Patent Publication Number: US-2016221261-A1

Title: Three-Dimensional Shaping Device and Three-Dimensional Shaping Method

Description:
TECHNICAL FIELD 
     The present invention relates to a three-dimensional shaping apparatus and a three-dimensional shaping method. 
     BACKGROUND ART 
     A technique called rapid prototyping (RP) is known as a technique of shaping a three-dimensional article (hereinafter referred to as “three-dimensional object”). This technique is a technique of shaping a three-dimensional object by using data (data of STL (Standard Triangulated Language) format) describing the surface of one three-dimensional object as a collection of triangles, by calculating a cross-sectional shape thinly cut in the lamination direction, and by forming each layer in accordance with the shape. In addition, known examples of methods of shaping a three-dimensional object include fused deposition molding (FDM), ink-jet methods, ink-jet binder methods, stereo lithography (SL), selective laser sintering (SLS) and the like. 
     An example of the three-dimensional shaping method of the ink-jet method is a technique of shaping a three-dimensional object in which one shaping material layer (cured layer) is formed through a step of selectively discharging a shaping material (for example, photosetting resin) from an ink-jet head to a shaping stage, a step of flattening the surface, and a step of curing the shaping material (in the case of a photosetting resin, light irradiation step), and a plurality of the shaping material layers are stacked on one another to thereby shaping a three-dimensional object, for example. With this method, high-definition shaping material layers are formed by discharging a shaping material in the form of micro droplets, and thus a high-definition three-dimensional object can be shaped by stacking the high-definition shaping material layers on one another. In addition, an ink-jet head (so-called line head) in which a plurality of discharging nozzles are arranged is used as the ink-jet head so that even a large three-dimensional object can be shaped in a relatively short time. 
     In recent years, it is desired to shape a three-dimensional object with a high definition, or more specifically, with a resolution of 600 [dpi] (600 [dot] per inch at approximately 42 [μm] pitch) or greater. High-resolution of a three-dimensional object in the lamination direction can be achieved by reducing the lowering amount of the shaping stage or the lifting amount of the ink-jet head (sending pitch). In addition, high-resolution of the main scanning direction (a direction orthogonal to the direction in which discharging nozzles are arranged) can be achieved by increasing the frequency of the voltage (discharging frequency) to be applied to the ink-jet head, or by reducing the scanning speed of the shaping stage and the ink-jet head. 
     In addition, high-resolution in the sub scanning direction (a direction parallel to the direction in which discharging nozzles are arranged) can be achieved by increasing the nozzle resolution of the ink-jet head, that is, by reducing the nozzle pitch. However, increase of the nozzle resolution of the ink-jet head is limited, and currently used nozzle resolution is merely about 100 [dpi] (100 nozzles per inch at approximately 0.25 [mm] pitch). In view of this, conventionally, after a first operation of discharging the shaping material while scanning in the main scanning direction, a second operation in which scanning is performed in the sub scanning direction at a pitch equal to or smaller than the nozzle pitch such that the discharging centers of the shaping material do not overlap is performed (that is, the discharging position is shifted to a position between nozzles), and the first operation and the second operation are repeated to increase the resolution in the sub scanning direction. 
     PTL 1 discloses a technique in which the arranging direction of orifices (discharging nozzles) in a print head (ink-jet head) and the scanning direction of the print head are oriented at a certain angle such that the shaping material can be discharged at an interval smaller than a nozzle pitch. 
     CITATION LIST 
     Patent Literature 
     PTL 1 
     Japanese Patent Application Laid-Open No. 2004-130817 
     SUMMARY OF INVENTION 
     Technical Problem 
     However, the above-mentioned approach intended for increasing the resolution of a three-dimensional object may result in decrease in shaping speed of the three-dimensional object. For example, when increasing the resolution in the sub scanning direction by repeating the first operation and the second operation, the discharging frequency of the shaping material is required to be increased, and consequently the shaping speed of the three-dimensional object is reduced by the increased frequency. 
     An object of the present invention is to provide a three-dimensional shaping apparatus and a three-dimensional shaping method which can increase the resolution of a three-dimensional object without reducing the shaping speed of the three-dimensional object. 
     Solution to Problem 
     A three-dimensional shaping apparatus according to the present invention includes: a shaping stage on which a shaping material layer made of a shaping material is formed; a first formation section including a first discharging nozzle configured to discharge the shaping material, the first formation section being configured to discharge the shaping material from the first discharging nozzle toward the shaping stage to form an outline of the shaping material layer with a first resolution; and a second formation section configured to supply the shaping material to the shaping stage to form an inner portion of the outline with a second resolution lower than the first resolution, in which the shaping material is supplied from the first formation section and the second formation section onto the shaping stage, and a plurality of shaping material layers are formed and stacked on one another to shape a three-dimensional object. 
     A three-dimensional shaping method of shaping a three-dimensional object according to the present invention includes: forming an outline of a shaping material layer with a first resolution by discharging a shaping material toward a shaping stage; forming an inner portion of the outline with a second resolution lower than the first resolution by supplying the shaping material toward the shaping stage; and forming and stacking a plurality of shaping material layers on one another. 
     Advantageous Effects of Invention 
     According to the present invention, an outline of a shaping material layer which is related to the appearance of a three-dimensional object and is therefore required to be formed with a high resolution is formed with a resolution higher than the resolution of the inner portion of the outline, whereas the inner portion of the outline which is not related to the appearance and is therefore is not required to be formed with a high resolution is formed with a formation speed higher than that of the outline. Thus, the resolution of the shaping material layer can be increased without reducing the formation speed of the shaping material layer, and in turn, the resolution of the three-dimensional object can be increased without reducing the shaping speed of the three-dimensional object. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  schematically illustrates a configuration of a three-dimensional shaping apparatus according to a first embodiment; 
         FIG. 2  illustrates a principal part of a control system of the three-dimensional shaping apparatus according to the first embodiment; 
         FIGS. 3A to 3C  illustrate a configuration of a first formation section according to the first embodiment, and specifically,  FIG. 3A  is a side view of an interior of a housing,  FIG. 3B  is a bottom view, and  FIG. 3C  illustrates a case where the first formation section has a double structure of a part for a model material and a part for a supporting material; 
         FIGS. 4A to 4C  illustrate a configuration of a second formation section according to the first embodiment, and specifically,  FIG. 4A  is a side view of an interior of a housing,  FIG. 4B  is a bottom view, and  FIG. 4C  illustrates a case where the second formation section has a double structure of a part for a model material and a part for a supporting material; 
         FIG. 5  illustrates a configuration of a curing section according to the first embodiment; 
         FIGS. 6A to 6J  schematically illustrate an operation of forming one shaping material layer; 
         FIG. 7  schematically illustrates a configuration of a three-dimensional shaping apparatus according to a second embodiment; 
         FIGS. 8A to 8C  illustrate a configuration of a second formation section according to the second embodiment, and specifically,  FIG. 8A  is a side view of an interior of a housing,  FIG. 8B  is a bottom view, and  FIG. 8C  illustrates a case where the second formation section has a double structure of a part for a model material and a part for a supporting material; 
         FIGS. 9A to 9D  illustrate an operation of the second formation section according to the second embodiment; 
         FIG. 10  illustrates a configuration of the second formation section according to a third embodiment; 
         FIGS. 11A to 11C  illustrate an operation of the second formation section according to the third embodiment; 
         FIG. 12  shows temperature dependency of the viscosity of a shaping material having a sol-gel phase transition temperature; and 
         FIG. 13  illustrates a configuration of a heating section that heats a discharging head. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     In the following, a first embodiment will be described in detail with reference to the accompanying drawings. 
       FIG. 1  schematically illustrates a configuration of three-dimensional shaping apparatus  100  according to the first embodiment.  FIG. 2  illustrates a principal part of a control system of three-dimensional shaping apparatus  100  according to the first embodiment. Three-dimensional shaping apparatus  100  illustrated in  FIGS. 1 and 2  shapes three-dimensional object  200  by sequentially stacking shaping material layers made of a first shaping material (also referred to as “model material”) on shaping stage  140 . When the shaping object has an overhung portion (overhanging portion) for example, a second shaping material (also referred to as “supporting material”) is disposed in contact with the model material on the outside of the model material and the shaping material layers are sequentially stacked, to thereby support the overhung portion of the model material and cover the model material until the shaping of three-dimensional object  200  is completed. Here, an exemplary case where a photosetting resin is used as the shaping material will be described. The supporting material is removed by the user after the shaping of three-dimensional object  200  is completed. It is to be noted that the portion corresponding to the supporting material is illustrated with a broken line in  FIG. 1  for convenience of description. 
     Three-dimensional shaping apparatus  100  includes control section  110 , shaping-material layer formation section  120 , movement mechanism  130 , shaping stage  140 , display section  145  and data input section  150 . Three-dimensional shaping apparatus  100  is connected with computer apparatus  155 . 
     Data input section  150  acquires 3D data (such as CAD data and design data) of a shaping object from computer apparatus  155 , and outputs the data to control section  110 . Computer apparatus  155  is configured to design the shaping object, or generate shaping data based on three-dimensional information obtained through measurement of a real object using a three-dimensional measuring apparatus. The CAD data and the design data may include color image information of a part of the surface of the shaping object or the entire surface of the shaping object and color image information of the interior of the shaping object, as well as the shape of the shaping object. It is to be noted that the method for acquiring 3D data is not particularly limited. 3D data may be acquired through short-range radio communication such as wired communication, radio communication, and Bluetooth (registered trademark), or may be acquired from a recording medium such as a universal serial bus (USB) memory. In addition, the 3D data may be acquired from a server that manages and stores the 3D data, or the like. 
     Control section  110  includes a computing section such as a central processing unit (CPU) or the like, and reconstructs data of each shaping material layer (hereinafter referred to as “slice data”) for shaping a three-dimensional object on the basis of 3D data output from data input section  150 . In addition, during the shaping operation of three-dimensional object  200 , control section  110  controls the entire operation of three-dimensional shaping apparatus  100 . For example, control section  110  outputs to movement mechanism  130  mechanism control information for discharging the shaping material to a desired place, and outputs the slice data to shaping-material layer formation section  120 . That is, control section  110  synchronizes and controls shaping-material layer formation section  120  and movement mechanism  130 . 
     Display section  145  displays various information and messages which are required to be received by the user. 
     Shaping-material layer formation section  120  includes first formation section  122  and second formation section  124 . Second formation section  124  includes discharging section  124 A and curing section  124 B as illustrated in  FIG. 1 . First formation section  122  and discharging section  124 A respectively include casings  123  and  125  that operate as carriages which freely move in x-direction and y-direction orthogonal to each other in a horizontal plane. Curing section  124 B includes casing  126  that operates as a carriage which moves in y-direction. 
     Shaping stage  140  is disposed below shaping-material layer formation section  120 . On shaping stage  140 , shaping material layers are formed and stacked by shaping-material layer formation section  120  so as to shape three-dimensional object  200 . 
     As illustrated in  FIG. 3 , first formation section  122  includes ink-jet discharging head  160  and light irradiation device  162  which are disposed in casing  123 . Discharging head  160  includes discharging nozzle (first discharging nozzle)  161  that selectively discharges droplet  170  of the shaping material. In the present embodiment, clogging detection section  164  that detects clogging (that is, a situation where droplet  170  is not discharged from the discharging nozzle, or discharging is insufficient because of foreign matters adhering to the inside of the nozzle and the like) is provided in the proximity of an end portion of discharging nozzle  161 . Clogging detection section  164  includes cylindrical electrode  164   a  that charges droplet  170   d  discharged from the discharging nozzle, and cylindrical dielectric electrode  164   b  through which charged droplet  170  passes. On the basis of results of measurement of an induced current which is generated at the time when charged droplet  170  passes through cylindrical dielectric electrode  164   b , control section  110  detects clogging of the discharging nozzle (see, for example, Japanese Patent Application Laid-Open No. 59-120464). It is to be noted that the method of detecting clogging of the discharging nozzle disclosed in Japanese Patent Application Laid-Open No. 2005-35309 for example may be employed in which clogging of the discharging nozzle is detected by generating a light beam in a direction interesting with the discharging direction of the droplet and by checking whether discharged droplet has blocked the light beam. When a detection step of detecting clogging of discharging nozzle  161  prior to three-dimensional shaping is provided, wasteful consumption of the shaping material due to formation of insufficient shaping articles can be prevented. 
     Discharging head  160  discharges droplet  170  of the shaping material from the discharging nozzle toward shaping stage  140  while moving in x-direction and y-direction orthogonal to each other in a horizontal plane along an outline portion which is formed when a shaping material layer is formed. Here, the outline is a shape which can be visually recognized when a shaped three-dimensional object  200  is viewed from outside. In the above-mentioned manner, the outline of the shaping material layer is formed in a desired region on shaping stage  140 . It is to be noted that discharging head  160  may discharge droplet  170  while moving around the outline of the shaping material layer one time, or may discharge droplet  170  while moving around the outline of the shaping material layer multiple times. 
     In the present embodiment, the nozzle diameter of discharging nozzle  161  of discharging head  160  is set to a small value to form the outline of the shaping material layer with a resolution higher than that of the inner portion of the outline (the region enclosed by the outline). Here, in the present example, the resolution is represented by the number of droplets which can be provided in a unit distance. Since the outline of the shaping material layer can be formed into a shape with a small number of (for example, one or several) droplets  170 , the number of discharging nozzles  161  of discharging head  160  can be reduced. Therefore, even when discharging head  160  is provided with clogging detection sections  164  corresponding to the number of discharging nozzles  161 , it is possible to suppress the cost and the device size of first formation section  122  to the minimum. Accordingly, even when clogging of the discharging nozzle is facilitated due to a decreased nozzle diameter of discharging nozzle  161 , the clogging can be surely detected with clogging detection sections  164 , and it is possible to take measures such as self-cleaning of the nozzle and notification to the user with a message on display section  145  indicating the occurrence of nozzle clogging. 
     Discharging head  160  stores the shaping material such that the shaping material is dischargeable. In the present embodiment, as discharging head  160 , a discharging head which can discharge a shaping material having a viscosity of 5 to 15 [mP·s] is employed. As the shaping material, a photosetting material which is curable with irradiation of light having a specific wavelength is used. Examples of the photosetting material include ultraviolet curable resins, and it is possible to use radical polymerized ultraviolet curable resins such as acrylic acid ester and vinyl ether; and cation polymerized ultraviolet curable resins using a combination of an epoxy monomer, an epoxy oligomer, an oxetane monomer, an oxetane oligomer and the like, and acetophenone, benzophenone and the like as a reaction initiator according to the resin. The photosetting material can be stored in a dischargeable state by using a light blocking member, a filter and the like to block light having a specific wavelength capable of facilitating the curing. The shaping material is discharged onto shaping stage  140  from discharging head  160 , thereby forming a shaping material layer. The shaping material layer is semi-cured by a curing process with light irradiation. Here, a semi-cured state is a state where the shaping material layer has been cured such that the layer has a viscosity enough to maintain the shape of the layer. From the viewpoint of sufficiently ensuring the adhesion property to the subsequently formed shaping material layer, it is preferable to keep a semi-cured state without completing the photopolymerization reaction at the time of curing of each shaping material layer such that the photopolymerization reaction is caused between the shaping material layer and the subsequently formed shaping material layer at the time of curing the subsequently formed shaping material layer. 
     In the case where the shaping object has an overhung portion (overhanging portion), or the case where the surface of three-dimensional object  200  is covered with another material for the purpose of protecting three-dimensional object  200 , it is preferable to further provide a discharging head for discharging supporting material. For example, as illustrated in  FIG. 3C , it is possible to employ a configuration in which a second discharging head and a second light irradiation device are provided in casing  123  of first formation section  122 . In this case, discharging of a shaping material as a model material from the first discharging head and discharging of the shaping material as the supporting material from the second discharging head may be simultaneously performed, or the supporting material may be discharged from the second discharging head after discharging the model material corresponding to one layer from the first discharging head such that the supporting material is in contact with the discharged model material, or, the model material may be discharged from the first discharging head after discharging the supporting material corresponding to one layer from the second discharging head such that the model material is in contact with the discharged supporting material. 
     Light irradiation device  162  irradiates a droplet of the photosetting resin discharged to shaping stage  140  with light from light irradiation port  163  to perform a curing process (light irradiation process) and semi-cures the droplet. When the shaping material is an ultraviolet curing material, an UV laser irradiation device that emits an ultraviolet (UV) laser beam is used as light irradiation device  162 . In the present embodiment, at a timing when droplet  170  of the shaping material discharged from discharging head  160  reaches shaping surface  172 , control section  110  controls light irradiation device  162  to irradiate droplet  170  reaching shaping surface  172  with light (dotted arrow in  FIG. 3 ). To be more specific, the dropping time of droplet  170  is measured in advance, and, on the basis of the estimated time period from the discharging of the shaping material to impinging on shaping surface  172 , droplet  170  is irradiated with light simultaneously with the impinging or immediately after the impinging. Alternatively, the installation angle of light irradiation device  162  is adjusted such that a laser beam emitted from light irradiation port  163  reaches the impinging area of droplet  170  on shaping surface  172 , and light is continuously emitted so as to include the timing at which droplet  170  reaches shaping surface  172 . Here, shaping surface  172  is the surface of shaping stage  140  in the case where a first layer of the shaping material layers is formed, and is the surface of the Nth shaping material layer in the case where the N+1th shaping material layer is formed. By irradiating droplet  170  reaching shaping surface  172  with light at the timing when droplet  170  reaches shaping surface  172 , droplet  170  can be cured before wet spreading of droplet  170  is caused on shaping surface  172 , and thus the outline of the shaping material layer can be formed with high resolution. It is to be noted that light irradiation device  162  may emit the light only at the timing when droplet  170  discharged from discharging head  160  reaches shaping surface  172 , or may continuously emit the light so as to include the timing when droplet  170  reaches shaping surface  172 . 
     As illustrated in  FIG. 4 , discharging section  124 A includes discharging device  180  that discharges shaping material  182  toward shaping surface  172  from discharging nozzle  181 . Discharging device  180  is provided in casing  125 . In the present embodiment, discharging device  180  is a dispenser capable of controlling the discharging rate of shaping material  182 , and can control the discharging and stopping of shaping material  182 . Discharging device  180  includes a discharging nozzle (second discharging nozzle) capable of continuously discharging shaping material  182 . After first formation section  122  has started an operation of forming an outline of a shaping material layer, discharging device  180  discharges shaping material  182  to fill the inner portion of the outline and forms the inner portion under the control of control section  110 . With this configuration, when discharging device  180  discharges shaping material  182 , the outline of the shaping material layer formed by first formation section  122  serves as a wall, and it is thus possible to prevent shaping material  182  from leaking out of the outline. The discharging rate of shaping material  182  of discharging device  180  is set by obtaining the volume of the internal portion of the outline by multiplying the planar dimension of the inner portion of the outline of the shaping material layer formed by first formation section  122  and the height of the outline (that is, the thickness of one layer of the shaping material layer). In the present embodiment, the discharging rate of shaping material  182  is set to a value greater than the volume obtained by multiplying the planar dimension of the inner portion of the outline and the height of the outline to a degree that shaping material  182  does not leak from the wall of the outline. It is to be noted that, in the present embodiment, shaping material  182  is supplied so as to fill the inner portion of the outline, and therefore the inner portion of the outline can be considered to have no resolving property. Thus, naturally, first formation section  122  forms the outline with a resolution higher than that of second formation section  124 , and second formation section  124  forms the inner portion of the outline with a resolution lower than that of first formation section  122 . 
     It suffices that discharging device  180  discharges shaping material  182  so as to fill the inner portion of the outline of the shaping material layer (that is, high resolution is not required for formation of the inner portion of the outline), and therefore the nozzle diameter of discharging nozzle  181  of discharging device  180  is greater than that of discharging nozzle  161  of discharging head  160 . With this configuration, clogging of discharging nozzle  181  of discharging device  180  can be prevented. In addition, discharging device  180  can discharge a droplet having a size greater than that of the droplet discharged from discharging head  160 . That is, discharging device  180  performs shaping with a resolution lower than that of discharging head  160  and thus can form the inner portion of the outline of the shaping material layer with a speed higher than the formation speed of discharging head  160 . That is, discharging device  180  can complete the application of shaping material  182  to an area in a shorter time in comparison with discharging head  160 . 
     While the shaping material used by discharging device  180  may be the same as the shaping material used by discharging head  160 , it is also possible to use different shaping materials having different viscosities or the like in accordance with light irradiation device  194  for the light irradiation process. In addition, it is possible to change the light polymerization initiator used for the shaping material used in discharging device  180  in accordance with light irradiation device  194 . 
     While, in the case where the supporting material is required, the shaping material as the supporting material may be discharged from the above-described second discharging nozzle, it is also possible to employ a configuration in which a second discharging device having a discharging port having a large diameter as with discharging device (first discharging device)  180  is provided at discharging section  124 A of second formation section  124  for the purpose of avoiding decrease of the shaping speed as illustrated in  FIG. 4C . In this case, the supporting material may be discharged from the second discharging device such that the supporting material is in contact with the discharged model material after discharging of the model material for one layer from first discharging device  180  is completed, or the model material may be discharged from the first discharging device such that the model material is in contact with the discharged supporting material after discharging of the supporting material for one layer from the second discharging device is completed. 
     As illustrated in  FIG. 5 , curing section  124 B includes, in casing  126 , levelling roller  190  as a planarizing section that levels shaping material  182 , scraping member  192 , collecting member  193  for scraped shaping material  182  and light irradiation device  194  as a curing section that cures shaping material  182 . Levelling roller  190 , scraping member  192  and light irradiation device  194  are disposed in curing section  124 B in this order from the near side in  FIG. 1 . 
     Levelling roller  190  can be driven into rotation under the control of control section  110 , and levelling roller  190  makes contact with the surface of shaping material  182  discharged by discharging device  180  to planarize the surface of shaping material  182 . Consequently, a shaping material layer (the outline and the inner portion of the outline) having a uniform thickness is formed. As a result of planarization of the surface of the shaping material layer, the next shaping material layer can be precisely formed and stacked, and thus highly precise three-dimensional object  200  can be shaped. It is to be noted that the leveling member for planarizing the surface of shaping material  182  is not limited to levelling roller  190 , and a blade or the like may be used for example. 
     Scraping member  192  is a blade provided in the proximity of levelling roller  190 . Scraping member  192  scrapes the shaping material attached on the surface of levelling roller  190 . Shaping material  182  scraped by scraping member  192  may be supplied to discharging head  160  (first formation section  122 ) and discharging device  180  (discharging section  124 A) and reused, or may be sent to a waste tank. 
     Light irradiation device  194  performs a curing process (light irradiation process) on shaping material  182  composed of a photosetting resin discharged by discharging device  180 , and semi-cures shaping material  182 . When the shaping material is an ultraviolet curing material, a UV lamp (in the present embodiment, a high-pressure mercury lamp) that emits an ultraviolet ray (UV) is used as light irradiation device  194 . It is to be noted that instead of a high-pressure mercury lamp, a low-pressure mercury lamp, an intermediate pressure mercury lamp, an ultra-high pressure mercury lamp, a carbon-arc lamp, a metal halide lamp, a xenon lamp, an ultraviolet LED lamp or the like may be used as light irradiation device  194 . 
     Movement mechanism  130  three-dimensionally changes the relative position of first formation section  122  and discharging section  124 A, and shaping stage  140 . In addition, movement mechanism  130  two-dimensionally changes the relative position of curing section  124 B and shaping stage  140 . To be more specific, movement mechanism  130  includes x-direction guide  132  that is engaged with first formation section  122  and discharging section  124 A, y-direction guide  134  that guides x-direction guide  132  and curing section  124 B in y-direction, and z-direction guide  136  that guides shaping stage  140  in z-direction which is a vertical direction as illustrated in  FIG. 1 . Further, movement mechanism  130  includes a drive mechanism composed of a motor, a drive reel and the like which are not illustrated. 
     Movement mechanism  130  drives a motor and a drive mechanism not illustrated in accordance with mechanism control information output from control section  110 , and freely moves first formation section  122  and discharging section  124 A in x-direction and y-direction (see  FIG. 1 ). It is to be noted that movement mechanism  130  may have a configuration in which the positions of first formation section  122  and discharging section  124 A are fixed and shaping stage  140  is moved in x-direction and y-direction, or a configuration in which first formation section  122  and discharging section  124 A, and shaping stage  140  are moved. Alternatively, movement mechanism  130  may have a configuration provided with two x-direction guides  132  each of which is engaged with first formation section  122  and discharging section  124 A. 
     In addition, movement mechanism  130  freely moves curing section  124 B in y-direction in accordance with mechanism control information output from control section  110  (see  FIG. 1 ). It is to be noted that movement mechanism  130  may have a configuration in which the position of curing section  124 B is fixed and shaping stage  140  is moved in y-direction, or a configuration in which both of curing section  124 B and shaping stage  140  are moved. 
     In the present embodiment, for the purpose of freely moving first formation section  122  in x-direction and y-direction, discharging section  124 A and curing section  124 B are moved as necessary such that the movement of first formation section  122  is not interfered. In addition, for the purpose of freely moving discharging section  124 A in x-direction and y-direction, first formation section  122  and curing section  124 B are moved as necessary such that the movement of discharging section  124 A is not interfered. In addition, for the purpose of freely moving curing section  124 B in y-direction, x-direction guide  132  is moved in y-direction as necessary such that the movement of curing section  124 B is not interfered. It is also possible to preliminarily set evacuation positions of first formation section  122 , discharging section  124 A and curing section  124 B where first formation section  122 , discharging section  124 A and curing section  124 B do not interfere with each other, so as move first formation section  122 , discharging section  124 A and curing section  124 B to the evacuation positions. 
     In addition, movement mechanism  130  adjusts the interval between shaping-material layer formation section  120  and three-dimensional object  200  by moving shaping stage  140  downward in z-direction in accordance with mechanism control information output from control section  110  (see  FIG. 1 ). That is, shaping stage  140  can be moved by movement mechanism  130  in z-direction, and is moved downward in z-direction by a distance (lamination pitch) corresponding to the thickness of one shaping material layer after Nth (N is a positive integer) shaping material layer is formed on shaping stage  140 . Then, after N+1th shaping material layer is formed on shaping stage  140 , shaping stage  140  is again moved downward in z-direction by the lamination pitch. It is to be noted that movement mechanism  130  may fix the position of shaping stage  140  in z-direction and move shaping-material layer formation section  120  upward in z-direction, or may move both of shaping-material layer formation section  120  and shaping stage  140 . 
       FIGS. 6A to 6J  schematically illustrate an operation of shaping-material layer formation section  120  for forming one shaping material layer. To be more specific,  FIGS. 6A to 6J  illustrate an operation of forming N+1th shaping material layer  215  on Nth shaping material layer  205 .  FIGS. 6A to 6J  illustrate an exemplary case where a columnar shaping article is formed. 
       FIG. 6A  illustrates a state after Nth shaping material layer  205  is formed by shaping-material layer formation section  120 . At this time, shaping material layer  205  has been semi-cured through a curing process of light irradiation device  194  of curing section  124 B. 
       FIG. 6B  illustrates a state where discharging head  160  of first formation section  122  moves to a position over the outline of N+1th shaping material layer  215 , and discharges droplet  170  of the shaping material from discharging nozzle. 
       FIG. 6C  illustrates a state where light irradiation device  162  of first formation section  122  irradiates droplet  170  reaching a shaping surface (in the example illustrated in  FIG. 6C , the surface of Nth shaping material layer  205 ) with light (dotted arrow in  FIG. 6C ) at the timing when droplet  170  of the shaping material discharged from discharging head  160  reaches the shaping surface. 
       FIG. 6D  illustrates a state where discharging head  160  discharges droplet  170  of the shaping material while moving along the outline (annular shape) of N+1th shaping material layer  215 . Although not shown in the drawing, light irradiation device  162  irradiates droplet  170  of the shaping material discharged from discharging head  160  with light while moving as with discharging head  160 . As a result, on Nth shaping material layer  205 , outline  210  of N+1th shaping material layer  215  is formed in a semi-cured state. In this manner, development of curing is started immediately after droplet  170  reaches the shaping surface, and thus outline  210  can be easily maintained in a desired shape. In addition, since it suffices to develop the curing only until a hardness enough to maintain the shape is obtained, the limitation on the performance required for light irradiation device  162  is reduced. 
       FIG. 6E  illustrates a state where discharging device  180  of second formation section  124  has moved to a certain position in the inner portion of outline  210  (for example, a center of the inner portion of outline  210 ) to supply shaping material  182 .  FIG. 6  illustrates an exemplary case where discharging device  180  discharges shaping material  182  while remaining at a center of the inner portion of outline  210 , but discharging device  180  may discharge shaping material  182  while appropriately moving in the inner portion of outline. 
       FIG. 6F  illustrates a state where shaping material  182  discharged from discharging device  180  fills the inner portion of outline  210  little by little.  FIG. 6G  illustrates a state where the inner portion of outline  210  is completely filled with shaping material  182  discharged from discharging device  180  in an uncured state. Here, by forming outline  210  in advance, subsequently supplied uncured shaping material  182  can be surely prevented from leaking out of outline  210 , and a shaping article whose surface shape is correctly reproduced can be obtained. 
       FIG. 6H  illustrates a state where levelling roller  190  of curing section  124 B makes contact with the surface of shaping material  182  discharged by discharging device  180  while moving in the arrow direction to planarize the irregularity on the surface of shaping material  182 . 
       FIG. 6I  illustrates a state where light irradiation device  194  of curing section  124 B performs a light irradiation process on shaping material  182  discharged by discharging device  180  while moving in the arrow direction to develop the curing. It is to be noted that, for convenience of description of the process of each step, levelling roller  190  and light irradiation device  194  are separated from each other in  FIG. 6 . 
       FIG. 6J  illustrates a state where N+1th shaping material layer  215  composed of outline  210  and shaping material  182  (the inner portion of outline  210 ) has been formed through a light irradiation process performed by light irradiation device  194  on the entirety of shaping material  182  discharged by discharging device  180 . In view of development of the curing of the entire shaping material at one time with the irradiation of light irradiation device  194 , the light wavelength range of light irradiation device  194  is preferably set to a value at which the shaping materials of outline  210  and the inner portion are both cured. 
     As has been described in detail, in the first embodiment, three-dimensional shaping apparatus  100  includes first formation section  122  that forms outline  210  of the shaping material layer with a first resolution and a second formation section (discharging section  124 A and curing section  124 B) that forms the inner portion of outline  210  with a second resolution lower than the first resolution by discharging a shaping material toward shaping stage  140 . 
     According to the first embodiment with the above-mentioned configuration, outline  210  of the shaping material layer which is related to the appearance of three-dimensional object  200  and is therefore required to be formed with a high resolution is formed with a resolution higher than that of the inner portion of outline  210 , whereas the inner portion of outline  210  which is not related to the appearance and therefore is not required to be formed with a high resolution is formed with a formation speed lower than that of outline  210 . With this configuration, the resolution of the shaping material layer can be increased without reducing the formation speed of the shaping material layer, and in turn the resolution of three-dimensional object  200  can be increased without reducing the shaping speed of three-dimensional object  200 . 
     While a shaping material having a photosetting property is employed as the shaping material used for the shaping of three-dimensional object  200  in the above-mentioned embodiment, the present invention is not limited to this. For example, it is also possible to adopt a configuration using a thermosetting material as the shaping material in which a heating section that generates heat with a resistance heater or the like heats the shaping material to perform a curing process. The reason for this is that, also when a thermosetting material is used for the shaping material, the problem mentioned in “Technical Problem,” that is, the problem that the approach for increasing the resolution of three-dimensional object  200  reduces the shaping speed of the three-dimensional object  200 . When a thermosetting material is used for the shaping material, a heat polymerization initiator is used in place of the light polymerization initiator, and curing section  124 B is provided with a heating section having a heater and the like in place of light irradiation device  194 . 
     While the inner portion of outline  210  is formed after the operation of forming outline  210  of shaping material layer  215  is started in the above-mentioned embodiment, the present invention is not limited to this. For example, outline  210  of shaping material layer  215  may be formed after the operation of forming the inner portion of outline  210  is started. In addition, the operation of forming outline  210  of shaping material layer  215  and the operation of forming the inner portion of outline  210  may be simultaneously performed. In this case, it is preferable to start the operation of forming the inner portion after outline  210  is formed to a certain degree and to complete the formation of outline  210  before the supply of the shaping material to the internal portion is completed. 
     In the following, a second embodiment will be described in detail with reference to the accompanying drawings.  FIG. 7  schematically illustrates a configuration of three-dimensional shaping apparatus  100  according to the second embodiment. As illustrated in  FIG. 7 , shaping-material layer formation section  120  includes second formation section  124  in place of discharging section  124 A and curing section  124 B of  FIG. 1 . It is to be noted that the same components as those of the first embodiment are denoted with the same reference numerals, and the description thereof will be omitted. 
     As illustrated in  FIGS. 8A to 8C , second formation section  124  includes, in casing  127 , ink-jet discharging head  220  in addition to levelling roller  190 , scraping member  192 , collecting member  193  and light irradiation device  194  of  FIG. 5 . Discharging head  220 , levelling roller  190 , scraping member  192  and light irradiation device  194  are disposed in second formation section  124  in this order from the near side of  FIG. 7 . 
     As illustrated in  FIG. 8B , a plurality of discharging nozzles are arranged in line in a longitudinal direction (x-direction). As this discharging head  220 , a conventionally used and publicly known discharging head for image formation is used. As long as the discharging nozzles are arranged in line, the discharging nozzles may be linearly disposed side by side, or may be arranged side by side in a zigzag form in line as a whole. 
     Discharging head  220  selectively discharges droplet  222  of the shaping material in parallel toward shaping stage  140  from a plurality of discharging nozzles while moving in a sub scanning direction orthogonal to the longitudinal direction. After first formation section  122  has started an operation of forming an outline of the shaping material layer, discharging head  220  discharges droplet  222  to fill the inner portion of the outline to form the inner portion under the control of control section  110 . 
     It suffices that discharging head  220  discharges droplet  222  to fill the inner portion of the outline of the shaping material layer (that is, high resolution is not required for formation of the inner portion of the outline), the nozzle diameter of each discharging nozzle  221  of discharging head  220  is greater than that of the discharging nozzle of discharging head  160 . Thus, clogging of discharging nozzle  221  of discharging head  220  can be prevented. In addition, discharging head  220  can discharge a droplet larger than the droplet discharged from discharging head  160 . That is, discharging head  220  shapes the inner portion of the outline with a resolution lower than that of the outline, and thus can form the inner portion of the outline of the shaping material layer with a formation speed higher than that of discharging head  160 . That is, discharging device  220  can complete the application of the shaping material to an area in a shorter time in comparison with discharging head  160 . 
     When the supporting material is required, it is also possible to adopt a configuration illustrated in  FIG. 8C  in which second formation section  124  is provided with a second discharging head having a discharging port with a large diameter as with the discharging head (first discharging head)  220 . In this case, the supporting material may be discharged from the second discharging device such that the supporting material is in contact with the discharged model material after discharging of the model material for one layer from first discharging head  220  is completed, or the model material may be discharged from first discharging head  220  such that the model material is in contact with the discharged supporting material after discharging of the supporting material for one layer from second discharging head  220  is completed. In addition, the shaping materials (the model material and the supporting material) may be respectively discharged from first and second discharging heads  220  in parallel. 
     Levelling roller  190  makes contact with the surface of droplet  222  discharged by discharging head  220  to planarize the surface of droplet  222 . As a result, a shaping material layer (the outline and the inner portion of the outline) having a uniform layer thickness is formed. Scraping member  192  is a blade provided in the proximity of levelling roller  190  and scrapes the shaping material attached on the surface of levelling roller  190 . Light irradiation device  194  performs a curing process (light irradiation process) on droplet  222  of the photosetting resin discharged by discharging head  220 , and semi-cures droplet  222 . 
     Movement mechanism  130  two-dimensionally changes the relative position of second formation section  124  and shaping stage  140 . To be more specific, movement mechanism  130  includes x-direction guide  132  that is engaged with first formation section  122 , y-direction guide  134  that guides x-direction guide  132  and second formation section  124  in y-direction, and z-direction guide  136  that guides shaping stage  140  in z-direction as illustrated in  FIG. 7 . Further, movement mechanism  130  includes a drive mechanism composed of a motor, a drive reel and the like which are not illustrated. 
     Movement mechanism  130  freely moves second formation section  124  in y-direction in accordance with mechanism control information output from control section  110  (see  FIG. 7 ). It is to be noted that movement mechanism  130  may have a configuration in which the position of second formation section  124  is fixed and shaping stage  140  is moved in y-direction, or a configuration in which second formation section  124  and shaping stage  140  are moved. 
     In the present embodiment, for the purpose of freely moving first formation section  122  in x-direction and y-direction, second formation section  124  is moved as necessary in y-direction such that the movement of first formation section  122  is not interfered. In addition, for the purpose of freely moving second formation section  124  in y-direction, x-direction guide  132  is moved in y-direction as necessary such that the movement of second formation section  124  is not interfered. It is also possible to preliminarily set evacuation positions of first formation section  122  and second formation section  124  where first formation section  122  and second formation section  124  do not interfere with each other, so as to move first formation section  122  and second formation section  124  to the evacuation positions. 
       FIGS. 9A to 9D  schematically illustrate operations of second formation section  124  for forming an inner portion of an outline of the shaping material layer. To be more specific, FIGS.  9 A to  9 D illustrate an operation of forming N+1th shaping material layer  225  on Nth shaping material layer  205 . 
       FIG. 9A  illustrates a state where outline  210  of N+1th shaping material layer  225  has been formed in a semi-cured state on Nth shaping material layer  205 . Discharging head  220  of second formation section  124  moves to a position near outline  210  of N+1th shaping material layer  225 . 
       FIG. 9B  illustrates a state where discharging head  220  moves across the inner portion of outline  210  in the arrow direction, and discharges droplet  222  of the shaping material. Subsequent to the operation of discharging head  220  for discharging droplet  222 , levelling roller  190  makes contact with the surface of droplet  222  discharged by discharging head  220  while moving in the arrow direction to planarize the irregularity of the surface of droplet  222 . 
       FIG. 9C  illustrates a state where light irradiation device  194  performs a light irradiation process on droplet  222  discharged by discharging head  220  while moving in the arrow direction to develop the curing. It is to be noted that, for convenience of description of the process of each step, levelling roller  190  and light irradiation device  194  are separated from each other in  FIG. 9 . 
       FIG. 9D  illustrates a state where light source  194  performs a light irradiation process on the entirety of droplet  222  discharged by discharging head  220  to form N+1th shaping material layer  225  composed of droplet  222  (the inner portion of outline  210 ) and outline  210  in a semi-cured state. 
     As described above, in the second embodiment, second formation section  124  includes discharging head  220 , levelling roller  190 , scraping member  192  and light irradiation device  194 , and simultaneously performs an operation of forming the inner portion of the outline of the shaping material layer (droplet  222 ), an operation of planarizing the surface of droplet  222  and an operation of curing droplet  222  while moving in y-direction. Therefore, in comparison with the first embodiment, the operation of shaping-material layer formation section  120  can be simplified, and the formation speed for one shaping material layer can be increased. 
     In the following, a third embodiment will be described in detail with reference to the accompanying drawings.  FIG. 10  illustrates a configuration of second formation section  124  according to the third embodiment. As illustrated in  FIG. 10 , second formation section  124  includes, in place of discharging head  220  of  FIG. 8 , application roller  230 , dispenser  240  that supplies a shaping material toward application roller  230 , and blade  250   a  that sets the thickness of the shaping material supplied to application roller  230  to a certain thickness. It is to be noted that the same components as those of the second embodiment are denoted with the same reference numerals, and the description thereof will be omitted. 
     Application roller  230  can be driven into rotation under the control of control section  110 , and applies droplet  232  (shaping material) formed on the surface of application roller  230  to shaping stage  140  while moving in y-direction orthogonal to the longitudinal direction. After the operation of first formation section  122  for forming an outline of the shaping material layer is started, application roller  230  applies droplet  232  to the inner portion of the outline to fill the inner portion, thereby forming the inner portion under the control of control section  110 . The thickness of droplet  232  formed on the surface of application roller  230  is greater than the thickness of the outline formed by first formation section  122 . With this configuration, at the time of application of droplet  232 , application roller  230  does not make contact with the outline of the shaping material layer, and droplet  232  formed on the surface of application roller  230  makes contact with the inner portion of the outline of the shaping material layer. 
     Here, in view of preventing droplet  232  from adhering to the outline of the shaping material layer at the time when droplet  232  formed on the surface of application roller  230  makes contact with the outline, it is preferable to perform a process for providing ink repellency to the surface of the outline. 
     Levelling roller  190  makes contact with the surface of droplet  232  applied by application roller  230  to planarize the surface of droplet  232 . As a result, a shaping material layer (the outline and the inner portion of the outline) having a uniform layer thickness is formed. Scraping member  192  is a blade provided at a position near levelling roller  190  and scrapes the shaping material attached on the surface of levelling roller  190 . Light irradiation device  194  performs a curing process (light irradiation process) on droplet  232  of the photosetting resin applied by application roller  230  to semi-cure droplet  232 . 
       FIGS. 11A to 11C  schematically illustrate an operation of application roller  230  for forming the inner portion of the outline of the shaping material layer. To be more specific,  FIGS. 11A to 11C  illustrate an operation of forming N+1th shaping material layer  235  on Nth shaping material layer  205 . 
       FIG. 11A  illustrates a state where outline  210  of N+1th shaping material layer  235  has been formed in a semi-cured state on Nth shaping material layer  205 . Application roller  230  of second formation section  124  moves to a position near outline  210  of N+1th shaping material layer  235 . 
       FIG. 11B  illustrates a state where application roller  230  moves across the inner portion of outline  210  and applies droplet  232  of the shaping material to the inner portion. Although not shown in the drawing, subsequent to the operation of applying droplet  232  to application roller  230 , levelling roller  190  planarizes the irregularity on the surface of droplet  232 , and light irradiation device  194  performs a light irradiation process on droplet  232  to semi-cure droplet  232 . 
       FIG. 11C  illustrates a state where N+1th shaping material layer  235  composed of droplet  232  (the inner portion of outline  210 ) and outline  210  in a semi-cured state has been formed through a light irradiation process performed by light irradiation device  194  on the entirety of droplet  232  discharged by application roller  230 . 
     As described above, in the third embodiment, application roller  230  applies droplet  232  to the inner portion of the outline of the shaping material layer to fill the inner portion, thereby forming the inner portion. The application amount per unit time of application roller  230  is greater than the discharging rate per unit time of discharging head  220  of the second embodiment. Therefore, in comparison with the second embodiment, the formation speed for the inner portion of the outline of the shaping material layer can be increased, and in turn the formation speed for one shaping material layer can be increased. It is to be noted that, in the present embodiment, application roller  230  applies the shaping material to the inner portion of the outline at one time, and therefore the inner portion of the outline can be considered to have no resolving property. Thus, naturally, first formation section  122  forms the outline with a resolution higher than that of second formation section  124 , and second formation section  124  forms the inner portion of the outline with a resolution lower than that of first formation section  122 . 
     Preferably, in the first and second embodiments, the shaping material discharged from discharging head  160  is a shaping material having a sol-gel phase transition temperature. For example, it is preferable to use a shaping material having a sol-gel phase transition temperature higher than normal temperature (natural temperature without heating or cooling). Here, the sol-gel phase transition temperature is a temperature at which the value of the viscosity of the liquid exceeds 500 [mP·s] when the temperature of a liquid in sol state of is being reduced. When the value of the viscosity exceeds 500 [mP·s], a droplet having a size of tens of micrometers do not flow as long as an external force is not applied thereto. That is, the shape of the droplet can be kept as it is. 
       FIG. 12  shows the temperature dependency of the viscosity of a shaping material having a sol-gel phase transition temperature. The value of the viscosity was obtained using rheometer MCR300 (available from Anton Paar GmbH) under a condition of a shear rate of 1000 [1/s]. In  FIG. 12 , L 1  indicates the temperature dependency of the viscosity of a shaping material which does not have a sol-gel phase transition temperature. L 2  indicates the temperature dependency of the viscosity of a shaping material which has a sol-gel phase transition temperature higher than normal temperature. 
     As illustrated in  FIG. 12 , the viscosity of the shaping material (L 1 ) which does not have a sol-gel phase transition temperature linearly increases as the temperature is reduced, but does not exceed 500 [mP·s] even when the temperature is reduced to approximately 10[° C.], and phase transition from sol state to gel state does not occur. Meanwhile, the value of the viscosity of shaping material (L 2 ) which has a sol-gel phase transition temperature higher than normal temperature exceeds 500 [mP·s] at approximately 45[° C.], and phase transition from sol state to gel state occurs. 
     In the first and second embodiments, discharging head  160  can discharge the shaping material within a viscosity range of 5 to 15 [mP·s]. Therefore, when a shaping material having a sol-gel phase transition temperature higher than normal temperature is used, the shaping material in sol state can be discharged by heating discharging head  160  to 70 to 80[° C.], and the impinging droplet thus discharged is instantly naturally cooled to 45[° C.], thus causing phase transition from sol state to gel state. Consequently, it is possible to prevent wet spreading on shaping surface  172  from occurring at the timing when droplet  170  discharged from discharging head  160  reaches shaping surface  172 . That is, it is not necessary to irradiate droplet  170  reaching shaping surface  172  with light from light irradiation device  162  to cure droplet  170  at the timing when droplet  170  reaches shaping surface  172 , and curing can be performed by emitting light from light irradiation device  194 . As described, when a shaping material having a sol-gel phase transition temperature higher than normal temperature is used, the shaping material stored in discharging head  160  is required to be in sol state, and therefore it is preferable to provide a heating section that heats discharging head  160  (see  FIG. 13 ). 
     In the configuration illustrated in  FIG. 13 , heater  168  is provided at the outer periphery of discharging head  160  with heat transfer member  166  therebetween. The output of heater  168  is controlled by control section  110 . Heater  168  is connected with a heater power source not illustrated. Heat transfer member  166  is extended to the discharging nozzle surface of discharging head  160 . That is, heat transfer member  166  efficiently transfers the heat of heater  168  to the channel of the shaping material discharged from discharging head  160 , and, to the discharging nozzle surface and its surroundings, thereby heating the air around the discharging nozzle surface. Control section  110  controls the output of heater  168  so as to heat discharging head  160  to a temperature equal to or higher than the sol-gel phase transition temperature. With this configuration, even a shaping material having a sol-gel phase transition temperature higher than normal temperature can be discharged from discharging head  160 . 
     It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors in so far as they are within the scope of the appended claims or the equivalents thereof. While the invention made by the present inventor has been specifically described based on the preferred embodiments, it is not intended to limit the present invention to the above-mentioned preferred embodiments but the present invention may be further modified within the scope and spirit of the invention defined by the appended claims. 
     This application is entitled to and claims the benefit of Japanese Patent Application No. 2013-208327 filed on Oct. 3, 2013, the disclosure of which including the specification, drawings and abstract is incorporated herein by reference in its entirety. 
     REFERENCE SIGNS LIST 
     
         
           100  Three-dimensional shaping apparatus 
           110  Control section 
           120  Shaping-material layer formation section 
           122  First formation section 
           124  Second formation section 
           124 A Discharging section 
           124 B Curing section 
           130  Movement mechanism 
           132  x-direction guide 
           134  y-direction guide 
           136  z-direction guide 
           140  Shaping stage 
           150  Data input section 
           155  Computer apparatus 
           160 ,  220  Discharging head 
           162 ,  194  Light irradiation device 
           164  Clogging detection section 
           166  Heat transfer member 
           168  Heater 
           170 ,  182 ,  222 ,  232  Droplet (Shaping material) 
           172  Shaping surface 
           180  Discharging device 
           190  Levelling roller 
           192  Scraping member 
           200  Three-dimensional object 
           205 ,  215 ,  225 ,  235  Shaping material layer 
           210  Outline 
           230  Application roller