Three-dimensional modeling methods

Abstract

To provide a three-dimensional printing method that, in a so-called core-shell method of three-dimensional printing, can produce a three-dimensional object with a shape close to the final shape, even when the final shape of the object has non-flat surfaces on its upper and lower surfaces. [Solution] A method for creating a three-dimensional object, comprising: a shell forming step of forming a shell 4 using a shell material 2 to form the shape of the part of the three-dimensional object excluding the top surface; a core material filling step of filling a core part 5, which is the part enclosed by the shell 4, with a core material 6, which is a liquid phase material; and a core material hardening step of hardening the core material 6 inside the core part 5, wherein, prior to the core material hardening step, a lid attachment step is made to place a lid 7, which forms the non-flat shape of the top surface of the three-dimensional object, on the upper surface of the core material 6 filled in the core part 5.

Description

Technical Field

[0001] The present invention relates to a three-dimensional modeling method, and more particularly to a three-dimensional modeling method for modeling a three-dimensional object using an additive manufacturing technology such as 3D printing.

Background Art

[0002] As the name of a manufacturing apparatus using 3D printing technology, the term "3D printer" is widely used. A 3D printer calculates the cross-sectional shape of a modeled object by computer based on three-dimensional CAD data, divides the modeled object into thin cross-sectional components, forms the cross-sectional components by various methods, and stacks them to form the target modeled object. 3D printing technology is often used internationally as a synonym for Additive Manufacturing Technology, and in Japanese translation, additive manufacturing technology is used.

[0003] In recent years, for modeled objects created by 3D printers, not only appearance but also rigidity and strength are required for evaluation purposes before mass production of actual products, and metal 3D printers and composite material 3D printers have attracted attention. As one of the related technologies, the applicant of this application has proposed a three-dimensional modeling method described in Patent Document 1 below.

[0004] The three-dimensional modeling method described in Patent Document 1 is characterized in that after repeatedly performing shell modeling and core material filling in a modeling tank in which a shell material is stored a plurality of times, the core material is cured collectively by irradiation with active energy rays or application of thermal energy. According to such a three-dimensional modeling method (hereinafter, this method is also referred to as a core-shell modeling method), since there is no lamination interface in the cured core material portion, it has become possible to model a three-dimensional object having no directionality in rigidity and strength. [Problems to be Solved by the Invention]

[0005] Figure 8 schematically shows an example of a three-dimensional object fabricated using the core-shell fabrication method described above. The three-dimensional object 50 shown in Figure 8 has a shell 51 which is an outer shell layer, and a core material 53 is filled into the core portion 52 which is the part surrounded by the shell 51, and then the core material 53 hardens. In the three-dimensional object 50 shown in Figure 8, the bottom surface (underside) of the shell 51 is flat. However, for example, when forming the shell 51 while hardening the shell material in a build tank, it is possible to form the bottom surface of the shell 51 into a non-flat shape by first forming a support part using the shell material between the build platform installed in the build tank and the shell 51.

[0006] On the other hand, the upper surface of the three-dimensional object 50 is such that the core material 53 is filled into the core portion 52. Therefore, forming the support portion inside the core portion 52 is undesirable as it would reduce the rigidity and strength of the object, and it is not possible to form a shell 51 with an uneven or non-flat shape below the upper surface of the core material 53.

[0007] Therefore, for example, when creating a three-dimensional object 60 whose final shape is the cross-sectional shape shown in Figure 9(a), that is, having a non-flat shape on the upper and lower surfaces, using the core-shell molding method described above, first, objects 61 and 62 having a cross-sectional shape with a flat upper surface, as shown in Figure 9(b) or Figure 9(c), are fabricated using the core-shell molding method. Then, after fabrication, the upper surfaces 61a and 62a of the hardened core material, which have flat surfaces, are subjected to machining (also called post-processing), such as cutting, to obtain the three-dimensional object 60 with the final shape shown in Figure 9(a).

[0008] Thus, with conventional core-shell molding methods, there was a problem in that it was difficult to create a three-dimensional object with a shape close to the final shape, especially when creating a three-dimensional object whose final shape has non-flat surfaces on the top and bottom, before the aforementioned post-processing was performed. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2019-136923 [Overview of the project] Means for solving the problem and their effects

[0010] The present invention has been made in view of the above problems, and aims to provide a three-dimensional molding method that can produce a three-dimensional object with a shape close to the final shape, even when the final shape of the molded object has a non-flat shape on its upper and lower surfaces, in a so-called core-shell molding method.

[0011] To achieve the above objective, the three-dimensional molding method (1) according to the present invention is: The shell molding process involves creating a shell using shell material to form the shape of the part of a three-dimensional object excluding the top surface, A core material filling step is performed in which a core material, which is a liquid phase material, is filled into the core portion, which is the part enclosed by the shell. A method for creating a three-dimensional object, comprising a core material hardening step for hardening the core material within the core portion, The method is characterized by including a lid attachment step, which involves placing a lid that forms the non-flat shape of the upper surface of the three-dimensional object on the upper surface of the core material filled in the core portion, prior to the core material hardening step.

[0012] According to the above three-dimensional molding method (1), the lid attachment step is included before the core material hardening step. In the lid attachment step, the lid is placed over the upper surface of the core material, so that the non-flat shape of the upper surface of the three-dimensional molded object is formed by the lid before the core material hardening step begins. Then, in the subsequent core material hardening step, the core material hardens in the non-flat shape formed by the lid. Therefore, at the stage when the core material hardening process is completed, the non-flat shape on the upper surface of the three-dimensional object can also be fabricated, and even when the final fabricated shape of the object has non-flat shapes on its upper and lower surfaces, it is possible to fabricate a three-dimensional object with a shape close to the final fabricated shape.

[0013] Furthermore, the three-dimensional molding method (2) according to the present invention is, in the three-dimensional molding method (1) described above, The method is characterized by including a lid molding step for molding the lid before the lid attachment step.

[0014] According to the above three-dimensional molding method (2), since the lid molding step is included, by molding the lid before the lid attachment step, it becomes possible to quickly place the lid on the upper surface of the core material after the core material filling step.

[0015] Furthermore, the three-dimensional molding method (3) according to the present invention is, in the three-dimensional molding method (2) described above, The shell forming process and the lid forming process are characterized in that they are carried out using a liquid tank polymerization method in a forming tank in which the shell material is stored.

[0016] According to the above three-dimensional molding method (3), the shell molding step and the lid molding step are carried out using a liquid bath polymerization method in the molding tank where the shell material is stored. This makes it possible to use the same material for the shell and the lid, and to efficiently mold the shell and the lid.

[0017] Furthermore, the three-dimensional molding method (4) according to the present invention is characterized in that, in the three-dimensional molding method (2) or (3) described above, a transparent liquid phase material is used for the shell material.

[0018] According to the above three-dimensional shaping method (4), since a liquid-phase material having transparency is used for the shell material, the lid can also have transparency together with the shell, and in the lid attachment step, the state of the interface between the lid and the core material when the lid is placed on the upper surface of the core material can be easily confirmed through the lid.

[0019] Moreover, the three-dimensional shaping method (5) according to the present invention is, in any one of the above three-dimensional shaping methods (1) to (4), the lid has a hole, in the lid attachment step, while extracting the air trapped between the upper surface of the core material and the lid from the hole, the lid is placed on the upper surface of the core material.

[0020] According to the above three-dimensional shaping method (5), in the lid attachment step, the lid can be placed on the upper surface of the core material so as not to generate an air pocket between the upper surface of the core material and the lid. Therefore, it is possible to prevent a phenomenon in which a shaping defect such as a void defect due to the air pocket occurs in the hardened core material after the core material hardening step.

[0021] Moreover, the three-dimensional shaping method (6) according to the present invention is, in any one of the above three-dimensional shaping methods (1) to (5), after the core material hardening step, including a separation step of separating at least a part of the shell and the lid from the hardened core material.

[0022] According to the above three-dimensional shaping method (6), since the separation step is included after the core material hardening step, a three-dimensional shaped object having a shape close to the final shaping shape mainly composed of the hardened core material can be obtained.

Brief Description of the Drawings

[0023] [Figure 1] It is a schematic diagram showing a configuration example of a three-dimensional shaping apparatus used in the three-dimensional shaping method according to an embodiment of the present invention. [Figure 2] This is a diagram illustrating the lid fabrication process included in the three-dimensional fabrication method according to the embodiment. [Figure 3] This is a diagram illustrating the shell fabrication process included in the three-dimensional fabrication method according to the embodiment. [Figure 4] This is a diagram illustrating the core material filling process included in the three-dimensional molding method according to the embodiment. [Figure 5] This diagram illustrates the lid attachment process included in the three-dimensional molding method according to the embodiment, where (a) shows the state before the lid is placed over the top surface of the core material, (b) shows the state in the process of placing the lid over the top surface of the core material, and (c) shows the state after the lid has been placed over the top surface of the core material. [Figure 6] This figure illustrates an example of a core material hardening process included in the three-dimensional molding method according to the embodiment, with (a) being a cross-sectional view showing the state before the core material hardens and (b) being a cross-sectional view showing the state after the core material hardens. [Figure 7] This figure illustrates an example of a separation step included in the three-dimensional molding method according to the embodiment, with (a) being a cross-sectional view showing the state before shell separation, and (b) and (c) showing the state after shell separation. [Figure 8] This is a schematic perspective view showing an example of a three-dimensional object fabricated using a conventional core-shell 3D printing method. [Figure 9] This diagram illustrates a method for fabricating an object with non-flat shapes on its upper and lower surfaces using a conventional core-shell fusion method. (a) is a cross-sectional view showing an example of the final fabricated shape, and (b) and (c) are cross-sectional views showing examples of shapes that can be fabricated using the core-shell fusion method. [Modes for carrying out the invention]

[0024] The embodiments of the three-dimensional molding method according to the present invention will be described below with reference to the drawings. Note that the forms of the three-dimensional molded objects shown in the drawings are schematic representations to facilitate understanding of the spirit of the present invention, and are not limited to these forms.

[0025] Figure 1 is a schematic diagram showing an example of the configuration of a three-dimensional molding apparatus used in the three-dimensional molding method according to the embodiment. In the following description, one direction of the horizontal plane is defined as the X-axis direction, the direction perpendicular to this on the horizontal plane is defined as the Y-axis direction, and the direction perpendicular to the XY plane (horizontal plane) is defined as the Z-axis direction. The 3D printing apparatus 10 functions as a composite material 3D printer and primarily comprises a printing tank 11 where printing is performed by liquid tank photopolymerization, a laser optical system 12, and a core material supply system 13. In addition, the 3D printing method according to this embodiment uses a thermosetting means 16. Including these components, an apparatus capable of printing three-dimensional objects using a core-shell printing method is configured.

[0026] Inside the molding tank 11, a photocurable resin, which is a liquid phase material, is stored as the shell material 2. The liquid level can be maintained and adjusted to a predetermined position by a photocurable resin adjustment system (not shown). For the shell material 2, known UV-curable resins such as epoxy or acrylic resins can be used, and transparent materials are used. A build platform 15 is provided inside the build tank 11. The build platform 15 is for supporting the object being built 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).

[0027] The laser optical system 12 comprises an ultraviolet laser light source 12a and a scanning optical system 12b. An ultraviolet laser beam 12c, which is one of the active energy rays, is emitted from the ultraviolet laser light source 12a, and the emitted ultraviolet laser beam 12c can be scanned over a predetermined range on the liquid surface (i.e., the xy plane) of the shell material 2 by driving the scanning optical system 12b.

[0028] When ultraviolet laser light 12c is irradiated onto the shell material 2, the shell material 2 hardens to a predetermined depth from the liquid surface, forming a hardened ultraviolet-cured resin layer 3. This hardening depth can be adjusted within a predetermined range, for example, within a range of about 0.1 mm to 0.4 mm, by adjusting the output of the ultraviolet laser light source 12a.

[0029] Therefore, by positioning the upper surface of the build plate 15 at a depth submerged by a predetermined curing depth from the liquid surface of the shell material 2, leveling the liquid surface of the shell material 2 with a recoater (not shown), and then irradiating an ultraviolet laser beam 12c at any position on the liquid surface of the shell material 2, a cured ultraviolet-curable resin layer 3 of any area is formed on the build plate 15. Subsequently, the build plate 15 is lowered by the curing depth, the liquid surface of the shell material 2 is leveled with the recoater, and then ultraviolet laser light 12c is irradiated at an arbitrary position on the liquid surface of the shell material 2, so that the cured ultraviolet curing resin layer 3 is laminated on top of the cured ultraviolet curing resin layer 3.

[0030] Then, by repeatedly performing the lowering motion of the build plate 15 and the irradiation of the liquid surface of the shell material 2 with ultraviolet laser light 12c, the cured ultraviolet-curable resin layer 3 is stacked, making it possible to create a three-dimensional object. In this embodiment, among the molded objects formed by hardening the shell material 2 in this way, the part that shapes the shape of the portion of the three-dimensional object excluding the top surface, that is, the part that functions as an outer shell layer, is called the shell 4 (see Figure 3), and the part that has the function of shaping the non-flat shape of the top surface of the three-dimensional object is called the lid 7 (see Figure 2).

[0031] The core material supply system 13 comprises a core material tank 13a for storing core material 6, piping systems 13c and 13d connected to the core material tank 13a, a pump 13b installed in the middle of the piping systems 13c and 13d, and a nozzle 14 attached to the outlet of the piping system 13d. The core material supply system 13 is configured to drive the pump 13b to supply core material 6 from the core material tank 13a to the nozzle 14 via the piping systems 13c and 13d, and to discharge the core material 6 from the tip of the nozzle 14. The nozzle 14 is composed of, for example, a needle nozzle with a small diameter that does not cause clogging of the core material 6. Furthermore, the nozzle 14 can be moved and fixed in the XYZ directions in the figure by a nozzle moving mechanism (not shown). Therefore, the piping system 13d is composed of a flexible structure and material so that it can follow the movement of the nozzle 14.

[0032] 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 epoxy or acrylic. The reinforcing material may be a fibrous reinforcing material containing at least one of carbon fibers, glass fibers, and aramid fibers, or it may be an inorganic material powder such as silica. The reinforcing material is preferably carbon fiber, and more preferably contains milled carbon fibers which are short fibers with a length of 200 μm or less. Furthermore, the specific gravity of the core material 6 is higher than the specific gravity of the shell material 2, and the viscosity of the core material 6 is higher than the viscosity of the shell material 2, preferably at least twice the viscosity of the shell material 2.

[0033] The thermosetting means 16 is used in the core material curing process described later and consists of a heating furnace with a sealable chamber. The thermosetting means 16 is capable of raising and lowering the temperature inside the heating furnace to a temperature higher than the thermosetting temperature of the core material 6.

[0034] The operation of each part of the 3D modeling apparatus 10 is controlled by a control unit (not shown). The control unit consists of a computer device including an arithmetic processing unit and a memory unit. The memory unit stores a program for controlling the operation of each part of the 3D modeling apparatus 10, 3D shape data (CAD data) of the 3D model to be created, and various other setting data necessary for modeling. The arithmetic processing unit executes a process to control the operation of each part of the 3D modeling apparatus 10 based on the program.

[0035] Next, an example of a three-dimensional fabrication method according to the embodiment will be explained using Figures 2 to 7. The three-dimensional molding method according to the embodiment is a method for molding a three-dimensional object 1 (see Figure 7) whose final molded shape has a non-flat shape on its upper and lower surfaces, and includes a lid molding step, a shell molding step, a core material filling step, a lid attachment step, and a core material hardening step, and further includes a separation step.

[0036] The lid fabrication process, as shown in Figure 2, is a process in which the lid 7 is fabricated in the fabrication tank 11 using a liquid tank photopolymerization method and the photopolymerization reaction of the shell material 2. The lid 7 is used to form the non-flat shape of the upper surface of the three-dimensional fabricated object.

[0037] As shown in Figure 3, the shell fabrication process involves fabricating a shell 4 in a fabrication tank 11 using a photopolymerization reaction of the shell material 2, which forms the shape of the part of the three-dimensional object excluding the top surface, by liquid tank photopolymerization. This shell 4 functions as an outer shell layer for filling the core material 6.

[0038] The core material filling process described above is a process of filling the core material 6 into the core portion 5, which is the part enclosed by the shell 4, as shown in Figure 4. The core portion 5 is the part enclosed by the inner surface of the shell 4 that has a bottom surface.

[0039] As shown in Figure 5, the lid attachment step is a step in which, after the core material filling step, the lid 7 is placed over the upper surface of the core material 6 that has been filled into the core portion 5. As shown in Figure 6, the core material hardening step is a step in which the core material 6 inside the core portion 5 is hardened using a heat hardening means 16 after the cover attachment step. Furthermore, as shown in Figure 7, the separation step is a step in which all or part of the shell 4 and lid 7 are separated, or removed, from the hardened core material 6a after the core material hardening step.

[0040] The following describes specific examples of each step included in the three-dimensional modeling method according to the embodiment. Figure 2 is a diagram illustrating the lid fabrication process. The lid fabrication process involves retracting the nozzle 14 of the core material supply system 13 from the irradiation range of the ultraviolet laser light 12c, and then using the photopolymerization reaction of the shell material 2 to fabricate a lid 7 having a non-flat shape on the fabrication table 15 by irradiating the liquid surface of the shell material 2 with light using the laser optical system 12 and lowering the fabrication table 15.

[0041] In other words, in the lid fabrication process, based on the three-dimensional shape data of the lid 7, the operation of scanning and irradiating the liquid surface of the shell material 2 on the build plate 15 with ultraviolet laser light 12c and the operation of lowering the build plate 15 by the curing depth are performed alternately, so that as shown in Figure 2, a lid 7 having an uneven shape in cross-section via support parts 8 is fabricated on the build plate 15. After the lid 7 is fabricated, the build plate 15 is moved above the liquid surface of the shell material 2, the lid 7 is removed from the build plate 15, and any unnecessary support parts 8 are removed as appropriate. The thickness of the lid 7 should be such that it does not easily deform during the subsequent lid attachment process, for example, a thickness of a few millimeters is sufficient, and if there is a subsequent separation process, it is preferable that it be as thin as possible from the viewpoint of ease of separation.

[0042] After completing the lid fabrication process, the process proceeds to the shell fabrication process shown in Figure 3. The shell fabrication process is basically carried out in the same manner as the lid fabrication process. The shell fabrication process involves retracting the nozzle 14 of the core material supply system 13 from the irradiation range of the ultraviolet laser light 12c, and then using the photopolymerization reaction of the shell material 2 to fabricate a shell 4 having a non-flat bottom surface on the fabrication table 15 by irradiating the liquid surface of the shell material 2 with light using the laser optical system 12 and lowering the fabrication table 15.

[0043] In other words, in the shell fabrication process, based on the three-dimensional shape data of the shell 4, the process alternates between scanning and irradiating the liquid surface of the shell material 2 on the build plate 15 with ultraviolet laser light 12c and lowering the build plate 15 by the amount of the curing depth. As shown in Figure 3, a shell 4 having an uneven bottom surface via a support section 8 is fabricated on the build plate 15. The shell 4 shown in Figure 3 is fabricated in the shape of a box with a bottom, having an uneven surface in cross-section on the bottom surface and a rectangular opening on the top surface. The thickness of the shell 4 is not particularly limited, but it should be thin enough so that it does not easily deform during the subsequent core material curing process, for example, a few millimeters. If there is a subsequent separation process, it is preferable to make it as thin as possible from the viewpoint of ease of separation.

[0044] After the shell 4 is fabricated, with the shell 4 positioned below the liquid level of the shell material 2 in the fabrication tank 11, the process then proceeds to the core material filling step shown in Figure 4. The core material filling process involves moving the nozzle 14 of the core material supply system 13 into the core section 5, which is the part enclosed by the shell 4, and then discharging the core material 6 from the nozzle 14 to fill the core section 5 with the core material 6. The filling of the core material 6 is performed with the tip of the nozzle 14 inserted into the filled core material 6. Furthermore, the filling of the core material 6 is performed while moving the nozzle 14 in the horizontal (XY axis) and vertical (Z axis) directions within the core section 5.

[0045] As shown in Figure 4, the core material filling process is carried out with the shell 4 positioned below the liquid level of the shell material 2 in the molding tank 11. Before filling with core material 6, the shell material 2 is present in the core section 5, as shown in Figure 3. Therefore, as the core material 6, which has a higher specific gravity than the shell material 2, is filled into the core section 5, the shell material 2 inside the core section 5 is pushed up, and as shown in Figure 4, the shell material 2 is pushed out of the shell 4 through the upper opening, and the inside of the core section 5 is replaced from shell material 2 to core material 6. As described above, a predetermined amount of core material 6 is filled into the core portion 5, which is the part surrounded by the inner surface of the shell 4. After filling with the predetermined amount of core material 6, the build plate 15 is moved above the liquid level of the shell material 2, and the shell 4 with the core material 6 filled in is removed from the build plate 15.

[0046] Furthermore, the shell molding process and the core material filling process may be carried out alternately in multiple steps. That is, the process of molding the shell 4 to a predetermined height, filling the core material 6 into the core portion 5 formed by the shell 4, further adding to the shell 4, and then filling the core material 6 into the newly formed core portion 5 by the added shell 4 may be repeated. By dividing the molding of the shell 4 into multiple steps in this way, it becomes possible to fill every corner of the core portion 5 with core material 6 by filling it in stages, especially when the core portion 5 has a complex shape.

[0047] After completing the core material filling process, the process proceeds to the lid attachment process shown in Figure 5. The lid attachment step is a step in which the lid 7, which was formed in the lid molding step, is placed over the shell 4, which has been filled with core material 6 after the core material filling step.

[0048] First, as shown in Figure 5(a), a lid 7 is placed opposite the upper surface of the shell 4 filled with core material 6. A hole 7a is formed in the convex portion of the lid 7. The hole 7a functions as an air vent to release air 9 (see Figure 5(b)) trapped between the upper surface of the core material 6 and the lid 7 when the lid 7 is placed over the core material 6, and also functions as an air vent to release air generated during the heat curing stage of the core material 6, which will be described later. The hole 7a may be drilled after the lid molding process, or it may be molded to have the hole 7a during the lid molding process.

[0049] Next, as shown in Figure 5(b), the lid 7 is placed over the upper surface of the core material 6 filled in the core portion 5 of the shell 4, that is, the lid 7 is lowered while its lower surface is in contact with the upper surface of the core material 6. At this time, the air 9 trapped between the upper surface of the core material 6 and the lower surface of the lid 7 escapes through the hole 7a.

[0050] Furthermore, since a transparent liquid-phase material is used for the shell material 2, the lid 7 formed by hardening the shell material 2 is also transparent. Therefore, it is possible to easily check the state of the interface between the lower surface of the lid 7 and the upper surface of the core material 6, for example, how well the core material 6 fits into the uneven areas on the lower surface of the lid 7 and how well the air 9 escapes. Then, as shown in Figure 5(c), the air 9 trapped between the upper surface of the core material 6 and the lid 7 is removed, and the core material 6 spreads across the entire lower surface of the lid 7, creating contact between the entire lower surface of the lid 7 and the core material 6, thus completing the installation of the lid 7. Note that the hole 7a of the lid 7 is filled with the core material 6.

[0051] After completing the lid attachment process, the process proceeds to the core material hardening process shown in Figure 6. In the core material hardening process, as shown in Figure 6(a), the shell 4, with the lid 7 placed over the upper surface of the core material 6 after the lid attachment process, is placed into the heat hardening means 16 to start the heat hardening process of the core material 6. In other words, the shell 4 is placed in the heat curing means 16, and the temperature inside the heat curing means 16 is raised to a temperature higher than the heat curing temperature of the core material 6. As a result, the entire molded object, including the core material 6, shell 4, and lid 7, is heated, and the hardening of the core material 6 begins and progresses. If air is generated in the core material 6 during heat curing, this air is allowed to escape to the outside of the shell 4 through the holes 7a. After a predetermined time has elapsed, the hardening of the entire core material 6 is completed, and as shown in Figure 6(b), a hardened core material 6a is formed in the core portion 5 surrounded by the shell 4 and lid 7.

[0052] Furthermore, in order to harden the entire core material 6 within the core portion 5, it is preferable to use a material made of thermosetting resin as the core material 6, as in this embodiment, and to harden the core material by thermal energy during the core material hardening process.

[0053] After the core material hardening process is completed, the shell 4 with the hardened core material 6a formed is removed from the heat curing means 16, and the process proceeds to the separation process shown in Figure 7.

[0054] The separation step involves separating at least a portion of the shell 4 and lid 7 from the hardened core material 6a. As shown in Figure 7(a), by separating and removing the shell 4 and lid 7 from the hardened core material 6a using a tool 17 such as a cutting tool, a three-dimensional molded object 1 made of hardened core material 6a having a non-flat shape on its upper and lower surfaces is obtained, as shown in Figure 7(b). In addition, at least a portion of the hardened core material 6a may be further processed by cutting or other means to fine-tune the shape. Furthermore, if the hardened core material 6a has entered the hole 7a of the lid 7, the hardened core material 6a that has entered the hole 7a may be cut off and removed together with the lid 7. In this embodiment, the three-dimensional molded object 1 made of hardened core material 6a is a three-dimensional molded object with a shape close to the final molded shape.

[0055] Figure 7(b) shows a case where the shell 4 and lid 7 are completely separated to obtain a three-dimensional object 1 consisting only of the hardened core material 6a. However, in another embodiment, as shown in Figure 7(c), a portion of the shell 4 may be left intact, and the three-dimensional object 1 may be formed by combining this portion of the shell 4 with the hardened core material 6a. Although not shown, a portion of the lid 7 may also be left intact, and the three-dimensional object 1 may be formed by combining this portion of the lid 7 with the hardened core material 6a. Since there is no layering interface in the hardened core material 6a that constitutes the three-dimensional object 1, the three-dimensional object 1 is a three-dimensional object with no directional rigidity or strength.

[0056] According to the three-dimensional molding method of the above embodiment (1), the lid attachment step is included before the core material hardening step. In the lid attachment step, the lid 7 is placed over the upper surface of the core material 6, so that the non-flat shape of the upper surface of the three-dimensional molded object 1 is formed by the lid 7 before the core material hardening step begins. Then, in the subsequent core material hardening step, the core material 6 is hardened in the non-flat shape formed by the lid 7. Therefore, at the stage when the core material hardening process is completed, the non-flat shape on the upper surface of the three-dimensional object 1 can also be fabricated. Even when fabricating an object whose final fabrication shape has non-flat shapes on its upper and lower surfaces, it is possible to fabricate a three-dimensional object 1 with a shape close to the final fabrication shape, i.e., a near-net shape. As a result, the workload for post-processing performed after fabrication can be greatly reduced.

[0057] Furthermore, according to the three-dimensional molding method of the above embodiment, since the lid molding step is included, the lid 7 can be molded using the same material as the shell 4 before the lid attachment step, and by using the same material for both the shell 4 and the lid 7, the molding cost can be reduced.

[0058] Furthermore, according to the three-dimensional molding method of the above embodiment, the shell molding process and the lid molding process are carried out using a liquid tank photopolymerization method in the same molding tank 11 where the shell material 2 is stored, so that the shell 4 and the lid 7 can be molded efficiently. In the above embodiment, the process proceeds to the shell molding process after the lid molding process is completed, but in another embodiment, the lid molding process and the shell molding process may be carried out simultaneously, that is, the shell 4 and the lid 7 may be molded simultaneously in the molding tank 11, in which case the efficiency of these molding processes can be further increased.

[0059] Furthermore, according to the three-dimensional molding method of the above embodiment, since a transparent liquid phase material is used for the shell material 2, the lid 7 can also be made transparent along with the shell 4. Therefore, in the lid attachment step, the state of the interface between the lid 7 and the core material 6 when the lid 7 is placed on the upper surface of the core material 6 can be easily confirmed by looking through the lid 7.

[0060] Furthermore, according to the three-dimensional molding method of the above embodiment, since the lid 7 has air venting holes 7a, the lid 7 can be placed over the upper surface of the core material 6 in the lid attachment step so as not to create air pockets between the upper surface of the core material 6 and the lid 7. Therefore, it is possible to prevent molding defects such as void-like defects caused by air pockets from occurring in the hardened core material 6a after the core material hardening step.

[0061] Furthermore, according to the three-dimensional molding method of the embodiment, since the separation step is included after the core material hardening step, a three-dimensional molded object 1 mainly composed of the hardened core material 6a can be obtained.

[0062] Furthermore, according to the three-dimensional molding method of the above embodiment, since the core material 6 is made of a thermosetting resin, the core material filling step can be easily performed under normal temperature and pressure conditions, and the core material curing step can be efficiently cured to a state in which the entire core material 6 is integrated.

[0063] Although embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to the embodiments described above, and various modifications are possible, all of which are also included within the scope of the present invention.

[0064] For example, the lid fabrication process is carried out by a liquid bath photopolymerization method in which ultraviolet laser light 12c is scanned within the fabrication tank 11 of the shell material 2 to cure the shell material 2, but the method of fabricating the lid 7 is not limited to this. For example, in another embodiment, the lid 7 may be fabricated using other additive manufacturing techniques such as material extrusion, powder bed fusion bonding, bonding injection, sheet lamination, material injection, or directed energy deposition. In yet another form, the lid 7 may be fabricated by methods other than additive manufacturing, and the material of the lid 7 is not limited to resin, but may be fabricated using inorganic materials such as metal or ceramic.

[0065] Furthermore, the lid 7 only needs to be shaped to form the non-flat shape of the upper surface of the three-dimensional object 1, and can be shaped to correspond to various shapes of the three-dimensional object 1 being manufactured. In addition, the non-flat shape includes various shapes that include at least one part with a difference in height. Furthermore, in the above embodiment, the lid 7 was fitted inside the upper opening of the shell 4, but in another embodiment, the outer periphery of the lid 7 may be locked to the upper opening of the shell 4.

[0066] Furthermore, in the lid attachment process, the lid 7 was placed over the shell 4 after it was removed from the build plate 15 following the core material filling process. However, in another configuration, the lid 7 may be placed over the shell 4 before it is removed from the build plate 15, that is, while the shell 4 is still on the build plate 15, and then the shell 4 with the lid 7 on it may be removed from the build plate 15.

[0067] Furthermore, although the above embodiment described the case where the shell material 2 used to form the shell 4 is a liquid phase material, the formation of the shell 4 is not limited to a method of curing the liquid phase material (liquid bath polymerization), and other additive manufacturing methods such as fused deposition modeling may also be applied. Furthermore, the core material 6 may be a curable material other than a thermosetting resin, provided that it can be cured in one go after being filled into the core portion 5.

[0068] The present invention is widely applicable in the field of additive manufacturing technologies such as 3D printers. By applying the present invention to such fields, it becomes possible not only to prototype but also to mass-produce parts and products that require lightweight and high strength, such as parts used in various industrial equipment such as automobiles, aircraft, and robots, as well as nursing care products and sporting goods. [Explanation of Symbols]

[0069] 1 Three-dimensional object 2 Shell material 3. Cured UV-cured resin layer 4 Shells 5. Core 6 Core material 6a Hardened core material 7 Lid 7a Hole 8. Support Department 9 Air 10 Three-dimensional modeling device 11 Modeling tank 12 Laser Optics 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 nozzles 15. Build Table 16 Heat curing means 17 Tools 50, 60 Three-dimensional object 51 Shells 52 Core section 53 Core material 61, 62 Three-dimensional objects 61a, 62a top surface

Claims

1. The shell molding process involves creating a shell using shell material to form the shape of the part of a three-dimensional object excluding the top surface, A core material filling step is performed in which a core material, which is a liquid phase material, is filled into the core portion, which is the part enclosed by the shell. A method for creating a three-dimensional object, comprising a core material hardening step for hardening the core material within the core portion, A method for creating a three-dimensional object, characterized by including a lid attachment step, which involves placing a lid that forms the non-flat shape of the upper surface of the three-dimensional object on the upper surface of the core material filled in the core portion, prior to the core material hardening step.

2. The method for creating a three-dimensional object according to claim 1, characterized in that it includes a lid fabrication step of fabricating the lid prior to the lid attachment step.

3. The method for creating a three-dimensional object according to claim 2, characterized in that the shell forming step and the lid forming step are carried out using a liquid bath polymerization method in a forming tank in which the shell material is stored.

4. The method for creating a three-dimensional object according to claim 2 or 3, characterized in that a transparent liquid phase material is used for the shell material.

5. The aforementioned cover has a hole, In the lid attachment process, The method for creating a three-dimensional object according to any one of claims 1 to 3, characterized in that the lid is placed over the upper surface of the core material while the air trapped between the upper surface of the core material and the lid is released from the hole.

6. After the core material hardening process, The method for creating a three-dimensional object according to any one of claims 1 to 3, characterized in that it includes a separation step of separating at least a portion of the shell and the lid from the hardened core material.

Images