JP2012201026A - Mold for injection molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mold for injection molding, which can prevent quality deterioration of a molded product by cold slug.SOLUTION: The mold for injection molding 1 includes a molding space 5 for molding the molded product, and a runner 6 communicated to the molding space 5 through a gate 7 between a pair of mold members 2, 3, and a sprue 23 having an outlet port 25 opened to the runner 6 and formed on the one mold member 2 out of the pair of mold members 2, 3. A slug well 32 is formed on a part opposite to the outlet port 25 of the sprue 23 of a runner formed surface 31 of the other mold member 3 out of the pair of mold members 2, 3. A protrusion 34 projected to an outlet port 25 side is protruded on a bottom surface of the slug well 32.

Description

  The present invention relates to an injection mold.

  As a mold for injection molding, generally, a two-plate mold having a female fixed mold in which a cavity (concave part) is formed and a male movable mold in which a core (convex part) is provided. It has been known. In this injection mold, a molding space (cavity) for molding a molded product is formed between the cavity and the core by fitting the movable mold to the fixed mold so that the core is inserted into the cavity. Is done. In addition, in a conventional injection mold, a runner communicated with a molding space via a gate is formed between a fixed mold and a movable mold, and a sprue bush in which a sprue is formed in the fixed mold described above. Are fitted. The outlet of the sprue described above is opened toward the runner, and the sprue and the runner communicate with each other. In addition, a concave curved nozzle receiving surface that abuts the tip of the nozzle of the injection molding machine is formed at the sprue inlet portion of the sprue bush.

  According to the above-described conventional mold for injection molding, when the nozzle of the injection molding machine is applied to the nozzle receiving surface and the molten resin is injected into the sprue from the nozzle, the molten resin enters the runner from the outlet of the sprue. It flows into the molding space from the runner through the gate. Thereby, the molten resin is filled in the molding space and the runner, respectively. Next, the mold is cooled to solidify the molten resin filled in the mold. After that, by moving the movable mold in the direction away from the fixed mold, the resin molded body is released from the fixed mold, and further, by ejecting the resin molded body with an ejector pin provided in the movable mold, The resin molding is released from the movable mold. Thereafter, by cutting the gate portion of the resin molded body, the runner portion molded by the runner is separated from the molded product (product) molded by the molding space, and a molded product having a desired shape is obtained. There is also a method of separating the runner portion from the molded product by cutting the gate portion of the resin molded body when the resin molded body is ejected by the ejector pin.

  By the way, in the injection molding using the above-described injection molding die, the nozzle tip is in contact with the nozzle receiving surface of the sprue bush when the die is cooled, so that the temperature of the nozzle tip is lowered together with the die when the die is cooled. . As a result, the molten resin is cooled at the tip of the nozzle and cold slag (solidified high-viscosity resin) is generated. In this state, when the molten resin is injected into the mold to form the next molded product, the cold slag at the tip of the nozzle may be washed away by the molten resin and enter the molding space. Since cold slag is difficult to bond with the molten resin, when cold slag enters the molding space, an interface is formed between the cold slag and the molten resin in the molded product, and a flow mark is generated in the molded product. It becomes easy to break and quality deteriorates.

  Therefore, conventionally, as described in Patent Document 1 below, for example, an injection mold in which a heat insulating material is interposed between a nozzle receiving portion of a sprue bush and a bush body has been proposed. According to this injection molding die, since the nozzle receiving portion is insulated from the bushing main body, the temperature drop of the nozzle receiving portion when the bushing main body is cooled is suppressed, and comes into contact with the nozzle receiving portion. The temperature at the nozzle tip is also difficult to decrease. Thereby, generation | occurrence | production of cold slag can be suppressed.

Japanese Unexamined Patent Publication No. 2000-6198

  However, in the conventional injection mold described above, if the heat insulating effect by the heat insulating material is insufficient, the temperature at the nozzle tip may be lowered and cold slag may be generated. Sometimes cold slag enters the molding space, which may reduce the quality of the molded product.

  Further, conventionally, a technique for forming a concave slag well (slag reservoir) in a portion of the movable runner molding surface facing the sprue outlet is known. Even if the cold slag discharged from the inside once enters the slag well, the molten resin may flow out of the slag well and enter the molding space.

  The present invention has been made in consideration of the above-described conventional problems, and an object of the present invention is to provide an injection mold that can prevent deterioration of the quality of a molded product due to cold slag.

The injection mold according to the present invention has the following features in order to solve the above-described problems.
That is, in the injection molding die according to claim 1 of the present application, a molding space for molding a molded product and a runner communicated with the molding space via a gate are formed between a pair of mold members, In a mold for injection molding in which one of the pair of mold members is formed with a sprue having an outlet opening toward the runner, the other mold member of the pair of mold members A slag well is formed in a portion of the runner molding surface facing the outlet of the sprue, and a protruding portion protruding toward the outlet is provided on the bottom surface of the slag well. It is a feature.

  Moreover, the injection mold according to claim 2 of the present application is characterized in that the protrusion is formed in a sharp shape.

According to the injection mold according to the present invention, the following actions and effects can be achieved by the above-described solving means.
That is, in the injection mold according to claim 1 of the present application, after the molten resin is injected into the sprue from the nozzle of the injection molding machine and the molten resin is filled in the mold (molding space and runner), the mold When the resin is cooled to solidify the molten resin, the temperature at the tip of the nozzle may drop and cold slag may be generated at the tip of the nozzle. In this case, when the molten resin is injected into the mold to form the next molded product, the cold slag at the tip of the nozzle is pushed away by the molten resin and enters the sprue, and is conveyed to the outlet side of the sprue. . The cold slag is discharged from the sprue outlet and enters the slag well. At this time, since a protruding portion protruding toward the outlet side of the sprue is provided on the bottom surface of the slag well, the cold slag is held by the protruding portion, and the cold slag is outside the slag well by the molten resin. It is prevented from being washed away. Thereby, even if cold slag is generated, the cold slag is not conveyed into the molding space, and it is possible to prevent deterioration of the quality (flow mark, crack, etc.) of the molded product due to cold slag.

  Moreover, according to the injection mold according to claim 2 of the present application, when the cold slag enters the slag well, the cold slag is stuck in the protruding portion, and the cold slag is securely held. Thereby, it is possible to reliably prevent the cold slag from being conveyed into the molding space, and it is possible to more reliably prevent the deterioration of the quality of the molded product due to the cold slag.

It is sectional drawing of the metal mold | die for injection molding which showed the state before molten resin injection for demonstrating embodiment of this invention. It is sectional drawing of the metal mold | die for injection molding which showed the state after molten resin injection for demonstrating embodiment of this invention.

  Hereinafter, an embodiment of an injection mold according to the present invention will be described with reference to the drawings.

  An injection mold 1 shown in FIG. 1 is a mold for injection molding a molded product made of synthetic resin, and includes a female fixed mold 2 (one mold member) in which a cavity 20 is formed, and a core. It has a two-plate structure including a male movable mold 3 (the other mold member) on which 30 is projected. The injection mold 1 in this embodiment is a mold for forming a cylindrical molded product, and by fitting the movable mold 3 to the fixed mold 2 so as to insert the core 30 into the cavity 20, A cylindrical molding space 5 is formed between the cavity 20 and the core 30. The injection mold 1 in this embodiment is a disk gate structure mold, and is a disk-shaped runner formed between the cavity 20 and the core 30 at a position inside the cylindrical molding space 5. 6 is disposed, and the runner 6 and the molding space 5 are communicated with each other via a gate 7 formed over the entire outer edge of the runner 6. In addition, the molded product shape | molded with the metal mold | die 1 for injection molding of this embodiment is a multistage (2 steps | paragraph) round pipe with which the large diameter cylinder part and the small diameter cylinder part were connected via the taper cylinder part.

  The fixed mold 2 described above is a fixed mold plate fixed to a mounting plate (not shown). The fixed mold 2 includes a recess (cavity 20) opened on the parting surface 26 side (movable mold 3 side). Is formed. The inner peripheral surface of the cavity 20 is a molding surface for molding the outer shape of the molded product. More specifically, the inner peripheral surface of the cavity 20 is reduced in diameter in a multistage shape (two steps) from the opening end side of the cavity 20 toward the bottom surface side through a tapered surface.

  Further, a columnar convex portion 27 protruding toward the opening end side of the cavity 20 is projected from the central portion of the bottom surface of the cavity 20. The outer peripheral surface of the convex portion 27 is a molding surface that molds the inner peripheral surface of the small-diameter portion of the molded product, and the tip surface (left end surface in FIG. 1) of the convex portion 27 is a runner that molds the runner 6. A molding surface 28 is formed.

  The fixed die 2 is provided with a sprue bush 21 in which a sprue 23 is formed. The sprue bush 21 is provided so as to penetrate from the base end surface (the surface opposite to the parting surface 26) of the fixed mold 2 to the runner molding surface 28 described above, and the tip surface of the sprue bush 21 faces the runner molding surface 28. It is formed in one. At the base end of the sprue bush 21 (the end on the base end face side of the fixed die 2), a concave curved nozzle receiving surface 22 with which the tip of the nozzle 13 of the injection molding machine 10 abuts is formed. . Further, the sprue bush 21 is formed with a tapered sprue 23 having a diameter gradually increased from the nozzle receiving surface 22 toward the tip end surface of the sprue bushing 21, and one end (inlet 24) of the sprue 23 is provided at the nozzle receiving surface. The other end (outflow port 25) of the sprue 23 is opened toward the runner 6 at the front end surface of the sprue bush 21.

  The movable mold 3 is a movable mold plate that can move in a direction away from the fixed mold 2. The movable mold 3 includes a convex portion (core 30) that protrudes into the cavity 20 from the parting surface 36 side. Is protruding. The outer peripheral surface of the core 30 is a molding surface for molding the inner shape of the molded product. More specifically, the outer peripheral surface of the core 30 is reduced in diameter in a multistage shape (two steps) from the proximal end of the core 30 toward the distal end side through a tapered surface. Further, the front end surface of the core 30 (the right end surface in FIG. 1) is opposed to the runner molding surface 28 of the cavity 20 with a space therebetween, and serves as a runner molding surface 31 for molding the runner 6.

  Further, a slag well 32 is formed in a portion of the runner molding surface 31 of the movable mold 3 that faces the outlet 25 of the sprue 23. The slag well 32 is a bottomed round hole-shaped concave portion opened toward the runner 6 side, and is formed to have a diameter larger than at least the outlet 25 of the sprue 23.

  A plurality of projecting portions 34 projecting toward the outflow port 25 are provided on the bottom surface of the slag well 32. The above-described protrusion 34 is a spine-shaped protrusion formed in a sharp shape, and specifically, is formed in a conical shape whose diameter is gradually reduced toward the distal end side. The protruding length of the protrusion 34 is shorter than the depth of the slag well 32, and the protrusion 34 has a length that does not protrude toward the runner 6 from the opening end of the slag well 32. The plurality of protrusions 34 are evenly arranged on the bottom surface of the slag well 32 at intervals.

  Next, the operation of the injection mold 1 having the above-described configuration will be described.

  When a molded product is molded using the above-described injection mold 1, first, the movable mold 3 is moved to the fixed mold 2 side so that the respective parting surfaces 26 and 36 are aligned with each other in the cavity 20. The core 30 is inserted into the core. Thereby, the molding space 5 and the runner 6 are formed between the cavity 20 and the core 30. Further, the tip of the nozzle 13 of the injection molding machine 10 is brought into contact with the nozzle receiving surface 22 of the sprue bush 21 so that the inside of the nozzle 13 and the sprue 23 are communicated.

  Subsequently, as shown in FIG. 2, the screw 12 of the injection molding machine 10 is driven to inject the molten resin R in the barrel 11 from the tip of the nozzle 13 toward the inlet 24 of the sprue 23. Thereby, the molten resin R flows into the runner 6 from the outlet 25 through the sprue 23, flows into the molding space 5 from the runner 6 through the gate 7, and melts inside the molding space 5 and the runner 6. Resin R is filled.

  At this time, if the cold slag S is generated in the nozzle 13 due to the mold cooling at the time of the previous molding, the cold slag S is pushed away by the injected molten resin R and sprued from the inlet 24 of the sprue 23. 23 and is transported to the outlet 25 side of the sprue 23. Then, the cold slag S is discharged from the outlet 25 of the sprue 23 and enters the slag well 32, and is stuck and held in a sharp protrusion 34 protruding from the bottom surface of the slag well 32. This prevents the cold slag S from flowing out of the slag well 32 by the molten resin R.

  Next, the injection mold 1 is cooled by water cooling or the like, and after the molten resin R filled in the injection mold 1 (the molding space 5 and the runner 6) is solidified, the movable mold 3 is fixed. The resin molded body is released from the fixed mold 2 by moving in a direction away from the fixed mold 2 (left side in FIG. 2). Subsequently, the resin molded body is released from the movable mold 3 by ejecting the resin molded body with an ejector pin (not shown) provided in the movable mold 3. Thereafter, by cutting the gate portion of the resin molded body, the runner portion molded by the runner 6 is separated from the molded product (product) molded by the molding space, and a molded product having a desired shape is obtained.

  According to the injection mold 1 described above, even if the cold slag S is generated as described above, the cold slag S can be prevented from entering the molding space 5. Thereby, quality degradation (a flow mark, a crack, etc.) by the cold slag S in the molded product (part molded by the molding space 5) which becomes a product can be prevented. In addition, although the runner part shape | molded by the runner 6 forms the interface of cold slag S and molten resin R and a flow mark is formed or it becomes easy to break, this runner part is cut off from a molded article as mentioned above. There is no problem because it is a part.

  Further, according to the above-described injection mold 1, the protrusion 34 is formed in a sharp shape, and the cold slag S that has entered the slag well 32 is stuck and held in the protrusion 34. Can be securely held. Thereby, it is possible to reliably prevent the cold slag S from being conveyed into the molding space 5, and it is possible to more reliably prevent the quality deterioration of the molded product due to the cold slag S.

  Further, according to the injection mold 1 described above, since the plurality of protrusions 34 protrude from the bottom surface of the slag well 32, the cold slag S is fitted between the plurality of protrusions 34. The cold slug S is more strongly held. Thereby, it can prevent more reliably that the cold slag S is conveyed in the molding space 5, and can prevent the quality deterioration of the molded product by the cold slag S more reliably.

  Furthermore, according to the injection mold 1, the protrusion 34 has a length that does not protrude from the open end of the slag well 32 toward the runner 6. The flow of the molten resin R that has flowed into is not hindered by the protrusions 34, and the filling property of the molten resin R can be improved. Thereby, the molten resin R can be uniformly filled in the molding space 5, and the quality defect of the molded product due to the poor filling of the molten resin R can be prevented.

The embodiment of the injection mold according to the present invention has been described above. However, the present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the spirit of the present invention.
For example, in the embodiment described above, the fixed die 2 is provided with the sprue bushing 21, but the present invention has a configuration in which the nozzle receiving surface 22 and the sprue 23 are directly formed on the fixed die 2. There may be.

  In the above-described embodiment, the injection molding die 1 having a disc gate structure has been described. However, the present invention provides an injection molding die having another structure without departing from the spirit of the invention. Is also possible. For example, an injection mold having a film gate structure other than a disk gate may be used, and an injection mold having a pin gate structure, a side gate structure, a tab gate structure, or the like may be used.

  In the embodiment described above, an injection mold 1 for molding a multi-stage (two-stage) round pipe (molded product) in which a large-diameter cylindrical portion and a small-diameter cylindrical portion are connected via a tapered cylindrical portion. However, the present invention may be an injection mold 1 for molding a molded product having another shape.

  In the embodiment described above, the cavity 20 is formed in the fixed mold 2, the core 30 is formed in the movable mold 3, and the molding space 5 is formed between the cavity 20 and the core 30. In the invention, the shape of the molding surface of the fixed mold 2 or the movable mold 3 can be appropriately changed according to the shape of the molded product. For example, a cavity may be formed in the movable mold 2 and a core may be formed in the fixed mold 3, or a mold without a core can be used in the case of a molded product having no inner peripheral surface, for example. is there.

  In the above-described embodiment, a plurality of sharpened protrusions 34 are provided on the bottom surface of the slag well 32. However, in the present invention, a shape other than the sharpened shape, for example, the tip is formed in a convex curved shape. It is possible to form a columnar protrusion, and the number of protrusions 34 can be changed as appropriate, and it is also possible to adopt a configuration in which only one protrusion 34 protrudes from the bottom surface of the slag well 32. is there.

  In addition, in the range which does not deviate from the main point of this invention, it is possible to replace suitably the component in above-mentioned embodiment with a well-known component, and you may combine the above-mentioned modification suitably.

1 Mold for injection molding 2 Fixed mold (one mold member)
3 Movable type (the other mold member)
5 Molding space 6 Runner 7 Gate 23 Spru 25 Outlet 31 Runner molding surface 32 Slag well 34 Projection

Claims (2)

A molding space for molding a molded product and a runner communicated with the molding space via a gate are formed between the pair of mold members, and one of the pair of mold members is attached to the runner. In an injection mold in which a sprue having an outlet opening facing is formed,
Of the runner molding surface of the other mold member of the pair of mold members, a slag well is formed in a portion facing the outlet of the sprue,
An injection mold, wherein a protrusion projecting toward the outlet side is provided on the bottom surface of the slag well. In the injection mold according to claim 1,
An injection mold, wherein the protrusion is formed in a sharp shape.

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