Injection molding device, control device, control method of injection molding device, and manufacturing method of resin molding

Abstract

To effectively suppress formation of poor appearance in a valve gate type injection molding device.SOLUTION: An injection molding device comprises: a metal mold main body with a mold cavity formed by mold-closing a first mold and a second mold; a gate device provided with an injection hole for injecting a molten resin; a valve pin with a tip displaceable from a clogging position for clogging the injection hole and an injection position for opening the injection hole; an actuator for displacing the valve pin; and a control device for controlling the actuator. In the valve pin, a tip face positioned on the mold cavity side is displaceable from the clogging position to an advance position advanced further to the mold cavity side. The control device controls the actuator in a manner that, after displacing the valve pin to the injection position, and at a timing after injecting the molten resin, the valve pin is displaced to the clogging position, then displacement of the valve pin to the advance position is performed.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to an injection molding apparatus that injects molten resin into a cavity of a mold body by closing and opening an injection hole with a valve pin. [Background technology]

[0002] Conventionally, when manufacturing plastic molded products, injection molding machines using the so-called valve gate method have been used, in which molten resin is injected into the cavity of the mold body by closing and opening the injection hole with a valve pin. The valve gate method is an excellent method in that it allows the injection hole to be positioned to a certain extent freely depending on the required quality of the product (strength, density, etc.).

[0003] In this type of injection molding device, molten resin is injected from the injection hole by displacing the valve pin between an open position that opens the injection hole and a closed position that closes the injection hole (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 77760 of 1999 Summary of the Invention [Problem to be solved by the invention]

[0005] However, a configuration like the injection molding device described above, which simply displaces the valve pin between an open position and a closed position, is prone to causing appearance defects such as sink marks on the surface of the mold that sandwiches the valve pin in the resin molded product, and is therefore not suitable for molding products where this surface is a decorative surface.

[0006] One way to prevent such cosmetic defects is to use a so-called side-gate injection molding machine, but the side-gate method places significant restrictions on the position of the injection hole, which often results in the product not meeting the required quality, making it unrealistic to adopt.

[0007] The present invention has been made to solve such problems, and aims to provide a technique for effectively suppressing the occurrence of appearance defects in a valve gate type injection molding apparatus. [Means for solving the problem]

[0008] The injection molding apparatus according to the present disclosure comprises: a mold body in which a cavity is formed by closing a first mold and a second mold; a gate device provided in the first mold and having an injection hole through which molten resin is injected into the cavity; a valve pin that is displaceable within the gate device to a blocking position where it moves toward the cavity and its tip closes the injection hole, and to an injection position where it moves away from the cavity and its tip opens the injection hole so that the molten resin is injected through the injection hole; an actuator that displaces the valve pin; and a control device that controls the actuator, wherein the valve pin is also displaceable to an advanced position in which its tip face located on the cavity side advances further from the blocking position toward the cavity side, and the control device controls the actuator to displace the valve pin to the injection position, and then to the blocking position after the molten resin has been injected, and then to displace the valve pin to the advanced position. [Effects of the Invention]

[0009] According to the present disclosure, by advancing the valve pin toward the cavity while the molten resin injected into the cavity hardens into the molded resin product, the area of ​​the molded resin product corresponding to the valve pin is pressed. As a result, even if the area of ​​the molded resin product located on the second mold side across the valve pin recedes toward the valve pin, potentially causing a sink mark, the advancement of the valve pin prevents this area from receding, thereby preventing the occurrence of a sink mark. In this way, the injection molding apparatus of the present disclosure can effectively prevent the occurrence of poor appearance in the molded resin product. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram illustrating a configuration of an injection molding apparatus according to an embodiment of the present disclosure. [Figure 2] FIG. 1 is a cross-sectional view of a main portion of an injection molding apparatus according to an embodiment of the present disclosure. [Figure 3] Flowchart illustrating a displacement control process according to an embodiment of the present disclosure. [Figure 4] 1 illustrates the operation of an injection molding apparatus according to one embodiment of the present disclosure. [Figure 5] FIG. 1 is a cross-sectional view of a main portion of an injection molding apparatus according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. (1) Overall structure As shown in FIGS. 1 and 2, the injection molding apparatus 1 includes a mold body 10, a gate device 20, a valve pin 30, an actuator 40, a control device 50, and a surrounding wall 60.

[0012] The mold body 10 has a cavity 100 formed by closing a first mold 11 and a second mold 13. The mold body 10 is composed of a first mold 11 and a second mold 13 that are divided in a predetermined direction (vertical direction in this embodiment), and the second mold 13 is displaceable along the dividing direction relative to the first mold 11. When the second mold 13 is displaced until it is closed with the first mold 11, the cavity 100 is formed as an internal space sandwiched between both molds.

[0013] 2, the gate device 20 is provided in the first mold 11, and has an injection hole 21 formed therein for injecting molten resin material (hereinafter referred to as "molten resin") toward the cavity 100. The gate device 20 is a cylindrical member that is embedded in the first mold 11 and extends until it reaches the cavity 100, and the injection hole 21 is formed at the end (the lower end in FIG. 2) on the side that reaches the cavity 100.

[0014] The valve pin 30 is housed inside the gate device 20 and is a pin that extends along the dividing direction of the mold body 10, and is provided so as to be movable within this gate device 20. This valve pin 30 is displaceable to a blocking position where it moves toward the cavity 100 and its tip closes the injection hole 21, an injection position where it moves toward the opposite side of the cavity 100 and its tip opens the injection hole 21, thereby injecting molten resin from the injection hole 21, and an advanced position where its tip face advances further from the blocking position toward the cavity 100.

[0015] In this embodiment, the position where the tip surface of the valve pin 30 advances a predetermined amount from the injection hole 21 toward the cavity 100 is the "advanced position," and the position where the tip surface of the valve pin 30 coincides with the boundary surface between the injection hole 21 and the cavity 100 is the "blocked position."

[0016] The actuator 40 is composed of a displacement mechanism for displacing the valve pin 30 and a motor for driving this displacement mechanism.

[0017] The control device 50 is a computer that controls the operation of the actuator 40 to displace the valve pin 30 .

[0018] The surrounding wall 60 is formed at the tip of the gate device 20 on the cavity 100 side in a position that surrounds the injection hole 21, and is formed with a height that can surround at least the tip face of the valve pin 30 in the advanced position. In this embodiment, the surrounding wall 60, which has a diameter larger than that of the injection hole 21, is provided as part of the gate device 20 at the tip of the gate device 20 on the cavity 100 side.

[0019] In this embodiment, surrounding wall 60 has the greatest height at the inner circumferential portion surrounding injection hole 21, and is formed so that the height of the wall decreases with increasing distance from injection hole 21. The thickness of surrounding wall 60 from the inner circumferential portion to the outer circumferential portion is set to a value that is sufficiently large relative to the height of the wall (specifically, the thickness is 50 to 100 times the height of the wall).

[0020] In the injection molding apparatus 1 configured in this manner, the valve pin 30 is displaced to an injection position where the molten resin is injected by opening the injection hole 21, displaced to a blocking position where the injection hole 21 is blocked after the molten resin has been injected, and after a predetermined cooling period has elapsed, displaced to an advanced position where the tip surface has advanced further from the blocked position toward the cavity 100, thereby producing a resin molded product.

[0021] (2) Processing procedure by the control device The procedure of the "displacement control process" executed by the control device 50 using a program stored in the built-in memory 51 will be described below with reference to Fig. 3. This displacement control process is started when a start command is received from an interface (operation device or communication device) not shown.

[0022] When this displacement control process is started, first, it is checked whether it is time to displace the valve pin 30 to the injection position (s110), and the process waits until it is determined that it is time to displace the valve pin 30 to the injection position (s110: NO). Here, it is determined that it is "time to displace the valve pin 30 to the injection position" when a sensor (not shown) detects that the valve pin 30 is in the closed position, that the first die 11 and the second die 13 have been closed, and that the gate device 20 has been filled with molten resin.

[0023] If it is determined that it is time to move the valve pin 30 to the injection position (s110: YES), the valve pin 30 is moved to the injection position (s120). A command to move the valve pin 30 to the injection position is issued, and the actuator 40, upon receiving this command, moves the valve pin 30 to the injection position. This starts the injection of the molten resin 200 from the injection hole 21 into the cavity 100 (see FIG. 4(a)).

[0024] Next, it is checked whether it is time to displace the valve pin 30 to the closing position (s130), and the process waits until it is determined that it is time to displace the valve pin 30 to the closing position (s130: NO). Here, after s130, if the time required for a specified amount of molten resin to be injected from the injection hole 21 has elapsed, it is determined that it is "time to displace the valve pin 30 to the closing position."

[0025] If it is determined that it is time to displace the valve pin 30 to the closed position (s130: YES), the valve pin 30 is displaced to the closed position (s140). Here, a command to displace the valve pin 30 to the closed position is issued, and the actuator 40, upon receiving this command, displaces the valve pin 30 to the closed position. This completes the injection of the molten resin 200 from the injection hole 21 into the cavity 100 (see FIG. 4(b)).

[0026] Next, it is checked whether it is time to displace the valve pin 30 to the advanced position (s150), and the process waits until it is determined that it is time to displace the valve pin 30 to the advanced position (s150: NO). Here, it is determined that it is "time to displace the valve pin 30 to the advanced position" when a certain time has passed before the time required for the molten resin injected into the cavity 100 to harden (cooling time) has passed.

[0027] If it is determined that it is time to move the valve pin 30 to the advanced position (s150: YES), the valve pin 30 is advanced (s160). In this advancement operation, the valve pin 30 is first displaced from the closed position to the advanced position, and then from the advanced position to the closed position.

[0028] Specifically, first, a command is given to displace the valve pin 30 to the advanced position, and the actuator 40, upon receiving this command, displaces the valve pin 30 to the advanced position (see FIG. 4(c)). Here, a command is given to displace the valve pin 30 in multiple stages until it reaches the advanced position, and the actuator 40, upon receiving this command, gradually displaces the valve pin 30 to the advanced position in multiple stages. After that, after a predetermined waiting time has elapsed, a command is given to displace the valve pin 30 to the closed position, and the actuator 40, upon receiving this command, displaces the valve pin 30 to the closed position (FIG. 4(c) ⇒ (b)).

[0029] (3) Variations Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above embodiments, and various modifications are possible within the scope of the gist of the invention. In particular, the multiple modifications described in this specification can be arbitrarily combined as necessary.

[0030] For example, in this embodiment, the "blocking position" is defined as the position where the tip surface of the valve pin 30 located on the cavity 100 side coincides with the boundary surface between the injection hole 21 and the cavity 100. However, the "blocking position" only needs to be able to block the injection hole 21, and the tip surface of the valve pin 30 may be a position a predetermined distance away from the boundary surface between the injection hole 21 and the cavity 100 toward the first mold 11. In this case, the "advance position" may be a position where the tip surface of the valve pin 30 does not advance from the injection hole 21 toward the cavity 100, as long as the tip surface advances further toward the cavity 100 from the blocking position.

[0031] In the above embodiment, in step s160 of the displacement control process, the valve pin 30 is displaced from the closed position to the advanced position, and then the "advance operation" of displacing the valve pin 30 from the advanced position to the closed position is performed only once. However, this "advance operation" may be performed multiple times.

[0032] In the above embodiment, a configuration has been exemplified in which surrounding wall 60 having a diameter larger than that of injection hole 21 is formed at the tip of gate device 20. However, surrounding wall 60 may be formed to surround injection hole 21 with the same inner diameter as injection hole 21.

[0033] (4) Action and effect In the above embodiment, by advancing the valve pin 30 toward the cavity 100 while the molten resin injected into the cavity 100 hardens into a resin molded product, the region of the resin molded product corresponding to the valve pin 30 is pressed. As a result, even if a region of the molten resin that will become the resin molded product, located on the second mold 13 side across the valve pin 30, recedes toward the valve pin 30 as shown in Fig. 5, and a sink mark 210 may occur, the receding of this region is suppressed by the advancement of the valve pin 30, thereby preventing the occurrence of the sink mark 210. In this way, the injection molding apparatus 1 of the above embodiment can effectively prevent the occurrence of defective appearance in the resin molded product.

[0034] Furthermore, in the above embodiment, the displacement control process controls the displacement of the valve pin 30 in multiple stages until it reaches the advanced position, so that the area of ​​the resin molded product corresponding to the valve pin 30 can be gradually pressed.

[0035] Furthermore, in the above embodiment, the valve pin 30 is configured so that its tip surface can be displaced to an advanced position by a predetermined amount from the injection hole 21 toward the cavity 100, and the tip side is displaced until it penetrates into the resin molded product, thereby making it possible to suppress the occurrence of sink mark 210 equivalent to the volume of penetration into the resin molded product.

[0036] Furthermore, in the above embodiment, the surrounding wall 60 is provided so as to surround the injection hole 21, and therefore, as shown in FIG. 5, the pressing force exerted when the valve pin 30 is displaced to the advanced position can be effectively transmitted to the resin molded product. [Explanation of symbols]

[0037] 1: injection molding device, 10: mold body, 11: first mold, 13: second mold, 20: gate device, 21: injection hole, 30: valve pin, 40: actuator, 50: control device, 51: built-in memory, 60: surrounding wall, 100: cavity, 210: sink mark.

Claims

1. a mold body in which a cavity is formed by closing the first mold and the second mold; a gate device provided in the first mold and having an injection hole formed therein for injecting molten resin into the cavity; a valve pin that is displaceable within the gate device between a blocking position where the valve pin moves toward the cavity side and the tip of the valve pin blocks the injection hole, and an injection position where the valve pin moves toward the opposite side from the cavity and the tip of the valve pin opens the injection hole, thereby injecting the molten resin from the injection hole; an actuator that displaces the valve pin; a control device for controlling the actuator, the valve pin is also displaceable to an advanced position where a tip end surface located on the cavity side is further advanced from the closed position toward the cavity side, the control device controls the actuator so that, after displacing the valve pin to the injection position, the valve pin is displaced to the closing position at a timing after the molten resin is injected, and then the valve pin is displaced to the advanced position. Injection molding equipment.

2. the control device controls the actuator so that the valve pin is displaced in multiple stages until it reaches the advanced position.

2. The injection molding apparatus of claim 1.

3. the advanced position is a position where the tip end surface of the valve pin is advanced from the injection hole toward the cavity by a predetermined amount.

3. The injection molding apparatus according to claim 1 or 2.

4. the control device displaces the valve pin to the injection position, and then displaces the valve pin to the closing position at a timing after the molten resin is injected, and then controls the actuator to displace the valve pin from the closing position to the advanced position and from the advanced position to the closing position.

4. An injection molding apparatus according to any one of claims 1 to 3.

5. a surrounding wall formed to surround the injection hole, 5. An injection molding apparatus according to any one of claims 1 to 4.

6. the valve pin is displaceable to the advanced position where a tip end surface thereof advances from the injection hole toward the cavity by a predetermined amount, the surrounding wall is formed to a height sufficient to surround at least the tip end surface of the valve pin in the advanced position.

6. The injection molding apparatus of claim 5.

7. a mold body in which a cavity is formed by closing the first mold and the second mold; a gate device provided in the first mold and having an injection hole formed therein for injecting molten resin into the cavity; a valve pin that is displaceable within the gate device to a blocking position where it moves toward the cavity side and its tip closes the injection hole, an injection position where it moves toward the opposite side from the cavity and its tip opens the injection hole, thereby injecting the molten resin from the injection hole, and an advanced position where its tip face located on the cavity side further advances toward the cavity side from the blocking position; an actuator that displaces the valve pin; A control device for controlling the operation of an injection molding apparatus comprising: controlling the actuator so that, after the valve pin has been displaced to the injection position, the valve pin is displaced to the closing position at a timing after the molten resin has been injected, and then the valve pin is displaced to the advanced position; Control device.

8. a mold body in which a cavity is formed by closing the first mold and the second mold; a gate device provided in the first mold and having an injection hole formed therein for injecting molten resin into the cavity; a valve pin that is displaceable within the gate device to a blocking position where it moves toward the cavity side and its tip closes the injection hole, an injection position where it moves toward the opposite side from the cavity and its tip opens the injection hole, thereby injecting the molten resin from the injection hole, and an advanced position where its tip face located on the cavity side further advances toward the cavity side from the blocking position; an actuator that displaces the valve pin; A control method for controlling the operation of an injection molding apparatus comprising: controlling the actuator so that, after the valve pin has been displaced to the injection position, the valve pin is displaced to the closing position at a timing after the molten resin has been injected, and then the valve pin is displaced to the advanced position; A method for controlling an injection molding device.

9. A program for causing a computer to function as the control device according to any one of claims 1 to 7.

10. A manufacturing method for manufacturing a resin molded product using an injection molding apparatus in which molten resin is injected into a cavity of a mold body by closing and opening an injection hole with a valve pin, comprising: the valve pin is displaced to an injection position where the molten resin is injected by opening the injection hole, displaced to a closing position where the injection hole is closed at a timing after the molten resin is injected, and displaced to an advanced position where the tip end face is further advanced from the closing position toward the cavity after a predetermined cooling period has elapsed; A method for manufacturing resin molded products.

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