Patent Publication Number: US-2018050491-A1

Title: Three-dimensional shaping method and additive manufacturing material

Description:
FIELD 
     Embodiments of the present invention relate to a three-dimensional shaping method and an additive manufacturing material. 
     BACKGROUND 
     There are proposed various three-dimensional shaping methods for manufacturing a three-dimensional shaped object by repeating: a powder layer formation process of forming a powder layer on a manufacturing stage; and a binding process of discharging a binder from an inkjet head to a predetermined area on the deposited powder layer to form a cured layer, for example. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: Japanese Patent Application Laid-open No. 2010-208069 
     SUMMARY OF THE INVENTION 
     Problem to be Solved by the Invention 
     To bind powder, it is necessary to use a solution including a certain amount or more of binding components (solid contents). However, to eject a binder from an inkjet head, liquid properties, such as viscosity, have restrictions. In other words, to increase the manufacturing accuracy, it is necessary to reduce the viscosity of the binder material, which makes it difficult to uniformly bind a powder layer. 
     The present invention has been made in view of the disadvantages described above and has an object to provide a three-dimensional shaping method and a material for additive manufacturing that are capable of increasing the density and the strength of a three-dimensional shaped object and providing a homogenous three-dimensional shaped object. 
     Means for Solving Problem 
     A three-dimensional shaping method according to an embodiment manufactures a three-dimensional shaped object and includes repeatedly performing a process of applying, to material particles each coated with a binder, a reaction solution that dissolves therein the binder or causes a binding reaction with the binder and a process of depositing the material particles. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic diagram for explaining the configuration and processes of a three-dimensional manufacturing system according to an embodiment. 
         FIG. 2  is a sectional view schematically illustrating a three-dimensional printer according to the embodiment. 
         FIG. 3  is a perspective view of a main part of a manufacturing tank and a supply device. 
         FIG. 4  is a diagram (part 1) for explaining combinations of a binder BD used for surface coating on secondary particles and a reaction solution RL. 
         FIG. 5  is a diagram (part 2) for explaining combinations of the binder BD used for surface coating on the secondary particles and the reaction solution RL. 
         FIG. 6  is a diagram for explaining a bond between functional groups. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments are described below with reference to the accompanying drawings.  FIG. 1  is a schematic diagram for explaining the configuration and processes of a three-dimensional shaping system according to an embodiment. A three-dimensional shaping system  10  according to the embodiment includes a raw material preparing apparatus  11  that prepares primary particles; a granulating apparatus  12  that mixes the primary particles prepared by the raw material preparing apparatus  11  with a binder BD to produce secondary particles each having a surface coated with the binder; an additive manufacturing apparatus  13  that is a so-called “three-dimensional printer” and deposits the secondary particles to manufacture a three-dimensional shaped object; and a sintering apparatus  14  that heats and sinters the three-dimensional shaped object manufactured by the additive manufacturing apparatus  13  in accordance with a predetermined temperature raising/lowering pattern to provide a sintered object. 
     Used as the raw material preparing apparatus  11  is an apparatus that appropriately adds an auxiliary agent, including the binder BD, to a powdered ceramic raw material (main material) produced be a solid phase method, a liquid phase method, or a gas phase method and performs crushing, dispersion, mixing, and other processing. For example, used as the raw material preparing apparatus  11  is a crushing and mixing apparatus, such as a ball mill, a bead mill, and a jet mill, for example. A spray drier and the like is further used as needed. 
     Next, the granulating apparatus  12  is described. The granulating apparatus  12  performs granulation of receiving injection of the primary particles prepared by the first raw material preparing apparatus  11 - 1  and the second raw material preparing apparatus  11 - 2  at a predetermined ratio and injection of a predetermined binder as an auxiliary agent, to produce the secondary particles. Used as the granulating apparatus is a crushing and mixing apparatus, such as a ball mill, a bead mill, and a jet mill, for example. 
     The following describes a three-dimensional printer serving as the additive manufacturing apparatus  13 .  FIG. 2  is a sectional view schematically illustrating the three-dimensional printer according to the embodiment. A three-dimensional printer  13  is a three-dimensional shaping apparatus employing a powder fixing depositing method. As illustrated in  FIG. 2 , the three-dimensional printer  13  includes a processing chamber  21 ; a material tank  22  that accommodates raw materials (secondary particles) for producing a three-dimensional shaped object; a manufacturing tank  23  that actually performs three-dimensional shaping; a wiper device  24  that supplies the raw materials accommodated in the material tank  22  to the manufacturing tank  23 ; an inkjet shaping device  25  that ejects a reaction solution RL to the raw materials (secondary particles) in units of layers supplied by the wiper device  24  to the manufacturing tank  23  at a position (in a pattern) corresponding to the three-dimensional shaped object on each layer corresponding to slice data; and a control unit  26  that controls the material tank  22 , the manufacturing tank  23 , the wiper device  24 , and the inkjet shaping device  25 . 
     In the configuration described above, the processing chamber  21  has a sealed space inside thereof. The material tank  22 , the manufacturing tank  23 , the wiper device  24 , and the inkjet shaping device  25  are arranged at predetermined positions in the processing chamber  21 . The inside of the processing chamber  21  is supplied with an inert gas, such as nitrogen and argon, from a gas supply device, which is not illustrated, through a supply port  21 A to keep the inside of the processing chamber clean. Unnecessary gas components or the like generated in three-dimensional shaping are exhausted to the outside of the processing chamber  21  through an exhaust port  21 B. 
     The material tank  22  has a placing table  22 A inside thereof in a manner capable of vertically moving by a hydraulic lifting device  22 B. Secondary particles P 20  serving as the raw materials are placed on the placing table  22 A. In three-dimensional shaping, the placing table moves upward at each predetermined shaping step, thereby moving the raw materials of an amount corresponding to a predetermined layer thickness toward an upper part of the material tank  22 . 
     The manufacturing tank  23  includes a placing table  23 A, a hydraulic lifting device  23 B, and a peripheral wall  23 D. The secondary particles P 20  serving as the materials are sequentially supplied to the upper face of the placing table  23 A based on slice data. 
     The wiper device  24  includes a squeezing blade. The wiper device  24  is horizontally driven in  FIG. 2 , thereby supplying, to the manufacturing tank  23 , the raw materials of the amount corresponding to the predetermined layer thickness moved toward the upper part of the material tank  22  while leveling them such that they have a uniform thickness. 
     The inkjet shaping device  25  ejects the reaction solution RL that dissolves a binding layer on the surface of the secondary particles P 20  supplied to the manufacturing tank  23  or causes a bonding reaction or the like, thereby causing the secondary particles P 20  to bind with each other. The inkjet shaping device  25  thus deposits and fixes the secondary particles P 20 . The inkjet shaping device  25  includes an ejecting device  61  that ejects the reaction solution RL to the secondary particles P 20  supplied to the manufacturing tank  23 ; a moving device  62  that moves the ejecting device  61 ; an accommodating device  63  that accommodates the raw materials, and a collecting device  64  that collects the raw materials (secondary particles) that are not used for shaping. 
       FIG. 3  is a perspective view of a main part of the manufacturing tank and the supply device. As illustrated in  FIG. 3 , the ejecting device  61  of the inkjet shaping device  25  includes a holder  71 ; a plurality of nozzles  72 A to  72 E that are provided integrally with the holder  71 ; and a plurality of tanks  73 A to  73 E respectively corresponding to the nozzles  72 A to  72 E. 
     The holder  71  holds the tanks  73 A to  73 E and is provided with the nozzles  72 A to  72 E on the lower face in a manner corresponding to the tanks  73 A to  73 E, respectively. 
     In the configuration described above, the tanks  73 A to  73 E may store therein the same reaction solution RL or store therein a plurality of different types of undiluted reaction solutions RL 0  mixed to function as the reaction solution RL, for example. 
     To simplify the explanation below, the following describes a case where the tanks  73 A to  73 E store therein the same reaction solution RL, for example. 
     The moving device  72  includes a rail  81  and a pair of conveyers  82 . The moving device  72  moves the ejecting device  61  in directions along an X-axis and a Y-axis, thereby moving the tanks  73 A to  73 E integrated with the holder  71  of the ejecting device  61  with respect to the manufacturing tank  23 . 
     The rail  81  is arranged above the manufacturing tank  23  and is longer than the size of the manufacturing tank in the direction along the Y-axis. The holder  71  of the ejecting device  61  can be moved along the rail  81 . By driving a mechanism including various parts, such as a motor, a gear, and a belt, the ejecting device  61  is moved along the rail  81 . The nozzles  72 A to  72 E of the ejecting device  61  are also moved along the rail  81  and eject the reaction solution RL, thereby depositing the secondary particles P 20  in the manufacturing tank  23 . 
     The collecting device  64  is connected to the accommodating device  63  by a collection tube  66 . The collecting device  64  sucks up the powdery secondary particles P 20  that are not fixed and transmits and collects them in the accommodating device  63 . 
     In the configuration described above, the control unit  26  controls the manufacturing tank  23 , the wiper device  24 , and the inkjet shaping device  25  to cause the secondary particles each coated with the fixing agent to fix to each other, thereby additively manufacturing a three-dimensional shaped object MD. Furthermore, the control unit  26  controls the collecting device  64  so as to suck up the powdery secondary particles P 20  that are not used for the manufacturing and transmit and collect them in the accommodating device  63 . 
     The three-dimensional shaped object MD manufactured as described above is subjected to heating by the sintering apparatus  14  in accordance with a predetermined temperature raising pattern and a predetermined temperature lowering pattern. The three-dimensional shaped object MD is thus sintered and formed into a three-dimensional shaped object MD 2  serving as a sintered object. More specifically, the three-dimensional shaped object serving as a sintered object has a length reduced to substantially 70%. The size of the three-dimensional shaped object is substantially 50% to 60% the size of the three-dimensional shaped object MD by volume. 
     The following describes preferable combinations of surface coating on the secondary particles with the binder BD and the reaction solution RL in detail. The outline is described first. The following five combinations are given as examples of the combination of the binder BD used for surface coating on the secondary particles and the reaction solution RL. 
     (1) Binder BD: Organic coating material (e.g., acrylic) 
     Reaction solution RL: solvent 
     (2) Binder BD: inorganic coating material (e.g., SiO 2 , Al 2 O 3 , and TiO 2 ) 
     Reaction solution RL: solution of inorganic nanoparticles (e.g., the same material as the binder BD or colloidal silica) 
     (3) Binder BD: inorganic coating material (e.g., SiO 2 , Al 2 O 3 , and TiO 2 ) 
     Reaction Solution RL: organic silane solution or the like 
     (4) Binder BD: metallic coating material 
     Reaction solution RL: silane coupling agent (e.g., a thiol group) 
     (5) Binder BD: silane coupling agent (e.g., an amino group) 
     Reaction solution RL: silane coupling agent (e.g., a carboxyl group) 
     The following describes the combinations of the binder BD and the reaction solution RL in greater detail.  FIG. 4  is a diagram (part 1) for explaining the combinations of the binder BD used for surface coating on the secondary particles and the reaction solution RL. 
     [1] Organic Coating Material+Solvent 
     The following describes a case where an organic coating material is used as the binder BD and a solvent is used as the reaction solution RL. As described in the first section in  FIG. 4 , examples of the binder BD made of an organic coating material include, but are not limited to, PVDF (polyvinylidene difluoride), PVB (polyvinyl butyral), polyester, PVC (polyvinyl chloride), acrylic, polyurethane, polypropylene, polyethylene, epoxy, EVA (ethyl vinyl acetate), polyamide, PVA (polyvinyl alcohol), rosin, fluorine, FEVE (fluoro ethylene vinyl ether), phenol, SBR (styrene-butadiene rubber), HPMC (hydroxypropyl methylcellulose, wax, etc. The organic coating material is appropriately selected from the group described above. As the reaction solution RL, a fluid (e.g., an organic solvent and water) that dissolves the organic coating material is used. In this case, the method for causing the secondary particles P 20  to bind with each other is a mechanism in that the secondary particles P 20  bind with each other by re-curing of the coating material after dissolution. The binding principle is assumed to be physical interference caused by solidification of a resin. Examples of additives to the reaction solution RL (referred to as an IJ liquid in  FIG. 4 ) applied by the inkjet shaping device  25  include, but are not limited to, a viscosity adjusting agent that provides optimum viscosity, a surface active agent that improves the wettability, etc. 
     [2] Inorganic Coating Material+Inorganic Nanoparticle Solution 
     The following describes a case where an inorganic coating material is used as the binder BD and a solution of inorganic nanoparticles is used as the reaction solution RL. 
     As described in the second section in  FIG. 4 , examples of the binder BD made of an inorganic coating material include, but are not limited to, SiO 2  (silicon dioxide), Al 2 O 3  (aluminum trioxide), TiO 2  (titanium dioxide), Au (gold,), Cu (copper), Ag (silver), etc. The inorganic coating material is appropriately selected from the group described above. 
     A solution of nanoparticles made of the same material as the material of the inorganic coating material or a solution of colloidal silica is used as the reaction solution RL. In this case, the method for causing the secondary particles P 20  to bind with each other is a mechanism in that the secondary particles P 20  bind with each other by intermolecular force and electrostatic force. The binding principle is assumed to be electrostatic attraction (Coulomb&#39;s force). 
     Examples of additives to the reaction solution RL (referred to as the IJ liquid in  FIG. 4 ) applied by the inkjet shaping device  25  include, but are not limited to, a viscosity adjusting agent that provides optimum viscosity, a surface active agent that improves the wettability, a dispersing agent that uniformly disperses the nanoparticles in the solution, etc. 
       FIG. 5  is a diagram (part 2) for explaining the combinations of the binder BD used for surface coating on the secondary particles and the reaction solution RL. 
     [3] Inorganic Coating Material+Organic Silane Solution 
     The following describes a case where an inorganic coating material is used as the binder BD and an organic silane solution is used as the reaction solution RL. 
     As described in the third section in  FIG. 5 , examples of the binder BD made of an inorganic coating material include, but are not limited to, SiO 2  (silicon dioxide), Al 2 O 3  (aluminum trioxide), TiO 2  (titanium dioxide), etc. The inorganic coating material is appropriately selected from the group described above. A silane coupling agent is used as the reaction solution RL. 
     In this case, the method for causing the secondary particles P 20  to bind with each other is a mechanism in that the secondary particles P 20  bind with each other by bonding force of a hydrolysable group (e.g., an alkoxy group) compatible with (having an affinity for) an inorganic substance. The binding principle is assumed to be that the hydrolysable group reacts and bonds with glass, a metal, or the like. 
     Examples of additives to the reaction solution RL (referred to as the IJ liquid in  FIG. 5 ) applied by the inkjet shaping device  25  include, but are not limited to, a viscosity adjusting agent that provides optimum viscosity, a surface active agent that improves the wettability, etc. 
     [4] Metallic Coating Material+Silane Coupling Agent 
     The following describes a case where a metallic coating material is used as the binder BD and a silane coupling agent is used as the reaction solution RL. As described in the fourth section in  FIG. 5 , examples of the binder BD made of a metallic coating material include, but are not limited to, Au (gold), Cu (copper), Ag (silver), etc. The metallic coating material is appropriately selected from the group described above. 
     A silane coupling agent is used as the reaction solution RL. In this case, the method for causing the secondary particles P 20  to bind with each other is a mechanism in that the secondary particles P 20  bind with each other by intermolecular force and electrostatic force. 
     The binding principle is a mechanism in that the secondary particles P 20  bind with each other by bonding force of a functional group (e.g., a thiol group [=a sulphydryl group, a mercapto group, or a sulfhydryl group]) compatible with (having an affinity for) a metal. 
     Examples of additives to the reaction solution RL (referred to as the IJ liquid in  FIG. 4 ) applied by the inkjet shaping device  25  include, but are not limited to, a viscosity adjusting agent that provides optimum viscosity, a surface active agent that improves the wettability, etc. 
     [5] Silane Coupling Agent+Silane Coupling Agent 
     The following describes a case where a silane coupling agent is used as both of the binder BD and the reaction solution RL. As described in the fifth section in  FIG. 5 , a silane coupling agent is used as the binder BD, and a silane coupling agent is used as the reaction solution RL. 
     In this case, the method for causing the secondary particles P 20  to bind with each other is a mechanism in that the secondary particles P 20  bind with each other by bonding force of a bond (e.g., a peptide bond, an ester bond, an amide bond, and a disulfide bond) between functional groups (e.g., amino group+carboxyl group) likely to react (having high reactivity). 
       FIG. 6  is a diagram for explaining a bond between functional groups. As illustrated in  FIG. 6 , if a silane coupling agent having a carboxyl group (—COOH) is used as the binder BD and a silane coupling agent having an amino group (—NH 2 ) is used the reaction solution RL, a peptide bond is generated by a dehydration reaction (OH+H→H 2 O), thereby providing a strong bond. 
     The binding principle is a mechanism in that the secondary particles P 20  bind with each other by electrostatic bonding force between the functional groups. Examples of additives to the reaction solution RL (referred to as the IJ liquid in  FIG. 4 ) applied by the inkjet shaping device  25  include, but are not limited to, a viscosity adjusting agent that provides optimum viscosity, a surface active agent that improves the wettability, etc. 
     As described above, the reaction solution RL that makes the binder BD for causing the secondary particles P 20  to bind with each other into a bindable state according to the present embodiment include no solid contents. This structure facilitates adjustment of the liquid viscosity. As a result, the inkjet shaping device  25  can reliably and uniformly apply the reaction solution RL to the coating layer of the secondary particles P 20 , thereby uniformly binding a powder layer serving as an aggregate of the secondary particles P 20 . Consequently, the present embodiment can reduce manufacturing failure and provide a uniform three-dimensional shaped object having high strength and accuracy. 
     While certain embodiments of the present invention have been described, these embodiments are given by way of example only and are not intended to limit the scope of the invention. The novel embodiments may be embodied in a variety of other forms, and various omissions, substitutions, and changes may be made without departing from the spirit of the invention. The embodiments and the modifications thereof are included in the scope and the spirit of the invention and in the invention described in the claims and their equivalents. 
     While the embodiments above perform three-dimensional manufacturing using one type of secondary particles, they may perform three-dimensional manufacturing similarly, using a plurality of types of secondary particles, for example.