Method for producing laminated molded article

Abstract

To provide a method for producing a laminated molded article that allows efficient production of a laminated molded article with high shape accuracy through improvement of fillability of a powder layer and enhancement of penetration of an aqueous binder solution into the powder layer.SOLUTION: A method for producing a laminated molded article, comprises: a powder layer forming step in which shaping particles, each having a metal particle and a coating disposed on the surface of the metal particle and containing a compound originating from a coupling agent with a hydrophobic functional group, are laid in layers to form a powder layer; an energy applying step in which energy is imparted to the powder layer such that a water contact angle of the shaping particles is in a range of 3° or more and 45° or less; and a binder solution supplying step in which an aqueous binder solution is supplied to the powder layer subjected to the energy applying step.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, additive manufacturing methods using metal powder have become increasingly popular as a technology for creating three-dimensional objects. One such additive manufacturing method is the binder jet method.

[0003] Patent Document 1 discloses a solid freeform fabrication system that uses inkjet printing technology to eject droplets of different volumes as binder droplets onto a powder layer, solidifying the powder and creating an object. Because the method for manufacturing an object using such a system includes a step of ejecting binder droplets, it can be considered a type of binder jetting. By ejecting droplets of different volumes, such a system can produce an object with a smooth surface finish.

[0004] Furthermore, Patent Document 2 discloses the use of powder for additive manufacturing in binder jetting, in which a cyclic structure-containing group, a fluoroalkyl group, or a fluoroaryl group is introduced to the particle surface of a metal powder. The introduction of such functional groups allows for the production of powder for additive manufacturing with high fluidity, resulting in a powder layer with a high packing ratio. By increasing the packing ratio of the powder layer, an additive manufacturing object with high shape precision can ultimately be obtained.

[0005] Furthermore, Patent Document 3 discloses a method for forming a three-dimensional object, which includes depositing a high-density feedstock containing a metal powder and a binder onto a surface, depositing a sintering-selective material according to a pattern, irradiating the feedstock with a laser to prime it, and removing the binder. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Special Publication No. 2006-515813 [Patent Document 2] Japanese Patent Publication No. 2022-122503 [Patent Document 3] Japanese Patent Publication No. 2022-068839 Summary of the Invention [Problem to be solved by the invention]

[0007] In the binder jet method, a water-based liquid (water-based binder solution) is often used as the binder droplets. The water-based binder solution penetrates into the powder layer, solidifying that area.

[0008] However, the powder for additive manufacturing described in Patent Document 2 has highly hydrophobic particle surfaces, so the aqueous binder solution may not quickly penetrate into the powder layer. In such cases, the penetration takes time, which can reduce the supply rate of the aqueous binder solution or cause uneven penetration. This reduces the speed at which the object (modeled body) is manufactured and reduces the shape accuracy of the manufactured object.

[0009] Furthermore, the method described in Patent Document 3 includes a step of depositing a feedstock containing a metal powder and a binder. With such a feedstock, there is a concern that the binder may absorb moisture and reduce fluidity, resulting in a decrease in the packing ability of the metal powder in the powder layer.

[0010] Therefore, the challenge is to realize a method that can efficiently manufacture layered objects with high shape accuracy by improving the packing ability of the powder layer and increasing the permeability of the aqueous binder solution into the powder layer. [Means for solving the problem]

[0011] A method for manufacturing a layered object according to an application example of the present invention includes: a powder layer forming step of laying metal particles and coatings formed on the surfaces of the metal particles, the coatings containing a compound derived from a coupling agent having a hydrophobic functional group, in a layered manner to form a powder layer; an energy applying step of applying energy to the powder layer so that the water contact angle of the particles for shaping becomes 3° or more and 45° or less; a binder solution supplying step of supplying an aqueous binder solution to the powder layer that has been subjected to the energy applying step; It has. [Brief explanation of the drawings]

[0012] [Figure 1] 1A to 1C are process diagrams illustrating a configuration of a method for manufacturing a layered object according to an embodiment. [Figure 2] 2A to 2C are diagrams for explaining a method for manufacturing the layered object shown in FIG. 1. [Figure 3] 2A to 2C are diagrams for explaining a method for manufacturing the layered object shown in FIG. 1. [Figure 4] 2A to 2C are diagrams for explaining a method for manufacturing the layered object shown in FIG. 1. [Figure 5] 2A to 2C are diagrams for explaining a method for manufacturing the layered object shown in FIG. 1. [Figure 6] 2A to 2C are diagrams for explaining a method for manufacturing the layered object shown in FIG. 1. [Figure 7] 2A to 2C are diagrams for explaining a method for manufacturing the layered object shown in FIG. 1. [Figure 8] 2A to 2C are diagrams for explaining a method for manufacturing the layered object shown in FIG. 1. [Figure 9] 2A to 2C are diagrams for explaining a method for manufacturing the layered object shown in FIG. 1. [Figure 10] 2A to 2C are diagrams for explaining a method for manufacturing the layered object shown in FIG. 1. [Figure 11] 1A to 1C are process diagrams illustrating a method for manufacturing a metal sintered body. DETAILED DESCRIPTION OF THE INVENTION

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the method for producing a layered object of the present invention will now be described in detail with reference to the accompanying drawings.

[0014] 1. Manufacturing method for additive manufacturing objects First, a method for manufacturing a layered object according to an embodiment will be described.

[0015] FIG. 1 is a process diagram showing the configuration of a method for manufacturing an additive manufacturing object according to an embodiment. FIGS. 2 to 10 are diagrams for explaining the method for manufacturing the additive manufacturing object shown in FIG. 1. In FIGS. 2 to 10, three mutually orthogonal axes are defined: an X-axis, a Y-axis, and a Z-axis. Each axis is represented by an arrow, with the tip end side being the "plus side" and the base end side being the "minus side." In the following description, the plus side of the Z-axis will be referred to as "up" and the minus side of the Z-axis will be referred to as "down." Furthermore, both directions parallel to the X-axis will be referred to as X-axis directions, both directions parallel to the Y-axis will be referred to as Y-axis directions, and both directions parallel to the Z-axis will be referred to as Z-axis directions.

[0016] 1 to 10 is a method called the binder jet method, which includes a powder layer forming step S102, an energy applying step S104, a binder solution supplying step S106, a repeating step S108, and a removal step S110, as shown in Fig. 1. The binder jet method has the advantage of being able to produce objects with complex shapes because it does not require a support structure to support the object.

[0017] In the powder layer forming step S102, shaping particles 1 are laid down to form a powder layer 31. In the energy applying step S104, energy is applied to the powder layer 31 so that the water contact angle of the shaping particles 1 is between 3° and 45°. In the binder solution supplying step S106, an aqueous binder solution 4 is supplied from the inkjet head 26 to the powder layer 31 that has been subjected to the energy applying step S104, bonding the particles in the powder layer 31 together to form a bonded layer 41. In the repeating step S108, the powder layer forming step S102, the energy applying step S104, and the binder solution supplying step S106 are repeated one or more times to stack the bonded layers 41. This results in a layered object 6. In the removing step S110, the layered object 6 is removed from the powder layer 31. Each step will be described below in order.

[0018] 1.1. Additive manufacturing equipment First, prior to describing the powder layer forming step S102, the layered manufacturing apparatus 2 will be described.

[0019] As shown in Figures 2 to 10, the additive manufacturing device 2 includes an apparatus main body 21 having a powder storage section 211 and a manufacturing section 212, a powder supply elevator 22 provided in the powder storage section 211, a manufacturing stage 23 provided in the manufacturing section 212, and a coater 24 and an inkjet head 26 movably provided on the apparatus main body 21.

[0020] The powder storage section 211 is a recessed portion that is provided in the device main body 21 and is open at the top. The powder storage section 211 stores the shaping particles 1. An appropriate amount of the shaping particles 1 stored in the powder storage section 211 is supplied to the shaping section 212 by the coater 24.

[0021] A powder feed elevator 22 is disposed at the bottom of the powder storage section 211. The powder feed elevator 22 is movable up and down with the shaping particles 1 loaded on it. By moving the powder feed elevator 22 upward, the shaping particles 1 loaded on the powder feed elevator 22 are pushed up and caused to protrude from the powder storage section 211. As a result, the protruding shaping particles 1 can be moved by the coater 24 toward the shaping section 212.

[0022] The modeling unit 212 is provided in the device main body 21 and is a recessed portion that is open at the top. A modeling stage 23 is disposed inside the modeling unit 212. The modeling particles 1 are laid in layers on the modeling stage 23 by a coater 24. The modeling stage 23 is also movable in the vertical direction with the modeling particles 1 laid on it. The amount of the modeling particles 1 laid on the modeling stage 23 can be adjusted by appropriately setting the height of the modeling stage 23.

[0023] The coater 24 extends in the Y-axis direction and is movable in the X-axis direction from the powder storage section 211 to the forming section 212. The coater 24 drags the particles 1 for forming, thereby leveling the particles 1 and laying them in a layer.

[0024] The inkjet head 26 is movable in the X-axis direction and the Y-axis direction in the modeling unit 212. The inkjet head 26 supplies a desired amount of the aqueous binder solution 4 to a desired position. The inkjet head 26 may be equipped with a plurality of discharge nozzles. The aqueous binder solution 4 may be discharged from the plurality of discharge nozzles simultaneously or with a time lag.

[0025] 1.2. Powder layer formation process In the powder layer forming step S102, the particles 1 for shaping are spread on the shaping stage 23 to form a powder layer 31. Specifically, as shown in FIGS. 2 and 3, a coater 24 is used to drag the particles 1 for shaping stored in the powder storage section 211 onto the shaping stage 23 and smooth it to a uniform thickness. This results in the powder layer 31 shown in FIG. 4. At this time, the upper surface of the shaping stage 23 is lowered below the upper end of the shaping section 212, and the thickness of the powder layer 31 can be adjusted by adjusting the amount of lowering.

[0026] As will be described later, the surfaces of the shaping particles 1 are hydrophobic, which suppresses moisture absorption even when placed in a high-temperature, high-humidity environment, thereby providing shaping particles 1 that maintain high fluidity and high packing ability.

[0027] The thickness of the powder layer 31 in this step is not particularly limited, but is preferably from 2 to 20 times, more preferably from 3 to 10 times, and particularly preferably from 4 to 8 times the average particle size of the metal powder used in the shaping particles 1. If the thickness of the powder layer 31 is within the above range, the shape precision of the final layered shaped body 6 can be sufficiently improved.

[0028] If the thickness of the powder layer 31 is below the lower limit, a larger number of powder layers 31 are required to manufacture the desired layered object 6. This may increase the time required to manufacture the layered object 6. On the other hand, if the thickness of the powder layer 31 exceeds the upper limit, the bonding layer 41 formed from the powder layer 31 also becomes thick, which may decrease the shape accuracy of the layered object 6.

[0029] Thereafter, the powder layer 31 may be compressed in the thickness direction as necessary. This increases the packing density of the shaping particles 1 in the powder layer 31. As a result, the penetration depth of the aqueous binder solution 4 in the binder solution supplying step S106, which will be described later, can be adjusted.

[0030] The relative density of the powder layer 31 after compression is preferably 40% or more, more preferably 45% to 70%, and even more preferably 50% to 65%. If the relative density is below the lower limit, the gaps between the particles in the powder layer 31 become large, which may prevent the aqueous binder solution 4 from penetrating sufficiently. On the other hand, if the relative density is above the upper limit, the gaps between the particles in the powder layer 31 may become too small. In this case, the continuity of the gaps may be lost, which may reduce the permeability of the aqueous binder solution 4.

[0031] The relative density of the powder layer 31 is the ratio of the density of the powder layer 31 to the true density of the material constituting the shaping particles 1. The density of the powder layer 31 can be calculated based on the volume calculated from the area and thickness of the powder layer 31 and the mass of the powder layer 31.

[0032] 1.3. Energy application process In the energy application step S104, as shown in Fig. 4, energy E is applied to the powder layer 31. Although the surfaces of the particles 1 for molding have been previously made hydrophobic, the application of energy E can alleviate this hydrophobicity. As a result, the fluidity and packing ability of the particles 1 for molding are ensured before the application of energy E, and after the application of energy E, the particles 1 for molding are given appropriate hydrophilicity. Therefore, when the aqueous binder solution 4 is supplied to the powder layer 31 in the binder solution supply step S106 described below, the permeability of the aqueous binder solution 4 in the powder layer 31 can be improved.

[0033] The energy E is applied so that the contact angle of the shaping particles 1 with water is 3° or more and 45° or less. The contact angle of the shaping particles 1 with water is preferably 5° or more and 40° or less, and more preferably 10° or more and 35° or less. The contact angle of the shaping particles 1 with water is measured as follows.

[0034] First, a stainless steel plate is prepared, and the shaping particles 1 are placed on it and smoothed with a squeegee to form a particle layer with a thickness of 50 μm. Next, energy E is applied to the obtained particle layer. This produces a test specimen for contact angle measurement.

[0035] Next, the water contact angle of the test specimen is measured using the θ / 2 method using a contact angle measuring device, DropMaster 500, manufactured by Kyowa Interface Science Co., Ltd. The measurement conditions are an air temperature of 25°C and a relative humidity of 50%±5%. The amount of water dropped is 3 μL, and the measurement is taken 5 seconds after the drop has landed.

[0036] Then, the water contact angle is measured while changing the integrated amount of energy E. This allows the integrated amount of energy E required to bring the water contact angle into the above range to be estimated in advance. In the energy application step S104, the integrated amount of energy E estimated in this way is applied to the powder layer 31.

[0037] The water contact angle of the shaping particles 1 tends to decrease according to the cumulative amount of the applied energy E. Therefore, when estimating the cumulative amount of the energy E, for example, an operation of increasing the cumulative amount of the energy E may be performed until the water contact angle decreases to a target value.

[0038] If the water contact angle of the shaping particles 1 is below the lower limit, the hydrophobicity of the surface of the shaping particles 1 is reduced too much. This reduces the moisture resistance of the shaping particles 1, and for example, when the shaping particles 1 are reused without being used in the layered object 6, the fluidity and filling ability of the shaping particles 1 may be reduced. On the other hand, if the water contact angle of the shaping particles 1 is above the upper limit, the hydrophobicity of the surface of the shaping particles 1 is not sufficiently reduced. This prevents the penetration of the aqueous binder solution 4 from being sufficiently increased.

[0039] Methods for applying energy E to the powder layer 31 include, for example, irradiation with energy rays, irradiation with plasma, irradiation with electron beams, ozone treatment, and corona treatment. All of these methods are capable of applying energy E locally. Therefore, it is possible to selectively apply energy E to the region to which the aqueous binder solution 4 is supplied in the binder solution supplying step S106 described below. This makes it possible to prevent the application of energy E to the shaping particles 1 that are not used in manufacturing the layered object 6. As a result, when unused shaping particles 1 are reused, it is possible to prevent a decrease in the fluidity and filling ability of the shaping particles 1.

[0040] Examples of the energy ray include infrared rays, visible light, ultraviolet rays, etc. The energy ray may also be a laser beam in these wavelength ranges.

[0041] Examples of infrared ray irradiators include infrared flash lamps, halogen lamps, light-emitting diodes, etc. The wavelength of the energy rays irradiated in this case is not particularly limited, but is preferably more than 780 nm and 1 mm or less.

[0042] Examples of visible light or ultraviolet light irradiation devices include xenon lamps, excimer lamps, cold cathode ultraviolet lamps, femtosecond lasers, light-emitting diodes, etc. The wavelength of the energy beam irradiated in this case is not particularly limited, but visible light is 380 nm or more and 780 nm or less, and ultraviolet light is 10 nm or more and less than 380 nm.

[0043] Among these, the energy application step S104 preferably includes a process of irradiating ultraviolet light having a wavelength of 253 nm or less for 30 seconds or more. By such a process, an appropriate amount of energy E can be applied efficiently in a simple manner.

[0044] The irradiation time of ultraviolet light having a wavelength of 253 nm or more is preferably 40 seconds or more and 360 seconds or less, and more preferably 50 seconds or more and 200 seconds or less.

[0045] Examples of the type of plasma include air plasma, oxygen plasma, argon-hydrogen plasma, and nitrogen plasma. Of these, oxygen plasma is preferably used. Oxygen plasma can efficiently reduce the hydrophobicity of the surfaces of the particles 1 for molding.

[0046] Examples of plasma irradiation devices include vacuum microwave plasma devices, vacuum high-frequency plasma devices, and atmospheric pressure plasma devices. Of these, atmospheric pressure plasma devices are preferred. Atmospheric pressure plasma devices are easily incorporated into the manufacturing method of the layered object 6. Therefore, using an atmospheric pressure plasma device can easily improve the manufacturing efficiency of the layered object 6. The flow rate of the plasma gas in the atmospheric pressure plasma device is preferably 100 sccm to 2000 sccm, and more preferably 300 sccm to 1000 sccm. Furthermore, the plasma generation output is not particularly limited, but is preferably 200 W to 2000 W, and more preferably 300 W to 1000 W. Furthermore, the generated plasma may be sprayed from the nozzle while scanning the nozzle. In this case, the scanning speed is preferably 5 mm / s to 100 mm / s, and more preferably 10 mm / s to 50 mm / s.

[0047] The ozone treatment is, for example, a treatment in which the particles 1 are brought into contact with a gas containing ozone (ozone-containing gas). The ozone concentration in the ozone-containing gas is not particularly limited, but is preferably 0.5% by volume or more and 20% by volume or less, and more preferably 1% by volume or more and 5% by volume or less. This allows the hydrophobicity of the surfaces of the particles 1 to be moderately reduced.

[0048] The flow rate of the ozone-containing gas brought into contact with the particles 1 is not particularly limited, but is preferably 100 ccm or more and 2000 ccm or less, and more preferably 300 ccm or more and 1000 ccm or less.

[0049] The energy E may be applied to the entire powder layer 31, or may be applied selectively to the formation region 60 of the powder layer 31 that corresponds to the layered object 6 to be formed. In the latter case, the energy E is not applied to regions other than the formation region 60, so the hydrophobicity of the surfaces of the particles 1 can be maintained. Therefore, when particles 1 that were not used for forming are reused, the fluidity and filling properties of the particles 1 can be ensured to be good.

[0050] 1.4. Binder solution supply process In the binder solution supplying step S106, as shown in FIG. 5, droplets of the aqueous binder solution 4 are ejected from the inkjet head 26 onto a formation region 60 of the powder layer 31 that corresponds to the layered object 6 to be formed. In the formation region 60 to which the aqueous binder solution 4 is supplied, the particles of the particles 1 for forming are bonded together, resulting in a bonded layer 41 as shown in FIG. 6. By ejecting the aqueous binder solution 4 from the inkjet head 26, the aqueous binder solution 4 can be supplied to the desired position with high precision. This ultimately allows the production of a layered object 6 with high shape precision.

[0051] The aqueous binder solution 4 is a liquid containing water and a binder component capable of binding the particles 1 together.

[0052] The surface tension of the aqueous binder solution 4 is preferably set to 20 mN / m or more and 40 mN / m or less, more preferably set to 20 mN / m or more and 35 mN / m or less, and even more preferably set to 20 mN / m or more and 30 mN / m or less. The driving force for permeation due to capillary action tends to increase as the surface tension of the aqueous binder solution 4 increases. Therefore, as long as the surface tension of the aqueous binder solution 4 is within the above range, the permeability of the aqueous binder solution 4 can be increased, even if the particle surfaces of the shaping particles 1 are made hydrophobic, and the shape precision of the binder layer 41 can be improved.

[0053] If the surface tension of the aqueous binder solution 4 is below the lower limit, the driving force for permeation due to capillary action may not work sufficiently for the aqueous binder solution 4 supplied to the powder layer 31. As a result, the aqueous binder solution 4 may not permeate sufficiently into the powder layer 31, which may result in a decrease in the shape precision of the binder layer 41. On the other hand, if the surface tension of the aqueous binder solution 4 is above the upper limit, the surface tension becomes excessive, which may cause droplets of the aqueous binder solution 4 to become spherical. In this case, the aqueous binder solution 4 may have difficulty permeating into the powder layer 31.

[0054] The surface tension of the aqueous binder solution 4 is measured using a surface tensiometer. Examples of the surface tensiometer include the CBVP-Z surface tensiometer manufactured by Kyowa Interface Science Co., Ltd.

[0055] Examples of binder components contained in the aqueous binder solution 4 include fatty acids, paraffin wax, microcrystalline wax, polyethylene, polypropylene, polystyrene, acrylic resins, polyamide resins, polyesters, stearic acid, polyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), polyethylene glycol (PEG), urethane resins, epoxy resins, vinyl resins, unsaturated polyester resins, and phenolic resins. Adding these components to a solvent or dispersion medium containing water tends to reduce the surface tension of the aqueous binder solution 4. For this reason, the surface tension of the aqueous binder solution 4 can be adjusted depending on the type and amount of binder component added.

[0056] Among these, polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP) is preferably used as the binder component. The aqueous binder solution 4 containing these binder components has a suitable affinity and viscosity for the shaping particles 1, and also has good binding properties. Therefore, the aqueous binder solution 4 containing these binder components contributes to the production of an additive manufacturing object 6 with particularly good shape precision.

[0057] The concentration of the binder component in the aqueous binder solution 4 is preferably 0.1% by mass or more and 20.0% by mass or less, more preferably 1.0% by mass or more and 15.0% by mass or less, and even more preferably 5.0% by mass or more and 12.0% by mass or less. This optimizes the viscosity of the aqueous binder solution 4 and ensures sufficient binding strength between the shaping particles 1. Furthermore, by setting the concentration of the binder component within the above range, the surface tension of the aqueous binder solution 4 can be optimized.

[0058] Furthermore, when the aqueous binder solution 4 contains a liquid other than water, examples of the liquid include alcohols, ketones, and carboxylic acid esters, and a mixture containing at least one of these is used. Adding these components to water tends to reduce the surface tension of the aqueous binder solution 4. This allows the surface tension of the aqueous binder solution 4 to be adjusted.

[0059] The water content in the aqueous binder solution 4 is not particularly limited, but is preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more. This allows the water ratio in the aqueous binder solution 4 to be sufficiently increased, thereby reducing the environmental impact when the aqueous binder solution 4 is dried or disposed of.

[0060] In addition to the above components, the aqueous binder solution 4 may contain additives such as viscosity adjusters, surfactants, moisturizing agents, stabilizers, antifoaming agents, crosslinking agents, and antioxidants.

[0061] The total content of the additives in the aqueous binder solution 4 is preferably 20.0% by mass or less, and more preferably 1.0% by mass or more and 15.0% by mass or less.

[0062] The movement speed of the inkjet head 26 is not particularly limited, but is preferably 0.1 mm / s to 20 mm / s, more preferably 1 mm / s to 15 mm / s, and even more preferably 3 mm / s to 10 mm / s. Setting the movement speed of the inkjet head 26 within this range can improve the ejection position accuracy of the droplets of the aqueous binder solution 4. This can improve the shape accuracy of the binder layer 41, and therefore the shape accuracy of the final layered object 6.

[0063] If the moving speed of the inkjet head 26 is below the lower limit, there is a risk of a decrease in the production efficiency of the layered object 6. On the other hand, if the moving speed of the inkjet head 26 exceeds the upper limit, there is a risk of a decrease in the accuracy of the droplet ejection position, which may result in a decrease in the shape accuracy of the binder layer 41.

[0064] The moving speed of the inkjet head 26 is the average speed of the inkjet head 26 measured at the timing when droplets of the aqueous binder solution 4 are ejected toward the formation region 60. The average speed is calculated by measuring the speed of the inkjet head 26 10 or more times at the timing when droplets are ejected and averaging the measured values.

[0065] The interval between droplets of the aqueous binder solution 4 is not particularly limited, but is preferably 1 μm to 90 μm, more preferably 5 μm to 80 μm, even more preferably 10 μm to 70 μm, and particularly preferably 20 μm to 60 μm. By setting the interval between droplets of the aqueous binder solution 4 within the above range, the aqueous binder solution 4 can be supplied uniformly and in a sufficient amount.

[0066] Although the droplet ejection interval of the aqueous binder solution 4 may be below the lower limit, in that case, the shape precision of the layered object 6 cannot be expected to be significantly improved, and it may become difficult to increase the movement speed of the inkjet head 26, which may reduce the production efficiency of the layered object 6. On the other hand, if the droplet ejection interval of the aqueous binder solution 4 exceeds the upper limit, the droplets of the aqueous binder solution 4 that land on the powder layer 31 may be too far apart, preventing the formation of a continuous coating film. In this case, there is a higher probability that particles will not bond together, and the shape precision of the layered object 6 will be reduced.

[0067] The droplet spacing of the aqueous binder solution 4 is determined by measuring the spacing between the droplets within a 5 mm x 5 mm area under the same conditions as when the aqueous binder solution 4 is dispensed onto a smooth surface that does not absorb the aqueous binder solution 4, and then calculating the average of these measurements. The spacing between droplets is the center-to-center distance between adjacent droplets. The average value is calculated by measuring the spacing between at least 10 pairs of randomly selected droplets.

[0068] Furthermore, the volume of the droplets of the aqueous binder solution 4 ejected from the inkjet head 26 is not particularly limited, but is preferably from 1 pL to 10 pL, more preferably from 1 pL to 8 pL, and even more preferably from 2 pL to 6 pL. Setting the volume of the droplets of the aqueous binder solution 4 within this range can improve the ejection position accuracy of the droplets, particularly at the outer edge of the binder layer 41. This can improve the shape accuracy of the layered object 6, particularly at the portion corresponding to the outer edge of the binder layer 41.

[0069] If the volume of the droplets of the aqueous binder solution 4 is below the lower limit, it becomes difficult to increase the movement speed of the inkjet head 26, which may reduce the production efficiency of the layered object 6. On the other hand, if the volume of the droplets of the aqueous binder solution 4 exceeds the upper limit, the mass of the droplets may increase. In this case, the impact when the droplets land on the powder layer 31 increases, reducing the shape accuracy of the binder layer 41, which in turn reduces the shape accuracy of the layered object 6.

[0070] The volume of the droplets of the aqueous binder solution 4 is determined by observing the plan view and cross section of the droplets after discharging the aqueous binder solution 4 onto a smooth surface that does not absorb the aqueous binder solution 4 under the same conditions as when discharging it onto the formation region 60. The average volume is determined by averaging the volumes of 10 or more droplets randomly selected.

[0071] Simultaneously with or after the supply of the aqueous binder solution 4, the powder layer 31 to which the aqueous binder solution 4 has been supplied may be subjected to a drying process. Examples of drying processes include heating and gas spraying. The drying process can promote the drying of the powder layer 31 to which the aqueous binder solution 4 has been supplied. This allows the penetration range of the aqueous binder solution 4 to be controlled as desired, further improving the shape precision of the layered object 6 that is finally obtained.

[0072] The heating temperature when heating is not particularly limited, but is preferably 50°C or higher and 250°C or lower, and more preferably 70°C or higher and 200°C or lower.

[0073] Furthermore, if the binder has photo-curing or ultraviolet-curing properties, a light irradiation process or ultraviolet-irradiation process may be performed, which allows the binder to be solidified or hardened in a shorter time.

[0074] 1.5.Repetitive process In the repeating step S108, the powder layer forming step S102, the energy applying step S104, and the binder solution supplying step S106 are repeated one or more times. In other words, these steps are performed a total of two or more times. This results in multiple bonding layers 41 being stacked. By stacking the bonding layers 41 in this manner, a layered object 6 having a desired three-dimensional shape is obtained, as shown in FIG. 10.

[0075] Specifically, first, a new powder layer 31 shown in Fig. 7 is formed on the binder layer 41 shown in Fig. 6. Next, as shown in Fig. 8, an aqueous binder solution 4 is supplied to a formation region 60 of the newly formed powder layer 31. This results in a second binder layer 41 shown in Fig. 9. The two binder layers 41 may have the same shape or different shapes.

[0076] 1.6.Removal process In the removal step S110, the binder layer 41 is removed from the powder layer 31. In this way, the layered object 6 is obtained.

[0077] Of the powder layer 31, the shaping particles 1 that did not form the binder layer 41 are collected and reused as needed, that is, are used again to manufacture the layered shaped object 6.

[0078] 2. Particles for modeling Next, the shaping particles 1 will be described.

[0079] 2.1. Metal powder The metal material contained in the metal powder is not particularly limited, but when a metal sintered body is produced from the additive manufacturing body 6, it is a sinterable material. Examples of sinterable metal materials include simple elements such as Fe, Ni, Co, Ti, Al, and Mg, as well as alloys and intermetallic compounds containing these as main components. Of these, Fe-based metal materials are preferably used as the metal material. Fe-based metal materials refer to metal materials with an Fe content of more than 50% in terms of atomic ratio. Fe-based metal materials are easy to obtain and can be used to produce metal sintered bodies with excellent mechanical properties.

[0080] Examples of Fe-based metallic materials include stainless steels such as austenitic stainless steel, ferritic stainless steel, martensitic stainless steel, precipitation hardened stainless steel, and austenitic-ferritic (duplex) stainless steel, as well as low-carbon steel, carbon steel, heat-resistant steel, die steel, high-speed tool steel, Fe-Ni alloys, and Fe-Ni-Co alloys.

[0081] Among these, stainless steel is preferably used as the Fe-based metallic material. Stainless steel is a type of steel that has excellent mechanical strength and corrosion resistance. Therefore, by using a metal powder made of stainless steel, it is possible to efficiently produce a metal sintered body that has excellent mechanical strength and corrosion resistance and high shape precision.

[0082] Examples of austenitic stainless steel include SUS301, SUS301L, SUS301J1, SUS302B, SUS303, SUS304, SUS304Cu, SUS304L, SUS304N1, SUS304N2, SUS304LN, SUS304J1, SUS304J2, SUS305, SUS309S, SUS310S, SUS312L, SUS315J1, SUS315J2, SUS316, SUS316L, SUS316N, SUS316LN, SUS316Ti, SUS316J1, SUS316J1L, SUS317, SUS317L, SUS317LN, SUS317J1, SUS317J2, SUS836L, SUS890L, SUS321, SUS347, SUSXM7, and SUSXM15J1.

[0083] Examples of ferritic stainless steel include SUS405, SUS410L, SUS429, SUS430, SUS430LX, SUS430J1L, SUS434, SUS436L, SUS436J1L, SUS445J1, SUS445J2, SUS444, SUS447J1, and SUSXM27.

[0084] Examples of martensitic stainless steel include SUS403, SUS410, SUS410S, SUS420J1, SUS420J2, and SUS440A.

[0085] Precipitation hardening stainless steel includes, for example, SUS630 and SUS631.

[0086] Examples of austenitic-ferritic (duplex) stainless steel include SUS329J1, SUS329J3L, and SUS329J4L.

[0087] The above symbols are material symbols based on the JIS standard. The types of stainless steel in this specification are distinguished by the above material symbols.

[0088] The layered object 6 may be manufactured using shaping particles 1 containing different types of metal materials. For example, if the layered object 6 is composed of two or more binder layers 41, one binder layer 41 may be manufactured using shaping particles 1 containing a first metal material, and another binder layer 41 may be manufactured using shaping particles 1 containing a second metal material.

[0089] 2.2.Coating The shaping particles 1 have a coating covering the surface of a core particle (metal particle) made of the above-mentioned metal material. This coating contains a compound derived from a coupling agent having a hydrophobic functional group. By providing such a coating, the shaping particles 1 can maintain high fluidity and high packing ability during the formation of the powder layer 31, even when placed in a high-temperature, high-humidity environment, until the energy-imparting step S104 is performed. Furthermore, providing a coating can also increase the affinity between the shaping particles 1 and the binder.

[0090] The coupling agent may be a compound having a hydrophobic functional group and a hydrolyzable group, and specific examples thereof include a silane coupling agent, a titanium coupling agent, and a zirconium coupling agent. The following chemical formula is an example of the molecular structure of a silane coupling agent.

[0091] [ka]

[0092] In the above formula, X is a functional group, Y is a spacer, and OR is a hydrolyzable group, where R is, for example, a methyl group or an ethyl group.

[0093] The hydrolyzable group is, for example, an alkoxy group or a halogen group, and among these, the alkoxy group generates a silanol group upon hydrolysis. This silanol reacts with the hydroxyl group generated on the surface of the metal particle, and the coupling agent adheres to the surface of the metal particle.

[0094] The coupling agent may contain at least one such alkoxy group, preferably two or more, and more preferably three alkoxy groups as shown in the formula above. In other words, the coupling agent preferably contains a dialkoxy group, and more preferably a trialkoxy group. A coupling agent containing a trialkoxy group reacts with the three hydroxyl groups generated on the surface of the metal particles. Therefore, a coating derived from the coupling agent exhibits good adhesion to the metal particles. Furthermore, a coupling agent containing a trialkoxy group also has excellent film-forming properties, allowing for the formation of a coating with excellent continuity. Such a coating contributes to further enhancing the fluidity of the shaping particles 1. Meanwhile, the hydrophobicity of a coating derived from such a coupling agent is reduced depending on the integrated amount of energy E applied in the energy application step S104. Therefore, by using such a coupling agent, a coating with an excellent balance of hydrophobicity and hydrophilicity can be formed.

[0095] Examples of hydrophobic functional groups possessed by coupling agents include alkyl groups, vinyl groups, cyclic structure-containing groups, fluoroalkyl groups, and fluoroaryl groups. Cyclic structure-containing groups, fluoroalkyl groups, and fluoroaryl groups are particularly preferred, with cyclic structure-containing groups being even more preferred. These hydrophobic functional groups are resistant to denaturation even in high-temperature, high-humidity environments. Therefore, by using these hydrophobic functional groups, shaping particles 1 having good fluidity and packing properties can be obtained, even when stored in high-temperature, high-humidity environments.

[0096] Among these, coupling agents having a cyclic structure-containing group include, for example, coupling agents having an aryl group and coupling agents having a cyclic ether group. The cyclic structure-containing group is preferably an aryl group, and more preferably a phenyl group. These have excellent heat resistance, which contributes to the realization of shaping particles 1 that are less likely to lose fluidity or packing ability, even when exposed to high-temperature environments.

[0097] Examples of coupling agents having an aryl group include: Phenyltrimethoxysilane represented by the following formula (A-1):

[0098] [ka]

[0099] Phenyltriethoxysilane represented by the following formula (A-2):

[0100] [ka]

[0101] Dimethoxydiphenylsilane represented by the following formula (A-3):

[0102] [ka]

[0103] 2,2-dimethoxy-1-phenyl-1-aza-2-silacyclopentane represented by the following formula (A-4):

[0104] [ka]

[0105] etc.

[0106] Examples of coupling agents having a cyclic ether group include: 3-glycidoxypropylmethyldimethoxysilane represented by the following formula (A-5):

[0107] [ka]

[0108] 3-glycidoxypropyltrimethoxysilane represented by the following formula (A-6):

[0109] [ka]

[0110] 3-glycidoxypropylmethyldiethoxysilane represented by the following formula (A-7):

[0111] [ka]

[0112] 3-glycidoxypropyltriethoxysilane represented by the following formula (A-8):

[0113] [ka]

[0114] etc.

[0115] Examples of coupling agents having a fluoroalkyl group include: Trimethoxy(3,3,3-trifluoropropyl)silane represented by the following formula (B-1):

[0116] [ka]

[0117] Trimethoxy(1H,1H,2H,2H-tridecafluoro-n-octyl)silane represented by the following formula (B-2):

[0118] [ka]

[0119] Trimethoxy(1H,1H,2H,2H-nonafluorohexyl)silane represented by the following formula (B-3):

[0120] [ka]

[0121] etc.

[0122] Examples of coupling agents having a fluoroaryl group include: Trimethoxy(11-pentafluorophenoxyundecyl)silane represented by the following formula (C-1):

[0123] [ka]

[0124] Pentafluorophenyldimethylchlorosilane represented by the following formula (C-2):

[0125] [ka]

[0126] etc.

[0127] The amount of coupling agent added is not particularly limited, but is preferably 0.01% by mass or more and 1.00% by mass or less, and more preferably 0.05% by mass or more and 0.50% by mass or less, relative to the metal particles.

[0128] The procedure for introducing a coupling agent to metal particles is not particularly limited, but examples include a procedure in which the metal particles and a coupling agent are placed in a chamber and then the chamber is heated; a procedure in which the metal particles are placed in a chamber and then the coupling agent is sprayed into the chamber while stirring the metal particles; a procedure in which water, a coupling agent, and an alkaline solution containing ammonia, sodium hydroxide, etc. are added to a primary alcohol such as methanol, ethanol, or isopropyl alcohol and stirred, the resulting dispersion is subjected to solid-liquid separation, and the resulting solid phase is dried.

[0129] After the coupling agent is introduced as described above, the metal particles may be heated as needed, which can stabilize the coating.

[0130] 2.2.Various properties of metal powders Next, various properties of the metal powder will be described.

[0131] 2.2.1.Particle size distribution When the particle size distribution of a metal powder is obtained on a volume basis using a laser diffraction particle size distribution analyzer, the particle size at which the cumulative frequency is 10% from the smallest diameter side is defined as D10. Similarly, the particle sizes at which the cumulative frequency is 50% and 90% from the smallest diameter side are defined as D50 and D90. An example of an apparatus for measuring particle size distribution is the Microtrac HRA9320-X100 manufactured by Nikkiso Co., Ltd.

[0132] The particle size D50 (average particle size D50) of the metal powder is preferably 1.0 μm or more and 15.0 μm or less, more preferably 2.0 μm or more and 10.0 μm or less, and even more preferably 3.0 μm or more and 8.0 μm or less. This allows the shaping particles 1 to have both good filling properties and good fluidity. As a result, a dense layered shaped body 6 with high shape accuracy can be obtained, and by using this, a metal sintered body with high density and high shape accuracy can be finally manufactured.

[0133] If the particle size D50 is below the lower limit, the particles of the shaping particles 1 may be more likely to aggregate. In this case, the fluidity of the shaping particles 1 may decrease, and the filling ability and shape accuracy of the layered object 6 may decrease. On the other hand, if the particle size D50 is above the upper limit, the particles of the shaping particles 1 may become too large. In this case, the particle shape may be more likely to be reflected on the surface of the layered object 6, and shape accuracy may decrease.

[0134] 2.2.2.Average circularity The average circularity of the metal powder is preferably 0.70 to 1.00, more preferably 0.80 to 0.98, and even more preferably 0.85 to 0.97. This allows the particles 1 to roll easily even when they have a small particle size, and allows the packed state to approach close packing. As a result, the packing ability and fluidity of the particles 1 can be both achieved. This allows for a dense layered shaped body 6 with high shape accuracy to be obtained, and by using this, a metal sintered body with high density and high shape accuracy can be finally produced.

[0135] If the average circularity is below the lower limit, the fluidity of the particles 1 may decrease and the filling rate may decrease. On the other hand, if the average circularity is above the upper limit, the difficulty of production may increase and the production efficiency of the particles 1 may decrease.

[0136] The average circularity of the metal powder is measured as follows. First, an image (secondary electron image) of the metal powder is taken using a scanning electron microscope (SEM). Next, the obtained image is loaded into image processing software. For example, image analysis particle size distribution measurement software "Mac-View" manufactured by Mountech Co., Ltd. is used as the image processing software. The imaging magnification is adjusted so that 50 to 100 particles are captured in one image. Then, multiple images are taken so that a total of 300 or more particle images are obtained.

[0137] Next, image processing software is used to calculate the circularity of 300 or more particle images and determine the average value. The average value obtained is the average circularity of the metal powder. Note that when the circularity is e, the area of ​​the particle image is S, and the perimeter of the particle image is L, the circularity e can be calculated using the following formula: e=4πS / L 2

[0138] 2.2.3.Oxygen content The oxygen content of the metal powder is preferably 1000 ppm to 4000 ppm by mass, more preferably 1500 ppm to 3500 ppm, and even more preferably 2000 ppm to 3000 ppm. When the oxygen content of the metal powder is within the above range, moisture adsorption can be suppressed while suppressing changes in properties over time. In other words, the particles for molding 1 have high storage stability.

[0139] If the oxygen content is below the lower limit, the oxide film on the surface of the metal powder particles may become thin, which may lead to deterioration over time. On the other hand, if the oxygen content is above the upper limit, the metal powder may easily adsorb moisture, which may increase the moisture content of the metal powder, which may reduce the fluidity of the metal powder 1.

[0140] The oxygen content of the metal powder is measured, for example, in accordance with the general rules for determining oxygen content in metallic materials as defined in JIS Z 2613: 2006. Specifically, the oxygen content can be measured using a LECO oxygen / nitrogen analyzer, TC-300 / EF-300, or a LECO oxygen / nitrogen / hydrogen analyzer, ONH836, or the like.

[0141] 3.Metal powder manufacturing method Next, an example of a method for producing metal powder will be described.

[0142] The metal powder may be produced by any method, for example, by atomization. In atomization, molten metal is allowed to flow down from a crucible and collide with a fluid, such as a liquid or gas, sprayed at high speed. The molten metal that collided with the fluid falls by inertia, causing the droplets to become spherical. As a result, it is possible to produce metal powder with a high average circularity and a relatively small specific surface area, despite its relatively small diameter.

[0143] The produced metal powder may be classified as needed by methods such as dry classification such as sieving classification, inertial classification, and centrifugal classification, and wet classification such as sedimentation classification.

[0144] 4.Method for manufacturing sintered metal bodies A metal sintered body is obtained by sintering the layered manufactured body 6. In the sintering process, the layered manufactured body 6 is heated to cause a sintering reaction.

[0145] FIG. 11 is a process diagram for explaining the method for producing a metal sintered body. The method for manufacturing a metal sintered body shown in Figure 11 includes a manufacturing process S202 in which an additive manufacturing body 6 is obtained by the above-mentioned method for manufacturing an additive manufacturing body, and a sintering process S204 in which the additive manufacturing body 6 is sintered to obtain a metal sintered body.

[0146] 4.1. Molding process In the modeling step S202, the layered object 6 is obtained by the above-described method for manufacturing a layered object.

[0147] 4.2.Sintering process In the sintering step S204, the layered manufactured body 6 is sintered to obtain a metal sintered body.

[0148] When the sintering process performed under the above conditions is referred to as "main sintering," the layered product 6 may be subjected to at least one of "pre-sintering" and "debinding," which correspond to pre-treatments prior to the main sintering, as needed. This makes it possible to remove at least a portion of the binder contained in the layered product 6 and sinter a portion of the layered product 6. This makes it possible to suppress unintended deformation during the main sintering.

[0149] The metal sintered body obtained as described above can be used as a material for constituting all or part of transportation equipment parts such as automobile parts, bicycle parts, railway vehicle parts, ship parts, aircraft parts, and space transport vehicle parts; electronic equipment parts such as personal computer parts, mobile phone terminal parts, tablet terminal parts, and wearable terminal parts; electrical equipment parts such as refrigerators, washing machines, and air conditioners; machine parts such as machine tools and semiconductor manufacturing equipment; plant parts such as nuclear power plants, thermal power plants, hydroelectric power plants, refineries, and chemical complexes; watch parts; and decorative items such as metal tableware, jewelry, and eyeglass frames.

[0150] 5. Effects of the above embodiment As described above, the method for manufacturing an additive manufacturing object according to the embodiment includes a powder layer forming step S102, an energy applying step S104, and a binder solution supplying step S106. In the powder layer forming step S102, metal particles and metal shaping particles 1 each having a coating formed on the surface of the metal particles and containing a compound derived from a coupling agent having a hydrophobic functional group are laid in a layer to form a powder layer 31. In the energy applying step S104, energy E is applied to the powder layer 31 so that the water contact angle of the metal shaping particles 1 is between 3° and 45°. In the binder solution supplying step S106, an aqueous binder solution 4 is supplied to the powder layer 31 that has undergone the energy applying step S104.

[0151] With this configuration, although the surfaces of the shaping particles 1 are already hydrophobic, the application of energy E can alleviate this hydrophobicity. As a result, the fluidity and packing ability of the shaping particles 1 are ensured before the application of energy E, and after the application of energy E, the shaping particles 1 are given appropriate hydrophilicity. Therefore, when the aqueous binder solution 4 is supplied to the powder layer 31 in the binder solution supplying step S106, the permeability of the aqueous binder solution 4 in the powder layer 31 can be improved. This makes it possible to manufacture an layered object 6 with high shape accuracy.

[0152] Furthermore, in the method for manufacturing a layered object according to the embodiment, the binder solution supplying step S106 may include a drying process for drying the powder layer 31 to which the aqueous binder solution 4 has been supplied.

[0153] This configuration can promote drying of the powder layer 31 to which the aqueous binder solution 4 has been supplied. This allows the penetration range of the aqueous binder solution 4 to be controlled as desired, further improving the shape precision of the final layered object 6 obtained.

[0154] Furthermore, in the method for manufacturing a layered object according to the embodiment, the powder layer forming step S102, the energy applying step S104, and the binder solution supplying step S106 are repeated multiple times. With this configuration, a layered object 6 having a desired three-dimensional shape can be obtained.

[0155] In the method for manufacturing a layered object according to the embodiment, the hydrophobic functional group is a group containing a cyclic structure.

[0156] According to this configuration, the particles 1 for shaping can be obtained that exhibit good fluidity and filling properties even when stored in a high-temperature, high-humidity environment, and therefore, a layered shaped body 6 with high shape accuracy can be finally manufactured.

[0157] In the method for manufacturing a layered object according to the embodiment, the cyclic structure-containing group is a phenyl group.

[0158] According to this configuration, the phenyl group has excellent heat resistance, which contributes to realizing the shaping particles 1 whose fluidity and filling properties are not easily reduced even when exposed to a high-temperature environment.

[0159] Furthermore, in the method for manufacturing a layered object according to the embodiment, the energy applying step S104 includes a process of irradiating with ultraviolet light having a wavelength of 253 nm or less for 30 seconds or more.

[0160] According to this configuration, an appropriate amount of energy E can be efficiently applied in a simple manner.

[0161] Furthermore, in the method for manufacturing a layered object according to the embodiment, the binder solution supplying step S106 includes a process of ejecting the water-based binder solution 4 as ink from the inkjet head 26 that moves relative to the powder layer 31.

[0162] With this configuration, the aqueous binder solution 4 can be supplied to the target position with high precision, thereby ultimately producing a layered object 6 with high shape precision.

[0163] In the method for manufacturing a layered object according to the embodiment, the average particle size of the metal particles is 1.0 μm or more and 15.0 μm or less.

[0164] This configuration achieves both the filling ability and fluidity of the shaping particles 1. As a result, a dense layered shaped body 6 with high shape accuracy can be obtained, and by using this, a metal sintered body with high density and high shape accuracy can be finally manufactured.

[0165] The method for manufacturing a layered object of the present invention has been described above based on the illustrated embodiment, but the present invention is not limited to this. For example, any desired process may be added to the embodiment. [Example]

[0166] Next, specific examples of the present invention will be described. 6. Manufacturing of particles for molding First, metal powders with different particle sizes were produced by water atomization under different manufacturing conditions. The metal powders were made of precipitation hardened stainless steel SUS630 (17-4PH).

[0167] Next, the average particle size D50, average circularity, and oxygen content of the produced metal powder were measured. The measurement results are shown in Tables 1 to 4.

[0168] Next, a coating was formed on the surface of the metal powder particles using a coupling agent shown in Tables 1 to 4. In this way, particles for shaping of each sample number were obtained.

[0169] In addition, the application of energy was omitted in Sample No. 1. In addition, the formation of a coating was omitted in Sample No. 9.

[0170] Furthermore, compound D-1 shown in Tables 1 to 4 is propyltrimethoxysilane, and compound D-2 is vinyltrimethoxysilane.

[0171] Next, energy was applied to the obtained particles for shaping using the application method and application time or scan speed shown in Tables 1 to 4. This reproduced the particles for shaping immediately before supplying the aqueous binder solution in the production of a layered object. The energy application conditions for each energy application method are as follows:

[0172] When the energy deposition method is ultraviolet irradiation, the wavelength of the ultraviolet light is 253 nm and the irradiance of the ultraviolet light is 5 mW / cm 2 It was decided.

[0173] When the energy application method was ozone treatment, the ozone concentration was 3% by volume, and the flow rate of the ozone-containing gas was 500 ccm.

[0174] When the energy application method was plasma irradiation, the plasma generation power was 1000 W and the flow rate of the plasma gas was 500 sccm.

[0175] In addition, in Tables 1 to 4, layered objects manufactured using a manufacturing method corresponding to the present invention are designated as "Examples," and layered objects manufactured using a manufacturing method not corresponding to the present invention are designated as "Comparative Examples."

[0176] 7. Evaluation of Particles for Fabrication 7.1. Packing properties of particles used for molding 50 g of the shaping particles of each sample No. was subjected to a heat treatment in an air atmosphere at 200°C for 24 hours. The heat-treated shaping particles were then placed in a 50 mL screw cap vial. The screw cap vial was then held upright and the height from the bottom to the top of the powder was measured. The measured height was then used to evaluate the packing ability of the shaping particles according to the following evaluation criteria. The evaluation results are shown in Tables 1 to 4.

[0177] A: Height is 25mm or less (especially high filling ability) B: Height is over 25mm and less than 30mm (slightly high filling ability) C: Height is over 30 mm (poor filling ability)

[0178] 7.2. Penetration time of aqueous binder solution into powder layer The shaping particles of each sample number were placed in a transparent container and compressed to a relative density of 50%, resulting in a packed body of shaping particles simulating a powder layer. The container was a rectangular prism-shaped container made of fluororesin, measuring 6.0 mm wide, 6.3 mm long, and 35.0 mm high.

[0179] Next, the container containing the filler was set in a contact angle meter. 25 μL of aqueous binder solution was dropped onto the filler, and the time it took for the aqueous binder solution to penetrate (penetration time) was measured using the contact angle meter. A PVP aqueous solution containing PVP at a concentration of 10% by mass and a humectant at a concentration of 12% by mass was used as the aqueous binder solution. The measured penetration time was then evaluated against the following evaluation criteria to evaluate the penetration time of the aqueous binder solution into the powder layer. The evaluation results are shown in Tables 1 to 4.

[0180] A: Penetration time is 10 seconds or less (penetration speed is particularly fast) B: Penetration time is more than 10 seconds and less than 30 seconds (slightly fast penetration speed) C: Penetration time is more than 30 seconds and less than 60 seconds (slightly slow penetration speed) D: The penetration speed is more than 60 seconds (the penetration speed is particularly slow)

[0181] 8. Evaluation of the additive manufacturing object 8.1. Density of the model used for density evaluation In 7.2, the aqueous binder solution was allowed to penetrate into the shaping particles, and then the aqueous binder solution was dried and solidified to obtain a shaped body for density evaluation, in which the shaping particles were bonded together by the binder.

[0182] The mass and volume of the obtained density evaluation objects were measured, and the density of the density evaluation objects was calculated from the measurement results. The density of the density evaluation objects was evaluated based on the calculation results against the following evaluation criteria. The evaluation results are shown in Tables 1 to 4.

[0183] A: The density of the model for density evaluation is particularly high. B: The density of the model for density evaluation is slightly high. C: The density of the object for density evaluation is low

[0184] 8.2. Shape accuracy of additively manufactured objects First, a rectangular parallelepiped-shaped additive manufacturing object was fabricated by binder jetting using the molding particles of each sample number. The thickness of each powder layer was 50 μm. The manufactured additive manufacturing object measured 40 mm in length, 20 mm in width, and 5 mm in thickness. The aqueous binder solution used was a PVP aqueous solution containing PVP and a humectant. The surface tension of the aqueous binder solution, the droplet volume, the inkjet head movement speed, and the droplet ejection interval of the aqueous binder solution were set to the values ​​shown in Tables 1 to 4.

[0185] The resulting layered object was then observed using a digital microscope that functions as a non-contact surface roughness measuring device. The arithmetic mean roughness Ra of the surface of the layered object was then measured based on the observation results. The shape accuracy of the layered object was then evaluated based on the measurement results against the following evaluation criteria. The evaluation results are shown in Tables 1 to 4.

[0186] A: The arithmetic mean roughness Ra is 4.0 μm or less (particularly high shape precision) B: The arithmetic mean roughness Ra is greater than 4.0 μm and less than 7.0 μm (shape accuracy is somewhat high) C: The arithmetic mean roughness Ra is greater than 7.0 μm and less than 10.0 μm (shape accuracy is somewhat low) D: The arithmetic mean roughness Ra is greater than 10.0 μm (particularly low shape accuracy)

[0187] [Table 1]

[0188] [Table 2]

[0189] [Table 3]

[0190] [Table 4]

[0191] As shown in Tables 1 to 4, in each example, the packing properties of the shaping particles were sufficiently high, and the powder layer formed using the shaping particles had good permeability for the aqueous binder solution. Furthermore, it was also found that the layered objects obtained in each example had high density and high shape accuracy. [Explanation of symbols]

[0192] 1... Particles for molding, 2... Layered molding device, 4... Aqueous binder solution, 6... Layered molded object, 21... Device body, 22... Powder supply elevator, 23... Molding stage, 24... Coater, 26... Inkjet head, 31... Powder layer, 41... Binder layer, 60... Formation area, 211... Powder storage section, 212... Molding section, E... Energy, S102... Powder layer formation process, S104... Energy application process, S106... Binder solution supply process, S108... Repeating process, S110... Removal process, S202... Molding process, S204... Sintering process

Claims

1. a powder layer forming step of laying metal particles and coatings formed on the surfaces of the metal particles, the coatings containing a compound derived from a coupling agent having a hydrophobic functional group, in a layered manner to form a powder layer; an energy applying step of applying energy to the powder layer so that the water contact angle of the particles for shaping becomes 3° or more and 45° or less; a binder solution supplying step of supplying an aqueous binder solution to the powder layer that has been subjected to the energy applying step; A method for manufacturing a layered object, comprising:

2. The method for manufacturing a layered object according to claim 1 , wherein the binder solution supplying step includes a drying process for drying the powder layer to which the aqueous binder solution has been supplied.

3. The method for manufacturing a layered object according to claim 1 or 2, wherein the powder layer forming step, the energy applying step, and the binder solution supplying step are repeated multiple times.

4. The method for producing a layered object according to claim 1 or 2, wherein the hydrophobic functional group is a group containing a cyclic structure.

5. The method for producing a layered object according to claim 4 , wherein the cyclic structure-containing group is a phenyl group.

6. The method for producing a layered object according to claim 1 or 2, wherein the energy application step includes a process of irradiating the substrate with ultraviolet light having a wavelength of 253 nm or less for 30 seconds or more.

7. The method for manufacturing a layered object according to claim 1 or 2, wherein the binder solution supplying step includes a process of ejecting the aqueous binder solution as ink from an inkjet head that moves relative to the powder layer.

8. The method for producing an additive manufacturing object according to claim 1 or 2, wherein the metal particles have an average particle size of 1.0 μm or more and 15.0 μm or less.

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