Patent Publication Number: US-2019193124-A1

Title: Powder removal

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 14/924,046 filed Oct. 27, 2015, the entire contents of which are incorporated herein by reference. 
    
    
     BACKGROUND 
     1. Field 
     The present disclosure relates to additive manufacturing methods and systems, more specifically to methods and systems for powder removal for additively manufactured articles. 
     2. Description of Related Art 
     Certain methods for additive manufacturing using powder beds (e.g., selective laser sintering) cause powder to be left within internal passages of the additively manufactured article. Traditional methods for removing of such remaining powder can damage internal passages, lead to material weakness in the additively manufactured part, and/or leave excessive amounts of residual powder within the internal passages. The ability to effectively remove powder from certain types and/or sizes of internal features is a limiting design factor for AM articles. 
     Such conventional methods and systems have generally been considered satisfactory for their intended purpose. However, there is still a need in the art for improved powder removal for additively manufactured articles. The present disclosure provides a solution for this need. 
     SUMMARY 
     A method includes issuing a state change fluid into an internal passage of an additively manufactured article and causing the state change fluid to change from a first state having a first viscosity to a second state that is either solid or has a second viscosity that is higher than the first viscosity within the internal passage. The method can also include causing the state change fluid to change back from the second state to the first state and flushing the state change fluid from the internal passage to remove residual powder from the additively manufactured article. 
     The method can include applying vibration, such as ultrasonic vibration, to the additively manufactured article while the state change fluid is in the second state. Causing the state change fluid to change from the first state to the second state can include applying heat to the state change fluid. For example, the state change fluid can include poly(N-isopropylacrylamide) or any other suitable thermal-responsive polymer that becomes more viscous or solidifies with added heat. 
     Causing the state change fluid to change from the first state to the second state can include cooling the state change fluid. For example, the state change fluid can include an ionic liquid that is crystalline at room temperature and melts to freely flow above room temperature. In certain embodiments, the ionic liquid can include [bmim]NTf 2 . In such embodiments, the method can further include heating the ionic liquid to change the ionic liquid from the second state to the first state before inputting the ionic liquid into the internal passage. 
     Causing the state change fluid to change from the first state to the second state can include applying a pressure or force to the state change fluid. For example, the state change fluid can include a non-Newtonian fluid that becomes more viscous or rigid with applied kinetic energy. 
     Inputting the state change fluid can include applying a pressure to the state change fluid. Causing the state change fluid to change from the first state to the second state can include removing the applied pressure or reducing pressure to the state change fluid. For example, the state change fluid can include a non-Newtonian fluid that flows more freely with higher pressure (e.g., a clay suspension). 
     In accordance with at least one aspect of this disclosure, an additively manufactured article includes an internal passage, the internal passages being cleared of residual powder by any suitable portion or combination of portions of a method as described above. 
     These and other features of the systems and methods of the subject disclosure will become more readily apparent to those skilled in the art from the following detailed description taken in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that those skilled in the art to which the subject disclosure appertains will readily understand how to make and use the devices and methods of the subject disclosure without undue experimentation, embodiments thereof will be described in detail herein below with reference to certain figures, wherein: 
         FIG. 1  is a flowchart of an embodiment of a method in accordance with this disclosure; 
         FIG. 2  is a cross-sectional elevation view of an embodiment of an additively manufactured article having an internal flow passage, showing a state change fluid flowing therethrough in a first state; 
         FIG. 3A  is a cross-sectional elevation view of an the additively manufactured article of  FIG. 2 , showing the state change fluid converted to a substantially solid form in an embodiment of a second state in accordance with this disclosure; and 
         FIG. 3B  is a cross-sectional elevation view of an the additively manufactured article of  FIG. 2 , showing the state change fluid converted to a more viscous state in another embodiment of a second state in accordance with this disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made to the drawings wherein like reference numerals identify similar structural features or aspects of the subject disclosure. For purposes of explanation and illustration, and not limitation, an illustrative view of an embodiment of a method in accordance with the disclosure is shown in  FIG. 1  and is designated generally by reference character  100 . Other embodiments and/or aspects of this disclosure are shown in  FIGS. 2-3B . The systems and methods described herein can be used to remove residual powder from within internal passages of additively manufactured articles, for example. 
     Referring to  FIGS. 1 and 2-3B , a method  100  includes inputting (e.g., at block  101 ) a state change fluid  205  into an internal passage  201  of an additively manufactured article  200 . The method  100  also includes causing (e.g., at block  103 ) the state change fluid  205  to change from a first state having a first viscosity (e.g., as shown in  FIG. 2 ) to a second state that is either solid (e.g., as shown  FIG. 3A ) or has a second viscosity that is higher than the first viscosity (e.g., as shown in  FIG. 3B ) while the state change fluid  205  is within the internal passage  201 . 
     The method  100  can also include causing (e.g., at block  105 ) the state change fluid  205  to change back from the second state (e.g.,  FIG. 3A  and/or  FIG. 3B ) to the first state (e.g.,  FIG. 2 ). After converting back to the first state, the method  100  can include flushing (e.g., at block  107 ) the state change  205  fluid from the internal passage  201  to remove residual powder from the additively manufactured article  200 . 
     Referring to  FIGS. 3A and 3B , the method  100  can include applying vibration  307  to the additively manufactured article  200  while the state change fluid  205  is in the second state. In certain embodiments, the vibration can be ultrasonic vibration. Any other suitable mode of vibration is contemplated herein and any type of transducer for vibration can be used to vibrate the additively manufactured article  200  and/or the state change fluid  205  within the internal passage  201 . 
     In certain embodiments, causing the state change fluid  205  to change from the first state to the second state can include applying heat to the state change fluid  205 . For example, the state change  205  fluid can include poly(N-isopropylacrylamide) or any other suitable thermal-responsive polymer that becomes more viscous and/or solidifies with added heat. 
     Causing the state change fluid to change  205  from the first state to the second state can include cooling the state change fluid  205 . For example, the state change fluid  205  can include an ionic liquid that is crystalline at room temperature and melts to freely flow above room temperature. In certain embodiments, the ionic liquid can include [bmim]NTf 2 . In such embodiments, the method  100  can further include heating the ionic liquid to change the ionic liquid from the second state to the first state before inputting the ionic liquid into the internal passage  201 . 
     In certain embodiments, causing the state change fluid  205  to change from the first state to the second state includes applying a pressure or force to the state change fluid  205 . For example, the state change fluid  205  can include a non-Newtonian fluid that becomes more viscous and/or rigid with applied kinetic energy (e.g., cornstarch in water). 
     In certain embodiments, inputting the state change fluid  205  includes applying a pressure to the state change fluid  205 . Causing the state change fluid  205  to change from the first state to the second state can include removing the applied pressure or reducing pressure to the state change fluid  205 . For example, the state change fluid  205  can include a non-Newtonian fluid that flows more freely with higher pressure (e.g., a clay suspension). 
     In accordance with at least one aspect of this disclosure, an additively manufactured article  200  includes an internal passage  201 , the internal passage  201  being cleared of residual powder by any suitable portion or combination of portions of a method  100  as described above. 
     Embodiments as described above allow for more effective powder removal than traditional methods and systems. Increasing the viscosity of a flushing fluid (e.g., the state change fluid  205 ) can allow the flushing to be more effective. For example, vibrating the article  200  after changing to a more viscous or solid state translates the vibration energy to powder particles that are stuck inside the internal passage. This increase as energy translation improves particle separation from the internal passage, thereby cleaning out the internal passage better without the need for corrosive or abrasive solutions which can comprise the integrity of the article  200 . This also allows for additive manufacturing design freedom not previously attainable with traditional techniques. 
     The methods and of the present disclosure, as described above and shown in the drawings, provide for additively manufactured articles with superior properties including improved residual powder removal from internal passages therein. While the apparatus and methods of the subject disclosure have been shown and described with reference to embodiments, those skilled in the art will readily appreciate that changes and/or modifications may be made thereto without departing from the spirit and scope of the subject disclosure.