Abstract:
An improved lamination molding apparatus which can maintain the inert gas environment in the chamber as well as remove the fume swiftly and efficiently away from the optical pathway of the laser beam, is provided.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a lamination molding device. 
         [0003]    2. Background of the Invention 
         [0004]    In a powder sintering/laminating method (laser lithography) of metal using laser beam, a particular smoke known as fume is generated when the metal material powder is irradiated with laser beam for sintering. When the chamber gets filled with fume, the fume may shield the laser beam, and the laser beam with necessary energy may not reach the sintering portion. 
         [0005]    Current laser lithography apparatus (sintering lamination molding apparatus) for molding metal products is generally operated by supplying the material powder in a chamber filled with inert gas (usually nitrogen gas), followed by irradiation of the material powder with the laser beam. 
         [0006]    In order to stably emit the laser beam, it is necessary to maintain the concentration of the inert gas in the chamber at a constant level. Accordingly, constitution is made so as to allow discharge of the contaminated inert gas in the chamber while supplying the clean inert gas. Management of the inert gas in the chamber is basically conducted by the supply/discharge opening arranged at upper left and right sides of the chamber. 
         [0007]    Removal of the fume by supplying and discharging the inert gas for maintaining the environment in the chamber enables to remove the obstacle during irradiation with the laser beam. However, such removal is still insufficient. In particular, when the laser beam is emitted from the upper side of the chamber, even a scarce amount of fume continuously rising towards the lens would contaminate the lens, and may result in termination of the molding process. 
         [0008]    In Patent Literature 1, a gas of a different type or a gas having a different temperature with respect to the inert gas in the chamber is supplied from the upper side of the chamber in order to remove the fume from the optical pathway of the laser beam. 
       PRIOR ART DOCUMENTS 
     Patent Literature 
       [0009]    [Patent Literature 1] JP 2012-224919A 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0010]    However, in a case where the gas of different type with respect to the inert gas in the chamber is supplied as in Patent Literature 1, it becomes difficult to maintain the concentration of the inert gas in the chamber. In addition, in a case where a gas having a different temperature with respect to the inert gas in the chamber is supplied, the temperature in the chamber would change, thereby causing unnecessary displacement of the apparatus or the halfway-molded product. 
         [0011]    The present invention has been made by taking these circumstances into consideration. An object of the present invention is to provide an improved lamination molding apparatus which can maintain the inert gas environment in the chamber as well as remove the fume swiftly and efficiently away from the optical pathway of the laser beam. 
       Means to Solve the Problem 
       [0012]    According to the present invention, a lamination molding apparatus, comprising: a chamber having a molding space covering a desired molding region and being filled with an inert gas of a predetermined concentration; and a fume diffusing section arranged on an upper surface of the chamber; wherein the fume diffusing section comprises: a housing having an opening as small as possible but not obstructing emission of a laser beam, the laser beam used for molding region irradiation; and an inert gas supplying pathway to fill the housing with an inert gas having the same composition as the inert gas filling the chamber; and the inert gas is discharged from the opening to form a streamline flow of the inert gas along an optical pathway of the laser beam, thereby removing a fume away from the optical pathway. 
       Effect of the Invention 
       [0013]    In the present invention, an inert gas having the same composition as the inert gas in the molding space of the chamber is used as the inert gas filled in the housing provided in the fume diffusing section of the chamber. In addition, the inert gas in the housing is discharged from an opening provided on the housing as a streamline flow flowing along the optical pathway of the laser beam. According to such constitution, the inert gas can be removed from the optical pathway of the laser beam by the streamline flow of the inert gas. In addition, the inert gas environment in the molding space can be easily maintained by using inert gas having the same composition as the inert gas in the housing of the fume diffusing section for the inert gas in the molding space. 
         [0014]    Hereinafter, various embodiments of the present invention will be provided. The embodiments provided below can be combined with each other. 
         [0015]    Preferably, the fume diffusing section comprises a diffusing member provided in the housing so as to surround the opening; the diffusing member comprises a plurality of fine pores; and the inert gas supplying pathway is provided in between the housing and the diffusing member, and the inert gas is discharged from the opening through the fine pores. 
         [0016]    Preferably, a temperature of the inert gas in the housing is substantially the same as a temperature of the inert gas in the molding space. 
         [0017]    Further preferably, a lamination molding apparatus, comprising: a chamber having a molding space covering a desired molding region and being filled with an inert gas of a predetermined concentration; a fume diffusing section arranged on an upper surface of the chamber so as to cover a window provided in the chamber; and an inert gas supplying apparatus to supply the inert gas into the chamber; wherein the fume diffusing section comprises: a housing having an opening provided so as to allow transmittance of a laser beam and not obstructing the laser beam, the laser beam being transmitted through the window so as to allow two-dimensional scanning throughout the entirety of the molding region; a diffusing member having a plurality of fine pores provided in the housing so as to surround the opening, the diffusing member thereby forming an inert gas supplying space in between the housing and diffusing member; and an inert gas supplying pathway to fill the housing with a the inert gas having the same composition and having the same temperature as the inert gas to be supplied into the molding space, the inert gas in the inert gas supplying space having a pressure higher than the inert gas in the molding space so as to allow the inert gas pass through the plurality of pores; the inert gas is discharged from the opening in a downward direction, thereby removing a fume away from the optical pathway of the laser beam; and the inert gas supplying apparatus constructed so as to supply the inert gases having the same composition and having the same temperature into the molding space and the inert gas supplying space, is provided. 
         [0018]    Further preferably, the lamination molding apparatus comprises an inert gas supplying system to supply the inert gas into the molding space and the inert gas supplying space respectively from the inert gas supplying apparatus through a divided path, and the temperature of the inert gas supplied into the chamber is the same as the inert gas supplied into the molding space. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    The above further objects, features and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, wherein: 
           [0020]      FIG. 1  is a structural diagram of the lamination molding apparatus according to one embodiment of the present invention. 
           [0021]      FIG. 2  is a perspective view of a powder layer forming apparatus  3 . 
           [0022]      FIG. 3  is a perspective view of the recoater head  11  and elongated members  9   r  and  91 . 
           [0023]      FIG. 4  is a perspective view of the recoater head  11  and the elongated members  9   r  and  91  seen from another angle. 
           [0024]      FIG. 5  is a structural diagram showing the details of the fume diffusing section  17 . 
           [0025]      FIG. 6  is a perspective view of the fume diffusing section  17 . 
           [0026]      FIG. 7  is an explanatory drawing showing the lamination molding method which uses the lamination molding apparatus according to one embodiment of the present invention. 
           [0027]      FIG. 8  is an explanatory drawing showing the lamination molding method which uses the lamination molding apparatus according to one embodiment of the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0028]    Hereinafter, the embodiments of the present invention will be described with reference to the drawings. Here, the characteristic matters shown in the embodiments can be combined with each other. 
         [0029]    As shown in  FIGS. 1 and 2 , the lamination molding apparatus according to one embodiment of the present invention is structured by providing the powder layer forming apparatus  3  in the chamber  1 . The powder layer forming apparatus  3  comprises a base  4  having a molding region R, a recoater head  11  provided on the base  4  and being capable of moving in a horizontal uniaxial direction (direction shown by arrow B), and elongated members  9   r  and  91  provided on both sides of the molding region R along the moving direction of the recoater head  11 . The molding region R is provided with a molding table  5  capable of moving vertically (direction shown by arrow A in  FIG. 1 ). When the lamination molding apparatus is used, the molding plate  7  is arranged on the molding table  5 , and the material powder layer  8  is formed thereon. 
         [0030]    As shown in  FIGS. 3 and 4 , the recoater head  11  comprises a material holding section  11   a,  a material supplying section  11   b  provided on the top surface of the material holding section  11   a,  and a material discharging section  11   c  provided on the bottom surface of the material holding section  11   a  for discharging the material powder contained in the material holding section  11   a.  The material discharging section  11   c  has a slit shape which elongates in the horizontal uniaxial direction (direction shown by arrow C) crossing orthogonally with the moving direction (direction shown by arrow B) of the recoater head  11 . On both sides of the recoater head  11 , squeegee blades  11   fb  and  11   rb  for forming a material powder layer  8  by planarizing the material powder discharged from the material discharging section  11   c  are provided. In addition, on both sides of the recoater head  11 , fume suction sections  11   fs  and  11   rs  for suctioning the fume generated during sintering of the material powder are provided. The fume suction sections  11   fs  and  11   rs  are provided along the horizontal uniaxial direction (direction shown by arrow C) crossing orthogonally with the moving direction (direction shown by arrow B) of the recoater head  11 . The material powder is, for example, metal powder (iron powder for example) having a sphere shape with an average particle diameter of 20 μm. 
         [0031]    The elongated members  9   r  and  91  are provided with openings  9   ra  and  91   a,  respectively. Here, the openings  9   ra  and  91   a  are provided along the moving direction (direction shown by arrow B) of the recoater head  11 . In the present embodiment, the opening  9   ra  is used as the inert gas supplying opening, and the opening  91   a  is used as the inert gas discharging opening. Since the inert gas is supplied from the opening  9   ra  and is discharged from the opening  91   a,  a flow of inert gas can be made in the direction shown by the arrow C on the molding region R. Accordingly, the fume generated in the molding region R can be easily discharged along this flow of the inert gas. Here, in the present specification, “inert gas” is a gas which substantially does not react with the material powder, and nitrogen gas, argon gas, and helium gas can be mentioned for example. Here, the opening  91   a  can be used as the inert gas supplying opening, and the opening  9   ra  can be used as the inert gas discharging opening. 
         [0032]    A laser beam emitter  13  is provided above the chamber  1 . The material powder layer  8  formed in the molding region R is irradiated with the laser beam L emitted from the laser beam emitter  13  which is transmitted through a window  1   a  provided in the chamber  1 . The laser beam emitter  13  need be structured so as to allow two-dimensional scanning of the laser beam L. For example, the laser beam emitter  13  is structured with a laser beam source for generating the laser beam L, and a pair of galvanometer scanner for allowing two-dimensional scanning of the laser beam L in the molding region R. There is no particular limitation to the type of the laser beam L, so long as it can sinter the material powder. For example, CO 2  laser, fiber laser, and YAG laser can be mentioned. The window  1   a  is formed with a material which can transmit the laser beam L. For example, in a case where the laser beam L is a fiber laser or a YAG laser, the window  1   a  can be structured with quartz glass. 
         [0033]    On the upper surface of the chamber  1 , the fume diffusing section  17  is provided so as to cover the window  1   a.  As shown in  FIGS. 5 to 6 , the fume diffusing section is provided with a cylindrical housing  17   a  and a cylindrical diffusing member  17   c  arranged in the housing  17   a.  An inert gas supplying space  17   d  is provided in between the housing  17   a  and the diffusing member  17   c.  Further, on the bottom surface of the housing  17   a,  an opening  17   b  is provided at the inner portion of the diffusing member  17   c.  The diffusing member  17   c  is provided with a plurality of pores  17   e,  and the clean inert gas supplied into the inert gas supplying space  17   d  is filled into a clean space  17   f  through the pores  17   e.  Then, the clean inert gas  27  filled in the clean space  17   f  is discharged towards below the fume diffusing section  17  through the opening  17   b.  The clean inert gas  27  discharged from the opening  17   b  forms a streamline flow along the optical pathway of the laser beam L (nearly coaxially with the optical pathway of the laser beam L), thereby removing the fume  25  from the optical pathway of the laser beam L. According to such structure, even when fume  25  is generated by irradiating the material powder layer  8  with the laser beam L, the fume  25  can be prevented from reaching the window  1   a.  Therefore, the contamination degree of the window  1   a  can be suppressed. Here, it is preferable that the opening  17   b  is formed as small as possible, in order to avoid the fume  25  from entering the clean space  17   f.  Specifically, the opening  17   b  is formed with the minimum size which can avoid the laser beam L from being blocked by the housing  17   a  during the two-dimensional scanning of the laser beam L throughout the entirety of the molding region R. 
         [0034]    Next, the inert gas supplying system to supply the inert gas into the chamber  1  and the fume discharging system to discharge the fume from the chamber  1  are explained. 
         [0035]    The inert gas supplying system to supply the inert gas into the chamber  1  is connected with the inert gas supplying apparatus  15  and the fume collector  19 . The inert gas supplying apparatus  15  has a function to supply the inert gas, and is a gas cylinder containing inert gas, for example. The fume collector  19  comprises duct boxes  21  and  23  provided at its upper stream side and its lower stream side respectively. The gas discharged from the chamber  1  (inert gas containing fume) is sent to the fume collector  19  through the duct box  21 . Then, fume is removed in the fume collector  19 , and the cleaned inert gas is sent to the chamber  1  through the fume duct box  23 . According to such constitution, the inert gas can be recycled. 
         [0036]    As shown in  FIGS. 1 and 3 , the inert gas supplying system is connected with the upper supplying opening  1   b  of the chamber  1 , the inert gas supplying space  17   d  of the fume diffusing section  17 , and the connecting section  9   rb  of the elongated member  9   r.  The inert gas is filled in the molding space  1   d  of the chamber  1  through the upper supplying opening  1   b.  The molding space  1   d  is provided with a temperature sensor and a concentration sensor for the inert gas (both of them not shown), thereby controlling the concentration of the inert gas and the temperature at a prescribed value. In addition, as described above, the inert gas is supplied into the inert gas supplying space  17   d  so as to form a flow of the inert gas flowing from the clean space  17   f  towards the molding space  1   d.  The supply pressure of the inert gas flowing into the inert gas supplying space  17   d  is preferably slightly higher (for example, by 5 to 10%) than the internal pressure of the molding space  1   d,  in order to allow easy forming of the flow flowing from the clean space  17   f  towards the molding space  1   d.  Here, the inert gas is supplied into the tubular elongated member  9   r  through the connecting section  9   rb,  and the inert gas is discharged onto the molding region R through the opening  9   ra.    
         [0037]    In the present embodiment, the inert gas from the fume collector  19  is sent to the upper supplying opening  1   b,  and the inert gas from the inert gas supplying apparatus  15  is sent to the inert gas supplying space  17   d  and the connecting section  9   rb.  Although there is a possibility that the inert gas from the fume collector  19  contains residual fume, the constitution of the present embodiment does not permit the inert gas from the fume collector  19  be supplied into the space which requires especially high cleanliness (clean space  17   f  and the space at the periphery of the molding region R). Accordingly, the effect of the residual fume can be minimized. In addition, since the supply pressure of the inert gas from the inert gas supplying apparatus  15  is kept higher than the supply pressure of the inert gas from the fume collector  19 , the inert gas from the fume collector can be prevented from reaching the clean space  17   f  and the periphery of the molding region R. Accordingly, the effect of the residual fume can be suppressed further efficiently. 
         [0038]    Here, in a case where the inert gas supplied into the inert gas supplying space  17   d  and the inert gas supplied into the upper supplying opening  1   b  are different from each other or have different temperature, the concentration of the inert gas and the temperature in the molding space  1   d  becomes difficult to control. In the present embodiment, the same inert gas from the inert gas supplying system is divided to supply the inert gas supplying space  17   d  and the upper supplying opening  1   b.  Therefore, the type and the temperature of the inert gas discharged from the clean space  17   f  towards the molding space  1   d  and the inert gas in the molding space  1   d  are the same. As a result, the concentration and the temperature of the inert gas in the molding space  1   d  can be managed easily, and the constitution of the inert gas supplying system becomes simple. 
         [0039]    As shown in  FIGS. 1 ,  3 , and  4 , the fume discharging system to discharge the fume from the chamber  1  is connected with the upper discharging opening  1   c  of chamber  1 , the fume suction sections  11   fs  and  11   rs  of the recoater head  11 , and the connecting section  91   b  of the elongated member  91 . Since the inert gas containing the fume in the molding space  1   d  of the chamber  1  is discharged through the upper discharging opening  1   c,  a flow of inert gas flowing from the upper supplying opening  1   b  towards the upper discharging opening  1   c  is formed in the molding space  1   d.  The fume suction sections  11   fs  and  11   rs  of the recoater head  11  can suction the fume generated in the molding region R when the recoater head  11  passes over the molding region R. Since the fume can be suctioned at a position very close to the position where the fume is generated, suction of the fume can be performed swiftly and efficiently. In addition, since the fume is suctioned from the direction orthogonal with the optical pathway of the laser beam L, the fume hardly intervene the laser irradiation. Here, the inert gas containing the fume is introduced into the elongated member  91  through the opening  91   a,  and the inert gas containing the fume is discharged out of the chamber  1  through the connecting section  91   b.  The fume discharging system is connected with the fume collector  19  through the dust box  21 , and the inert gas after removal of the fume by the fume collector  19  is recycled. 
         [0040]    Next, referring to  FIGS. 1 ,  7 , and  8 , the lamination molding method using the lamination molding apparatus will be explained. Here, in  FIGS. 7 and 8 , the inert gas supplying system and the fume discharging system are not shown. 
         [0041]    First, the molding plate  7  is placed on the molding table  5 , and the height of the molding table  5  is adjusted to an appropriate position. In this state, the recoater head  11  with the material holding section  11   a  being filled with the material powder is moved from the left side to the right side of the molding region R, in the direction shown by arrow B in  FIG. 1 . Accordingly, a first layer of the material powder layer  8  is formed on the molding plate  7 . 
         [0042]    Subsequently, predetermined portion of the material powder layer  8  is irradiated with the laser beam L, thereby sintering the portion of the material powder layer  8  being irradiated with the laser beam. Accordingly, the first layer of sintered layer  81   f  is obtained as shown in  FIG. 7 . The fume generated during sintering is mainly suctioned from the fume suction section  11   rs  provided at the back side (left side in  FIG. 7 ) of the recoater head  11 . 
         [0043]    Then, the height of the molding table  5  is declined by the thickness of one layer of the material powder layer  8 . Subsequently, the recoater head  11  is moved from the right side to the left side of the molding region R. Accordingly, a second layer of the material powder layer  8  is formed on the sintered layer  81   f.  The fume is suctioned from the fume suction section  11   rs  during the movement of the recoater head  11 . Here, the suction of the fume is performed at a position very close to the position where the fume is generated, and thus it is especially effective. Here, suction of the fume can be performed with the fume suction sections  11   fs  and  11   rs  located at both sides. In addition, the fume is suctioned also from the opening  91   a.    
         [0044]    Next, predetermined portion of the material powder layer  8  is irradiated with the laser beam L, thereby sintering the portion of the material powder layer  8  being irradiated with the laser beam. Accordingly, the second layer of sintered layer  82   f  is obtained as shown in  FIG. 8 . The fume generated during sintering is mainly suctioned from the fume suction section  11   fs  at the front side (right side in  FIG. 8 ) of the recoater head  11 . 
         [0045]    By repeating these steps, the third layer of sintered layer  83   f,  the fourth layer of sintered layer  84   f,  and the sintered layers thereafter are formed. The adjacent sintered layers are firmly fixed with each other. 
         [0046]    After forming necessary number of sintered layers, the non-sintered material powder is removed to obtain the molded sintered body. The sintered body can be used as a mold for molding resin for example. 
       EXPLANATION OF SYMBOLS 
       [0047]      1 : chamber 
         [0048]      3 : powder layer forming apparatus 
         [0049]      5 : forming table 
         [0050]      8 : material powder layer 
         [0051]      11 : recoater head 
         [0052]      17 : fume diffusing section 
         [0053]    L: laser beam 
         [0054]    Although various exemplary embodiments have been shown and described, the invention is not limited to the embodiments shown. Therefore, the scope of the invention is intended to be limited solely by the scope of the claims that follow.