Three-dimensional modeling method

Abstract

To provide a method of molding three-dimensional solid capable of filling a core material into all parts of a core part.SOLUTION: A method of molding a three-dimensional solid to form a three-dimensional molded article including a core material 116 includes: molding firstly a shell 125 which is an outer shell layer of a three-dimensional molded article using a shell material 121 which is a liquid phase material; and thereafter filling a core material 116 which is a liquid phase material into a core part 126 which is a part surrounded by the molded shell 125 to substitute the shell material 121 of the core part 126 with the core material 116, where an opening is provided on a part of the shell 125 positioned at a highest part in a gravity direction in a shape of the core part 126, and the core material 116 is filled into the core part 126 from this opening.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a three-dimensional fabrication method for forming a three-dimensional object using additive manufacturing techniques such as 3D printing. [Background technology]

[0002] 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 3D CAD data, divides the object into thin, circular cross-sectional components, forms these cross-sectional components using various methods, and stacks them to form the desired object. 3D printing technology is often used internationally as a synonym for Additive Manufacturing Technology, and the Japanese translation of the term is additive manufacturing technology.

[0003] 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 actual products before mass production. In particular, the three-dimensional modeling method disclosed in Patent Document 1 below involves repeating the formation of shell layers and filling of core material multiple times in a modeling tank, and then curing the core material all at once by irradiating it with active energy rays or applying thermal energy. This eliminates the layer interface in the model formed from the core material, making it possible to create a model with no directional rigidity or strength. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-136923 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the above-described three-dimensional modeling method, when the shape of the core portion inside the shell becomes complex, there is a risk that the core material may not be filled in part of the core portion. Specifically, when the core portion 226 has a plurality of maximum portions 231a and 231b each having an opening and a convex shape, such as the maximum portions 231a and 231b shown in Fig. 12, if the nozzle 220 is inserted into the maximum portion 231b and the core material is discharged from the nozzle 220, the height of the interface between the core material 216 and the shell material 221 tends to become uniform between the maximum portions. Therefore, the core material 216 is not filled to a predetermined height or more in the maximum portion 231a. In addition, the core material 216 leaks from the opening in the maximum portion 231b through which the nozzle 220 is inserted, contaminating the shell material 221 in the modeling tank.

[0006] In view of the above problems, the present invention aims to provide a three-dimensional object forming method that can fill the entire core portion with a core material. [Means for solving the problem]

[0007] In order to solve the above problems, the three-dimensional fabrication method of the present invention first forms a shell, which is the outer layer of a three-dimensional object, using a shell material, which is a liquid phase material, and then fills the core portion, which is the part surrounded by the formed shell, with a core material, which is a liquid phase material, thereby replacing the core portion with the shell material and forming a three-dimensional object containing the core material, characterized in that an opening is provided in the part of the shell that is located at the highest point in the direction of gravity in the shape of the core portion, and the core material is filled into the core portion through this opening.

[0008] This three-dimensional modeling method allows the core material to be filled at least up to the highest part of the core portion.

[0009] The core portion may have a shape with maximum portions, and a discharge port may be provided in the portion of the shell located at each of the maximum portions to allow the replaced shell material to be discharged from the core portion.

[0010] By doing so, the shell material is not confined within the maximum portion, and it is possible to replace the shell material with the core material until the core portion is entirely filled with the core material.

[0011] In addition, it is preferable to connect at least some of the outlets to a tubular member that extends to a position above the height of the shell located at the highest part and serves as a flow path for the shell material and / or the core material from the core part.

[0012] This prevents the core material from leaking into the modeling tank from other locations while filling the core material up to the highest point.

[0013] Furthermore, the three-dimensional object having a desired shape may be obtained by repeatedly performing the steps of: forming the shell to a predetermined height; filling the core portion of the shell formed to the predetermined height with the core material until replacement of the core material in at least the maximum portion is completed; and closing the outlet corresponding to the maximum portion.

[0014] By doing so, the core material can be filled into the entire core portion without leaking out from the maximum portion formed in the middle.

[0015] Furthermore, the core portion that is finally formed may have a plurality of the maximum portions, and each time a shell that surrounds a maximum portion is formed, the shaping of the shell may be stopped and the core material may be filled.

[0016] By doing so, the core material can be filled into the entire core portion having a shape with a plurality of maximum portions without leaking out of the maximum portion. [Effects of the Invention]

[0017] According to the three-dimensional fabrication method of the present invention, the core material can be filled into the entire core portion. [Brief explanation of the drawings]

[0018] [Figure 1]1A and 1B are diagrams illustrating a three-dimensional object fabrication apparatus for carrying out a three-dimensional object fabrication method according to the present invention. [Figure 2] 1A to 1C are diagrams illustrating a three-dimensional object fabrication method according to an embodiment of the present invention. [Figure 3] 10A to 10C are diagrams illustrating a process of filling the entire core portion with a core material in the three-dimensional object fabrication method of the present embodiment. [Figure 4] 1A and 1B are diagrams illustrating an example in which filling of a core material fails in a conventional three-dimensional modeling method. [Figure 5] 10A to 10C are diagrams illustrating a process of filling the entire core portion with a core material in the three-dimensional object fabrication method of the present embodiment. [Figure 6] 10A to 10C are diagrams illustrating a process of filling the entire core portion with a core material in the three-dimensional object fabrication method of the present embodiment. [Figure 7] 10A to 10C are diagrams illustrating a three-dimensional object fabrication method according to another embodiment of the present invention. [Figure 8] 10A to 10C are diagrams illustrating a three-dimensional object fabrication method according to another embodiment of the present invention. [Figure 9] 1A to 1C are diagrams illustrating an example of the shape of a three-dimensional object obtained by the three-dimensional object fabrication method of the present embodiment. [Figure 10] 10A to 10C are diagrams illustrating a three-dimensional object fabrication method according to another embodiment of the present invention. [Figure 11] 10A to 10C are diagrams illustrating a three-dimensional object fabrication method according to another embodiment of the present invention. [Figure 12] 1A and 1B are diagrams illustrating an example in which filling of a core material fails in a conventional three-dimensional modeling method. DETAILED DESCRIPTION OF THE INVENTION

[0019] A three-dimensional object fabrication apparatus for carrying out the three-dimensional object fabrication method of the present invention will be described with reference to FIG.

[0020] The three-dimensional modeling apparatus 100, which is a composite material 3D printer, mainly comprises a modeling tank 111 in which a shell material 121, which is an ultraviolet curable resin, is stored, a laser optical system 112, and a core material supply system 113.

[0021] A shell material 121, which is a liquid phase material, is stored in the modeling tank 111, and the liquid surface position can be maintained and adjusted at a predetermined position by a shell material adjustment system (not shown). Well-known materials such as epoxy and acrylic shell materials can be used as the shell material 121. A modeling table 128 is provided in the modeling tank 111. The modeling table 128 is used to support a three-dimensional object, and can be moved and set to any position in the Z-axis direction in the figure by a drive mechanism (not shown).

[0022] The laser optical system 112 consists of an ultraviolet laser light source 114 and a scanning optical system 115, and the ultraviolet laser light 130 emitted from the ultraviolet laser light source 114 can be scanned over a predetermined range on the liquid surface of the shell material 121 (i.e., the XY plane) by the scanning optical system 115.

[0023] The shell material 121 is hardened by irradiation with the ultraviolet laser light 130 to a predetermined depth from the liquid surface, as shown by the hardened ultraviolet curing resin 123 in Figure 1. This hardening depth is generally about 0.1 mm to 0.2 mm. Of course, this hardening depth can be adjusted by adjusting the output of the ultraviolet laser light source 114.

[0024] The top surface of the modeling table 128 is positioned at a depth below the liquid surface of the shell material 121 to approximately this hardening depth, and ultraviolet laser light 130 is irradiated to any position on the liquid surface of the shell material 121, thereby forming hardened ultraviolet curing resin 123 of any area on the modeling table 128.

[0025] After the cured ultraviolet curable resin 123 is formed on the modeling table 128, the modeling table 128 is lowered by the curing depth, and then ultraviolet laser light 130 is irradiated to any position on the liquid surface of the shell material 121, thereby stacking the cured ultraviolet curable resin 123 on top of the cured ultraviolet curable resin 123.

[0026] Then, by repeatedly lowering the modeling table 128 and irradiating the liquid surface of the shell material 121 with the ultraviolet laser light 130, the cured ultraviolet curable resin 123 is layered, and a three-dimensional shape of the cured ultraviolet curable resin 123 can be obtained. In the present invention, the object thus formed is called a shell 125. This shell 125 is an outer shell layer for filling the hollow core material 116, and the part surrounded by the shell 125 that has a bottom surface is called a core portion 126.

[0027] The core material supply system 113 uses a pump 119 to pump and supply the core material 116, which is a liquid material, from a core material tank 117 that stores the core material 116 therein via piping systems 118b and 118a in order, and discharges it from the tip of a nozzle 120. The nozzle 120 can be moved and fixed in each of the X, Y, and Z axes in the figure by a movement mechanism (not shown). For this reason, the piping system 118a has a flexible configuration and material so that it can follow the movement of the nozzle 120. The core material 116 is a thermosetting resin in which a reinforcing material is uniformly dispersed, and like the shell material 121, known thermosetting resins such as epoxy and acrylic can be used. The specific gravity of the core material 116 is greater than that of the shell material 121.

[0028] The core material 116 is filled into the core portion 126 of the shell 125, and thermal energy is applied to the core material 116 while it is filled into the core portion 126, thereby thermally curing the core material 116. The thermally cured core material 116 is the three-dimensional object in this description, and a three-dimensional object of a desired shape can be obtained by filling the core portion 126 of a desired shape with the core material 116 and then thermally curing it. Furthermore, according to this method, there is no layer interface in the three-dimensional object formed from the core material 116, so it is possible to form a three-dimensional object with no directional rigidity or strength.

[0029] Next, a three-dimensional object fabrication method using the above three-dimensional object fabrication apparatus 100 according to one embodiment of the present invention will be described with reference to FIG.

[0030] In the three-dimensional modeling method of the present invention, a shell 125 is formed on a modeling table 128 by irradiating a shell material 121 with ultraviolet laser light 130, and a core material 116 is ejected from a nozzle 120 inserted into a core portion 126 formed in the shell 125 into the core portion 126, thereby progressing the filling of the core material 116.

[0031] Furthermore, the core material 116 is discharged into the core portion 126 while the shell 125 is immersed in the shell material 121 in the forming tank 111, and the shell material 121 is present in the core portion 126 before the core material 116 is filled. As the core material 116, which has a larger specific gravity than the shell material 121, is filled, the shell material 121 is pushed up and is pushed out from the core portion 126 to the outside of the shell 125 through an opening provided in the top of the shell 125. In other words, the shell material 121 is replaced with the core material 116.

[0032] 2 has two maximum portions 131 (maximum portions 131a and 131b), and the portion of the shell 125 located at each maximum portion 131 is provided with an outlet 132 (outlet 132a and 132b), which is an opening through which the shell material 121 is discharged. In other words, the maximum portion 131 referred to in this description is a portion having an upwardly convex shape, and the outlet 132 is preferably provided at the highest portion of the maximum portion 131 in the direction of gravity. That is, if the maximum portion 131 has a curved surface as shown in FIG. 2, the outlet 132 is preferably provided so as to communicate with the highest portion of the curved surface, and if the top of the maximum portion 131 is a flat surface, the outlet 132 is preferably provided so as to communicate with somewhere on the flat surface.

[0033] Furthermore, maximum portion 131a is located higher in the direction of gravity than maximum portion 131b, and maximum portion 131a forms the highest part of core portion 126. Nozzle 120 is inserted into core portion 126 from outlet 132a that communicates with maximum portion 131a. Therefore, of outlets 132, at least outlet 132a has a size sufficient to accommodate insertion of nozzle 120.

[0034] Next, the process of filling the entire core portion with the core material in the three-dimensional object fabrication method of this embodiment will be described with reference to FIGS.

[0035] 3(a) shows the state at the start of filling of the core material 116. At the start of filling, the core part 126 contains the shell material 121, and as the core material 116 is filled, the same amount of shell material 121 as the filled core material 116 is discharged from the discharge ports 132a and 132b. In other words, the replacement of the shell material 121 with the core material 116 progresses.

[0036] 3(b) shows the state after the filling of core material 116 has progressed for a while. The interface between core material 116 and shell material 121 enters local maximum portions 131a and 131b and rises so that the interface heights become approximately the same within both local maximum portions 131. At this point, the only escape route for shell material 121 in each local maximum portion 131 is through discharge outlet 132 provided in that local maximum portion 131, and shell material 121 in local maximum portion 131a is discharged from discharge outlet 132a, and shell material 121 in local maximum portion 131b is discharged from discharge outlet 132b.

[0037] As a comparative example of this embodiment, Fig. 4 shows how core material 116 is filled when no outlet communicating with maximum peak portion 131b is provided. As core material 116 is filled, the interface between core material 116 and shell material 121 rises, and maximum peak portion 131b is closed by the interface and the inner wall surface of shell 125 that forms maximum peak portion 131b. At this point, the shell material 121 in this closed maximum peak portion 131b has nowhere to escape. Therefore, the replacement of core material 116 with shell material 121 in this portion stops, and core material 116 fills only maximum peak portion 131a. In other words, core material 116 cannot fill the entire core portion 126.

[0038] In contrast to this, in this embodiment, the discharge ports 132 are provided so as to communicate with the respective maximum portions 131, thereby preventing the shell material 121 from having nowhere to escape.

[0039] Returning to the description of the three-dimensional object forming method of this embodiment, FIG. 5(a) shows a state in which the core material 116 has been filled entirely into the maximum portion 131b. If the filling of the core material 116 continues in this state, the core material 116 will leak out from the discharge port 132b. For this reason, a blocking member 133b is provided to block the discharge port 132b, as shown in FIG. 5(b). This stops the supply of the core material 116 to the maximum portion 131b, and the core material 116 is supplied only into the maximum portion 131a, as shown in FIG. 6(a).

[0040] Here, in this embodiment, the closing member 133b is formed by hardening the shell material 121, similar to the shell 125. Specifically, as shown in FIG. 5(a), when the core material 116 has filled the entire maximum portion 131b, the supply of the core material 116 is stopped, the modeling table 128 is raised until the discharge port 132b is at the same height as the liquid level of the shell material 121 in the modeling tank 111, and the ultraviolet laser light 130 is irradiated onto the shell material 121 accumulated in the discharge port 132b, thereby forming the closing member 133b. Then, after the discharge port 132b is closed, the modeling table 128 is lowered, and after the modeling table 128 is lowered, the filling of the core material 116 is resumed.

[0041] 6(b), when the core material 116 has filled the entire maximum portion 131a, filling of the core material 116 into the entire core portion 126 is complete. Here, because the nozzle 120 is inserted through the outlet 132a, which is the opening that forms the highest portion of the core portion 126, the core material 116 is filled up to the highest portion of the core portion 126 without any problems.

[0042] After the core portion 126 has been completely filled with the core material 116, a blocking member 133a is provided to close the outlet 132a as needed, and the core material 116 together with the shell 125 is removed from the modeling table 128. The shell 125 and core material 116 are then placed in a heating device (not shown), and thermal energy is applied to thermally harden the core material 116, resulting in a three-dimensional object of the desired shape. Here, it is preferable that the shell 125 has the property of self-disintegrating when thermal energy is applied.

[0043] Through the above steps, the core material 116 is filled into the entire core portion 126, and a three-dimensional object having a desired shape can be obtained.

[0044] Next, a three-dimensional object fabrication method according to another embodiment of the present invention will be described with reference to FIG.

[0045] 7, a tubular member 134 that serves as a flow path for shell material 121 and / or core material 116 from core portion 126 is connected to outlet 132b of maximum portion 131b, which is located at a low position in the direction of gravity. This tubular member 134 extends to a position equal to or higher than the height of shell 125 at the portion that forms maximum portion 131a, which is the highest part of core portion 126.

[0046] By providing this tubular member 134, even after the core material 116 has been filled into the entire maximum portion 131b, the core material 116 can continue to be filled into the maximum portion 131a without leaking from the vicinity of the maximum portion 131b.

[0047] In this case, the interface between the core material 116 and the shell material 121 rises inside the tubular member 134, and the shape of the three-dimensional object obtained after filling of the core material 116 has a surplus portion 135, which is shown by thick hatching in Fig. 7. In this case, the core material 116 is thermally hardened, the shell 125 is removed, and then the surplus portion 135 is cut off to obtain a three-dimensional object of the desired shape.

[0048] Furthermore, in this embodiment, the tubular member 134 extends vertically upward, but it may also have a shape that extends obliquely upward, for example.

[0049] Next, a three-dimensional object fabrication method according to another embodiment of the present invention will be described with reference to FIG.

[0050] In this embodiment, instead of starting to fill the core material 116 after the entire shell 125 has been formed, a three-dimensional object of the desired shape is obtained by repeatedly performing a process of forming a portion of the shell 125 up to a predetermined height and a process of filling the core portion of the portion of the shell 125 formed up to the predetermined height with core material until replacement of the core material in at least the maximum portion is completed.

[0051] Specifically, when the core portion 126 has a shape having multiple maximum portions 131 (maximum portion 131a, maximum portion 131b) as shown in Figure 8(b), the formation of the shell is stopped each time a maximum portion 131 is formed, and the core material 116 is filled until the maximum portion 131 is filled with the core material 116.

[0052] 8(a), when the formation of shell 125 using irradiation of ultraviolet laser light 130 progresses until maximum portion 131b is formed, the formation of shell 125 is temporarily stopped, and nozzle 120 is inserted into core portion 126a of shell 125a formed at this point, and filling of core material 116 begins. Next, when filling of core material 116 progresses until maximum portion 131b is replaced with core material 116, the filling of core material 116 is temporarily stopped. Next, ultraviolet laser light 130 is irradiated onto shell material 121 accumulated in discharge port 132b, and a blocking member 133b that blocks discharge port 132b is formed.

[0053] Once the formation of the blocking member 133b is complete, the molding of the shell 125 is resumed. Then, as shown in Fig. 8(b), once the molding of the shell 125 has progressed until the core portion 131a is formed (i.e., once the entire shell 125 has been molded), the nozzle 120 is inserted into the core portion 126, and the filling of the core material 116 is resumed, and the filling of the entire core portion 126 progresses.

[0054] As in the present embodiment, the formation of the shell 125 and the filling of the core material 116 may be carried out in stages. Furthermore, in this embodiment, each time the filling of each maximum portion 131 with the core material 116 is completed, the discharge port 132 can be immediately blocked without moving the modeling table 128 up and down. This allows the core material 116 to be filled into the entire core portion 126 without leaking from the maximum portions 131 formed along the way. Note that, in this embodiment as well, the above-described tubular member 134 may be provided.

[0055] On the other hand, in the example of Figures 8(a) and (b), the core portion 126 has two maximum portions 131, so the filling of the core material 116 into the entire core portion 126 is completed by two-stage formation of the shell 125 and filling of the core material 116, but if the core portion 126 has three or more maximum portions 131, the formation of the shell 125 may be stopped and the core material 116 may be filled each time a shell 125 surrounding each maximum portion 131 is formed.

[0056] Next, an application example of the three-dimensional object fabrication method of the present invention will be described with reference to FIGS.

[0057] 9 is a diagram showing an example of the shape of a three-dimensional object. A three-dimensional object 140 has a maximum portion 141 at the bottom, and a canopy portion 142 is provided so as to cover the maximum portion 141. When forming a three-dimensional object 140 of this shape using a core material, if the core material is filled after the entire shell is formed, there is a risk that the core material may not be filled to every corner.

[0058] FIG. 10 shows an example of a three-dimensional modeling method for modeling the three-dimensional model 140 shown in FIG.

[0059] In this three-dimensional fabrication method, the formation of the shell and the filling of the core material are carried out in two stages.

[0060] 10(a), the shell 145a is shaped to a height H1 shown in Fig. 10(a) so that the shape of the core portion 146a is the shape before the formation of the maximum portion 141 and the formation of the overhang portion 142. Then, the nozzle 120 is inserted into the core portion 146a, and the core material 116 is filled into the core portion 146a.

[0061] 10(a), a tubular member 144 is provided so as to communicate with the maximum portion 141. The height of the tubular member 144 is equal to or higher than the liquid level in the forming tank 111 when the core material 116 is filled into the core portion 146a, and is set to a height that does not interfere with the shell 145 that becomes the outer shell layer of the eave portion 142 in FIG. 10(b). The flow path is blocked as soon as filling of the core material 116 into the core portion 146a is completed.

[0062] Next, as shown in FIG. 10(b), additional shaping is performed on the shell 125a to form the entire core portion 126 including the eave portion 142, thereby forming the shell 125. Then, the core portion 116 is filled in. Finally, the shell 125 and the core material 116 are removed from the forming tank 111, and the core material 116 is thermally cured. Then, by cutting off the excess portion 147 of the core material 116 that has entered the tubular member 144, the three-dimensional object with the complex shape shown in FIG. 9 is formed.

[0063] 11 is a diagram illustrating a method for forming the three-dimensional object shown in FIG. 9, which differs from the three-dimensional forming method shown in FIGS. 10(a) and 10(b). In this forming method, filling of the core material 116 begins after the entire shell 125 has been formed, but the tubular member 151 communicating with the maximum portion 141 is formed in a shape that extends upward while avoiding the overhang portion 142. This makes it possible to fill the core material 116 even into the maximum portion 141 that is hidden below the overhang portion 142. Then, by thermally curing the core material 116 and then cutting off the excess portion 152, the three-dimensional object with the complex shape shown in FIG. 9 is formed.

[0064] By using the above three-dimensional modeling method, it is possible to fill the entire core portion with the core material.

[0065] The three-dimensional object fabrication method of the present invention is not limited to the above-described embodiment, and may be of other embodiments within the scope of the present invention. For example, although the above embodiment describes a three-dimensional object formed using only a thermoset core material, the present invention is not limited to this embodiment, and a three-dimensional object may be formed using a thermoset core material and a shell surrounding the core material.

[0066] Furthermore, in the above description, the nozzle that ejects the core material is inserted into the core portion only through the opening that communicates with the part that forms the highest part of the core portion in the direction of gravity, but it is also acceptable for the nozzle to be inserted into openings that are present in not only the highest part but also other maximum parts during the process of filling the core material.

[0067] Furthermore, in the above description, the core material is thermosetting and hardens when thermal energy is applied after filling the core portion, but this is not limited thereto, and hardening may also proceed by leaving it at room temperature, for example. [Explanation of symbols]

[0068] 100 Three-dimensional modeling equipment 111 Modeling tank 112 Laser Optical System 113 Core material supply system 114 Ultraviolet laser light source 115 Scanning Optical System 116 Core material 117 Core material tank 118a Piping system 118b Piping system 119 Pump 120 nozzles 121 Shell material 123 Cured UV curable resin 125 shells 125a shell 126 Core 126a Core 128 Modeling stand 130 Ultraviolet laser light 131a Maximum part 131b Maximum part 132a Outlet 132b Outlet 133a Closure member 133b Closure member 134 Tubular members 135 Surplus 140 Three-dimensional sculpture 141 Maximum part 142 Eaves 144 Tubular members 145 shells 145a Shell 146 Core 146a Core 147 Surplus 151 Tubular members 152 Surplus

Claims

1. A three-dimensional modeling method in which a shell, which is an outer shell layer of a three-dimensional object, is first formed using a shell material, which is a liquid phase material, and then a core material, which is a liquid phase material, is filled into a core portion, which is a portion surrounded by the formed shell, thereby replacing the core portion with the shell material and forming a three-dimensional model including the core material, an opening is provided in a portion of the shell that is located at a highest point in the direction of gravity in the shape of the core portion, and the core material is filled into the core portion through this opening; The shape of the core portion has a maximum portion, a discharge port is provided in a portion of the shell located at each of the maximum portions, through which the replaced shell material is discharged from the core portion; A three-dimensional modeling method, characterized in that at least some of the outlets are connected to tubular members that extend to a position above the height of the shell located at the highest part and serve as a flow path for the shell material and / or the core material from the core part.

2. A three-dimensional modeling method in which a shell, which is an outer shell layer of a three-dimensional object, is first formed using a shell material which is a liquid phase material, and then a core portion, which is a portion surrounded by the formed shell, is filled with a core material which is a liquid phase material, thereby replacing the core portion from the shell material with the core material, thereby forming a three-dimensional model containing the core material, an opening is provided in a portion of the shell that is located at a highest point in the direction of gravity in the shape of the core portion, and the core material is filled into the core portion through this opening; The shape of the core portion has a maximum portion, a discharge port is provided in a portion of the shell located at each of the maximum portions, through which the replaced shell material is discharged from the core portion; shaping the shell to a predetermined height; a step of filling the core portion of the shell shaped to the predetermined height with the core material until replacement of the core material in at least the maximum portion is completed; a step of blocking the outlet corresponding to the maximum portion; and repeating the steps of filling the core material at a position higher than the outlet after blocking the outlet, thereby obtaining the three-dimensional object of a desired shape.

3. The three-dimensional fabrication method according to claim 2, characterized in that the core portion finally formed has a plurality of the maximum portions, and each time a shell surrounding a maximum portion is formed, the formation of the shell is stopped and the core material is filled.

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