JP2005262494A - Male mold - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem wherein a corner right-angled to a lamination direction is formed in the plastic member left in the runner because the direction of the runner is inclined with respect to the lamination direction in a case that a mold for molding an inclined tapered runner constituting a submarine gate is molded by a metal laminating and shaping method and it is difficult to take the plastic member out of the runner because the corner is protruded from the inclined tapered inner surface of the runner to be hooked with the runner. <P>SOLUTION: In the male mold 2 brought into contact with a female mold 3 along a parting surface 4 and forming a predetermined cavity 5 filled with a molten material 6 along with the female mold 3 and having the injection boss hole 2A communicating with the cavity 5 to guide the molten material 6, a runner 2C, wherein the tapered leading end inclined with respect to the parting surface 4 communicates with the injection boss hole 2A to guide the molten material 6, is provided and a runner part 2F produced by lamination on a plane almost vertical to the runner 2C is provided. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a male mold for use in plastic injection molding.

  There is a submarine gate as a method for leaving no gate mark on the front surface of the plastic product to be injection molded. The gate is an inlet for the molten material into the cavity of the mold. The submarine gate is a part of the structure of the core mold that is a male mold on the back side of the product. The submarine gate consists of a rod-shaped injection boss hole on the back of the product, a gate on the side of the injection boss hole, and a slanted tapered truncated cone runner that is part of the path through which molten material flows into the gate. Constitute.

There is a metal additive manufacturing method in which a mold is manufactured by additive manufacturing from metal powder. In the metal additive manufacturing method, for example, a mold is formed as follows. A metal powder with a binder (polymer) added is thinly applied to the molded part, and a laser beam with a diameter of about 0.3 mm is scanned according to the three-dimensional CAD data in a nitrogen gas atmosphere. Are formed one by one in a thickness of 0.05 to 0.1 mm. The metal powder that has not been solidified after forming the whole is removed, and the formed mold is sintered in a hydrogen reduction furnace at 250 to 350 ° C. to vaporize the bonding material. Thereafter, copper melted in a furnace at 1120 to 1150 ° C. is allowed to penetrate into the mold by capillary action. (For example, see Patent Document 1)
In order to perform the metal additive manufacturing method in a short time, there is a method in which only a part having a predetermined thickness is manufactured by additive manufacturing from the surface of the mold, and the other part is constituted by a reinforcing material layer. (For example, see Patent Document 1)

Japanese Patent Laid-Open No. 10-323862.

As a method of processing a mold for forming an inclined tapered runner constituting the submarine gate, there are cutting processing, electric discharge processing, metal additive manufacturing method, and the like. Since the gate diameter is as small as about 0.5 to 1.2 mm and the runner is tapered and slanted, it is necessary to use a large, high-precision processing machine for cutting and electric discharge machining, and machining is not easy. There was a problem. Moreover, since the shape of the submarine gate is different for each product, a cutting tool or a discharge tool is required for each product.
In the case of forming by the metal additive manufacturing method, since the direction of the runner is inclined, the plastic member remaining on the runner has an angle perpendicular to the stacking direction. Since this corner protrudes and catches from the tapered inner surface of the runner, there is a problem that it is difficult to take out the plastic member from the runner.

  The male die according to the present invention is in contact with the female die at the parting surface, forms a predetermined cavity filled with the molten material between the female die, and guides the molten material connected to the cavity. In a male mold having a boss hole, a tapered tip inclined with respect to the parting surface has a runner that leads to the injection boss hole and guides the molten material, and is manufactured by laminating on a plane substantially perpendicular to the runner It is characterized by having a runner portion.

  The male die according to the present invention is in contact with the female die at the parting surface, forms a predetermined cavity filled with the molten material between the female die, and guides the molten material connected to the cavity. In a male mold having a boss hole, a tapered tip inclined with respect to the parting surface has a runner that leads to the injection boss hole and guides the molten material, and is manufactured by laminating on a plane substantially perpendicular to the runner Since the provided runner portion is provided, there is an effect that the plastic member can be easily pulled out from the runner portion.

Embodiment 1 FIG.
FIG. 1 is a perspective view for explaining the shape of a plastic product 1 used for explaining an embodiment of the present invention. FIG. 1A is a front perspective view, and FIG. 1B is a rear perspective view. Moreover, the top view which looked at the plastic product 1 from the back surface is shown in FIG. The plastic product 1 is a lid that closes a rectangular opening of a metal product. In such a plastic product 1, in order not to leave a trace of the gate for injecting the molten material on the surface side, injection molding is performed using a submarine gate. By using a submarine gate, an injection boss mark 1A is formed on the back surface of the plastic product. There is also a protruding pin mark 1B on the back surface of the plastic product. The injection boss mark 1A and the protruding pin mark 1B will be described later.

FIG. 3 is a plan view of a mold for injection molding using a submarine gate, FIG. 4 is a cross-sectional view before forming the plastic product 1 in the AA section of FIG. 3, and the plastic product 1 is formed. FIG. 5 shows a cross-sectional view after the completion. In FIG. 3, the structure inside the mold is indicated by a broken line. 3 to 5, the plastic product 1 is formed in the hollow portion 5 between the core mold 2 that is the lower male mold and the cavity mold 3 that is the upper female mold. The upper surface of the core mold 2 and the lower surface of the cavity mold 3 are in contact with each other at the parting surface 4. In FIG. 4, an arrow is written in the path for injecting the molten material 6 (not shown).
The core mold 2 has a circular injection boss hole 2A for guiding the molten material 6 to the hollow portion 5 from the core mold 2 side, and a diameter leading to the molten material 6 connected to a portion near the bottom of the injection boss hole 2A. There are a gate 2B having a thickness of about 0.5 to 1.2 mm and a runner 2C having an inclined tapered cross section connected to the gate 2B from the right side in the drawing. The mold 3 includes a sprue 3A having a circular cross section with a thicker lower side in the drawing connected to the runner 2C. The molten material 6 is injected from the injection molding machine 7 (not shown) into the sprue 3A, guided through the runner 2C, the gate 2B, and the injection boss hole 2A and injected into the cavity portion 5.

  As shown in FIG. 5 which is a cross-sectional view after the plastic product 1 is formed, the plastic product 1 is formed in the hollow portion 5, the injection boss 8 is formed in the injection boss hole 2A, and the remaining plastic is formed in the runner 2C and the sprue 3A. 9 is formed. After the plastic product 1 and the injection boss 8 are removed from the core mold 2, they are separated at the injection boss separation portion 1C. The injection boss mark 1 </ b> A is a mark obtained by separating the injection boss 8 from the plastic product 1.

  The core mold 2 also has an ejection pin 2D for ejecting the plastic product 1 together with the injection boss 8 after the plastic product 1 is formed, and an ejection pin 2E for ejecting the remaining plastic 9. The protruding pin 2D is accommodated in the hole so as to be movable up and down, and the upper surface of the protruding pin 2D is the same height as the upper surface of the core mold 2. The molten material 6 slightly enters the boundary between the protruding pin 2D and its accommodation hole, and a protruding pin mark 1B is formed on the back surface of the plastic product 1.

  The runner portion 2F, which is a part of the rectangular parallelepiped core mold 2 with the gate 2B opened to the left end face and slightly above the position below the gate 2B, is formed by three-dimensional CAD using a metal additive manufacturing method. Based on data. The parts other than the runner part 2F are integrally manufactured by casting or the like, and the runner part 2F and other parts are integrated by screwing. At the time of screwing, an attachment fitting for fastening may be used, or the runner part 2F may be screwed directly to the other part.

FIG. 6 shows a cross-sectional view from the side surface of the runner portion 2F immediately after forming by the metal additive manufacturing method. An enlarged view of the vicinity of the gate 2B of the runner portion 2F is shown in FIG. The enlarged portion in FIG. 7 is a portion surrounded by a broken line in FIG.
As shown in FIG. 7, since the central axis 2H is perpendicular to the laminated surface, the runner 2C that is narrower near the gate 2B is formed as a hole whose upper side is enlarged stepwise in the metal additive manufacturing method. For this reason, when the hole of the lower layer is moved upward, it is completely included in the hole of the runner 2C of the upper layer.
On the outer surface of the runner portion 2F, the end of the laminated surface is stepped to form a minute groove. The outer surface of the runner portion 2F is processed so that there is no minute groove on the outer surface of the runner portion 2F at an appropriate time until integration with other than the runner portion 2F.

  Since the direction of the plane which laminates the protruding pin accommodation hole 2G by the metal additive manufacturing method is inclined, the protruding pin 2E cannot be moved smoothly as it is. In order to allow the protruding pin 2E to move smoothly, the hole is enlarged by a drill or reamer after the processing by the metal additive manufacturing method, and the center position, diameter, surface roughness, etc. are finished to the required accuracy. The projecting pin accommodating hole 2G is perpendicular to the bottom surface of the runner portion 2F and has a constant hole diameter, so that it is easy to process by drilling.

  This is the end of the description of the structure, and the operation will be described below. The runner portion 2F of the core mold 2 is formed by a metal additive manufacturing method, and is integrated with another portion manufactured by another method to manufacture the core mold 2. The cavity mold 3 is also manufactured by an appropriate method. When other devices and raw materials necessary for manufacturing the plastic product 1 are thus prepared, the plastic product 1 is manufactured by the following process.

(Manufacturing process of plastic product 1)
(Step 1) The mold cavity 3 is superposed on the core mold 2. FIG. 4 shows this state.
(Step 2) An injection molding machine 7 (not shown) injects a molten material 6 (not shown) into the sprue 3A and fills the cavity portion 5 without leaving a space. The molten material 6 is also filled into the sprue 3A, the runner 2C, and the injection boss hole 2A. FIG. 5 shows this state.
(Step 3) Wait for a predetermined time determined in consideration of the time for the molten material 6 to solidify.
(Step 4) The mold cavity 3 is removed. FIG. 8 shows a cross-sectional view from the side of the core mold 2 and the plastic product 1 with the mold 3 removed.
(Step 5A) The protruding pin 2D is moved in the direction of the parting surface 4 to remove the plastic product 1 and the injection boss 8 from the core mold 2.
(Step 5B) At the same time as or before and after (Step 5A), the protruding pin 2E is moved to remove the residual plastic 9 from the core mold 2. When the protrusion pin 2D or the protrusion pin 2E is moved forward, the injection boss 8 and the residual plastic 9 are separated at the position of the gate 2B. FIG. 9 shows a cross-sectional view from the side of the core mold 2 and the plastic product 1 in a state where the process 5A and the process 5B are being performed.
(Step 6) The injection boss 8 is separated from the plastic product 1 at the injection boss separation portion 1C.

Since the layer perpendicular to the runner 2C is formed in the runner portion 2F of the core mold 2 by the metal additive manufacturing method, the residual plastic 9 can be smoothly removed from the runner 2C in step 5B.
As a comparative example for explaining the effect in more detail, a layer parallel to a plane (in this case, a plane parallel to the parting surface 4) of the runner portion 2F of the core mold 2 that is not perpendicular to the runner 2C is formed by a metal additive manufacturing method. FIG. 10 shows an enlarged view of substantially the same part as FIG. In FIG. 10, the runner 2C has a stepped space, and the remaining plastic 9 is filled in the stepped space of the runner 2C without any gap. A surplus portion 9A (not shown) of the residual plastic 9 is formed in the surplus space 2J which is a stepped corner portion.

When the residual plastic 9 is moved in parallel to the central axis 2H of the runner 2C, the surplus portion 9A is caught on the corners of the stacked layers on the inner surface of the runner 2C. Therefore, it becomes difficult to remove the residual plastic 9 from the runner 2C. On the other hand, when the runner portion 2F of the core mold 2 is formed by a metal additive manufacturing method with a layer perpendicular to the runner 2C, the surplus plastic portion 9A is not generated in the residual plastic 9, and the residual plastic 9 is smoothly removed from the runner 2C. Can be removed.
Since only the runner part 2F is formed by the metal additive manufacturing method, the mold can be manufactured at a lower cost than the case where the whole is formed by the metal additive manufacturing method.

  In the first embodiment, the case of the plastic product 1 having a lid that closes the rectangular opening has been described. However, the plastic product 1 may have any shape. Although the screwing method is used to integrate the runner part 2F and the other part of the core mold, if the runner part 2F and the other part of the core mold can be integrated with a predetermined accuracy and strength, Any method is acceptable. Although only the runner portion 2F is formed by the metal additive manufacturing method, the entire core mold 2 may be formed by the metal additive manufacturing method.

In the first embodiment, the runner portion is formed by the metal additive manufacturing method on a plane perpendicular to the central axis 2H of the runner 2C. However, if the surplus plastic portion 9A is not generated in the residual plastic 9 when it is removed from the runner 2C. It may not be perpendicular to the central axis 2H. If the angle of the tip of the runner 2C is 2 × θ, the surplus portion 9A is not generated in the residual plastic 9 if the angle between the central axis 2H and the laminated surface is in the range of 90−θ degrees to 90 + θ degrees. . Assume that the laminated surface is perpendicular to the runner 2C when the angle between the central axis 2H and the laminated surface is in the range of 90-θ degrees to 90 + θ degrees. Further, it is assumed that the laminated surface is substantially perpendicular to the runner 2C when it is within a range having a predetermined margin from 90-θ degrees to 90 + θ degrees. In addition, if the laminated surface is substantially perpendicular to the runner 2C, the surplus portion 9 is not generated in the remaining plastic 9, or if it is generated, the remaining plastic 9 can be easily taken out from the runner 2C.
In the first embodiment, the metal additive manufacturing method using a laser is used. However, any other method may be used as long as the layers are stacked one by one.
The above also applies to other embodiments.

Embodiment 2
In the second embodiment, the first embodiment is modified so that the electropolishing method is performed on the runner portion 2F so that the inner surface of the runner 2C becomes smoother. In FIG. 11, the enlarged view from the side surface of the runner part 2F of the same position as FIG. 7 is shown. Compared to FIG. 7, the stepped corners on the inner surface of the runner 2 </ b> C are rounded and the inner surface is smoother.

  FIG. 12 is a diagram illustrating a method for performing the electrolytic polishing method. The electrolytic bath 10 is filled with an electropolishing liquid 11 adjusted according to the type of metal of the runner portion 2F, and the runner portion 2F formed by the metal additive manufacturing method is immersed in the electropolishing liquid 11, and on the central axis 2H of the runner 2C. A rod-like counter electrode 12 having a circular cross section is disposed at a position where the distance from each part of the inner surface of the runner 2C becomes appropriate. A positive voltage is applied to the runner portion 2F and a negative voltage is applied to the counter electrode 12 from the DC power source 13 for a predetermined time.

  FIG. 13 shows a diagram for explaining the principle of electropolishing. FIG. 13A shows the time immediately after the start of electropolishing, and FIG. 13B shows the time just before the end of electropolishing. In the figure, there is a counter electrode 12 at the center, and an inner surface of the runner 2C around. Between the counter electrode 12 and the inner surface of the runner 2C, there is a mucus layer 14 on the side close to the runner 2C, and the electropolishing liquid 11 is near the counter electrode 12. The mucus layer 14 is obtained by dissolving the metal of the runner portion 2F as ions and mixing it with the electrolytic polishing liquid 11. The runner portion 2F has a stepped shape, but the boundary between the mucus layer 14 and the electropolishing liquid 11 is less uneven than the stepped shape of the runner portion 2F. For this reason, the mucus layer 14 becomes thin at the stepped corner portion of the runner portion 2F, and the mucus layer 14 becomes thick at the stepped portion. The electric resistance of the electropolishing liquid 11 is small, and the electric resistance of the mucus layer 14 is considerably larger than that of the electropolishing liquid 11. For this reason, more current flows in the stepped protruding corner portion of the runner portion 2F where the mucus layer 14 becomes thinner, melting proceeds faster from the protruding corner portion, and unevenness on the stepped portion of the runner portion 2F is observed. Smoothes more smoothly.

By carrying out the electropolishing method in this way, the inner surface of the runner 2C becomes smooth, and it becomes easier to remove the residual plastic 9 from the runner 2C.
The method of electrolytic polishing may be other than the method shown in the second embodiment, and any method may be used as long as the inner surface of the runner 2C can be made smooth.

It is a perspective view explaining the shape of the plastic product used when describing embodiment of this invention. It is the top view which looked at the plastic product used on describing embodiment of this invention from the back surface. It is a top view of the metal mold | die for carrying out injection molding using the submarine gate in Embodiment 1 of this invention. It is sectional drawing from the side surface of the metal mold | die for carrying out injection molding using the submarine gate in Embodiment 1 of this invention. It is sectional drawing from the side of the metal mold | die and plastic product after injection molding using the submarine gate in Embodiment 1 of this invention. It is sectional drawing from the side surface of the runner part of the core metal mold | die immediately after forming with the metal additive manufacturing method in Embodiment 1 of this invention. It is sectional drawing from the side which expanded the front-end | tip part of the runner of the runner part of the core metal mold | die immediately after forming with the metal additive manufacturing method in Embodiment 1 of this invention. It is sectional drawing from the side surface of a core metal mold | die and a plastic product in the state which removed the mold mold | die in Embodiment 1 of this invention. It is sectional drawing from the side of the metal mold | die and plastic product in the state in which the plastic product in Embodiment 1 of this invention is removed. It is sectional drawing from the side which expanded the front-end | tip part of the runner of the runner part of a core metal mold | die at the time of forming the runner part in Embodiment 1 of this invention in the plane parallel to a parting surface by a metal additive manufacturing method. . It is sectional drawing from the side which expanded the front-end | tip part of the runner of the runner part of the core metal mold | die after implementing the electropolishing method in Embodiment 2 of this invention. It is a figure explaining the method of implementing the electropolishing method in Embodiment 2 of this invention. It is a figure explaining the principle of the electropolishing in Embodiment 2 of this invention.

Explanation of symbols

1: Plastic product 1A: Injection boss trace 1B: Extrusion pin trace 1C: Injection boss separation part 2: Core mold (male mold)
2A: Injection boss hole 2B: Gate 2C: Runner 2D: Extrusion pin 2E: Extrusion pin 2F: Runner part 2G: Extrusion pin receiving hole 2H: Central axis 2J: Extra space 3: Cavity mold (female mold)
3A: Sprue 4: Parting surface 5: Cavity part 8: Injection boss 9: Residual plastic 10: Electrolytic polishing liquid 11: Electrolytic tank 12: Counter electrode 13: DC power supply 14: Mucus layer

Claims (2)

In the male mold that contacts the female mold at the parting surface, forms a predetermined cavity filled with the molten material between the female mold, and has an injection boss hole that leads to the molten material connected to the cavity. A tapered tip inclined with respect to the parting surface has a runner that leads to the injection boss hole and guides the molten material, and has a runner portion manufactured by laminating on a plane substantially perpendicular to the runner. Characteristic male mold. The male mold according to claim 1, wherein the inner surface of the runner is electropolished.

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