Patent Publication Number: US-2021170526-A1

Title: Lamination molding apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority benefit of Japan application serial no. 2019-219664, filed on Dec. 4, 2019. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification. 
     BACKGROUND 
     Technical Field 
     The disclosure relates to a lamination molding apparatus. 
     Description of Related Art 
     Various methods have been known as lamination molding methods for a three-dimensional molded object. As an example, a lamination molding apparatus which carries out powder bed fusion forms a material layer on a molding region, which is a region in which the desired three-dimensional molded object is formed. Then, the lamination molding apparatus sinters or melts the material layer and forms a solidified layer by scanning a laser beam at a predetermined position of the material layer. Then, the lamination molding apparatus repeats the formation of the material layer and the formation of the solidified layer to laminate a plurality of solidified layers and thereby produce the three-dimensional molded object. 
     As a scanning means for irradiating the laser beam to the predetermined position, a galvano scanner may be used. The galvano scanner includes two galvano mirrors that reflect the laser beam and an actuator that rotates each galvano mirror to a predetermined angle. 
     US Patent Publication No. 2019/0151945 has disclosed a lamination molding apparatus including a plurality of galvano scanners to simultaneously irradiate laser beams to a plurality of positions in the molding region. 
     SUMMARY 
     Problem to be Solved 
     From the perspective of speeding up the molding, it is favorable that a plurality of galvano scanners can be simultaneously used regardless of the shape or the position of the molded object. In other words, it is desirable that the irradiable ranges of the laser beams of the respective galvano scanners cover the entire molding region. Besides, from the perspective of stabilizing the molding quality, it is desirable that the shape of the irradiation spot as well as the energy density of the laser beam irradiated to the predetermined position are substantially constant regardless of which galvano scanner is used for scanning. In other words, it is desirable that the difference be as little as possible among the incident angles of the laser beams scanned by the respective galvano scanners. 
     The disclosure has been made in view of the above circumstances, and provides a lamination molding apparatus including a plurality of galvano scanners which increases the molding speed as well as stabilizing the molding quality. 
     Means for Solving the Problems 
     According to the disclosure, a molding lamination apparatus is provided. The molding lamination apparatus includes: a chamber, covering a molding region; and an irradiation device, in each divided layer formed by dividing a desired three-dimensional molded object at a predetermined height, irradiating a laser beam to a material layer formed in the molding region to form a solidified layer. The irradiation device includes at least one laser source, generating the laser beam; a first galvano scanner, scanning the laser beam; a second galvano scanner, scanning the laser beam; and an irradiation controller, controlling the at least one laser source, the first galvano scanner, and the second galvano scanner. The first galvano scanner includes: a first X-axis galvano mirror, scanning the laser beam in an X-axis direction; a first X-axis actuator, rotating the first X-axis galvano mirror; a first Y-axis galvano mirror, scanning the laser beam in a Y-axis direction perpendicular to the X-axis direction; and a first Y-axis actuator, rotating the first Y-axis galvano mirror. The second galvano scanner includes: a second X-axis galvano mirror, scanning the laser beam in the X-axis direction; a second X-axis actuator, rotating the second X-axis galvano mirror; a second Y-axis galvano mirror, scanning the laser beam in the Y-axis direction; and a second Y-axis actuator, rotating the second Y-axis galvano mirror. Irradiable ranges of the laser beams by using the first galvano scanner and the second galvano scanner respectively include the entire molding region. The first X-axis galvano mirror and the first Y-axis galvano mirror are disposed to be plane-symmetric to the second X-axis galvano mirror and the second Y-axis galvano mirror. 
     Inventive Effects 
     In the lamination molding apparatus according to the disclosure, the irradiable ranges of the laser beams by using the first galvano scanner and the second galvano scanner include the entire molding region. In addition, the first X-axis galvano mirror and the first Y-axis galvano mirror of the first galvano scanner, and the second X-axis galvano mirror and the second Y-axis galvano mirror of the second galvano scanner are disposed to be plane-symmetric to each other. Accordingly, the molding can be performed more efficiently regardless of the shape or the position of the molded object. In addition, by disposing the first galvano scanner and the second galvano scanner to be close, the difference between the incident angles of the respective galvano scanners can be decreased, and the molding quality can be stabilized. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view illustrating the configuration of a lamination molding apparatus according to a first embodiment of the disclosure. 
         FIG. 2  is a perspective view illustrating a material layer forming device  3  of the lamination molding apparatus of  FIG. 1 . 
         FIG. 3  is a perspective view illustrating a recoater head  11  from a top perspective. 
         FIG. 4  is a perspective view illustrating the recoater head  11  from a bottom perspective. 
         FIG. 5  is a top view illustrating an irradiation device  13  according to the first embodiment. 
         FIG. 6  illustrates the configuration of a portion of components of the irradiation device  13  of  FIG. 5 . 
         FIG. 7  illustrates an example of laser beams irradiated by the irradiation device  13 . 
         FIG. 8  illustrates a lamination molding method using the lamination molding apparatus according to the first embodiment. 
         FIG. 9  illustrates a position relationship between the irradiation device  13  and a molding region R according to the first embodiment from a top perspective. 
         FIG. 10  illustrates an example of an irradiation region irradiated by the irradiation device  13  according to the first embodiment. 
         FIG. 11  illustrates paths of laser beams L 1  and L 2  when irradiating a point Q in the irradiation region of  FIG. 10 . 
         FIG. 12  illustrates a lamination molding method using the lamination molding apparatus according to the first embodiment of the disclosure. 
         FIG. 13  is a schematic view illustrating the configuration of an irradiation device  113  of a lamination molding apparatus according to a second embodiment of the disclosure. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     In the following, the embodiments of the disclosure will be described with reference to the drawings. The various features shown in the following embodiments may be combined with each other. In addition, the disclosure is independently established for each feature. 
     A lamination molding apparatus of the embodiment, in each divided layer formed by dividing a desired three-dimensional molded object at a predetermined thickness, repetitively forms a material layer  8  and forms a solidified layer to form a three-dimensional molded object. As shown in  FIG. 1 , the lamination molding apparatus according to the first embodiment of the disclosure includes a chamber  1 , a material layer forming device  3 , and an irradiation device  13 . 
     The chamber  1  covers a molding region R required as a region for forming the desired three-dimensional molded object. An inert gas having a predetermined concentration is supplied from an inert gas supplier to the chamber  1 . In addition, the inert gas containing fumes generated during formation of a solidified layer is discharged from the chamber  1 . The inert gas supplier is, for example, an inert gas generator that generates the inert gas at the predetermined concentration from surrounding air or a gas cylinder that stores the inert gas at the predetermined concentration. Preferably, the fumes of the inert gas discharged from the chamber  1  may be removed by a fume collector, and the inert gas may be returned to the chamber  1 . The fume collector is, for example, an electric precipitator or a filter. In the disclosure, the inert gas is a gas that does not substantially react with the material layer  8  or the solidified layer, and, in response to the type of the molding material, may be a suitable gas selected from a nitrogen gas, an argon gas, a helium gas, etc. 
     On a top surface of the chamber  1 , a chamber window  1   a  for laser beams L 1  and L 2  to pass through is disposed. The chamber window  1   a  is formed by a material which the laser beams L 1  and L 2  can pass through. Specifically, the material of the chamber window  1  a, in response to the type of the laser beams L 1  and L 2 , may be selected from quartz glass or borosilicate glass, or crystals of germanium, silicon, zinc selenium or potassium bromide. For example, in the case where the laser beams L 1  and L 2  are fiber laser or YAG laser, the chamber window  1   a  may be formed by quartz glass. 
     In addition, on the top surface of the chamber  1 , a fume diffuser  17  covering the chamber window  1   a  is disposed. The fume diffuser  17  includes a cylindrical casing  17   a  and a cylindrical diffusing member  17   c  disposed in the casing  17   a . An inert gas supply space  17   d  is defined between the casing  17   a  and the diffusing member  17   c . In addition, on a bottom surface of the casing  17   a , an opening  17   b  is provided on an inner side of the diffusing member  17   c . A plurality of pores  17   e  are provided on the diffusing member  17   c , and the clean inert gas supplied to the inert gas supply space  17   d  fills a clean room  17   f  through the pores  17   e . The clean inert gas that fills the clean room  17   f  is then jetted toward a bottom of the fume diffuser  17  through the opening  17   b . With such configuration, the fume can be prevented from attaching to the chamber window  1   a , and the fumes can be eliminated from an irradiation path of the laser beams L 1  and L 2 . 
     The material layer forming device  3  is disposed in the chamber  1 . As shown in  FIG. 2 , the material layer forming device  3  includes a base  4  provided with the molding region R and a recoater head  11  disposed on the base  4 . The recoater head  11  is configured to be reciprocally movable in a horizontal direction (the direction of an arrow B) by a recoater head driving mechanism  12 . 
     As shown in  FIGS. 3 and 4 , the recoater head  11  includes a material container  11   a , a material supply port  11   b , and a material discharge port  11   c . In the embodiment, a metallic material powder is used as the molding material for forming the material layer  8 . 
     The material supply port  11   b  is disposed on a top surface of the material container  11   a , and is a receiving port of the material powder supplied from a material supply unit (not shown) to the material container  11   a . The material discharge port  11   c  is disposed on a bottom surface of the material container  11   a  and discharges the material powder in the material container  11   a . The material discharge port  11   c  has a slit shape that extends in a longitudinal direction of the material container  11   a . Blades  11   fb  and  11   rb  are provided on two side surfaces of the recoater head  11 , respectively. The blades  11   fb  and  11   rb  planarize the material powder discharged from the material discharge port  11   c  to form the material layer  8 . 
     As shown in  FIGS. 1 and 2 , the molding region R is positioned on a molding table  5 . The molding table  5  is movable in a vertical direction (the direction of an arrow U) by a molding table driving mechanism (not shown). At the time of molding, a base plate  6  is disposed on the molding table  5 , and the material layer  8  is formed on the base plate  6 . 
     As shown in  FIG. 1 , the irradiation device  13  is disposed above the chamber  1 . The irradiation device  13  irradiates the laser beams L 1  and L 2  to a predetermined position of the material layer  8  formed on the molding region R to melt or sinter and solidify the material layer  8  at the irradiation position. As shown in  FIGS. 1 and 5 , the irradiation device  13  includes a first laser source  31 , a second laser source  41 , a first aperture  33 , a second aperture  43 , a first focus control unit  34 , a second focus control unit  44 , a first adjustment lens  35 , a second adjustment lens  45 , a first galvano scanner  32 , a second galvano scanner  42 , and an irradiation controller  30 . In the following, a horizontal direction in the molding region R is set as an X-axis, and a horizontal direction perpendicular to the X-axis is set as a Y-axis. In addition, along the paths of the laser beams L 1  and L 2 , a side relatively close to the first laser source  31  or the second laser source  41  is set as an upstream side, and a side relatively close to the material layer  8  is set as a downstream side. 
     The first laser source  31  generates the laser beam L 1 , and the second laser source  41  generates the laser beam L 2 . The laser beams LI and L 2  may be any laser beams as long as they are capable of sintering or melting the material powder. Examples of the laser beams L 1  and L 2  include fiber laser, CO2 laser, and YAG laser. In the embodiment, fiber laser is used. As described in the following, while the laser beams L 1  and L 2  generated by the two laser sources  31  and  41  are respectively scanned by the first galvano scanner  32  and the second galvano scanner  42  in the embodiment, it may also be that the laser beam generated by one laser source is split, and the split laser beams are respectively scanned by the first galvano scanner  32  and the second galvano scanner  42 . 
     As shown in  FIGS. 5 and 6 , the first aperture  33 , the second aperture  43 , the first focus control unit  34 , the second focus control unit  44 , the first adjustment lens  35 , the second adjustment lens  45 , the first galvano scanner  32 , and the second galvano scanner  42  are integrally disposed in a casing  14  having an opening  14   a  at a bottom. In other words, the single casing  14  accommodates the first galvano scanner  32  and the second galvano scanner  42 . In the opening  14   a , an irradiation device window  14   b  that the laser beams L 1  and L 2  pass through is disposed. The irradiation device window  14   b  is formed by a material which the laser beams L 1  and L 2  can pass through. Specifically, the material of the irradiation device window  14   b , in response to the type of the laser beams L 1  and L 2 , may be selected from quartz glass or borosilicate glass, or crystals of germanium, silicon, zinc selenium or potassium bromide. For example, in the case where the laser beams L 1  and L 2  are fiber laser or YAG laser, the irradiation device window  14   b  may be configured by quartz glass. In addition, in the casing  14 , a first control substrate  38  electrically connected with the first galvano scanner  32  and the first focus control unit  34  and a second control substrate  48  electrically connected with the second galvano scanner  42  and the second focus control unit  44  are disposed. The first galvano scanner  32  includes a first X-axis galvano mirror  32   a , a first X-axis actuator  32   c , a first Y-axis galvano mirror  32   b , and a first Y-axis actuator  32   d . The second galvano scanner  42  includes a second X-axis galvano mirror  42   a , a second X-axis actuator  42   c , a second Y-axis galvano mirror  42   b , and a second Y-axis actuator  42   d.    
     The first laser source  31  is connected with the first aperture  33  via a connector  37  disposed on a back surface of the casing  14 . The second laser source  41  is connected with the second aperture  43  via a connector  47  disposed on the back surface of the casing  14 . The first aperture  33  and the second aperture  43  serve as diaphragms that allow a central portions of the laser beams L 1  and L 2  from the first laser source  31  and the second laser source  41  to pass through. Accordingly, an energy distribution of the irradiated laser beams L 1  and L 2  can be stabilized. 
     The first focus control unit  34  includes a focus control lens  34   a  inside. The second focus control unit  44  includes a focus control lens  44   a  inside. The focus control lenses  34   a  and  44   a  in the embodiment are plano-convex lenses which, along the respective paths of the laser beams L 1  and L 2  from the first laser source  31  and the second laser source  41 , are planar on the upstream side and convex on the downstream side. The focus control lenses  34   a  and  44   a  are forward/backward-movable by motors incorporated in the focus control units  34  and  44  along the paths of the laser beams L 1  and L 2 , and therefore can adjust spot diameters of the laser beams L 1  and L 2  that pass through the respective focus control lenses  34   a  and  44   a . The spot diameters of the laser beams L 1  and L 2  are controlled by driving currents input to the motors of the focus control units  34  and  44  based on command signals received from the irradiation controller  30  via the control substrates  38  and  48 . 
     The laser beams L 1  and L 2  that respectively pass through the focus control lenses  34   a  and  44   a  are respectively condensed by the first adjustment lens  35  and the second adjustment lens  45 . The first adjustment lens  35  and the second adjustment lens  45  of the embodiment are plano-convex lenses which, along the respective paths of the laser beams L 1  and L 2 , planar on the upstream side and convex on the downstream side. Positions of the first adjustment lens  35  and the second adjustment lens  45  can be adjusted manually, and the first adjustment lens  35  and the second adjustment lens  45  serve to fine-tune the spot diameters that may cause an error in attaching the device, etc. 
     As shown in  FIGS. 6 and 7 , the first galvano scanner  32  controllably two-dimensionally scans the laser beam L 1  that passes through the first adjustment lens  35 . Specifically, the laser beam L 1  is reflected by the first X-axis galvano mirror  32   a  rotated by the first X-axis actuator  32   c  and scanned in the X-axis direction of the molding region R, and is reflected by the first Y-axis galvano mirror  32   b  rotated by the first Y-axis actuator  32   d  and scanned in the Y-axis direction of the molding region R. Rotation angles of the first X-axis galvano mirror  32   a  and the first Y-axis galvano mirror  32   b  are controlled by driving currents input to the first X-axis actuator  32   c  and the first Y-axis actuator  32   d  based on command signals received from the irradiation controller  30  via the control substrate  38 . Here, the first galvano scanner  32  is configured as being capable of irradiating any position in the molding region R. In other words, the irradiable range of the first galvano scanner  32  includes the entire molding region R. 
     The second galvano scanner  42  controllably two-dimensionally scans the laser beam L 2  that passes through the second adjustment lens  45 . Specifically, the laser beam L 2  is reflected by the second X-axis galvano mirror  42   a  rotated by the second X-axis actuator  42   c  and scanned in the X-axis direction of the molding region R, and is reflected by the second Y-axis galvano mirror  42   b  rotated by the second Y-axis actuator  42   d  and scanned in the Y-axis direction of the molding region R. Rotation angles of second X-axis galvano mirror  42   a  and the second Y-axis galvano mirror  42   b  are controlled by driving currents input to the second X-axis actuator  42   c  and the second Y-axis actuator  42   d  based on command signals received from the irradiation controller  30  via the control substrate  48 . Here, the second galvano scanner  42  is configured as being capable of irradiating any position in the molding region R. In other words, the irradiable range of the second galvano scanner  42  includes the entire molding region R. 
     In  FIGS. 6 and 7 , a symmetry plane P is a plane that is equidistant from an optical axis of the laser beams L 1  and L 2  passing through the adjustment lenses  35  and  45  and is perpendicular to the molding region R. The first X-axis galvano mirror  32   a  and the first Y-axis galvano mirror  32   b  of the first galvano scanner  32  and the second X-axis galvano mirror  42   a  and the second Y-axis galvano mirror  42   b  of the second galvano scanner  42  are disposed to be plane-symmetric to each other with respect to the symmetry plane P. As shown in  FIGS. 6 and 7 , when the side relatively close to the laser source  31  and  41  is set as the upstream side, and the side relatively close to the material layer  8  is set as the downstream side along the paths of the laser beams L 1  and L 2 , the first X-axis galvano mirror  32   a  and the first Y-axis galvano mirror  32   b  of the first galvano scanner  32  and the second X-axis galvano mirror  42   a  and the second Y-axis galvano mirror  42   b  of the second galvano scanner  42  are disposed to be plane-symmetric to each other with respect to the symmetry plane P which is perpendicular to the molding region R, so that a distance between the downstream galvano mirror of the first X-axis galvano mirror  32   a  and the first Y-axis galvano mirror  32   b  of the first galvano scanner  32  (i.e., the first X-axis galvano mirror  32   a  in the embodiment) and the downstream galvano mirror of the second X-axis galvano mirror  42   a  and the second Y-axis galvano mirror  42   b  of the second galvano scanner  42  (i.e., the second X-axis galvano mirror  42   a  in the embodiment) is smaller than a distance between the upstream galvano mirror of the first X-axis galvano mirror  32   a  and the first Y-axis galvano mirror  32   b  of the first galvano scanner  32  (i.e., the first Y-axis galvano mirror  32   b  in the embodiment) and the upstream galvano mirror of the second X-axis galvano mirror  42   a  and the second Y-axis galvano mirror  42   b  of the second galvano scanner  42  (i.e., the second Y-axis galvano mirror  42   b  in the embodiment). 
     It is desirable that the first galvano scanner  32  and the second galvano scanner  42  be disposed to be closer to each other within the extent that the first galvano scanner  32  and the second galvano scanner  42  do not physically interfere with each other. In other words, it is preferable that a distance between reflected positions of the laser beams L 1  and L 2  on the downstream side in the respective galvano scanners  32  and  42  be shorter. Specifically, it is preferable that the respective galvano scanners  32  and  42  may be disposed so that the distance between the first reflected position of the laser beam L 1  of the downstream galvano mirror of the first X-axis galvano mirror  32   a  and the first Y-axis galvano mirror  32   b  of the first galvano scanner  32  (i.e., the reflected position in the first X-axis galvano mirror  32   a  in the embodiment) and the second reflected position of the laser beam L 2  of the downstream galvano mirror of the second X-axis galvano mirror  42   a  and the second Y-axis galvano mirror  42   b  of the second galvano scanner  42  (i.e., the reflected position in the second X-axis galvano mirror  42   a  in the embodiment), when the laser beams L 1  and L 2  are irradiated, is preferably constantly 150 mm or less, and more preferably 100 mm or less. Since the first galvano scanner  32  and the second galvano scanner  42  are disposed so as to be plane-symmetric with each other, the physical interference does not occur, and the first galvano scanner  32  and the second galvano scanner  42  can be disposed with the distance between the first reflected position and the second reflected position being 150 mm or less. 
     In  FIG. 7 , a first incident angle of the laser beam L 1  on an incident plane at the time when the laser beam L 1  is irradiated to a predetermined position in the molding region R by the first galvano scanner  32  with respect to the vertical direction is set as θ 1 [°], and a second incident angle of the laser beam L 2  on an incident plane at the time when the laser beam L 2  is irradiated to a predetermined position in the molding region R by the second galvano scanner  42  with respect to the vertical direction is set as θ 2 [°]. In addition, the laser beams L 1  and L 2  respectively form irradiation spots R 1  and R 2  on the material layer  8  in the molding region R. Here, the irradiation spot refers to the shape of the laser beam at the irradiation position. As will be described in the following, in order to further reduce the difference between the energy densities or the shapes of the irradiation spots R 1  and R 2  to reduce the variation in the molding quality, it is desirable that the difference between the first incident angle θ 1  and the second incident angle θ 2  be smaller. In the embodiment, the irradiation device  13  is configured so that, at any position in the molding region R, the absolute value of the difference between the first incident angle θ 1  and the second incident angle θ 2  at the time when the laser beams L 1  and L 2  are irradiated is constantly 7 degrees or less, and more preferably 3 degrees or less. 
     The position of the irradiation device  13  in the horizontal direction is preferably configured so that the reflected positions of the laser beams L 1  and L 2  of the downstream galvano mirrors of the first galvano scanner  32  and the second galvano scanner  42  are positioned above the substantially central position of the molding region R. 
     As shown in  FIG. 8 , the laser beams L 1  and L 2  passing through the first galvano scanner  32  and the second galvano scanner  42  pass through the irradiation device window  14   b  and the chamber window  1  a to be irradiated to the predetermined positions of the material layer  8  formed on the molding region R. Since the reflected positions of the laser beams L 1  and L 2  of the downstream galvano mirrors are configured to be positioned above the substantially central position of the molding region R, a transmission window for the laser beams L 1  and L 2  in the chamber  1  can be configured by the relatively smaller chamber window  1   a . In other words, the laser beam L 1  scanned by the first galvano scanner  32  and the laser beam L 2  scanned by the second galvano scanner  42  pass through the single chamber window  1   a . Therefore, the chamber window  1  a can be more easily cleaned and replaced. 
     The irradiation controller  30  includes a hardware component in which a processor, a memory, various circuits are properly assembled. The irradiation controller  30  analyzes a molding program file including specific commands relating to the scan paths of the laser beams L 1  and L 2  that are transmitted from a numerical control device not shown herein and generates laser beam irradiation data. In addition, the irradiation controller  30  transmits desired command signals based on the laser beam irradiation data, and the driving currents whose magnitudes correspond to the command signals are input to the actuators  32   c  and  32   d  of the first galvano scanner  32  and the actuators  42   c , and  42   d  of the second galvano scanner  42 . With the driving currents, the respective galvano mirrors  32   a ,  32   b ,  42   a , and  42   b  form the desired rotation angles. Accordingly, the irradiation positions of the laser beams L 1  and L 2  on the molding region R are determined. In addition, the irradiation controller  30  controls the laser sources  31  and  41  and performs control relating to on/off, intensity, etc., of the laser beams L 1  and L 2 . 
     Nevertheless, the irradiation device  13  is not limited to the above. For example, an fθ lens may be disposed in place of the first focus control unit  34  and the second focus control unit  44 . In addition, while the focus control lenses  34   a  and  44   a  in the first focus control unit  34  and the second focus control unit  44  of the embodiment are condensing lenses, diffusing lenses may also be used as the focus control lenses  34   a  and  44   a . In addition, while the first X-axis galvano mirror  32   a  and the second X-axis galvano mirror  42   a  are disposed on the downstream side in the first galvano scanner  32  and the second galvano scanner  42 , the first Y-axis galvano mirror  32   b  and the second Y-axis galvano mirror  42   b  may also be disposed on the downstream side. Nevertheless, it is desirable that the intensities, types of the respective laser beams L 1  and L 2 , the types of the optical members which the respective laser beams L 1  and L 2  pass through, and the reflectances of the respective galvano mirrors  32   a ,  32   b ,  42   a , and  42   b  be the same. 
     In the following, a method for manufacturing a lamination molded object by using the lamination molding apparatus will be described. 
     Firstly, as shown in  FIG. 1 , the height of the molding table  5  is adjusted to a suitable position in the state in which the base plate  6  is mounted on the molding table  5 . In this state, the recoater head  11  is moved from the left side of the molding region R to the right side in the direction of the arrow B, and, as shown in  FIG. 8 , the first material layer  8  is formed on the molding table  5 . 
       FIG. 9  is a schematic view illustrating the position relationship between the irradiation device  13  and the molding region R according to the embodiment from a top perspective. The respective galvano mirrors  32   a ,  32   b ,  42   a , and  42   b  are positioned above the substantially central position of the molding region R. In this state, by irradiating the laser beams L 1  and L 2  to a predetermined irradiation region A of the material layer  8 , the material layer  8  is solidified, and a first solidified layer  80   a  is obtained as shown in  FIG. 10 . The irradiation region A is the irradiation range of the laser beams L 1  and L 2  in each divided layer in the molding region R, and is substantially uniform with the region defined by a contour shape of the solidified layer in each divided layer. 
       FIG. 11  is a view that illustrates the paths of the laser beams L 1  and L 2  when a point Q in the irradiation region A of  FIG. 10  is irradiated with the laser beams L 1  and L 2 . A second incident angle θ 2 Q on an incident plane T 2  of the laser beam L 2  irradiated to the point Q by the second galvano scanner  42  is greater than a first incident angle θ 1 Q on an incident plane T 1  of the laser beam L 1  irradiated by the first galvano scanner  32  from a position closer to the point Q to the point Q. Therefore, an irradiation spot R 2 Q of the laser beam L 2  at the point Q is greater than an irradiation spot R 1 Q of the laser beam L 1  at the point Q, and an energy density of the irradiation spot R 2 Q is smaller than an energy density of the irradiation spot R 1 Q. 
     When the difference in shape and energy density between the irradiation spots R 1  and R 2  of the laser beams L 1  and L 2  at the time of irradiating the same position in the molding region R is great, variations in molding quality occur according to the selection of laser beam. In the embodiment, by configuring the first galvano scanner  32  and the second galvano scanner  42  so that the first X-axis galvano mirror  32   a  and the first Y-axis galvano mirror  32   b  and the second X-axis galvano mirror  42   a  and the second Y-axis galvano mirror  42   b  are plane-symmetric to each other, and reducing the distance between the reflected positions of the laser beams L 1  and L 2  on the downstream side, the shapes of the irradiation spots R 1  and R 2  are unified, and the difference in energy density at the time of irradiating the predetermined position is alleviated. 
     In addition, in the embodiment, at the irradiation positions of the molding region R, the absolute value of the difference between the first incident angle θ 1  and the second incident angle θ 2  of the laser beams L 1  and L 2  may be configured as being constantly 7 degrees or less, preferably 3 degrees or less. With such configuration, the shapes of the irradiation spots R 1  and R 2  at the time of irradiating the same position can be substantially uniform, the difference in energy density between the laser beams L 1  and L 2  can be reduced, and the molding quality can be stabilized. 
     In addition, as described above, the irradiable ranges of the first galvano scanner  32  and the second galvano scanner  42  include the entire molding region R. Therefore, regardless of the shape of the molded object or the position of the molded object in the molding region R, the laser beams L 1  and L 2  from the first galvano scanner  32  and the second galvano scanner  42  can be simultaneously irradiated in different positions in the predetermined irradiation region A to increase the molding speed. 
     In the molding region A shown in  FIG. 10  as an example, the irradiation region A is divided into two irradiation regions A 1  and A 2 . The irradiation region A 1  is irradiated by the laser beam L 1 , and the irradiation region A 2  is irradiated by the laser beam L 2 . The irradiation area in the irradiation region A is set as an entire irradiation area S, and the irradiation areas in the irradiation regions A 1  and A 2  are respectively set as a first irradiation area S 1  and a second irradiation area S 2 . By controlling the first galvano scanner  32  and the second galvano scanner  42  by the irradiation controller  30  so that the first irradiation area S 1  and the second irradiation area S 2  are substantially the same, the laser beams L 1  and L 2  can be irradiated efficiently, and the molding speed can be increased. Preferably, the irradiation controller  30  may control the first galvano scanner  32  and the second galvano scanner  42  so that the proportions of the first irradiation area S 1  with respect to the entire irradiation area S and the second irradiation area S 2  with respect to the entire irradiation area S in the predetermined divided layer may be respectively from 40% to 60% inclusive, preferably from 45% to 55% inclusive. Moreover, it is preferable that the divided layers in which the first irradiation area S 1  and the second irradiation area S 2  are substantially the same may be substantially all the divided layers in the desired three-dimensional molded object. Specifically, it is desirable that the first galvano scanner  32  and the second galvano scanner  42  may be controlled so that the first irradiation area S 1  and the second irradiation area S 2  may be substantially the same in 80% or more of the divided layers, more preferably 90% of the divided layers, even more preferably all of the divided layers. 
     After the first solidified layer  80   a  is formed, the height of the molding table  5  is lowered by one layer of the material layer  8 . In this state, the recoater head  11  is moved from the right side of the molding region R to the left side, and a second material layer  8  is formed on the molding table  5  to cover the first solidified layer  80   a . Then, by using the same method, as shown in  FIG. 12 , a second solidified layer  80   b  is obtained by irradiating the laser beams L 1  and L 2  to a predetermined portion in the material layer  8  for solidifying. 
     By repeating the above process, third and later solidified layers are formed. The adjacent solidified layers are firmly fixed to each other. 
     After or during the molding of the three-dimensional molded object, by using a cutting apparatus (not shown) disposed in the chamber  1 , a machining process may be performed on the surface or an undesired portion of a solidified object obtained by laminating the solidified layers. After the lamination molding is completed, by discharging the material powder that is not solidified and cutting chips, the molded object can be obtained. 
     Although the exemplary embodiment of the disclosure has been described above, the disclosure is not limited to the above-described embodiment, and various design changes are possible within the scope of the claims. For example, the disclosure may also be implemented in the following modes. 
     The irradiation device  13  according to the first embodiment includes two galvano scanners consisting of the first galvano scanner  32  and the second galvano scanner  42 . However, the number of the galvano scanners included in the irradiation device is not limited to two. For example, the irradiation device may also be configured as including four galvano scanners. 
       FIG. 13  is a schematic view illustrating the configuration of an irradiation device  113  according to a second embodiment of the disclosure, and illustrates the configuration of a portion of components when the irradiation device  113  is viewed from a top perspective. In such configuration, in addition to the first galvano scanner  32  and the second galvano scanner, which is the same as the configuration of the first embodiment, the irradiation device  113  also include a third galvano scanner  52  and a fourth galvano scanner  62 . 
     The third galvano scanner  52  and the fourth galvano scanner  62  are controlled by the irradiation controller  30  and scan laser beams L 3  and L 4 , respectively. A third laser source not shown herein is connected with a third aperture  53  via a connector  57  disposed on the back surface of a casing  114 . A fourth laser source not shown herein is connected with a fourth aperture  63  via a connector  67  disposed on the back surface of the casing  114 . The laser beams L 3  and L 4  generated by the third light source and the fourth light source respectively pass through the third aperture  53  and the fourth aperture  63 , respectively pass through respective focus control lenses  54   a  and  64   a  of a third focus control unit and a fourth focus control unit and a third adjustment lens  55  and a fourth adjustment lens  65  to be condensed, and are incident to the third galvano scanner  52  and the fourth galvano scanner  62 . In the casing  114 , a control substrate electrically connected with the third galvano scanner  52  and the third focus control unit and a control substrate electrically connected with the fourth galvano scanner  62  and the fourth focus control unit are disposed. The functions and configurations of these components of the irradiation device  113  are the same as the functions and configurations of the components of the irradiation device  13  of the first embodiment. Therefore, details in this regard will be omitted. In addition, these components are integrally disposed in the casing  114 . In other words, the first galvano scanner  32 , the second galvano scanner  42 , the third galvano scanner  52 , and the fourth galvano scanner  62  are accommodated in the single casing  114 . 
     The third galvano scanner  52  includes a third X-axis galvano mirror  52   a  that scans the laser beam L 3  in the X-axis direction, a third X-axis actuator  52   c  that rotates the third X-axis galvano mirror  52   a , a third Y-axis galvano mirror  52   b  that scans the laser beam L 3  in the Y-axis direction, and a third Y-axis actuator  52   d  that rotates the third Y-axis galvano mirror  52   b.    
     The fourth galvano scanner  62  includes a fourth X-axis galvano mirror  62   a  that scans the laser beam L 4  in the X-axis direction, a fourth X-axis actuator  62   c  that rotates the fourth X-axis galvano mirror  62   a , a fourth Y-axis galvano mirror  62   b  that scans the laser beam L 4  in the Y-axis direction, and a fourth Y-axis actuator  62   d  that rotates the fourth Y-axis galvano mirror  62   b.    
     The third galvano scanner  52  and the fourth galvano scanner  62  are configured as being capable of irradiating any position in the molding region R. In other words, the irradiable range of the third galvano scanner  52  and the fourth galvano scanner  62  include the entire molding region R. 
     In addition, the third X-axis galvano mirror  52   a  and the third Y-axis galvano mirror  52   b  of the third galvano scanner  52  and the fourth X-axis galvano mirror  62   a  and the fourth Y-axis galvano mirror  62   b  of the fourth galvano scanner  62  are disposed to be plane-symmetric to each other. The third X-axis galvano mirror  52   a  and the third Y-axis galvano mirror  52   b  of the third galvano scanner  52  and the fourth X-axis galvano mirror  62   a  and the fourth Y-axis galvano mirror  62   b  of the fourth galvano scanner  62  are disposed to be plane-symmetric to each other with respect to the symmetry plane P which is perpendicular to the molding region R, so that a distance between the downstream galvano mirror of the third X-axis galvano mirror  52   a  and the third Y-axis galvano mirror  52   b  of the third galvano scanner  52  (i.e., the third X-axis galvano mirror  52   a  in the embodiment) and the downstream galvano mirror of the fourth X-axis galvano mirror  62   a  and the fourth Y-axis galvano mirror  62   b  of the fourth galvano scanner  62  (i.e., the fourth X-axis galvano mirror  62   a  in the embodiment) is smaller than a distance between the upstream galvano mirror of the third X-axis galvano mirror  52   a  and the third Y-axis galvano mirror  52   b  of the third galvano scanner  52  (i.e., the third Y-axis galvano mirror  52   b  in the embodiment) and the upstream galvano mirror of the fourth X-axis galvano mirror  62   a  and the fourth Y-axis galvano mirror  62   b  of the fourth galvano scanner  62  (i.e., the fourth Y-axis galvano mirror  62   b  in the embodiment). In addition, it is preferably configured so that the reflected positions of the laser beams L 1 , L 2 , L 3  and L 4  of the downstream galvano mirrors of the first galvano scanner  32 , the second galvano scanner  42 , the third galvano scanner  52 , and the fourth galvano scanner  62  are positioned above the substantially central position of the molding region R. 
     The third galvano scanner  52  and the fourth galvano scanner  62  are configured so that the structural relationship therebetween is the same as the structural relationship between the first galvano scanner  32  and the second galvano scanner  42 . That is, for the third galvano scanner  52  and the fourth galvano scanner  62 , it is preferable that a distance between reflected positions of the laser beams L 3  and L 4  on the downstream side in the respective galvano scanners  52  and  62  be shorter. Specifically, it is preferable that the respective galvano scanners  52  and  62  may be disposed so that the distance between the third reflected position of the laser beam L 3  of the downstream galvano mirror of the third X-axis galvano mirror  52   a  and the third Y-axis galvano mirror  52   b  of the third galvano scanner  52  (i.e., the reflected position in the third X-axis galvano mirror  52   a  in the embodiment) and the fourth reflected position of the laser beam L 4  of the downstream galvano mirror of the fourth X-axis galvano mirror  62   a  and the fourth 
     Y-axis galvano mirror  62   b  of the fourth galvano scanner  62  (i.e., the reflected position in the fourth X-axis galvano mirror  62   a  in the embodiment), when the laser beams L 3  and L 4  are irradiated, is preferably constantly 150 mm or less, and more preferably 100 mm or less. 
     In addition, when a third incident angle of the laser beam L 3  on an incident plane at the time when the laser beam L 3  is irradiated to a predetermined position in the molding region R by the third galvano scanner  52  with respect to the vertical direction is set as θ 3 [°], and a fourth incident angle of the laser beam L 4  on an incident plane at the time when the laser beam L 4  is irradiated to a predetermined position in the molding region R by the fourth galvano scanner  42  with respect to the vertical direction is set as θ 4 [°], in order to reduce the difference in shapes of irradiation spots or energy densities, it is desirable that the difference between the third incident angle θ 3  and the fourth incident angle θ 4  be smaller. In the embodiment, the irradiation device  113  is configured so that, at any position in the molding region R, the absolute value of the difference between the third incident angle θ 3  and the fourth incident angle θ 4  at the time when the laser beams L 3  and L 4  are irradiated is constantly 7 degrees or less, and more preferably 3 degrees or less. 
     In the case where a lamination molded object is manufactured by using the lamination molding apparatus according to the second embodiment, by irradiating the laser beams L 1 , L 2 , L 3 , and L 4  to the predetermined irradiation region A of the material layer  8 , the material layer  8  is solidified, and a solidified layer is obtained. By dividing the irradiation region A into four irradiation regions, i.e., irradiation regions A 1 , A 2 , A 3 , and A 4 , the irradiation regions A 1 , A 2 , A 3 , and A 4  are respectively irradiated with the laser beams L 1 , L 2 , L 3 , and L 4 . The irradiation area in the irradiation region A is set as the entire irradiation area S, and the irradiation areas in the irradiation regions A 1 , A 2 , A 3 , and A 4  are respectively set as the first irradiation area S 1 , the second irradiation area S 2 , a third irradiation area S 3 , and a fourth irradiation area S 4 . By controlling the first galvano scanner  32 , the second galvano scanner  42 , the third galvano scanner  52 , and the fourth galvano scanner  62  by the irradiation controller  30  so that the first irradiation area S 1 , the second irradiation area S 2 , the third irradiation area S 3 , and the fourth irradiation area S 4  are substantially the same, the laser beams L 1 , L 2 , L 3 , and L 4  can be irradiated efficiently, and the molding speed can be increased. Preferably, the irradiation controller  30  may control the first galvano scanner  32 , the second galvano scanner  42 , the third galvano scanner  52 , and the fourth galvano scanner  62 , so that the proportions of the first irradiation area S 1 , the second irradiation area S 2 , the third irradiation area S 3 , and the fourth irradiation area S 4  with respect to the entire irradiation area S in the predetermined divided layer may be respectively from 20% to 30% inclusive, and preferably from 22.5% to 27.5% inclusive. Moreover, it is preferable that the divided layers in which the first irradiation area S 1 , the second irradiation area S 2 , the third irradiation area S 3 , and the fourth irradiation area S 4  are substantially the same may be substantially all the divided layers in the desired three-dimensional molded object. Specifically, it is desirable that the first galvano scanner  32 , the second galvano scanner  42 , the third galvano scanner  52 , and the fourth galvano scanner  62  may be controlled so that the first irradiation area S 1 , the second irradiation area S 2 , the third irradiation area S 3 , and the fourth irradiation area S 4  are substantially the same in  80 % or more of the divided layers, more preferably  90 % of the divided layers, and even more preferably all the divided layers. In addition, it is desirable that the laser beam L 1  scanned by the first galvano scanner  32 , the laser beam L 2  scanned by the second galvano scanner  42 , the laser beam L 3  scanned by the third galvano scanner  52 , and the laser beam L 4  scanned by the fourth galvano scanner  32  may pass through the single chamber window la. 
     Even in the second embodiment, the shape difference in the irradiation spots and the energy densities among the laser beams L 1 , L 2 , L 3 , and L 4  can be reduced according to the above configuration, and the molding quality can be stabilized. In addition, since the laser beams L 1 , L 2 , L 3 , and L 4  from the four galvano scanners can be simultaneously irradiated to different positions of the irradiation region, the molding speed can be increased.