Patent Application
20210016508
This invention relates to additive manufacturing, and more particularly to using powder fluidization for removal of a manufactured object from a build box and for removal of powder from the object.
Powder-based additive manufacturing is referred to as such because the additive manufacturing process uses powder as the medium for building the object of manufacture. Power-based additive manufacturing is also referred to as “powder bed fusion”.
Powder-based additive manufacturing can be used with various powdered materials and its flexibility allows for geometrically complex three-dimensional structures. As with other additive manufacturing processes, the object is first modeled with data, and then computerized equipment then builds the object layer-by-layer. In a powder-based process, the layers are formed by sintering or otherwise fusing powder granules.
Examples of powder-based additive manufacturing are selective laser sintering, with both metals and polymers, and direct metal laser sintering. Selective laser melting does not use sintering for the fusion of powder but rather melts a powder using a high-energy laser. Electron beam melting is another example and manufactures parts by melting metal powder layer by layer with an electron beam.
A characteristic of powder-based additive manufacturing is that that the object is made inside a “build box” containing the powder. The object must be removed from the build box once it is formed and the powder must be removed from the object. Conventionally, this removal process involves removing the build box from the additive manufacturing system, removing the object, then manually separating the powder from the object. Problems with conventional removal processes include but are not limited to wasted powder material, damage to delicate parts, extensive labor expenses, and safety hazards from exposure to loose powder.
A more complete understanding of the present embodiments and advantages thereof may be acquired by referring to the following description taken in conjunction with the accompanying drawings, in which like reference numbers indicate like features, and wherein:
The following description is directed to a removal process suitable for powder-based additive manufacturing. As described in the Background, additive manufacturing builds three-dimensional objects. Once a computer model is designed, the additive manufacturing equipment reads in data and fuses powder to fabricate the object. The fusing process is sometimes referred to as “sintering” although other terminology may be appropriate depending on the particular type of power-based process being used.
Fluidization Build Box with Movable Platform
As further explained in detail below, after a portion of the powder is sintered or otherwise fused to make object 11, the powder not used to manufacture object 11 is fluidized within the build box 10. This facilitates removal of the object 11 from the build box 10 and removal of unfused powder from the object 11.
A platform 12 is moveable vertically within the build box 10. In the embodiment of
The junction between platform 12 and the inner walls of build box 10 need not be sealed. As described below, in some embodiments, some or all of the fluidized powder flows around or through the platform 12 into the portion of build box 10 below platform 12.
The mechanics for moving platform 12 are not explicitly shown, but various actuation means may be used for moving platform 12 up and down within build box 10. In the embodiment of
A platform actuator/controller 14a controls the timing and extent of movement of platform 12. It is assumed that actuator/controller 14a has appropriate hardware and/or software for performing the tasks described herein.
As indicated, a fluid (gas or liquid) is introduced into build box 10 for the purpose of fluidization of unfused powder within build box 10. The type of fluid used for fluidization may vary with different types of powders and desired density of fluidization.
A fluid delivery network (such as is shown in
A fluid delivery controller 15 controls the timing and volume of fluid to be delivered into the build box 10. It is assumed that controller 15 has appropriate hardware and/or software for performing the tasks described herein. A valve 16 may be used to control fluid flow into box 10.
As a result of fluid delivered into build box 10, the unfused powder within build box 10 becomes a fluidized bed of material that behaves like a liquid. This fluidization is caused by the suspension of unfused powder particles. The suspension of the powder particles is caused when the force of fluid introduced into the powder is equal to the powder particles' weight (i.e., buoyancy). The fluid introduction causes particles of a certain density to rise or fall in relation to the buoyancy force, suspending in a state where equilibrium is achieved.
The fluidization of unused powder allows object 11 to be removed easily from build box 10. The removal process is analogous to pulling an object out of a tub of liquid. Alternatively, platform 12 could be raised such that the fluidized powder is displaced out of the top of the build box 10.
Fluid delivery network 31 may be a configuration of pipes or tubes having ports 31a, which allow liquid to enter into the build box 10 for fluidization of powder within build box 10. As indicated, a main delivery line 34 delivers the fluid, which is typically pressurized. The location of ports 31a may vary. For example, ports 31a may be on the upper sides of the pipes (in the direction of the powder above the fluid delivery network) or on their lower sides, or on both sides.
The “fluid delivery network” may have alternative configurations other than pipes or tubes. For example, the fluid delivery network could be a perforated plate, with fluid delivered via the perforations.
In the embodiment of
Regardless of the configuration of the fluid delivery network 31 or 41, agitation or vibration within build box 10 may be used to enhance fluidization. Properly implemented, the agitation or vibration introduces micro air paths within the powder.
Fluidization Build Box with Stationary Platform
In the embodiment of
A feature of all embodiments is that the fluidization may be controlled to produce a desired “buoyancy” of the object 11. As shown in
Fluidizing Build Box Methods
Another use of the fluidization build box (all embodiments) is for introduction of an already manufactured or partially manufactured part for “re-manufacturing”, i.e., for repair or further manufacture. The build box 10 is first filled with a fluidized powder. The object is lowered into build box 10. The fluidization is turned off, and the powder becomes “un-fluidized”. The object is now captured within the previously fluidized powder. At this point, the re-manufacturing proceeds, using the powder-base additive manufacturing process described above.
A further use of the fluidization build box system (all embodiments) is to level the powder or a platform within the build box. To level a platform, powder is fluidized below the platform. The platform will then float atop the fluidized powder and will seek a level position. Similarly, powder within the build box may be fluidized and leveled above the build box. Agitation and/or vibration may be used to assist in the leveling process.
