JP2015193035A - Method of manufacturing three-dimensional laminated formed object - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a three-dimensional laminated formed object, which enables a granular material of an unprinted part to be recycled without being regenerated, and which enables recoating to be properly performed without reference to the kind of the granular material.SOLUTION: A method of manufacturing a three-dimensional laminated formed object 20c includes a step (A) of stacking granular materials and performing an operation for carrying out printing by discharging a binder thereonto from a printing nozzle head 13, and a step (B) of making a gas hardener pass through a laminate of the granular materials and the binder.

Description

  The present invention relates to a method for manufacturing a three-dimensional layered object.

A mold is required to produce a casting. Examples of the mold include a thermosetting mold, a self-hardening mold, and a gas curing mold. For example, a self-hardening mold is a wooden mold or resin mold (hereinafter collectively referred to as “model”) filled with kneaded sand containing a refractory granular material, a curing agent, and a binder (binder). In general, it is produced by a method of curing the binder.
However, in order to manufacture a mold having a complicated shape, it is inevitably necessary to increase the number of models, resulting in complicated processes. Even if the number of models can be increased, the mold cannot be manufactured unless the mold can be removed from the model.

In order to solve these problems, in recent years, a method for producing a mold by three-dimensional additive manufacturing has been proposed, which can directly produce a mold without using a model.
The three-dimensional additive manufacturing is a method of manufacturing a mold using a three-dimensional shape input on a CAD (computer aided design) system as a direct three-dimensional model (three-dimensional model).

  As a method for producing a mold by three-dimensional additive manufacturing, the operation of laminating (recoating) kneaded sand containing a refractory granular material and a liquid curing agent, and printing a binder on the basis of CAD data thereon is repeated, A method of removing the kneaded sand in the non-printed part after the binder is cured (two-component self-hardening type) is known (for example, see Patent Document 1).

Japanese Patent No. 5249447

However, when a mold is manufactured by three-dimensional additive manufacturing of a two-component self-hardening mold, a hardener is blended in the non-printed portion of the kneaded sand. Regeneration such as baking was necessary.
In addition, depending on the type of the refractory granular material, the kneaded sand has poor fluidity and may be difficult to recoat.

  The present invention has been made in view of the above circumstances, and a method for producing a three-dimensional layered object that can be reused without regenerating the granular material of the non-printed portion and can be satisfactorily recoated regardless of the type of the granular material. The purpose is to provide.

The present invention has the following aspects.
[1] A step (A) of laminating a granular material, and performing a printing operation by discharging a binder from the printing nozzle head thereon, and a step of passing a gas curing agent through the laminate of the granular material and the binder (B And a method for producing a three-dimensional layered object.
[2] Steps (A) and (B) are simultaneously performed in an atmosphere in which a gas curing agent is introduced while degassing, and the introduction position of the gas curing agent is below the discharge port of the print nozzle head; and The method for producing a three-dimensional layered object according to [1], wherein the deaeration position is below the introduction position of the gas curing agent.
[3] The method for producing a three-dimensional layered object according to [2], wherein the gas curing agent is heavier than air.
[4] The method for producing a three-dimensional layered object according to any one of [1] to [3], wherein the laminate through which the gas curing agent has been passed is further cured.
[5] The method for producing a three-dimensional layered object according to any one of [1] to [4], wherein the binder is an acid curable binder and the gas curing agent is an acidic gas.
[6] The method for producing a three-dimensional layered object according to [5], wherein the acidic gas is carbon dioxide.
[7] The method for producing a three-dimensional layered object according to [5] or [6], wherein the acid curable binder is an acid curable resin.
[8] The method for producing a three-dimensional layered object according to [5] or [6], wherein the acid curable binder is water glass.
[9] The method for producing a three-dimensional layered object according to any one of [1] to [4], wherein the binder is an alkali phenol resin and the gas curing agent is an organic ester gas.
[10] The method for producing a three-dimensional layered object according to any one of [1] to [9], wherein the granular material is a refractory granular material.
[11] The method for producing a three-dimensional layered object according to [10], wherein the refractory granular material is artificial sand obtained by any one of a melting method, a sintering method, and a flame melting method.
[12] The method for producing a three-dimensional layered object according to any one of [1] to [11], wherein the three-dimensional layered object is a mold.

  According to the present invention, it is possible to provide a method for manufacturing a three-dimensional layered object that can be reused without regenerating the granular material of the non-printed portion and can be satisfactorily recoated regardless of the type of the granular material.

It is sectional drawing which illustrates typically the method of manufacturing a three-dimensional laminate modeling thing, performing a process (A) and a process (B) simultaneously. It is a perspective view which shows the column-shaped laminated body produced in [Example].

"Method for manufacturing three-dimensional layered objects"
The method for producing a three-dimensional layered object of the present invention includes a step of performing a printing operation (hereinafter referred to as “step (A)”) in which granular materials are laminated and a binder is discharged from a printing nozzle head on the printed material. And a step of passing a gas curing agent through the laminate of the particulate material and the binder (hereinafter referred to as “step (B)”).

<Process (A)>
Step (A) is a step in which a granular material is laminated, and a binder is ejected from the print nozzle head to perform printing.
The granular material is used in a dry state. Here, the “dry state” means that the free moisture measured based on JACT test method S-9 (casting sand moisture test method) is 0.1% or less. The specific measurement method is as follows.
First, 50 g of the granular material is weighed, put in a drier, dried at 105 to 110 ° C., cooled to room temperature in a desiccator, and then weighed. From the weight loss when this operation is repeated to reach a constant weight, free water is calculated by the following formula (1).
Free moisture [%] = (mass of granular material before drying [g] −mass of granular material after drying [g]) / mass of granular material before drying [g] × 100 (1)

Examples of the particulate material include sand, resin beads, and metal beads.
Sand having fire resistance is preferable, and natural sand such as quartz sand, olivine sand, zircon sand, chromite sand, alumina sand, mullite sand, etc. is used as the sand having fire resistance (hereinafter referred to as “fire-resistant granular material”). Examples include sand and artificial sand. Moreover, the thing which collect | recovered used artificial sand and natural sand, and the thing which recycled these can be used.
Artificial sand is generally obtained from bauxite as a raw material by any one of a melting method (atomizing method), a sintering method, and a flame melting method. Specific conditions of the melting method, sintering method, flame melting method and the like are not particularly limited, and are described in, for example, JP-A-5-169184, JP-A-2003-251434, and JP-A-2004-202577. Artificial sand may be manufactured using known conditions.

Examples of the resin used as a raw material for the resin beads include nylon-6, nylon-6,6, nylon-11, nylon-12, polypropylene, and polystyrene.
Examples of the metal used as a raw material for the metal beads include iron and titanium.

The average particle diameter of the granular material is preferably 50 to 300 μm, more preferably 75 to 150 μm. When the average particle diameter is 300 μm or less, a three-dimensional layered object having excellent surface roughness can be obtained.
In the step (A), a laminate in which the granular material and the binder are alternately laminated is obtained. When the granular material is too fine, the gas curing agent tends to hardly penetrate in the laminating direction of the laminate in the step (B). When the average particle diameter of the granular material is 50 μm or more, the gas curing agent easily penetrates into the laminate, and the binder is sufficiently cured. In addition, although mentioned later in detail, when performing a process (A) and a process (B) alternately, a gas hardening | curing agent can be ventilated from the state with a thin laminated body. Therefore, compared with the case where a process (B) is performed after a process (A), even if a granular material is fine, a gas hardening | curing agent penetrate | infiltrates easily.

Here, the average particle diameter of the granular material is a median diameter of 50% cumulative volume of the granular material measured by the dynamic light scattering method.
The “surface roughness” is the surface roughness in the stacking direction of the three-dimensional layered object.

A granular material is selected according to the intended purpose of the obtained three-dimensional layered object. For example, when the three-dimensional layered object is a mold, a refractory granular material is suitable as the granular material. In particular, artificial sand has high fire resistance and is not easily expanded by heat (excellent in low thermal expansion). If the thermal expansibility is large, vaning defects are likely to occur. Here, the vaning defect is a burr-like defect that is generated when a crack is generated in the mold due to expansion of the mold due to heat during casting, and molten metal flows into the crack. When artificial sand is used as the granular material, it is possible to produce a large mold or a mold that can withstand even when pouring high-temperature molten metal (that is, a vaning defect is unlikely to occur).
Since natural sand is cheaper than artificial sand, it is preferable to use natural sand alone or mixed with artificial sand from the viewpoint of reducing manufacturing costs. It is preferable to use a mixture of sand and artificial sand.
As natural sand, quartz sand is preferred. The reason is that, for example, zircon sand is relatively expensive among natural sands, chromite sand contains chromium, so it takes time to dispose of it, and olivine sand tends to increase the surface roughness of the three-dimensional layered object. Because.
In addition, from the viewpoint of cooling the mold, metal beads may be used as the granular material, and iron beads are particularly suitable from the viewpoint of cost.

The mold is a mold for casting a casting. After casting, the mold is disassembled to take out the casting. In other words, if the casting is the final object (final product), the mold is premised on being finally broken.
On the other hand, when the three-dimensional layered object is a final object (not premised on being finally destroyed), the granular material may be selected according to the use of the final object. For example, when manufacturing final blades such as wings and trays used for dolls, screws, etc., resin beads are suitable as the granular material.

Examples of the binder include an acid curable binder and an alkali phenol resin (but not used in combination with a boron compound described later).
Examples of the acid curable binder include acid curable resins and water glass. Here, the acid curable resin is a resin that is cured by the action of an acid gas.
Examples of the acid curable resin include a mixture of an alkali phenol resin and a boron compound, a resol type phenol resin, a furan resin, a urea-modified furan resin, and a phenol-modified furan resin.

The alkali phenol resin in the mixture of the alkali phenol resin and the boron compound is a resin that is cured by the action of the organic ester gas as described later, but becomes a resin that is cured by the action of the acidic gas when used in combination with the boron compound.
The alkali phenol resin is one or more selected from the group consisting of phenols and bisphenols (hereinafter referred to as “phenolic compounds”) and aldehydes in the presence of an alkali metal hydroxide in a conventional manner. Can be obtained by reacting in an aqueous system.
Examples of phenols include phenol, cresol, resorcin, nonylphenol, cashew nut shell liquid, and the like.
Examples of bisphenols include bisphenol A, bisphenol F, bisphenol C, bisphenol S, and bisphenol Z.
Examples of aldehydes include formaldehyde, paraformaldehyde, acetaldehyde, furfural, glyoxal, glutardialdehyde, phthalic acid dialdehyde, and the like.

  As the phenolic compound, either one of phenols and bisphenols may be used alone, or a mixture of phenols and bisphenols may be used. In particular, a co-condensation type resin composed of phenols and bisphenols is preferable as the phenolic compound in that a three-dimensional layered product having high strength is easily obtained.

Examples of the alkali metal hydroxide include sodium hydroxide, potassium hydroxide, and lithium hydroxide. Among these, sodium hydroxide and potassium hydroxide are preferable. These alkali metal hydroxides may be used alone or in combination of two or more.
The amount of the alkali metal hydroxide used is preferably 0.5 to 4.0 times mol, more preferably 0.8 to 3.5 times mol, and 1.0 to 1.0 mol based on the total number of moles of the phenolic compound. 3.0 times mole is particularly preferable. If the usage-amount of an alkali metal hydroxide is 0.5 times mol or more with respect to the total number of moles of a phenolic compound, the intensity | strength of a three-dimensional laminate molding will increase. On the other hand, if the amount of the alkali metal hydroxide used is 4.0 times or less the total number of moles of the phenolic compound, it is possible to prevent the alkali metal hydroxide from becoming excessive. It is possible to prevent the working environment from being deteriorated by the hydroxide.

  The amount of aldehyde used is preferably 1.0 to 3.5 times mole, more preferably 1.1 to 2.5 times mole, and 1.5 to 2.0 times the total number of moles of the phenolic compound. Mole is particularly preferred. If the usage-amount of aldehydes is 1.0 times mole or more with respect to the total number of moles of a phenol type compound, the intensity | strength of a three-dimensional laminate molding will increase. On the other hand, when the amount of aldehyde used is 3.5 times or less of the total number of moles of the phenolic compound, the amount of unreacted aldehyde remaining in the alkali phenol resin can be reduced. When many unreacted aldehydes remain in the alkali phenol resin, there is a tendency for harmful aldehydes to be generated more frequently during additive manufacturing.

  In addition, when making a phenol type compound and aldehyde react, you may add the monomer (For example, urea, cyclohexanone, a melamine etc.) which can be condensed with an aldehyde in a reaction system. Moreover, you may dilute the obtained alkali phenol resin so that it may become a desired density | concentration with monohydric alcohols (for example, methanol, ethanol, propanol, etc.).

The boron compound in the mixture of the alkali phenol resin and the boron compound serves to rapidly cure the alkali phenol resin by the action of the acid gas.
Examples of the boron compound include sodium tetraborate decahydrate (borax), potassium borate decahydrate, sodium metaborate, sodium pentaborate, potassium pentaborate and the like. Further, boric acid may be used as the boron compound. In addition, boric acid reacts with an alkali by mixing with alkali phenol resin, and becomes borate. These boron compounds may be used alone or in combination of two or more.
0.1-20 mass parts is preferable with respect to 100 mass parts of alkali phenol resins, and, as for the addition amount of a boron compound, 1-10 mass parts is more preferable. If the addition amount of the boron compound is 0.1 parts by mass or more, a sufficient curing speed can be obtained, and the strength of the three-dimensional layered object can be increased. On the other hand, if the addition amount of the boron compound is 20 parts by mass or less, the miscibility with the particulate material is sufficient.

  Furthermore, for the purpose of increasing the strength of the three-dimensional layered object, a salt of a metal that binds the phenolic compound to an ionomer, a glycol, a silane coupling agent, or the like may be added to the mixture of the alkali phenol resin and the boron compound. Good.

Examples of the metal salt that forms an ionomer bond with a phenol compound include aluminates such as sodium aluminate, potassium aluminate, and lithium aluminate; stannates such as sodium stannate, potassium stannate, and lithium stannate; titanic acid Examples thereof include titanates such as sodium and potassium titanate. These metal salts may be used alone or in combination of two or more.
0.1-1.0 mass part is preferable with respect to 100 mass parts of alkali phenol resins, and, as for the addition amount of a metal salt, 0.3-0.6 mass part is more preferable. If the addition amount of the metal salt is 0.1 parts by mass or more, the effect of improving the strength of the three-dimensional layered object can be sufficiently obtained. The effect of improving the strength of the three-dimensional layered object tends to be obtained as the amount of the metal salt added increases. Therefore, the addition amount of the metal salt is preferably 1.0 part by mass or less.

Examples of glycols include diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl. Ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monopropyl ether, triethylene glycol monobutyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, etc. These glycols may be used individually by 1 type, and may use 2 or more types together.
As for the addition amount of glycols, 1-20 mass parts is preferable with respect to 100 mass parts of alkali phenol resins. If the addition amount of glycols is 1 part by mass or more, the effect of improving the strength of the three-dimensional layered object is sufficiently obtained. The effect of improving the strength of the three-dimensional layered object tends to be obtained as the added amount of glycols increases. Therefore, the addition amount of glycols is preferably 20 parts by mass or less.

Examples of the silane coupling agent include γ-aminopropyltriethoxysilane, γ- (2-aminoethyl) aminopropyltrimethoxysilane, and γ-glycidoxypropyltrimethoxysilane. These silane coupling agents may be used alone or in combination of two or more.
0.01-3.0 mass parts is preferable with respect to 100 mass parts of alkali phenol resins, and, as for the addition amount of a silane coupling agent, 0.1-2.0 mass parts is more preferable. If the addition amount of a silane coupling agent is 0.01 mass part or more, the effect which improves the intensity | strength of a three-dimensional laminate modeling thing will fully be acquired. The effect of improving the strength of the three-dimensional layered object tends to be obtained as the addition amount of the silane coupling agent increases, but the effect only reaches a limit even if it increases too much. Therefore, the addition amount of the silane coupling agent is preferably 3.0 parts by mass or less.

It does not specifically limit as water glass, A conventionally well-known thing can be used. For example, sodium silicate (specifically, No. 1, No. 2, No. 3, sodium metasilicate (1 type, 2 types) described in JIS K 1408: 1966), potassium silicate, or a mixture thereof may be used. it can.
As the water glass, it is preferable that SiO ₂ and M (M = _{K 2} O or _Na 2 O) molar ratio of _(SiO 2 / M) is used water glass is 1.6 to 4.0, moles It is more preferable to use water glass having a ratio of 2.15 to 2.5. When the molar ratio is small, the curing rate is slow and the adhesive strength tends to be high. Conversely, when the molar ratio is increased, the curing rate is increased and the adhesive strength tends to be decreased.

  The degree of Baume at 25 ° C. of water glass is preferably 36-44. When the Baume degree of water glass becomes small, the amount of water increases so that the strength of the three-dimensional layered object may be lowered. Conversely, when the baume degree of the water glass increases, the viscosity of the water glass tends to increase and become difficult to handle.

When an alkali phenol resin (but not used in combination with the above-described boron compound) is used as a binder, the alkali phenol resin is a resin that is cured by the action of an organic ester gas.
As an alkali phenol resin, the alkali phenol resin illustrated previously in description of acid curable resin is mentioned.

  As the binder, those other than the above-mentioned acid curable binder and alkali phenol resin may be used. For example, a mixture of a phenol resin and a urethane resin can be used. However, when a mixture of a phenol resin and a urethane resin is used as the binder, an amine gas is suitable as the gas curing agent used in the step (B), as will be described in detail later. This amine gas may worsen the working environment. Therefore, the binder is preferably an acid curable binder or an alkali phenol resin that can be cured by the action of a gas curing agent other than amine gas.

The step of performing the operation of stacking the granular material and discharging the binder from the print nozzle head for printing is performed as follows, for example.
First, a granular material is installed in the three-dimensional laminating apparatus using a blade mechanism having a recoater using a three-dimensional laminating apparatus (for example, Professional RCT S-print (registered trademark), distributor: EX ONE Co., Ltd.) using a printing modeling method Laminated on the bottom of the metal case. Next, a binder is printed on the laminated granular material by scanning the print nozzle head based on data obtained by 3D CAD design of the shape of the three-dimensional layered object. The bottom surface of the metal case serves as a modeling table and can be moved up and down. After printing the binder, the bottom surface (modeling table) of the metal case is lowered further, the granular material is laminated in the same manner as described above, and the binder is printed thereon. The process (A) consisting of these lamination and printing is repeated. The thickness of one layer is preferably 100 to 500 μm, and more preferably 200 to 300 μm.

  Although it does not restrict | limit especially as an application quantity at the time of printing a binder, When the mass of the granular material for one layer is 100 mass parts, the application quantity used as 0.4-10 mass parts is preferable, 0.8-5 A coating amount that is part by mass is more preferable.

<Process (B)>
Step (B) is a step of passing a gas curing agent through the laminate of the particulate material and the binder. By passing the gas curing agent, the binder is cured, and a three-dimensional layered product is obtained.
The gas curing agent is a gasification of the curing agent, and is appropriately selected and used according to the type of binder used in the step (A).
For example, when an acid curable binder is used as the binder, an acid gas is suitable as the gas curing agent. Examples of the acid gas include carbon dioxide gas, sulfurous acid gas, and hydrogen chloride gas. Among these, carbon dioxide is preferable because it is easy to handle and hardly affects the work environment.
On the other hand, when an alkali phenol resin (but not used in combination with the above-described boron compound) is used as the binder, an organic ester gas is suitable as the gas curing agent. Examples of the organic ester gas include methyl formate gas and ethyl formate gas.
Moreover, when using the mixture of a phenol resin and a urethane resin as a binder, amine gas is suitable as a gas hardening | curing agent. Examples of the amine gas include triethylamine gas and dimethylethylamine gas.

  The step (B) may be performed after all the plurality of steps (A) to be repeated are completed, the step (A) and the step (B) may be performed alternately, or the step (A) and the step (B) may be performed simultaneously. However, when the process (A) and the process (B) are performed alternately, the last is the process (B).

When the step (B) is performed after the completion of the step (A), the laminate of the particulate material and the binder is taken out from the three-dimensional laminating apparatus together with the metal case, and the metal case is installed in the sealed case. After reducing the pressure to a gas curing agent, the binder is cured. This method is called a VRH method (Vacuum Replacement Hardening Process).
When the step (B) is performed after the completion of the step (A), the amount (replacement amount) required to replace the air in the sealed case with the gas curing agent varies depending on the volume of the sealed case, but the volume is 0%. .9 to 2.0 times the amount is preferable, and the same amount as the volume is more preferable. For example, when the size of the sealed case is 1000 mm × 800 mm × 700 mm, the volume is 560 L. Therefore, the replacement amount of the gas curing agent is 504 L or more, which is 0.9 times the main volume, and 2 of the main volume. It is preferably 1120 L or less, which is a double amount, and more preferably 560 L which is the same amount as the main volume. If the replacement amount of the gas curing agent is 0.9 times the volume or more, the binder is sufficiently cured. On the other hand, if the replacement amount of the gas curing agent is 2.0 times the volume or less, the sealed case can sufficiently withstand the gas pressure.
The time for curing the binder (curing reaction time) is preferably 60 to 300 seconds, and more preferably 120 to 180 seconds. If the curing reaction time is 60 seconds or more, the binder is sufficiently cured, but the binder is hardened even if it exceeds 300 seconds. The curing reaction time is the time from immediately after the start of replacement with the gas curing agent in the sealed case until the sealed case is opened.

When the step (A) and the step (B) are performed alternately, for example, the metal case installation part of the three-dimensional laminating apparatus is hermetically sealed and decompressed, and the first granular material is placed on the bottom surface of the metal case (the modeling table ), A binder is printed thereon, and then a gas curing agent is aerated while reducing the pressure. Next, the pressure reduction and the aeration of the gas curing agent are stopped, the bottom surface (modeling table) of the metal case is lowered further, the granular material is laminated in the same manner as described above, and the binder is printed on the gas curing agent. Repeat the operation to ventilate.
When the step (A) and the step (B) are alternately performed, the flow rate of the gas curing agent may be an amount sufficient for the binder to be cured, but the volume of the laminate laminated at one pitch is sufficient. The flow rate is preferably 3 to 25 times, and more preferably 8 to 15 times. For example, if the volume of the laminate laminated at 1 pitch per minute is 1 L, the gas curing agent aeration flow rate is preferably 3 to 25 L, more preferably 8 to 15 L per minute. If the flow rate of the gas curing agent is at least three times the volume of the laminate laminated at one pitch, the binder is sufficiently cured. On the other hand, if the flow rate of the gas curing agent is 25 times or less the volume of the laminate laminated at one pitch, the strength of the three-dimensional laminate shaped article can be maintained. Further, the wind pressure does not become too strong, and the granular material is not easily scattered.
The time for allowing the gas curing agent to pass is not particularly limited. However, if the next layer is laminated after the binder is completely cured, sufficient adhesion between layers may not be obtained, and delamination may occur. Therefore, when the step (A) and the step (B) are performed alternately, it is preferable to stack the next layer before the binder is completely cured, and the ventilation time is set in consideration of the curing time of the binder. It is preferable to do.

When performing a process (A) and a process (B) simultaneously, it is preferable to carry out in the atmosphere which introduce | transduces a gas hardening agent, deaerating. Hereinafter, an example of a method for simultaneously performing the step (A) and the step (B) will be described in detail with reference to FIG. In addition, the method shown in FIG. 1 is a method of performing a process (A) and a process (B) simultaneously using the three-dimensional laminating apparatus using the printing modeling method.
A three-dimensional laminating apparatus in which a metal case 10 having an introduction port 11 for introducing a gas curing agent into the metal case 10 and a deaeration port 12 for degassing the inside of the metal case 10 at predetermined positions is installed. The deaeration pump (not shown) is connected to the deaeration port 12 and the inside of the metal case 10 is deaerated. Simultaneously with the deaeration, the gas curing agent is introduced into the metal case 10 from the inlet 11. Under such an atmosphere in which a gas curing agent is introduced while degassing, the first-layer granular material is laminated on the bottom surface (modeling table) 10a of the metal case, and a binder is discharged from the printing nozzle head 13 on the printed material. To do. Subsequently, in an atmosphere in which a gas curing agent is introduced while degassing, the bottom surface (modeling table) 10a of the metal case 10 is lowered by one layer, a granular material is laminated in the same manner as above, and a binder is printed thereon. Repeat the operation.

The introduction position of the gas curing agent (in the case of FIG. 1, the position of the introduction port 11) is preferably located below the discharge port 13 a of the print nozzle head 13. If the introduction position of the gas curing agent is below the discharge port 13 a of the print nozzle head 13, the binder is not easily exposed to the gas curing agent in the print nozzle head 13, so that it is difficult to cure. Therefore, clogging of the print nozzle head 13 can be suppressed.
The deaeration position (the position of the deaeration port 12 in the case shown in FIG. 1) is preferably located below the introduction position of the gas curing agent. If the deaeration position is below the gas curing agent introduction position, the gas curing agent flows from the upper side to the lower side in the metal case 10, that is, from the introduction port 11 to the deaeration port 12. The gas curing agent is sufficiently distributed to the laminate 20.
In the case of FIG. 1, the introduction port 11 is provided at a position above the wall 10 b of the metal case 10, specifically below the discharge port 13 a of the print nozzle head 13 and at a height near the lamination surface 20 a of the laminate 20. The deaeration port 12 is provided on the bottom surface (modeling table) 10 a of the metal case 10. Here, the “lamination surface” is the surface of the uppermost layer of the laminate.
In particular, it is preferable that the introduction port 11 and the deaeration port 12 are positioned substantially on a diagonal line. If the introduction port 11 and the deaeration port 12 are located on a diagonal line, the gas curing agent is more easily spread throughout the metal case 10, and the binder is more easily cured.

When performing the step (A) and the step (B) at the same time, the amount of the gas curing agent introduced may be an amount sufficient for the binder to be cured, but the volume of the laminate laminated at one pitch is 3 The introduction amount is preferably ˜25 times, more preferably 8 to 15 times. For example, if the volume of the laminate laminated at 1 pitch per minute is 1 L, the amount of the gas curing agent introduced is preferably 3 to 25 L, more preferably 8 to 15 L per minute. If the amount of the gas curing agent introduced is at least three times the volume of the laminate laminated at one pitch, the binder is sufficiently cured. On the other hand, if the introduction amount of the gas curing agent is not more than 25 times the volume of the laminate laminated at one pitch, the strength of the three-dimensional laminate shaped article can be maintained. Further, the wind pressure does not become too strong, and the granular material is not easily scattered.
In particular, when the step (A) and the step (B) are performed simultaneously, the gas curing agent is preferably heavier than air. If the gas curing agent is heavier than air, the gas curing agent is likely to sink to the bottom of the metal case 10 when introduced into the metal case 10, and the gas curing agent spreads more sufficiently to the laminate 20. Moreover, since it becomes difficult for the binder to be exposed to the gas curing agent in the print nozzle head 13, the clogging of the print nozzle head 13 can be further suppressed.

In addition, when performing a process (A) and a process (B) alternately, or when performing a process (A) and a process (B) simultaneously, the gas hardening | curing agent was ventilated after these processes were completed. The laminate may be further cured. Here, the curing when the step (A) and the step (B) are alternately performed, or the curing when the step (A) and the step (B) are performed simultaneously is called “precure”, and the step (A) and Curing performed after alternately performing the step (B) or curing performed after performing the step (A) and the step (B) at the same time is referred to as “post cure”.
By performing post-cure after pre-cure, the binder is more fully cured.
Examples of the post-cure method include a method of heating the laminate, a method of irradiating the laminate with microwaves, and a VRH method.

For example, as shown in FIG. 1, the binder printed portion 20 b of the laminate 20 is in a non-bonded state only in the step (A), but the binder is cured by passing a gas curing agent in the step (B). Then, it can be in a combined state.
On the other hand, the binder non-printing portion 20c of the laminate 20 is in a non-bonded state even after the step (B) because no binder is present. Therefore, the particulate material of the binder non-printing part is removed with a brush or a vacuum cleaner to obtain a three-dimensional layered object.

<Effect>
According to the present invention, since the gas curing agent is used as the binder curing agent, no curing agent is added to the particulate material. Therefore, since the binder non-printing part of the laminate is made of only the granular material, the non-printing part of the granular material can be reused without reprocessing. In addition, since the hardener is not blended in the granular material, it can be satisfactorily recoated regardless of the type of the granular material.

By the way, when natural sand such as silica sand is used as a granular material and a mold is manufactured as a three-dimensional layered object, the obtained mold is likely to have the above-mentioned vaning defects. The reason for this is considered as follows.
Since natural sand has a phase transition point, it expands in volume by heat during casting. In particular, the inner side of the mold (the part in contact with the molten metal) is easily expanded due to the heat of the molten metal, but is less likely to expand because the heat of the molten metal is less likely to be transmitted closer to the outer side of the mold. It is considered that cracks are generated inside the mold due to the difference in expansion between the inside and the outside.

On the other hand, artificial sand hardly undergoes a phase transition, and therefore hardly expands due to heat during casting. Therefore, a mold manufactured using artificial sand is less likely to cause vaning defects.
However, as described above, when a mold is manufactured by a two-component self-hardening mold, a liquid curing agent is blended with artificial sand and recoated. However, when a liquid curing agent is blended with artificial sand, fluidity is lowered. The recoating property was apt to decrease.

In order to improve the fluidity of artificial sand, there is also a method of blending a liquid hardener with a mixture of artificial sand and natural sand.
However, the mold obtained by this method can withstand the molten metal pouring temperature when it is low (for example, when pouring aluminum), but when the pouring temperature becomes high (for example, when pouring iron) ) Unable to withstand that temperature. Therefore, it has been difficult to produce a large mold. This is because vaning defects are more likely to occur as the mold becomes larger. The reason is considered as follows.
The molten metal poured into the mold cools and hardens from the outside (the part in contact with the mold) from the central part. When the mold is small, the molten metal cools in a short time, so that the outer molten metal cools and solidifies before the crack occurs in the mold, and even if a crack occurs in the mold, the molten metal can be prevented from flowing into the crack. it is conceivable that. On the other hand, when the mold is large, it takes a long time for the molten metal to cool down, so that it is considered that a crack occurs in the mold before the outer molten metal hardens, resulting in a vaning defect.

  However, if it is this invention, since a hardening | curing agent is not mix | blended with a granular material, the problem of the fluidity | liquidity which arises when using artificial sand as a granular material can be solved. That is, according to the present invention, since artificial sand can be used alone, recoating can be performed, so that a mold that can endure even when pouring high-temperature molten metal (that is, less likely to cause vaning defects) can be manufactured. .

  In the case of the two-component self-hardening type as described above, there is a usable time, but in the present invention, the binder is cured with a gas curing agent, so there is no usable time and the workability is excellent.

By the way, the air permeability of the gas curing agent is affected by the average particle diameter of the granular material, and the larger the average particle diameter, the better the air permeability.
Since the average particle diameter of a granular material used for a normal mold such as a gas curing mold is relatively large at about 350 μm, the gas curing agent has good air permeability.
On the other hand, when a mold is manufactured by three-dimensional additive manufacturing, the average particle diameter of the granular material used is as small as 50 to 300 μm, so that it is difficult to obtain sufficient gas curing agent breathability. Therefore, when the gas curing agent is passed through the laminate of the particulate material and the binder by the VRH method or the like, the gas curing agent is difficult to penetrate into the laminate unless the inside of the sealed case is sufficiently depressurized. Only the surface is cured. However, if the pressure is reduced too much, the particulate material tends to scatter. In the case of the VRH method, as described above, the laminate is placed in the sealed case together with the metal case to cure the binder. That is, since the laminate in which the binder is in an uncured state is moved, there is a possibility that the laminate is displaced.

However, when the step (A) and the step (B) are performed alternately, the binder can be cured layer by layer. On the other hand, when performing a process (A) and a process (B) simultaneously, the part laminated | stacked can be hardened each time. Therefore, even if the average particle diameter of the granular material is small, the gas curing agent easily penetrates into the granular material, and the binder can be sufficiently cured. In addition, since the gas curing agent easily penetrates into the granular material, it is not necessary to expose it to a strong reduced pressure, and the scattering of the granular material can be suppressed.
Further, after alternately performing the step (A) and the step (B) or simultaneously performing the step (A) and the step (B), the laminate is further cured (post-cured) by the VRH method or the like. Even in this case, since the laminate is already cured to some extent, even if the laminate is moved, the laminate is not easily displaced.

<Other embodiments>
The manufacturing method of the three-dimensional layered object of the present invention is not limited to the method described above. For example, when performing the step (A) and the step (B) at the same time, in the example shown in FIG. 1, the deaeration port 12 is provided at one place on the bottom surface 10a of the metal case 10, but at a plurality of places on the bottom surface 10a. It may be provided, or may be provided at one or more locations on the wall 10b as long as it is below the inlet 11.
Further, for example, one or more protrusions may be provided on the inner side of the wall 10 b so that the gas curing agent can be swiveled in the metal case 10.

  Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto. The binder used in each example is shown below. Moreover, the measuring method of the free water | moisture content of the granular material used in each example, and the measuring method of the thermal expansion coefficient of the test piece obtained in each example are shown below.

"Binder"
<Preparation of acid curable resin>
A 1 L four-necked flask equipped with a thermometer, a stirrer, and a condenser was charged with 94 g (1 mol) of phenol, and while stirring, 101 g (0.9 mol) of 50 wt% potassium hydroxide, 92 wt% paraformaldehyde 65.2 g (2.17 mol) was added slowly. Next, this solution was heated to 90 ° C. and reacted at 90 ° C. for 3 hours to obtain an alkali phenol resin.
After the reaction, 260.2 g of the above alkaline phenol resin cooled to 40 ° C. or lower, 123.4 g of 50 mass% potassium hydroxide, 30 g of sodium tetraborate decahydrate, 1.9 g of γ-aminopropyltriethoxysilane, 125.0 g of water was added to obtain an acid curable resin.

<Water glass>
As water glass, an aqueous solution of sodium silicate (molar ratio (SiO ₂ / Na ₂ O): 2.50, Baume degree: 40 (25 ° C.)) was used.

<Preparation of furan binder>
88.2 parts by mass of furfuryl alcohol, 9.0 parts by mass of bisphenol A, 1.0 part by mass of resorcinol, and 0.2 parts by mass of aminosilane were mixed to obtain a furan binder.

"Measuring method"
<Measurement of free water>
The free moisture of the granular material was measured as follows based on JACT test method S-9 (water test method for foundry sand).
50 g of the granular material was weighed, put in a drier, dried at 105 to 110 ° C., cooled to room temperature in a desiccator, and then weighed. From the weight loss when this operation was repeated to reach a constant weight, free water was calculated by the following formula (1).
Free moisture [%] = (mass of granular material before drying [g] −mass of granular material after drying [g]) / mass of granular material before drying [g] × 100 (1)

<Measurement of thermal expansion coefficient>
The thermal expansion coefficient of the test piece was measured as follows based on JACT test method M-2 (rapid thermal expansion coefficient measurement test method in the thermal expansion test method).
The test piece was inserted into a furnace heated to 1000 ° C., the amount of expansion was measured with a thermal dilatometer for 5 minutes, and the coefficient of thermal expansion was calculated by the following formula (2).
Coefficient of thermal expansion [%] = expansion amount [mm] / length of test piece before heating [mm] × 100 (2)

"Experiment 1"
Artificial sand obtained by a melting method (“Isandaki # 1000”, average particle size 106 μm, free water 0%) obtained by a melting method was used as a granular material.
An acid curable resin was used as the binder.
Carbon dioxide gas was used as a gas curing agent.

A metal using a three-dimensional laminating apparatus (Prometal RCT S-print (registered trademark), sold by EX ONE Co., Ltd.) using a printing molding method, and a granular material placed in the three-dimensional laminating apparatus by a blade mechanism having a recoater Laminated on the bottom of the case. Next, a binder was printed on the laminated granular material by scanning the print nozzle head based on data obtained by 3D CAD design of the shape of the three-dimensional layered object. After printing the binder, the bottom surface (modeling table) of the metal case was lowered by one layer (280 μm), the granular material was laminated in the same manner as before, and the binder was printed thereon (step (A)). The step (A) consisting of lamination and printing was repeated to produce a cylindrical laminate 30 having a diameter d of 30 mm and a length l of 50 mm as shown in FIG.
Note that three types of laminates were produced by repeating the step (A) of laminating granular materials in three directions of the X axis, Y axis, and Z axis shown in FIG. 2 and printing a binder thereon. At that time, whether or not lamination was possible in each direction (whether or not lamination modeling was possible) was visually confirmed. The results are shown in Table 1.

After printing, the laminate of the particulate material and the binder is taken out from the three-dimensional laminating apparatus together with the metal case, and the metal case is placed in a sealed case (volume: 1000 mm × 800 mm × 700 mm). The binder was cured by replacing air with a gas curing agent (step (B)). The replacement amount of the gas curing agent was 560 L, and the curing reaction time was 180 seconds.
Subsequently, the granular material of the binder non-printing part was removed with a brush to obtain a cylindrical test piece (three-dimensional layered object) having a diameter of 30 mm and a length of 50 mm.
The thermal expansion coefficient of each obtained test piece was measured. The results are shown in Table 1.
Moreover, the granular material of the binder non-printing part was reused as reusable sand without being recycled.

"Experimental example 2"
Test piece in the same manner as in Experimental Example 1, except that artificial sand obtained by a sintering method (“Cerabead # 1450”, average particle size 106 μm, free water 0%) manufactured by the sintering method was used as a granular material. Were made and evaluated. The results are shown in Table 1.
Moreover, the granular material of the binder non-printing part was reused as reusable sand without being recycled.

"Experiment 3"
Artificial sand obtained by the flame melting method (“Lunamos MS # 110” manufactured by Kao Quaker Co., Ltd., average particle size 106 μm, free water 0.02%) was used as a granular material in the same manner as in Experimental Example 1. Test pieces were prepared and evaluated. The results are shown in Table 1.
Moreover, the granular material of the binder non-printing part was reused as reusable sand without being recycled.

"Experimental example 4"
A test piece was prepared and evaluated in the same manner as in Experimental Example 1 except that water glass was used as the binder. The results are shown in Table 1.
Moreover, the granular material of the binder non-printing part was reused as reusable sand without being recycled.

“Experimental Example 5”
Experiments were conducted except that artificial sand obtained by a sintering method (“Cerabead # 1450”, average particle size 106 μm, free moisture 0%) was used as a granular material, and water glass was used as a binder. Test pieces were prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1.
Moreover, the granular material of the binder non-printing part was reused as reusable sand without being recycled.

"Experimental example 6"
Artificial sand obtained by the flame melting method (“Lunamos MS # 110” manufactured by Kao Quaker Co., Ltd., average particle size 106 μm, free water 0.02%) is used as a granular material, and water glass is used as a binder. Produced a test piece in the same manner as in Experimental Example 1 and evaluated it. The results are shown in Table 1.
Moreover, the granular material of the binder non-printing part was reused as reusable sand without being recycled.

"Experimental example 7"
Artificial sand (Ito Kiko Co., Ltd., “Alsand # 1000”, average particle size 106 μm, free moisture 0%) obtained by the melting method as a granular material and silica sand (FS-001-EU, distributor: EX Co., Ltd.) A test piece was prepared and evaluated in the same manner as in Experimental Example 1 except that mixed sand in which ONE, an average particle size of 106 μm, and a free water content of 0.02% were mixed at a mass ratio of 60:40 was used. The results are shown in Table 1.
Moreover, the granular material of the binder non-printing part was reused as reusable sand without being recycled.

"Experimental example 8"
A test piece was prepared in the same manner as in Experimental Example 1 except that silica sand (FS-001-EU, distributor: EX ONE Co., Ltd., average particle size 106 μm, free water 0.02%) was used as the granular material. evaluated. The results are shown in Table 1.
Moreover, the granular material of the binder non-printing part was reused as reusable sand without being recycled.

"Comparative Example 1"
A curing agent was prepared by mixing 55 parts by mass of para-toluenesulfonic acid and 45 parts by mass of water. 0.3 parts by mass of this curing agent was added to 100 parts by mass of artificial sand (“Isanda # 1000” manufactured by Ito Kiko Co., Ltd., average particle size 106 μm, free water 0%) obtained by a melting method, and kneaded. It was kneaded sand.
A test piece was prepared in the same manner as in Experimental Example 1 except that the obtained kneaded sand was used instead of the granular material. However, the sand was agglomerated and the kneaded sand could not be recoated.

"Comparative Example 2"
0.3 parts by mass of the curing agent prepared in Comparative Example 1 is added to 100 parts by mass of silica sand (FS-001-EU, distributor: EX ONE Corporation, average particle size 106 μm, free water 0.02%) and kneaded. And kneaded sand.
A cylindrical laminate having a diameter of 30 mm and a length of 50 mm was prepared in the same manner as in Experimental Example 1 except that the obtained kneaded sand was used in place of the particulate material and a furan binder was used as the binder (two-component type). Self-hardening type). Three types of laminates were produced by repeating the step (A) of laminating kneaded sand in three directions of the X axis, Y axis, and Z axis, and printing a binder thereon.
After the completion of printing, after the binder was cured, the kneaded sand in the non-printed portion of the binder was removed with a brush to obtain a cylindrical test piece (three-dimensional layered object) having a diameter of 30 mm and a length of 50 mm.
The thermal expansion coefficient of each obtained test piece was measured. The results are shown in Table 2.
Further, the kneaded sand of the binder non-printed part was reused as reused sand after being regenerated by roasting.

“Comparative Example 3”
0.3 parts by mass of the curing agent prepared in Comparative Example 1 was mixed with artificial sand (manufactured by Ito Kiko Co., Ltd., “Alsand # 1000”, average particle size 106 μm, free water 0%) and quartz sand (FS-001-EU, Vendor: EX ONE Co., Ltd., average particle size 106 μm, free water 0.02%) was added to 100 parts by mass of mixed sand mixed at a mass ratio of 60:40 and kneaded to obtain kneaded sand.
A cylindrical laminate having a diameter of 30 mm and a length of 50 mm was prepared in the same manner as in Experimental Example 1 except that the obtained kneaded sand was used in place of the particulate material and a furan binder was used as the binder (two-component type). Self-hardening type). Three types of laminates were produced by repeating the step (A) of laminating kneaded sand in three directions of the X axis, Y axis, and Z axis, and printing a binder thereon.
After the completion of printing, after the binder was cured, the kneaded sand in the non-printed portion of the binder was removed with a brush to obtain a cylindrical test piece (three-dimensional layered object) having a diameter of 30 mm and a length of 50 mm.
The thermal expansion coefficient of each obtained test piece was measured. The results are shown in Table 2.
Further, the kneaded sand of the binder non-printed part was reused as reused sand after being regenerated by roasting.

The granular material used in each experimental example was excellent in fluidity, and could be recoated well in any of the X-axis, Y-axis, and Z-axis directions. In addition, the granular material in the non-printed part could be reused without reprocessing. In particular, Experimental Examples 1 to 6 using only artificial sand as a granular material had a low coefficient of thermal expansion. A small coefficient of thermal expansion means that the fire resistance is high, and even when hot molten metal is poured, vaning defects are unlikely to occur.
On the other hand, in the case of Comparative Example 1 using the kneaded sand in which the hardener was blended with the artificial sand, the fluidity of the kneaded sand was poor and re-coating could not be performed. Therefore, a test piece could not be produced.
In Comparative Example 2 using kneaded sand in which a hardener is blended with natural sand, and Comparative Example 3 in which kneaded sand is blended with a mixed sand of artificial sand and natural sand, X axis, Y axis, Recoating was successfully performed in any direction of the Z axis. However, since the hardened agent is mixed in the kneaded sand in the non-printed part, a regeneration process is necessary for reuse.

10 Metal Case 10a Bottom of Metal Case (Modeling Table)
10b Metal Case Wall 11 Inlet 12 Deaeration Port 13 Print Nozzle Head 13a Discharge Port 20 Laminate 20a Laminate Surface 20b Binder Print Part 20c Binder Non-Print Part 30 Laminate

Claims (12)

  A step (A) of performing a printing operation by laminating a granular material and discharging a binder from the print nozzle head thereon, and a step (B) of passing a gas curing agent through the laminate of the granular material and the binder. A method for manufacturing a three-dimensional layered object.   The step (A) and the step (B) are simultaneously performed in an atmosphere in which the gas curing agent is introduced while degassing, the introduction position of the gas curing agent is below the discharge port of the print nozzle head, and the deaeration position. The method for producing a three-dimensional layered object according to claim 1, wherein is lower than a position where the gas curing agent is introduced.   The method for producing a three-dimensional layered object according to claim 2, wherein the gas curing agent is heavier than air.   The manufacturing method of the three-dimensional layered object as described in any one of Claims 1-3 which hardens | cures further the laminated body by which the gas hardening | curing agent was ventilated.   The method for producing a three-dimensional layered object according to any one of claims 1 to 4, wherein the binder is an acid curable binder and the gas curing agent is an acid gas.   The method for producing a three-dimensional layered object according to claim 5, wherein the acidic gas is carbon dioxide.   The method for producing a three-dimensional layered object according to claim 5 or 6, wherein the acid curable binder is an acid curable resin.   The method for producing a three-dimensional layered object according to claim 5 or 6, wherein the acid curable binder is water glass.   The manufacturing method of the three-dimensional layered object as described in any one of Claims 1-4 whose binder is alkali phenol resin and whose gas hardening | curing agent is organic ester gas.   The manufacturing method of the three-dimensional layered object as described in any one of Claims 1-9 whose granular material is a refractory granular material.   The method for producing a three-dimensional layered object according to claim 10, wherein the refractory granular material is artificial sand obtained by any one of a melting method, a sintering method, and a flame melting method.   The manufacturing method of the three-dimensional layered object according to any one of claims 1 to 11, wherein the three-dimensional layered object is a mold.

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