Abstract:
A method for forming a part. The method includes: forming a first portion of the part at a first level; forming a second portion of the part at a second level; wherein forming the first and second portions includes exposing the first and second levels to a sintering process and portions of the first and second levels to an electron beam; forming a wire in the passage formed inside the first and second portions by exposing a portion of the passage to the electron beam; applying a signal to the wire to break up sintered material in the passage; and removing the wire.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This invention relates forming elements or parts and, more particularly, to a method of removing power from parts formed by electron beam melting. 
         [0002]    Powder bed fusion (PBF) methods use either a laser or electron beam to melt and fuse material powder together. Electron beam melting (EBM) is a particular example of a PDF method and is a type of additive manufacturing (AM) for metal parts. In particular, it is a powder bed fusion technique process where an electron beam is used to melting metal powder layer by layer in a vacuum to form a product. One unique aspect of EBM additive manufacturing is that non-melted particles, i.e. those particles not utilized in the final part, are sintered together. The sintering process binds the non-melted particles together providing additional mechanical strength during the build process. The sintered particle is very difficult to remove from more complex structures, particularly those that contain internal features such passages or blind holes. Another type of PDF utilizes a laser. Powder is not sintered but complex geometries may still exist that include powder. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0003]    According to one aspect of the invention, a method for forming a part is disclosed. The method includes: forming a first portion of the part at a first level; forming a second portion of the part at a second level; wherein forming the first and second portions includes exposing the first and second levels to a sintering process and portions of the first and second levels to an electron beam; forming a wire in the passage formed inside the first and second portions by exposing a portion of the passage to the electron beam; applying a signal to the wire to break up sintered material in the passage; and removing the wire. 
         [0004]    According to some aspects of the invention, a method for forming a part includes: forming a first portion of the part at a first level; forming a second portion of the part at a second level; wherein the first and second portions are formed by exposing, respectively, by exposing some of the first level and some of the second level to a laser beam; forming a wire in the passage formed inside the first and second portions by exposing a portion of the passage to the laser beam; applying a signal to the wire to break up sintered material in the passage; and removing the wire. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
           [0006]      FIG. 1  is a cut-away side view of a part including powder and a removal wire; 
           [0007]      FIG. 2  is a top view of the part of  FIG. 1  taken along line A-A; 
           [0008]      FIG. 3  depicts one example of a passage with multiple wires formed therein; 
           [0009]      FIG. 4  depicts another embodiment of a wire including a cleaning attachment; 
           [0010]      FIG. 5  shows an alternative embodiment that includes multiple wires and cleaning elements in combination; and 
           [0011]      FIG. 6  is a flow chart of one method of removing powder. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0012]    As briefly described above, it is very difficult to remove the dense, sintered powder after completion of the build. Parts with internal features such as passages within a housing have to be specially processed in order to remove dense powder. Powder removal is a step that, for complex parts, will add cost to an additively built part. Embodiments disclosed herein may provide a more efficient or economical solution to removing the dense power. 
         [0013]    The methods disclosed herein may expedite and minimize the amount of time required for powder removal from PBF (including EBM and laser PBF) manufactured parts. In one embodiment, the removal element is formed as a portion of the part itself, used to remove the powder and then discarded. The methods disclosed herein may be especially useful in removing hardened powered in internal surfaces of a part. 
         [0014]      FIG. 1  is an example of part  100  that is formed by PBF shown in a cut-away side view. While the following describes an EBM process, the removal methods are applicable to all PBF created pieces where powder needs to be removed from internal passages. The part  100  includes first and second portions  102 ,  104  separated by an internal passage  106 . As the part  100  is formed, metallic power is first layered down and then sintered. The portions of the part  100  that are to become part of the final product are then exposed to an electron beam to convert the sintered powder to a hard metal object. However, the portions of the part that are not exposed to the electron beam are still sintered, just not fully hardened by the electron beam. 
         [0015]    In the example in  FIG. 1 , the passage  106  may be filled with sintered material  108 . That is, the portions  102 ,  104  are metal pieces formed by exposing the sintered powder to an electron beam to form the fully hardened metal. Portions that are not exposed remain as partially hardened sintered material as illustrated by sintered material  108 . Removal of this material to open, for example, passage  106  may be difficult, especially when the passage is not a straight or varies in size. According to one embodiment, as the part  100  is being formed, a wire  110  is formed through the passage  106 . The wire  110  is formed in the same manner as the portions  102 ,  104 . That is, as each level of the part  100  is formed, a small portion of the otherwise sintered only section (e.g., material  108 ) is exposed to the electron beam to form a continuous wire  110  through it. 
         [0016]      FIG. 2  shows a top view of the part taken along line A-A from  FIG. 1 . The portions  102 ,  104  have been exposed to the electron beam to fully harden them. So too has the wire  110 . Thus, portions  102 ,  104  and wire  110  are in the same state of processing and are fully hardened metal. The passage  106  is shown as including sintered material  108  that has not been exposed to an electron beam. This is the material that needs to be removed in order to allow material to pass through passage  106 . For example, if the part  100  is a manifold, passage  106  would need material  108  removed in order to allow fluids to pass through it. 
         [0017]    With reference to both  FIGS. 1 and 2 , in one embodiment, the wire  110  may be coupled to a transducer  112 . The transducer  112  is an ultrasonic transducer in one embodiment. In one embodiment, the transducer  112  provides an ultrasonic input to the wire  100  which causes the sintered material  110  to more easily be removed. 
         [0018]      FIG. 3  shows an alternative embodiment. Again, a passage  106  is formed that includes sintered material (not shown). Portions of sintered material are exposed to form multiple sinusoidal wires  110   a,    110   b,    110   c.  The number of wires can be varied from 1 to any number and the wires can be either straight or sinusoidal. Using sinusoidal wire shapes may allow for more ultrasonic energy from the transducer  112  to be contact the sintered material in the passage  106 . Further, as the wires  110  are pulled out (for example, in direction C) the increased surface area of additional wires may remove more powder. 
         [0019]      FIG. 4  shows yet another embodiment. In this embodiment, the passage  106  is formed to include wire  110  a cleaning element  120 . The cleaning element  120  is formed of the same material as the wire in one embodiment. As the wire  100  is removed (direction C) the cleaning element  120  may aid in powder removal. The particular shape of the cleaning element  120  may be varied from that shown in  FIG. 4 . Also, more cleaning elements  120  may be provided. In general, the cleaning element  120  has a larger cross-section than the wire  110 . In another embodiment, one or more optional additional cleaning elements  140  may be added to the wire  110 . One or more of the additional elements  140  may be of a different size or shape than cleaning element  120 . 
         [0020]    In yet another embodiment, nested cleaning elements  220  may be provided. Each element (e.g.,  220   a,    220   b ) may be attached to an individual wire  110   a,    110   b,  respectively. As illustrated, a first cleaning element  220   a  is attached to a first wire  110   a  and a second cleaning element  220   b  is attached to a second cleaning element  220   b.  In this configuration, the first wire  110   a  passes through a hole or other passage way (e.g., notch  240 ) formed in the second cleaning element  220   b.  This allows the second cleaning element  220   b  to be removed before the first cleaning element  220   a.  In this manner, a first amount of powder may be removed and then a second amount (assuming that the second cleaning element  220   b  is smaller than the first cleaning element  220   a ). In on embodiment, the wires  110   a.    110   b  may run through different channels to allow them both to work in the illustrated channel  106  and then to work in different channels as they are removed. 
         [0021]      FIG. 6  shows a method according to one embodiment. The method includes several optional steps that may or may not be needed depending on the particular wire/cleaning element combination chosen. 
         [0022]    At block  600  a plan for part is received. The plan may, for example, be a representation of the part or it may be CAD model of the part. One or more wires are added to the plan at block  602 . The added wires are added such that they will be formed in an interior passage(s) of the part. At block  604  optional cleaning elements are added to the plan. At block  606  the part, including the wire(s)/optional cleaning element(s), is formed. The part and the wires are formed using electron beam manufacturing as described above. At block  608  a signal is applied to the wires. This signal causes sintered powder to break up or otherwise become easier to remove. The signal is an ultrasonic signal in one embodiment. At block  610  the wire (or wires) is removed. 
         [0023]    While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.