Defect Suppression Mechanism

Abstract

An object of the present invention is to provide a technique capable of preventing a decrease in the fluidity of a resin and preventing the occurrence of molding defects such as stringing and drooling. 【Solution means】The molding defect suppression mechanism is capable of suppressing molding defects that may occur between the molten resin and the solidified resin in injection molding, and includes a first flow path and a second flow path. The first flow path allows the molten resin to pass through. The second flow path allows air to pass through without allowing the molten resin to pass through. The second flow path is continuous with a blowout port that opens toward the first flow path. From the blowout port, the air that has passed through the second flow path is blown out into the first flow path.

Description

Technical Field

[0001] The present disclosure relates to a molding defect suppression machine Structure .

Background Art

[0002] Generally, in injection molding, the molten resin injected by an injection nozzle is fed into a mold through a sprue bushing. In injection molding, molding defects may occur between the molten resin and the solidified resin. Examples of molding defects include stringing and drooling.

[0003] Stringing is that when the mold is opened, the resin that has not completely solidified extends in a thread-like manner from the tip portion of the sprue. Also, drooling is that the molten resin at the tip portion of the injection nozzle drips down from the tip portion in a drooling shape, and is also called drawing.

[0004] Regarding the sprue bushing for countermeasures against stringing, for example, there is one described in Patent Document 1. This sprue bushing includes a sprue bushing body and a bushing component. A recess is formed on the surface of the sprue bushing body on the injection port side of the molten resin. The bushing component is fitted into the recess. The bushing component further has a nozzle contact surface which is the surface where the nozzle tip contacts. An injection port which is an opening into which the molten resin is injected is formed on the nozzle contact surface. A through hole leading from the injection port to the resin flow path inside the sprue bushing body is formed in the bushing component. The bushing component further has a plurality of ribs radially extending outward from the inner peripheral surface of the through hole.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, regarding the sprue bush of Patent Document 1, the bush component has a plurality of ribs for heat dissipation. Therefore, there is a problem that the resin solidifies as it cools, and the fluidity of the resin may deteriorate.

[0007] An object of the present disclosure is to provide a technique capable of preventing a decrease in the fluidity of a resin and preventing the occurrence of molding defects such as stringing and drooling.

Means for Solving the Problems

[0008] A molding defect suppression mechanism according to an aspect of the present disclosure is a molding defect suppression mechanism capable of suppressing molding defects that may occur between molten resin and solidified resin in injection molding, and is attached to an injection molding bush in which a flow path is formed, and includes a first flow path and a second flow path. The first flow path has a downstream end continuous with the flow path of the injection molding bush Upstream end and passes through the molten resin that has entered The inner diameters are the same . The second flow path passes air without passing molten resin. The second flow path is continuous with a blowout port that opens toward the first flow path. From the blowout port, the air that has passed through the second flow path is At a predetermined pressure blown out into the first flow path. The predetermined pressure is set to a value that can blow away and cut the thread drawing generated between the molten resin and the solidified resin in the first flow path with air. Molding defects that may occur between molten resin and solidified resin are, for example, stringing and drooling, etc. 。

Effects of the Invention

[0010] According to the present disclosure, it is possible to provide a technique capable of preventing a decrease in the fluidity of a resin and preventing the occurrence of molding defects such as stringing and drooling.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Mode for Carrying Out the Invention

[0012] Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and the description will not be repeated. Also, in some of the drawings, the X direction, Y direction, and Z direction that intersect each other are shown.

[0013] Hereinafter, the term "intersect" includes that lines, planes, or lines and planes intersect each other at right angles. The term "intersect" further includes that lines, planes, or lines and planes intersect each other at a non-right angle within a minute difference range. The minute difference includes tolerances and errors.

[0014] [First Embodiment] Hereinafter, with reference to FIGS. 1 to 3, a first embodiment in which the "molding defect suppression mechanism" of the present disclosure is applied to the sprue bush 13 will be described. The sprue bush 13 is an example of the "bush for injection molding" of the present disclosure.

[0015] [Sprue Bush 13] The mold includes a sprue bush 13. Hereinafter, the term "sprue bush 13" means "sprue bush 13 attached to the mold" unless otherwise specified. Hereinafter, with reference to FIGS. 2 to 3, the sprue bush 13 will be described. Note that it should be noted that the mold is not shown.

[0016] The sprue bush 13 is made of, for example, die steel and includes a large-diameter portion 131 and a small-diameter portion 132. The large-diameter portion 131 and the small-diameter portion 132 are examples of the "body" in the present disclosure. At the center of the end face 131c on one side X1 in the X direction in the large-diameter portion 131, a concave portion 131d that is recessed toward the other side X2 in the X direction from the end face 131c is formed. The concave portion 131d forms a spherical cap shape together with the nozzle touch surface 141 described later. The axis of the spherical cap is coaxial with the central axis 115a.

[0017] The sprue bush 13 further includes a through hole 133. The through hole 133 is a hole that penetrates the sprue bush 13 in the X direction. Specifically, the through hole 133 extends from the concave portion 131d to the end face 131e on the other side X2 in the X direction. The through hole 133 is designed to be coaxial with the central axis 115a.

[0018] A high-pressure air flow path 144 is formed in the sprue bush 13. The flow path 144 is a through hole that linearly extends in the radial direction r between the outer peripheral surface 131f of the large-diameter portion 131 and the large-diameter hole 133a.

[0019] The through hole 133 has a large-diameter hole 133a and a sprue 133b. That is, a sprue 133b through which the molten resin passes is formed in the large-diameter portion 131 and the small-diameter portion 132. The sprue 133b is an example of the "flow path through which the molten resin passes" in the present disclosure.

[0020] The large-diameter hole 133a is defined by a cylindrical surface that is coaxial with the central axis 115a and larger than the diameter of the sprue 133b. The large-diameter hole 133a is formed between the end of the through hole 133 on one side X1 in the X direction and the end of the sprue 133b on one side X1 in the X direction.

[0021] The sprue 133b is designed to be coaxial with the central axis 115a. In the first embodiment, the sprue 133b has a tapered shape that is smaller in the radial direction of the central axis 115a at positions closer to the end on one side X1 in the X direction. The end of the sprue 133b on one side X1 in the X direction is continuous with the end of the large-diameter hole 133a on the other side X2 in the X direction.

[0022] The sprue bush 13 further has a member 14. The member 14 is attached to the large-diameter hole 133a of the through-hole 133. That is, the member 14 is attached to the large-diameter portion 131. Specifically, the member 14 is inserted into the large-diameter hole 133a from the outside (specifically, one side X1 in the X direction) of the large-diameter portion 131 and fixed. Hereinafter, the term "member 14" means "member 14 attached to the large-diameter hole 133a" unless otherwise specified. Further, the member 14 is the first example of the "molding defect suppression mechanism" of the present disclosure.

[0023] The member 14 is made of, for example, maraging steel. Since maraging steel has a relatively high hardness of 50 HRC, it is difficult to wear and break even when the injection nozzle 21 repeatedly contacts it.

[0024] The member 14 has a nozzle contact surface 141, a bottom surface 142, and a side surface 143.

[0025] The nozzle contact surface 141 is contacted by the tip of the injection nozzle 21. The nozzle contact surface 141 forms a spherical crown shape together with the concave portion 131d. The bottom surface 142 is located farther in the other direction X2 in the X direction than the nozzle contact surface 141 and is a surface that expands in the radial direction r (Y direction and Z direction). The bottom surface 142 has substantially the same shape as the nozzle contact surface 141 in a plan view from the X direction. The side surface 143 is a substantially cylindrical surface that connects the outer edge of the nozzle contact surface 141 and the outer edge of the bottom surface 142.

[0026] The member 14 further has a flow path 145. In the first embodiment, the flow path 145 is a flow path of molten resin having a cylindrical inner peripheral wall that also functions as a part of the sprue 133b of the sprue bush 13 through which the molten resin passes. The flow path 145 extends in the X direction and is designed to be coaxial with the central axis 115a. The X direction is an example of the "first direction" in the present disclosure. In the first embodiment, the flow path 145 has a horizontal (same diameter) shape in the radial direction of the central axis 115a and does not have a taper unlike the sprue 133b. One end X1 of the flow path 145 in the X direction serves as an injection port 145a of the molten resin, which is open in the same direction. Also, the other end X2 of the flow path 145 in the X direction (an example of the "downstream end of the first flow path" in the present disclosure) is continuous with the end of the sprue 133b in the X direction X1 (an example of the "upstream end of the flow path" in the present disclosure).

[0027] The member 14 further has at least one concave groove 146 and a plurality of through holes 147. In FIG. 2, the through holes 147 are shown by relatively thick solid lines. Also, the reference numeral "147" is attached to only one through hole.

[0028] The concave groove 146 is a groove that recesses from the side surface 143 in the centripetal direction r. The concave groove 146 is annular and extends in the circumferential direction θ over the entire area of the side surface 143. In the first embodiment, there are a plurality of concave grooves 146. The plurality of concave grooves 146 are separated from each other in the X direction. The concave groove 146 forms an annular flow path through which high-pressure air can flow together with the cylindrical surface partitioning the large-diameter hole 133a when the member 14 is attached to the large-diameter hole 133a.

[0029] The plurality of through holes 147 allow air to pass through but do not allow the molten resin to pass through. In the first embodiment, the cross-section of each through hole 147 is generally circular, for example, with an inner diameter of 20 μm or more and 50 μm or less. Note that the cross-sectional shape of each through hole 147 is not limited to a circular shape as long as the molten resin flowing through the flow path 145 cannot pass through it, and it may be a slit shape that is thin in the X direction and wide in the circumferential direction θ.

[0030] Each through-hole 147 penetrates the member 14 in the radial direction r from each concave groove 146 toward the flow path 145. Therefore, each through-hole 147 forms a blowout port 147a that is open toward the flow path 145 at the end in the centripetal direction r1. From each blowout port 147a, high-pressure air that has passed through each through-hole 147 is blown out into the flow path 145. Here, each through-hole 147 and the flow path 145 are examples of the "second flow path" and the "first flow path" of the present disclosure.

[0031] The plurality of through-holes 147 are arranged in the X direction and the circumferential direction θ. Specifically, the plurality of through-holes 147 are arranged at equal intervals in the circumferential direction θ in each concave groove 146. Also, the plurality of through-holes 147 are arranged at equal intervals in the X direction.

[0032] [Injection nozzle 21] As shown in FIG. 2, the injection nozzle 21, together with the air nozzle 22 and the control unit 24, constitutes a main part of an injection molding machine.

[0033] The tip of the injection nozzle 21 contacts the nozzle touch surface 141 of the sprue bush 13. The injection nozzle 21 injects molten resin under the control of the control unit 24 toward one end X1 side in the X direction of the flow path 145.

[0034] In the first embodiment, the air nozzle 22 blows out high-pressure air toward the flow path 144 under the control of the control unit 24.

[0035] The control unit 24 includes electronic circuits such as a microcomputer and a memory (not shown). The microcomputer controls the operations of the injection nozzle 21 and the air nozzle 22 according to a program stored in the memory.

[0036] [Function and effect of the sprue bush 13 (injection molding method)] After the molten resin in the mold has cooled and solidified, the control unit 24 starts to open the fixed-side mold and the movable-side mold. Immediately after the start of mold opening, the control unit 24 causes high-pressure air to be injected from the air nozzle 22 into the flow path 144. Thereafter, the high-pressure air flows toward the plurality of air outlets 147a through the concave groove 146 and the plurality of through holes 147. Each air outlet 147a blows the high-pressure air into the flow path 145. It is desirable that the pressure of the air is about 0.5 MPa or more.

[0037] During mold opening, there may be stringing or drooling caused by resin that has not fully solidified between the injection nozzle 21 and the sprue 133b. This stringing is cut by the high-pressure air blown into the flow path 145. Also, the drooling is cooled and solidified by the high-pressure air blown into the flow path 145. As a result, it is possible to suppress the adhesion of the stringing or drooling resin to the product or the mold. Thereby, it is possible to prevent the occurrence of molding defects due to stringing and also prevent the occurrence of molding defects due to drooling. The pressure of the air blown out from the plurality of air outlets 147a is set to a value at which such stringing can be blown away and cut by this air. Also, the blowing time and the air volume of the air blown out from the plurality of air outlets 147a are set to values at which the resin can be cooled to a hardness and viscosity at which drooling does not occur.

[0038] Also, in order to prevent the influence of stringing, it is necessary to solidify the molten resin relatively quickly. As a countermeasure, it is conceivable to lower the temperature of the injection nozzle. However, if the temperature of the injection nozzle is lowered, the fluidity of the molten resin will be affected. However, in the first embodiment, since the stringing is cut by air, there is no need to lower the temperature of the injection nozzle. Therefore, the fluidity of the molten resin does not decrease. Also, since there is no need to lower the temperature of the injection nozzle 21, cold slugs are less likely to occur at the tip of the injection nozzle 21.

[0039] Also, since the molten resin is cut by high-pressure air, it is possible to shorten the cooling process for solidifying the resin, and the time from the start of filling the molten resin by the injection molding machine to the completion of the product is shortened.

[0040] [Second Embodiment] In the first embodiment, the member 14 was attached to the sprue bush 13, but it is not limited to this, and it may be attached to the tip of the injection nozzle 21. The second embodiment is an example in which the "molding defect suppression mechanism" of the present disclosure is applied to the injection nozzle 21.

[0041] As shown in FIG. 4, in the second embodiment, a large-diameter hole corresponding to the large-diameter hole 133a formed in the sprue bush 13 of the first embodiment is formed at the tip of the injection nozzle 21, and the member 14 is attached to this large-diameter hole. Further, a high-pressure air flow path 221 is formed in the injection nozzle 21. High-pressure air from the air nozzle 22 is supplied to the flow path 221. The large-diameter hole formed at the tip of the injection nozzle 21 is partitioned by a cylindrical surface that is coaxial with the central axis 115a and larger than the diameter of the tip flow path of the injection nozzle 21.

[0042] In the injection nozzle 21 configured as described above, immediately after the start of mold opening, the control unit 24 injects high-pressure air from the air nozzle 22 into the flow path 221, so that high-pressure air blows out from each air outlet 147a of the member 14 into the flow path 145. As a result, the stringing that may occur between the injection nozzle 21 and the sprue 133b due to mold opening is cut by the high-pressure air. Further, the molten resin at the tip portion of the injection nozzle 21 is cooled and solidified by the high-pressure air. Therefore, also in the injection nozzle 21 of the second embodiment, it is possible to prevent the occurrence of molding defects due to stringing as in the first embodiment, and it is also possible to prevent the occurrence of molding defects due to drooling.

[0043] Note that the member 14, which is an example of the "molding defect suppression mechanism" of the present disclosure, is not limited to the above-described embodiments as long as it is a site where molding defects such as stringing and drooling may occur between the molten resin and the solidified resin when the mold is opened in injection molding. Although not shown, for example, it is possible to apply the member 14 to a pinpoint gate (pin gate) provided in a three-plate type mold or a hot runner nozzle (injection nozzle) provided in a hot runner system.

[0044] The embodiments of the present disclosure have been described above with reference to the drawings. However, the present disclosure is not limited to the above-described embodiments, and can be implemented in various aspects without departing from the gist thereof. Further, the plurality of components disclosed in the above embodiments can be modified as appropriate. For example, a certain component among all the components shown in one embodiment may be added to the components of another embodiment, or some of the components among all the components shown in one embodiment may be deleted from the embodiment.

[0045] In addition, the drawings schematically show each component mainly for facilitating the understanding of the present disclosure, and the thickness, length, number, interval, etc. of each illustrated component may be different from the actual ones for convenience in drawing preparation. Also, the configuration of each component shown in the above embodiments is an example and is not particularly limited, and it goes without saying that various changes can be made without substantially departing from the effects of the present disclosure.

[0046] [Appendix] Note that the present technology can also adopt the following configurations. (1) An injection molding bushing including a first flow path through which molten resin passes and a second flow path through which air passes without passing the molten resin, the second flow path being continuous with a blowout port opened toward the first flow path, and from the blowout port, the air that has passed through the second flow path is blown out into the first flow path. (2) The injection molding bushing according to (1), comprising a main body in which a sprue through which the molten resin passes is formed, and a member attached to the main body and having the first flow path, the second flow path, and the blowout port, wherein a downstream end of the first flow path is continuous with an upstream end of the sprue. (3) The injection molding bushing according to (2), wherein the member further has a nozzle touch surface with which an injection nozzle of the molten resin contacts, and an injection port formed on the nozzle touch surface and serving as an inlet for the molten resin, and the injection port is continuous with an upstream end of the first flow path. (4) The first flow path extends in a first direction, and air is blown out from the air outlet in a second direction intersecting the first direction, for the injection molding bush according to any one of (1) to (3). (5) A method of injection molding, which fills a mold with molten resin through the first flow path and solidifies it, and blows air into the first flow path through a second flow path through which air passes without passing the molten resin according to the mold opening of the mold.

[0047] 13: Sprue bush (injection molding bush) 14: Member (molding defect suppression mechanism) 21: Injection nozzle 141: Nozzle touch surface 145: Flow path (first flow path) 145a: Injection port 147: Through hole (second flow path) 147a: Air outlet

Claims

[Claim 1] A molding defect suppression mechanism capable of suppressing molding defects that may occur between molten resin and solidified resin in injection molding, comprising: It is attached to an injection molding bushing having a flow passage formed therein, a first flow path having a downstream end connected to the flow path, through which the molten resin entering from the upstream end passes, and having an inner diameter equal to that of the first flow path; a second flow path through which the molten resin does not pass but air passes, The second flow path is continuous with an outlet opening toward the first flow path, and the air that has passed through the second flow path is blown out from the outlet into the first flow path at a predetermined pressure. A molding defect suppression mechanism, in which the predetermined pressure is set to a value at which the air can blow away and cut any stringiness that occurs between the molten resin and the solidified resin in the first flow path.

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