JP2001047211A - Metallic mold and production of formed product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent defective formation, such as misrun, casting flash. SOLUTION: On the opposite surfaces one set of metallic molds 10, reversal shapes of the formed product are carved, respectively, (this carved surface is named as a cavity surface). Therefore, the cavity surface 12 for shaping the formed product is formed by mold-clamping with the advance of a movable plate 11A. On the ranges 10a, 10b for forming the thin thickness part of the formed parts on the cavity surface in one set of the metallic molds 10, the fine recessed parts having such degree that fluidized forming material is not inserted, are disposed in the suitable density, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold structure suitable for die casting, injection molding of a metal material or an alloy material.

[0002]

2. Description of the Related Art Die casting, injection molding using a metal material or an alloy material as a molding material, and the like as shown in FIG.
A set of molds 50 is used. One mold 50a (movable mold) of the set of molds 50 is attached to the movable platen 51a of the molding machine. The other mold 50b (fixed mold) is attached to a fixed platen 51b of the molding machine, and is filled with a molding material such as a metal material or an alloy material in a molten state. This molding material is filled into the cavity 53 formed by clamping the set of molds 50 via the sprue 52 and the gate 53. In addition, as the material of these molds 50, mold steel materials excellent in heat resistance, strength, wear resistance, and corrosion resistance are used.

[0003] Metals and alloys used as molding materials in this way have high thermal conductivity, so they are easy to cool.
Due to the heat radiation during the filling of the cavity 53, the viscosity increases or solidification starts. For this reason, insufficient filling of the molding material into the cavity 53 may occur, and the appearance of the molded product may be poor.

Therefore, in die casting and injection molding, the following measures are taken to prevent such insufficient filling of the molding material.

In die casting, a method is employed in which a molding material is cast into a mold at a high speed while maintaining the temperature sufficiently higher than the melting point.

On the other hand, in injection molding, a molding material is
A method of injecting into a cavity at a high pressure and a high speed as a semi-molten state with a small flow disturbance (a solid-liquid coexisting state called a thixotropic state) is adopted. In addition, as a technique related to this, for example, Japan Steel Works Technical Report No. 53
(1997.6) A thixomolding method for injection molding a magnesium alloy, described on pages 63 to 69, is known.

[0007]

However, when the molded article has a complicated shape (for example, a rib, a boss, a step portion, etc.), or when the thickness of the molded article is too thin, the above-mentioned conventional technique is required. In either case, insufficient filling of the molding material into the cavity may occur. In particular, poor filling of the molding material is likely to occur in a portion away from the gate.

In any of the measures, since the molding material is injected into the cavity at a high speed, the mold is opened by a high pressure load (about 500 to 600 kg / cm ² ) due to overfilling, and burrs are formed on the molded product. May be.

Further, when the molded product has a thick portion and a thin portion, the molded product is not uniformly cooled, so that the molded product is deformed (warped, etc.) or cracked due to internal stress. Sometimes.

Accordingly, an object of the present invention is to provide a mold having a structure that does not easily cause molding defects in a molded product, and a method of manufacturing the molded product.

[0011]

According to the present invention, there is provided a mold having a cavity surface forming a cavity portion filled with a molten or semi-molten molding material. The surface includes a plurality of concave shapes, and the concave portion of each concave shape has a size that does not allow the molding material to be filled to enter.

According to such a mold structure, the flow resistance between the cavity surface and the molding material is reduced by the lubricating effect of the air interposed between the cavity surface and the molding material. In addition, the heat insulating effect of the air interposed between the cavity surface and the molding material prevents the viscosity and solidification of the molding material during injection from being increased. Therefore, even if the injection speed of the molding material is not so high, the fluidity of the molding material is not lost, and the molding material can spread to every corner of the cavity. Therefore, the occurrence of molding defects such as insufficient filling of the molding material and burrs is prevented.

If the depth of each concave portion in the cavity surface of the mold is changed in accordance with the distance from the gate so that the heat insulating effect increases as the distance from the gate increases, the depth of the cavity can be increased. The longer the molding time, the more difficult it is to cool. As a result, the entire molded article is uniformly cooled, and the occurrence of cracks and deformation due to internal stress is prevented.

The present invention also relates to a method for manufacturing a molded product using a metal mold or an alloy, the method comprising: And a step of filling a molding material in a molten state or a semi-molten state.

According to the method of manufacturing a molded product according to the present invention, a molded product having a complicated shape (for example, a rib, a boss, a step portion, etc.), a thin molded product, etc. can be formed by the above-described effects. It can be manufactured without occurrence of molding defects.

[0016]

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

First, the structure of the mold according to the present embodiment will be described with reference to FIG.

In the mold 10 according to the present embodiment, the movable side (movable mold 10A) is attached to a movable plate 11A of an injection molding machine or a die casting machine, and is fixed (fixed mold 10B). Is mounted on a fixed platen 11B of an injection molding machine or a die casting machine.

Each of the molds 10 is formed of a mold steel material having excellent heat resistance, strength, abrasion resistance and corrosion resistance. The opposite surfaces are each engraved with the inverted shape of the molded product (hereinafter, these engraved surfaces are referred to as cavity surfaces). Therefore, the cavity portion 12 for forming a molded product is formed by clamping the mold by moving the movable platen 11A forward.

A sprue 13 for joining a nozzle for discharging a molding material such as a metal material or an alloy material in a molten state, and a runner for guiding the molding material from the sprue 13 to the cavity 12 are provided in the fixed mold 10B. 14 are provided.

On the other hand, the movable die 10A is provided with a protruding pin and a pin hole for protruding a molded product.

In the in-plane regions of the cavity surfaces of the pair of molds 10, the regions 10a and 10b forming the thin portions of the molded parts have such an extent that the flowing molding material cannot enter. Fine pores are dispersed at an appropriate density. Specifically, by etching, cutting, etc.
Many irregularities are formed in predetermined regions 10a and 10b of both molds 10A and 10B. However, the size of the concave portion into which the flowing molding material does not enter depends on the mold conditions such as the type of molding material, molding conditions of injection pressure of molding material, thickness of molded product (especially thin portion), distance from gate, etc. Parameter values (e.g., depth of recesses, etc.) that determine the size of the recesses formed in the cavity surface of each mold are values of experiments performed under actual molding conditions. Must be set based on the result. Also, using the analysis results of the flow analysis and the heat conduction analysis, it can be seen that the size of the concave portion is more effective as the size is larger within a range where the molding material does not enter, but if the concave portion becomes too large, this time, It can be seen that the step portion prevents the flow of the molding material, and the difference in cooling rate between the thin portion and the thick portion is excessively widened due to the heat insulating effect described below, so that an internal stress is generated in the molded product.
Therefore, it is desirable to set a parameter value that determines the size of the concave portion in consideration of such an analysis result.
Considering such analysis results, it can be seen that, for example, when the opening diameter of the concave portion is about 100 μm, it is appropriate to set the depth dimension to about 1.6 μm to 5.0 μm.

The molding material discharged from the nozzle joined to the sprue 13 does not enter into the concave portions of the cavity surface even when injected into the cavity portion 12. Therefore, a lot of fine air is interposed between the molding material and the cavity surface. Due to the lubricating effect of these bubbles, the flow resistance between the molding material and the cavity surface is reduced. Therefore, of the in-plane region of the cavity surface, the region 10 where the thin part of the molded part is formed is formed.
By dispersing such concave portions in a and 10b, the molding material can smoothly pass through a thin gap between the regions 10a and 10b. In addition, the heat insulation effect of the air interposed between the molding material and the cavity surface prevents the viscosity and solidification of the molding material during injection from being increased and prevents the fluidity of the molding material from being lost. Contributes. Therefore, even if the injection speed of the molding material is not so high, the fluidity of the molding material is hardly lost, and the molding material can spread to every corner of the cavity. As a result, insufficient filling of the molding material and occurrence of molding defects such as burrs are prevented. Further, prevention of stick-slip often seen on a mirror surface or the like is also achieved.

In order to confirm such an effect, actually,
Using this mold, a molded product including a thick portion having a length of about 200 mm × 300 mm, a thickness of about 1.5 mm, and a thin portion having a thickness of about 1.0 mm was injection-molded. The molding material is a magnesium alloy, and a plurality of concave portions having a depth of about 24 μm are formed by etching in a predetermined region (region forming a thin portion of the molded product) in the cavity surface of the mold.

As a result of observation of the completed molded product, almost no occurrence of molding defects (such as sink marks) due to insufficient filling of the molding material was observed in this molded product. No stick-slip was observed.

In this embodiment, the movable mold 10
Although the concave portions are dispersed in predetermined regions in the cavity surface on both sides of the mold A and the fixed side mold 10B, the concave portions may be dispersed only in predetermined regions in the cavity surface of one of the molds.

In this embodiment, the concave portion is formed directly in the mold 10, but it is not always necessary to do so. For example, another member having a concave portion may be fitted as a nest in a mold.

In the above description, in the cavity surface of the mold, the concave portions are dispersed at an appropriate density in a region where the thin portion of the molded product is molded, but the concave portions are dispersed in other regions. No problem. For example, the concave portions may be dispersed throughout the cavity surface. in this case,
Each recess has a distance between opposing cavity surfaces (i.e.,
It is desirable to have a size corresponding to at least one of the distance from the gate 14 and the distance from the gate 14. Hereinafter, a specific configuration example will be described.

FIG. 2 is a cross-sectional view of a mold having a cavity surface in which concave portions having a size corresponding to the distance between the opposing cavity surfaces (the thickness of the molded part) are dispersed.

On the cavity surface of this set of molds 10B, recesses satisfying the above conditions are dispersed at an appropriate density as a whole. Therefore, due to the above-described effects, the molding material smoothly passes through any region between the opposing cavity surfaces.

However, in this mold structure, regions 10a and 10b (thin portion forming regions) in the cavity surfaces of both molds 10A and 10B which form the thin portion of the molded product.
The recesses forming the voids larger than the recesses dispersed in the regions 10c and 10d (thick portion forming regions) forming the thick portions of the molded article, The concave portions deeper than the concave portions are dispersed. That is,
More air is held on the surfaces of the thin portion forming regions 10a and 10b.

For this reason, in the thin portion forming regions 10a and 10b where the thin portions that are easy to cool are formed, a higher heat insulating effect can be obtained than in the thick portion forming regions 10c and 10d that are difficult to cool. Therefore, the molded article is cooled uniformly as a whole, and the generation of internal stress in the molded article is avoided.

In order to confirm such an effect, actually,
Using this mold, a molded product made of a magnesium alloy including a thick portion having a length of about 200 mm × 300 mm, a thickness of about 1.0 mm, and a thin portion having a thickness of about 0.6 mm was injection-molded. The thin portion forming regions 10a and 10b of the mold used here include:
A plurality of recesses (depth / cavity distance = 0.04) having an opening diameter of about 200 μm and a depth of about 24 μm are formed, and the thick wall portions 10 c and 10 d have an opening diameter of about 200 μm and a depth of about 1 μm.
6 μm recess (depth / cavity surface distance = 0.016)
Are formed. Also in this case, the depth dimension of each concave portion is determined based on the results of the flow analysis and the heat conduction analysis as described above.

As a result of observing the completed molded product, it was found that molding defects such as insufficient filling of the molding material (such as sink marks), burrs, and deformation due to internal stress (such as cracking and warping) were observed. Did not. No stick-slip was observed. Thereby, the above-mentioned effect was confirmed.

Next, FIG. 3A is a cross-sectional view of a mold having a cavity surface in which concave portions having a size corresponding to the distance from the gate 14 are dispersed.

On the cavity surfaces of the set of dies, concave portions satisfying the above conditions are dispersed at an appropriate density as a whole. Therefore, by the above-mentioned effect,
The molding material passes smoothly through any area between the opposing cavity surfaces.

However, in the cavity surface of the mold structure, a concave portion which forms a larger gap as the regions 10e and 10f are farther from the gate 14, specifically, the gate 14
The concave portions deeper than the concave portions dispersed in the regions 10g and 10h close to the distance are dispersed. That is, as the distance from the gate 14 increases, more air is held on the cavity surface of the mold 10. Therefore, the hotter molding material injected later is easier to cool. For this reason, the molded article is uniformly cooled as a whole, and the generation of internal stress in the molded article is avoided.

In order to confirm such an effect, actually,
Using this mold, a magnesium alloy molded product having a length and width of about 200 mm × 300 mm and a wall thickness of about 0.8 mm was injection-molded. Central region 1 of cavity surface of mold used here
0g and 10h have an opening diameter of about 200μm and a depth of about 16μ
In the peripheral regions 10e and 10f, a plurality of recesses having an opening diameter of about 200 μm and a depth of about 24 μm are formed. Also in this case, the depth dimension of each recess is determined based on the results of the flow analysis and the heat conduction analysis as described above.

As a result of observing the completed molded product, it is found that molding defects such as insufficient filling of the molding material (such as sink marks), burrs, and deformation due to internal stress (such as cracks and warpage) are generated. Did not. No stick-slip was observed. Thereby, the above-mentioned effect was confirmed.

In this case, the size of the concave portion is discontinuously changed in the cavity plane. However, as shown in FIG. 3B, the concave portion gradually increases as the distance from the gate increases. Is also good.

Finally, an outline of a method for molding a molded product using the mold 10 according to the present embodiment will be described.

In the mold 10 according to the present embodiment, the movable mold 10A is attached to the movable plate 11A of an injection molding machine or a die casting machine, and the fixed mold 10B is attached to an injection molding machine or a die casting machine. To the fixed plate 11B. Then, the mold 10 is fastened by moving the movable platen 11A forward. As a result, a cavity 12 for forming a molded product is formed.

Then, a nozzle is joined to the sprue 13, and a molding material such as a magnesium alloy material in a semi-molten state is injected or cast from the nozzle into the cavity 12 at an appropriate pressure and speed. Thus, the cavity 12
When the molding material filled in the mold is hardened by cooling,
Retract 1A. Then, the molded product held on the movable mold is projected and projected with a pin. As a result, a molded article free of molding defects as described above is completed.

[0044]

According to the present invention, the fluidity of a molten or semi-molten metal or alloy material can be maintained without increasing the injection speed so much. The occurrence of molding failure is prevented. In addition, since the entire molded article is uniformly cooled, deformation (cracking, warping, etc.) due to internal stress is prevented.

[Brief description of the drawings]

FIG. 1 is a sectional view of a mold according to an embodiment of the present invention.

FIG. 2 is a sectional view of a mold according to one embodiment of the present invention.

FIG. 3 is a sectional view of a mold according to one embodiment of the present invention.

FIG. 4 is a sectional view of a conventional mold.

[Explanation of symbols]

 Reference Signs List 10: mold (10A: movable mold, 10B: fixed mold) 10a, 10b: thin portion forming region on cavity surface 10c, 10d: thick portion forming region on cavity surface 12: cavity portion 13: sprue 14 … Runner

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Keiji Takasu, Inventor 292, Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside the Hitachi, Ltd. Production Technology Laboratory (72) Inventor Hiroki Kuramoto 292, Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Inside Hitachi, Ltd. Production Technology Laboratory (72) Inventor Tsutomu Kono 292, Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside Hitachi-Production Technology Laboratory (72) Inventor Naotake Ebinuma Yoshida, Totsuka-ku, Yokohama, Kanagawa Prefecture No. 292, Hitachi, Ltd. Production Technology Research Laboratory, Hitachi, Ltd. (72) Inventor Masayuki Yamada 292, Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture F-term in Hitachi, Ltd. Production Technology Laboratory 4E093 NA01 NB00

Claims (5)

[Claims] 1. A mold having a cavity surface forming a cavity portion filled with a molding material in a molten state or a semi-molten state, wherein the cavity surface includes a plurality of concave shapes. The concave portion has a size such that the molding material being filled does not enter. 2. The mold according to claim 1, wherein each of the recesses in the cavity surface has a distance between the recess and a cavity surface facing the recess.
And a mold having a depth corresponding to at least one of a distance between a gate for discharging a molding material to the cavity and the recess. 3. A mold having a cavity surface forming a cavity portion filled with a molding material in a molten state or a semi-molten state, wherein the cavity surface is between the molding material being filled in the cavity portion. A mold having an air pocket in which air is interposed in the mold. 4. A molded article made of metal or alloy is manufactured.
A method for producing a molded product, comprising a step of filling a cavity portion of a mold according to any one of claims 1, 2 and 3 with a molding material in a molten state or a semi-molten state. Features,
Manufacturing method of molded article. 5. One of the first, second and third aspects of the present invention.
A molded article characterized by being molded by the mold described in the above item.