KR20210061511A - Method For Manufacturing Shape-Customized Hollow Product Using Blow Molding - Google Patents

Abstract

The present invention relates to a method for manufacturing a hollow product having a shape corresponding to the shape of a contact object, and specifically, to a method for manufacturing a hollow product in which a hollow is formed by using a mold unit including a first mold and a second mold for closing and opening together with the first mold, which includes the steps of: positioning a predetermined object in a first cavity of the first mold; positioning a molding material between a second cavity of the second mold and the object; blow molding by injecting a fluid into the molding material after closing the mold unit; and separating a blow-molded hollow product from the mold unit after opening the mold unit.

Description

Method For Manufacturing Shape-Customized Hollow Product Using Blow Molding}

The present invention relates to a method of manufacturing a hollow product having a hollow therein, and more particularly, to a method of manufacturing a hollow product having a shape corresponding to the shape of a contact object.

In general, in order to form a hollow inside a product made of metal or resin, various casting methods and injection methods are used. This hollow product manufacturing method is a method of forming a product by placing a long tube with a space therein on a mold for product manufacturing, and then supplying the molten metal into the mold. At this time, the inner space of the long tube forms the hollow of the molded product. In this case, a support material is filled in the inner space of the long tube to withstand the pressure of the injected molten metal.

Such a hollow product can exhibit a function of cooling the surroundings when cooling water is passed through the hollow, and has been disclosed through the hollow product manufacturing method of Korean Patent Laid-Open Publication No. 10-2017-0118309 in connection with the manufacturing method.

In particular, the hollow product manufactured in the above-described manner does not leak cooling water from the hollow and has a very strong advantage, and is also used as a housing for accommodating a motor or battery requiring cooling.

Meanwhile, in order to further increase the cooling efficiency of the hollow product, cooling is performed while the hollow product is in contact with a specific object. In this case, when the hollow product has a shape corresponding to the surface of the object in contact, that is, it is manufactured by matching the shape, the hollow product can cool the object with higher cooling efficiency.

However, the hollow product manufactured by the above-described method is generally formed in a shape whose surface, in particular, the outer surface corresponds to the inner surface of the cavity of the mold, and most of the hollow products are formed in a shape that does not consider the surface of the object to be cooled.

Therefore, when the object needs to be cooled quickly in contact with the hollow product, a manufacturing method is required so that the hollow product has a formation corresponding to the contact portion of the object.

An object of the present invention is to provide a method of manufacturing a hollow product in which the surface of a hollow product that cools the object by contacting the object is formed in a shape corresponding to a portion in contact with the object, through an embodiment.

In order to solve the above-described problems, the present invention provides a method for manufacturing a hollow product having a hollow inside using a mold part including a first mold and a second mold for mold closing and mold opening. Positioning a predetermined object in the first cavity of one mold; Placing a molding material between the object and the second cavity of the second mold; Blow molding by injecting a fluid into the molding material after mold closing the mold part; It provides a method for manufacturing a hollow product comprising; after opening the mold part, separating the blow-molded hollow product from the mold part.

The second mold may have a core protruding from the second cavity to press the molding material toward the object.

The first cavity may be formed to fit one end of the object.

The second cavity may have an inner circumferential surface in surface contact with the outer circumferential surface of the other end of the object so that the molding material does not count out.

The object may be a stator in which a hollow in which a rotor is accommodated is formed through between both ends, and a coil is wound around a plurality of cores disposed at intervals in the circumferential direction.

The core may be fitted into the hollow when the mold part is combined.

The partition wall may insert the molding material into the stator when the mold is closed.

The second mold and the first mold each have a pair of surfaces that contact and engage with each other when the mold part is closed, and a recess formed in each of the pair of surfaces is formed to form a single auxiliary when closing the mold part. A cavity can be formed.

The second mold and the first mold each have a pair of surfaces that contact and engage with each other when the mold part is closed, and a first groove formed in each of the pair of surfaces is formed to form one recess when the mold part is closed. It is possible to form an auxiliary cavity of.

The first mold is provided with a first auxiliary cavity formed by being recessed into a surface that contacts and couples with the second mold when the mold is closed, and the second mold is in contact with the first mold when the mold is closed. A second auxiliary cavity formed by being recessed in the mating surface may be provided.

The first auxiliary cavity may extend in a radial direction of the first cavity from an outer circumferential surface of the first cavity.

The second auxiliary cavity may extend from an outer circumferential surface of the second cavity in a radial direction of the second cavity.

Each of the pair of surfaces may have a second groove formed therein, so that one through passage part may be formed when the mold part is closed.

In the blow molding step, a fluid injection unit for injecting a fluid is used, and the fluid injection unit may be inserted into the through passage.

The through passage part and the auxiliary cavity may be spaced apart from each other with the partition wall therebetween.

After the separating step, processing a portion corresponding to the auxiliary cavity of the hollow product may further include forming a hole to communicate with the hollow of the hollow product.

The core includes a surface facing the first mold, and a surface of the core facing the first mold may press the molding material toward the stator when the mold is closed.

The surface of the core facing the first mold may be inserted into the hollow of the stator when the mold is closed.

As described above, according to the embodiment of the present invention, the following effects are obtained.

First, according to an embodiment of the present invention, the surface of the hollow product that cools the object by contacting the object is provided in a shape corresponding to the portion in contact with the object.

Second, according to an embodiment of the present invention, it provides the effect of forming the surface of the hollow product in a shape corresponding to the portion in contact with the object in a relatively simple and inexpensive method.

1 is a perspective view showing an example of a hollow product and an object to be cooled according to a method of manufacturing a hollow product according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating an arrangement relationship between a molding material to be manufactured from the hollow product shown in FIG. 1 and a mold of an object to be cooled.
FIG. 3 is a diagram illustrating an example of a method in which the mold shown in FIG. 2 is incorporated and a fluid is introduced to manufacture a hollow product.
4 is a view showing a state in which the molding material shown in FIG. 2 is formed into a hollow product.

The embodiments described below are illustratively shown to aid understanding of the invention, and it should be understood that the present invention may be variously modified and implemented differently from the embodiments described herein. However, in describing the present invention, when it is determined that a detailed description of a related known function or component may unnecessarily obscure the subject matter of the present invention, the detailed description and detailed illustration thereof will be omitted. In addition, the accompanying drawings are not drawn to scale to aid understanding of the invention, but dimensions of some components may be exaggerated.

The first and second terms used in the present application may be used to describe various elements, but the elements should not be limited by terms. The terms are used only for the purpose of distinguishing one component from other components.

In addition, terms used in the present application are only used to describe specific embodiments, and are not intended to limit the scope of the rights. Singular expressions include plural expressions unless the context clearly indicates otherwise. In the present application, terms such as "comprise", "consist of" or "consist of" are intended to designate the presence of features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, one or It is to be understood that no further features or possibilities of the presence or addition of numbers, steps, actions, components, parts, or combinations thereof are excluded in advance.

1 is a perspective view showing an example of a hollow product 100 and an object 200 to be cooled by a method of manufacturing a hollow product 100 according to an embodiment of the present invention.

First, an example of a hollow product 100 and an object 200 to be cooled by the hollow product 100 according to an embodiment of the present invention will be described with reference to FIG. 1. It should be noted that the object 200 described herein is only an example, and the method of manufacturing the hollow product 100 according to an embodiment of the present invention is not limited thereto.

Referring to FIG. 1, the object 200 to be cooled is a stator 200 used in a motor, for example, and the hollow product 100 contacts one end of the stator 200 to cool the stator 200. .

A portion of the stator 200 that the hollow product 100 contacts is one end surface of the stator 200 and has a complex shape and a heat source is collected. Therefore, the stator 200 may be referred to as a typical example of the object 200 that needs to be cooled by contacting the hollow product 100.

The stator 200 forms a motor (not shown) together with a rotor (ROTOR, not shown). The motor generally includes a motor housing (not shown) forming an external appearance, and a stator 200 and a rotor accommodated in the motor housing. The stator 200 may be fixed to the motor housing. The rotor is configured to rotate by electromagnetically interacting with the stator 200. The rotor is generally disposed inside the stator 200.

The stator 200 includes a stator body 210, a stator coil 240, a stator core 220, and a stator slot 230.

The stator body 210 forms the exterior of the stator 200, and a hollow rotor receiving portion 211 for accommodating the rotor is formed in the central portion. The stator body 210 may be formed by stacking press-processed steel plates.

The stator core 220 is arranged around the rotor receiving portion 211 along the circumferential direction of the rotor to form a plurality. The stator core 220 extends radially from the center of the rotor receiving portion 211.

The stator slots 230 are formed between the stator cores 220 arranged at intervals in the circumferential direction, and form a plurality of stator slots. The stator slot 230 accommodates the stator coil 240 as the stator coil 240 is wound around the stator core 220. The stator coils 240 wound around each of the stator cores 220 are spaced apart from each other.

When the motor is running, it can generate high heat. The high heat of the motor may melt the insulating coating of the stator coil 240, leading to damage to the motor. In order to prevent such damage to the motor, the stator 200 is cooled by contacting the stator 200, but it is preferable to increase the area in contact with the stator 200.

1, a hollow product 100 for cooling the stator 200 by contacting one end of the stator 200 is shown. The hollow product 100 includes a channel body 110 in which a flow path is formed so that a fluid such as coolant flows therein, a shape-corresponding part 120 having a shape matching the shape of one end of the stator 200, and a fluid flow in and out. It includes parts 131 and 132.

The channel body 110 is elongated to be formed in an approximately ring shape, but is bent to have a predetermined curvature. The channel body 110 has both ends facing each other while being spaced apart from each other, and a space 133 is formed between both ends. Accordingly, the channel body 110 is formed in an approximately C-shaped alphabet.

A first fluid inlet 131 and a second fluid inlet 132 are provided at both ends of the channel body 110, respectively. Accordingly, when a fluid is injected through any one of the first fluid inlet 131 and the second fluid inlet 132, the fluid flows along the flow path formed inside the channel body 110, and then the first fluid inlet It is discharged through the rest of the 131 and the second fluid inlet 132.

The first fluid inlet 131 and the second fluid inlet 132 are formed to protrude from the channel body 110 and a space is formed to allow fluid to flow therein. This space communicates with the inner flow path of the channel body 110. The protruding directions of the first fluid inlet 131 and the second fluid inlet 132 may be, for example, a radial direction.

The shape-corresponding part 120 is provided on one surface of the channel body 110 and includes a protrusion 120 accommodated in the stator slot 230. One surface of the protrusion 120 and one surface of the channel body 110 located between the protrusion 120 have a shape of a stator coil 240. In addition, a flow path through which cooling water flows is formed in the protrusion 120.

Various methods may be used to manufacture the hollow product 100, and in this specification, a blow molding (molding) method will be described with reference to FIGS. 2 to 4 as an example.

FIG. 2 is a diagram illustrating an arrangement relationship between a molding material 500 to be manufactured from the hollow product 100 shown in FIG. 1 and a mold of the object 200 to be cooled, and FIG. 3 is a mold shown in FIG. It is a view for explaining an example of a method of manufacturing the hollow product 100 by the injection of the fluid, and Figure 4 shows a state in which the molding material 500 shown in FIG. 2 is molded into the hollow product 100 It is a drawing.

The blow molding method is a molding method of making a hollow product 100 with a space formed therein by placing a molding material 500, which is a molding material 500, inside a mold and then blowing a fluid therein. Various materials are used for the molding material 500, and a synthetic resin such as plastic is sometimes used.

Referring to FIG. 2, in this blow molding method, a mold part 10 including a first mold 30, a first mold 30, and a second mold 20 for mold closing and mold opening is used.

The first mold 30 includes a first cavity 31 formed by recessing a surface that is coupled with the second mold 20 and one side of the surface that is coupled with the second mold 20, and a first through passage part 35 ) And, a first auxiliary cavity 34 is provided.

The first cavity 31 is formed so that one end of the stator 200 is fitted. That is, the inner circumferential surface, that is, the inner circumferential surface of the first cavity 31 is in contact with the outer circumferential surface of one end of the stator 200.

In addition, as will be described later, as the first cavity 31 is formed so that the stator 200 is fitted, it serves to fix the stator 200 during blow molding.

The first through passage part 35 communicates the outside of the first cavity 31 and the first mold 30 to each other, and is formed by recessing one side of a surface that is engaged with the second mold 20 described above. The first through passage part 35 together with the second through passage part 21 to be described later forms a through passage part 21 and 31 which is one through hole when the mold part is molded or closed. A fluid injection part 40 to be described later is positioned in the through passages 21 and 31, and a part of the mold material 500 is injected to form the first fluid inlet 131.

The first auxiliary cavity 34 is formed by recessing one side of the surface engaging the second mold 20 described above, and a space formed by being recessed communicates with the first cavity 31. The first auxiliary cavity 34 is spaced apart from the first through passage part 35, and together with the second auxiliary cavity 24 to be described later, when the mold part 10 is molded or closed, the auxiliary cavities 24 and 34, which are one through hole. ) To form. A part of the mold material 500 is injected into the auxiliary cavities 24 and 34 to form a second fluid inlet 132.

The second mold 20 includes a second cavity 22 formed by depression of a surface to which the first mold 30 is coupled, and one side of the surface to be coupled to the first mold 30, and the second cavity 22. A protruding core 23, a second through passage part 21, a second auxiliary cavity 24, and a partition wall 25 are provided.

The second cavity 22 is formed so that one end of the stator 200 and the other end located opposite to the other end of the stator 200 are fitted. That is, the inner circumferential surface of the second cavity 22, that is, the inner circumferential surface of the stator 200 comes into contact with the outer circumferential surface of the other end of the stator 200. Accordingly, the molding material 500 to be described later does not count.

The core 23 protrudes from the second cavity 22 and serves to press the molding material 500 toward the stator 200. In addition, the core 23 is formed to be inserted into the rotor receiving portion 211. In this case, the core 23 is fitted to the rotor receiving portion 211. That is, the outer circumferential surface of the core 23 contacts the inner circumferential surface of the rotor receiving portion 211.

Accordingly, when the molding material 500 is molded and closed after being positioned at the other end of the stator 200, the molding material 500 contacts the coil, but the rotor is accommodated due to the core 23 fitted to the rotor receiving part 211 It does not flow into the part 211 and does not flow out of the second cavity 22 from the other end of the stator 200 due to the other end of the stator 200 fitted into the second cavity 22.

The partition wall 25 is for forming the separation space 133 of the channel body 100, and is formed to substantially cross the space between the inner circumferential surface of the second cavity 22 and the outer circumferential surface of the core 23 in a radial direction. . The partition wall 25 is located between the second through passage part and the second auxiliary cavity 24, and the surface of the partition wall 25 facing the first mold 30 is among the surfaces of the second mold 20. The same surface as the surface that is joined to the first mold 30 may be formed.

The second through passage part 21 communicates the outside of the second mold 20 with the second cavity 22 and is formed by recessing one side of a surface that is coupled to the first mold 30 described above. The second through passage part 21 together with the first through passage part 35 forms a through passage part 21 and 31 which is one through hole when the mold part 10 is molded or closed.

The second auxiliary cavity 24 is formed by recessing one side of the surface engaging the first mold 30 described above, and a space formed by being recessed communicates with the second cavity 22. The second auxiliary cavity 24 is spaced apart from the second through passage part 21, and together with the first auxiliary cavity 34 to be described later, when the mold part 10 is molded and closed, the auxiliary cavities 24 and 34 are one through hole. ) To form.

The mold part 10 is provided with a fluid injection part 40 for injecting a fluid into the mold material 500. The fluid injection unit 40 serves to inject an external fluid into the second cavity 22 through the through passages 21 and 31. Such a fluid injection part 40 is inserted into the through passage portions 21 and 31, so that the molding material 500 is injected into the through passage portions 21 and 31 so that the first fluid inlet portion 131 can be formed. The outer circumferential surface of the fluid injection part 40 is spaced apart from the inner circumferential surfaces of the through passage parts 21 and 31.

When the molding material 500 is positioned in the second cavity 22, the fluid injection unit 40 may inject a fluid into the molding material 500 through the through passages 21 and 31. The fluid injection part 40 may be formed to be longer than the length of the through passage parts 21 and 31, and the fluid may be directly injected into the molding material 500 while being directly inserted into the molding material 500. .

When the mold part 10 is molded and closed, the molding material 500 flows into and is located between the outer circumferential surface of the fluid injection part 40 and the inner circumferential surfaces of the through passages 21 and 31, and the first fluid inlet 131 is Is formed. When the fluid is injected by the fluid injection unit 40, a flow path through which coolant or the like can flow is formed in the molding material 500. Thereafter, when the fluid injection part 40 is removed, the space in which the fluid injection part 40 is located allows the flow path to communicate with the outside of the molded molding material 500.

In order to perform the blow molding method, the mold part 10 is first opened. One end of the stator 200 is fitted into the first cavity 31, and the molding material 500 is positioned between the second cavity 22 and the other end of the stator 200.

At this time, it does not exclude that the molding material 500 is first positioned on the side of the second cavity 22 and then the stator 200 is performed in the order in which one end of the stator 200 is inserted into the first cavity 31.

The molding material 500 may be heated in advance for smooth molding, or may not have a certain shape. Accordingly, the area of the molding material 500 may be larger than the cross-sectional area of the second cavity 22.

3, when the placement of the molding material 500 and the stator 200 between the mold parts 10 is completed, at least one of the first mold 30 and the second mold 20 moves, and the mold The wealth (10) is sentenced to death.

In this case, the molding material 500 is located in a space defined by the core 23, the second cavity 22, and the other end of the stator 200.

The molding material 500 contacts the other end of the stator 200 while being pressed by the inner surfaces of the core 23 and the second cavity 22, and is pushed into the stator slot 230 or the like. Accordingly, a shape corresponding portion 120 having a shape corresponding to the shape of the other end of the stator 200 is formed.

The molding material 500 is pre-adjusted in viscosity and volume so that it flows into the slit of the stator 200 and does not flow down or move to one end of the stator 200.

On the other hand, when the mold part 10 is molded and closed, the molding material 500 having an area larger than the cross-sectional area of the second cavity 22 is cut off to fit the cross-sectional area of the second cavity 22, and part of the through passage part (21, 31) and the auxiliary cavity (24, 34).

In this case, for example, a cutting blade (not shown) inserted into the edge of the first cavity 31 may be continuously provided along the edge of the second cavity 22 at the edge of the second cavity 22. The cutting blade is shaped like a sharp blade.

When the mold is closed, the cutting blade of the second cavity 22 is inserted into the second cavity 22 to smoothly cut the molding material 500.

In addition, the molding material 500 located between the second cavity 22 and the core 23 is pushed to both sides of the partition wall 25 by the partition wall 25. Accordingly, the spaced space 133 is formed.

When the mold is closed and the molding material 500 is cut to fit the second cavity 22, the fluid is then injected into the molding material 500 through the fluid injection unit 40.

When the fluid is injected, a space that can serve as a flow path is formed inside the molding material 500, and in particular, a space is formed inside the protruding portion of the shape-corresponding portion 120.

In this case, a space capable of serving as a flow path by the injected fluid is not formed up to the molding material 500 introduced into the auxiliary cavities 24 and 34.

Referring to FIG. 4, after a predetermined time elapses, a fluid such as air is discharged, and the fluid injection part 40 is removed. When the fluid injection part 40 is removed, the space occupied by the fluid injection part 40 becomes an internal space of the first fluid inlet part. The inner space of the first fluid inlet part communicates the flow path and the outside of the channel body 110 with each other.

After that, the mold part 10 is opened and the hollow product 100 which is a molded product is taken out. Since the taken out hollow product 100 has the second fluid inlet 132 blocked, a hole for communicating the flow path and the outside must be formed through a separate process.

Accordingly, the hollow product 100 is completed, and the completed hollow product 100 has a flow path formed therein, and a first fluid inlet 131 and a second fluid inlet 132 are respectively provided at both ends of the flow path. It is formed and communicates with the flow path.

For example, when a fluid such as coolant is injected into the first fluid inlet 131, the fluid passes through the first fluid inlet 131 and passes through the flow path of the channel body 110 to the second fluid inlet 132. Is discharged through. Since the flow path of the channel body 110 is formed up to the inside of the protruding part of the shape-corresponding part 120, when the object to be cooled is the stator 200, it can be cooled directly to a certain depth of the stator slot 230. .

As described above, although the present invention has been described by limited embodiments and drawings, the present invention is not limited thereto, and the technical spirit and the following by those of ordinary skill in the technical field to which the present invention pertains. It goes without saying that various modifications and variations are possible within the equal scope of the claims to be described in.

10: mold part
100: hollow product
200: object
500: molding material

Claims (24)

In the method of manufacturing a hollow product in which a hollow is formed therein by using a mold part including a first mold and a second mold for mold closing and mold opening with the first mold,
Positioning a predetermined object in the first cavity of the first mold;
Placing a molding material between the object and the second cavity of the second mold;
Blow molding by injecting a fluid into the molding material after mold closing the mold part;
After opening the mold part, the step of separating the blow-molded hollow product from the mold part; Method for manufacturing a hollow product comprising a. The method of claim 1,
The second mold is
A method of manufacturing a hollow product, characterized in that a core protruding from the second cavity is provided to press the molding material toward the object. The method of claim 1,
The first cavity is
Method for manufacturing a hollow product, characterized in that formed so as to fit one end of the object. The method of claim 1,
The second cavity is
A method of manufacturing a hollow product, characterized in that an inner circumferential surface in contact with the outer circumferential surface of the other end of the object is provided so that the molding material does not count out. The method of claim 2,
The object is
A method of manufacturing a hollow product, characterized in that it is a stator in which a hollow penetrating between both ends is formed so that the rotor is accommodated, and a coil is wound on a plurality of cores arranged at intervals in the circumferential direction. The method of claim 5,
The method of manufacturing a hollow product, characterized in that the core is fitted into the hollow of the object when the mold is combined. The method of claim 5,
The stator, characterized in that the outer circumferential surface is in contact with the inner circumferential surface of the first cavity
Method of manufacturing hollow products. The method of claim 5,
The method of manufacturing a hollow product, characterized in that the stator is forcibly fitted into the first cavity. The method of claim 5,
The method of manufacturing a hollow product, wherein the stator has an outer circumferential surface fitted to the inner circumferential surface of the second cavity. The method of claim 5,
The second mold is
A space between the inner circumferential surface of the second cavity and the outer circumferential surface of the core is formed in a ring shape, and a partition wall extending in the radial direction of the core is provided to partition the space between the inner circumferential surface of the second cavity and the outer circumferential surface of the core. Method for manufacturing a hollow product, characterized in that the. The method of claim 10,
The bulkhead is
Method for manufacturing a hollow product, characterized in that one end is in contact with the outer circumferential surface of the core and the other end is in contact with the inner circumferential surface of the second cavity. The method of claim 11,
The partition wall includes a surface facing the first mold,
The method of manufacturing a hollow product, characterized in that the side of the partition wall facing the first mold presses one end of the stator when the mold part is closed. The method of claim 11,
The partition wall is a method of manufacturing a hollow product, characterized in that the molding material is inserted into the stator when the mold is closed. The method of claim 10,
The second mold and the first mold form a pair of each provided with surfaces that contact and couple with each other when the mold part is closed,
A method of manufacturing a hollow product, characterized in that a groove is formed in each of the pair of surfaces to form a single auxiliary cavity when the mold part is closed. The method of claim 10,
The second mold and the first mold form a pair of each provided with surfaces that contact and couple with each other when the mold part is closed,
A method of manufacturing a hollow product, characterized in that a first groove is formed in each of the pair of faces to form one auxiliary cavity when the mold part is closed. The method of claim 15,
The first mold is provided with a first auxiliary cavity formed by being recessed into a surface that contacts and couples with the second mold when the mold part is closed,
The method of manufacturing a hollow product, characterized in that when the second mold is closed, a second auxiliary cavity is formed by being recessed into a surface that contacts and couples with the first mold. The method of claim 16,
The method of manufacturing a hollow product, wherein the first auxiliary cavity extends in a radial direction of the first cavity from an outer circumferential surface of the first cavity. The method of claim 16,
The second auxiliary cavity is a method of manufacturing a hollow product, characterized in that extending in the radial direction of the second cavity from the outer circumferential surface of the second cavity. The method of claim 15,
A method of manufacturing a hollow product, characterized in that a second groove is formed in each of the pair of faces to form one through passage part when the mold part is closed. The method of claim 19,
In the blow molding step, a fluid injection unit for injecting fluid is used,
The method of manufacturing a hollow product, characterized in that the fluid injection part is inserted into the through passage. The method of claim 19,
The method of manufacturing a hollow product, characterized in that the through passage part and the auxiliary cavity are spaced apart from each other with the partition wall therebetween. The method of claim 19,
After the separating step, processing a portion corresponding to the auxiliary cavity of the hollow product to form a hole to communicate with the hollow of the hollow product. The method of claim 5,
The core includes a surface facing the first mold,
The method of manufacturing a hollow product, characterized in that the surface of the core facing the first mold presses the molding material toward the stator when the mold is closed. The method of claim 23,
The method of manufacturing a hollow product, characterized in that the surface of the core facing the first mold is inserted into the hollow of the stator when the mold is closed.

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