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1. (WO2019005602) Large Scale High Speed Precision Powder Bed Fusion Additive Manufacturing
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CLAIMS

What is claimed is:

1. A system for powder bed fusion additive manufacturing comprising:

a platen having an additive manufacturing powder material spread thereon;

a plurality of energy beams;

an optical relay system comprising:

fixed and moving optics that maintain focus of the plurality of energy beams at the surface of the additive manufacturing powder material;

beam steering system that actively corrects the flight of the plurality of energy beams;

a rotating polygon mirror that reflects the plurality of energy beams for fast scanning motion; and

post scan relay optics that provide planar focus of the plurality of energy beams at a predetermined portion of the additive manufacturing powder material; and

control electronics that selectively control the motion of the optical system and the power modulation of the individual beams comprising the plurality of energy beams.

2. A method of additive manufacturing comprising:

directing, by fixed and moving optical components, a plurality of energy beams toward a beam steering system;

directing, by a beam steering system comprising optical components, the plurality of energy beams toward a rotating polygon mirror;

reflecting in a scanning motion, by the rotating polygon mirror, the plurality of energy beams ;

directing and focusing, by post scan relay optics, the reflected plurality of energy beams toward a platen having an additive manufacturing powder material spread thereon, wherein the reflected plurality of energy beams scan a region of the additive manufacturing powder material to selectively melt the additive manufacturing powder; and

controlling, by control electronics, power modulation of the individual beams comprising the plurality of energy beams in coordination with the scanning motion forming a build layer of a three dimensional structure and repeating the process on sequential build layers to form a three dimensional structure.

A method for powder bed fusion additive manufacturing for the fabrication of three dimensional structures through a succession of multiple powder bed build layers utilizing a succession of parallel scans of a partem of energy beams where the length and width of the beam pattern are more than 5 times the depth of the powder bed build layers and each build layer consists of a union of parallel channels of melted or sintered volume having lengths corresponding to the distances between structure surfaces as measured in the plane of the build layer in the direction of the scanning motion where the lengths of the channels are not necessarily limited to discrete values, and the combination of the scan speed and the power settings for the beams generate and maintain powder bed surface temperatures between the point of complete melting and the initiation of boiling for the fabrication material during the scan engagement.

A method for powder bed fusion additive manufacturing of claim 3 wherein the lengths of the channels of melted or sintered volumes are limited to discrete values.

A method for powder bed fusion additive manufacturing of claim 3 wherein the parallel channels of melted or sintered volume are generated within the bounds of the potential melt pool which travels across the powder bed in the scan direction with the scanning beam pattern, forming channels and not forming channels by selectively having the power of the beams on or off as they engage the specific locations within the powder bed.

A method for powder bed fusion additive manufacturing of claim 3 wherein the power amplitude of some of the energy beams are modulated in a manner that shifts relative maxima in the surface temperature distribution relative to the boundaries of the melt pool, which may include providing an AC component in the power amplitude that is nominally at a frequency near the quotient of the scan speed and the typical beam spacing and is frequency modulated at a frequency that is a fraction of the quotient of the scan speed and the width of the beam pattern.

A method for powder bed fusion additive manufacturing of claim 5 wherein the fabrication of an individual build layer includes one or more imaging stripes, each of which are characterized by a succession of scans of the pattern of energy beams with each scan being equal in length and parallel to one another and the successive scans offset in at least the direction perpendicular to the scan direction and overlapping to some degree in the direction perpendicular to the scan direction.

8. A method for powder bed fusion additive manufacturing of claim 5 wherein the combination of the scan speed and the power settings for the beams provide a melt pool geometry whose solidification boundary has a slope that varies by less than 0.5 over 60% of its surface area.

9. A method for powder bed fusion additive manufacturing of claim 8 wherein successive scans overlap in a manner where the portion of the melt pool where the slope of the solidification boundary deviated by more than 0.5 is re-melted and re-solidified with a slope that varies by less than 0.5 from the portion of the previous scan that is not re- melted.

10. A method for powder bed fusion additive manufacturing of claim 5 wherein the melting or sintering in parallel channels through parallel scans of the beam pattern is augmented with independently controlled single beam scans which may occur along any path or trajectory within the plane of the build layer.

11. A method for powder bed fusion additive manufacturing for the fabrication of three

dimensional structures through a succession of multiple powder bed build layers utilizing a succession of scans of a pattern of energy beams where the length and width of the beam pattern are more than 5 times the depth of the powder bed build layers, and the combination of the scan speed and the power settings for the beams generate and maintain powder bed surface temperatures between the point of complete melting and the initiation of boiling for the fabrication material during the scan engagement while providing a melt pool geometry whose solidification boundary has a slope that varies by less than 0.5 over 60% of its surface area.

12. An apparatus for powder bed fusion additive manufacturing utilizing a pattern of energy beams where the length and width of the beam pattern are more than 5 times the depth of the powder bed layers, and the beam pattern can be scanned at speeds exceeding 2 m/s.

13. An apparatus of Claim 12 wherein the beam pattern image is constructed in a structure that remains fixed in space and the beam pattern image is optically relayed to the final focal plane at the surface of the powder bed, with the relaying optics capable of moving the beam pattern image in space throughout the final focal plane.

14. An apparatus of Claim 13 wherein the relaying optics include a rotating polygon mirror to provide the scanning motion of the beam partem image.

15. An apparatus of Claim 14 wherein the polygon scanner is mounted on a translation stage that provides motion in one or more directions.

16. An apparatus of Claim 15 wherein a controlled translating reflector in combination with other beam delivery reflectors maintains a focal distance at the final focal plane throughout all motions of the translation stage.

17. An apparatus of Claim 14 wherein an active beam steering system maintains pre-scan location and pointing of the beam pattern image through control of actuated reflectors with detector feedback.

18. An apparatus of Claim 15 wherein the scan length is less than the width of the powder bed and multiple overlapping imaging stripes are used to pattern a layer.

19. An apparatus of Claim 12 wherein the energy beam pattern includes one or more of the beams of a different frequency that can be diverted in the post scan optics to scan across a grating that is over a detector to provide an optical timing signal for coordinating beam modulations with the beam pattern motions.

20. An apparatus of Claim 17 wherein the energy beam pattern includes one or more beams of a different frequency that can be diverted within the active beam steering system and directed to the detectors as the feedback for that system.

21. An apparatus of Claim 12 wherein fiber lasers or fiber coupled lasers are used in the construction of the beam partem image

22. An apparatus of Claim 12 wherein one or more laser diode arrays are used in the

construction of the beam partem image

23. An apparatus of Claim 15 wherein a preheating device such as a radiant lamp is mounted on the translation stage and is directed just ahead of the beam pattern in the process direction

24. An apparatus of Claim 12 wherein the temperature throughout the bulk of the powder bed is controlled utilizing heating and cooling elements included within the structure containing the bed of powder material and the build platen.

25. An apparatus of Claim 14 wherein the powder bed translates in the process direction during imaging.