JP2019151081A - Injection molding die and molding method - Google Patents

Abstract

To provide an injection molding die and a molding method, wherein a sink mark on a molded article is difficult to form even at a position apart from a gate.SOLUTION: The injection molding die 10 contains a molding space 4 for molding a molded article, one or a plurality of gates 6 for supplying a resin to the molding space 4, a die body 1 having a storage part 5 to which a part of the resin in the molding space 4 can be introduced, and an adjustment mechanism 3 for adjusting a volume of the storage part 5.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an injection mold and a molding method.

  In the injection mold, one or more gates are set. In a mold having multiple gates, the flow length of the resin can be adjusted, and the resin pressure can be applied uniformly during holding pressure, so that the occurrence of sink marks can be suppressed.

JP 7-214620 A

  In the above-described mold, it may be difficult to set the gate due to structural restrictions for using the hot runner. In that case, it may be difficult to suppress the occurrence of sink marks at a site that is far from the gate.

  An object of one embodiment of the present invention is to provide an injection mold and a molding method in which sink marks are unlikely to occur in a molded product even at a position away from a gate.

  One aspect of the present invention is a mold body having a molding space for molding the molded product, one or a plurality of gates for supplying resin to the molding space, and a reservoir capable of introducing a part of the resin in the molding space. And an adjustment mechanism that adjusts the volume of the storage section.

  The injection molding die further includes a hole forming portion that forms a hole in the molded product, and the opening of the storage portion facing the molding space is at least one of the hole forming portion with respect to the opening of the gate. The configuration may be on the back side.

  It is preferable that the opening of the storage part is formed at a position including the parting surface of the mold body.

  It is preferable that the injection mold further includes a heating unit that heats the resin in the storage unit.

  It is preferable that the opening of the storage part is formed close to the joining position of the resin introduced into the molding space from the gate and divided into a plurality by the hole forming part.

  One aspect of the present invention is a method of molding a resin using the injection mold, wherein the first step of introducing the resin into the molding space and the volume of the storage portion are increased by the adjustment mechanism. Thus, the second step of storing the resin in the molding space in the storage unit, and reducing the volume by the adjusting mechanism as the temperature of the resin in the molding space decreases, the storage unit There is provided a molding method having a third step of introducing the resin into the molding space and a fourth step of obtaining the molded product by solidifying the resin in the molding space.

According to one aspect of the present invention, since the storage portion and the adjustment mechanism are provided, a part of the resin in the storage portion can be introduced into the molding space in the pressure holding step. Therefore, a decrease in the resin pressure in the molding space can be suppressed. Therefore, it is possible to prevent the occurrence of sink marks even at locations away from the gate.
According to one aspect of the present invention, in the pressure-holding step, a part of the resin in the storage part is introduced into the molding space, thereby promoting the resin flow in the joining part. Therefore, it can suppress that the mechanical strength of the resin molded product falls due to the weld.

It is a block diagram of the metal mold | die for injection molding which concerns on embodiment. It is a figure which shows the structure of the metal mold | die for injection molding of FIG. (A) It is process drawing of the shaping | molding method using the injection mold of FIG. 1, and is the schematic diagram of the state which filled resin in molding space. (B) It is explanatory drawing of the junction part of resin. (A) It is process drawing following FIG. 3 (A), and is a schematic diagram in a state in which a part of resin flows into a storage part. (B) It is explanatory drawing of the junction part of resin. (A) It is process drawing following FIG. 4 (A), and is a schematic diagram of the state which is holding pressure using the resin in a storage part. (B) It is explanatory drawing of the junction part of resin. It is process drawing following FIG. 5 (A), and is a schematic diagram which shows the cross section which looked at the metal mold | die and the molded product from the side. FIG. 7 is a process diagram following FIG. 6, and is a schematic diagram showing a state where a molded product is taken out from the mold. It is a figure explaining the structure and operation | movement of the other example of an adjustment mechanism. It is a figure explaining the structure and operation | movement of the adjustment mechanism of FIG. It is a figure explaining the structure and operation | movement of the adjustment mechanism of FIG. It is a figure explaining the structure and operation | movement of the adjustment mechanism of FIG. It is a figure explaining the structure and operation | movement of the adjustment mechanism of FIG. It is a figure explaining the structure and operation | movement of the adjustment mechanism of FIG.

  Embodiments to which the present invention is applied will be described below in detail with reference to the drawings. Note that the drawings used in the following description are for explaining the configuration of the embodiment of the present invention, and the size, thickness, dimensions, etc. of each part shown in the drawings may be different from the actual dimensional relationship of the apparatus. is there.

[Injection mold]
FIG. 1 is a configuration diagram of an injection mold 10 according to the embodiment. FIG. 2 is a view showing the structure of the injection mold 10. The plan view means viewing from the vertical direction (Z direction) in FIG.

As shown in FIGS. 1 and 2, the injection mold 10 includes a mold body 1, a hole forming portion 2, and an adjustment mechanism 3.
As shown in FIG. 2, the mold body 1 includes a first mold 11 and a second mold 12. In FIG. 2, the first mold 11 is located above the second mold 12. A vertical direction (Z direction) in FIG. 2 is a facing direction of the first mold 11 and the second mold 12, and is a thickness direction of the molding space 4.

  The first mold 11 has a top wall 13 and a side wall 14. The top wall 13 is a rectangular wall portion in plan view. The side wall 14 is a wall portion depending from the peripheral edge of the top wall 13. The second mold 12 has a bottom wall 15 and a side wall 16. The bottom wall 15 is a rectangular wall portion in plan view. The side wall 16 is a wall portion standing on the periphery of the bottom wall 15.

  A molding space 4 is secured between the first mold 11 and the second mold 12. The molding space 4 has a shape corresponding to the resin molded product 50 to be manufactured (see FIG. 7). The top surface 13a of the first mold 11 (the lower surface of the top wall 13) and the bottom surface 15a of the second mold 12 (the upper surface of the bottom wall 15) face each other with the molding space 4 therebetween.

  The top surface 13a of the first mold 11 has a shape corresponding to the first surface 50a (see FIG. 7) of the resin molded product 50. The bottom surface 15a of the second mold 12 has a shape conforming to the second surface 50b of the resin molded product 50 (the surface opposite to the first surface 50a; see FIG. 7). The inner side surfaces 14a and 16a of the side walls 14 and 16 have a shape corresponding to the outer side surface of the resin molded product 50 (see FIG. 7).

  As shown in FIG. 1, the molding space 4 has, for example, a rectangular shape in plan view. The outer side surface 17 of the molding space 4 (the inner surfaces 14a and 16a of the side walls 14 and 16 shown in FIG. 2) includes a first surface 17a, a second surface 17b, a third surface 17c, and a fourth surface 17d. Have. The first to fourth surfaces 17a to 17d are perpendicular to the top surface 13a and the bottom surface 15a (see FIG. 2). The second surface 17b and the fourth surface 17d are perpendicular to the first surface 17a. The third surface 17c is parallel to the first surface 17a.

  As shown in FIG. 2, the hole forming portion 2 has a columnar shape (for example, a rectangular columnar shape) along the thickness direction (Z direction) of the molding space 4. The hole forming portion 2 has an upper end reaching the top surface 13 a of the first mold 11 and a lower end reaching the bottom surface 15 a of the second mold 12. The hole forming part 2 forms a through hole 51 (see FIG. 7) of the resin molded product 50.

  As shown in FIG. 1, the hole forming portion 2 is separated from the outer side surface 17 of the molding space 4 of the molds 11 and 12. The outer surface of the hole forming portion 2 (the inner side surface 18 of the molding space 4) has a first surface 18a, a second surface 18b, a third surface 18c, and a fourth surface 18d. The first to fourth surfaces 18a to 18d are perpendicular to the top surface 13a and the bottom surface 15a (see FIG. 2). The second surface 18b and the fourth surface 18d are perpendicular to the first surface 18a. The third surface 18c is parallel to the first surface 18a.

  The first surface 18a is parallel to the first surface 17a and faces the first surface 17a. The second surface 18b is parallel to the second surface 17b and faces the second surface 17b. The third surface 18c is parallel to the third surface 17c and faces the third surface 17c. The fourth surface 18d is parallel to the fourth surface 17d and faces the fourth surface 17d.

  Of the molding space 4, a space between the first surface 17a and the first surface 18a is referred to as a first space 4a. A space between the second surface 17b and the second surface 18b is referred to as a second space 4b. A space between the third surface 17c and the third surface 18c is referred to as a third space 4c. A space between the fourth surface 17d and the fourth surface 18d is referred to as a fourth space 4d.

  The mold body 1 is provided with one or more gates 6 for supplying the molten resin to the molding space 4. In the injection mold 10 shown in FIGS. 1 and 2, the number of gates 6 is one. The opening 6 a of the gate 6 is formed in the first surface 18 a of the hole forming portion 2. Therefore, the opening 6a is at a position facing the first space 4a.

  As shown in FIG. 2, the storage portion 5 is a space formed by storage grooves 19 and 20 formed in the parting surfaces 11 a and 12 a of the first mold 11 and the second mold 12, respectively. The storage grooves 19 and 20 are formed from the side surface 17 to the outer surface 21 of the molds 11 and 12. The cross-sectional shape of the storage grooves 19 and 20 (the shape of the cross section perpendicular to the length direction of the storage grooves 19 and 20) may be, for example, a semicircular shape, a V shape, and a rectangular shape. The cross-sectional shape of the storage unit 5 (the cross-sectional shape orthogonal to the length direction of the storage unit 5) may be, for example, a circular shape or a rectangular shape.

  As shown in FIG. 1, the inner end opening 5 a of the storage portion 5 is formed on the side surface 17 (third surface 17 c) and faces the third space 4 c of the molding space 4. The outer end opening 5 b of the reservoir 5 is formed on the outer surface 21. Since the opening 6a of the gate 6 is at a position facing the first space 4a, the third space 4c is located on the back side of the hole forming portion 2 with respect to the opening 6a. Therefore, the inner end opening 5a of the reservoir 5 is in a position close to the position where the molten resin introduced from the gate 6 joins.

  Since the storage part 5 is formed by the storage grooves 19 and 20 formed in the parting surfaces 11a and 12a, the inner end opening 5a is formed at a height position including the parting surfaces 11a and 12a. Therefore, when the resin molded product 50 (see FIG. 7) is taken out from the mold main body 1, the resin remaining in the storage portion 5 can be easily removed from the mold main body 1 together with the resin molded product 50. The portion outside the resin molded product 50 can be excised from the resin molded product 50 in the same manner as a normal resin gate portion.

  Since the inner end opening 5 a is formed in the third surface 17 c, the inner end opening 5 a is on the back side of the hole forming portion 2 with respect to the opening 6 a of the gate 6. Therefore, in the first step (resin introduction step) to be described later, the molten resin supplied from the opening 6a of the gate 6 cannot reach the storage part 5 at the shortest distance, and wraps around the hole forming part 2 for storage. Part 5 is reached.

The adjustment mechanism 3 includes a cylinder part 23, a piston part 24, and an insertion pin 25.
The piston part 24 is provided inside the cylinder part 23 and is movable in a direction approaching the mold body 1 and a direction away from the mold body 1 by hydraulic pressure or the like.

  The insertion pin 25 can move in a direction approaching the mold body 1 and a direction away from the mold body 1 in conjunction with the piston portion 24. The insertion pin 25 is formed in a rod shape (for example, a cylindrical shape), and is inserted into the storage portion 5 from the outer end opening 5b. For example, the insertion pin 25 can move back and forth between a forward position P1 (see FIG. 3A) and a backward position P2 (see FIG. 4A). The advancement of the insertion pin 25 is to move in a direction approaching the molding space 4. The retreat of the insertion pin 25 is to move in a direction away from the molding space 4.

  The advance position P1 is the position of the insertion pin 25 when the tip 25a reaches the inner end opening 5a of the storage unit 5. When the insertion pin 25 is at the forward position P1, the insertion pin 25 is inserted into the storage unit 5 over the entire length without any gap, so that the volume in which the resin can be introduced into the storage unit 5 is substantially zero. The reverse position P2 is a position that is retracted from the forward position P2. When the insertion pin 25 is in the retracted position P <b> 2, a space is secured in the reservoir 5 in front of the distal end 25 a of the insertion pin 25. Resin can be introduced into this space from the inner end opening 5a. Thus, the adjustment mechanism 3 can adjust the volume in which the resin can be introduced (that is, the volume in which the resin can be stored) in the storage unit 5 by the advance / retreat operation of the insertion pin 25.

  The adjustment mechanism 3 may have a heating unit. The heating unit can heat the insertion pin 25 and adjust the temperature of the resin in the storage unit 5.

[Molding method]
Next, a molding method using the injection mold 10 will be described with reference to FIGS. FIG. 3A is a process diagram of a molding method using the injection mold 10 and is a schematic diagram showing a state where the molding space 4 is filled with resin. FIG. 3B is an explanatory diagram of a resin junction. FIG. 4A is a schematic view of a state in which a part of the resin flows into the storage unit 5. FIG. 4B is an explanatory diagram of a resin junction. FIG. 5A is a schematic diagram of a state in which pressure holding is performed using the resin in the reservoir 5. FIG. 5B is an explanatory diagram of a resin junction. FIG. 6 is a schematic diagram showing a cross section of the injection mold 10 and the resin molded product 50 as viewed from the side. FIG. 7 is a schematic view of the resin molded product 50 taken out from the injection mold 10.

(First step: resin introduction step)
In the injection mold 10 shown in FIG. 3A, the insertion pin 25 of the adjustment mechanism 3 is in the forward movement position P1. Therefore, the volume in which the resin can be introduced in the reservoir 5 is almost zero.

  A molten resin 27 is introduced from the gate 6 into the molding space 4 of the mold body 1. The molten resin 27 is, for example, a thermoplastic resin. The molten resin 27 is introduced into the first space 4a from the opening 6a of the gate 6 and flows in two parts. One of the two resin flows is directed to the second space 4b, and the other is directed to the fourth space 4d. These two resin flows go around the hole forming portion 2 and merge in the third space 4c. As shown in FIG. 3 (B), the two resin flows cannot be completely fused at this junction, and a weld line 28 may be formed. Thereby, the molding space 4 is filled with the molten resin 27. The molten resin 27 is not introduced into the storage unit 5.

(Second step: Resin storage step)
As shown in FIG. 4A, the insertion pin 25 in the reservoir 5 is retracted by retracting the piston 24 in the adjustment mechanism 3. Thereby, a part of the molten resin 27 in the molding space 4 is introduced into the storage part 5 from the inner end opening 5a and stored. As shown in FIG. 4B, since a part of the molten resin 27 in the third space 4 c is introduced into the storage part 5, the weld line 28 can be deformed so that the center part approaches the storage part 5. There is sex.

(Third step: pressure holding step)
As shown in FIG. 5A, the piston portion 24 and the insertion pin 25 are advanced in the adjustment mechanism 3 as the temperature of the molten resin 27 decreases. Thereby, a part of the molten resin 27 in the reservoir 5 is introduced into the molding space 4 (third space 4c). Therefore, a decrease in the pressure of the molten resin 27 in the molding space 4 can be suppressed. Therefore, although the third space 4c is far away from the gate 6, it is possible to prevent the occurrence of sink marks in the third space 4c.

  In this step, not only the resin supply from the storage unit 5 to the molding space 4 but also the resin pressure from the gate 6 may suppress the resin pressure drop in the first space 4a. As a result, a high sink occurrence suppressing effect can be obtained with less energy. Therefore, it is advantageous in terms of energy saving.

As shown in FIG. 5B, a part of the molten resin 27 in the storage unit 5 is introduced into the molding space 4 to promote the flow of the resin in the junction. Therefore, it can suppress that the mechanical strength of the resin molded product falls due to the weld.
When the molten resin 27 is heated by the heating unit in the storage unit 5, the molten resin 27 having a high temperature is introduced into the molding space 4, so that the resin in the junction is heated and the resin in the weld line 28 is heated. The surface condition at the interface is improved.

(4th process: molding process)
As shown in FIG. 6, the molten resin 27 is solidified by lowering the temperature of the molten resin 27. The cooled and solidified molten resin 27 becomes a resin molded product 50.
As shown in FIG. 7, the molds 11 and 12 are opened and the resin molded product 50 is taken out. At this time, the hole forming portion 2 is extracted from the resin molded product 50. In the resin molded product 50, a portion where the hole forming portion 2 was present becomes a through hole 51. The through hole 51 is formed through the resin molded product 50 in the thickness direction from the first surface 50 a to the second surface 50 b of the resin molded product 50.

  According to the injection mold 10, since the storage portion 5 and the adjusting mechanism 3 are provided, in the third step (pressure holding step), a part of the molten resin 27 in the storage portion 5 is formed in the molding space 4 (third space). 4c). Therefore, a decrease in the pressure of the molten resin 27 in the molding space 4 can be suppressed. Therefore, although the third space 4c is far away from the gate 6, it is possible to prevent the occurrence of sink marks in the third space 4c.

  According to the injection mold 10, in the third step (pressure-holding step), a part of the molten resin 27 in the reservoir 5 is introduced into the molding space 4, thereby promoting the resin flow in the junction. It is. Therefore, it can suppress that the mechanical strength of the resin molded product falls due to the weld.

  In addition, the storage part can also be formed at a position close to the gate. For example, the storage portion can be formed facing the same space (for example, the first space 4a in FIG. 1) as the space in which the gate is formed among the first to fourth spaces of the molding space. In that case, it is not necessary to supply resin from the gate to the molding space in the pressure holding step. Therefore, since the injection unit for resin supply from the gate can immediately enter the weighing operation after the resin supply (first step and second step), the cycle time for molding the resin molded product is shortened. , Can increase productivity.

[Other examples of adjustment mechanism]
8-13 is a figure explaining the structure and operation | movement of the adjustment mechanism 30 which are the other examples of an adjustment mechanism.
As shown in FIG. 8, the adjustment mechanism 30 includes a cylinder part 33, a piston part 34, a closing body 35, a moving mechanism 36, and a heating part 37. The piston part 34 is provided in the cylinder part 33. The piston part 34 is movable in the front-rear direction (vertical direction in FIG. 8) within the cylinder part 33 by hydraulic pressure or the like.

The closing body 35 is formed in a rod shape (for example, a columnar shape), and is movable in the front-rear direction (vertical direction in FIG. 8). The closing body 35 closes the flow hole 39 of the cylinder part 33 in the forward position shown in FIG. 8, and opens the flow hole 39 of the cylinder part 33 in the retracted position shown in FIG.
The moving mechanism 36 includes a cylinder part 41 and a piston part 42. The piston part 42 is provided in the cylinder part 41. The piston part 42 is connected to the closing body 35.
The heating part 37 is provided on the outer peripheral surface of the cylinder part 33, and can heat the resin in the space (front space 40) on the front side of the piston part 34 in the cylinder part 33.

Next, the operation of the adjustment mechanism 30 will be described.
(First step: resin introduction step)
As shown in FIG. 8, in the first step, the closing body 35 moves forward, and the flow hole 39 of the cylinder portion 33 is closed.

(Second step: Resin storage step)
As shown in FIG. 9, in the second step, the closing body 35 is moved backward by the moving mechanism 36 to open the flow hole 39. As shown in FIG. 10, when the piston portion 34 is retracted, the molten resin 27 is introduced into the front space 40 through the flow hole 39. Since the front space 40 can store the molten resin 27, it functions as a second storage portion.

(Third step: pressure holding step)
As shown in FIG. 11, in the third step, the molten resin 27 in the front space 40 is introduced into the molding space 4 by advancing the piston portion 34. Thereby, the fall of the pressure in the shaping | molding space 4 can be suppressed, and generation | occurrence | production of sink can be prevented.

  As shown in FIG. 12, in the adjustment mechanism 30, the molten resin 27 in the front space 40 can be heated by the heating unit 37. As shown in FIG. 13, in the third step, since the molten resin 27 whose temperature has been increased by the heating unit 37 is introduced into the molding space 4, the resin at the junction is heated, and the surface state at the interface of the resin is Improved.

  In the adjustment mechanism 33, the molten resin 27 in the front space 40 can be heated in the third step, and the molten state can be maintained. Therefore, it is possible to cope with the molding of the resin molded product 50 that requires a longer holding time.

The technical scope of the present invention is not limited to the above-described embodiments, and includes those in which various modifications are made to the above-described embodiments without departing from the spirit of the present invention. In other words, the configuration described in the above-described embodiment is merely an example, and can be changed as appropriate.
For example, although the injection mold 10 of the embodiment shown in FIGS. 1 and 2 has the hole forming portion 2, a configuration without the hole forming portion is also possible.
In the injection mold 10, the through hole 51 is formed in the resin molded product 50 by the hole forming portion 2, but the hole formed in the resin molded product may not be a through hole. Therefore, the upper end or the lower end of the hole forming portion may not reach the inner surface of the molding space.
In the injection mold 10, the number of hole forming portions 2 is 1, but the number of hole forming portions may be plural. Therefore, a plurality of holes may be formed in the resin molded product.
The adjustment mechanism may be a small injection unit that can be directly connected to the mold body.

  DESCRIPTION OF SYMBOLS 1 ... Mold body, 2 ... Hole formation part, 3 ... Adjustment mechanism, 4 ... Molding space, 5 ... Storage part, 5a ... Inner end opening (opening of storage part), 6 ... Gate, 6a ... Opening (gate opening) 10) Injection mold, 11a, 12a ... Parting surface, 27 ... Molten resin, 50 ... Resin molded product, 51 ... Through hole (hole).

Claims (6)

A mold body having a molding space for molding the molded product, one or more gates for supplying resin to the molding space, and a storage part into which a part of the resin in the molding space can be introduced;
An injection mold comprising: an adjustment mechanism for adjusting a volume in the storage unit. Further comprising a hole forming part for forming a hole in the molded article,
2. The injection mold according to claim 1, wherein an opening of the storage portion facing the molding space is on a back side of the hole forming portion with respect to an opening of at least one of the gates.   The injection mold according to claim 1 or 2, wherein the opening of the reservoir is formed at a position including a parting surface of the mold body.   The injection mold according to any one of claims 1 to 3, further comprising a heating unit that heats the resin in the storage unit.   The injection mold according to claim 2, wherein the opening of the storage part is formed in the vicinity of a joining position of the resin introduced into the molding space from the gate and divided into a plurality by the hole forming part. . A method of molding a resin using the injection mold according to any one of claims 1 to 5,
A first step of introducing a resin into the molding space;
A second step of storing the resin in the molding space in the storage unit by increasing the volume of the storage unit by the adjustment mechanism;
A third step of introducing the resin in the reservoir into the molding space by reducing the volume by the adjustment mechanism as the temperature of the resin in the molding space decreases;
And a fourth step of obtaining the molded product by solidifying the resin in the molding space.

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