WO2024172041A1

WO2024172041A1 - Three-dimensional modeling method, method for manufacturing three-dimensional model, and three-dimensional model

Info

Publication number: WO2024172041A1
Application number: PCT/JP2024/004885
Authority: WO
Inventors: 諭圓崎; 雄一郎津田; 尊神村
Original assignee: 東レエンジニアリング株式会社
Priority date: 2023-02-17
Filing date: 2024-02-13
Publication date: 2024-08-22
Also published as: JP2024117651A

Abstract

Provided is a three-dimensional modeling method for a core-shell system, in which, in a step for curing a core material, molding defects caused by gases emitted from the core material can be prevented, and deformation of the shell can be suppressed. Specifically, this three-dimensional modeling method includes: a shell modeling step for using a shell material to model a shell that defines the external shape of a three-dimensional model; a core material filling step for filling a liquid-phase core material into a core section, which is a section enclosed by the inner surface of the shell; and a core material curing step for curing the core material inside the core section. The method also includes a core section sealing step for sealing an opening in the core section by leaving an uncured region of the shell material on the upper surface of the core material filled into the core section. The core material curing step is performed after the core section sealing step.

Description

Three-dimensional modeling method, manufacturing method for three-dimensional model, and three-dimensional model

The present invention relates to a three-dimensional modeling method, a method for manufacturing a three-dimensional object, and a three-dimensional model, and more specifically to a three-dimensional modeling method for manufacturing a three-dimensional object using additive manufacturing techniques such as 3D printing, a method for manufacturing a three-dimensional object, and a three-dimensional model.

The term 3D printer is widely used as the name for manufacturing equipment that uses 3D printing technology. A 3D printer is a three-dimensional modeling device that uses a computer to calculate the cross-sectional shape of an object based on three-dimensional CAD data, divides the object into thin, round cross-sectional components, forms these components using various methods, and stacks them to create the desired object. Internationally, 3D printing technology is often used as a synonym for Additive Manufacturing Technology, and the Japanese translation is additive manufacturing technology.

In recent years, metal 3D printers and composite 3D printers have been attracting attention as they are now required to have rigidity and strength in addition to appearance for the purpose of evaluating the actual product before mass production.

The applicant has proposed a three-dimensional modeling method described in the following Patent Document 1 as one of the technologies related to the additive manufacturing technology described above. The three-dimensional modeling method described in Patent Document 1 is characterized in that after shell modeling and core material filling are repeated multiple times in a modeling tank, the core material is cured all at once by irradiating it with active energy rays or applying thermal energy. This three-dimensional modeling method makes it possible to create a three-dimensional object in which there is no layer interface in the part modeled with the core material, in other words, which has no directional rigidity or strength.

When obtaining a three-dimensional object using the three-dimensional modeling method described in Patent Document 1 above (hereinafter, this method is also referred to as the core-shell method), the three-dimensional object is generally defined as a combination of the shell that forms the outer layer and the hardened core material inside the shell.
[Problem to be solved by the invention]

On the other hand, when obtaining a three-dimensional object using this core-shell method, if importance is placed on the integrity of the three-dimensional object or the strength of the shell is an issue, it may be necessary to separate at least a portion of the shell from the hardened core material to produce a three-dimensional object that is primarily made of the hardened core material.

In this case, since the shell and the hardened core material are in close contact with each other, a step of applying an external force to the shell by cutting or the like is required to separate the shell from the core material.
In the above-mentioned core-shell method, when the core material in a liquid phase state is hardened all at once, in order to harden the core material without distortion, it is desirable that the shell has a sufficient thickness so that the shell does not deform when the core material hardens.

On the other hand, the thicker the shell, the more difficult it becomes to separate the shell from the core material after hardening. Therefore, if it is necessary to separate the shell from the core material after hardening, it is desirable for the shell to be thin.
However, when the thickness of the shell is reduced, the shell softens due to the application of thermal energy in the process of hardening the core material, and the weight of the core material before hardening is also added, causing the shape of the shell to deform, which in turn causes the shape of the core material after hardening to also deform.

An example of a phenomenon that causes the above problem will be described with reference to FIGS.
6 and 7 are schematic diagrams showing the states before and after a conventional process of hardening the core materials all at once in the core-shell method.
Figure 6(a) is a plan view showing the state of the core material before hardening when the shell is thick, (b) is a cross-sectional view taken along line b-b in (a), (c) is a plan view showing the state of the core material after hardening when the shell is thick, and (d) is a cross-sectional view taken along line d-d in (c).
Figure 7(a) is a plan view showing the state of the core material before hardening when the shell is thin, (b) is a cross-sectional view taken along line b-b in (a), (c) is a plan view showing the state of the core material after hardening when the shell is thin, and (d) is a cross-sectional view taken along line d-d in (c).

In the example shown in Figures 6 and 7, before the core material hardens, the shell 40 has a box shape with a bottom that opens upward, and the core portion 50, which is the part surrounded by the shell 40, is filled with the core material 60, and the shell material 2, which is a liquid phase material, remains in an unhardened state on the upper surface of the core material 60.
As shown in FIG. 6, when the shell 40 is thick, there is almost no deformation of the shell 40 and the core portion 50 before and after the core material hardens, and the hardened core material 60a is in a form in which the core material 60 has hardened with almost no distortion.

On the other hand, as shown in Figure 7, when the thickness of the shell 40 is thin, after the core material hardens as shown in Figures 7(c) and (d), the outer peripheral surface of the shell 40 in the longitudinal direction becomes slightly bulged, and as shown in the cross-sectional view of Figure 7(d), the upper part of the shell 40 deforms into a wider shape, and accordingly, the core portion 50 also deforms, resulting in a distorted shape of the hardened core material 60a.
If the thickness of the shell 40 is made thin in this manner, the shell 40 may soften due to heat during the process of thermally hardening the core material 60, and the weight of the unhardened core material 60 may be applied to the shell 40, causing deformation of the shapes of the shell 40 and the core portion 50, resulting in a decrease in the dimensional accuracy of the hardened core material 60a.

As a countermeasure against such a phenomenon, even if the thickness of the shell 40 is reduced, the following method shown in FIG. 8 can be considered as an example of a method for suppressing deformation of the shell 40 during the hardening process of the core material 60.
As shown in Fig. 8(a), after the step of filling the core portion 50 with the core material 60 is completed, the uncured shell material 2 remaining on the upper surface of the core material 60 is irradiated with active energy rays. Then, as shown in Fig. 8(b), all of the uncured shell material 2 is cured, and the upper surface of the core material 60 is sealed with the shell 40. After that, a step of applying thermal energy to cure the core material 60 is performed.

However, in the method shown in FIG. 8, when gas (air) contained and dissolved within the core material 60 is generated as bubbles from the core material 60 by the application of thermal energy in the process of hardening the core material 60, the bubbles may accumulate at the interface with the shell 40, causing voids 60b due to the bubbles, as shown in FIG. 8(c). If the core material 60 is hardened with the voids 60b remaining, depressions or gaps due to the voids 60b will be formed on the upper surface of the hardened core material 60a, raising the issue of concern that molding defects in the hardened core material 60a may occur.

JP 2019-136923 A

Means for solving the problem and their effects

The present invention has been made in consideration of the above problems, and aims to provide a three-dimensional modeling method, a manufacturing method for a three-dimensional object, and a three-dimensional object that can prevent molding defects in the core material caused by gas generated from the core material during the process of hardening the core material, and can suppress deformation of the core portion in the so-called core-shell type three-dimensional modeling method.

In order to achieve the above object, a three-dimensional object forming method (1) according to the present invention comprises:
a shell forming process for forming a shell that defines an outer shape of a three-dimensional object using a shell material;
a core material filling step of filling a core portion, which is a portion surrounded by an inner surface of the shell, with a core material, which is a liquid phase material;
and hardening the core material in the core portion,
a core portion sealing step of sealing an opening of the core portion while leaving an uncured region of the shell material on an upper surface of the core material filled in the core portion;
The method is characterized in that the core material hardening step is carried out after the core sealing step.

According to the above-mentioned three-dimensional modeling method (1), the core portion sealing process seals the opening of the core portion so as to leave an unhardened area of the shell material on the upper surface of the core material filled in the core portion, and the core material hardening process is carried out after the core portion sealing process.
Therefore, when gas is generated from the core material in the core material hardening step, the gas is expelled into the unhardened region of the shell material that exists in a liquid state on the upper surface of the core material, and it is possible to prevent molding defects such as void defects caused by the gas in the hardened core material. In addition, since the core material hardening step is performed with the opening of the core portion sealed, deformation of the core portion in the core material hardening step can also be suppressed.

The present invention also provides a three-dimensional object forming method (2), comprising the steps of:
The core sealing step includes:
The opening of the core portion is sealed by curing only the upper layer portion of the uncured region of the shell material.

According to the three-dimensional modeling method (2), in the core sealing step, the opening of the core can be sealed by curing only the upper layer of the uncured region of the shell material while leaving the uncured region of the shell material on the upper surface of the core material.

The present invention also provides a three-dimensional object fabrication method (3), comprising the steps of:
the shell material contains a resin that is cured by irradiation with active energy rays,
In the core sealing step, the active energy rays are irradiated onto an upper surface of the uncured region of the shell material to cure only the upper layer portion of the uncured region of the shell material,
the core material comprises a thermosetting resin;
The core material hardening step is characterized in that thermal energy is applied to the core material to thermally harden the core material.

According to the above-mentioned three-dimensional modeling method (3), in the core portion sealing process, the active energy rays are irradiated onto the upper surface of the uncured region of the shell material to harden only the upper layer of the uncured region of the shell material, so that the process of sealing the opening of the core portion while leaving the uncured region of the shell material on the upper surface of the core material can be carried out efficiently.
Furthermore, since the core material is composed of a thermosetting resin, the core material filling process can be easily carried out under normal temperature and pressure conditions, and in the core material hardening process, gas generated from the core material can be expelled into the unhardened area of the shell material, while the entire core material can be efficiently hardened into an integrated state.

Further, the present invention provides a three-dimensional object fabrication method (4) in any one of the three-dimensional object fabrication methods (1) to (3),
The size of the uncured region of the shell material is adjusted according to the amount of the core material filled in the core portion.

According to the above three-dimensional modeling method (4), even if the amount of gas generated from the core material in the core material hardening process increases in accordance with an increase in the amount of the core material filled in the core section, the size (volume) of the unhardened area of the shell material is adjusted to increase in accordance with an increase in the amount of the core material filled in the core section, so that the gas generated in the core material hardening process can be more reliably removed into the unhardened area of the shell material.

Further, the present invention provides a three-dimensional object forming method (5) in any one of the above three-dimensional object forming methods (1) to (4),
After the core material hardening step,
The method includes a separation step of separating at least a portion of the shell from the hardened core material to obtain a three-dimensional object having a shape following the shape of the core portion and made mainly of the core material.

The three-dimensional modeling method (5) includes the separation step after the core material hardening step, so that a three-dimensional model consisting mainly of the hardened core material can be obtained without molding defects such as voids caused by the gas and with reduced deformation.

The method for producing a three-dimensional object according to the present invention is characterized in that the three-dimensional object is produced using the three-dimensional object production method (5) described above.

The method for manufacturing a three-dimensional object described above provides the same effects as those obtained by the three-dimensional modeling method (5) described above when manufacturing the three-dimensional object, and can improve the accuracy of the dimensions and shape of the three-dimensional object mainly made of the core material after hardening.

The three-dimensional object (1) according to the present invention is a three-dimensional object having a structure including a shell forming an outer shell layer and a hardened core material in a core portion surrounded by an inner surface of the shell,
The shell is formed by hardening a shell material,
an uncured region of the shell material on an upper surface of the cured core material;
The opening of the core portion is sealed.
A three-dimensional object (2) according to the present invention is the three-dimensional object (1) described above, characterized in that an opening of the core portion is sealed with the shell.

The three-dimensional object (1) has an uncured region of the shell material on the upper surface of the hardened core material, and the opening of the core portion is sealed. The three-dimensional object (2) has an opening of the core portion sealed with the shell. The three-dimensional objects (1) and (2) have a form in which the uncured shell material is enclosed on the upper surface of the hardened core material, so that it is possible to provide an object with fewer molding defects in the hardened core material and reduced deformation of the core portion.

1 is a schematic diagram showing a configuration example of a 3D object modeling system used in a 3D object modeling method according to an embodiment of the present invention; 5A and 5B are diagrams for explaining an example of a three-dimensional object forming method according to an embodiment, in which FIG. 5A is a diagram for explaining a shell forming step, and FIG. 5B is a diagram for explaining a core material filling step. 5A and 5B are cross-sectional views illustrating an example of a core portion sealing step in the three-dimensional object manufacturing method according to the embodiment, in which FIG. 5A is a cross-sectional view illustrating a state of the three-dimensional object before sealing the core portion and FIG. 5B is a cross-sectional view illustrating a state of the three-dimensional object after sealing the core portion. 5A and 5B are cross-sectional views illustrating an example of a core material hardening step in the three-dimensional object fabrication method according to the embodiment, in which FIG. 5A is a cross-sectional view illustrating a state of the three-dimensional object before the core material is hardened, and FIG. 5B is a cross-sectional view illustrating a state of the three-dimensional object after the core material is hardened. 5A and 5B are cross-sectional views for explaining an example of a separation step in the three-dimensional object fabrication method according to the embodiment, in which FIG. 5A is a cross-sectional view showing a state before shell separation and FIG. 5B is a cross-sectional view showing a state after shell separation. 1A and 1B are diagrams showing an example of the state of a three-dimensional object before and after a conventional process of hardening a core material in a core-shell method, in which (a) is a plan view showing the state before the core material hardens when the shell is thick, (b) is a cross-sectional view taken along line b-b in (a), (c) is a plan view showing the state after the core material hardens when the shell is thick, and (d) is a cross-sectional view taken along line d-d in (c). FIG. 13 is a diagram showing an example of the state of a three-dimensional object before and after a conventional process of hardening a core material in a core-shell method, in which (a) is a plan view showing the state before the core material hardens when the shell is thin, (b) is a cross-sectional view taken along line b-b in (a), (c) is a plan view showing the state after the core material hardens when the shell is thin, and (d) is a cross-sectional view taken along line d-d in (c). 1A to 1C are diagrams showing an example of a conventional method for suppressing deformation of a core portion in a process of hardening a core material.

Below, the three-dimensional modeling method, the manufacturing method of a three-dimensional object, and the three-dimensional object according to the present invention will be described with reference to the drawings. Note that the shapes of the shell and core parts shown in the drawings are depicted diagrammatically so that the gist of the present invention can be easily understood, and the present invention is not limited to these shapes.

An example of the configuration of a three-dimensional object modeling system used in a three-dimensional object modeling method according to an embodiment will be described with reference to FIG.
The three-dimensional object modeling system 100 includes a three-dimensional object modeling apparatus 10 , an ultraviolet ray irradiation apparatus 20 , and a thermal curing means 30 .
The three-dimensional modeling device 10 is used in the shell modeling process and the core material filling process, and has the function of a composite 3D printer. Its main components are a modeling tank 11 in which modeling takes place, a laser optical system 12, and a core material supply system 13.

In the modeling tank 11, for example, a photocurable resin, which is a liquid phase material, is stored as the shell material 2, and the liquid level position can be maintained and adjusted at a predetermined position by a photocurable resin adjustment system (not shown). For the shell material 2, for example, known ultraviolet curable resins such as epoxy and acrylic resins can be used. In addition, a modeling table 15 is provided in the modeling tank 11. The modeling table 15 is for supporting the object being modeled, and can be moved (raised and lowered) and set to any position in the z-axis direction in the figure by a drive mechanism (not shown).

The laser optical system 12 includes an ultraviolet laser light source 12a and a scanning optical system 12b. Ultraviolet laser light 12c is emitted from the ultraviolet laser light source 12a, and the emitted ultraviolet laser light 12c can be caused to scan a predetermined range on the liquid surface of the shell material 2 (i.e., the xy plane) by driving the scanning optical system 12b.

The shell material 2 is cured to a predetermined depth from the liquid surface by irradiation with ultraviolet laser light 12c, which is a type of active energy ray, as shown by the cured ultraviolet cured resin layer 3 in Figure 1. This curing depth can be adjusted to a certain extent by adjusting the output of the ultraviolet laser light source 12a, and is adjusted to a range of, for example, about 0.1 mm to 0.4 mm.

Therefore, by positioning the top surface of the modeling table 15 at a depth that is a predetermined curing depth below the liquid surface of the shell material 2 and irradiating an arbitrary position on the liquid surface of the shell material 2 with ultraviolet laser light 12c, a cured ultraviolet cured resin layer 3 of any area is formed on the modeling table 15. Then, after the cured ultraviolet cured resin layer 3 is formed on the modeling table 15, the modeling table 15 is lowered by the curing depth and an arbitrary position on the liquid surface of the shell material 2 is irradiated with ultraviolet laser light 12c, so that a cured ultraviolet cured resin layer 3 is layered on top of the cured ultraviolet cured resin layer 3.

Then, by repeatedly lowering the modeling table 15 and irradiating the liquid surface of the shell material 2 with ultraviolet laser light 12c, the layering of the cured ultraviolet-cured resin layer 3 progresses, and it is possible to obtain a cured ultraviolet-cured resin layer 3 having a three-dimensional shape.
In this embodiment, the object thus shaped is called the shell 4 (see FIG. 2). The shell 4 functions as an outer shell layer for filling the core material 6, and the part surrounded by the inner surface of the shell 4 and having a bottom surface is called the core portion 5 (see FIG. 2).

The core material supply system 13 supplies the core material 6 from the core material tank 13a, which stores the core material 6 inside, by pump 13b, sending it through

piping systems

13c and 13d in sequence, and exhales the core material 6 from the tip of the nozzle 14. The nozzle 14 can be moved and fixed in each of the x, y and z directions in the figure by a nozzle movement mechanism (not shown). For this reason, the piping system 13d is constructed with a flexible structure and material so that it can follow the movement of the nozzle 14.

The core material 6 is composed of a composite material in which a reinforcing material is uniformly dispersed in a thermosetting resin, which is a known liquid phase material such as an epoxy or acrylic resin. The reinforcing material may be, for example, a fibrous reinforcing material containing at least one of carbon fiber, glass fiber, and aramid fiber, or may be an inorganic material powder such as silica. The core material 6 has a higher specific gravity than the shell material 2. The viscosity of the core material 6 is preferably at least twice as high as that of the shell material 2. The shell 4 has a physical property of a glass transition temperature Tgs, which is lower than the heat curing temperature Tpc of the core material 6.

The ultraviolet irradiation device 20 is used in the core sealing process, and is configured to include one or more ultraviolet irradiators 21 that irradiate ultraviolet light, which is one type of active energy ray. The target of ultraviolet irradiation here is the shell 4 (see FIG. 3(a)) that has been removed from the molding tank 11, has the core portion 5 filled with the core material 6, and has an uncured area 2a of the shell material 2 present on the upper surface of the core material 6.

The ultraviolet irradiation device 20 has a function capable of irradiating ultraviolet rays onto, for example, the opening of the shell 4, i.e., the entire upper surface of the core portion 5. The ultraviolet irradiator 21 adjusts the output (intensity) of the ultraviolet rays and the irradiation time, making it possible to harden only a predetermined depth (for example, about 1 to 2 mm) from the top surface of the unhardened area 2a of the shell material 2 present on the top surface of the core material 6 filled in the core portion 5 of the shell 4.

The heat curing means 30 is used in the core material curing process after the core sealing process, and is composed of a heating furnace having a chamber capable of sealing the heating target. The heating target here is the shell 4 (see FIG. 4(a)) after being treated by the ultraviolet irradiation device 20. The heat curing means 30 is capable of raising and lowering the temperature inside the heating furnace to a temperature higher than the heat curing temperature Tpc of the core material 6, and is capable of curing the core material 6 all at once. In this embodiment, this hardened core material 6 is called hardened core material 6a (see FIG. 4(b)).

Next, an example of a three-dimensional object fabrication method according to the embodiment will be described with reference to FIGS.
The three-dimensional object fabrication method according to the embodiment includes a shell fabrication step, a core material filling step, a core sealing step, a core material hardening step, and a separation step. Note that the separation step is not essential and may be performed as necessary.

In the three-dimensional object fabrication method according to the embodiment, first, a process of fabricating the shell 4 and a process of filling the core material 6 into the fabricated shell 4 are performed by the three-dimensional object fabrication apparatus 10 .
Specifically, first, as shown in Fig. 2(a), with the nozzle 14 retracted from the irradiation range of the ultraviolet laser light 12c, the ultraviolet laser light 12c is irradiated to any position on the liquid surface of the shell material 2 on the modeling table 15, and the modeling table 15 is lowered alternately by an amount corresponding to the curing depth. Through this operation, a shell 4 having a core portion 5 of a desired shape is formed. The process of forming the shell 4, which defines the outer shape of the three-dimensional object, using the shell material 2 as described above is called the shell modeling process.

The shell 4 shown in FIG. 2 is shaped like a bottomed box with an opening on the top surface. The thickness of the shell 4 is not particularly limited, but if a separation process is to be performed later, it is preferable to form the shell 4 thin, for example, to about 1 mm to 3 mm.

After the shell molding process is completed, the nozzle 14 moves into the core portion 5 formed in the shell 4 as shown in FIG. 2(b), and the core material 6 is ejected from the nozzle 14 into the core portion 5, thereby filling the core portion 5 with the core material 6. The process of filling the core portion 5, which is surrounded by the inner surface of the shell 4, with the core material 6 as described above is called the core material filling process.

In this embodiment, the core material filling step is performed with the shell 4 immersed in the shell material 2 in the forming tank 11, and before the core material 6 is filled, the shell material 2 is present in the core portion 5 as shown in FIG. 2(a). Then, as the core material 6, which has a larger specific gravity than the shell material 2, is filled into the core portion 5, the shell material 2 in the core portion 5 is pushed up, and as shown in FIG. 2(b), the shell material 2 is pushed out of the shell 4 through the opening of the core portion 5, and the shell material 2 is replaced by the core material 6.

The above shell forming process and core material filling process may be performed alternately multiple times. That is, the shell 4 may be formed to a predetermined height, the core portion 5 formed by the shell 4 may be filled with the core material 6, the shell 4 may be expanded, and the newly formed core portion 5 by the expanded shell 4 may be filled with the core material 6. By dividing the formation of the shell 4 into multiple steps in this way, it is possible to fill every corner of the core portion 5 with the core material 6 by filling it in stages, especially when the core portion 5 has a complex shape (e.g., narrow, thin, thin, etc.).

Then, the core material filling process is completed when the shell material 2 remains on the top surface of the core material 6 filled in the core portion 5, that is, when a layer consisting of the unhardened area 2a of the shell material 2 is formed as shown in FIG. 2(b). Note that the above shell molding process and core material filling process can be carried out in a normal room temperature (e.g., 20°C to 30°C) environment.

The size (volume) of the unhardened region 2a of the shell material 2 is adjusted according to the amount of core material 6 filled in the core portion 5. For example, as the amount of core material 6 filled in the core portion 5 increases, the amount of gas generated from the core material 6 during the core material hardening process tends to increase. Therefore, in order to ensure that the gas generated from the core material 6 is removed into the unhardened region 2a of the shell material 2, the size (volume) of the unhardened region 2a of the shell material 2 is adjusted to increase as the amount of core material 6 filled in the core portion 5 increases. Therefore, the core portion 5 formed by the shell 4 has a shape that takes into consideration the amount of core material 6 filled and the size of the unhardened region 2a of the shell material 2 required to remove the gas generated from the core material 6.

Once the shell molding process and core material filling process are completed, the molding table 15 in the molding tank 11 is then raised above the liquid level of the shell material 2, and the shell 4 filled with the core material 6 is removed from the molding table 15, and the process proceeds to the next core sealing process.

The core sealing step is a step of sealing the opening of the core portion 5 so as to leave an uncured region 2 a of the shell material 2 on the upper surface of the core material 6 filled in the core portion 5 .
3A, the shell 4 removed from the modeling table 15 is placed under the ultraviolet irradiator 21 of the ultraviolet irradiation device 20. The shell 4 removed from the modeling table 15 has the core portion 5 filled with the core material 6 and has a layer made of the uncured region 2a of the shell material 2 on the upper surface of the core material 6.

Then, ultraviolet light is applied to the top surface of the uncured region 2a of the shell material 2 using an ultraviolet irradiator 21, and as shown in FIG. 3(b), only the upper layer 2b of the uncured region 2a of the shell material 2 is cured to form a sealing portion 4a. The depth of the upper layer 2b to be cured can be adjusted by adjusting the output (intensity) of the ultraviolet light from the ultraviolet irradiator 21 and the irradiation time, and can be adjusted to a depth of, for example, about 1 mm to 2 mm.

By using an ultraviolet irradiation device 20 to harden only the upper layer 2b of the unhardened region 2a of the shell material 2, it is possible to form a sealing portion 4a that seals the opening of the core portion 5 while leaving the unhardened region 2a of the shell material 2 on the upper surface of the core material 6.
Then, when the core sealing step is completed, the shell 4 with the sealing portion 4a formed therein is removed from the ultraviolet irradiating device 20, and the process proceeds to the next core material hardening step.

In the core material hardening process, as shown in FIG. 4(a), the shell 4 having an unhardened area 2a of the shell material 2 on the upper surface of the core material 6 in the core portion 5 and a sealing portion 4a formed on the upper surface of the unhardened area 2a is placed into a heat hardening means 30, and the heat hardening process for hardening the core material 6 in the core portion 5 is started.
That is, the shell 4 is placed in the heat curing means 30, and the temperature inside the heat curing means 30 is raised to a temperature higher than the heat curing temperature Tpc of the core material 6, whereby the entire shaped object including the shell 4 and the core material 6 is heated, and the hardening of the core material 6 begins and progresses. After a predetermined time has elapsed, the hardening of the entire core material 6 is completed, and a hardened core material 6a is formed in the core portion 5, as shown in FIG. 4(b).

In the core material hardening step, when the core material 6, which is a liquid phase material, is hardened by heating, gas present and dissolved in the core material 6 may be generated as bubbles 6b.
In this embodiment, the shell 4 fed into the heat curing means 30 has the uncured region 2a of the shell material 2 on the upper surface of the core material 6 in the core portion 5, so that even if air bubbles 6b are generated in the core material 6, the air bubbles 6b in the core material 6 move (rise) from the core material 6 into the uncured region 2a of the shell material 2 and accumulate at the boundary between the uncured region 2a and the sealing portion 4a. In other words, the air bubbles 6b are eliminated from the core material 6.

In addition, even if the shell 4 is heated to a temperature equal to or higher than the glass transition temperature Tgs of the shell 4 during the core material hardening process and becomes soft, the sealing portion 4a that is integrated with the shell 4 is formed on the upper surface of the unhardened area 2a of the shell material 2, so the sealing portion 4a can prevent the sidewall of the shell 4 from being unable to withstand the weight of the core material 6 and becoming deformed.

In order to harden the entire core material 6 filled in the core portion 5, it is preferable to use a material containing a thermosetting resin as the core material 6 as in this embodiment, and to thermally harden the core material 6 by applying thermal energy in the core material hardening process.

After the core material hardening process is completed, the shell 4 (shell 4 with hardened core material 6a formed in the core portion 5) is removed from the heat hardening means 30 and proceeds to the next separation process.

This separation process is a process for separating at least a portion of the shell 4 from the hardened core material 6a. As shown in FIG. 5(a), for example, a tool 31 such as a cutting tool is used to separate the unnecessary sealing portion 4a and shell 4 from the hardened core material 6a, thereby obtaining a three-dimensional object 1 made of the hardened core material 6a having a shape following the shape of the core portion 5, as shown in FIG. 5(b).

In the example shown in FIG. 5(b), all of the shells 4 are separated to obtain a three-dimensional object 1 consisting only of the hardened core material 6a, but this is not limited thereto. A portion of the shell 4 may be left, and the combination of this portion of the shell 4 and the hardened core material 6a may be called the three-dimensional object 1.

According to the three-dimensional object forming method according to the embodiment described above, in the core portion sealing step illustrated in Fig. 3, the sealing portion 4a is formed on the upper surface of the core material 6 filled in the core portion 5 so as to leave the uncured region 2a of the shell material 2, and the opening of the core portion 5 is sealed by the sealing portion 4a. Then, after the core portion sealing step, the core material curing step illustrated in Fig. 4 is performed.
Therefore, if gas is generated from the heated core material 6 during the core material hardening process, the generated gas will be removed from the unhardened region 2a of the shell material 2 as air bubbles 6b, thereby preventing molding defects such as void-like defects in the hardened core material 6a due to the air bubbles 6b.

Furthermore, in the core material hardening process using the heat hardening means 30, heating is performed with the opening of the core portion 5 sealed by the sealing portion 4a. Therefore, even if the temperature inside the heat hardening means 30 is raised to a temperature higher than the heat hardening temperature Tpc of the core material 6 and the shell 4 becomes soft, the sealing portion 4a can prevent the shell 4 from being unable to withstand the weight of the core material 6 and becoming deformed. In other words, the sealing portion 4a acts to suppress deformation of the shell 4, and can also suppress deformation of the core portion 5 during the core material hardening process.

Furthermore, according to the three-dimensional modeling method of the above embodiment, in the core portion sealing process, ultraviolet light is irradiated onto the upper surface of the uncured region 2a of the shell material 2 within the core portion 5 to harden only the upper layer 2b of the uncured region 2a, so that the process of forming the sealing portion 4a on the upper surface of the core material 6 within the core portion 5 while leaving the uncured region 2a on its upper surface can be performed efficiently.
Furthermore, since the core material 6 is composed of a thermosetting resin, the core material filling process illustrated in FIG. 2 can be easily carried out under normal temperature and pressure conditions, and in the core material hardening process, the entire core material 6 can be efficiently hardened into an integrated state.

Furthermore, according to the three-dimensional modeling method of the above embodiment, the size (volume) of the unhardened area 2a of the shell material 2 in the core portion 5 is adjusted according to the amount of core material 6 filled in the core portion 5, so that gas generated from the core material 6 during the core material hardening process can be more reliably expelled into the unhardened area 2a of the shell material 2.

Furthermore, according to the three-dimensional modeling method of the above embodiment, a separation process is provided after the core material hardening process, so that a three-dimensional modeled object 1 mainly made of hardened core material 6a can be obtained without molding defects such as void-like defects caused by gas generated from the core material 6 and with deformation suppressed.
Furthermore, by manufacturing the three-dimensional object 1 using the three-dimensional modeling method according to the above embodiment, it is possible to improve the accuracy of the dimensions and shape of the three-dimensional object 1 which is mainly made of the hardened core material 6a, and since there is no layer interface in the hardened core material 6a, it is possible to form a three-dimensional object 1 which has no directionality in rigidity or strength.

In addition, the core sealing step in the three-dimensional modeling method according to the embodiment described above is performed by the ultraviolet irradiation device 20. However, in another embodiment, for example, after the core material filling step, the modeling table 15 in the modeling tank 11 may be raised above the liquid level of the shell material 2, and then an ultraviolet irradiator 21 may be positioned above the shell 4 on the modeling table 15, and ultraviolet light may be irradiated from the ultraviolet irradiator 21 toward the upper surface of the shell 4 to form the sealing portion 4a.

In addition, in the three-dimensional modeling method according to the embodiment described above, in the core sealing step, the opening of the core part 5 is sealed by hardening only the upper layer of the unhardened area of the shell material 2. However, in another embodiment, in the core sealing step, the opening of the core part 5 may be sealed by covering the opening of the core part 5 with a separately prepared lid member.

In another embodiment, after the core material hardening process is completed, the shell 4 removed from the heat hardening means 30 may be handled as a three-dimensional object without performing the separation process, that is, the shell 4 having the unhardened area 2a of the shell material 2 on the upper surface of the hardened core material 6a and the opening of the core portion 5 sealed.

The present invention is not limited to the above embodiments, and each of the steps of the shell forming process, core material filling process, core sealing process, core hardening process, and separation process can be modified in various ways depending on the shape of the molded object, etc., and it goes without saying that these are also included within the scope of the present invention.
In the above embodiment, the case where the shell material 2 used to form the shell 4 is a liquid phase material has been described. However, the method of forming the shell 4 is not limited to the method of hardening a liquid phase material (liquid phase polymerization method), and other additive manufacturing methods such as fused deposition molding (FDM) may also be applied.

The present invention is widely applicable in the field of additive manufacturing technology such as 3D printers, and by applying the present invention to this field, it will be possible to realize not only prototyping but also mass production of parts and products that require light weight and high strength, such as parts used in various industrial equipment such as automobiles, aircraft, and robots, nursing care products, and sporting goods.

Reference Signs List 1 Three-dimensional object 2 Shell material 2a Uncured region 2b Upper layer 3 Cured ultraviolet

curable resin layer

4, 40 Shell

4a Sealing portion

5, 50

Core portion

6, 60

Core material

6a, 60a Cured

core material

6b, 60b Gap 100 Three-dimensional modeling system 10 Three-dimensional modeling device 11 Modeling tank 12 Laser optical system 12a Ultraviolet laser light source 12b Scanning optical system 12c Ultraviolet laser light 13 Core material supply system 13a Core material tank 13b Pump 13c, 13d Piping system 14 Nozzle 15 Modeling table 20 Ultraviolet irradiation device 21 Ultraviolet irradiator 30 Thermal curing means 31 Tool

Claims

a shell forming process for forming a shell that defines an outer shape of a three-dimensional object using a shell material;
a core material filling step of filling a core portion, which is a portion surrounded by an inner surface of the shell, with a core material, which is a liquid phase material;
and hardening the core material in the core portion,
a core portion sealing step of sealing an opening of the core portion while leaving an uncured region of the shell material on an upper surface of the core material filled in the core portion;
the core material hardening step is carried out after the core sealing step.
The core sealing step includes:
2. The method for fabricating a three-dimensional object according to claim 1, wherein the opening of the core portion is sealed by curing only an upper layer portion of the uncured region of the shell material.
the shell material contains a resin that is cured by irradiation with active energy rays,
In the core sealing step, the active energy rays are irradiated onto an upper surface of the uncured region of the shell material to cure only the upper layer portion of the uncured region of the shell material,
the core material comprises a thermosetting resin;
3. The three-dimensional object fabrication method according to claim 2, wherein in the core material hardening step, thermal energy is applied to the core material to thermally harden the core material.
The three-dimensional modeling method according to any one of claims 1 to 3, characterized in that the size of the unhardened area of the shell material is adjusted according to the amount of the core material filled in the core portion.
After the core material hardening step,
The method for three-dimensional object fabrication according to any one of claims 1 to 3, further comprising a separation step of separating at least a part of the shell from the hardened core material to obtain a three-dimensional object having a shape following a shape of the core portion and consisting mainly of the core material.
A method for manufacturing a three-dimensional object, comprising the steps of: Manufacturing a three-dimensional object using the three-dimensional modeling method according to claim 5.
A three-dimensional object having a structure including a shell forming an outer shell layer and a hardened core material in a core portion surrounded by an inner surface of the shell,
The shell is formed by hardening a shell material,
an uncured region of the shell material on an upper surface of the cured core material;
A three-dimensional object, wherein the opening of the core portion is sealed.
The three-dimensional object according to claim 7, characterized in that the opening of the core portion is sealed with the shell.