Patent Application
20220241862
Disclosed embodiments relate generally to electrostatic separation of impurities from a powder. More particularly, disclosed embodiments relate to electrostatic separation of impurities from a powder bed during additive manufacturing processes.
Many additive and other manufacturing processes utilize a supply of material that is processed into the part or parts being manufactured. For example, processes such as 3-D printing, directed energy deposition, material jetting, binder jetting, and powder bed fusion technologies, including but not limited to, direct metal laser sintering, selective laser sintering, selective heat sintering, electron beam melting, direct metal laser melting, and the like, can use supplies of powder or powder-like materials to manufacture various objects and component parts. The powders used may also vary depending upon the process, the part being made, and the like, and can include metal powders, thermoplastics, ceramics, composites, glasses, and the like.
Typically, and especially in the manufacture of aerospace vehicle components, the powders should remain free from impurities during the manufacturing process. It has been found by the present inventors that polymeric foreign material can be introduced into metallic powder from existing powder bed additive manufacturing systems during handling or the build process itself. Existing filtration methods and powder handling procedures typically limit the amount of impurities that get introduced into the fabrication material but prove ineffective in removing all impurities and are ineffective for impurities that are introduced during the fabrication process.
Existing additive manufacturing processes typically have multiple filtration systems integrated into the process to achieve an impurities-free fabrication ecosystem. The most prevalent method of eliminating impurities from the powder is by sieving the powder through a designated mesh screen sized to remove particulates other than the designated size. In other words, current filtration systems only filter by size, not material composition. Thus, impurities of similar size to the designated size, or smaller, are often missed.
Furthermore, most existing filtration systems are external machines outside of the additive manufacturing system and cannot filter material during the fabrication process when it is typically most critical. Other drawbacks, inefficiencies, and issues also exist with current systems and methods.
Accordingly, disclosed embodiments address the above, and other, issues with existing systems and methods. Disclosed embodiments include apparatus for removing impurities from a powder bed, the apparatus including a powder bed containing powder usable in an additive manufacturing process, a recoater arm that traverses the powder bed to distribute the powder, a collector element connected to the recoater arm, and an electrostatic generator electrically connected to impart an electrostatic charge on at least the collector element and cause the impurities in the powder to adhere to the collector element.
Further disclosed embodiments include a collection compartment adjacent to the collector element for collecting the impurities that adhere to the collector element. In still further disclosed embodiments, the apparatus can include a cleaning element that contacts at least a portion of the collector element and removes the impurities that adhere to the collector element and guides the removed impurities into the collection compartment.
In some disclosed embodiments the collector element may be a roller. In other disclosed embodiments, the collector element may be a plate.
In some disclosed embodiments the impurities may be polymer foreign material. In further disclosed embodiments the impurities are electrically non-conducting. In some disclosed embodiments the powder may be a metallic powder.
Also disclosed are methods of removing impurities from a powder in an additive manufacturing process, the methods include depositing a layer of the powder in a powder bed, spreading the powder in the powder bed with a recoater arm, charging a collector element with an electrostatic charge, and moving the charged collector element over the powder in the powder bed to attach the impurities in the powder to an outer surface of the charged collector element.
In further disclosed embodiments the methods include cleaning the impurities from the collector element as the collector element contacts a cleaning element. In still further disclosed embodiments the methods can include depositing the impurities in a collection compartment. In other disclosed embodiments the methods can include discharging the collector element at a predetermined location to release the impurities. In some disclosed embodiments the predetermined location is at an end of the powder bed. In other disclosed embodiments the predetermined location comprises two locations at opposite ends of the powder bed.
In some disclosed embodiments the methods can include moving the charged collector element proximate to an oppositely charged second collector element to remove the impurities from the charged collector element. In embodiments where the impurities are polymer foreign material, the methods can include charging the collector element to an amount sufficient to attach at least some of the polymer foreign material to the collector element.
Also disclosed are systems for additively manufacturing aerospace vehicle components, the systems including a powder additive manufacturing machine that includes a powder bed configured to contain a powder, a recoater arm that traverses the powder bed to distribute the powder, and an electrically non-conductive collector element connected to the recoater arm. The systems further include an electrostatic generator electrically connected to impart an electrostatic charge on at least the non-conductive collector element and cause impurities in the powder to adhere to the non-conductive collector element.
Further disclosed systems include a collection compartment in communication with the non-conductive collector element to collect the impurities that adhere to the non-conductive collector element. In some disclosed embodiments the systems include a cleaning element in contact with a portion of the non-conductive collector element that removes the impurities that adhere to the non-conductive collector element and guides the removed impurities into the collection compartment.
In some disclosed embodiments the non-conductive collector element may be a roller. In other disclosed embodiments the non-conductive collector element may be a plate. In some disclosed embodiments the impurities may be polymer foreign material.
Also disclosed are powder cleaning systems including a collector element configured to traverse a powder supply, and an electrostatic generator electrically connectable to the collector element to impart an electrostatic charge on the collector element and cause impurities in a powder in the powder supply to adhere to the collector element.
Further disclosed embodiments of powder cleaning systems include a cleaning element that contacts at least a portion of the collector element and removes the impurities that adhere to the collector element.
In some disclosed embodiments the collector element may be a roller. In other disclosed embodiments the collector element may be a plate. In some disclosed embodiments the powder in the powder supply may be a metallic powder. Other embodiments are also possible.
While the disclosure is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and will be described in detail herein. However, it should be understood that the disclosure is not intended to be limited to the particular forms disclosed. Rather, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the invention as defined by the appended claims.
As will be apparent to those of ordinary skill in the art having the benefit of this disclosure, the disclose apparatus, systems, and methods have applicability in a wide array of industries, fields and circumstances. Of particular interest are industries, such as the manufacture of aerospace vehicles and their components where tolerances, specifications, and component reliability are highly important. As used herein, aerospace vehicles includes, but is not limited to, commercial aircraft, military aircraft, unmanned aircraft, spacecraft (manned and unmanned), satellites, drones, and the like.
As also shown in FIG.1 additive manufacturing apparatus 100 may include a recoater arm 110 that traverses the powder bed 104 to, among other things, redistribute the powder 106. As shown schematically in
Some embodiments of recoater arm 110 may include a blade 112, or the like, to assist in the powder 106 distribution process.
As also shown in
Powder cleaning system 200 also includes an electrostatic generator 204, which may be any type of electrostatic charge generator such as a Van de Graaf generator, a Wimshurst machine, a Bonetti machine, suitable circuitry for generating an electrostatic charge, or the like. As indicated schematically electrostatic generator 204 is electrically connected to impart a charge (shown schematically as a negative charge in
As would also be understood by persons of ordinary skill in the art having the benefit of this disclosure, the disclosed systems, apparatus, and methods allow impurities 102 to be collected during, or before, a build process and may be collected independent of impurity 102 size. Impurities 102 that are electrically non-conducting, such as polymer foreign material, or the like, may be collected in accordance with disclosed embodiments.
As indicated by direction of travel arrow 1 the recoater arm 310 may move bidirectionally, or in other patterns, across the powder bed 104. Thus, it may be advantageous to include more than one powder cleaning systems 200A, 200B to remove impurities 102 along each direction of travel.
In these embodiments each powder cleaning system 200A, 200B includes a collector element 202A, 202B (shown schematically as rollers rotating in directions indicated by arrows R, R′), an electrostatic generator 204A, 204B, a collection compartment 210A, 210B, and a cleaning element 208A, 208B. Other configurations are also possible.
As discussed with other embodiments collector element 402 (again shown as a roller rotating in the direction of arrow R) is charged by electrostatic generator 404 to remove impurities 102 from the powder bed 104. A cleaning element 408 may be used to remove impurities 102 from the collector element 402 and deposit the impurities 102 into a collection compartment 410.
Embodiments of the methods can also optionally include at 610 cleaning the impurities from the collector element as the collector element contacts a cleaning element (e.g., 208, 408). Embodiments can also optionally include at 612 depositing the impurities in a collection compartment (e.g., 210, 410, 510).
Embodiments of the methods can also optionally include at 614 discharging the collector element at a predetermined location (e.g., 512, 514) to release the impurities. As disclosed herein the predetermined locations may be at the ends of a powder bed, may be more the one location, or the like.
Embodiments of the methods can also optionally include at 616 moving the charged collector element proximate to an oppositely charged second collector element (e.g., 516) to remove the impurities from the charged collector element.
Embodiments of the methods can also optionally include moving the charged collector element proximate to an oppositely charged second collector element (e.g., 516) to remove the impurities from the charged collector element. As disclosed herein for methods where the impurities comprise polymer foreign material the collector element may be charged to an amount sufficient to attach at least some of the polymer foreign material to the collector element. Other methods, sequences of steps, combinations of steps, and the like are also possible.
Although various embodiments have been shown and described, the present disclosure is not so limited and will be understood to include all such modifications and variations are would be apparent to one skilled in the art.
