JP7229605B1 - Injection mold, resin molded product and resin molding method - Google Patents

Abstract

A mold for injection molding is provided, which is capable of molding even a thin-walled molded product having convex portions while suppressing the manufacturing cost of the mold and suppressing deterioration in the quality of the thin-walled molded product.
Kind Code: A1 An injection mold 10 molds a resin molded product having a convex portion and a flat portion by injecting molten resin into a cavity 13 formed between a core mold 12 and a cavity mold 14. A mold for injection molding, wherein the cavity 13 includes a convex space portion 13A for molding a convex portion, a planar space portion 13B for forming a planar portion around the convex portion, the convex space portion 13A and the planar space portion. 13B, a band-shaped induction band space 13C having a space portion thicker than the convex space 13A and the plane space 13B is provided, and molten resin is injected into the induction band space 13C. It has a gate 16 and a residual gas discharge part 18 formed in the core mold 12 or the cavity mold 14 for discharging residual gas remaining from the top of the convex space 13A to the top.
[Selection drawing] Fig. 1

Description

TECHNICAL FIELD The present invention relates to an injection mold, a resin molded product, and a resin molding method.

2. Description of the Related Art Conventionally, a vacuum forming technique is known as a technique for molding various relatively thin resin molded articles (hereinafter also simply referred to as "molded articles") such as egg cartons. Since the vacuum forming technique uses a resin material that has been processed into a sheet having a predetermined thickness in advance, it is relatively easy to form a thin molded product.

However, the vacuum forming technique requires the resin material to be processed into a sheet in advance, and therefore has the problem of being limited to resin materials that can be obtained in the state of being processed into a sheet. In addition, since the sheet-shaped resin material is stretched over a frame, heated, and vacuum-sucked to adhere to the mold for molding, the bent parts of the molded product are easily stretched, becoming thin and fragile, and it is difficult to maintain the dimensional accuracy of the thickness. This is difficult, and there are problems such as not being able to make the thickness very thin for a molded article having a complicated shape with many irregularities.

Injection molding technology is also well known as a technology for molding resin molded products. Injection molding technology melts a resin material and forms a mold inside an injection mold (hereinafter simply referred to as a "mold") that is processed to provide a molten resin flow path in a metal block. Space (hereinafter also referred to as "cavity") is filled with molten resin, cooled and solidified, and then the separable mold members constituting the mold are separated to open the molding space (hereinafter referred to as "cavity"). , also called “mold opening”), is a technique of molding a molded product by taking out the molded product. For example, Patent Literature 1 discloses a mold in which a gate (pinpoint gate) that is an entrance from a runner to a molding space is formed.

Compared to vacuum molding technology, injection molding technology does not stretch at bends, it molds according to the shape of the mold cavity, has high dimensional accuracy, and may lose strength at bends. has the advantage of not In addition, unlike vacuum molding technology, injection molding technology can be used with many types of resin materials, and even used resin materials such as polypropylene (PP) can be recovered, remelted, and reused. It also has the advantage of being able to suppress the load.

However, with injection molding technology, it is necessary to pour molten resin into every corner of the cavity to fill it. Molded products with a large surface area and complex shapes with a complex mixture of flat and uneven parts have many factors that hinder the smooth flow of the molten resin. There is a problem that it is relatively difficult to fill the resin to the end of the cavity without gaps.

Further, in Patent Document 2, the present inventor also made a proposal leading to the solution of the above-mentioned problems in the injection molding technology. Patent Literature 2 discloses a complex-shaped cushioning body in which flat portions and convex portions are mixed, which is molded using a mold.

According to the shock absorber technique of Patent Document 2, it is shown that a relatively thin molded product having a thickness of about 0.4 mm can be molded. In the mold used for the shock absorber of Patent Document 2, an induction band extending from the gate (a rib-like portion in the molded product) surrounds the cavity portion corresponding to the convex portion of the shock absorber, and the induction band further It is formed so as to branch and crawl up the portion corresponding to the convex portion. According to the proposal of Patent Document 2, compared to the case without such an induction band, the flow of the molten resin in the portion corresponding to the convex portion of the buffer becomes smoother, and accordingly the number of gates can be reduced, and the convex portion It is said to have the effect of suppressing molding defects that occur.

Japanese Utility Model Laid-Open No. 6-5929 JP 2020-097433 A

However, through subsequent prototype experiments and research by the present inventor, the effect of suppressing molding defects that occur in the convex portions as described above cannot be obtained for a specific shape such as the buffer structure of Patent Document 2. Although it has been confirmed, it is not easy to determine the optimum positional relationship between the part corresponding to the convex part in the cavity and the guide band for a general molded product shape with a thin wall and a complicated convex part. It became clear.

Patent Document 2 does not disclose any method for reducing the flow path resistance of the curved portion of the cavity at the boundary between the flat portion and the convex portion of the molded product having the convex portion. Even with the use of , trial and error are required to determine an appropriate mold shape including the placement of the guide band, and the problem of high cost still remains.

The present invention has been made with a focus on the above-mentioned problems, and even if the molded product is relatively thin and large in size or has a complex shape in which flat parts and uneven parts are mixed in a complicated manner, The object is to provide a mold that simplifies the number and arrangement of gates, suppresses the production cost of the mold, and suppresses deterioration of the quality of the molded product, and a molded product molded using such a mold. do.

A mold for injection molding according to a first aspect of the present invention has a core mold and a cavity mold, the core mold and the cavity mold are overlapped, and a mold is formed between the core mold and the cavity mold. A mold for injection molding that molds a resin molded product having a convex portion and a flat portion by injecting a molten resin into a cavity, wherein the cavity includes a convex space portion for molding the convex portion; A planar space portion forming the planar portion around the convex portion, and at least one of the convex portion space portion and the planar space portion, the wall thickness of which is thicker than that of the convex portion space portion and the planar space portion. a gate for injecting a molten resin into the induction band space; and a top portion of the convex space formed in at least one of the core mold and the cavity mold and a residual gas discharge part for discharging residual gas remaining in the top part from.

According to the above configuration, the molten resin injected into the cavity from the gate has a flow path thicker than that of the convex space and the plane space, and therefore the flow path resistance is lower than that of the convex space and the plane space. Through the induction zone space having a part, the end of the induction zone space near the flat space and the convex space at a point away from the gate (that is, after that, the flow path resistance of the flow path is high place) quickly. As a result, the molten resin pressure inside the induction band is accumulated, and the molten resin spreads from there to the surrounding flat space and convex space, so that the quality is higher than that of a mold without an induction band space. Thin-walled molded products can be molded.

Further, according to the above configuration, the residual gas discharge portion is positioned at the top of the convex space portion. Molten resin flows into this convex space from around the base of the convex due to the effect of the induction band placed in the planar space, so part of the residual gas inside the cavity is removed by the flow pressure of the molten resin. It is easy to temporarily concentrate near the top of this convex space. Normally, the residual gas in the cavity is discharged from the gap in the parting surface at the end of the molten resin flow path. Since the residual gas passes through the part and is discharged to the outside of the mold, the residual gas is discharged more smoothly than in the case where the residual gas discharge part is not provided. The residual gas discharge part has such a small gap that the gas passes through but the molten resin does not pass through. As a result, it is possible to suppress deterioration in quality due to gas burns, short circuits, warping, etc. of molded products caused by residual gas.

In addition, according to the above configuration, the residual gas is appropriately discharged to the outside of the mold by the residual gas discharge part, so that the residual gas concentrated near the top of the convex space is excessively compressed and the pressure is increased. Suppressed. As a result, it is possible to prevent distortion caused by excessive local pressure from remaining in the molded product, and also to prevent residual gas from exceeding the ignition point of the molten resin due to adiabatic compression and scorching the surface of the resin. Furthermore, it is possible to reduce the filling pressure required to fill the cavity with the molten resin while discharging the residual gas to the outside of the mold. In addition, as a result of lightening the pressure load on the injection molding machine, it becomes possible to use a small injection molding machine, which contributes to cost reduction.

Further, according to the above configuration, it is not necessary to provide the gates at the top positions of the convex space portions to prevent residual gas from remaining in the convex space portions, and the gates are not necessary to prevent the residual gas from stagnation in the convex space portions. A number smaller than the number of parts can be appropriately arranged. For example, in the cavity, the flow path formed by the induction zone space extending from one gate is branched into a plurality of flow paths similarly formed by the induction zone space, and the branched flow path is formed on the downstream side to form a plurality of protrusions. A space part can be arranged.

For this reason, compared to the conventional method in which a gate is provided at the top of each projection space, even when a plurality of projections are provided on the molded product, a plurality of gates are provided in the mold according to the number of projections. No need to place. Therefore, the configuration of the runners for supplying the molten resin to the gates in a well-balanced manner is relatively simple, and the cost of designing and manufacturing the mold can be reduced.

In the above first aspect, the residual gas discharge part includes a gas vent hole provided in at least one of the core mold and the cavity mold and reaching the top of the convex space from the outer surface of the mold, and the gas vent and a plug member removably inserted into the hole, wherein the entire outer peripheral surface of at least a portion of the plug member that is in contact with the top of the convex space is in close contact with the entire inner peripheral surface of the gas vent hole. Between the outer peripheral surface of the rod-shaped member and the inner peripheral surface of the gas vent hole in the tight contact portion, a gas flow path through which the molten resin cannot pass but the residual gas can pass may be formed.

According to the above configuration, the inner surface of the gas vent hole and the outer surface of the plug member are substantially in close contact with each other at least at the tip portion contacting the top of the convex space, thereby preventing the molten resin from leaking out from the gas vent hole. . In addition, since the contact surface has a small gap through which the passage of the molten resin is difficult and the passage of the residual gas is possible, the residual gas concentrated at the top of the convex space part is released from this gap. Ejected.

In addition to the gaps resulting from the minute irregularities present on the metal processing surface, the gaps in the contact surface are such that the inner surface of the gas vent hole and/or the outer surface of the plug member make it difficult for molten resin to pass through and residual gas to escape. Gas passages that can pass through can be added by machining. Such additional gas flow paths may be formed, for example, by roughening the wall surface by sandblasting or by cutting, etching, or the like.

By preparing various types of plug members that change the flow path resistance of the residual gas discharge path by adding such a gas flow path, it is possible to appropriately replace the plug member according to the type of resin and the amount of residual gas. , appropriate degassing can be performed, and as a result, the number of prototype designs for performing appropriate degassing can be reduced, and the mold cost can be reduced. In addition, the residual gas discharge path using the contact surfaces of such mold parts becomes tar-like and adheres to the volatile components of the molten resin, and it gradually becomes dirty and clogged, so it needs to be cleaned from time to time. According to the above construction, since the plug member is detachable, it is easy to remove the plug member at any time to clean the gas flow path.

In the present invention, the "gas flow path through which the molten resin cannot pass but the residual gas can pass" basically means that the molecular size of the molten resin is larger than that of the residual gas and the string-like polymer of the molten resin is entwined and integrated. It means a gas channel having an opening diameter smaller than the size of the polymerized molecular group, provided that the size of the molecular group varies depending on the type of resin, and even if it is the same resin, the degree of polymerization of the polymer (molecular weight) varies, and the degree of entanglement of the string-like polymer exhibits various irregular shapes. Also included is a gas flow path with an opening diameter that does not cause defects in the molded product.

In the above-described first aspect, the outlet of the gas vent hole communicates with a flow path connected to an air injection device, and the air injection device causes the convex portion of the resin molded product to move from the gas vent hole. Air may be injected to the outer surface, and the resin molded product may be released from at least one of the core mold and the cavity mold by the pressure of the air.

According to the above configuration, after the mold opening process for separating the core mold and the cavity mold is completed, the gas vent hole can also be used as an air injection hole for pushing out the molded product from the mold by the wind pressure of air and releasing the mold. Therefore, the number of air injection holes can be reduced compared to the case where all the air injection holes are provided separately. can. Further, for example, when the mold is released using an ejector pin, the tip of the ejector pin may give a mechanical impact to the molded product and damage it. will not be damaged by mechanical shock.

In the first aspect, the outlet of the gas vent hole communicates with a flow path connected to a vacuum device, and the vacuum device sucks residual gas discharged from the gas vent hole, and the convex portion Residual gas evacuation from the top of the void may be facilitated.

According to the above configuration, in the step of injecting the molten resin into the cavity, when the residual gas concentrated in the convex space is discharged through the gas vent hole, the residual gas is discharged by the suction force of the vacuum. The degassing hole can also be used as the vacuum suction hole for urging. Therefore, compared to the case where the holes are not used as vacuum suction holes, the discharge capacity of the residual gas is improved. The residence time in the gas vent holes is shortened, and the adhesion of tar components caused by the residual gas inside the gas vent holes is reduced, so maintenance costs can be reduced, such as by reducing the frequency of cleaning the mold.

A resin molding method for molding a resin molded product using the injection molding die according to the first aspect may be configured.

A resin molded product according to a second aspect of the present invention is a resin molded product comprising a convex portion and a planar portion formed around the convex portion, wherein the top portion of the convex portion is formed by injection molding. The trace of the gas vent hole provided in the mold for injection molding is formed, and the trace of the gate provided in the mold for injection molding is formed on the flat portion.

The mark of the gas vent hole in the above configuration is that in the molding using the mold according to the first aspect, the molten resin in the portion facing the gas vent hole at the top of the convex space part is a small amount, but the gas vent hole that it is exposed to the compressed residual gas until the end compared to the surrounding molten resin; Due to subtle differences in the state, etc., the top of the convex part of the molded product has a slightly different shape and property from the surroundings, and is formed as a recognizable trace of the gas vent hole. .

In the above structure, the traces of the gate are formed by solidification of the molten resin in the portion facing the gate opening at the stage of cooling and solidification of the molten resin in the molding process. Since it is solidified in an integrated state, it is necessary to cut and separate the molded product from the resin on the sprue side or runner side at the gate position. is formed as a recognizable gate imprint.

Further, according to the above configuration, the flow of the molten resin and the discharge of the residual gas during molding are smoothed by the gas vent hole and the gate provided in the mold, as in the case of the first aspect. It is possible to provide high-quality molded products by suppressing quality deterioration due to distortion, insufficient filling, discoloration, etc.

According to the present invention, even in the case of a thin molded product having a convex portion, the extent to which the flow of the molten resin in the cavity is hindered due to the convex portion is alleviated, thereby reducing the injection pressure of the molten resin. Furthermore, this low-pressure molding makes it possible to reduce the pressure distortion remaining inside the molded product, the generation of burrs, and the like.

In addition, by obtaining a margin in the molding conditions in this way, it is possible to reduce the number of prototype molds to ensure sufficient filling properties, suppress the manufacturing cost of molds, and even for thin molded products. It is possible to provide a mold and a molded product that can be molded while suppressing deterioration in quality.

FIG. 3 is a cross-sectional view for explaining the injection molding die according to the present embodiment, with the AA′ line cross section in FIG. 2 turned upside down. It is a bottom view explaining the cavity type|mold of the metal mold|die for injection molding which concerns on this embodiment, seeing from the side where a cavity is formed. FIG. 10 is a perspective view illustrating another example of the plug member;

Embodiments of the present invention are described below. In the following description of the drawings, identical or similar parts are given the same or similar reference numerals. However, the drawings are schematic, and the relationship between the thickness and the planar dimensions, the ratio of the thickness of each device and each member, etc. are different from the actual ones. Therefore, specific thicknesses and dimensions should be determined with reference to the following description. In addition, there are portions with different dimensional relationships and ratios between the drawings.

<Thin wall molding technology>
Before describing the configuration of the injection molding die according to the present embodiment, thin-wall molding technology will be described first.

In the following description of the present invention, the term "cavity mold" refers to a mold that is filled with a molten resin into a cavity, which is a molding space inside the mold, and is cooled and solidified so that the molded product can be taken out of the cavity. is mainly divided into two parts. Of these mold parts, the one that is connected to the molten resin injection nozzle of the injection molding machine and is provided with a gate that is the outlet for the molten resin into the cavity. Means mold parts.

Further, the "core mold" means the mold part which is opposed to the "cavity mold" among the mold parts divided into the two parts.

In addition, "flow path resistance" refers to physical factors such as the viscosity of the molten resin injected into the cavity as a fluid, and the distance, thickness, bending, width change, etc. along the flow of the molten resin in the cavity. It means an acting force that hinders the flow of molten resin caused by a shape factor.

In addition, the "thickness" means the dimension of the shortest axis of the cross section perpendicular to the flow path direction of the molten resin in the cavity or molded product. Also, "thin wall" means that the "flow resistance" along the flow of the molten resin in the cavity is large, so the molten resin reaches the end of the cavity and fills the entire cavity before it cools and loses fluidity. means the wall thickness in a relatively difficult cavity or molded article, and does not mean a wall thickness below a certain thickness.

A "thin molded product" means a molded product having a "thin wall thickness". In addition, the "thin molding technology" means a resin molding technology specially devised for stably molding a "thin molded product" which is relatively difficult to fill with molten resin.

In addition, the "induction band" is a band-shaped channel provided in the cavity so that the molten resin injected into the cavity has a particularly low channel resistance in a specific direction. The thickness is thicker than the thickness of the cavity in its peripheral part, and the end of this channel part is connected to the part where the cavity thickness is thinner than this channel part or ends up to the mold wall surface It means a channel that extends and ends in a dead end (hereinafter, the portion where the cavity thickness is thinner than the channel portion of this "induction band" is also referred to as a "thin portion").

In general, the gate is provided at a position where the molten resin is directly injected into the induction band flow path, and the flow path of the induction band starts from this gate position and extends along the flow path to the thin part farthest from the gate position. The end of the connection is defined as the channel end. Therefore, when a gate is positioned in the middle of continuous induction band flow paths, two induction band flow paths are provided from the gate position toward both sides. , it is possible to branch or merge in the middle.

In addition, the "convex part" in the molded product means a concave or protruding part in the direction perpendicular to the main plane part of the molded product, and the concave part or the protruding part It is formed with a relatively thin wall thickness, and in the case of a cavity, it means any part of the concave-convex shape of the cavity formed by overlapping the corresponding concave-convex portions of the cavity mold and the core mold. In addition, the "foot portion of the convex portion" means the boundary portion between the convex portion and the flat portion in the case of the molded product, and the boundary portion between the space portion of the convex portion and the flat space portion in the case of the cavity. . Further, the "protrusion surrounding induction band space" means a cavity space forming an induction band that is in contact with and circulates around the base of the protrusion.

In addition, in the present invention, the term “convex portion” means, as indicated in the definition above, when there is a flat portion that serves as a reference in the molded product, it is concave with respect to the flat portion. It is used as a general term for the part that is on the surface and the part that protrudes. In addition, in the cavity for molding the molded product, the uneven shape is formed according to the unevenness of the cavity mold and the core mold. , as well as the concave and convex portions of the molded product, the term “convex portion” is used as a generic term without distinguishing between the two.

In addition, "residual gas" means the gas that exists in the cavity during the process of filling the cavity with the molten resin. Consists of air and resin volatile components that existed in the runner and sprue.

In addition, "short" means that when molten resin is injected into the cavity and filled, the molten resin cools and solidifies before reaching the end of the cavity, or the discharge of "residual gas" is delayed and the residual gas is released. It means a phenomenon in which a part of the molded product is underfilled due to the fact that the molten resin solidifies without being filled in the part.

Generally, in the injection molding of a molded product, there is residual gas in the cavity, and as the molten resin injected from the gate fills the cavity, the residual gas is driven away from the gate. Compressed, the residual gas pressure works to stop the flow of the molten resin, which is one of the causes of lowering the filling speed.

On the other hand, the injected molten resin is cooled from the portion in contact with the low-temperature mold wall surface in the cavity, and finally loses its fluidity and solidifies, thereby preventing further filling. For this reason, in injection molding, the time required for the molten resin injected into the cavity to solidify and the time for the molten resin to completely fill the cavity by discharging all residual gas (hereinafter also referred to as "cavity filling time"). ), and if the latter time is longer, a short circuit, which is one of the defects due to insufficient filling, will occur.

The cavity filling time is defined as the difference between the injection pressure at the gate, which is the starting end of the molten resin flow path in the cavity, and the pressure of the residual gas with which the tip of the flowing molten resin is in contact (hereinafter, this pressure difference is also referred to as "fluid pressure"). The smaller, the longer.

In addition to the general characteristics of injection molding as described above, in molding thin-walled molded products, compared to thick-walled products, the cross-sectional area per unit width of the flow path is narrower, and the residual gas tends to be at high pressure. , the increase in flow path resistance is one of the factors that prolong the cavity filling time.

Therefore, if the discharge speed of the residual gas is slow, the residual gas is compressed by the injection of the molten resin and becomes high pressure, the flow pressure becomes low, and it becomes a factor that hinders filling, and the temperature rises due to the adiabatic compression of the residual gas, and the molten resin There is also a risk that the ignition point of the resin will be exceeded and the resin will be scorched. Due to the combined behavior of flow path resistance and flow pressure, the cavity filling time tends to be longer in thin-walled molding than in thick-walled moldings. This is a major cause of increasing difficulty in thin-wall molding.

As mentioned above, in thin-wall molding, flow resistance is high and residual gas is inevitably high pressure. The range is gradually expanding.

As one of such technological developments, the development of induction band technology has been made.

When the molten resin is filled into the cavity using an induction band, it is more difficult to fill the thin-walled portions with high flow resistance than the gate portion without using the induction band. The molten resin can reach and fill even thin-walled portions with a relatively short delay, making it easy to mold thin-walled molded products.

<Structure of mold for injection molding>
As shown in FIG. 1 , an injection mold 10 according to this embodiment is an injection mold 10 having a core mold 12 and a cavity mold 14 . A core mold 12 and a cavity mold 14 are overlapped, and a molten resin is injected into a cavity 13 (molding space) formed between the core mold 12 and the cavity mold 14 to form a convex portion and a flat portion. The product is molded. The injection mold 10 also has a gate 16 and a residual gas discharge section 18 .

(cavity)
The cavity 13 according to this embodiment includes a convex space portion 13A, a plane space portion 13B, and an induction band space portion 13C. Although the thickness of the cavity 13 is about 0.4 mm in this embodiment, it can be changed as appropriate in the present invention. 13 A of convex part space parts shape|mold the convex part of a molded product. The planar space portion 13B is formed by forming a planar portion around the convex portion of the resin molded product. The guide band space 13C is strip-shaped, is formed in the convex space 13A and the plane space 13B, and has a space that is thicker than the convex space 13A and the plane space 13B. In addition, in the present invention, the induction band space may be provided in either one of the convex space and the planar space. In addition, in the present embodiment, as shown in FIGS. 1 and 2, the induction band space 13C is formed up to an intermediate portion between the bottom and top of the convex space 13A. When the guide band space is provided in the convex space, it may be formed at any position from the hem to the top of the convex space according to the shape of the convex.

(Convex Circular Induction Band Space)
The convex-circumferential guide band space 13X according to the present embodiment branches from the guide band space 13C, contacts the convex foot, which is the boundary portion between the convex space 13A and the plane space 13B. going around the department. The convex-circumference guide band space 13X is arranged so as to surround the entire periphery of the convex foot portion of each of the convex-part spaces 13A. In addition, in the present invention, the convex-circumference guiding band space may appropriately extend around only a part of the convex-foot foot in consideration of the wall thickness, the convex-portion height, and the like. You may arrange|position so that a part may be divided into several places and it may go around.

As shown in FIG. 2, the surface of the cavity mold 14 facing the core mold includes a convex space corresponding portion 14A corresponding to the convex space portion 13A, a planar space corresponding portion 14B corresponding to the planar space portion 13B, and an induction zone space. It has a guiding band space corresponding portion 14C corresponding to the portion 13C and a convex winding guiding band space corresponding portion 14X corresponding to the convex winding guiding band space portion 13X. Although FIG. 2 exemplifies the case where the number of the projection space corresponding portions 14A is four, in the present invention, the number of the projection space corresponding portions can be appropriately changed to one or more.

In addition, in the present invention, by providing the convex-circling guide band space, the convex-circling guide band space functions as a molten resin reservoir, and the entire length of the convex-circling guide band space is a film to the convex space. It functions as a gate, and as a result, the flow inhibition effect of the flow path bending part at the foot of the convex part, which is a factor that hinders the flow of the molten resin from the planar space part to the convex part space part and increases the flow path resistance, is suppressed. attenuate In addition, the corners formed in the cavity due to the bending of the base of the convex portion and the contact of the surrounding guide band space of the convex portion with the base of the convex portion are rounded in order to reduce the flow impediment factor of the corners. is desirable.

(Gate)
In this embodiment, the gate 16 injects molten resin into the induction band space 13C. The type of gate 16 is a pin gate. It should be noted that other types of gates, such as tunnel gates, may be employed in the present invention.

(Residual gas discharge part)
In this embodiment, the residual gas discharge part 18 is a gas vent hole 18A and a plug member 18B. In addition, in this invention, a residual gas discharge part is not limited to this. For example, a parting surface may be used as a residual gas outlet. Specifically, depending on the shape of the molded product, the mold can be designed so that the parting line passes through the apex of the convex portion, and the parting surface can be used as an outlet for residual gas.

Moreover, in this embodiment, the residual gas discharge part 18 is formed in both the cavity mold 14 and the core mold 12 . In addition, in the present invention, the residual gas discharge part 18 may be formed only in the core mold 12 or may be formed only in the cavity mold 14 . Also, in the present invention, the residual gas discharge section is not essential.

(gas vent hole)
The gas vent hole 18A according to the present embodiment is a hole penetrating from the outside of the mold to the top of the convex space 13A, and one end thereof opens to the top of the convex space 13A.

However, the present invention does not preclude arranging the opening position of the gas vent hole at an arbitrary position between the top of the convex space and the gate. The gas vent hole 18A according to the present embodiment discharges residual gas from the top of the convex space 13A.

In this embodiment, the shape of the opening of the gas vent hole 18A facing the molded product is circular with a diameter of about 2.0 mm. In addition, in the present invention, the size and shape of the opening can be changed as appropriate. The shape of the gas vent hole can be set to any geometric shape, such as a polygonal shape, an elliptical shape, or the like. Therefore, the shape of the trace of the gas vent hole formed in the molded product also changes according to the shape of the gas vent hole.

(plug member)
The plug member 18B according to this embodiment is provided in a detachable state inserted into the gas vent hole 18A. The plug member 18B is a columnar member that adheres to the inner periphery of the gas vent hole 18A. The plug member 18B has a shaft portion and a head portion (flange portion) having a larger diameter than the shaft portion. Although not shown, the head can be detachably fixed to the mold with screws or the like. The outer diameter of the cylindrical shaft portion of the plug member 18B is substantially equal to the inner diameter of the gas vent hole 18A. In addition, in the present invention, the shape of the plug member is not limited to a columnar shape, and may be other shapes such as a prismatic shape depending on the shape of the gas vent hole.

Since the plug member 18B according to this embodiment can be removed from the gas vent hole 18A, it is easy to clean the plug member 18B and the gas vent hole 18A during non-molding.

A gas passage 20 having an opening diameter through which the molten resin cannot pass but the residual gas can pass is formed on the outer peripheral surface of the cylindrical member of the plug member 18B according to the present embodiment. The aperture diameter according to this embodiment is about 2/100 mm. In the present invention, the opening diameter is not limited to that, and the appropriate opening diameter depends on the type of resin material used for molding, the temperature of the molten resin, molding conditions such as injection pressure, the length and flexibility of the gas flow path, etc. In contrast, when designing the mold, an appropriate opening diameter can be arbitrarily determined in consideration of these factors.

(gas flow path)
The gas flow path 20 illustrated in FIG. 1 is formed between the inner surface of the gas vent hole 18A and the outer surface of the shaft of the plug member 18B by closely contacting the outer surface of the plug member 18B and the inner surface of the gas vent hole 18A. It is

In this embodiment, as shown in FIG. 1, the gas flow path 20 provided on the outer surface of the shaft portion of the plug member 18B facing the inner surface of the gas vent hole 18A has a planar shape parallel to the axial direction of the plug member 18B. It is considered to be a gap between When the gas flow path 20 provided on the outer surface of the shaft portion of the plug member 18B is a planar gap parallel to the axial direction, the cylindrical material as the raw material is cut to a predetermined thickness on a plane parallel to the axial direction. Therefore, the plug member 18B according to this embodiment can be easily produced.

In addition, in the present invention, as shown in FIG. 3, the gas flow path 20 may be composed of, for example, a plurality of straight vertical grooves 18B1 extending along the axial direction of the cylindrical member. Further, in the present invention, the gas flow path is not limited to a planar or cylindrical gap along the axial direction or a linear vertical groove. A gas flow path may be formed by combining a plurality of flow paths.

As shown in FIG. 3, the head of the plug member is not essential in the present invention, and the plug member may have only a shaft portion.

Further, in the present invention, the groove width of the longitudinal groove 18B1 as the gas flow path 20 illustrated in FIG. The subsequent gas passages may have any shape and size, for example, each may be widened so as to widen toward the outside where the residual gas exits, or each may be separated longitudinally by grooves along the outer periphery. The grooves may communicate with each other.

(Air injection mechanism)
Although not shown, in the injection mold 10 according to the present embodiment, the outlet of the gas vent hole 18A is communicated with a flow path, the other end of which is connected to an air injection device (not shown). there is In the injection molding process, after cooling and solidification of the molten resin is completed and the mold is opened, the air injection device is activated to inject air from the outlet of the gas vent hole 18A toward the outer surface of the convex portion of the molded product. As a result, the molded article stuck to the core mold 12 or the cavity mold 14 can be pushed out and released from the mold by air pressure.

In the present invention, apart from the gas vent hole, the air injection hole having one end connected to the air injection device and communicating with the flow path may be placed at an arbitrary position in at least one of the core type and the cavity type. can be provided, and the molded product stuck to the core mold or the cavity mold can be extruded and released by air pressure. Such an air injection hole is provided in the core mold or the cavity mold, which is the side to which the molded product sticks when the mold is opened, which is determined according to the shape of the molded product, the selection of the mold dividing surface, and the like.

(bypass mechanism)
Further, in the injection molding die 10 according to the present embodiment, the gas release holes 18A are formed in the core mold and the cavity mold 14, and the insides of the core mold 12 and the cavity mold 14 are not shown, A bypass path branching from the middle of the gas vent hole 18A is formed. That is, one end of the bypass communicates with the gas flow path 20 at a position slightly upstream from the head of the plug member 18B in close contact with the gas vent hole 18A, and the other end of the bypass communicates with the outside of the mold. , the residual gas is vented to the atmosphere.

Moreover, the bypass path is provided in a branched state toward the side surface of the core mold and the cavity mold 14 from the middle of the gas vent hole 18A. In addition, in the present invention, by appropriately providing the bypass passage, the discharge port for the residual gas to the outside air can be provided at an arbitrary position without being limited to the position of the top of the convex portion.

(Resin molded product)
By using the injection mold 10 according to the present embodiment, a molded product having a convex portion and a flat portion formed around the lower portion of the convex portion can be molded. Traces of gas vent holes provided in the mold are formed on the tops of the convex portions of the molded product, and traces of the gate 16 are formed on the plane portion. In addition, in the molded product molded by the resin molding method performed using the injection molding die 10, there is an induction band (convex circumference A rib is formed as a trace of the guide band space portion 13X).

(Effect)
According to the injection molding die 10 according to the present embodiment, the molten resin first has a flow path thicker than the convex space 13A and the plane space 13B. It is injected into the cavity 13 from the gate 16 provided at the position of the induction band space portion 13C having a space portion with a lower flow resistance than 13B. The injected molten resin then quickly reaches the end of the guide band space 13C at a point away from the gate 16 (that is, the point where the flow path resistance of the flow path is high thereafter).

On the other hand, when the molten resin reaches the end of the induction band space 13C , the plane space 13B and the convex space 13A adjacent to the induction band space 13C, which have high flow resistance, are filled with too much molten resin. not in a state of However, when the molten resin reaches the end of the induction band space 13C , the flow of the molten resin is dammed in a region with a high flow path resistance, and as a result, the molten resin pressure inside the induction band space 13C is accumulated. , the pressure-accumulated molten resin permeates and spreads along the induction band space 13C into the flat space 13B and the convex space 13A, which are adjacent to each other, at substantially the same time. , can mold thin-walled products with high quality.

Further, according to the present embodiment, the molten resin injected from the gate 16 into the induction band space portion 13C adjacent to the planar space portion 13B flows down the induction band space portion 13C adjacent to the planar space portion 13B. It reaches the foot of the convex portion, which is the boundary portion between the portion 13B and the convex space portion 13A, and flows into the convex circular guide band space portion 13X branched from the guide band space portion 13C, and from there to the convex space portion 13A at the top. Fill in the direction.

Since the convex-circumference guide band space 13X is provided in contact with the bent portion formed by the flat space 13B and the convex space 13A, the flat space 13B and the convex space 13A are formed. It has the effect of expanding the channel at the bent portion, and has the effect of reducing the channel resistance associated with the bending of the channel.

Further, the convex-circling guide band space 13X is provided around the base of the convex, and the pressure of the molten resin in the convex-circling guide band space 13X is accumulated, which is close to the liquid pressure at the gate position. In this state, the convex-circumference guide band space 13X functions as if it were a film gate for the convex-part space 13A, and the filling property of the convex-part space improves, so that the convex part in contact with the base of the convex part A thin-walled molded product with high quality can be molded as compared with the case without the circling guide band space portion 13X.

Further, according to the present embodiment, the residual gas discharge portion 18 for discharging residual gas is positioned at the top of the convex space portion 13A. For this reason, the residual gas inside the cavity 13 tends to concentrate at the top of the convex space portion 13A due to the flow pressure of the molten resin, but the residual gas in the cavity concentrated at the top passes through the residual gas discharge portion 18. , is discharged to the outside of the mold. As a result, it is possible to suppress deterioration in quality due to gas burns, short circuits, warping, etc. of molded products caused by residual gas.

Further, according to the present embodiment, the residual gas is appropriately discharged to the outside of the mold by the residual gas discharge section 18, so that the residual gas concentrated at the top of the convex space 13A is not excessively pressurized. Suppressed. As a result, the molding pressure required to fill the cavity with the molten resin can be reduced, and as a result, the pressure burden on the molding machine can be reduced, enabling the use of a compact molding machine and reducing costs. can contribute.

Further, according to the present embodiment, the gate 16 is arranged not at the top of the convex space 13A, but in the induction band space 13C provided adjacent to the planar space 13B. For this reason, for example, in the cavity 13, the flow path formed by the induction band space 13C extending from one gate 16 is branched into a plurality of flow paths similarly formed by the induction band space, and the branched flow paths A plurality of convex space portions 13A can be arranged on the downstream side.

In other words, compared to the conventional method in which the gate 16 is provided at the top of each convex space 13A, even when a plurality of convex portions are provided in the molded product, a plurality of gates 16 are formed according to the number of convex portions. No need to put it in a mold. Therefore, the structure of the runners for supplying the molten resin to the gate 16 in a well-balanced manner is relatively simple, and the cost of mold design and manufacture can be reduced.

Further, according to the present embodiment, appropriate degassing can be performed by appropriately replacing the plug members 18B having different residual gas discharge performances according to the type of resin and the amount of residual gas. In addition, since the volatile components of the molten resin become tar-like and gradually contaminate and clog the discharge passage for the residual gas, it is necessary to clean the discharge passage from time to time. is easy to clean.

Further, according to this embodiment, by connecting the flow path connected to the air injection device to the outlet of the gas vent hole 18A, after the mold opening process is finished, the molded product is pushed out of the injection molding mold by the wind pressure of the air. It can be extruded from the mold 10 and demolded.

Further, according to the present embodiment, when releasing the molded product by the air injection pressure using the gas vent hole 18A of the molded product, compared with the case of using the ejector pin to release the mold, Molded products are not damaged by mechanical impact.

Further, according to the present embodiment, by connecting a channel (not shown) connected to a vacuum device to the outlet of the gas vent hole 18A, residual gas in the cavity 13 can be sucked through the gas vent hole 18A. becomes possible. As a result, the residual gas discharge efficiency in the cavity is improved, and quality deterioration due to gas burning, short circuit, warpage, etc. of the molded product caused by the residual gas can be suppressed.

Moreover, according to the resin molding method using the injection molding die 10 according to the present embodiment, even a thin molded product can be efficiently molded with high quality. In addition, the molding using the injection molding die 10 according to the present embodiment has traces of gas vent holes formed on the tops of the convex portions of the molded product, and the planar portion of the molded product has It is indicated by the formation of gate traces and the formation of ribs, which are the traces of the induction bands that are in contact with the boundary between the convex portion and the flat portion.

<Appendix>
Based on the present embodiment described above, the present invention will be additionally described below as an appendix.

(Examination of Prior Art)
In general, there is a residual gas in the cavity, and the pressure of the residual gas in the cavity is approximately atmospheric pressure when the molten resin is started to be injected. Rise. On the other hand, since the space in the cavity is occupied by the molten resin, it is pushed by this molten resin, and part of the residual gas in the cavity passes through a small gap on the parting surface of the mold, etc. It is discharged outside.

However, the gap between the molds is very narrow to the extent that the molten resin cannot leak out, and therefore the discharge rate of the residual gas is generally relatively slow. For this reason, the pressure of the residual gas in the cavity will continue to increase substantially until the residual gas is finally completely discharged or the injection of the molten resin is stopped. Moreover, the pressure of the residual gas within the cavity acts as a force to stop the flow of the injected molten resin within the cavity.

Such an increase in the internal pressure of the residual gas impedes the flow of the molten resin in the cavity, resulting in insufficient filling, partial lack of thickness or unevenness in thickness, or complete filling of the molten resin. This is one of the causes of short circuits, which are parts that are not connected. In addition, when the residual gas is adiabatically compressed and the pressure rises, the gas temperature also rises, and eventually the ignition point of the molten resin is exceeded and the surface of the resin is scorched. In other words, there also arises a problem that the quality of the thin-walled molded product deteriorates.

Patent Literature 1 does not disclose anything about the resistance of the flow path of the molten resin in the cavity and the effect of residual gas when injection molding a molded product. For this reason, the technique disclosed in Patent Document 1 alone cannot solve the problem of quality degradation of molded products caused by high flow path resistance and delay in discharge of residual gas in injection molding.

Further, when the inventors of the present invention examined the technique of Patent Document 2, it was confirmed that it is possible to improve the filling property of the molten resin during injection molding by providing an induction band in the cavity. However, it has been found that sufficient quality may not be obtained depending on the shape and size of the molded product, such as the thinness of the wall thickness and the number of protrusions.

In the injection molding of a molded product having a convex portion as shown in Patent Document 2, as a method of suppressing the increase in pressure of residual gas in the cavity portion corresponding to the convex portion, for example, a gate, which is the starting point of the flow of molten resin, is provided. , a method of arranging it at a mold position corresponding to the top of the projection.

However, according to this method, it is necessary to arrange all the gates at the mold positions corresponding to the tops of the projections, so as the number of projections increases, the number of gates also increases. For example, when the molded product is an egg carton, usually 10 or more convex parts are often required in one molded product, and when the lid part is integrally molded, it is nearly twice as large. gate number is required. As a result, it becomes necessary to stretch runners according to the arrangement of the gates, which makes it difficult to achieve injection balance between the gates, and also increases the complexity of the mold, increasing the processing load on the mold. As a result, there is a problem that the manufacturing cost of the mold increases.

(Convex Circular Induction Band Space)
In the present invention, through trial production and research by the inventor, in the injection molding of a molded product with a thin wall and a complex shape with unevenness, if the molten resin is filled to the end part in the cavity according to the shape, the cross-sectional area of the flow path It has been found that the flow path is longer than that of , and the flow path resistance is high due to the large number of curved portions of the flow path, which reduces the filling property.

Therefore, first, the gate is provided in the induction band space formed in a part of the planar space, and the molten resin is used as a pseudo runner in the induction band space, and the vicinity of the base of the convex portion, which is the largest bend, Further, a convex portion surrounding guide band space is provided that contacts and surrounds the convex base portion, and is preferably provided around the entire circumference of the convex portion base portion. In some cases, it is also possible to provide a convex-circling induction band space part in a part of the convex-portion foot part, and the convex-circulation-induction band space part guides the molten resin to the periphery of the convex-portion foot part, and makes the convex-portion circumference. Using the induction band space as a pseudo-film gate, the molten resin pressure-accumulated in the convex-surrounding induction band space is injected into the thin-walled portion that constitutes the wall surface of the convex from the base of the convex. Design the mold cavity structure.

In addition, in the arrangement of the convex portion encircling guide band space, if the convex portion is large and the filling of the molten resin in the convex thin portion is insufficient, the convex portion is branched from the convex portion encircling guide band space. It is also possible to freely provide an induction band space portion that crawls up on the side wall of the portion.

Further, the convex-circling guide band space is formed so as to be in contact with the base of the convex, and preferably is formed so as to extend over the wall of the convex. are formed so as to be connected by a smooth curved surface without corners. In addition, if the protruding portion encircling guide band space cannot be provided in contact with the protruding foot portion depending on the shape of the molded product, the distance from the protruding portion encircling guiding band space portion to the protruding portion foot portion is It suffices if the flow path resistance at the ridges is sufficiently close to the extent that the flow path resistance at the ridges does not become a major obstacle for filling the convexes with the molten resin.

By adopting such a mold structure, the flow path resistance of the flow path from the gate to the tip of the projection is significantly reduced compared to the case where the projection winding guide band space is not used. A solution is provided to the problem of poor fillability of the protrusions.

In addition, when the flow path resistance at the time of filling the molten resin is lowered, the injection pressure of the molten resin can be lowered, so the liquid pressure of the molten resin is also lowered, resulting in a low-pressure molding state. Combined with the idea of discharging to the outside, there is also an effect of suppressing the increase in pressure of the residual gas.

In addition, if the pressure of the residual gas is not too high, the temperature of the residual gas will not exceed the ignition point of the molten resin due to adiabatic compression, and it will be possible to suppress gas burn defects and prevent distortion from remaining in the molded product due to high pressure. In addition, since the pressure burden is reduced, molding can be performed even with a small molding machine, which has the effect of reducing costs.

In addition, by also providing an exhaust hole for the residual gas at the apex of the convex portion, the pressure of the residual gas can be further lowered. As in the case of lowering the pressure, the filling property is improved, and low-pressure molding becomes possible, and effects such as suppression of gas burning and distortion and downsizing of the molding machine can be obtained.

The proposal of providing the convex-circumferential guide band space in contact with the base of the convex, which is the main point of the present invention, is a technique for improving the flow path resistance of the bent portion of the convex, and also has a gas vent hole at the top of the convex. is a technique for improving discharge of residual gas in the convex portion, and both have the effect of improving filling properties of the convex portion and suppressing increase in pressure of residual gas in the entire cavity.

In addition to the effects described above, the effects obtained by suppressing the increase in the pressure of the residual gas include the suppression of burrs caused by the residual gas pressure and the suppression of the injection pressure of the molten resin. In addition, the stress applied when the resin solidifies is reduced, warpage and deformation of the molded product are suppressed, and the cooling time provided to correct warpage and deformation can be shortened, shortening the molding cycle. Injection molding machine can be made smaller by lowering the injection pressure, resulting in cost reduction. Similarly, by lowering the injection pressure, the mold clamping force can be reduced, and the ability to discharge residual gas from the parting surface is increased. Effects such as being able to keep the pressure low can be obtained.

From this specification, the aspects described in aspects 1 to 3 below are conceptualized and included in the present invention.

An injection mold according to aspect 1 of the present invention has a core mold and a cavity mold, and is formed between the core mold and the cavity mold by overlapping the core mold and the cavity mold. An injection mold for molding a resin molded product having a convex portion and a flat portion by injecting a molten resin into a cavity, wherein the cavity includes a convex space portion for molding the convex portion and the convex portion. and an induction band formed in at least one of the convex space and the planar space and having a greater thickness than the convex space and the planar space. a space portion, wherein the guide band space portion includes a convex portion surrounding guide band space portion that is in contact with and surrounds the boundary portion between the convex portion space portion and the planar space portion; A gate for injecting molten resin is provided in the induction band space.

According to the above configuration, the molten resin injected from the gate into the induction band space of the cavity has a thicker flow path than the convex space or the plane space, and therefore flows from the convex space or the plane space. Through the guide strip space having a space with low road resistance, it quickly reaches the end of the guide strip space that circles the plane space and the convex space at a point away from the gate. In addition, since the end of the flow path with low flow resistance along the induction band space is connected to the part with high flow resistance, the molten resin continues to flow after the end of the induction band space is filled. Pressure is accumulated in the molten resin inside the induction band space according to the applied injection pressure.

As a result, under relatively high pressure, the molten resin flows along the induction band space into the laterally adjacent flat space and convex space, and spreads throughout the mold. As a result, defects such as short circuits are less likely to occur, and high-quality thin-walled molded products can be molded.

In the above configuration, the induction band space is formed mainly in a planar space where a straight flow channel can be relatively secured from the viewpoint of flow path resistance. The space may be formed in the convex space, or may be formed in both the plane space and the convex space. In addition, it is desirable to provide a gate for injecting molten resin into the induction band space at the position of the induction band space formed in the planar space from the viewpoint of efficiently arranging the induction band network starting from the gate. An arbitrary number of guide band spaces can be provided at arbitrary positions in accordance with the dimensions and shape of the molded product.

Further, according to the above configuration, the guide band space portion includes the convex portion encircling guide band space portion which is in contact with the convex portion foot portion and surrounds the convex portion foot portion, so that the convex portion encircling guide band space portion is formed by the molten resin. It acts as a reservoir, and the entire length of the protruding surrounding guide band space plays the role of a film gate to the protruding space. It reduces the flow obstruction effect of the curved portion of the flow path at the foot of the convex portion, which is a factor that increases the resistance. For this reason, defects such as short-circuiting are less likely to occur in the convex portion, and high-quality thin-walled molded products can be molded, as compared with a mold that does not have such a convex-surrounding guide band space portion. In addition, it is desirable that both the inner peripheral wall surface and the outer peripheral wall surface of the corner portion of the flow passage curved portion have an R shape (roundness).

In the injection mold according to aspect 2 of the present invention, in aspect 1, at least one of the core mold and the cavity mold discharges residual gas remaining at the top from the top of the convex space. It has a residual gas exhaust.

According to the above configuration, since the induction band space portion is provided with the convex portion winding guide band space portion that is in contact with and surrounds the convex portion foot portion, in addition to improving the filling property of the molten resin into the convex portion space portion, In addition, at least one of the core mold and the cavity mold is provided with a residual gas discharge part for discharging residual gas from the top of the convex space. Since the residual gas is appropriately discharged to the outside of the mold by the residual gas discharge part, the residual gas concentrated in the vicinity of the top of the convex space is excessively compressed and is suppressed from becoming high pressure and hindering the flow of the molten resin. The filling property of the molten resin into the inner space is further improved.

In the present invention, the residual gas discharge part may have any structure and shape as long as a gas flow path extending from the cavity through which the molten resin cannot pass but through which the residual gas can pass to the outside of the mold is formed. However, for example, at least one of the core mold and the cavity mold has a gas vent hole extending from the outer surface of the mold to the top of the convex space, and a plug member detachably inserted into the gas vent hole. The plug member is a rod-shaped member in which at least the entire outer peripheral surface of the portion in contact with the top of the convex space is in close contact with the entire inner peripheral surface of the gas vent hole. A gas flow path through which the molten resin cannot pass but the residual gas can pass may be formed between the inner peripheral surface.

Further, in the present invention, when the gas vent hole is used as the residual gas discharge part, a vacuum device is connected to the outlet of the gas vent hole, and the residual gas discharged from the gas vent hole is sucked by the vacuum device, and the convex portion Residual gas evacuation from the top of the void may be facilitated.

As an aspect 3 of the present invention, a resin molding method for molding a resin molded product using the injection molding die according to the aspect 1 may be configured. As described in Mode 1, the resin molding method with the above configuration can provide a high-quality resin molded product in which deterioration in quality due to distortion, insufficient filling, discoloration, etc. of the molded product is suppressed.

<Other embodiments>
While the present invention has been described by the above disclosed embodiments, the statements and drawings forming part of this disclosure should not be construed as limiting the invention. The present invention includes embodiments obtained by appropriately combining each of the embodiments described above and various embodiments not described above, and the technical scope of the present invention is reasonable from the above description. It is determined only by the matters specifying the invention in the scope of claims.

10 Mold for injection molding 12 Core mold 13 Cavity 13A Convex space 13B Plane space 13C Induction band space 13X Convex surrounding guide band space 14 Cavity mold 14A Convex space corresponding portion 14B Plane space corresponding portion 14C Induction band Space-corresponding portion 14X Convex circumference induction band Space-corresponding portion 16 Gate 18 Residual gas discharge portion 18A Gas vent hole 18B1 Vertical groove 18B Plug member 20 Gas flow path

Claims (6)

It has a core mold and a cavity mold, the core mold and the cavity mold are overlapped, and a convex portion and a flat portion are formed by injecting a molten resin into a cavity formed between the core mold and the cavity mold. An injection mold for molding a resin molded product having
The cavity is formed in at least one of a convex space for forming the convex, a planar space for forming the planar portion around the convex, and the convex space and the planar space. , a band-shaped induction band space portion having a space portion thicker than the convex space portion and the planar space portion,
a gate for injecting molten resin into the induction band space;
a residual gas discharge part formed in at least one of the core mold and the cavity mold for discharging residual gas remaining in the top from the top of the convex space;
Injection mold with The residual gas discharge part is detachably inserted into a gas vent hole provided in at least one of the core mold and the cavity mold and reaching the top of the convex space from the outer surface of the mold, and the gas vent hole. a plug member;
The plug member is a rod-shaped member having at least the entire outer peripheral surface of a portion in contact with the top of the convex space in close contact with the entire inner peripheral surface of the gas vent hole,
Between the outer peripheral surface of the rod-shaped member and the inner peripheral surface of the gas vent hole in the tight contact portion, a gas flow path is formed through which the molten resin cannot pass but the residual gas can pass.
The mold for injection molding according to claim 1. A channel connected to an air injection device communicates with an outlet of the gas vent hole,
The air injection device is used to inject air from the gas vent hole onto the outer surface of the convex portion of the resin molded product, and the resin molded product is pushed out from at least one of the core mold and the cavity mold by the pressure of the air. to release the mold,
The mold for injection molding according to claim 2. A channel connected to a vacuum device communicates with an outlet of the gas vent hole,
The vacuum device sucks the residual gas discharged from the gas vent hole, and promotes the discharge of the residual gas from the top of the convex space.
The mold for injection molding according to claim 2. A resin molding method for molding a resin molded product using the injection molding die according to claim 1 . A resin molded product comprising: a plurality of convex portions ;
The apex of the convex portion is formed with traces of gas vent holes provided in the molding die,
Traces of gates provided in the molding die are formed on the flat portion,
Resin molded product.

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