Method for creating three-dimensional shapes, and apparatus for creating three-dimensional shapes.

Abstract

To provide a three-dimensional printing method that can prevent defects in the printing of the three-dimensional object, in a so-called core-shell type three-dimensional printing method. [Solution] A method for creating a three-dimensional object, comprising: a shell forming step of forming a shell 4, which is the outer shell layer of a three-dimensional object, in a forming tank 11 where shell material 2 is stored, by liquid tank polymerization; and a core material filling step of filling a core portion 5, which is the part surrounded by the shell 4, with a core material 6, which is a liquid phase material, using a nozzle 14 to replace the shell material 2, wherein after filling the core portion 5 with the core material 6, when the nozzle 14 is pulled up from inside the core portion 5, the method includes a stringing suppression step to suppress the formation height of the stringing portion 6a of the core material 6 that is formed from the interface of the core material 6 to the tip of the nozzle 14.

Description

Technical Field

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

Background Art

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

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

[0004] The three-dimensional shaping method described in Patent Document 1 is characterized in that after repeatedly shaping a shell and filling a core material in a shaping 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 shaping method (hereinafter, this method is also referred to as a core-shell shaping method), since there is no lamination interface in the cured portion of the core material, it is possible to shape a three-dimensional object having no directionality in rigidity and strength. [Problems to be Solved by the Invention]

[0005] However, the core-shell 3D printing method described above had some areas that needed improvement to prevent defects in the printed 3D objects. These points will be explained in detail below. Figures 9(a) to 9(g) show the key parts of the intermediate steps in creating a three-dimensional object using the core-shell 3D printing method described above.

[0006] Figure 9(a) shows a scene from the process (core material filling process) in which the core portion 5, which is the part enclosed by the shell 4, is filled with core material 6, which is a liquid phase material, using a nozzle 14. The shell 4 forms the outer shell layer of the three-dimensional object. It is formed by irradiating a portion of the shell material 2 with ultraviolet laser light 12c on a build plate 16 located in a build tank where the shell material 2 is stored, thereby curing the shell material 2.

[0007] The core material filling process, as shown in Figure 9(a), involves inserting a nozzle 14 into the core portion 5, discharging core material 6 from the tip of the nozzle 14, and filling the core portion 5 with core material 6. Since core material 6 has a higher specific gravity than shell material 2, the core material 6 is filled into the core portion 5 while replacing the shell material 2 inside the core portion 5 with the core material 6 discharged from the nozzle 14.

[0008] Once the core material 6 has been filled into the core portion 5, the nozzle 14 is pulled up from inside the core portion 5 in a substantially vertical direction, as shown in Figure 9(b). At this time, the core material 6 near the tip of the nozzle 14 is lifted along with the nozzle 14, and a stringy portion 6a of the core material 6 extending in a whisker-like manner from the interface of the core material 6 to the tip of the nozzle 14 may be formed.

[0009] After the nozzle 14 is raised, as shown in Figures 9(c) and (d), the build plate 16 is lowered to a predetermined height (for example, a predetermined percentage of the curing depth), and then the ricoter 18, which is a liquid surface leveling tool, is moved horizontally with its tip slightly submerged in the liquid surface of the shell material 2, thereby leveling the liquid surface of the shell material 2 with the ricoter 18. As shown in Figure 9(c), if a stringy portion 6a is formed in the core material 6, the recoater 18 scrapes off a portion of the stringy portion 6a, and as shown in Figure 9(d), the scraped portion of the stringy portion 6b is leveled on the liquid surface of the shell material 2.

[0010] Next, a process is carried out to create a new shell 4 on top of the shell 4 filled with core material 6. In this process, as shown in Figures 9(e) and (f), if the stringy portion 6b is present in a leveled state at the liquid surface of the shell material 2 into which the new shell 4 is created by irradiating it with ultraviolet laser light 12c, the stringy portion 6b will be incorporated into the interior of the newly created shell 4.

[0011] After the new shell 4 is fabricated, as shown in Figure 9(g), the core material 6 is filled into the core portion 5, which is the part surrounded by the newly fabricated shell 4, using the nozzle 14. The same process as above is repeated until the shell 4 filled with core material 6 is removed from the fabrication tank, and thermal energy is applied to the shell 4 filled with core material 6 to harden the core material 6 all at once. At this time, the stringy portion 6b contained within the shell 4 also hardens.

[0012] As described above, in conventional core-shell molding methods, after the core material 6 is filled into the core 5, when the nozzle 14 is pulled up from inside the core 5, a stringing portion 6a of the core material 6 may be formed. This formation of the stringing portion 6a can cause molding defects, such as a part of the core material 6, i.e., the stringing portion 6b, being mixed into the shell 4. [Prior art documents] [Patent Documents]

[0013] [Patent Document 1] Japanese Patent Publication No. 2019-136923 [Overview of the Initiative] Means for solving the problem and their effects

[0014] The present invention has been made in view of the above problems, and aims to provide a three-dimensional molding method and a three-dimensional molding apparatus that can prevent the occurrence of molding defects in the three-dimensional object being molded.

[0015] To achieve the above objective, the three-dimensional molding method (1) according to the present invention is: The shell fabrication process involves fabricating the shell, which is the outer shell layer of a three-dimensional object, in a molding tank where the shell material is stored using a liquid bath polymerization method. A method for creating a three-dimensional object, comprising a core material filling step 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, using a nozzle to replace the shell material, The present invention is characterized by including a stringing suppression step, which suppresses the formation height of the stringing portion of the core material that is formed from the interface of the core material to the tip of the nozzle when the nozzle is pulled up from the core after the core material has been filled into the core portion.

[0016] According to the above three-dimensional molding method (1), since the stringing suppression step is included, when the nozzle is pulled up from the core after the core material has been filled into the core, the height of the stringing portion of the core material that is formed from the interface of the core material to the tip of the nozzle is suppressed. Therefore, in the shell molding process, when leveling the liquid surface of the shell material using a liquid leveling tool, it is possible to prevent the stringy portion of the core material from being scraped together with the shell material, and to prevent the stringy portion of the core material from being mixed into the shell. Thus, it is possible to prevent the occurrence of molding defects in the three-dimensional molded object caused by the stringy portion of the core material.

[0017] Furthermore, the three-dimensional molding method (2) according to the present invention is, in the three-dimensional molding method (1) described above, The shell forming process and the core material filling process are repeatedly performed. The method is characterized in that the stringing suppression step is performed each time the nozzle is pulled out of the core after the core material filling step is completed.

[0018] According to the above-described three-dimensional molding method (2), the shell molding step and the core material filling step are repeatedly performed, and the stringing suppression step is performed each time the core material filling step is completed and the nozzle is pulled out from the core. This prevents the stringing portion of the core material from being mixed into the shell which is molded in multiple stages. Therefore, even when molding large objects or objects with complex shapes, for example, it is possible to prevent defects in the three-dimensional molded object caused by the stringing portion of the core material.

[0019] Furthermore, the three-dimensional molding method (3) according to the present invention is characterized in that, in the three-dimensional molding method (1) or (2) above, the stringing suppression step includes a step of operating the nozzle so as to suppress the height of the stringing portion formed in the core material.

[0020] According to the above three-dimensional molding method (3), the stringing suppression step includes a step of operating the nozzle to suppress the formation height of the stringing portion of the core material. As a result of operating the nozzle, the shape of the stringing portion is flattened, and the formation height of the stringing portion can be kept low. Therefore, it is possible to more reliably prevent the occurrence of molding defects in the three-dimensional molded object caused by the stringing portion of the core material. The steps for operating the nozzle may include, for example, a step of moving the nozzle back and forth in a zigzag pattern on a horizontal plane with the tip of the nozzle positioned slightly above the interface of the core material, a step of rotating the nozzle in a spiral pattern on a horizontal plane, a step of pulling up the nozzle while moving it back and forth in a zigzag pattern, or a step of pulling up the nozzle while rotating it in a spiral pattern. The steps for operating the nozzle may also include a step of moving the nozzle back and forth up and down so that the tip of the nozzle presses against the stringing portion of the core material.

[0021] Moreover, the three-dimensional shaping method (4) according to the present invention is characterized in that, in any one of the above three-dimensional shaping methods (1) to (3), the thread drawing suppression step includes a step of discharging the shell material from above the thread drawing portion of the core material after pulling up the nozzle from within the core portion.

[0022] According to the above three-dimensional shaping method (4), since the thread drawing suppression step includes a step of discharging the shell material from above the thread drawing portion of the core material after pulling up the nozzle from within the core portion, the shape of the thread drawing portion is flattened by the shell material discharged from above the thread drawing portion of the core material, and the formation height of the thread drawing portion can be suppressed to be low. Therefore, it is possible to more reliably prevent the occurrence of molding defects in the three-dimensional shaped object due to the thread drawing portion of the core material.

[0023] Moreover, the three-dimensional shaping method (5) according to the present invention is characterized in that, in any one of the above three-dimensional shaping methods (1) to (4), the thread drawing suppression step includes a step of sucking at least a part of the thread drawing portion of the core material with the nozzle.

[0024] According to the above three-dimensional shaping method (5), since the thread drawing suppression step includes a step of sucking at least a part of the thread drawing portion of the core material with the nozzle, the volume of the thread drawing portion can be reduced by the step of sucking with the nozzle, and the formation height of the thread drawing portion of the core material can be suppressed to be low. Therefore, it is possible to more reliably prevent the occurrence of molding defects in the three-dimensional shaped object due to the thread drawing portion of the core material.

[0025] Moreover, the three-dimensional shaping apparatus (1) according to the present invention is a three-dimensional shaping apparatus used in any one of the above three-dimensional shaping methods (1) to (5), a shell shaping system for shaping the shell, which is the outer shell layer of the three-dimensional shaped object, in the shaping tank in which the shell material is stored by the liquid tank polymerization method; and a core material filling system for filling the core portion, which is the portion surrounded by the shaped shell, with the core material, which is a liquid phase material, using the nozzle. The nozzle is characterized in that at least its tip is treated with a surface treatment that suppresses the adhesion of the core material.

[0026] According to the above-described three-dimensional molding apparatus (1), at least the tip of the nozzle is treated with a surface treatment that suppresses adhesion of the core material. Therefore, when the nozzle is pulled up from the core after the core material has been filled into the core, the core material is more easily separated from the nozzle, reducing the amount of core material that is lifted together with the nozzle, and keeping the height of the stringy portion of the core material low. Thus, the effect of preventing molding defects in three-dimensional molded objects caused by the stringy portion of the core material can be enhanced. [Brief explanation of the drawing]

[0027] [Figure 1] This 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 Embodiment (1) of the present invention. [Figure 2] (a) to (c) are diagrams illustrating the first shell fabrication step and core material filling step in the three-dimensional fabrication method according to Embodiment (1). [Figure 3] (a) to (f) are diagrams illustrating an example of a stringing suppression process in the three-dimensional molding method according to Embodiment (1). [Figure 4] Figures (a) to (f) illustrate the second shell fabrication step and core material filling step in the three-dimensional fabrication method according to Embodiment (1). [Figure 5] (a) to (c) are diagrams illustrating an example of another stringing suppression process. [Figure 6] (a) to (c) are diagrams illustrating yet another example of a stringing suppression process. [Figure 7] This is a schematic diagram showing an example of the configuration of a three-dimensional modeling apparatus used in the three-dimensional modeling method according to Embodiment (2). [Figure 8] (a) to (c) are diagrams illustrating an example of a stringing suppression process in the three-dimensional molding method according to Embodiment (2). [Figure 9] Figures (a) to (g) show the key parts of the intermediate steps in creating a three-dimensional object using the conventional core-shell 3D printing method. [Modes for carrying out the invention]

[0028] The embodiments of the three-dimensional molding method and three-dimensional molding apparatus according to the present invention will be described below with reference to the drawings. The forms of the three-dimensional molded objects shown in the drawings are schematic representations intended to facilitate understanding of the present invention, and are not limited to these forms.

[0029] Figure 1 is a schematic diagram showing an example of the configuration of a three-dimensional modeling apparatus used in the three-dimensional modeling method according to Embodiment (1). In the following description, one direction of the horizontal plane is defined as the X-axis direction, the direction perpendicular to this in 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.

[0030] The 3D printing apparatus 10 functions as a composite material 3D printer and primarily comprises a build tank 11 where molding is performed by liquid bath polymerization (also known as stereolithography), a laser optical system 12, and a core material supply system 13. In addition, a thermosetting means 17 is used in the 3D printing method according to this embodiment. The shell molding system is configured including the build tank 11 and the laser optical system 12, and the core material filling system is configured including the core material supply system 13. Including these, an apparatus capable of fabricating 3D objects using a core-shell molding method is configured.

[0031] Inside the build tank 11, a shell material 2, such as a photocurable resin which is a liquid phase material, is stored, and 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 ultraviolet curing resins such as epoxy or acrylic resins can be used. A build platform 16 is provided inside the build tank 11. The build platform 16 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).

[0032] Furthermore, a ricochet 18, which serves as a liquid leveling tool, is positioned near the upper opening of the molding tank 11, and the ricochet 18 is movable in the XYZ axis directions in the figure by a ricochet movement mechanism 19. The ricochet movement mechanism 19 is configured to include, for example, a robot capable of moving the ricochet 18 in at least the XYZ directions, such as a 3-axis combination robot.

[0033] 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.

[0034] 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.

[0035] Therefore, by positioning the upper surface of the build plate 16 at a depth submerged by a predetermined height (for example, a predetermined percentage of the curing depth) from the liquid surface of the shell material 2, leveling the liquid surface of the shell material 2 with the recoater 18, and then irradiating an ultraviolet laser beam 12c at an arbitrary 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 16. Subsequently, by lowering the build plate 16 by a predetermined percentage of the curing depth, leveling the liquid surface of the shell material 2 with the recoater 18, and then irradiating an ultraviolet laser beam 12c at an arbitrary position on the liquid surface of the shell material 2, a new cured ultraviolet-curable resin layer 3 is laminated on top of the cured ultraviolet-curable resin layer 3.

[0036] Then, by repeatedly performing the lowering motion of the build plate 16 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 fabricate a shell 4 (see Figure 2) having a three-dimensional shape. In this embodiment, the object formed by hardening the shell material 2 in this manner is called the shell 4. The shell 4 forms the outer shell layer of the three-dimensional object, and the portion of the shell 4 surrounded by its inner surface that has a bottom surface is called the core portion 5 (see Figure 2).

[0037] 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, a nozzle 14 attached to the outlet of the piping system 13d, and a nozzle moving mechanism 15 for moving the nozzle 14.

[0038] The core material supply system 13 is configured to drive a pump 13b to supply core material 6 from the core material tank 13a to the nozzle 14 via 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 diameter small enough to prevent clogging of the core material 6. The nozzle 14 may be made of metal such as stainless steel, or of a flexible resin.

[0039] Furthermore, at least the tip of the nozzle 14 is treated with a surface treatment to suppress adhesion of the core material 6 and shell material 2. The surface treatment includes various surface treatments that can impart release properties (non-adhesion), and includes, for example, coating treatments using resins such as fluorine or silicone, nanoparticles, other liquid repellents, liquid repellent paints, water-repellent plating treatments such as electroless nickel plating, surface processing treatments that form fine irregularities on the surface, or combinations thereof. In addition to being applied to the outer circumferential surface of the nozzle 14, the surface treatment may also be applied to the inner circumferential surface (inside the nozzle hole) of the nozzle 14. By applying the surface treatment to the inner circumferential surface of the nozzle 14, it is possible to further improve the release properties of the core material 6.

[0040] The nozzle movement mechanism 15 includes, for example, a robot capable of moving and fixing the nozzle 14 in at least the XYZ directions, such as a 3-axis combination robot. Therefore, the piping system 13d is made of a flexible structure and material so as to follow the movement of the nozzle 14.

[0041] 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.

[0042] The thermosetting means 17 is used in the process of curing the core material 6 filled in the core portion 5 (core material curing process), and consists of a heating furnace having a sealable chamber. The thermosetting means 17 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.

[0043] The operation of each part of the 3D printing apparatus 10 (the build plate 16, the recoater 18, the laser optical system 12, and the core material supply system 13) 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 programs for controlling the operation of each part of the 3D printing apparatus 10, 3D shape data (CAD data) of the 3D object to be printed, and various other setting data necessary for printing. The arithmetic processing unit executes processes to control the operation of each part of the 3D printing apparatus 10 based on the programs.

[0044] Next, an example of the three-dimensional molding method according to Embodiment (1) will be described using Figures 2 to 4. The three-dimensional molding method according to Embodiment (1) includes a shell molding step, a core material filling step, and a stringing suppression step. The aforementioned shell fabrication process is a process of fabricating the shell 4, which is the outer shell layer of the three-dimensional object, in a fabrication tank 11 where the shell material 2 is stored, by liquid tank polymerization. The core material filling process involves filling the core portion 5, which is the part enclosed by the shell 4, with core material 6 using a nozzle 14, replacing the shell material 2. The stringing suppression step is a step to suppress the height of the stringing portion 6a of the core material 6 that is formed from the interface of the core material 6 to the tip of the nozzle 14 when the nozzle 14 is pulled up from inside the core portion 5 after the core material 6 has been filled into the core portion 5. The three-dimensional molding method according to embodiment (1) further includes a core material hardening step of hardening the core material 6 within the core portion 5.

[0045] The three-dimensional molding method described below divides the shell molding process and the core material filling process into two steps and repeats them, and the stringing suppression process is performed each time the core material filling process is completed.

[0046] Figures 2(a) to 2(c) are diagrams illustrating the first shell fabrication step and core material filling step included in the three-dimensional fabrication method according to Embodiment (1), and are enlarged partial cross-sectional views of the peripheral area of ​​the build plate 16.

[0047] The aforementioned shell forming process, as shown in Figure 2(a), is a process of forming a shell 4 by hardening a portion of the shell material 2 in a forming tank 11 where the shell material 2 is stored. More specifically, the shell fabrication process involves moving the nozzle 14 out of 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 on the fabrication table 16 by irradiating the liquid surface of the shell material 2 with light using the laser optical system 12 and by lowering the fabrication table 16 and leveling the liquid surface of the shell material 2 with the recoater 18.

[0048] In other words, in the shell fabrication process, based on the three-dimensional shape data of the shell 4, the following operations are performed alternately: scanning and irradiating the liquid surface of the shell material 2 on the build plate 16 with ultraviolet laser light 12c, and lowering the build plate 16 by a predetermined percentage of the curing depth and leveling the liquid surface of the shell material 2 with a recoater 18. Through these operations, the shell 4 is fabricated on the build plate 16. Note that the shell 4 shown in Figure 2 is fabricated in the shape of a bottomed box with an opening on the top surface.

[0049] After the first shell 4 is fabricated, with the shell 4 positioned below the liquid level of the shell material 2 in the fabrication tank 11, the first core material filling process shown in Figures 2(b) and 2(c) is then performed. The core material filling process involves inserting a nozzle 14 into the core section 5 where the shell material 2 is located, with the shell 4 positioned below the liquid level of the shell material 2 in the molding tank 11, discharging core material 6 from the tip of the nozzle 14, and filling the core section 5 with core material 6 while at least the tip of the nozzle 14 is inserted into the discharging core material 6, replacing the shell material 2 with core material 6. The filling of core material 6 may also be performed by moving the nozzle 14 in the horizontal (XY axis) and vertical (Z axis) directions within the core section 5 using a nozzle moving mechanism 15.

[0050] As shown in Figure 2(b), 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, and the shell material 2 is present in the core section 5 before the core material 6 is filled. 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 in the core section 5 is pushed up and pushed out of the shell 4 through the upper opening of the shell 4, and the inside of the core section 5 is replaced from the shell material 2 to the core material 6.

[0051] Then, as shown in Figure 2(c), after filling the core portion 5, which is the part surrounded by the inner surface of the first shell 4, with a predetermined amount of core material 6, the discharge of core material 6 from the nozzle 14 is stopped, completing the first core material filling process, and then the first stringing suppression process is performed.

[0052] Figures 3(a) to 3(f) illustrate an example of the stringing suppression process. The stringing suppression step shown in Figure 3 includes the step of operating the nozzle 14 to suppress the height of the stringing portion 6a formed in the core material 6. First, after stopping the discharge of the core material 6 from the nozzle 14, the control unit controls the operation of the nozzle movement mechanism 15 to raise the nozzle 14 to a position where the tip of the nozzle 14 is slightly above the interface of the core material 6 within the core portion 5 (Figure 3(a)). At this time, a slightly raised stringy portion 6a is formed from the interface of the core material 6 to the tip of the nozzle 14.

[0053] Next, the control unit controls the operation of the nozzle movement mechanism 15 to perform a stringing suppression operation by the nozzle 14. Various forms of this stringing suppression operation are possible. For example, the stringing suppression operation may be an operation in which the nozzle 14 is moved back and forth in a zigzag pattern on the horizontal plane (XY plane) inside the core part 5, as shown in Figure 3(b), or an operation in which the nozzle 14 is rotated in a spiral pattern on the horizontal plane inside the core part 5, as shown in Figure 3(c).

[0054] Furthermore, the stringing suppression operation may be performed by raising the nozzle 14 while moving it back and forth in a zigzag pattern, as shown in Figure 3(d), or by raising the nozzle 14 while rotating it in a spiral pattern, as shown in Figure 3(e).

[0055] Furthermore, the stringing suppression operation may also be performed by operating the nozzle 14 as shown in Figure 3(b) or Figure 3(c) above, and then operating the nozzle 14 to pull it up as shown in Figure 3(d) or Figure 3(e).

[0056] Then, after the stringing suppression operation by the nozzle 14 as shown in Figures 3(b) to (e), the nozzle 14 is pulled up vertically as shown in Figure 3(f), and the stringing suppression process is completed. At the end of the stringing suppression process, the stringing portion 6a is flattened by the operation of the nozzle 14, and the height of the stringing portion 6a is kept low.

[0057] Next, as shown in Figures 4(a) to 4(f), the second shell molding process and core material filling process are performed. After the stringing suppression process is completed and the nozzle 14 is retracted to a predetermined position, the second shell molding process is performed. First, as shown in Figures 4(a) and (b), the build plate 16 is lowered to a predetermined height (for example, a predetermined percentage of the curing depth), and then the tip of the coater 18 is slightly submerged in the liquid surface of the shell material 2, and the coater 18 is moved horizontally to level the liquid surface of the shell material 2. Because the stringing suppression process described above keeps the height of the stringing portion 6a low, as shown in Figure 4(b), when the recoater 18 levels the liquid surface of the shell material 2, a portion of the stringing portion 6a is not scraped off by the recoater 18. Therefore, the stringing portion 6a is not scraped onto the liquid surface of the shell material 2.

[0058] After leveling the surface of the shell material 2 with the recoater 18, as shown in Figures 4(c) and (d), similar to the first shell fabrication process, the following operations are performed alternately: scanning and irradiating the surface of the shell material 2 with ultraviolet laser light 12c based on the three-dimensional shape data of the shell 4, and lowering the build plate 16 by a predetermined percentage of the curing depth and leveling the surface of the shell material 2 with the recoater 18. Through these operations, as shown in Figure 4(d), a new shell 4 is fabricated on top of the shell 4 fabricated in the first shell fabrication process.

[0059] After the second shell 4 is fabricated, with the shell 4 positioned below the liquid level of the shell material 2 in the fabrication tank 11, the second core material filling process shown in Figures 4(e) and 4(f) is then performed. The second core material filling process is performed in the same manner as the first. That is, with the shell 4 positioned below the liquid level of the shell material 2 in the molding tank 11, the nozzle 14 is inserted into the core section 5 where the shell material 2 is located from above the liquid level of the shell material 2, and then inserted into the previously filled core material 6, after which the core material 6 is discharged from the tip of the nozzle 14.

[0060] Then, as shown in Figure 4(f), after filling the core portion 5, which is the part surrounded by the inner surface of the second shell 4, with a predetermined amount of core material 6, the discharge of core material 6 from the nozzle 14 is stopped, completing the second core material filling process, and then the second stringing suppression process is performed. The second stringing suppression step includes operating the nozzle 14 to suppress the height of the stringing portion 6a formed in the core material 6, and is performed in the same manner as the first stringing suppression step shown in Figures 3(a) to (f).

[0061] After the second stringing suppression step is completed, the nozzle 14 is moved to a predetermined position, the build plate 16 is moved above the liquid level of the shell material 2, the shell 4 filled with core material 6 is removed from the build plate 16, and then the core material hardening step is performed. In the core material hardening process, the shell 4, in which the core material 6 is filled into the core portion 5, which has been removed from the build plate 16, is placed into the heat hardening means 17 to start the heat hardening process of the core material 6. In other words, the shell 4 is placed in the heat curing means 17, and the temperature inside the heat curing means 17 is raised to a temperature higher than the heat curing temperature of the core material 6. This heats up the entire three-dimensional object, including the core material 6 and the shell 4, causing the entire core material 6 to harden all at once. After the entire core material 6 has hardened, the three-dimensional object consisting of the hardened core material 6 and shell 4 is removed from the heat curing means 17, thus completing the core material hardening process. The hardened core material 6 that constitutes the three-dimensional object has no layered interface, and the stringy portion 6a of the core material 6 is not mixed into the outer shell layer 4.

[0062] In the three-dimensional molding method described above, an example was explained in which the shell molding process and the core material filling process were repeated alternately twice. However, depending on the shape of the three-dimensional object to be molded, the shell molding process and the core material filling process may be performed alternately only once, or they may be repeated alternately three or more times. In that case as well, it is preferable to perform the stringing suppression process each time the core material filling process is performed.

[0063] According to the three-dimensional molding method of the above embodiment (1), after filling the core portion 5 with core material 6, the stringing suppression step is performed, and the stringing suppression step includes a step of operating the nozzle 14 to suppress the formation height of the stringing portion 6a of the core material 6. Therefore, when the nozzle 14 is pulled up from inside the core portion 5, the stringing suppression operation by the nozzle 14 keeps the formation height of the stringing portion 6a of the core material 6, which is formed from the interface of the core material 6 to the tip of the nozzle 14, low. Consequently, when leveling the liquid surface of the shell material 2 using the recoater 18 in the shell molding step, it is possible to prevent the stringing portion 6a of the core material 6 from being scraped together with the shell material 2, and it is possible to prevent the stringing portion 6a of the core material 6 from being mixed into the shell 4.

[0064] Furthermore, since the shell molding process and the core material filling process are repeatedly performed, and the stringing suppression process is performed each time the core material filling process is completed and the nozzle 14 is pulled up from the core part 5, it is possible to prevent the stringing portion 6a of the core material 6 from being mixed into the shell 4 which is molded in multiple stages. Therefore, even when molding large objects or objects with complex shapes, for example, it is possible to prevent the occurrence of molding defects in three-dimensional objects caused by the stringing portion 6a of the core material 6.

[0065] Furthermore, according to the three-dimensional molding apparatus 10 of embodiment (1), at least the tip of the nozzle 14 is treated with a surface treatment that suppresses adhesion of the core material 6. Therefore, when the nozzle 14 is pulled up from inside the core part 5 after the core material 6 has been filled into the core part 5, the core material 6 is more likely to separate from the nozzle 14, reducing the amount of core material 6 that is lifted together with the nozzle 14, and thus keeping the height of the stringy portion 6a of the core material 6 low. Consequently, the effect of preventing molding defects in three-dimensional molded objects caused by the stringy portion 6a of the core material 6 can be enhanced.

[0066] In the three-dimensional molding method according to the embodiment (1) described above, the stringing suppression operation by the nozzle 14 shown in Figure 3 was explained as an example of the process of operating the nozzle 14 in the stringing suppression process, but the operation mode of the nozzle 14 is not limited to these. Figure 5 is a diagram illustrating another mode of operation of the nozzle 14 in the stringing suppression process, and the process of operating the nozzle 14 shown in Figure 5 includes the step of moving the nozzle 14 up and down so as to press the tip of the nozzle 14 against the stringing portion 6a of the core material 6.

[0067] After stopping the discharge of the core material 6 from the nozzle 14, as shown in Figure 5(a), the control unit controls the operation of the nozzle movement mechanism 15 to raise the nozzle 14 to a position where the tip of the nozzle 14 is above the liquid surface of the shell material 2. At this time, a stringy portion 6a is formed, which is raised from the interface of the core material 6 to the tip of the nozzle 14.

[0068] Subsequently, as shown in Figure 5(b), the control unit controls the operation of the nozzle movement mechanism 15 to move the nozzle 14 up and down reciprocally so that the tip of the nozzle 14 presses against the stringing portion 6a of the core material 6. Then, as shown in Figure 5(c), the nozzle 14 is pulled up and moved to a predetermined position. The reciprocating movement may be performed once or two or more times. The pressing action of the nozzle 14 against the stringing portion 6a due to the reciprocating movement keeps the height of the stringing portion 6a low. According to the stringing suppression process of the other form described above, the same effect as the stringing suppression process shown in Figure 3 can be obtained.

[0069] Furthermore, Figure 6 is a diagram illustrating yet another form of the stringing suppression process, which includes a step of sucking at least a portion of the stringing portion 6a of the core material 6 with a nozzle 14. After stopping the discharge of the core material 6 from the nozzle 14, as shown in Figure 6(a), the control unit controls the operation of the nozzle movement mechanism 15 to raise the nozzle 14 to a position where its tip is above the liquid surface of the shell material 2. At this time, a stringy portion 6a is formed, which is raised from the interface of the core material 6 to the tip of the nozzle 14.

[0070] Subsequently, as shown in Figure 6(b), the control unit controls the operation of the nozzle moving mechanism 15 and the pump 13b to slowly lower the nozzle 14 to near the interface of the core material 6, while performing a suction operation to suck up at least a portion of the stringing portion 6a with the nozzle 14. Then, as shown in Figure 6(c), the nozzle 14 is raised and retracted to a predetermined position. Due to the suction operation, at least a portion of the stringing portion 6a is sucked up, and the height of the formation of the stringing portion 6a is kept low. After retracting the nozzle 14 to a predetermined position, it is preferable to perform a test run of the core material 6 from the nozzle 14 and discharge the sucked-up core material 6 and shell material 2.

[0071] According to the stringing suppression process of the other embodiment described above, the process includes a step of sucking at least a portion of the stringing portion 6a of the core material 6 with a nozzle 14. By sucking at least a portion of the stringing portion 6a with the nozzle 14, the volume of the stringing portion 6a of the core material 6 is reduced, and the height of the stringing portion 6a of the core material 6 can be reliably lowered. In particular, when the stringing portion 6a is formed near the boundary with the shell 4, the height of the stringing portion 6a can be reliably lowered without the stringing portion 6a being pushed out onto the upper surface portion of the shell 4. Therefore, the occurrence of molding defects in the three-dimensional molded object caused by the stringing portion 6a of the core material 6 can be more reliably prevented.

[0072] Next, a three-dimensional molding method according to embodiment (2) and a three-dimensional molding apparatus used in said three-dimensional molding method will be described. Figure 7 is a schematic diagram showing an example of the configuration of the 3D printing apparatus 10A used in the 3D printing method according to embodiment (2). Components having the same function as the 3D printing apparatus 10 according to embodiment (1) shown in Figure 1 are denoted by the same reference numerals, and their descriptions are omitted.

[0073] The 3D modeling apparatus 10A according to embodiment (2) differs from the 3D modeling apparatus 10 according to embodiment (1) shown in Figure 1 in that it is further equipped with a shell material supply system 20 that discharges shell material into the molding tank 11. The shell material supply system 20 includes a nozzle 21 for discharging shell material 2a (see Figure 8), a nozzle moving mechanism 22 for moving the nozzle 21, and a piping system 23 connected to the nozzle 21. Furthermore, it includes a pump located in the middle of the piping system 23 and a shell material tank to which the piping system 23 is connected (neither of which are shown).

[0074] The nozzle movement mechanism 22 includes, for example, a robot capable of moving and fixing the nozzle 21 in at least the XYZ directions, such as a 3-axis combination robot. Therefore, the piping system 23 is made of a flexible structure and material so as to follow the movement of the nozzle 21. The operation of each part of the shell material supply system 20 is controlled by the control unit (not shown).

[0075] The difference between the three-dimensional molding method using the three-dimensional molding apparatus 10A according to Embodiment (2) and the three-dimensional molding method using the three-dimensional molding apparatus 10 according to Embodiment (1) described above lies in the content of the stringing suppression process. Since the shell molding process and the core material filling process are basically the same, only the content of the stringing suppression process, which is the only difference, will be explained here.

[0076] Figures 8(a) to 8(c) illustrate an example of a stringing suppression process in the three-dimensional molding method according to Embodiment (2). The stringing suppression step shown in Figure 8 includes the step of pulling up the nozzle 14 from inside the core 5 and then dropping the shell material 2a from above the stringing portion 6a of the core material 6. The shell material 2a is the same liquid phase material as the shell material 2 stored in the molding tank 11.

[0077] After the core material filling process has finished discharging the core material 6, as shown in Figure 8(a), the control unit controls the operation of the nozzle moving mechanism 15 to pull up the nozzle 14 and retract the nozzle 14 to a predetermined position. At this time, a stringy portion 6a is formed, which is raised from the interface of the core material 6 to the tip of the nozzle 14. Subsequently, the control unit controls the operation of the nozzle movement mechanism 22 to move the nozzle 21 for discharging the shell material 2a to the raised position of the nozzle 14, that is, above the stringing portion 6a of the core material 6.

[0078] Subsequently, as shown in Figure 8(b), the control unit controls the operation of the pump in the shell material supply system 20 to discharge the shell material 2a from the nozzle 21. The shell material 2a discharged from the nozzle 21 falls onto the stringing portion 6a of the core material 6, and the shape of the pointed tip of the stringing portion 6a is disrupted by the falling shell material 2a, causing the stringing portion 6a to become flattened. After a predetermined amount of shell material 2a is discharged from the nozzle 21, the control unit controls the operation of the nozzle movement mechanism 22 to move the nozzle 21 to a predetermined position, as shown in Figure 8(c), thereby completing the stringing suppression process.

[0079] According to the three-dimensional molding method of embodiment (2), the stringing suppression step includes the step of dropping the shell material 2a from above the stringing portion 6a of the core material 6 after pulling up the nozzle 14 from inside the core portion 5. As a result, the shell material 2a discharged from above the stringing portion 6a of the core material 6 flattens the stringing portion 6a, and the height of the stringing portion 6a can be reduced. Therefore, as with embodiment (1), it is possible to reliably prevent the occurrence of molding defects in the three-dimensional molded object caused by the stringing portion 6a of the core material 6.

[0080] 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. For example, as a first modified example, the stringing suppression step may be a step that combines the steps of operating the nozzle 14 to suppress the formation height of the stringing portion 6a of the core material 6 shown in Figures 3 and 5, and the steps of pulling up the nozzle 14 from inside the core portion 5 shown in Figure 8, and then dropping the shell material 2a from above the stringing portion 6a of the core material 6.

[0081] Furthermore, as a second modified example, the stringing suppression step may be a step that combines the steps of using a nozzle 14 to suck up at least a portion of the stringing portion 6a of the core material 6 shown in Figure 6, and the steps of pulling up the nozzle 14 from inside the core portion 5 shown in Figure 8, and then dropping the shell material 2a from above the stringing portion 6a.

[0082] Furthermore, as a third modified example, the stringing suppression step may be a step that combines the step of sucking at least a portion of the stringing portion 6a of the core material 6 shown in Figure 6 with the nozzle 14, and the step of operating the nozzle 14 to suppress the formation height of the stringing portion 6a shown in Figures 3 and 5.

[0083] Further, as a fourth modification example, the thread drawing suppression step may be a combination of a step of sucking at least a part of the thread drawing portion 6a of the core material 6 shown in FIG. 6 with the nozzle 14, a step of operating the nozzle 14 so as to suppress the formation height of the thread drawing portion 6a shown in FIGS. 3 and 5, and a step of dropping the shell material 2a from above the thread drawing portion 6a after pulling up the nozzle 14 from within the core portion 5 shown in FIG. 8.

[0084] Furthermore, as a fifth modification example, the thread drawing suppression step may be a step of once pulling up the nozzle 14 in the Z-axis direction as shown in FIG. 5(a), then shifting the nozzle 14 in the X-axis or Y-axis direction and then reinserting the nozzle 14 into the liquid surface of the shell material 2, and then moving the nozzle 14 in the X-axis or Y-axis direction. By such a step, by causing the tip of the nozzle 14 to approach and pass through the thread drawing portion 6a from the side of the thread drawing portion 6a, it becomes possible to expand the thread drawing portion 6a in the XY direction and suppress the formation height of the thread drawing portion 6a.

[0085] The present invention can be widely applied in the field of additive manufacturing technologies such as 3D printers. By applying the present invention in such a field, for example, it becomes possible not only to prototype but also to mass-produce parts used in various industrial equipment such as automobiles, airplanes, and robots, nursing care products, sports products, etc., particularly parts and products that require light weight and high strength.

Explanation of Reference Numerals

[0086] 2, 2a Shell material 3 Cured ultraviolet curable resin layer 4 Shell 5 Core portion 6 Core material 6a, 6b Thread drawing portion 10, 10A Stereolithography apparatus 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 nozzles 15. Nozzle movement mechanism 16. Build Table 17 Heat curing means 18 Ricohta 19. Recoater Movement Mechanism 20. Shell material supply system 21 nozzles 22 Nozzle movement mechanism 23 Piping Systems

Claims

1. The shell fabrication process involves fabricating the shell, which is the outer shell layer of a three-dimensional object, in a molding tank where the shell material is stored using a liquid bath polymerization method. A method for creating a three-dimensional object, comprising a core material filling step 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, using a nozzle to replace the shell material, A method for creating three-dimensional shapes, characterized by including a stringing suppression step to suppress the formation height of the stringing portion of the core material that is formed from the interface of the core material to the tip of the nozzle when the nozzle is pulled up from the core after the core material has been filled into the core portion.

2. The shell forming process and the core material filling process are repeatedly performed. The method for creating a three-dimensional object according to claim 1, characterized in that the stringing suppression step is performed each time the nozzle is pulled up from the core after the core material filling step is completed.

3. The stringing suppression process is The method for creating a three-dimensional object according to claim 1 or 2, characterized in that it includes a step of operating the nozzle to suppress the height of the formation of the stringy portion of the core material.

4. The stringing suppression process is The method for creating a three-dimensional object according to claim 1 or 2, characterized in that it includes the step of pulling up the nozzle from inside the core portion and then discharging the shell material from above the stringing portion of the core material.

5. The stringing suppression process is The method for creating a three-dimensional object according to claim 1 or 2, characterized in that it includes the step of sucking at least a portion of the stringy portion of the core material with the nozzle.

6. A three-dimensional modeling apparatus used in the three-dimensional modeling method described in claim 1, A shell fabrication system for fabricating the shell, which is the outer shell layer of the three-dimensional object, in a fabrication tank where the shell material is stored by the liquid tank polymerization method, The system comprises a core material filling system that fills the core portion, which is the part enclosed by the molded shell, with the core material, which is a liquid phase material, using the nozzle, A three-dimensional molding apparatus characterized in that at least the tip of the nozzle is subjected to a surface treatment that suppresses adhesion of the core material.

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