Patent Publication Number: US-9889450-B2

Title: Powder classification system and method

Description:
BACKGROUND 
     The present invention relates generally to the field of additive manufacturing and, in particular, to pretreatment and classification of powders used in additive manufacturing processes. 
     Additive manufacturing is an established but growing technology. In its broadest definition, additive manufacturing is any layerwise construction of articles from thin layers of feed material. Additive manufacturing may involve applying liquid, layer, or particle material to a workstage, then sintering, curing, melting, and/or cutting to create a layer. The process is repeated up to several thousand times to construct the desired field finished component or article. 
     SUMMARY 
     A powder classification apparatus includes a first chamber that includes a fluidized bed and has an inlet and an outlet, the inlet configured to receive a gas and distribute the gas in a uniform flow through the first chamber, the first chamber configured to receive a powder and the gas and create a fluidization zone, the outlet configured to allow at least a portion of the powder to exit the first chamber; and a second chamber having a powder inlet configured to accept at least a portion of the powder from the outlet in the first chamber caused by at least a portion of the powder being ejected from the first chamber by the gas. 
     A method of classifying a powder includes introducing a powder into a fluidized bed, the fluidized bed having an inlet and an outlet; flowing a gas into the fluidized bed through the inlet to form a uniform flow across the surface area of the fluidized bed causing the powder to become suspended in the gas; and collecting a specific size, shape, or density of the powder that is ejected from the fluidized bed by the gas. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-section view of a first embodiment of a powder classification apparatus. 
         FIG. 2  is a cross-section view of a second embodiment of a powder classification apparatus. 
         FIG. 3  is a cross-section view of a third embodiment of a powder classification apparatus. 
     
    
    
     DETAILED DESCRIPTION 
     Often times, it is necessary to clarify or sort raw powder into various sizes, shapes, and/or densities before it is used in an additive manufacturing process. A finished component or article may be more precisely constructed if the powder used at a particular stage is consistent in size, shape. and/or density. Additionally, it may be easier to pretreat the powder if the powder is first classified into groups of similar size, shape and/or density. 
       FIG. 1  is a cross-section view of a first embodiment of a powder classification apparatus. Powder classification apparatus  10  includes first chamber  12 , which also may be called a fluidized bed, and second chamber  14 . First chamber  12  includes gas inlet  16 , powder outlet  18 , and flow regulator  20 . Second chamber  14  includes powder inlet  24 , collection zone  26 , and powder collector  28 . Within powder classification apparatus  10  may also be powder P and gas G. Powder classification apparatus  10  may also include gas outlet  30  and heat treatment device  32 . 
     One purpose of powder classification apparatus  10  is to classify (or sort) powder P, which is within first chamber  12  when the classification process begins. Powder P includes particles of various sizes, shapes, and/or densities. As the classification process progresses, powder P is classified such that the smaller and/or less dense particles (designated P′) with lower drag coefficients are ejected from first chamber  12  and the larger and/or more dense particles (designated P) with higher drag coefficients remain within first chamber  12  (when discussing the powder in general or the powder within first chamber  12 , the designation P will be used; when discussing the smaller and/or less dense particles with lower drag coefficients that were ejected from first chamber  12 , the designation P′ will be used). 
     First chamber  12  is a fluidized bed that may be cylindrical or another shape that allows for a uniform gas flow upward through first chamber  12 . At the bottom of first chamber  12  is gas inlet  16 , which introduces gas G into first chamber  12 . Adjacent to gas inlet  16  is flow regulator  20 , which turns gas G that is introduced into first chamber  12  by gas inlet  16  into a uniform gas flow across the surface area of first chamber  12 . The uniform gas flow created by flow regulator  20  flows upward through first chamber  12 , causing powder P within first chamber  12  to become suspended. At the top of first chamber  12  is powder outlet  18 , which is an opening in first chamber  12  that allows a specific size, shape, and/or density of powder P to exit first chamber  12 . 
     Surrounding first chamber  12  is second chamber  14 , which may be annular or another shape that is able to collect the specific size, shape, and/or density of powder P′ that exits first chamber  12  through powder outlet  18 . Powder inlet  24  is an opening at the top of second chamber  14  and is adjacent to powder outlet  18  of first chamber  12  such that if powder P′ exits first chamber  12  it will flow into second chamber  14 . Within second chamber  14  is collection zone  26 , which is near the bottom of second chamber  14  and is where powder P′ within second chamber  14  accumulates after powder P′ exits first chamber  12 . Adjacent to collection zone  26  is powder collector  28 , which may remove powder P′ from second chamber  14  so powder P′ can go through further pretreatment or be used in the additive manufacturing process. 
     Heat treatment device  32  may extend through the sides of first chamber  12  and second chamber  14  to allow for heat to be introduced into powder classification apparatus  10  for heat treatment of powder P. Additionally, heat treatment device  32  may surround powder classification apparatus  10  such that powder classification apparatus  10  is within a heated atmosphere, which may be a furnace or similar device. Also, heat treatment device  32  may be placed near gas inlet  16  so as to heat gas G before it is introduced into first chamber  12 . Heat treatment device  32  may be a heater or can be another device that heats gas G as it is introduced into powder classification apparatus  10 . At the top of powder classification apparatus  10  is gas outlet  30 , which allows for gas G to exit powder classification apparatus  10  so as to prevent a buildup of pressure within powder classification apparatus  10 . 
     Powder P having various sizes, shapes, and/or densities and desired to be classified for an additive manufacturing process is introduced into first chamber  12 . Powder P may be one material with various sizes and shapes or may be a number of materials having different sizes, shapes, and/or densities. Powder P begins within first chamber  12 , where it is acted upon by the uniform flow of gas G flowing upward through first chamber  12 . Gas G is introduced into first chamber  12  by gas inlet  16 . Gas G may be a number of different gases suitable for acting upon powder P, but may also be a noble gas, such as argon, or a gas selected in order to degas/clean powder P as it comes into contact with powder P through the fluidization process (the process that suspends powder P; the area where the suspension takes place may be called a fluidized bed). After flowing into first chamber  12  through gas inlet  16 , gas G is acted upon by flow regulator  20 . Flow regulator  20  is a gas distributor configured to turn gas G into a uniform flow across the surface area of first chamber  12 . While  FIG. 1  shows flow regulator  20  located at the bottom of first chamber  12 , flow regulator  20  may also be located within gas inlet  16 . Uniform flow upward in first chamber  12  is desired so as to ensure powder P is consistently dispersed through first chamber  12 . The size and/or shape of first chamber  12  may also be altered to create a uniform flow through first chamber  12 . Flow regulator  20  may be a tent, porous plate, cap, or other configuration, but should have openings smaller than the smallest sized particles of powder P so as to prevent flow regulator  20  from becoming clogged by powder P. 
     The uniform flow of gas G through first chamber  12  creates a fluidized bed that suspends powder P within first chamber  12 . The uniform flow of gas G through first chamber  12  will cause the different particles of powder P having different drag coefficients (due to differing size, density, and/or surface areas) to be suspended at different heights within first chamber  12 . Depending on the size, shape (surface area), and/or density of the particles of powder P, some particles of powder P will be suspended near the bottom of first chamber  12 , near the top of first chamber  12 , or ejected from first chamber  12 . The heavier and denser particles of powder P with higher drag coefficients will be more resistance to being lifted by the uniform flow and the closer those particles of powder P will be to the bottom of first chamber  12 . The lighter and less dense particles of powder P with lower drag coefficients will be less resistance to being lifted by the uniform flow and the closer those particles of powder P will be to the top of first chamber  12 . Additionally, the shape of the particles of powder P can also influence where the particle of powder P is suspended, for round particles have less drag (and therefore will be suspended higher in first chamber  12 ) and sharp/jaggedly shaped particles have more drag (and therefore will be suspended lower in first chamber  12 ). 
     Depending on the rate of the uniform flow, the type of gas G used, the size of the particles of powder P, the shape of the particles of powder P, and/or the density of the particles of powder P, powder classification apparatus  10  can be adjusted to selectively eject a specific size, shape, and/or density of the particles of powder P out of first chamber  12  through powder outlet  18 . Powder P would be sorted such that the smaller and/or less dense particles of powder P with lower drag coefficients would be ejected from first chamber  12  (designated by P′) and the larger and/or more dense particles (designated by P) with higher drag coefficients would remain behind in first chamber  12 . Therefore, powder P would be classified into groups depending on its properties, most notably the size, shape, and/or density of the particles of powder P. 
     Powder P′ that is ejected from first chamber  12  flows out through powder outlet  18 . At this point, powder P′ is not acted upon by the uniform flow sufficiently to cause powder P′ to be suspended. In this situation, gravity causes the particles of powder P′ to settle and enter second chamber  14  through powder inlet  24 . Second chamber  14  is adjacent to first chamber  12  and can be a variety of different shapes, including an annular configuration that is radially outward from first chamber  12 . The uniform flow of gas G within first chamber  12  is not present within second chamber  14 , so powder P′ is able to settle to the bottom of second chamber  14  and into collection zone  26 . Collection zone  26  may include powder collector  28 , which collects powder P′ that was ejected from first chamber  12  and settled into collection zone  26 . Powder collector  28  may be a sweeping assembly, suction mechanism, or other device able to remove powder P′ from collection zone  26 . After leaving collection zone  26 , powder P′ may go on to further pretreatment or may be used directly in an additive manufacturing process or another process. 
     Powder P may also be heated by heat treatment device  32  within first chamber  12  or second chamber  14  so as to heat treat powder P without sintering powder P. Heat treatment device  32  may be any device that introduces a desired amount of heat into powder classification apparatus  10  and can be located anywhere throughout powder classification apparatus  10 . As mentioned above, heat treatment device  32  may surround powder classification apparatus  10  or may also be located so as to heat gas G before it is introduced into first chamber  12 . 
     At the top of powder classification apparatus  10  is gas outlet  30 , which is configured to allow gas G introduced into first chamber  12  by gas inlet  16  to escape powder classification apparatus  10 . Gas outlet  30  is positioned to prevent powder P from exiting powder classification apparatus  10  through gas outlet  30 . Because gas G is allowed to escape powder classification apparatus  10  through gas outlet  30 , gas G does not build up within powder classification apparatus  10  and the pressure within powder classification apparatus  10  can be regulated and adjusted. 
     Powder classification apparatus  10 , through the use of a fluidized bed within first chamber  12 , has the ability to sort specific sizes, shapes, and/or densities of particles of powder P, which is advantageous when powder P is intended to be used in an additive manufacturing process that requires a consistent powder having a specific size, density, and/or other properties. Additionally, the use of a suitable gas within powder classification  10  can degas and clean powder P so that the contaminants or inconsistences of powder P are removed before being used. Finally, powder P may be heat treated within powder classification apparatus  10  to give it desired properties suited for its specific use. Therefore, powder classification apparatus  10  can classify and treat powder P so as to prepare it for its intended use in the additive manufacturing process. Powder classification apparatus  10  is flexible enough to be useful in the laboratory to classify and prepare a small portion of powder P or may be enlarged into a commercial process to classify and prepare a large portion of powder P. 
       FIG. 2  is a cross-section view of a second embodiment of a powder classification apparatus. Powder classification apparatus  110  includes first chamber  112 , which also may be called a fluidized bed, and second chamber  114 . First chamber  112  includes gas inlet  116 , powder outlet  118 , and flow regulator  120 . Second chamber  114  includes powder inlet  124  collection zone  126 , and powder collector  128 . Within powder classification apparatus  110  may be powder P. Powder classification apparatus  110  may also include gas outlet  130  and heat treatment device  132 . 
     Powder classification apparatus  110  functions similar to powder classification apparatus  10  of  FIG. 1  in that it uses a fluidization process to classify powder P into specific sizes, shapes, and/or densities (with P′ designating the smaller and/or less dense particles with lower drag coefficients that have been ejected from first chamber  112 ), except that second chamber  114  can be cylindrical or another shape with first chamber  112  surrounding second chamber  114 . First chamber  112  may be a cylinder with second chamber  114  also a cylinder radially within first chamber  114 . Powder classification apparatus  110  has all of the advantageous of the apparatus of  FIG. 1 . Additionally, while powder classification apparatus  110  shows first chamber  112  adjacent to both sides of second chamber  114 , first chamber  112  may be a rectangle or another shape that is adjacent only to one side of second chamber  114 . Also, while second chamber  114  of  FIG. 2  is shown to have a bottom that extends below the bottom of first chamber  112 , similar configurations allow for the bottoms for first chamber  112  and second chamber  114  to be aligned. 
       FIG. 3  is a cross-section view of a third embodiment of a powder classification apparatus. Powder classification apparatus  210  includes first chamber  212  and second chamber  214 , both of which may be fluidized beds. First chamber  212  includes gas inlet  216 A, powder outlet  218 , and flow regulator  220 A. Second chamber  214  includes gas inlet  216 B, flow regulator  220 B, powder inlet  224 , and outlet  230 . Within powder classification apparatus  210  may be powder P and P′ and P″. Powder classification apparatus  210  may also include heat treatment devices  232 A and  232 B. Between first chamber  212  and second chamber  214  is transfer tube  234 . 
     One purpose of powder classification apparatus  210  is to classify powder P, which is within first chamber  212  when the classification process begins. Powder P includes particles of various sizes, shapes, and/or densities having different drag coefficients. As the classification process progresses, powder P is classified such that the smaller and/or less dense particles (designated P′) with lower drag coefficients are ejected from first chamber  112  and the larger and/or more dense particles (designated P) with higher drag coefficients remain within first chamber  112 . As the classification process progresses further, powder P′ in second chamber  214  is classified such that the smallest and/or least dense particles (designated P″) with the lowest drag coefficients are ejected from second chamber  214  (when discussing the powder in general or the powder within first chamber  112 , the designation P will be used; when discussing the smaller and/or less dense particles that were ejected from first chamber  112 , the designation P′ will be used; and when discussing the smallest and/or least dense particles that were ejected from second chamber  114 , the designation P″ will be used). 
     Powder classification apparatus  210  functions similarly to the apparatuses of  FIG. 1  and  FIG. 2  in that powder classification apparatus  210  has the ability to classify or sort powder P depending on size, density, and/or other properties of the particles of powder P. 
     First chamber  212  is a fluidized bed that may be cylindrical or another shape that allows for a uniform gas flow upward through first chamber  212 . At bottom of first chamber  212  is gas inlet  216 A, which introduces gas G into first chamber  212 . Adjacent to gas inlet  216 A is flow regulator  220 A, which is a gas distributor that turns gas G that is introduced into first chamber  212  by gas inlet  216 A into a uniform gas flow across the surface area of first chamber  212 . While  FIG. 3  shows flow regulator  220 A located at the bottom of first chamber  212 , flow regulator  220 A may also be located within gas inlet  216 A. The uniform gas flow created by flow regulator  220 A flows upward through first chamber  212 , causing powder P within first chamber  212  to become suspended. At the top of first chamber  212  is powder outlet  218 , which is an opening in first chamber  212  that allows a specific size, shape, and/or density of powder P′ to exit first chamber  212 . While powder outlet  218  does not span the total width of first chamber  212  in  FIG. 3 , powder outlet  218  may be as large as needed to allow for powder P′ to exit first chamber  212 . 
     Connected to powder outlet  218  is transfer tube  234 , which allows powder P′ that has exited first chamber  212  to flow into second chamber  214  through powder inlet  224 . Transfer tube  234  may be any configuration that allows powder P′ to move from first chamber  212  to second chamber  214 . Transfer tube  234  may also transfer gas G within first chamber  212  to second chamber  214 . 
     Second chamber  214  may be a collection zone for powder P′ that has exited first chamber  212  or may be a fluidized bed similar to first chamber  212  that further classifies powder P′ into a larger and/or denser powder P′ and a smaller and/or less dense powder P″. Second chamber  214  may be cylindrical or another shape that allows for a uniform gas flow upward through second chamber  214 . At the bottom of second chamber  214  is gas inlet  216 B, which may introduce gas G′ into second chamber  214 . Adjacent to gas inlet  216 B is flow regulator  220 A, which is a gas distributor that turns gas G′ that is introduced into second chamber  214  by gas inlet  216 B into a uniform gas flow across the surface area of second chamber  214 . While  FIG. 3  shows flow regulator  220 B located at the bottom of second chamber  214 , flow regulator  220 B may also be located within gas inlet  216 B. The uniform gas flow created by flow regulator  220 B flows upward through second chamber  214 , causing powder P′ introduced into second chamber  214  by transfer tube  234  through powder inlet  224  to become suspended. At the top of second chamber  214  is outlet  230 , which is an opening in second chamber  214  that allows gas G to exit when second chamber  214  is not a fluidized bed or allows gas G and G′ and a specific size, shape, and/or density of powder P″ to exit when second chamber  214  is a fluidized bed. Outlet  230  allows for gas G and G′ to exit powder classification apparatus  210  so as to prevent a buildup of pressure within powder classification apparatus  210 . 
     Heat treatment device  232 A and  232 B may be positioned throughout powder classification apparatus  210 , including heat treatment device  232 A that is present within first chamber  212  or heat treatment device  232 B that is present within second chamber  214 . Additionally, heat treatment device  232 A and  232 B may surround powder classification apparatus  210  such that powder classification apparatus  210  is within a heated atmosphere, which may be a furnace or similar device. Also, heat treatment device  232 A may be placed near gas inlet  216 A and/or heat treatment device  232 B may be placed near gas inlet  216 B so as to heat gas G and/or G′ before it is introduced into first chamber  212  and/or second chamber  214 . Heat treatment device  232 A and  232 B may be a heater or can be another device that heats gas G and/or G′ as it is introduced into powder classification apparatus  210 . Heat treatment device  232 A and  232 B could be used to pretreat powder P so as to prepare powder P for the additive manufacturing process. 
     Powder P having various sizes, shapes and/or densities and desired to be classified for an additive manufacturing process is introduced into first chamber  212 . Powder P may be one material with various sizes and shapes or may be a number of materials having different sizes, shapes, and/or densities. Powder P begins within first chamber  212 , where it is acted upon by the uniform flow of gas flowing upward through first chamber  212 . Gas G is introduced into first chamber  212  by gas inlet  216 A. Gas G may be a number of different gases suitable for acting upon powder P, but may also be a noble gas, such as argon, or a gas selected in order to degas/clean powder P as it comes into contact with powder P through the classification process. After flowing into first chamber  212  through gas inlet  216 A, gas G is acted upon by flow regulator  220 A. Flow regulator  220 A is configured to turn gas G into a uniform flow across the surface area of first chamber  212 . Uniform flow upward in first chamber  212  is desired so as to ensure powder P is consistently dispersed through first chamber  212 . The size and/or shape of first chamber  212  may also be altered to create a uniform flow through first chamber  212 . Flow regulator  220 A may be a tent, porous plate, cap, or another configuration, but should have openings smaller than the smallest sized particles of powder P so as to prevent flow regulator  220 A from becoming clogged by powder P. 
     The uniform flow of gas G through first chamber  212  creates a fluidized bed that suspends powder P within first chamber  212 . The uniform flow of gas G through first chamber  212  will cause the different particles of powder P having different drag coefficients (due to differing size, density, and/or surface areas) to be suspended at different heights within first chamber  212 . Depending on the size, shape (surface area), and/or density of the particles of powder P, the particles of powder P will be suspended near the bottom of first chamber  212 , near the top of first chamber  212 , or ejected from first chamber  212  through powder outlet  218 . The heavier and denser particles of powder P with higher drag coefficients will be more resistance to being lifted by the uniform flow and the closer the particles of powder P will be to the bottom of first chamber  212 . The lighter and less dense particles of powder P with lower drag coefficients will be less resistance to being lifted by the uniform flow and the closer the particles of powder P will be to the top of first chamber  212 . Additionally, the shape of the particles of powder P can also influence where the particle of powder P is suspended, for round particles have less drag (and therefore will be suspended higher in first chamber  212 ) and sharp/jaggedly shaped particles have more drag (and therefore will be suspended lower in first chamber  212 ). 
     Depending on the rate of the uniform flow, the type of gas G used, the size of the particles of powder P, the shape of the particles of powder P, and/or the density of the particles of powder P, powder classification apparatus  210  can be adjusted to selectively eject a specific size, shape, and/or density of the particles of powder P out of first chamber  212  through outlet  218 . Powder P would be sorted such that the smaller and/or less dense particles (designated by P′) of powder P would be ejected from first chamber  212  and the larger and/or denser particles (designated by P) would remain behind in first chamber  212 . Therefore, powder P would be classified into groups depending on its properties, most notably the size, shape, and/or density of the particles of powder P. 
     Powder P′ that is ejected from first chamber  212  exits through outlet  218  and into transfer tube  234 , where those powder P′ eventually enters second chamber  214 . Gas G flowing through first chamber  212  may also exit first chamber  212  through outlet  218  and flow through transfer tube  234  into second chamber  214 . Because of the configuration of first chamber  212 , the larger and/or denser particles (powder P) with higher drag coefficients remain within first chamber  212  while the smaller and/or less dense particles (powder P′) with lower drag coefficients travel out of first chamber  212  through outlet  218  and into second chamber  214  through transfer tube  234  and powder inlet  224 . 
     When second chamber  214  is used as a collection area for the particles of powder P′ ejected from first chamber  212 , gas G′ is likely not introduced into second chamber  214  through gas inlet  216 B, and powder P′ in second chamber  214  is allowed to settle to the bottom of chamber  214  where it is collected. In this situation, outlet  230  would only act as an outlet that allows gas G from first chamber  212  to escape. 
     When second chamber  214  is a fluidized bed, second chamber  214  functions much like first chamber  212 , except that the classification process of second chamber  214  ejects a smaller sized and/or less dense particles (powder P″) with lower drag coefficients out through outlet  230  than powder P′ that first chamber  212  ejected out through powder outlet  218 . The size, shape, and/or density of the particles of powder P″ that are ejected may depend on the uniform flow (which may be altered by a number of variables, such as the inlet rate, the surface area of second chamber  214 ), the type of gas G′ introduced into second chamber  214  through gas inlet  216 B, and other variables in second chamber  214 . Therefore, the size and/or density of particles of powder P′ that remain in second chamber  214  are between the size and/or density of particles of powder P that remain in first chamber  212  and the size and/or density of particles of powder P″ that are ejected out of second chamber  214  through outlet  230 . Outlet  230  may then be attached to another device that collects the ejected powder P″. Additionally, another embodiment of powder classification apparatus  210  may include the connection of outlet  230  to another transfer tube that leads to a third chamber that functions as a fluidized bed. Such a multi-stage configuration could go on for many chambers so as to classify powder P into a variety of different sizes and/or densities. 
     Powder inlet  224  should be placed and configured to provide for an even distribution of powder P′ across the entire surface area of second chamber  214  and to ensure that gas G coming from first chamber  212  through transfer tube  234  does not affect powder P′ in the second chamber  214  drastically so as to cause larger and/or more dense particles of powder P′ to be ejected from second chamber  214  than desired. 
     Gas G′ introduced into second chamber  214  through gas inlet  216 B may be the same or a different gas than gas G that is introduced into first chamber  212  through gas inlet  216 A. The gases may be chosen to degas/clean powder P so as to prepare powder P for its intended use. A different gas may be used in second chamber  214  than that used in first chamber  212  if desired, such as when powder classification apparatus  210  is used to separate at least two different powders with different shapes and/or densities. In that instance, it may be desired to degas/treat the different powders with different gases. 
     Powder classification apparatus  210  has all of the advantageous of the apparatuses discussed in  FIGS. 1 and 2 . Additionally, powder classification apparatus  210  allows for multiple classifications of powder P into more than two separate sizes and/or densities with different drag coefficients, which would allow for more powder classes while only introducing the powder into one apparatus. Like with the apparatuses of  FIGS. 1 and 2 , powder classification apparatus  210  is flexible enough to be useful in the laboratory to classify and prepare a small portion of powder P or may be enlarged into a commercial process to classify and prepare a large portion of powder P. 
     DISCUSSION OF POSSIBLE EMBODIMENTS 
     The following are non-exclusive descriptions of possible embodiments of the present invention. 
     A. powder classification apparatus may include a first chamber that includes a fluidized bed and has an inlet and an outlet, the inlet configured to receive a gas and distribute the gas in a uniform flow through the first chamber, the first chamber configured to receive a powder and the gas and create a fluidization zone, the outlet configured to allow at least a portion of the powder to exit the first chamber; and a second chamber having a powder inlet configured to accept at least a portion of the powder from the outlet in the first chamber caused by at least a portion of the powder being ejected from the first chamber by the gas. 
     The powder classification apparatus of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations, and/or additional components. 
     A specific size, shape, or density of powder is ejected from the first chamber to the second chamber depending on the rate of flow of the gas into the first chamber, the type of gas used, the size of the particles of powder, the shape of the particles of powder, and/or the density of the particles of powder. 
     The first chamber is cylindrical in shape and the second chamber is radially outward from first chamber. 
     The outlet of the first chamber is adjacent to the powder inlet of the second chamber. 
     The second chamber is cylindrical in shape and the first chamber is radially outward from the second chamber. 
     A gas outlet in one of the first chamber and the second chamber that is configured to allow the gas to exit the powder classification apparatus. 
     The second chamber is a fluidized bed having the powder inlet, a gas inlet, and an outlet, the powder inlet configured to accept at least a portion of the powder from the outlet in the first chamber, the gas inlet configured to receive a second gas and distribute the second gas in a uniform flow through the second chamber, the second chamber configured to receive a powder from the first chamber and the second gas and create a fluidization zone, the outlet configured to allow at least a portion of the powder to exit the second chamber. 
     The first gas and the second gas are the same. 
     The second chamber includes a powder removal device. 
     The powder is heat treated through the addition of heat into the powder classification apparatus. 
     The powder classification assembly may further include a first chamber that includes a fluidized bed, an inlet, and an outlet, the inlet configured to receive a gas and distribute the gas in a uniform flow through the fluidized bed to create a fluidization zone, the fluidized bed configured to receive a powder, the outlet configured to allow at least a portion of the powder to exit the first chamber; and a second chamber having a powder inlet adjacent to the outlet in the first chamber, the powder inlet is configured to accept at least a portion of the powder from the outlet in the first chamber caused by at least a portion of the powder being ejected from the first chamber by the gas. 
     The powder classification apparatus of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations, and/or additional components. 
     The first chamber is cylindrical and radially within the second chamber. 
     The second chamber is cylindrical and radially within the first chamber. 
     The second chamber includes a powder removal device. 
     A plate with holes is used to distribute the gas in the first chamber in a uniform flow through the fluidized bed in the first chamber. 
     The holes in the plate have a smaller diameter than the diameter of the powder. 
     A method of classifying a powder may include introducing a powder into a fluidized bed, the fluidized bed having an inlet and an outlet; flowing a gas into the fluidized bed through the inlet to form a uniform flow across the surface area of the fluidized bed causing the powder to become suspended in the gas; and collecting a specific size, shape, or density of the powder that is ejected from the fluidized bed by the gas. 
     The method of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations, and/or additional components. 
     The fluidized bed includes a gas outlet. 
     The specific size, shape, or density of powder is ejected from the fluidized bed in response to the rate of flow of the gas into the fluidized bed, the type of gas used, the size of the powder, and/or the density of the powder. 
     Introducing heat into the fluidized bed to heat treat the powder. 
     While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.