Manufacturing method of additive manufacturing object

Abstract

To provide a laminated molded object production method capable of easily clogging an opening part with a plug by sintering without requiring a welding operation.SOLUTION: A laminated molded object production method has: a precursor formation step S1 in which a liquid binder is jetted to a powder layer to form a solidified layer, and the sequentially formed solidified layers are then laminated to form a precursor 10 having an opening part 12 in communication with an internal space 11; a plug formation step S2 for forming a plug 20 assemblable to the opening part 12; a powder removing step S3 in which unsolidified powder remaining at the internal space 11 is removed from the opening part 12; a binder coating step S4 in which, after the removal of the unsolidified powder, an outer circumferential wall of the plug 20 is coated with the liquid binder; an assembly step S5 in which the plug 20 is assembled to the opening part 12 so that the outer circumferential wall of the plug 20 is brought into contact with an inner circumferential wall of the opening part 12; and a sintering step S6 for sintering the precursor 10 with the plug 20 assembled into the opening part 12.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a layered object. [Background technology]

[0002] In recent years, methods for manufacturing additively manufactured objects have been used, in which a liquid binder is sprayed onto a powder layer to form a solidified layer, and the solidified layers are then stacked to produce a three-dimensional object. Patent Document 1 listed below describes a method for manufacturing additively manufactured objects, including the steps of stacking metal powder to form a molded object having an opening communicating with a hollow interior space, discharging the metal powder remaining in the interior space after the molded object has been formed through the opening, attaching a plug to the opening, and welding the plug attached to the opening to the molded object. According to this manufacturing method, after discharging the unsolidified metal powder remaining in the interior space, the opening can be closed by welding the plug attached to the opening to the molded object. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-161460 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the manufacturing method described in Patent Document 1 above has the following problems. The plug cannot be welded to a shaped object before sintering because the plug must be welded to the shaped object after sintering. Furthermore, the additional step of welding the plug to the shaped object increases manufacturing costs and man-hours.

[0005] The present invention has been made to solve these technical problems, and aims to provide a method for manufacturing an additive manufacturing object in which an opening can be easily closed with a plug by sintering, without requiring welding work. [Means for solving the problem]

[0006] The method for manufacturing an additive manufacturing product according to the present invention is characterized by including: a precursor formation process in which a precursor of an additive manufacturing product having an opening communicating with a hollow internal space is formed by spraying a liquid binder onto a powder layer to form a solidified layer and stacking the formed solidified layers; a plug formation process in which a plug that can be assembled to the opening is formed; a powder removal process in which unsolidified powder remaining in the internal space of the precursor is removed from the opening to the outside of the precursor; a binder application process in which, after the unsolidified powder has been removed, the liquid binder is applied to at least one of the inner wall of the opening and the outer wall of the plug; an assembly process in which the plug is assembled to the opening so that the inner wall of the opening and the outer wall of the plug are in contact with each other; and a sintering process in which the precursor with the plug assembled to the opening is sintered.

[0007] In the method for manufacturing a layered object according to the present invention, unsolidified powder remaining in the internal space is removed from the opening, a liquid binder is applied to at least one of the inner peripheral wall of the opening and the outer peripheral wall of the plug, the plug is assembled to the opening so that the inner peripheral wall of the opening and the outer peripheral wall of the plug are in contact with each other, and then the precursor is sintered. This method makes it possible to easily close the opening with the plug by sintering without requiring welding.

[0008] In a more preferred embodiment, in the binder application step, alcohol is applied to at least one of the inner peripheral wall of the opening and the outer peripheral wall of the plug, and then the liquid binder is applied. This prevents the applied liquid binder from drying, thereby enhancing the bonding strength between the plug and the precursor. [Effects of the Invention]

[0009] According to the present invention, the opening can be easily closed with a plug by sintering, without the need for welding. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a flow diagram illustrating a method for manufacturing a layered object according to an embodiment. [Figure 2] FIG. 2 is a perspective view showing an example of a precursor of a shaped object. [Figure 3] 1A to 1C are schematic cross-sectional views for explaining a method for manufacturing a layered object. [Figure 4] 1A to 1C are schematic cross-sectional views for explaining a method for manufacturing a layered object. [Figure 5] 1A to 1C are schematic cross-sectional views for explaining a method for manufacturing a layered object. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of a method for manufacturing a layered object according to the present invention will be described with reference to the drawings. In the following description, the up / down, left / right, and front / rear directions are merely directions corresponding to the states shown in the drawings and do not limit the manufacturing method. Furthermore, to avoid complicating the description, the term "layered object" may be abbreviated to simply "molded object."

[0012] 1 is a flow diagram showing a method for manufacturing an additively-molded object according to an embodiment. The method for manufacturing an additively-molded object according to this embodiment is a method for manufacturing an additively-molded object having a three-dimensional internal space using a binder jetting method. This method for manufacturing an additively-molded object includes a precursor formation step S1, a plug formation step S2, a powder removal step S3, a binder application step S4, an assembly step S5, and a sintering step S6.

[0013] The precursor-forming step S1 and the plug-forming step S2 are independent steps and may be performed in parallel, or either step may be performed first. In this embodiment, however, an example in which the steps are performed in parallel will be described. Furthermore, the plug-forming step S2 only needs to be completed before the binder-applying step S4 starts. For example, the plug-forming step S2 may be performed after the powder-removing step S3 or in parallel with the powder-removing step S3.

[0014] In the precursor formation step S1, a liquid binder is sprayed onto a powder layer to form a solidified layer, and the solidified layers are stacked to form a precursor of a shaped object with an opening that communicates with the hollow interior space. Specifically, powders of, for example, resin, plaster, sand, or metal are evenly spread to form a powder layer of the desired thickness, and a liquid binder (i.e., binder) is selectively sprayed onto the formed powder layer. As a result, the powder particles in the areas of the powder layer where the liquid binder was sprayed bond together and solidify, forming the first solidified layer. Meanwhile, the powder in the areas of the powder layer where the liquid binder was not sprayed remains unsolidified.

[0015] The liquid binder is not particularly limited as long as it has the adhesive or cohesive properties to bind powder particles together. Examples of solvents for the liquid binder include water, alcohols, ketones, and carboxylic acid esters, and may also be a mixture containing at least one of these. Examples of solutes for the liquid binder include fatty acids, paraffin wax, microcrystalline wax, polyethylene, polypropylene, polystyrene, acrylic resins, polyamide resins, polyesters, stearic acid, polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), and polyethylene glycol (PEG). These liquid binders may be selected according to the type and properties of the powders used.

[0016] Next, the second, third, ..., nth solidified layers are sequentially formed and stacked in the same manner to form a precursor (also called a green body) of the shaped object.

[0017] The precursor of the shaped object is a three-dimensional object, for example, as shown in Fig. 2. As shown in Fig. 2, the precursor 10 is, for example, a rectangular parallelepiped, and a hollow internal space 11 is formed therein. The internal space 11 has, for example, a thin cylindrical shape, and extends in a meandering manner in the front-to-back, left-to-right, and up-to-down directions of the precursor 10, giving it a complex shape. Furthermore, the internal space 11 has many locations where the direction changes relatively sharply (for example, at a bending angle of 90° or more).

[0018] Furthermore, a plurality of openings 12 communicating with the internal space 11 are formed in the outer wall of the precursor 10. The positions and number of the openings 12 are not particularly limited, and are preferably set so that unsolidified powder remaining in the internal space 11 can be smoothly removed to the outside. For example, if it is difficult to remove the unsolidified powder remaining in the internal space 11, openings 12 communicating with the internal space 11 may be formed in the front and rear, left and right, and top and bottom outer walls of the precursor 10.

[0019] 3, the opening 12 has, for example, a truncated cone-like cross section, and the diameter increases from the inside to the outside of the precursor 10. That is, the opening 12 is formed so that its smallest end surface faces the internal space 11. In addition, the diameter of the smallest end surface of the opening 12 is larger than the diameter of the internal space 11.

[0020] In the plug formation step S2, a plug 20 that can be assembled into the opening 12 of the precursor 10 is formed. The plug 20 has a truncated cone-shaped flange portion 21 and a cylindrical insertion portion 22 that is integrally formed with the flange portion 21, as shown in FIG. 3 . The flange portion 21 is formed slightly smaller than the opening 12 so as to fit the shape of the opening 12. The insertion portion 22 is disposed coaxially with the flange portion 21 and protrudes from the smallest end face of the flange portion 21. The insertion portion 22 has a diameter that allows it to be inserted into the internal space 11.

[0021] 3, the diameter of the insertion portion 22 is smaller than the diameter of the smallest end face of the flange portion 21. As a result, a step portion 23 is formed between the flange portion 21 and the insertion portion 22. The plug 20 is made of the same material as the precursor 10, and may be formed by the binder jetting method like the precursor 10, or may be formed by a different method.

[0022] Furthermore, although the plug 20 according to this embodiment has the insertion portion 22 and the flange portion 21, it may have only the flange portion 21. Furthermore, the plug 20 is not limited to the above-described shape, and may have a truncated pyramidal or cylindrical shape, for example.

[0023] The powder removal step S3 following the precursor formation step S1 and the plug formation step S2 is a so-called powder removal step. In this powder removal step S3, unsolidified powder remaining in the internal space 11 of the precursor 10 is removed from the precursor 10 through the opening 12. Specifically, the unsolidified powder in the internal space 11 is removed via the opening 12 by tube pressure feeding and / or tube suction.

[0024] In the binder application step S4 following the powder removal step S3, a liquid binder is applied to at least one of the inner peripheral wall of the opening 12 of the precursor 10 and the outer peripheral wall of the plug 20. For example, as shown in FIG. 3 , the same liquid binder 30 as used in the precursor formation step S1 is applied to the outer peripheral wall of the flange portion 21 of the plug 20 and the outer peripheral wall of the insertion portion 22. At this time, it is preferable to also apply the liquid binder 30 to the inner peripheral wall of the opening 12. In this way, the bonding strength between the plug 20 and the precursor 10 can be increased.

[0025] Note that the liquid bonding agent may be applied to the inner peripheral wall of the opening 12 instead of the outer peripheral wall of the plug 20. In this case, it is preferable to also apply the liquid bonding agent to the inner peripheral wall of the internal space 11 that comes into contact with the outer peripheral wall of the insertion portion 22 of the plug 20 when assembled with the plug 20. In this way, the bonding strength between the plug 20 and the precursor 10 can be increased.

[0026] In the assembling step S5 following the binder application step S4, the plug 20 is assembled into the opening 12 of the precursor 10 so that the inner circumferential wall of the opening 12 and the outer circumferential wall of the plug 20 are in contact with each other. Specifically, as shown in FIG. 4 , the plug 20, to which the liquid binder 30 has been applied, is inserted into the opening 12 of the precursor 10 so that the stepped portion 23 of the plug 20 abuts against the smallest end face of the opening 12. When the stepped portion 23 of the plug 20 abuts against the smallest end face of the opening 12, the outer circumferential wall of the insertion portion 22 of the plug 20 comes into contact with part of the inner circumferential wall of the internal space 11, and the outer circumferential wall of the flange portion 21 of the plug 20 comes into contact with the inner circumferential wall of the opening 12. In this way, the plug 20 is assembled into the opening 12 of the precursor 10.

[0027] In the sintering step S6 following the assembling step S5, the precursor 10 with the plug 20 assembled in the opening 12 is sintered. Specifically, the precursor 10 with the plug 20 assembled in the opening 12 is placed in a sintering furnace or the like and sintered at a predetermined temperature (e.g., 900°C) for a predetermined time (e.g., 3 hours). Examples of the heating atmosphere during sintering include air, an inert gas, and a reduced pressure atmosphere.

[0028] Sintering solidifies the powder that constitutes the precursor 10, increasing the strength of the precursor 10. Furthermore, this sintering shrink-fits the plug 20 into the precursor 10, making it integrated with the precursor 10. Therefore, the opening 12 of the precursor 10 is closed by the plug 20 (see FIG. 5).

[0029] In this way, a shaped object having an internal space 11 is manufactured.

[0030] In the method for manufacturing an additive manufacturing object according to this embodiment, unsolidified powder remaining in the internal space 11 of the precursor 10 is removed from the opening 12 of the precursor 10, a liquid binder 30 is applied to the outer peripheral wall of the plug 20, the plug 20 is assembled to the opening 12 so that the inner peripheral wall of the opening 12 contacts the outer peripheral wall of the plug 20, and then the precursor 10 is sintered. In this manner, the opening 12 of the precursor 10 can be easily closed by the plug 20 through sintering, without the need for welding. Furthermore, by eliminating the conventional welding process, it is expected that the manufacturing costs and manufacturing man-hours can be reduced.

[0031] In the sintering step S6 of the present embodiment, the precursor 10 in which the plug 20 is assembled in the opening 12 may be subjected to a degreasing treatment before sintering. In this way, it is possible to prevent the occurrence of sintering defects due to the remaining liquid binder 30.

[0032] Furthermore, in the binder application step S4, alcohol may be applied to at least one of the inner peripheral wall of the opening 12 and the outer peripheral wall of the plug 20, and then the liquid binder may be applied. This prevents the applied liquid binder from drying, which has the effect of increasing the bonding strength between the plug 20 and the precursor 10.

[0033] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various design modifications can be made without departing from the spirit of the present invention as set forth in the claims. [Explanation of symbols]

[0034] 10: precursor, 11: internal space, 12: opening, 20: plug, 21: flange portion, 22: insertion portion, 23: step portion, 30: liquid bonding agent

Claims

[Claim 1] a precursor formation step of forming a precursor of an additive manufacturing object having an opening communicating with the hollow internal space by spraying a liquid binder onto a powder layer to form a solidified layer and stacking the formed solidified layer; a plug forming step of forming a plug that can be assembled into the opening; a powder removing step of removing unsolidified powder remaining in the internal space of the precursor from the opening to the outside of the precursor; a binder application step of applying the liquid binder to at least one of an inner peripheral wall of the opening and an outer peripheral wall of the plug after removing unsolidified powder; an assembly step of assembling the plug into the opening so that an inner peripheral wall of the opening and an outer peripheral wall of the plug are in contact with each other; a sintering step of sintering the precursor having the plug assembled in the opening; Including, a step of applying the liquid binder after applying alcohol to at least one of the inner peripheral wall of the opening and the outer peripheral wall of the plug in the binder application step.

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