Molding defect suppressing mechanism

Abstract

To provide a technique capable of preventing not only the lowering of the flowability of a resin but also the generation of molding inferiority such as stringing or dripping.SOLUTION: The molding defect suppression mechanism is capable of suppressing molding defects that may occur between a molten resin and a solidified resin in injection molding, and includes a first flow path and a second flow path. The molten resin passes through the first flow path. The second flow path does not allow the molten resin to pass through but allows air to pass through. The second flow path is continuous with the blow-out port opened toward the first flow path. Air that has passed through the second flow path is blown out from the blow-out port to the first flow path.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a molding defect suppression mechanism and an injection molding method. [Background technology]

[0002] In general, in injection molding, molten resin is injected from an injection nozzle and sent into a mold through a sprue bushing. In injection molding, molding defects can occur between the molten resin and the solidified resin. Examples of molding defects include stringiness and drooling.

[0003] Stringiness occurs when unsolidified resin stretches out like threads from the tip of the sprue when the mold is opened, while drooling occurs when molten resin at the tip of the injection nozzle drips like drool from the tip.

[0004] A sprue bushing with stringing prevention measures is described, for example, in Patent Document 1. This sprue bushing includes a sprue bushing body and a bushing component. The sprue bushing body has a recess formed on its surface facing the injection port for molten resin. The bushing component is fitted into the recess. The bushing component further has a nozzle contact surface that is the surface that comes into contact with the nozzle tip. The nozzle contact surface has an injection port formed therein, which is an opening through which molten resin is injected. The bushing component has a through hole formed in it that runs from the injection port to a resin flow path within the sprue bushing body. The bushing component further has a plurality of ribs extending radially outward from the inner circumferential surface of the through hole. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-154255 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the sprue bushing of Patent Document 1 has multiple ribs on the bushing part for heat dissipation, which causes the resin to solidify as it cools, potentially reducing its fluidity.

[0007] An object of the present disclosure is to provide a technology that can prevent a decrease in the fluidity of resin and prevent molding defects such as stringiness and drooling. [Means for solving the problem]

[0008] A molding defect prevention mechanism according to one embodiment of the present disclosure is a molding defect prevention mechanism capable of preventing molding defects that may occur between molten resin and solidified resin during injection molding, and includes a first flow path and a second flow path. The first flow path passes molten resin. The second flow path passes air but not molten resin. The second flow path is connected to an outlet that opens toward the first flow path. Air that has passed through the second flow path is blown out from the outlet into the first flow path. Molding defects that may occur between molten resin and solidified resin include, for example, stringiness and drooling.

[0009] In another embodiment of the injection molding method of the present disclosure, molten resin is filled into a mold through a first flow path and solidified, and in response to opening of the mold, air is blown into the first flow path through a second flow path that does not allow the molten resin to pass but allows air to pass through. [Effects of the Invention]

[0010] According to the present disclosure, it is possible to provide a technology that can prevent a decrease in the fluidity of resin and prevent molding defects such as stringiness and drooling. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 2 is a perspective view showing a sprue bushing 13 equipped with a member 14 according to the first embodiment, and an injection nozzle 21. [Figure 2] 2 is a view of a vertical cross section taken along line II-II in FIG. 1 as viewed from the other side Z2 in the Z direction. [Figure 3]2 is a cross-sectional view of the sprue bushing 13 taken along line VV in FIG. 1, viewed from one side X1 in the X direction. [Figure 4] FIG. 10 is a cross-sectional view showing an injection nozzle 21 equipped with a member 14 according to a second embodiment, and a sprue bushing 13. DETAILED DESCRIPTION OF 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 designated by the same reference numerals, and the description will not be repeated. In addition, some drawings show X, Y, and Z directions that intersect with each other.

[0013] Hereinafter, the term "intersection" includes when lines, surfaces, or a line and a surface intersect at right angles. The term "intersection" also includes when lines, surfaces, or a line and a surface intersect at non-right angles within a small difference range. The small difference includes tolerance and error.

[0014] [First embodiment] 1 to 3, a first embodiment in which the "molding defect prevention mechanism" of the present disclosure is applied to a sprue bushing 13. The sprue bushing 13 is an example of the "injection molding bushing" of the present disclosure.

[0015] [Sprue Bush 13] The mold includes a sprue bushing 13. Hereinafter, unless otherwise specified, the term "sprue bushing 13" means "sprue bushing 13 attached to the mold." The sprue bushing 13 will be described below with reference to Figures 2 and 3. Note that the mold is not shown in the figures.

[0016] The sprue bushing 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 "main body" of the present disclosure. A recess 131d is formed in the center of an end face 131c of the large diameter portion 131 on one side X1 in the X direction, recessed toward the other side X2 in the X direction from the end face 131c. The recess 131d, together with a nozzle touch surface 141 described below, forms a spherical crown shape. The axis of the spherical crown is coaxial with the central axis 115a.

[0017] The sprue bushing 13 further includes a through hole 133. The through hole 133 is a hole that penetrates the sprue bushing 13 in the X direction. Specifically, the through hole 133 extends from the recess 131d to an 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 bushing 13. The flow path 144 is a through hole that extends linearly in the radial direction r between the outer circumferential 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, the 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 a "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 has a diameter larger than that 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 tapers radially from the central axis 115a toward its 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 bushing 13 further includes 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 of the large diameter portion 131 (specifically, from the X1 side in the X direction) and fixed therein. Hereinafter, unless otherwise specified, the term "member 14" means "the member 14 attached to the large diameter hole 133a." Furthermore, the member 14 is a first example of a "molding defect prevention mechanism" of the present disclosure.

[0023] The member 14 is made of, for example, maraging steel, which has a relatively high hardness of 50 HRC, so it is resistant to wear and damage even when the injection nozzle 21 comes into contact with it repeatedly.

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

[0025] The nozzle touch surface 141 is in contact with the tip of the injection nozzle 21. The nozzle touch surface 141, together with the recess 131d, forms a spherical crown shape. The bottom surface 142 is located away from the nozzle touch surface 141 in the other X-direction, X2, and is a surface that extends in the radial direction r (Y-direction and Z-direction). When viewed from above in the X-direction, the bottom surface 142 has roughly the same shape as the nozzle touch surface 141. The side surface 143 is a roughly cylindrical surface that connects the outer edge of the nozzle touch surface 141 and the outer edge of the bottom surface 142.

[0026] The member 14 further includes a flow path 145. In the first embodiment, the flow path 145 is a flow path for molten resin having a cylindrical inner peripheral wall that also functions as part of the sprue 133b of the sprue bushing 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 a "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, unlike the sprue 133b, does not have a taper. An end X1 of the flow path 145 on one side in the X direction serves as an injection port 145a for molten resin that opens in the same direction. In addition, an end X2 of the flow path 145 on the other side in the X direction (an example of a "downstream end of a first flow path" in the present disclosure) is continuous with an end X1 of the sprue 133b on one side in the X direction (an example of an "upstream end of a flow path" in the present disclosure).

[0027] The member 14 further has at least one recessed groove 146 and a plurality of through holes 147. In Fig. 2, the through holes 147 are indicated by relatively thick solid lines. Also, only one through hole is given the reference symbol "147."

[0028] The recessed groove 146 is a groove recessed from the side surface 143 in the centripetal direction r. The recessed 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 multiple recessed grooves 146. The multiple recessed grooves 146 are spaced apart from each other in the X direction. When the member 14 is attached to the large diameter hole 133a, the recessed groove 146, together with the cylindrical surface that defines the large diameter hole 133a, forms an annular flow path through which high-pressure air can flow.

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

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

[0031] The multiple through holes 147 are arranged in the X direction and the circumferential direction θ. Specifically, the multiple through holes 147 are aligned at equal intervals in the circumferential direction θ in each recessed groove 146. The multiple through holes 147 are also aligned 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 the main part of the injection molding machine.

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

[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] [Effects of sprue bushing 13 (injection molding method)] After the molten resin in the molds has cooled and solidified, the control unit 24 starts the mold opening between the fixed mold and the movable mold. Immediately after the mold opening begins, the control unit 24 injects high-pressure air from the air nozzle 22 into the flow path 144. The high-pressure air then flows through the recessed groove 146 and the plurality of through-holes 147 toward the plurality of air outlets 147a. Each air outlet 147a blows high-pressure air into the flow path 145. The air pressure is preferably about 0.5 MPa or higher.

[0037] When the mold is opened, stringiness or drooling due to incompletely solidified resin may occur between the injection nozzle 21 and the sprue 133b. This stringiness is cut by the high-pressure air blown into the flow path 145. The drooling is also cooled and solidified by the high-pressure air blown into the flow path 145. As a result, the stringiness or drooling resin is prevented from adhering to the product or mold. This makes it possible to prevent molding defects due to stringiness as well as molding defects due to drooling. The pressure of the air blown out from the multiple air outlets 147a is set to a value that allows the air to blow away and cut off such stringiness. The blowing time and volume of the air blown out from the multiple air outlets 147a are set to values ​​that allow the resin to cool to a hardness and viscosity that prevents drooling.

[0038] Furthermore, to prevent the effects of stringing, it is necessary to solidify the molten resin relatively quickly. One possible solution to this problem is to lower the temperature of the injection nozzle. However, lowering the temperature of the injection nozzle affects the fluidity of the molten resin. However, in the first embodiment, the stringing is cut off by air, so there is no need to lower the temperature of the injection nozzle. Therefore, the fluidity of the molten resin does not decrease. Furthermore, because 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] In addition, because the molten resin is cut by high-pressure air, the cooling process for solidifying the resin can be shortened, reducing the time from when the injection molding machine starts filling the molten resin to when the product is completed.

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

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

[0042] In the injection nozzle 21 configured in this manner, immediately after the mold opening process begins, the control unit 24 injects high-pressure air from the air nozzle 22 into the flow path 221, causing high-pressure air to be blown into the flow path 145 from each air outlet 147a of the member 14. This causes the high-pressure air to cut any stringing that may occur between the injection nozzle 21 and the sprue 133b during mold opening. In addition, the molten resin at the tip of the injection nozzle 21 is cooled and solidified by the high-pressure air. Therefore, the injection nozzle 21 of the second embodiment can prevent molding defects due to stringing, as in the first embodiment, and can also prevent molding defects due to drooling.

[0043] Note that member 14, which is an example of the "molding defect prevention mechanism" of the present disclosure, is not limited to the above-described embodiment, as long as it is a portion where molding defects such as stringiness or drooling may occur between the molten resin and the solidified resin when the mold is opened during injection molding. Although not shown, member 14 can also be applied to, for example, a pinpoint gate (pin gate) provided in a three-plate 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 embodiments and can be implemented in various forms without departing from the spirit and scope of the present disclosure. Furthermore, the components disclosed in the above embodiments can be modified as appropriate. For example, some of the components shown in one embodiment may be added to the components of another embodiment, or some of the components shown in one embodiment may be deleted from the embodiment.

[0045] Furthermore, the drawings mainly show each component in a schematic manner to facilitate understanding of the present disclosure, and the thickness, length, number, spacing, etc. of each component shown in the drawings may differ from the actual configuration due to the convenience of creating the drawings. Furthermore, the configuration of each component shown in the above embodiment is an example and is not particularly limited, and it goes without saying that various modifications are possible within a scope that does not substantially deviate from the effects of the present disclosure.

[0046] [Note] The present technology can also employ the following configuration. (1) An injection molding bushing having a first flow path through which molten resin passes and a second flow path through which air passes but which does not pass the molten resin, the second flow path being continuous with an outlet opening toward the first flow path, and the air that has passed through the second flow path being blown out from the outlet into the first flow path. (2) An injection molding bushing as described in (1), comprising a main body having a sprue through which the molten resin passes, and a member attached to the main body and having the first flow path, the second flow path, and the blow-out outlet, wherein the downstream end of the first flow path is continuous with the upstream end of the sprue. (3) The injection molding bushing described in (2) above, wherein the member further has a nozzle touch surface with which an injection nozzle for the molten resin comes into contact, and an injection inlet for the molten resin formed on the nozzle touch surface, the injection inlet being continuous with the upstream end of the first flow path. (4) The bushing for injection molding according to any one of (1) to (3), wherein 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. (5) An injection molding method, comprising filling a mold with molten resin through a first flow path and solidifying it, and, upon opening the mold, blowing air into the first flow path through a second flow path that does not allow the molten resin to pass but allows air to pass through.

[0047] 13: Sprue bushing (bush for injection molding) 14: Parts (mechanism for suppressing molding defects) 21: Injection nozzle 141: Nozzle touch surface 145: Flow path (first flow path) 145a: Inlet 147: Through hole (second flow path) 147a: Air outlet

Claims

1. A molding defect prevention mechanism capable of suppressing molding defects that may occur between molten resin and solidified resin in injection molding, A molding defect prevention mechanism comprising a first flow path through which the molten resin passes and a second flow path through which air passes but which does not pass the molten resin, the second flow path being continuous with an outlet that opens toward the first flow path, and the air that has passed through the second flow path being blown out from the outlet into the first flow path.

2. attached to an injection molding bushing having a flow path through which the molten resin passes; The molding defect suppression mechanism according to claim 1 , wherein a downstream end of the first flow path is continuous with the flow path.

3. 3. The molding defect prevention mechanism according to claim 2, further comprising: a nozzle touch surface with which an injection nozzle for the molten resin comes into contact; and an injection inlet for the molten resin formed on the nozzle touch surface, the injection inlet being continuous with an upstream end of the first flow path.

4. 4. The molding defect suppression mechanism according to claim 1, wherein the first flow path extends in a first direction, and the air is blown out from the air outlet in a second direction intersecting the first direction.

5. An injection molding method comprising filling a mold with molten resin through a first flow path, and, in response to opening of the mold, blowing air into the first flow path through a second flow path that does not allow the molten resin to pass but allows air to pass.

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