JP6706803B2 - Sprue bush - Google Patents

Description

The present invention relates to a sprue bush. More particularly, the present invention relates to sprue bushings used in molds.

One of the technologies that has supported Japan's "manufacturing" industry is molding technology that uses dies. Examples of such molding technique include a pressure molding method, an injection molding method, and an extrusion molding method. Of these molding methods, the injection molding method is a method of obtaining a molded product from a molten raw material resin using an injection molding die.

In the injection molding method, inside a mold cavity 203′ composed of one mold (core side mold) 201′ of the injection molding mold 200′ and the other mold (cavity side mold) 202′. The molten raw material resin is injected into the container (see FIG. 9A). The injected molten raw material resin is cooled and solidified in the mold cavity 203' to be a molded product. Injection of the molten raw material resin into the mold cavity 203' is generally performed through the sprue bush 100'.

As shown in FIG. 9(A), a raw resin flow path 10' is provided in a sprue bush 100' used in an injection molding die 200'. The raw material resin flow path 10' extends from one end portion 10a' into which the molten raw material resin is introduced to the other end portion 10b' which communicates with the inside of the mold cavity 203'.

The raw material resin flow path 10' is tapered so that a molded product can be taken out easily. Specifically, the width dimension W′ of the raw material resin flow channel 10′ gradually increases as it extends from the one end 10a′ to the other end 10b′. As shown in FIG. 9A, while the width W ₁ ′ of the upstream side 10A′ of the raw material resin flow channel 10′ is relatively small, the width 10B′ of the downstream side 10B′ of the raw material resin flow channel 10′ is relatively small. dimension W _{2 'is} made relatively large.

The tapered raw material resin flow path 10' is preferable in terms of taking out the molded product, but is not necessarily preferable in terms of cooling and solidification of the molten raw material resin. For example, when the tapered raw material resin flow path 10' becomes longer, the influence of the relatively large width dimension W'on the downstream side becomes larger accordingly, and the molten raw material resin becomes difficult to cool and solidify. If the molten raw material resin is difficult to cool and solidify, the time required from injection of the molten raw material resin to removal of the molded product increases, resulting in a longer molding cycle. Therefore, as shown in FIG. 9B, the cooling medium flow passage 20' may be provided around the raw material resin flow passage 10'.

International Publication No. 2008-038694

However, the following problems may occur in the sprue bush 100' (see FIG. 9B) provided with the cooling medium flow passage 20'.

When the cooling medium flows through the cooling medium flow passage 20', the cooling heat of the cooling medium is transferred to the molten raw material resin in the raw material resin flow passage 10' because the sprue bush 100' is made of a metal member. However, the molten raw material resin in the raw material resin flow channel 10' tends to be cooled and solidified more easily on the upstream side 10A' than on the downstream side 10B' due to the relatively small width dimension of the upstream side 10A'. Have.

If the molten raw material resin is cooled and solidified in the upstream side 10A' before the downstream side 10B', the raw material resin flow passage 10' may be substantially closed. In this case, the molten raw material resin cannot be suitably injected through the raw material resin flow channel 10', and a predetermined amount of molten raw material resin cannot be filled in the mold cavity 203'. Therefore, a molded product having a desired shape cannot be finally obtained.

The present invention has been made in view of such circumstances. That is, an object of the present invention is to provide a sprue bush capable of more suitably cooling the molten raw material resin in the raw material resin passage.

In order to achieve the above object, in the present invention,
A sprue bush having a raw material resin passage and a cooling medium passage provided around the raw material resin passage,
Provided is a sprue bush provided with a low heat transfer portion that provides relatively smaller heat transfer than a region other than the local region in a local region between the upstream side portion of the raw material resin flow channel and the cooling medium flow channel. It

In the sprue bush of the present invention, the molten raw material resin in the raw material resin passage can be cooled more suitably.

Sectional drawing which showed typically the sprue bush which concerns on one Embodiment of this invention. Sectional drawing which showed typically the sprue bush which has the area|region which consists of hollow parts. Sectional drawing which showed typically the sprue bush which has the hollow part of a vacuum state. Sectional drawing which showed typically the sprue bush which has the hollow part used as a heat medium flow path. Sectional drawing which showed typically the sprue bush which has the hollow part in which the powder body was provided. Sectional drawing which showed typically the sprue bush which has the area|region which consists of porous materials. Sectional drawing which showed typically the sprue bush which has the cooling medium flow path in which the coating layer was provided. Sectional views schematically showing a process mode of stereolithography compound processing in which the powder sintering lamination method is carried out (FIG. 8(a): during powder layer formation, FIG. 8(b): during solidification layer formation, FIG. c): In the middle of stacking) Sectional view schematically showing a conventional sprue bush (FIG. 9(A): no cooling medium flow passage, FIG. 9(B): cooling medium flow passage)

Hereinafter, an embodiment of the present invention will be described in more detail with reference to the drawings. The forms and dimensions of various elements in the drawings are merely examples and do not reflect actual forms and dimensions.

As shown in FIG. 1, a sprue bush 100 according to an embodiment of the present invention is a metal member including a flange portion 101 and a base portion 102 integrated with the flange portion 101. As shown in the drawing, the sprue bush 100 has a raw material resin flow path 10 and a cooling medium flow path 20 provided around the raw material resin flow path 10 inside.

The raw material resin flow path 10 of the sprue bush 100 extends from one end 10a into which the molten raw material resin is introduced to the other end 10b communicating with the inside of the mold cavity. Based on the flow of the molten raw material resin at the time of molding, the one end portion 10a corresponds to the "upstream side" end portion, and the other end portion 10b corresponds to the "downstream side" end portion. The raw material resin flow passage 10 is tapered in order to facilitate taking out of a molded product obtained by cooling and solidifying the molten raw material resin. More specifically, the raw material resin flow path 10 is configured such that the width dimension W gradually increases as it extends from the one end 10a to the other end 10b. That is, the width dimension W ₁ of the upstream side 10A of the raw material resin flow channel 10 is relatively small, whereas the width dimension W ₂ of the downstream side 10B of the raw material resin flow channel 10 is relatively large.

The cooling medium flow path 20 of the sprue bush 100 is a flow path for flowing the cooling medium, and is a flow path that contributes to cooling the molten raw material resin in the raw material resin flow path 10. That is, at the time of molding, the molten raw material resin in the raw material resin flow passage 10 is subjected to the temperature drop due to the cooling medium flowing through the cooling medium flow passage 20. The term “cooling medium” as used herein refers to a fluid that can give a cooling effect to the molten raw material resin in the raw material resin flow channel 10, and is, for example, cooling water or cooling gas.

In the present specification, the "upstream side of the raw material resin flow path" refers to a portion located on the proximal side with respect to the one end portion 10a into which the molten raw material resin is introduced. On the other hand, in the present specification, the “downstream side of the raw material resin flow path” refers to a portion located on the distal side with respect to the one end portion 10a into which the molten raw material resin is introduced. The boundary between the upstream side and the downstream side of the raw material resin flow passage is not particularly limited, but is, for example, “a half-divided point of the entire longitudinal dimension of the raw material resin flow passage”. More specifically, the "upstream side of the raw material resin flow passage" is, for example, a region from one end 10a of the raw material resin flow passage 10 to a "half-divided point of the entire longitudinal dimension of the raw material resin flow passage 10". Equivalent to. On the other hand, the “downstream side of the raw material resin flow passage” corresponds to, for example, a region from the “half-divided point of the entire longitudinal dimension of the raw material resin flow passage 10” to the other end 10b of the raw material resin flow passage 10.

In the sprue bush 100 of the present invention, as shown in FIG. 1, the local area 100A between the upstream side 10A of the raw material resin flow path 10 and the cooling medium flow path 20 is more relative to the local area 100B than the local area 100A. The low heat transfer portion 30 having a relatively small heat transfer is provided. That is, the low heat transfer portion 30 of the sprue bush of the present invention has a local or limited form between the raw material resin flow passage 10 and the cooling medium flow passage 20. In the present specification, the “low heat transfer portion” is a portion of the sprue bush that reduces or inhibits a phenomenon in which cooling heat resulting from the cooling medium in the cooling medium flow passage 20 is transferred to the molten raw material resin in the raw material resin flow passage 10. It refers to that.

In the sprue bush 100 of the present invention, since the low heat transfer portion 30 exists between the upstream side 10A of the raw material resin flow passage 10 and the cooling medium flow passage 20, the cooling heat due to the cooling medium in the cooling medium flow passage 20 is generated. It becomes difficult to transmit to the upstream side 10A. The difficulty of transmitting the cooling heat to the upstream side 10A means that the cooling of the molten raw material resin on the upstream side 10A is more suitably suppressed. Therefore, the phenomenon that the molten raw material resin is cooled and solidified in the upstream side 10A before the downstream side 10B is less likely to occur, and the raw material resin flow passage 10 can be prevented from being blocked.

When the blockage of the raw material resin flow passage 10 is prevented, the molten raw material resin can be more suitably injected through the raw material resin flow passage 10. Therefore, in the sprue bush 100 of the present invention, a predetermined amount of molten raw material resin can be filled in the mold cavity, and finally a molded product having a desired shape can be obtained.

Hereinafter, a method for manufacturing the sprue bush according to the embodiment of the present invention will be described in detail. The sprue bush 100 according to the embodiment of the present invention can be manufactured by using the “powder sintering lamination method” described later. However, the sprue bush 100 may be manufactured by forming a part of the sprue bush 100 by the powder sintering lamination method and cutting the remaining part of the metal structure prepared in advance. .. Examples of such "a part of the sprue bush" include the base portion 102 (or a part thereof) of the sprue bush (see FIG. 1). Examples of the “remaining portion of the sprue bush” include the flange portion 101 of the sprue bush (or a portion obtained by adding a part of the base portion 102 thereto) (see FIG. 1).

The “powder sintering lamination method” used for manufacturing the sprue bush is a method capable of manufacturing a three-dimensional shaped object by irradiating a powder material with a light beam. In the powder sinter lamination method, a three-dimensional shaped object is manufactured by alternately repeating powder layer formation and solidified layer formation based on the following steps (i) and (ii).
(I) A step of irradiating a predetermined portion of the powder layer with a light beam and sintering or melting and solidifying the powder at the predetermined portion to form a solidified layer.
(Ii) A step of forming a new powder layer on the obtained solidified layer and similarly irradiating it with a light beam to form a further solidified layer.

According to such a manufacturing technique, a complicated three-dimensional shaped object can be manufactured in a short time. When an inorganic metal powder is used as the powder material, the obtained three-dimensional shaped object can be used as the sprue bush or a part thereof.

An example is a powder sintering lamination method in which a metal powder is used as a powder material and a three-dimensional shaped object produced thereby is used as a sprue bush or a part thereof. As shown in FIG. 8, first, the squeegee blade 23 is moved to form the powder layer 22 having a predetermined thickness on the modeling plate 21 (see FIG. 8A). Next, the light beam L is irradiated to a predetermined portion of the powder layer 22 to form the solidified layer 24 from the powder layer 22 (see FIG. 8B). Subsequently, a new powder layer is formed on the obtained solidified layer and irradiated with a light beam again to form a new solidified layer. When the powder layer formation and the solidified layer formation are alternately repeated in this manner, the solidified layers 24 are laminated (see FIG. 8C), and finally the three-dimensional solid layer composed of the laminated solidified layers 24 is formed. A shaped object can be obtained.

In order to provide the raw material resin flow path 10 and the cooling medium flow path 20 (see FIG. 1) in the sprue bush 100 as a three-dimensional shaped object, for example, a non-irradiation part where the light beam is not partially irradiated during formation of the solidified layer Form. More specifically, when the solidified layer is formed by the powder sinter lamination method, the predetermined regions serving as the raw material resin flow path and the cooling medium flow path are not irradiated with the light beam and are not irradiated. Then, when the powder present in the non-irradiated portion is finally removed, the raw material resin flow passage 10 and the cooling medium flow passage 20 are obtained in the sprue bush 100 used as the three-dimensional shaped object.

As described above, when a part of the sprue bush 100 (for example, the base portion 102 of the sprue bush) is formed by the powder sintering method, the remaining portion of the sprue bush (for example, the flange portion 101 of the sprue bush) is formed. On the other hand, a part of the raw material resin flow path 10 and a part of the cooling medium flow path 20 may be formed on the metal structure using a cutting tool. As the cutting tool, for example, an end mill can be used. The end mill may be a two-blade ball end mill of cemented carbide material. A part of the raw material resin flow passage 10 formed in the part of the sprue bush and a part of the raw material resin flow passage 10 formed in the remaining part of the sprue bush are connected to each other. Further, a part of the cooling medium passage 20 formed in the part of the sprue bush and a part of the cooling medium passage 20 formed in the remaining part of the sprue bush are also connected to each other. By thus combining the sprue bush precursors with each other, a desired sprue bush can be obtained.

[Specific Embodiment of Low Heat Transfer Part]
Below, the specific aspect of a low heat transfer part is demonstrated.

The low heat transfer portion provided in the sprue bush is roughly divided into two specific modes.

The first specific mode is a mode using a hollow portion. In such an aspect, the low heat transfer part is composed of a hollow part. The hollow portion may be used (1) in a vacuum state, (2) as a heat medium flow path for flowing a heat medium, or (3) as a space in which a powder body is provided.

(1) When used in a vacuum state, the number of gas molecules that conduct heat is small in the hollow portion, so that the hollow portion can function suitably as a “heat insulating region”. Further, in the case of (2) the heat medium flow passage, heat conduction by the cooling medium in the cooling medium flow passage is reduced by the heat generated from the heat medium in the heat medium flow passage and in the vicinity thereof, so that such a hollow portion is “cooled”. It can be suitably functioned as a “heat conduction reduced region”. (3) When a powder body is provided, the powder particles come into "point" contact with each other in the hollow portion, and the heat conduction of the powder body becomes relatively low. It can function appropriately.

The second specific mode is a mode in which the material of the sprue bush is locally changed.

For example, in the sprue bush according to the second specific aspect, the low heat transfer portion is made of a porous material. Due to the presence of a large number of voids in the porous material, the cooling heat caused by the cooling medium in the cooling medium flow path is reduced by the porous material. Therefore, such a porous material can suitably function as a “cooling heat conduction lowering region”.

In the present invention, the "low heat transfer portion locally provided between the upstream side of the raw material resin flow path and the cooling medium flow path" can be preferably embodied by at least one of the above two specific modes. The details will be described below.

[(1) Low heat transfer part: hollow part]
In the sprue bush 100 according to the embodiment of the present invention, as shown in FIG. 2, the low heat transfer portion is composed of the hollow portion 40. The “hollow portion” here refers to a space region of the sprue bush 100 formed at least between the upstream side 10A of the raw material resin flow passage 10 and the cooling medium flow passage 20. By using the hollow portion 40 as the low heat transfer portion, the cooling heat generated from the cooling medium in the cooling medium passage 20 is less likely to be transmitted through the hollow portion 40. When such cooling heat is difficult to be transmitted through the hollow portion 40, cooling of the molten raw material resin in the upstream side 10A of the raw material resin flow channel 10 is suppressed more suitably, and the molten raw material resin is cooled in the upstream side 10A before the downstream side 10B. The phenomenon of solidification is less likely to occur. That is, the blockage of the raw material resin flow path 10 can be prevented more preferably.

Hollow part: vacuum state The hollow part 40 may be in a vacuum state (see FIG. 3 ). The “vacuum state” here means a space state having a pressure lower than atmospheric pressure. When the hollow portion 40 is in a vacuum state, the hollow portion 40 is in a state in which the amount of air is relatively small. That is, the hollow portion 40 has less gas molecules that transfer heat. When the number of gas molecules that transfer heat to the hollow portion 40 is small, it is difficult for the cooling heat resulting from the cooling medium in the cooling medium passage 20 to be transferred to the upstream side 10A of the raw material resin passage 10 due to this. This means that the cooling of the molten raw material resin on the upstream side 10A is more suitably suppressed. Therefore, the phenomenon in which the molten raw material resin is cooled and solidified in the upstream side 10A before the downstream side 10B is less likely to occur, and the blockage of the raw material resin flow path 10 can be more preferably prevented.

The hollow portion 40 does not need to be in a completely vacuum state, and may have air entering from the outside. Air has a lower thermal conductivity than metallic materials. For example, at room temperature, a metal material (for example, an iron material) has a thermal conductivity of about 80 W·m ⁻¹ ·K ⁻¹ , whereas air has a thermal conductivity of about 0.02 W·m ⁻¹ ·K. ^-1 . Therefore, even if air unintentionally enters the hollow portion, the cooling heat from the cooling medium is reduced due to the existence of the hollow portion 40.

The hollow portion 40 in a vacuum state can be obtained by the following method, for example. First, when the solidified layer is formed by the powder sinter lamination method, the light beam is not irradiated to a certain local region, and the powder in the local region is finally removed to form the hollow portion. The present invention is not limited to this, and the hollow portion may be formed by performing a cutting process on a local region where the metal structure is present. After forming the hollow portion, if a so-called “vacuum drawing” is performed from the communicating portion 45 (see FIG. 3) with the outside, the hollow portion 40 in a vacuum state can be obtained (the communicating portion for maintaining the vacuum state). 45 may be appropriately sealed.

Hollow part: Heat medium flow path The hollow part 40 may be a heat medium flow path 40a as shown in FIG. 4, for example. In the illustrated embodiment, a part of the heat medium flow channel 40a is positioned between the upstream side 10A of the raw material resin flow channel 10 and the cooling medium flow channel 20 (see FIG. 4). The "heat medium flow channel" here refers to a flow channel for flowing the heat medium. The heat carrier may be a fluid such as hot water, steam or hot air.

In the sprue bush 100 in which the hollow portion 40 serves as the heat medium passage 40a, the cooling medium flows in the cooling medium passage 20 and the heat medium flows in the heat medium passage 40a. Since at least a part of the heat medium flow passage 40a is positioned between the upstream side 10A of the raw material resin flow passage 10 and the cooling medium flow passage 20, the cooling heat due to the cooling medium in the cooling medium flow passage 20 is heat. It is reduced in the region of the medium channel 40a and its vicinity. That is, the cooling heat of the cooling medium passage 20 is less likely to be transmitted to the upstream side 10A of the raw material resin passage 10. As a result, the phenomenon in which the molten raw material resin is cooled and solidified in the upstream side 10A before the downstream side 10B is less likely to occur, and the blockage of the raw material resin flow path 10 can be more preferably prevented.

The heat medium flow passage 40a is preferably connected to a heat medium source and can be suitably obtained by connecting a heat medium pipe including a fluid pump or the like to the hollow portion 40.

Hollow part: powder body filling In the sprue bush 100 which concerns on one Embodiment of this invention, a powder body may be used. As shown in FIG. 5, the powder body 50 may be provided in the hollow portion 40, for example. The "powder body" here refers to an aggregate of powder particles made of, for example, at least one of metal powder and resin powder. The metal powder may be, for example, an iron-based metal powder having an average particle size of about 5 μm to 100 μm. The resin powder may be nylon, polypropylene, ABS or the like having an average particle size of about 30 μm to 100 μm.

When the powder body 50 is provided in the hollow portion 40, the heat conduction becomes relatively low in the hollow portion 40 because the powder particles are in “point” contact with each other. As a result, the cooling heat due to the cooling medium in the cooling medium flow path 20 is reduced by the powder body 50. That is, the cooling heat is less likely to be transferred from the cooling medium flow passage 20 to the upstream side 10A of the raw material resin flow passage 10. This makes it difficult for the molten raw material resin to cool and solidify in the upstream side 10A before the downstream side 10B, and the raw material resin flow passage 10 can be more appropriately prevented from being blocked.

When the powder body is provided in the hollow portion 40, the effect of improving the structural strength of the sprue bush 100 can also be obtained. Since the hollow portion 40 forms a “space” inside the sprue bush, it can be said that the presence of the hollow portion 40 is generally not preferable in terms of the structural strength of the sprue bush 100. In this respect, when the powder body 50 is provided in the hollow portion 40 as shown in FIG. 5, it is possible to compensate for the decrease in strength caused by the hollow portion 40. That is, the powder body 50 provided in the hollow portion 40 can function as a reinforcing member for structural strength. From the viewpoint of suitably supplementing the structural strength in this way, it is preferable that the hollow body 40 is filled with the powder body 50 in a larger amount.

The hollow portion 40 filled with the powder body 50 can be obtained by carrying out the powder sintering lamination method. Specifically, when the solidified layer is formed by the powder sinter lamination method, the area where the powder body is provided is not irradiated with the light beam and is set as a non-irradiated portion. Then, if the powder of the non-irradiated part is not removed and the powder is left to the end, the hollow part 40 in which the powder body 50 is provided in the sprue bush 100 can be obtained. However, the present invention is not limited to this, and a hollow region 40 is formed by performing a cutting process on a local region where a metal structure is present, and powder is supplied to the hollow region 40 so that the “hollow body having the powder body 50 is Part 40" can also be obtained.

[(2) Low heat transfer part: Porous material]
In the sprue bush 100 according to the embodiment of the present invention, the low heat transfer portion 30 may be made of a porous material 60, as shown in FIG. 6, for example. The “porous material” here refers to a porous material having a large number of minute voids (that is, holes). The average size of each void is not particularly limited, but is preferably about 10 nm to 1 mm, more preferably about 20 nm to 500 nm, for example, about 100 nm.

Air is substantially present in the voids of the porous material 60. As described above, since the thermal conductivity of air is smaller than that of the metal material, the cooling heat from the cooling medium in the cooling medium passage 20 is reduced by the porous material 60 in which air is present. That is, the cooling heat is less likely to be transmitted from the cooling medium flow path 20 to the upstream side 10A of the raw material resin flow path 10, and the phenomenon in which the molten raw material resin is cooled and solidified in the upstream side 10A before the downstream side 10B is less likely to occur.

The porous material 60 provided as the low heat transfer part 30 may be obtained by a powder sintering lamination method. When the solidified layer is formed by the powder sinter lamination method, the region made of the porous material 60 can be obtained by controlling the irradiation condition of the light beam. More specifically, by lowering the irradiation energy of the light beam with respect to a part of the region to be the solidified layer, the sintering density of the part can be made relatively small. For example, the sintered density can be 40% to 90%. The region of the solidified layer having such a low sintering density can be used as the region of the porous material 60. As an example, the sintering density can be set to about 70 to 80% by lowering the irradiation energy of the light beam to about ² to 3 J/mm ² . (1) In addition to lowering the irradiation energy of the light beam, (2) increasing the scanning speed of the light beam, (3) expanding the scanning pitch of the light beam, and (4) increasing the converging diameter of the light beam. The area of the porous material 60 can also be formed by things or the like.

The first and second specific modes described above are related to the low heat transfer section provided between the upstream side of the raw material resin flow path and the cooling medium flow path. Also, the "heat transfer to the upstream side of the raw material resin flow path" can be reduced.

Cooling medium flow path: coating layer formation The sprue bush 100 shown in FIG. 7 has a coating layer 70. More specifically, the coating layer 70 is provided on at least a portion 20A of the inner wall surface of the cooling medium flow passage 20. The “coating layer” here refers to a layer that covers at least a part of the inner wall surface of the cooling medium channel 20. “At least a part of the inner wall surface 20A of the cooling medium flow path 20” particularly refers to the inner wall surface of the raw material resin flow path 10 that is proximal to the upstream side 10A as shown in FIG. The coating layer 70 is preferably a layer of low thermal conductivity material. The low thermal conductivity material used for the coating layer 70 is not particularly limited, but examples thereof include epoxy resin and silicone resin.

As shown in FIG. 7, when the coating layer 70 of the low thermal conductivity material is provided on at least a part 20A of the inner wall surface of the cooling medium passage 20, the cooling heat due to the cooling medium in the cooling medium passage 20 is coated. It will be reduced in layer 70. Specifically, because the coating layer 70 is made of a material having a low thermal conductivity, the cooling heat is less likely to be transmitted to the upstream side 10A of the raw material resin passage 10. Therefore, the cooling of the molten raw material resin on the upstream side 10A is more appropriately suppressed, and the phenomenon that the molten raw material resin is cooled and solidified on the upstream side 10A before the downstream side 10B is less likely to occur.

Although the sprue bush according to the embodiment of the present invention has been described above, the present invention is not limited thereto, and various modifications can be made without departing from the scope of the invention defined in the claims. It will be understood that this is done by the vendor.

100 sprue bush 100A local area (local area between upstream side portion of raw material resin flow path and cooling medium flow path)
100B Area other than local area 10 Raw material resin flow path 10A Upstream side of raw material resin flow path 20 Cooling medium flow path 30 Low heat transfer section 40 Hollow part 40a Heat medium flow path 50 Powder body 60 Porous material

Claims (1)

A sprue bush having a raw material resin flow path and a cooling medium flow path provided around the raw material resin flow path,
In a local region between the upstream side portion of the raw material resin flow channel and the cooling medium flow channel, a low heat transfer portion that provides relatively smaller heat transfer than a region other than the local region is provided, and A sprue bush, wherein the low heat transfer portion is provided inside the sprue bush so as not to be exposed to the surface of the sprue bush and the surface on which the raw material resin flow path is formed .

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