JP2002144007A - Die for die casting and its designing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cast plural pieces of die cast products having comparatively large size and complicated shape with high quality. SOLUTION: On the way of a main runner 16 continued to a biscuit forming part 7, the first sub-runners 11A, 11B are divided in the right and the left directions crossed to this extending direction and also, from the end part of this main runner 10, the second sub-runners 12A, 12B are divided into two branches to the extending direction, and with the respective sub-runners, cavities 14A, 14B, 15A, 15B are connected through respective gates 13. Then, the fluidity of molten metal is analyzed with a computer simulation and the length from the centers of the biscuit forming part 7 to the divided point S of the second sub-runners 12A, 12B is set so that the molten metal is made to flow into each cavity at almost same timing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a die-casting die capable of multi-cavity molding and a method for designing the die.

[0002]

2. Description of the Related Art For example, a base plate of a hard disk drive (HDD) is manufactured by die casting of an aluminum alloy. However, the base plate is relatively large and complicated in shape, and required quality (accuracy) is severe. Conventionally, one-cavity was standard and at most two-cavity was the limit.

[0003]

By the way, with the recent expansion of the computer (personal computer) market, the demand for price reduction of computer parts has become more and more severe, and the above-mentioned base plate for HDD (particularly, 2.5 inch HDD) has been greatly reduced. Cost reduction is required. However, as described above, since the number of pieces of the base plate is limited to two, it has been difficult to reduce the cost.

The present invention has been made in view of the above-mentioned conventional technical background, and an object of the present invention is to make it possible to take a plurality of die-cast products having a relatively large and complicated shape with high quality. Accordingly, it is an object of the present invention to provide a die casting mold and a design method thereof that greatly contribute to cost reduction.

[0005]

In order to achieve the above object, a die casting mold according to the present invention comprises a first sub-runner extending from a middle of a main runner following a biscuit forming portion in a lateral direction intersecting with an extension direction thereof. At the same time, the second sub-runner is bifurcated from the end of the main runner in the direction of its extension, and cavities are connected to the first and second sub-runners via gates, respectively. The length from the center of the biscuit forming portion to the branch portion of the second sub-runner is set so that the molten metal flows into the cavity at substantially the same timing. In the die casting mold configured as described above, the second sub-runner is bifurcated from the end of the main runner in the direction in which the second sub-runner extends, so that the flow of the molten metal to the second sub-runner becomes good, and Since the molten metal flows into each cavity at the same timing, four relatively large and complex-shaped die-cast products can be obtained with high quality.

In the die casting mold according to the present invention, the third sub-runner is bifurcated in a direction extending from the end of the second sub-runner, and the cavity for the second sub-runner is omitted. A cavity can be connected to the third sub-runner via a gate, and in this case, six cavities can be obtained. Further, in the present invention, each of the sub-runners may be formed so that the terminal cross-sectional area is smaller than the inlet cross-sectional area, whereby the flow rate of the molten metal increases toward the terminal of each sub-runner, Even if the cavity is provided at a position distant from the forming portion, the filling property of the molten metal into the cavity is sufficiently ensured.

The method for designing a die-casting die according to the present invention is characterized in that the flow of the molten metal is dynamically analyzed by computer simulation, and the biscuit forming part in the die-casting die is so set that the molten metal flows into each cavity at substantially the same timing. The length from the center to the second sub-runner or the third sub-runner is set. In the die-casting die designing method performed in this way, there is no need to actually manufacture the die and prototype the die-cast product, that is, so-called cut and try.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 and FIG. 2 show a die casting mold according to the present invention. In FIG. 2, reference numeral 1 denotes a fixed type in which a fixed insert 2 is mounted, and 3 denotes a movable type in which a movable insert 4 is mounted. The movable type 3 is supported by a movable base that moves forward and backward by driving means (not shown). At the time of casting, as shown in FIG. 2, the mold closed state fitted to the fixed mold 1 is maintained. The fixed mold 1 has a sprue bush 5,
A splitter 6 is provided in each of the movable molds 3, and a biscuit forming portion (gate section) 7 is formed between the sprue bush 5 and the splitter 6 in the above-described mold closed state. .

In the present embodiment, a main runner 10 following the biscuit forming portion 7 is provided at a joining portion of the fixed die 1 and the movable die 3 and a branch is made in the middle of the main runner 10 in a lateral direction crossing the main runner 10. Two first sub-runners 11
A and 11B, and two second sub-runners 12A and 12B bifurcated from the end of the main runner 10 are provided. This die-casting die is designed as a four-cavity die, and cavities 14A, 14B, 15A, and 15B are connected to the first sub-runners 11A and 11B and the second sub-runners 12A and 12B via a gate 13. Has been established. Of these cavities, two cavities (hereinafter, referred to as first-stage cavities) 14A and 14B connected to the first sub-runners 11A and 11B, respectively.
Are cavities (hereinafter referred to as second-stage cavities) 15A and 15B connected to the second sub-runners 12A and 12B.
Are newly provided in the present embodiment, and accordingly, the second sub-runners 12A and 12B corresponding to the second-stage cavities 15A and 15B are also new. In addition, each cavity 14A, 14B, 15A,
A pool 17 is connected to 15B via an overflow gate 16.

A predetermined amount of molten metal is injected into the sprue bush 5 from a plunger sleeve (not shown) containing a plunger in accordance with sliding of the plunger. The injected molten metal flows into the main runner 10 via the biscuit forming section 7 and fills the main runner 10, and then the first sub runner 11
A, 11B and the second sub-runners 12A, 12B, and further through the gate 13, the cavities 14A, 14B.
B, 15A and 15B. Also, some of the molten metal
After filling the cavities 14A, 14B, 15A, 15B, they flow into the pool 17 from the overflow gate 16, respectively.

In the die-casting mold, the second-stage cavities 15A and 15B must be provided at a position farther from the biscuit forming portion 7 than the first-stage cavities 14A and 14B due to the design of the mold. In the mold design (layout) of the first embodiment, the timing at which the molten metal flows into the second-stage cavities 15A and 15B is determined by the first-stage cavities 14A and 14B.
This is later than the timing at which the molten metal flows into B. However, in the present embodiment, the second-stage cavity 1
Since the second sub-runners 12A and 12B communicating with 5A and 15B are bifurcated from the end of the main runner 10,
The flow of the molten metal into the second sub-runners 12A and 12B becomes good, and the difference between the inflow timings of the molten metal is considerably eliminated.

Here, the flow of the molten metal is dynamically analyzed by computer simulation for the die casting mold having the above configuration, and the cavities 14A, 14B, 15A, 1
As a result of measuring the timing at which the molten metal flows into 5B, the second sub-runner 1 communicating with the second-stage cavities 15A, 15B
Bifurcation S (FIG. 1) and biscuit forming part 7 of 2A and 12B
, The second sub-runner 12A,
It has been found that the inflow timing is greatly affected by the position of the branch portion S of 12B. Specifically, as the branch portion S moves away from the biscuit forming portion 7, the timing of the flow of the molten metal into the second-stage cavities 15A and 15B becomes earlier, and the closer the branch portion S approaches the biscuit forming portion 7, the more the timing becomes.
The timing at which the molten metal flows into the stage cavities 15A and 15B is delayed. Therefore, in the present embodiment, the inflow timing of the molten metal into the second-stage cavities 15A and 15B becomes substantially the same as the inflow timing of the molten metal into the first-stage cavities 14A and 14B by the molten metal flow analysis by the computer simulation. Then, the position of the branch portion S was grasped, and this position S was set in a die casting mold. As a result, the molten metal flows into the first-stage cavities 14A and 14B and the second-stage cavities 15A and 15B at substantially the same timing. As a result, even if the HDD base plate is relatively large and has a complicated shape, , It is possible to take four high quality.

Further, in the present embodiment, each of the sub-runners 11A, 11B, 12A, 12B is formed such that each terminal cross-sectional area is smaller than the entrance cross-sectional area. Thereby, each sub runner 11A, 11B, 12
The flow velocity of the molten metal increases toward the ends of A and 12B, and as a result, the molten metal flows smoothly into the second-stage cavities 15A and 15B separated from the biscuit forming portion 7. In other words, even if the second-stage cavities 15A and 15B are largely separated from the biscuit forming portion 7, the filling property of the molten metal into the cavities can be sufficiently ensured, and the degree of freedom in designing the mold is improved accordingly. It will be.

In the above embodiment, the die-casting die is designed to be formed in four pieces. However, in the present invention, six pieces can be formed. In this case, the third sub-runner is further branched bifurcated from the end of each of the second sub-runners 12A and 12B, and each of the four third sub-runners thus formed is provided with a cavity (via a gate) via a gate. The second-stage cavity may be provided continuously. Again,
In the same manner as in the above-described embodiment, the biscuit forming section 7 is designed so that the molten metal flows into each cavity at substantially the same timing by the flow analysis by computer simulation.
From the center to the branch of the third sub-runner, that is, the position of the branch of the third sub-runner. Further, the third sub-runner is formed such that each terminal cross-sectional area is smaller than the inlet cross-sectional area, so that there is almost no difference in the inflow timing of the molten metal into the second-stage cavity and the first-stage cavity. Even with a relatively large and complicated base plate for HDD, high quality 6
You will be able to collect them.

Example A die-casting die having the layout shown in FIG. 1 was designed under the following conditions for a 2.5-inch aluminum alloy base plate (weight 125 g) for a 2.5-inch HDD. The flow is analyzed and each cavity 14A, 14B, 15A, 15B
The inflow timing of the molten metal into the furnace was measured. [Mold conditions] Distance between the center of the biscuit forming portion 7 and the branch portion S: 130 mm Cross-sectional area of the entrance of the sub-runners 11A, 11B, 12A, 12B: 96 mm ² Termination of the sub-runners 11A, 11B, 12A, 12B Area: 17.5 mm ² Inlet / terminal cross-sectional area ratio of sub-runners 11A, 11B, 12A, 12B: 5.5 [Casting conditions] Casting pressure: 9310 kPa Gate speed: 41-45 m / sec Melt temperature: 700 ° C Injection speed: High 2.25 to 2.50 m / sec Low 0.85 m / sec Filling time: 0.01 sec

As a result, each cavity 14 from the start of injection
The time required for the molten metal to reach the gate 13 with respect to A, 14B, 15A, and 15B is substantially constant at 0.03 sec.
The time until the molten metal is filled into B, 15A and 15B is
It is almost constant at 0.04 sec and the first cavity 1
It was confirmed that there was almost no difference in the inflow timing of the molten metal between 4A, 14B and the second-stage cavities 15A, 15B.

[0018]

As described above, according to the die casting mold according to the present invention, since the molten metal flows into each cavity at substantially the same timing, a die casting product having a relatively large and complicated shape like a base plate of a hard disk drive. Even in this case, four or six pieces can be obtained with high quality, which greatly contributes to cost reduction. According to the method for designing a die casting mold according to the present invention,
The flow of the molten metal is analyzed using computer simulation, and the design is made so that the molten metal flows into each cavity at almost the same timing. Practical use of the die casting mold can be achieved at low cost.

[Brief description of the drawings]

FIG. 1 is a plan view showing a layout of a die casting mold as an embodiment of the present invention.

FIG. 2 is a sectional view showing the overall structure of the die casting mold.

[Explanation of symbols]

 7 Biscuit forming section 10 Main runner 11A, 11B First sub-runner 12A, 12B Second sub-runner 13 Gate 14A, 14B First-stage cavity 15A, 15B Second-stage cavity

Claims (5)

[Claims] 1. A first sub-runner is branched from the middle of a main runner following a biscuit forming portion in a left-right direction intersecting with an extension direction of the first runner. The two sub-runners are branched, cavities are connected to the first and second sub-runners via gates, and the molten metal flows into each cavity at substantially the same timing. A die-casting die wherein a length up to a branch portion of the second sub-runner is set. 2. The third sub-runner is bifurcated in the direction of extension of the second sub-runner from the end of the second sub-runner, a cavity for the second sub-runner is omitted, and a gate is provided to each of the third sub-runners. 2. The die casting mold according to claim 1, wherein the cavities are connected to each other. 3. The die-casting die according to claim 1, wherein each of the sub-runners is formed to have a terminal cross-sectional area smaller than an inlet cross-sectional area. 4. The die casting die according to claim 1, wherein the die casting die is for casting a base plate of a hard disk drive. 5. The method for designing a die casting mold according to claim 1, wherein the flow of the molten metal is dynamically analyzed by computer simulation, and the molten metal flows into each cavity at substantially the same timing. like,
A method for designing a die casting mold, comprising setting a length from a center of a biscuit forming portion to a branch portion of a second sub-runner or a third sub-runner.