Patent Publication Number: US-2016236293-A1

Title: Apparatus for metal additive manufacturing and electrical discharge machining

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority of Taiwanese Patent Application No. 104105387, filed on Feb. 16, 2015. 
     FIELD 
     The disclosure relates to an apparatus for metal additive manufacturing and electrical discharge machining. 
     BACKGROUND 
     U.S. Pat. No. 6,657,155 B2 discloses a method of and an apparatus for making a three-dimensional object. To make the three-dimensional object, an optical beam is first irradiated on a metal powder layer to form a sintered layer. Then, a cutting machine is used to directly contact and physically machine the sintered layer to obtain a desired shape. However, metal swarf produced when performing physical machining has a dimension larger than that of the metal powder layer, and may cause the sintered layer to have voids. The metal swarf may also result in formation of burr at an edge of the three-dimensional object. Moreover, the metal swarf may be oxidized by the heat generated during machining, and needs to be sieved and discarded, resulting in increased manufacturing costs. 
     SUMMARY 
     Therefore, an object of the present disclosure is to provide an apparatus that can alleviate at least one of the drawbacks associated with the prior art. 
     According to the present disclosure, an apparatus is for metal additive manufacturing and electrical discharging, and is used to machine a metal powder into a rigid body. 
     The apparatus includes an apparatus frame unit, an additive manufacturing unit, and an electrical discharge machining unit. 
     The apparatus frame unit includes a main frame and a processing lift table. The main frame has a processing surface and a processing space that is recessed from the processing surface. The processing lift table is received in the processing space, and is movable relative to the processing surface in a vertical direction that is perpendicular to the processing surface. 
     The additive manufacturing unit is disposed on the main frame, and includes a powder applying unit and a laser unit. The powder applying unit includes a powder applying member that is used to apply a layer of the metal powder onto the processing lift table, so that the metal powder is flush with the processing surface of the main frame. The laser unit is disposed on the main frame and is used to heat a part of the metal powder that is disposed within an imaginary contour line to form the rigid body having a contour that is defined by the imaginary contour line. 
     The electrical discharge machining unit is disposed on the main frame, is proximate to the additive manufacturing unit, and includes a carrier unit, a powder removing member, and an electrode member. The carrier unit removably holds the electrode member and is movable relative to the main frame. The powder removing member is disposed on the carrier unit. The powder removing member is used to remove a part of the metal powder that is proximate to the imaginary contour line. The electrode member is used to machine the rigid body via electrical discharge. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features and advantages of the present disclosure will become apparent in the following detailed description of the embodiment with reference to the accompanying drawings, of which: 
         FIG. 1  is a schematic view showing an embodiment of an apparatus for metal additive manufacturing and electrical discharge machining according to the present disclosure; 
         FIG. 2  is a schematic view showing a rigid body manufactured by the embodiment, formed from a metal powder, and defined by an imaginary contour line; and 
         FIGS. 3 to 7  illustrate consecutive steps of operating the embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1 and 2 , an embodiment of an apparatus of the present disclosure is for metal additive manufacturing and electrical discharge machining. The apparatus is used to machine a metal powder  10  into a rigid body  100 , and includes an apparatus frame unit  2 , an additive manufacturing unit  3 , and an electrical discharge machining unit  4 . 
     The apparatus frame unit  2  includes a main frame  21 , a processing lift table  22 , and a powder supply lift table  23 . 
     The main frame  21  has a processing surface  211 , a processing space  212 , a powder supply space  213 , and a powder recovery space  214 . The processing space  212  is recessed from the processing surface  211 . The powder supply space  213  and the powder recovery space  214  are respectively disposed at two opposite sides of the processing space  212 , and are recessed from the processing surface  211 . In this embodiment, the main frame  21  is an assembly of an upper frame body  215  and a lower frame body  216 . The processing surface  211 , the processing space  212 , the powder supply space  213 , and the powder recovery space  214  are located at the lower frame body  216 . 
     The processing lift table  22  is received in the processing space  212 , and is movable relative to the processing surface  211  in a vertical direction (L) that is perpendicular to the processing surface  211 . In this embodiment, the processing lift table  22  is connected to a ball screw so as to be movable along a linear track. The movement of the ball screw together with the processing lift table  22  is precisely controlled by a servo motor. The moving mechanism of the processing lift table  22  may alternatively be a linear motor cooperating with an optical scale, a servo motor cooperating with an assembly of rack and pinion, a belt drive assembly, etc., and should not be limited to what are disclosed herein. 
     The powder supply lift table  23  is received in the powder supply space  213  of the main frame  21  for moving the metal powder  10  relative to the processing surface  211 . The moving mechanism of the powder supply lift table  23  is similar to that of the processing lift table  22 , and is therefore not further described for the sake of brevity. 
     The additive manufacturing unit  3  is disposed on the main frame  21 , and includes a powder applying unit  31  and a laser unit  32 . 
     The powder applying unit  31  includes a powder applying member  311  that is used to apply a layer of the metal powder  10  onto the processing lift table  22 , so that the metal powder  10  is flush with the processing surface  211  of the main frame  21 . 
     The laser unit  32  is disposed on the main frame  21  and is used to heat a part of the metal powder  10  that is disposed within an imaginary contour line (C) to form the rigid body  100  having a contour that is defined by the imaginary contour line (C). The laser unit  32  includes a laser emitting member  321  and a reflection member  322 . The laser emitting member  321  is capable of emitting a laser beam, and the reflection member  322  is capable of guiding the laser beam toward the metal powder  10  that is disposed on the processing lift table  22 . 
     Specifically, the processing lift table  22  is movable downwards relative to the processing surface  211  by a desired distance, so as to allow the powder applying member  311  to apply the metal powder  10  onto the processing lift table  22 . Then the laser unit  32  starts to focus the laser beam into the part of the metal powder  10  and begins to heat the part of the metal powder  10 . With said configuration, the rigid body  100  can be formed to have a precisely defined contour and shape. In this embodiment, the distance by which the processing lift table  22  moves downwards ranges from 0.01 mm to 0.50 mm. In certain embodiment, the distance is fixed at 0.05 mm. 
     The electrical discharge machining unit  4  is disposed on the main frame  21 , is proximate to the additive manufacturing unit  3 , and includes a carrier unit  41 , a holder  42 , a holding seat  43 , at least one powder removing member  44 , and at least one electrode member  45 . In this embodiment, the electrical discharge machining unit  4  is disposed immediately proximate to the additive manufacturing unit  3 . 
     The carrier unit  41  removably holds the electrode member  45 , is movable relative to the main frame  21 , and includes a long axis carrier  411 , a short axis carrier  412 , and a lift carrier  413 . The long axis carrier  411  is disposed on the main frame  21  and is movable in a long axis direction that is parallel to the processing surface  211 . The short axis carrier  412  is disposed on the long axis carrier  411  and is movable in a short axis direction that is perpendicular to the long axis direction and parallel to the processing surface  211 . The lift carrier  413  is disposed on the short axis carrier  412  and is movable in the vertical direction (L). The moving mechanisms for moving the long axis carrier  411 , the short axis carrier  412 , and the lift carrier  413  are similar to that of the processing lift table  22  as disclosed hereinabove, and is therefore not further described for the sake of brevity. 
     The holder  42  is disposed on the lift carrier  413  for removably holding the electrode member  45 . 
     The powder removing member  44  is disposed on the carrier unit  41 . In this embodiment, the powder removing member  44  and the holder  42  are disposed on the lift carrier  413  and spaced apart from each other. The holding seat  43  is disposed on the main frame  21 . The electrode member  45  is removably disposed on the holding seat  43 . The powder removing member  44  is used to remove a part of the metal powder  10  that is proximate to the imaginary contour line (C). 
     The electrode member  45  is used to machine the rigid body  100  via electrical discharge. 
     In operation, the holder  42  can be positioned above the holding seat  43 , through the movement of the long axis carrier  411 , the short axis carrier  412 , and the lift carrier  413 , for removably holding the electrode member  45 . When the electrode member  45  is removably disposed on the lift carrier  413 , it is movable relative to the main frame  21  in a selected one of the long axis direction, the short axis direction, and the vertical direction (L). 
     In this embodiment, an external device (e.g., a pump) can provide a negative pressure so that the powder removing member  44  is capable of removing the part of the metal powder  10  proximate to the imaginary contour line (C), thereby avoiding the part of metal powder  10  proximate to the imaginary contour line (C) to be melted and attached to the rigid body  100  during subsequent electrical discharge processing. In this embodiment, the electrode member  45  machines at least a part of the rigid body  100  defined by the imaginary contour line (C). The powder removing member  44  removes an endless elongated part  11  of the metal powder  10 . The endless elongated part  11  has an inner periphery surrounding and adjoining the imaginary contour line (C), and a width not less than 1 mm. In certain embodiments, the endless elongated part  11  has a width ranging from 5 mm to 10 mm. 
     In certain embodiments, the electrode member  45  is in a form of a hollow tube (not shown), and the powder removing member  44  is configured as a center bore formed in the hollow tube and permits air to pass therethrough in two opposite directions to remove the endless elongated part  11  of the metal powder  10  that is proximate to the imaginary contour line (C) by one of a blowing force and a suction force. In certain embodiments, the powder removing member  44  removes the endless elongated part  11  of the metal powder  10  that is proximate to the imaginary contour line (C) by one of a blowing force, a suction force, and a scratch force. In certain embodiments, the metal powder  10  is ferromagnetic, and the powder removing member  44  removes the part of the metal powder  10  that is proximate to the imaginary contour line (C) by a magnetic attractive force. The method for removing the metal powder  10  that is proximate to the imaginary contour line (C) via the powder removing member  44  should not be limited to what are disclosed herein, and may be changed according to practical requirements. It is worth mentioning that the metal powder  10  removed by the powder removing member  44  is not sintered or oxidized by the laser unit  32 , and therefore may be recycled, thereby reducing manufacturing costs. 
     In this embodiment, the number of the powder removing member  44  is one, and the number of the electrode member  45  is three. Therefore, one of the electrode member  45  that has a suitable shape may be selected for different requirements. For example, when machining the contour of the rigid body  100  that is defined by the imaginary contour line (C), the electrode member  45  with a small diameter (e.g., a needle-shaped electrode member) may be used. When machining a surface of the rigid body  100 , the electrode member  45  with a large diameter (e.g., a linear-shaped electrode member) may be used. 
     Referring to  FIGS. 1 and 3 to 7 , a method of operating the apparatus for metal additive manufacturing and electrical discharge machining to manufacture the rigid body  100  is disclosed in the following steps. 
     In a first step, an operator pours the metal powder  10  into the powder supply space  213 , so that a layer of the metal powder  10  is disposed on the powder supply lift table  23 . 
     In a second step, the processing lift table  22  moves downwards relative to the processing surface  211  by the desired distance. In this embodiment, the desired distance may range from 0.01 mm to 0.50 mm or alternatively be fixed at 0.05 mm. 
     In a third step, as shown in the  FIG. 1 , the powder supply lift table  23  moves upwards relative to the processing surface  211  to raise the metal powder  10  to a position higher than the processing surface  211 , followed by applying the metal powder  10  onto the processing lift table  22  so that the metal powder  10  is flush with the processing surface  211 . The remaining metal powder  10  is subsequently collected in the powder recovery space  214 . 
     In a fourth step, as shown in  FIG. 3 , the laser emitting member  321  of the laser unit  32  emits the laser beam, and the reflection member  322  guides the laser beam toward the metal powder  10  to heat the part of metal powder  10  disposed within an imaginary contour line (C), so as to form the rigid body  100 . 
     In a fifth step, as shown in  FIG. 4 , the first to fourth steps may be repeated for five times to form the rigid body  100  with desired shape. It should be noted that the number of repetition times is not limited to five and may be changed according to practical requirements. 
     In a sixth step, as shown in  FIG. 5 , the powder removing member  44  removes the endless elongated part  11  of the metal powder  10  by the distance of at least 1 mm, alternatively by the distance ranging from 5 mm to 10 mm. 
     In an seventh step, as shown in  FIGS. 6 and 7 , the holder  42  moves with the carrier unit  41  to a position above the holding seat  43 , and the electrode member  45  is held by the holder  42 . Then, the electrode member  45  machines a surface or along the imaginary contour line (C) of the rigid body  100 , so that the rigid body  100  can have desired dimensional precision. 
     In a eighth step, the first to seventh steps may be repeated to obtain the rigid body  100  with desired dimension, and then the processing lift table  22  lifts up so that the rigid body  100  can be easily removed from the apparatus. 
     The merits of the apparatus for metal additive manufacturing and electrical discharge machining are summarized below. 
     The electrical discharge machining unit  4  provides better dimensional precision to the rigid body  100 . Moreover, the electrode member  45  of the electrical discharge machining unit  4  provides heat that can evaporate metal burr of the rigid body  100 . 
     The powder removing member  44  is capable of removing the part of the metal powder  10  proximate to the imaginary contour line (C), thereby avoiding the part of metal powder  10  proximate to the imaginary contour line (C) to be melted and attached to the rigid body  100  during subsequent electrical discharge processing. Moreover, the metal powder  10  removed by the powder removing member  44  can be recycled for reuse, thereby reducing manufacturing costs. 
     With the carrier unit  41 , movement action of the processing lift table  22  can be minimized, thereby minimizing jumping out of the metal powder  10  during movement of the processing lift table  22 . 
     The holding seat  43  is provided for the electrode member  45  to be disposed thereon, and the holder  42  can hold the electrode member  45 , thereby providing flexibility in manufacturing process. 
     While the disclosure has been described in connection with what are considered the exemplary embodiment, it is understood that this disclosure is not limited to the disclosed embodiment but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.