a having the same diameter as that of an apex of a projected pin 6 is formed on the apex of the projected pin 6 and it is placed at a specified place of the master model so that it can be set on the core-mold 4. Metal blocks are placed around the cavity-mold 3 and the core-mold 4. A mold usable for injection molding of a reactive resin is thereby obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for manufacturing a resin mold that prevents leakage of resin from ejector pins during molding of reactive resin and improves service life. .

Conventional technology Conventionally, molding using this type of reactive resin is often done using molds using silicone rubber, and silicone rubber is often used because it has fluidity and can be easily manufactured into molds. It was getting worse.

On the other hand, the lifespan of molds is short, and if a large amount of back-production is required, many molds are required, which reduces the effectiveness in terms of cost, schedule, etc.

On the other hand, as improvements to this type of mold, resin molds, metal molds (aluminum cutting, low melting point metal spraying molds such as zinc/bismuth), etc. are sometimes used.

These molds have features such as high precision and long mold life, but on the other hand, they have many problems.

Problems to be Solved by the Invention Although resin molds and metal molds have the characteristics of high precision and long life as described above, they also have problems.

That is, in such a mold, a method is used to take out the product by using an ejector pin built into the mold to eject the product when the mold is opened. However, in order to perform this demolding smoothly, it is necessary to provide a clearance between the mold and the ejector pin.

However, when using a liquid resin composition, the resin invades the clearance and makes it impossible to remove the mold from the mold.
However, there are problems such as damage to the parts.

The present invention solves the above-mentioned problems, and aims to provide a method for manufacturing a resin mold in which the clearance portion of the ejector pin is sealed to prevent resin leakage.

Means for Solving the Problems In order to solve the above problems, the resin mold manufacturing method of the present invention forms a rubber part on the surface of an ejector pin, places this ejector pin on a part of the master model, and then After that, metal is thermally sprayed, and a liquid resin composition containing fine gold powder with a specific gravity of at least twice that of the resin is cast at least three times that of the resin, thereby producing a resin mold used as a mold for, for example, a reactive resin. It is.

Effect With the above structure, the obtained resin mold has a protruding pin with a rubber part formed on the surface, and the rubber part of the ejecting pin expands due to the curing reaction temperature of the material poured into the mold, and the clearance part of the ejecting pin is expanded. It is sealed to prevent resin from leaking.

EXAMPLE Hereinafter, an example of the present invention will be explained with reference to the drawings.

FIG. 1 is a perspective view of a master model used in a resin mold manufacturing method according to an embodiment of the present invention, and FIG. 2 is a schematic sectional view of a resin mold obtained by the same resin mold manufacturing method.

Master model 1 shown in Figure 1 has a length of 300 mm.

It was installed approximately in the center of an aluminum plate 2 with a width of 200 m and a thickness of 10 sheets, and a water-soluble mold release agent was brushed on the surface of this master model, and after air drying, a zinc-based low melting point metal was sprayed.
After cooling, a frame is installed around the aluminum plate, and #-4
A resin composition prepared by mixing 00 fine aluminum powder 4.5~ with liquid acrylic resin (Atlas M130, manufactured by Texa Corporation) 11Qi+ was cast onto the above thermal sprayed material. In this way, the cavity mold 3 and the core mold 4 shown in FIG.
was produced.

3a and 4a are thermally sprayed gold leaf layers, and 3b and 4b are resin compositions. During the above casting, a resin injection port 5 is inserted and glued into a part of the cavity mold 3, and a silicone rubber portion 6a with the same diameter is formed at the tip of the ejecting pin 6.
master model 1 so that it can be installed in the core mold 4.
It was placed at a predetermined location and cast. Said cavity mold 3
A metal block 7 was provided around the core mold 4 to obtain a mold that can be used for injection molding of reactive resin. Table 1 shows the results of molding urethane resin using the mold thus obtained.

As a comparative example, the ejector pin 6 used in the above embodiment
Instead, a similar fur mold was obtained using an ejector pin without silicone rubber attached to the tip.

The results of molding the mold thus obtained using urethane resin in the same manner as in the above example are shown in Table 1.As is clear from the results shown in Table 1, the core mold of the mold obtained in this example Since the silicone rubber part 6a is formed at the tip of the protruding pin 6, the silicone rubber part 6a adheres tightly to the guide hole due to thermal expansion, resulting in good airtightness, no leakage of resin, and a reduced number of molding shots before failure occurs. 1200, which has a much longer lifespan than the comparative example 85, which has an ejector pin without silicone rubber attached to the tip, and the occurrence of defects in this series was limited to a part of the sprayed metal layer peeling off. On the other hand, in the comparative example, the resin leaked from the clearance part of the ejector pin, making demolding difficult, and the mold around the ejector pin was damaged.

In addition, in the present invention, the amount of rubber provided on the surface of the ejector pin is adjusted in accordance with the curing temperature of the reaction resin to be molded, thereby preventing the rubber portion from entering the molded product and producing a high-quality molded product. can be obtained.

Effects of the Invention As described above, in the resin mold manufacturing method of the present invention, by forming a rubber portion at least at the tip of the surface of the ejector pin, the rubber portion expands at the curing temperature of the resin and the ejector pin is heated. It is possible to maintain airtightness by closely contacting the peripheral guide hole and prevent leakage of liquid resin, reducing post-processing of molded products and further improving quality.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a master model used in a resin mold manufacturing method according to an embodiment of the present invention, and FIG. 2 is a sectional view of a mold obtained by the same resin mold manufacturing method. 1... Master model, 3... Cavity type, 4
... Core type, 3 a + 4 a ... thermal sprayed metal layer,
3b, 4b...Resin composition, 5...Resin injection port, 6...Ejection pin, 6a...Rubber part.

Claims (1)

[Claims] 1. When manufacturing a resin mold equipped with a resin injection port and an ejector pin, the ejector pin is placed on a master model with a rubber part formed on at least the tip of its surface, and a metal thin film is placed on the surface of this master model. A layer is formed, and a resin composition containing fine metal powder having a specific gravity of at least twice that of the resin and at least three times the weight of the resin is cast onto the thin metal layer to form a mold. Method of manufacturing resin molds.