JP2001096585A - Method for production of hollow object - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a hollow object for a short time. SOLUTION: In a method for producing a hollow object 12 by supplying a molding material to the gate 4 communicating with the outside of the cavity 6 formed by a movable mold 5b wherein an undercut 13 is provided to the side surface of a core pin 7 and a fixed mold 5a from a molding material supply part 1 through a runner 3, the core pin 7 is rotated before the hollow object 12 is separated from the core pin 7 to allow the residual matter connected to the outer periphery of the hollow object 12 to be spaced apart from the gate port 4a being the part connected to the cavity 6 of the gate 4.

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 hollow body having an annular cross section.

[0002]

2. Description of the Related Art In this type of hollow body manufacturing method,
A molding material is supplied to a gate communicating with the outside of the cavity through a molding material supply unit to a cavity having an annular cross section formed by a movable mold and a fixed mold having an undercut on a side surface of a core pin. This is to supply and produce a hollow body.

[0003]

However, in the above-mentioned prior art, as shown in FIG. 7, after the hollow body 12 is released from the core pin 7, the molded product after the release of the gate 4, the runner 3 and the like is formed. Since the objects are connected to the outer periphery of the hollow body 12, it is necessary to remove these residues by a cutting tool or the like manually or by using a machine, which causes a prolonged time of the manufacturing process as a subsequent process.

[0004] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for manufacturing a hollow body having a short manufacturing process time.

[0005]

According to a first aspect of the present invention, there is provided a method for manufacturing a hollow body, comprising a movable mold having an undercut on a side surface of a core pin and a fixed mold. In the method of manufacturing a hollow body that supplies a molding material to a gate communicating with the outside of the cavity from a molding material supply unit via a runner to a cavity having an annular cross section, the core pin is removed before releasing the hollow body from the core pin. By rotating, a residue connected to the outer periphery of the hollow body is separated from the hollow body from a gate port which is a portion connected to the cavity of the gate.

Accordingly, the residue is removed by the rotation of the core pin, and a post-process is not required. Therefore, the manufacturing time of the hollow body can be shortened, and the workability can be improved.

According to a second aspect of the invention, there is provided a method of manufacturing a hollow body, wherein the cross section of the gate opening is formed to be smaller than the cross sectional area of the runner.

Accordingly, since the gate opening has the weakest cross-sectional shape, the removal of the residue can be facilitated.

[0009]

1 to 7 show an embodiment of the present invention, and FIG. 1 is an explanatory diagram showing a configuration of the embodiment of the present invention. 2A and 2B are views showing a core pin which is a main part of the embodiment, wherein FIG. 2A is a perspective view and FIG. 2B is a view seen from above. 3 to 5 are explanatory diagrams showing the manufacturing steps of the embodiment. FIG. 6 is an explanatory diagram showing another configuration example of the embodiment. FIG. 7 is a perspective view showing the shape of another hollow body according to the embodiment.

The method of manufacturing a hollow body according to this embodiment is a method of forming a molding material in a cavity 6 having an annular cross section formed by a movable mold 5b having an undercut 13 on the side surface of a core pin 7 and a fixed mold 5a. From the supply unit 1 via the runner 3,
In the method of manufacturing the hollow body 12 for supplying the molding material to the gate 4 communicating with the outside of the cavity 6, the core pin 7
Before releasing the hollow body 12 from the mold, the core pin 7 is rotated so that the residue connected to the outer periphery of the hollow body 12 is separated from the hollow body 12 through the gate port 4a, which is a portion connected to the cavity 6 of the gate 4. I have. Further, the cross section of the gate port 4a of this embodiment is formed to be smaller than the cross sectional area of the runner 3.

FIG. 1 shows a mold apparatus, which includes a fixed mold 5.
a and the movable mold 5b. In the fixed mold 5a, a molding material supply unit 1, a sprue 2, a runner 3
And a gate 4 in communication with the cavity 6. In addition, the air bend 11 can exhaust air in the cavity 6 during injection molding. The movable mold 5b has a core pin 7 provided with an undercut 13 as shown in FIG. 2. The core pin 7 fits into the cavity 6 of the fixed mold 5a at the time of mold clamping, forming a hollow body. I do. Also, a stripper plate 8 for releasing the hollow body 12 from the core pin 7, an ejector pin 9a for pushing up the stripper plate 8, and an initial molding material in the molding material supply unit 1 and the sprue 2 during injection of the molding material. A cold slug 10 for improving the quality of the hollow body 12, and an ejector pin 9b for releasing a molded product in the cold slug 10 from the stripper plate 8.

Here, as a molding material, for example, a resin material such as polyacetal or SUS3 having an average particle size of 5 to 20 μm is used.
16. Injection molding is performed by using a powder injection molding material obtained by heating and kneading a metal powder such as SUS630, SKH57, and WC-Co and a binder made of wax or a thermoplastic resin such as polypropylene or polyacetal.

FIG. 3 shows the first step. First, the hollow body 12
In order to mold the mold, the movable mold 5b moves toward the fixed mold 5a, and the mold apparatus is clamped. Next, a molding material injection step is performed. The molding material injected from the molding material supply unit 1 is supplied from the gate 4 to the cavity 6 through the sprue 2 and the runner 3.

FIG. 4 shows the second step. After the first step, which is the injection step, there is a pressure-holding step and a cooling step for 3 to 10 seconds. Then, the movable mold 5b is separated from the fixed mold 5a and opened. At this time, the hollow body 12 of the hollow body is
Is moved to the movable mold 5b while holding the residue, that is, the sprue 2, the runner 3, and the gate 4, by the action of the undercut 13 provided in the movable die 5b.

FIG. 5 shows the third step. In this step, the ejector pins 9a and 9b are moved in the direction of the fixed mold 5a in the ejector step, and the residues of the sprue 2, the runner 3 and the gate 4 are integrated with the cold slug 10 and are ejected by the ejector pins 9a. Pushed up. The hollow body 12 is also pushed up by the stripper plate 8, but the hollow body 12 is rotated by the undercut 13 and separated from the residue at the gate opening.

In the case of the hollow body 12 made of metal powder, a degreasing step and a sintering step are added.

The degreasing step is performed by using a degreasing furnace at a normal pressure of nitrogen or hydrogen or under a reduced pressure atmosphere for 10 to 100 hours.
The temperature is raised to 300 to 600 ° C. at a rate of temperature / hour, and the binder contained in the hollow body is reduced to 70 to 95 wt%.
It is removed by thermal decomposition.

The sintering step is performed in a sintering furnace in a vacuum or under a pressure-controlled atmosphere using nitrogen or argon as a partial gas at a heating rate of 0.5 to 3 degrees / minute at 1200 to 1500 degrees. The temperature is raised to sintering.

Therefore, the residue is removed by the rotation of the core pin, and the post-process is not required. Therefore, the manufacturing time of the hollow body can be shortened, and the workability can be improved. Further, since the gate opening has the weakest cross-sectional shape, it is possible to easily remove the residue.

The present invention includes hollow bodies 12 of various shapes such as conical ones, for example, as shown in FIGS. 6 (a) to 6 (d), in addition to the cylindrical hollow bodies 12.

[0021]

As described above, in the method for manufacturing a hollow body according to the first aspect of the present invention, when the core pin is released, the hollow body is pulled out from the core pin while rotating along the undercut. In this case, almost no shear force is generated, and the breakage of the hollow body can be prevented.

According to a second aspect of the present invention, in addition to the effects of the first aspect, the gate having the weakest cross-sectional shape is cut from the hollow body by the rotation of the hollow body when the core pin is released from the mold. Therefore, it is possible to omit the post-treatment of cutting the residue from the hollow body, and to improve the working efficiency.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a configuration of an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a core pin which is a main part of the embodiment.

FIG. 3 is an explanatory diagram showing a manufacturing process of the embodiment.

FIG. 4 is an explanatory diagram showing a manufacturing process of the embodiment.

FIG. 5 is an explanatory diagram showing a manufacturing process of the embodiment.

FIG. 6 is a perspective view showing the shape of another hollow body according to the embodiment.

FIG. 7 is an explanatory diagram showing a schematic configuration of a conventional example of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Molding material supply part 2 Sprue 3 Runner 4 Gate 4a Gate opening 5a Fixed mold 5b Movable mold 6 Cavity 7 Core pin 8 Stripper plate 9a Ejector pin 9b Ejector pin 10 Cold slug 11 Air bend 12 Hollow body 13 Undercut

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] November 9, 1999 (1999.11.
9)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction contents]

[0009]

1 to 7 show an embodiment of the present invention, and FIG. 1 is an explanatory diagram showing a configuration of the embodiment of the present invention. FIG. 2 is a perspective view showing a core pin which is a main part of the embodiment. 3 to 5 are explanatory diagrams showing the manufacturing steps of the embodiment. FIG. 6 is an explanatory diagram showing another configuration example of the embodiment. FIG. 7 is a perspective view showing the shape of another hollow body according to the embodiment.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0015

[Correction method] Change

[Correction contents]

FIG. 5 shows the third step. In this step, the ejector pins 9a and 9b are moved in the direction of the fixed mold 5a in the ejector step, and the residues of the sprue 2, the runner 3 and the gate 4 are integrated with the cold slug 10 and are ejected by the ejector pins 9a. Pushed up. The hollow body 12 is also pushed up by the stripper plate 8, but the hollow body 12 is rotated by the rotation of the core pin 7 and separated from the residue at the gate port.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction contents]

[0021]

[Effect of the Invention] As described above, the manufacturing method according to claim 1 hollow body according to the present invention, upon release of the core pin, because middle empty body is pulled out from the core pin while rotating, remove residue <br />.

Claims (2)

[Claims] 1. A molding material supply unit communicates with the outside of the cavity through a runner from a molding material supply unit to a cavity having an annular cross section formed by a movable mold and a fixed mold having an undercut on a side surface of a core pin. In the method for manufacturing a hollow body for supplying a molding material to the gate, the core pin is rotated before the hollow body is released from the core pin, and a residual portion connected to the outer periphery of the hollow body from a gate port which is a portion connected to the cavity of the gate. A method for producing a hollow body, comprising separating an object from the hollow body. 2. The method for manufacturing a hollow body according to claim 1, wherein a cross section of said gate port is formed smaller than a cross sectional area of a runner.