Method for manufacturing injection molding dies and injection molded products
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- INOAC CORP
- Filing Date
- 2024-12-25
- Publication Date
- 2026-07-07
Smart Images
Figure 2026112530000001_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to an injection mold and a method for manufacturing an injection molded product.
Background Art
[0002] As a conventional injection mold, one capable of molding an injection molded product having a flat surface is known (see, for example, Patent Document 1).
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
[0020] , FIG. 2A)
Summary of the Invention
Problems to be Solved by the Invention
[0004] In the above-described conventional injection mold, improvement in molding quality is required.
Means for Solving the Problems
[0005] One aspect of the invention made to solve the above problems is an injection mold including a first mold and a second mold that are opened and closed with a cavity therebetween. The first mold includes a base portion and a movable portion movable with respect to the base portion. The movable portion is movable between a first position when filling of molten resin into the cavity is started and a second position where the capacity of the cavity is larger than the first position. The injection mold includes moving means for moving the movable portion from the second position to the first position in a mold closed state between the base portion of the first mold and the second mold.
Brief Description of the Drawings
[0006] [Figure 1] FIG. 1 is a perspective view of an injection molded product according to the first embodiment [Figure 2]Figure 2 is a side view of the injection molding machine. [Figure 3] Figure 3 is a side cross-sectional view of an injection molding die. [Figure 4] Figure 4A is an enlarged cross-sectional view of the injection molding die before molten resin is filled in, Figure 4B is an enlarged cross-sectional view of the injection molding die after molten resin has been filled in and the movable part has moved to the second position, and Figure 4C is an enlarged cross-sectional view of the injection molding die after the movable part has returned to the first position. [Figure 5] Figure 5 is a side cross-sectional view of the injection molding die near the retaining stopper. [Figure 6] Figure 6 is an enlarged cross-sectional view of the injection molding die of the second embodiment. [Modes for carrying out the invention]
[0007] [First Embodiment] Referring to Figures 1 to 5, an injection molding die 10 of a first embodiment of the present disclosure will be described. Figure 1 shows an example of an injection molded product 100 formed by the injection molding die 10. As shown in Figure 1, the injection molded product 100 has a pair of product parts 101 arranged symmetrically on both sides of a non-product part 102. Each product part 101 includes, for example, a substantially oval plate part 105 and a pair of arm parts 106 perpendicular to the back surface 104 of the plate part 105. The pair of arm parts 106 are also arranged at both ends in the longitudinal direction of the plate part 105. In the injection molded product 100 as a whole, the pair of plate parts 105 are located in the same plane, and their planar shapes, which are substantially oval, are arranged so that their major axes (not shown) are aligned in a straight line.
[0008] The surface of the product part 101 is a decorative surface 103, and since it is decorated by laminating metal layers or the like in a post-formation process, a high degree of flatness is required. For this reason, the decorative surface molding surface 42A of the injection molding die 10, which will be described later, is also processed to a high degree of flatness and given a mirror finish. However, if the molten resin G filled inside the cavity 50 of the injection molding die 10 is not molded according to the decorative surface molding surface 42A, a high degree of aesthetic appeal cannot be expected for the decorative surface 103 of the product part 101. In contrast, the injection molding die 10 of this embodiment has a structure for molding the decorative surface 103 of the product part 101 with high molding accuracy, as will be described below.
[0009] The non-product portion 102 of the injection-molded product 100 consists of resin remaining in the sprue 32 and runner 26 of the injection molding die 10 (described later), and comprises a sprue portion 102A and a runner portion 102B. The runner portion 102B is bent in a crank shape, with both ends and the central part offset in a stepped manner. The central part of the runner portion 102B is located in approximately the same plane as the plate portion 105, and both ends are perpendicular to the sides of the tips of the pair of arm portions 106 on the sides closest to each other of the two product portions 101. The sprue portion 102A extends parallel to the arm portions 106 and penetrates the central part of the runner portion 102B from front to back. The portion of the sprue portion 102A that extends to the back side of the runner portion 102B is cylindrical, while the portion that extends to the front side is tapered, becoming narrower as it moves away from the runner portion 102B.
[0010] As shown in Figure 2, the injection mold 10 is assembled to the injection molding machine body 110H as part of the injection molding machine 110. Figure 3 shows the entire injection mold 10 as a standalone unit. As shown in Figure 3, the injection mold 10 comprises a movable mold 20 and a fixed mold 30. The fixed mold 30 is fixed to the fixed-side support portion 31 on the injection machine 111 side of the injection molding machine body 110H. On the other hand, the movable mold 20 is fixed to the movable-side support portion 21 of the injection molding machine body 110H and moves toward or away from the fixed mold 30.
[0011] Hereinafter, in the movable mold 20 and the fixed mold 30, the side facing each other will be referred to as the "front side," and the opposite side as the "rear side." Furthermore, unless otherwise specified, the shape and arrangement of each component will be described assuming that the injection molding die 10 is in a closed state with the movable mold 20 and the fixed mold 30 in contact. In this embodiment, the fixed mold 30 corresponds to the "first mold" in the claims, and the movable mold 20 corresponds to the "second mold."
[0012] Between the front surfaces of the movable mold 20 and the fixed mold 30, there is a pair of cavities 50 corresponding to a pair of product sections 101. Between the cavities 50 and the nozzle hole 112A to which the tip of the nozzle 112 (see Figure 2) of the injection machine 111 abuts, there is a sprue 32 and a runner 26 corresponding to the sprue section 102A and runner section 102B (see Figure 1). Each cavity 50 has a parting line L formed along the joint between the back surface 104 and the side surface 103A of the product section 101 (see the same figure).
[0013] The sprue 32 penetrates the fixed mold 30 in the mold closing direction, and its lower end is positioned in front of the movable mold 20. The runner 26 is formed between the fixed mold 30 and the movable mold 20, and extends outwards from a position near the bottom of the sprue 32, each connected to the cavity 50. The molten resin G entering from the nozzle hole 112A passes through the sprue 32 and runner 26 and flows into the cavity 50. The molten resin G in one pair of cavities 50 is then molded into one pair of product parts 101 (see Figure 1), and the molten resin G in the sprue 32 and runner 26 becomes the non-product part 102 (see the same figure) of the injection molded product 100.
[0014] The surfaces for forming the design surface 103 and the side surface 103A of the product section 101 are provided on the fixed mold 30. Specifically, the fixed mold 30 is provided with a pair of molding recesses 42, which are part of a pair of cavities 50. The bottom surface of each molding recess 42 forms the design surface molding surface 42A for forming the design surface 103 of the injection molded product 100, and the side surface of each molding recess 42 forms the side surface molding surface 42B for forming the side surface 103A of the injection molded product 100. The design surface molding surface 42A is a mirror-finished flat surface. Furthermore, the fixed mold 30 has the following structure in order to improve the molding accuracy of the design surface 103 of the product section 101.
[0015] The fixed mold 30 comprises a base portion 33 fixed to the fixed-side support portion 31 of the injection molding machine body 110H, and a pair of movable portions 40 supported so as to be movable in the mold closing direction (front-rear direction) relative to the base portion 33, with the molding recess 42 formed on the front surface of each movable portion 40.
[0016] Specifically, the base portion 33 has a flat front surface 31F that can contact the front surface 20F of the movable type 20, and the front surface 31F is provided with a pair of support recesses 35 that open toward the front surface 20F of the movable type 20. The pair of support recesses 35 have, for example, a non-circular shape when viewed from the front-rear direction, and a pair of movable parts 40 are housed inside each of them. The movable parts 40 are permitted to move only in the front-rear direction within the support recesses 35, and movement and rotation in other directions are restricted.
[0017] The movable part 40 has a flat front surface 40F that can contact the front surface 20F of the movable mold 20, and a molded recess 42 is formed in the front surface 40F. When the front surface 40F of the movable part 40 contacts the front surface 20F of the movable mold 20, the movable part 40 is positioned at the first position, which is the front end of the movable range. A stopper 36 is provided on the bottom surface 35A of the support recess 35. When the rear surface 40R of the movable part 40 contacts the stopper 36, the movable part 40 is positioned at the second position, which is the rear end of the movable range. As will be described in detail later, the first position is the position when the filling of molten resin G into the cavity 50 begins, and the second position is the position where the volume of the cavity 50 is larger than that of the first position. The movable part 40 moves between the first position and the second position when the mold is closed between the base part 33 of the fixed mold 30 and the movable mold 20. The movable stroke of the movable part 40 is, for example, 0.01 to 0.1 mm. Note that in Figures 3 to 6, the movable stroke is exaggerated for illustrative purposes.
[0018] In this embodiment, the stopper 36 is, for example, a projection protruding from the bottom surface 35A of the support recess 35, but the entire bottom surface 35A of the support recess 35 may also serve as the stopper. Furthermore, the stopper 36 may be a rigid body or an elastic body. A rigid body is suitable for achieving a highly accurate movable stroke, while an elastic body is suitable for absorbing the impact when the movable part 40 moves to the second position. In this embodiment, a rigid body (metal) is used as the stopper 36.
[0019] Also, although omitted in FIGS. 3 and 4, as shown in FIG. 5, between the movable part 40 and the base part 33, in the mold opening state where the movable mold 20 is separated from the fixed mold 30, the movable part 40 abuts against the base part 33 at a third position (a position farther from the second position than the first position) where the movable part 40 slightly protrudes from the front surface of the base part 33, and a retaining mechanism is provided to prevent the movable part 40 from coming out of the support recess 35. The retaining mechanism is formed, for example, by a retaining protrusion 37 protruding from the side surface of the movable part 40 being loosely fitted into a retaining recess 37A formed in the base part 33. Note that the retaining mechanism may have a configuration other than the above as long as it can regulate the movable part 40 from falling out of the support recess 35. Also, a configuration without a retaining mechanism may be adopted.
[0020] An elastic member 63 is provided between the rear surface 40R of the movable part 40 and the bottom surface 35A of the support recess 35. The elastic member 63 is, for example, a compression coil spring, and both ends are received in spring receiving recesses formed in the rear surface 40R of the movable part 40 and the bottom surface 35A of the support recess 35. In the mold opening state described above, the elastic member 63 is compressed and deformed, and the movable part 40 is biased to the third position by its elastic force.
[0021] In this embodiment, a compression coil spring is used as the elastic member 63, but any member that can apply a force in the mold closing direction to the movable part 40, such as a leaf spring, may be used. Also, the elastic member 63 may not be provided.
[0022] The fixed mold 30 is provided with a pair of hydraulic cylinders 60 as drive sources for moving the pair of movable parts 40 to the first position. Each hydraulic cylinder 60 has a rod 60R that linearly moves in a direction intersecting the moving direction of the movable part 40. Note that the elastic member 63 and the hydraulic cylinder 60 correspond to the "moving means" in the claims.
[0023] The base portion 33 is provided with a pair of through holes 60A that extend in a direction perpendicular to the front-rear direction and penetrate from the outer surface of the base portion 33 into a pair of support recesses 35. The cylinder body 60H of each hydraulic cylinder 60 is fixed to the base portion 33, and the rod 60R of the hydraulic cylinder 60 is received in the through holes 60A.
[0024] A wedge-shaped member 62 is connected to the rod 60R, and this wedge-shaped member 62 moves linearly with the rod 60R and is pushed between the base portion 33 and the movable portion 40. The wedge-shaped member 62 is provided with a sliding contact slope 62S that faces diagonally forward, and correspondingly the movable portion 40 is provided with a sliding contact slope 40S that faces diagonally backward, so that the sliding contact slopes 40S and 62S are in surface contact with each other. The hydraulic cylinder 60 is also configured by a valve (not shown) to switch between a pushing state, which pushes the wedge-shaped member 62 away from the cylinder body 60H, and a pulling state, which pulls it towards the cylinder body 60H. When the hydraulic cylinder 60 is in the pushing state, the wedge-shaped member 62 is pushed, and the movable portion 40 is pushed forward. In other words, in this embodiment, a wedge-shaped member 62 having a sliding contact slope 62S and a movable part 40 having a sliding contact slope 40S constitute a power conversion mechanism that converts the power of the hydraulic cylinder 60 into force in the direction of movement of the movable part 40.
[0025] Furthermore, since the sliding inclined surfaces 40S and 62S are angled at an angle of 45 degrees or more with respect to the front-rear direction, that is, the direction of movement of the movable part 40, the power of the hydraulic cylinder 60 can be amplified and applied to the movable part 40. Specifically, if the sliding inclined surfaces 40S and 62S are at a 45-degree angle with respect to the direction of movement of the movable part 40, then in order to move the movable part 40 by, for example, 0.1 mm, the wedge-shaped member 62 will move by 0.1 mm, and the movement of the wedge-shaped member 62 will be transmitted as the movement of the movable part 40 without deceleration (i.e., transmitted with a reduction ratio of 1), and the power of the hydraulic cylinder 60 will be applied to the movable part 40 without amplification.
[0026] In contrast, in this embodiment, the sliding contact inclined surfaces 40S and 62S are laid at an angle of 45 degrees or more with respect to the direction of movement of the movable part 40. Therefore, in order to move the movable part 40 by, for example, 0.1 mm, the wedge-shaped member 62 must be moved by a distance greater than 0.1 mm. As a result, the movement of the wedge-shaped member 62 is reduced and transmitted as the movement of the movable part 40, and the reduction ratio becomes greater than 1. Consequently, the power of the hydraulic cylinder 60 is amplified by the reduction ratio and applied to the movable part 40. Here, the forward pressing force of the movable part 40 driven by the hydraulic cylinder 60 is adjusted so that the resultant force, which is the same as the elastic force of the elastic member 63, does not become large enough to push the movable mold 20 and the fixed mold 30 apart when the mold is closed.
[0027] Next, a method for manufacturing an injection-molded product 100 using an injection molding die 10 will be described.
[0028] (1) Immediately before the molten resin is filled into the cavity 50, the injection molding die 10 is held in a closed position and heated. At this time, the hydraulic cylinder 60 is positioned in a retracted position, and the movable part 40 is held in the first position by the elastic force of the elastic member 63 and friction with the base part 33 (see Figure 4A).
[0029] (2) With the movable part 40 held in the first position, the injection machine 111 starts filling the pair of cavities 50 of the injection molding die 10 with molten resin G. At this time, the filling pressure of the molten resin G that has increased in each cavity 50 causes each movable part 40 to retract from the first position to the second position, compressing and deforming the elastic member 63. When each movable part 40 retracts to the second position, the volume of each cavity 50 becomes larger than when it was held in the first position (see Figure 4B).
[0030] (3) Next, the supply of molten resin G from the injection machine 111 is stopped, and the injection mold 10 is cooled. As a result, the molten resin G in the cavity 50 solidifies, and the molten resin G begins to shrink. In this embodiment, the hydraulic cylinder 60, which is switched to a pressing state as soon as cooling begins, moves the wedge-shaped member 62 (rod 60R) in a straight line, thereby pushing the movable part 40 in a direction that reduces the volume of the cavity 50, moving from the first position to the second position. In addition, as the molten resin G shrinks, the elastic member 60 elastically returns to its original position, which also pushes the movable part 40 in a direction that reduces the volume of the cavity 50. In this case, the movable part 40 is pushed in a direction that presses the design surface 42A contained in its molding recess 42 against the molten resin G. As a result, the molten resin G solidifies while gradually shrinking, maintaining the state in which the design surface 42A is pressed against it (see Figure 4C).
[0031] (4) The injection molding die 10 is opened after all the molten resin G inside the cavity 50 has solidified. At this time, the injection molded product 100 made of the solidified molten resin G is held in the movable mold 20. It is then separated from the movable mold 20 by the knockout pin 23 (see Figure 3) and ejected from inside the injection molding die 10. After the hydraulic cylinder 60 is returned to the pulled position, the inside of the injection molding die 10 is closed, returning to the initial state and the next injection molded product 100 is molded.
[0032] As described above, in the manufacturing method of the injection molding die 10 and injection molded product 100 of this embodiment, after the molten resin G is filled into the cavity 50, the decrease in resin pressure due to the shrinkage of the molten resin G is suppressed. Therefore, the molding quality of the injection molded product 100 is improved.
[0033] Specifically, as in this embodiment, if the design surface molding surface 42A is a mirror-finished flat surface, when the molten resin G filled in the cavity 50 solidifies, the molten resin G shrinks and the pressure pressing against the design surface molding surface 42A decreases, which can cause sink marks on the design surface 103. As a result, the design surface 103 may take on a distorted wave shape, for example, and molding errors between it and the design surface molding surface 42A can become a problem.
[0034] However, in the injection molding die 10 of this embodiment, after the molten resin G is filled into the cavity 50, the movable part 40 is moved from the second position to the first position so that the volume of the cavity 50 decreases, thereby suppressing the decrease in resin pressure in the cavity 50 due to the shrinkage of the molten resin G. As a result, the problem of molding errors due to sink marks is eliminated, and the molding quality is improved.
[0035] Here, it is conceivable to omit the movable part 40 in the injection molding die 10, fill the cavity 50 with molten resin G, and then apply injection pressure of the molten resin G into the cavity 50 using the injection machine 111 (see Figure 2) to prevent a decrease in the pressure of the molten resin G within the cavity 50 (i.e., maintain pressure). However, considering the pressure loss in the sprue 32 and runner 26 interposed between the injection machine 111 and the design surface molding surface 42A, and the progress of solidification of the molten resin G, it is difficult to maintain the pressure of the molten resin G on the design surface molding surface 42A with the injection pressure of the molten resin G from the injection machine 111. Furthermore, if the output of the injection machine 111 is increased to ensure sufficient filling pressure, it is necessary to hold the injection molding die 10 in a closed state with a force that can withstand that output. Consequently, the drive mechanism for opening and closing the injection molding die 10 also becomes larger, and the entire injection molding machine 110 becomes larger.
[0036] In contrast, in this embodiment, the injection molding die 10 itself includes a movable part 40 for maintaining (i.e., holding pressure) the pressure of the molten resin G against the design surface molding surface 42A, and a hydraulic cylinder 60 and an elastic member 63 (moving means) for moving the movable part 40 so that the design surface molding surface 42A is pressed against the molten resin G. This makes it possible to efficiently hold pressure on the design surface molding surface 42A, which requires high molding accuracy, without increasing the size of the injection molding machine 110, and to achieve higher molding quality than when holding pressure is performed by the injection machine 111.
[0037] Alternatively, it is conceivable to perform the holding pressure by the minute clamping action of the injection molding die 10 without providing the movable part 40. Specifically, it is conceivable to close the fixed mold 30 and the movable mold 20, leaving a small gap between them so that molten resin G does not leak out, fill the cavity 50 with molten resin G, and then move the movable mold 20 by the amount of that small gap to perform the holding pressure. However, moving the entire large movable mold 20 back and forth by the amount of that small gap requires advanced technology and is therefore difficult to implement. In contrast, with the injection molding die 10 of this embodiment, holding pressure can be performed simply by moving the movable part 40, which is part of the fixed mold 30, making it easy to implement.
[0038] Furthermore, by equipping the injection molding die 10 with a movable part 40 capable of increasing the pressure inside the cavity 50, the target pressure at the time of completion of filling the cavity 50 with molten resin G can be lowered, thereby shortening the cycle time. In other words, if the target pressure is increased to improve molding accuracy, it takes a long time for the pressure of the molten resin G to reach the target pressure at the time of completion of filling the cavity 50 with molten resin G, resulting in a longer cycle time. In particular, if the cavity 50 or runner 26 has a complex shape, the molten resin G is difficult to flow and the pressure loss is large, so the cycle time becomes even longer. In contrast, by equipping the injection molding die 10 with a movable part 40 capable of increasing the pressure inside the cavity 50, the target pressure can be lowered, thereby shortening the cycle time.
[0039] Furthermore, in the injection molding die 10 of this embodiment, the filling pressure when the molten resin G is filled into the cavity 50 causes the movable part 40 to move toward the second position and the elastic member 63 to elastically deform. Then, when the molten resin G shrinks, the movable part 40 is pushed by the elastic member 63 and moves toward the first position in a direction that reduces the volume of the cavity 50. That is, elastic energy is stored in the elastic member 63 by the filling pressure of the molten resin G, and this elastic energy causes the movable part 40 to move toward a direction that reduces the volume of the cavity 50, thereby suppressing a decrease in the pressure of the molten resin G filled in the cavity 50.
[0040] Furthermore, since the output of the drive source is transmitted to the movable part 40 via the wedge-shaped member 62, it becomes possible to move the movable part 40 to the first position with a simple structure. In addition, since most resins used in injection molding do not easily enter gaps of 0.1 mm or less, it becomes unnecessary to provide a special shape on the parting line L between the movable part 40 and the second mold to prevent resin leakage from the cavity 50. This also allows for a simpler structure for the injection molding die 10.
[0041] Furthermore, the wedge-shaped member 63 and the movable part 40 convert the power of the hydraulic cylinder 60 into a force that moves the movable part 40 in a direction that reduces the volume of the cavity 50. This makes it possible to return the movable part 40 to the first position with a stable force and also makes it possible to control the timing of the movement of the movable part 40.
[0042] Furthermore, a stopper 36 is provided on the bottom surface 35A of the support recess 35 to position the movable part 40 in a second position. This prevents the cavity 50 from expanding more than necessary due to the filling pressure of the molten resin G, thereby stabilizing the amount of molten resin G filled into the cavity 50.
[0043] [Second Embodiment] Figure 6 shows the injection molding die 10A of the second embodiment. The injection molding die 10A differs from the first embodiment in that it does not have a hydraulic cylinder 60, and moves the movable part 40 using only a plurality of elastic members 70. Specifically, the elastic members 70 hold the movable part 40 in a first position until the molten resin G is injected from the injection machine 111. On the other hand, when the molten resin G fills the cavity 50, the elastic members 70 elastically deform under the pressure, allowing the movable part 40 to move to a second position. Then, the elastic members 70 elastically return to their original state as the pressure in the cavity 50 decreases, moving the movable part 40 back to the first position. This makes it possible to suppress the pressure drop in the cavity 50 with a simple configuration. [Other embodiments]
[0044] (1) In the above embodiment, the movable part 40 of the fixed mold 30 was provided with a molding recess 42, but the molding recess 42 may be provided on the movable mold 20 side, or on both sides.
[0045] (2) In the above embodiment, the arm portion 106 was provided on the back surface 104 of the product portion 101, but it may also be provided on the design surface 103 side, or on both sides.
[0046] (3) The passage for molten resin G within the injection molding die 10 may be structured such that the downstream end of the runner 26 is on the fixed mold 30 side of the parting line L. As in the above embodiment, if the downstream end of the runner 26 is on the movable mold 20 side of the parting line L, the filling pressure is more likely to be lost before reaching the cavity 50, so the effect of reducing the volume of the cavity 50 by providing a movable part 40 can be enjoyed to a greater extent.
[0047] (4) In the first embodiment, a hydraulic cylinder 60 was used as the drive source for moving the movable part 40, but for example, a motor combined with a ball screw or rack and pinion that converts its rotational output into linear motion may be used. In addition, any other device that can move the movable part 40 in the mold closing direction may be used.
[0048] (5) In the above embodiment, the movable part 40 moved in the mold closing direction, but it may also move in a direction perpendicular to the mold closing direction. If this is the case, for example, if the design surface 103 is provided with a flat surface perpendicular to the plate portion 105, it will be possible to maintain a high degree of flatness of that flat surface.
[0049] <Note> The following describes the features extracted from the above embodiment, explaining their effects and other aspects as needed. For ease of understanding, corresponding configurations in the above embodiment will be indicated in parentheses as appropriate, but these features are not limited to the specific configurations indicated in parentheses.
[0050] [Feature 1] In an injection molding die (10) comprising a first mold (30) and a second mold (20) that open and close with a cavity (50) between them, the first mold (30) includes a base portion (33) and a movable portion (40) that is movable relative to the base portion (33), the movable portion (40) being movable between a first position when filling of molten resin (G) into the cavity (50) begins and a second position in which the volume of the cavity (50) is larger than that of the first position, and the injection molding die (10) comprising moving means (60, 63, 40) for moving the movable portion (40) from the second position to the first position when the mold is closed between the base portion (33) of the first mold (30) and the second mold (20).
[0051] In the injection molding die (10) of Feature 1 and the manufacturing method of the injection molded product (100) of Feature 7, after the molten resin (G) is filled into the cavity (50), the movable part (40) provided on the injection molding die (10) is moved from the second position to the first position by the moving means (hydraulic cylinder 60 and elastic member 63), thereby reducing the volume of the cavity (50). This suppresses the contraction of the molten resin (G) filled into the cavity (50) and the decrease in the pressure of the molten resin (G), thereby improving the molding quality. Specifically, if the molding surface, which is the inner surface of the cavity (50), is, for example, a mirror-finished flat surface, and the molten resin (G) solidifies while the pressure of the molten resin (G) in the cavity (50) has decreased, sink marks will occur on the molded surface of the injection molded product (100), resulting in a slightly undulating wave shape. Therefore, molding errors between the molded surface of the cavity (50) and the molded surface of the injection-molded product (100) can become a problem. In contrast, according to the injection molding die (10) of Feature 1 and the manufacturing method of the injection-molded product (100) of Feature 7, it is possible to suppress the contraction of the molten resin (G) filled in the cavity (50) and the decrease in the pressure of the molten resin (G), thereby suppressing molding errors between the molded surface of the cavity (50) and the molded surface of the injection-molded product (100) and improving molding quality.
[0052] Furthermore, the inner surface of the cavity (50) in the first mold may be provided only on the movable part (40), or it may be provided on both the movable part (40) and the base part (33).
[0053] One possible method to suppress the pressure drop of the molten resin (G) filled in the cavity (50) is to replenish the resin in the injection mold (10) from the injection molding machine. However, in that case, due to pressure loss in the path from the injection molding machine to the cavity (50) and solidification of the resin, it may not be possible to replenish the pressure sufficiently, or even if it is possible, other problems may arise, such as the need to enlarge the injection molding machine. In contrast, as described above, in Feature 1 and Feature 7, the pressure inside the cavity 50 is replenished by the movement of the movable part (40) provided in the injection mold (10), so the above problems do not occur.
[0054] [Feature 2] The injection molding die (10) according to feature 1, wherein the moving means (60) includes a drive source (60, 60R) and a power conversion mechanism (40, 62) that converts the power of the drive source (60, 60R) into a force that moves the movable part (40) to the first position.
[0055] According to the injection molding die (10) of Feature 2, the power conversion mechanism (40, 62) converts the power of the drive source (60, 60R) to return the movable part (40) to the first position with a stable force. It is also possible to have both the configurations of Feature 2 and Feature 3.
[0056] [Feature 3] The injection molding die (10) according to feature 2, wherein the drive source includes a hydraulic cylinder (60) having a rod (60R) that moves linearly in a direction intersecting the direction of movement of the movable part (40), and the power conversion mechanism includes a wedge-shaped member (62) connected to the rod (60R) that moves linearly and is pressed between the base part (33) and the movable part (40).
[0057] According to the injection molding die (10) of Feature 3, the output of the drive source is transmitted to the movable part (40) via the wedge-shaped member (62), making it possible to move the movable part (40) to the first position with a simple structure. In addition, since the rod (60R) of the hydraulic cylinder (60) is provided to move in a direction perpendicular to the direction of movement of the movable part (40), it is possible to keep the injection molding die (10) compact in the mold opening direction.
[0058] [Feature 4] The injection molding die (10) according to Feature 1, wherein the moving means (63, 70) is provided between the base portion (33) and the movable portion (40), and includes an elastic member (63) that elastically deforms due to the filling pressure of the molten resin (G) into the cavity (50) to allow the movable portion (40) to move to the second position, and elastically returns to move the movable portion (40) to the first position as the molten resin (G) shrinks after filling is complete.
[0059] In the injection molding die (10) of Feature 4, the filling pressure of the molten resin (G) when the molten resin (G) is filled into the cavity (50) causes the movable part (40) to move toward the second position and the elastic members (63, 70) to undergo elastic deformation. Then, when the molten resin (G) contracts, the movable part (40) is pushed by the elastic member (63) and moves toward the first position in a direction that reduces the volume of the cavity (50). In other words, elastic energy is stored in the elastic member (63) by the filling pressure of the molten resin (G), and this elastic energy causes the movable part (40) to move toward a direction that reduces the volume of the cavity (50), thereby suppressing a decrease in the pressure of the molten resin (G) filled into the cavity (50).
[0060] [Feature 5] The injection molding die (10) according to feature 1, comprising a stopper provided on the base portion (33) for positioning the movable portion (40) to the second position.
[0061] In the injection molding die (10) of Feature 5, the stopper allows for precise determination of the second position of the movable part (40). This suppresses variations in the amount of resin in the injection molded product (100) and stabilizes the molding quality.
[0062] [Feature 6] An injection molding die (10) according to feature 1, wherein a parting line (L) is provided between the movable part (40) located at the first position and the second mold (20), and the movable part (40) moves such that the distance between the movable part (40) and the second mold (20) at the parting line (L) changes within the range of 0 to 0.1 mm.
[0063] In the injection molding die (10) of Feature 6, since most resins used in injection molding do not easily enter gaps of 0.1 mm or less, it is not necessary to provide a special shape at the parting line (L) between the movable part (40) and the second mold to prevent resin leakage from the cavity (50), and the injection molding die (10) can be made into a simpler structure.
[0064] [Feature 7] A method for manufacturing an injection-molded product (100) using an injection molding die (10) comprising a first mold (30) and a second mold (20) that open and close with a cavity (50) between them, wherein the first mold (30) includes a base portion (33) and a movable portion (40) that is movable relative to the base portion (33), the movable portion (40) being movable between a first position when filling of molten resin (G) into the cavity (50) begins and a second position in which the volume of the cavity (50) is larger than that of the first position, and after filling the cavity (50) with molten resin (G), the movable portion (40) is moved from the second position to the first position while the base portion (33) of the first mold (30) and the second mold (20) are in a closed state, the method for manufacturing an injection-molded product (100). [Explanation of Symbols]
[0065] 10 Injection molding dies 20 Movable type 26 Runners 30 Fixed type 32 Sprue 33 Base section 35 Support recess 36 Stopper 40 Moving parts 42 Molding recess 50 Cavity 60 Hydraulic Cylinders 60R Rod 62 Wedge-shaped member 63 Elastic members 100 Injection molded products 101 Product Department 103 Design surface 110 Injection molding machine G Molten resin L parting line
Claims
1. In an injection molding die comprising a first mold and a second mold that open and close with a cavity between them, The first type includes a base portion and a movable portion that is movable relative to the base portion, The movable part is movable between a first position when the filling of molten resin into the cavity begins and a second position in which the volume of the cavity is larger than that of the first position. An injection molding die comprising a moving means for moving the movable part from a second position to a first position when the mold is closed between the base portion of the first mold and the second mold.
2. The aforementioned means of transport is Power source and The injection molding die according to claim 1, further comprising a power conversion mechanism that converts the power of the drive source into a force that moves the movable part to the first position.
3. The drive source includes a hydraulic cylinder having a rod that moves linearly in a direction intersecting the direction of movement of the movable part, The injection molding die according to claim 2, wherein the power conversion mechanism includes a wedge-shaped member connected to the rod, which moves linearly and is pressed between the base portion and the movable portion.
4. The aforementioned means of transport is The injection molding die according to claim 1, comprising an elastic member provided between the base portion and the movable portion, which elastically deforms due to the filling pressure of the molten resin into the cavity, allowing the movable portion to move to the second position, and elastically returns to move the movable portion to the first position as the molten resin shrinks after filling is complete.
5. The injection molding die according to claim 1, further comprising a stopper provided on the base portion for positioning the movable portion at the second position.
6. A parting line is provided between the movable part located at the first position and the second mold. The injection molding die according to claim 1, wherein the movable part moves such that the distance between the movable part and the second mold in the parting line changes within a range of 0 to 0.1 mm.
7. A method for manufacturing an injection molded product using an injection molding die comprising a first mold and a second mold that open and close with a cavity between them, The first type includes a base portion and a movable portion that is movable relative to the base portion, The movable part is movable between a first position when the filling of molten resin into the cavity begins and a second position in which the volume of the cavity is larger than that of the first position. A method for manufacturing an injection molded product, comprising filling the cavity with molten resin, and then moving the movable part from the second position to the first position while the mold is closed between the base portion of the first mold and the second mold.