Calibrating multiple laser beams for additive manufacturing

1 . A method of aligning a first scanning optic associated with a first irradiation beam and a second scanning optic associated with a second irradiation beam during additive manufacturing of a target object, the method comprising:

irradiating an object area of a layer of a powdered material provided on a building platform with at least one of the first irradiation beam or the second irradiation beam, wherein the object area is associated with a cross-section of the target object;

irradiating a calibration area of the layer of the powdered material with at least one of the first irradiation beam and the second irradiation beam, wherein the calibration area is associated with a cross-section of a calibration object, thereby forming an intermediate top face of the calibration object, wherein the forming of the intermediate top face of the calibration object includes irradiating the calibration area in a plurality of portions, a first portion of the plurality of portions is irradiated by guiding at least one of the first irradiation beam or the second irradiation beam along scan vectors that run parallel to each other in a first orientation or deviate from running parallel by less than 10°;

guiding the first irradiation beam with the first scanning optic over the intermediate top face so as to melt a first calibration pattern having a first geometrical feature into the intermediate top face;

guiding the second irradiation beam with the second scanning optic over the intermediate top face so as to melt a second calibration pattern having a second geometrical feature into the intermediate top face;

directing a first illuminating light beam onto the intermediate top face, wherein an incident direction of the first illuminating light beam has an inclination component in a range from 25° to 80° with respect to a normal direction of the layer of the powdered material and has an azimuthal component in a range from 45° to 90° with respect to the first orientation of the scan vectors of the first portion;

acquiring at least a first image of the intermediate top face including the first calibration pattern and the second calibration pattern while the first illuminating light beam is directed onto the intermediate top face;

using at least the first image, identifying image points related to the first geometrical feature and the second geometrical feature;

from the image points, deriving a spatial offset between positions of the first geometrical feature and the second geometrical feature within the layer of the powdered material; and

aligning at least one of the first scanning optic or the second scanning optic taking into account the spatial offset.

2 . The method of claim 1 , wherein at least one of the plurality of portions is manufactured to have a wave-shaped surface.

3 . The method of claim 1 , wherein the second orientation of the scan vectors of the second portion differ from the first orientation of the scan vectors of the first portion by an angle in a range from 45° to 90°.

4 . The method of claim 1 , wherein

the plurality of portions includes two pairs of opposing portions, each pair of portions is irradiated by guiding at least one of the first irradiation beam and the second irradiation beam along scan vectors, wherein the scan vectors of the two pairs are oriented with respect to each other at an angle in a range from 45° to 90°,

the first calibration pattern includes a pair of straight-line segments that cross in a first reference point defining the first geometrical feature, and each of the straight-line segments extends sufficiently long enough within one of the two pairs of opposing portions that an orientation of a respective straight-line segment is capable of being estimated,

the second calibration pattern includes a pair of straight-line segments that cross in a second reference point defining the second geometrical feature, and each of the straight-line segments extends sufficiently long enough within one of the two pairs of opposing portions of the calibration area that an orientation of a respective straight-line segment is capable of being estimated,

the spatial offset is a difference in positions of the first reference point and the second reference point, and

the straight-line segments are respectively generated by moving the respective irradiation beam along linear scan vectors, wherein orientations of the linear scan vectors of the first calibration pattern are inclined with respect to orientations of the linear scan vectors of the second calibration pattern.

5 . The method of claim 1 , wherein

the plurality of portions includes at least two portions irradiated by guiding at least one of the first irradiation beam and the second irradiation beam along scan vectors, wherein the scan vectors in one of the at least two portions are oriented with respect the scan vectors in another one of the at least two portions at an angle in a range from 45° to 90°, and

the first calibration pattern and the second calibration pattern each include straight-line segments generated by guiding the respective irradiation beam along linear scan vectors, wherein orientations of the linear scan vectors of the first calibration pattern are inclined with respect to orientations of the linear scan vectors of the second calibration pattern, and

the straight-line segments are associated with linear extensions that respectively cross in a first reference point defining the first geometrical feature or a second reference point defining the second geometrical feature, wherein the linear extensions respectively cross for the first calibration pattern and the second calibration pattern.

6 . The method of claim 1 , wherein each of the first calibration pattern and the second calibration pattern includes straight-line segments, the method further comprising:

in the first image, deriving straight lines that extend through images of the straight-line segments and identifying the image points, wherein the image points correspond to crossings of the straight lines, and

deriving the spatial offset from a distance between the first image points in the image.

7 . The method of claim 1 , wherein

aligning the first scanning optic or the second scanning optic includes setting an optical beam path through the first scanning optic or the second scanning optic, or a zero-point associated with the first scanning optic or the second scanning optic, for guiding the first irradiation beam or the second irradiation beam across a powder bed in line with a machine coordinate system; and/or

a first layer associated with the calibration object is attached to the building platform, and the calibration object is positioned at a border region of the building platform, and/or

for a plurality of layers of the powdered material applied for the additive manufacturing of the target object, the first calibration pattern and the second calibration pattern are melted into respective intermediate top faces of the calibration object to repeatedly perform the alignment of the first scanning optic and the second scanning optic throughout the additive manufacturing.

8 . A method of aligning a first scanning optic associated with a first irradiation beam and a second scanning optic associated with a second irradiation beam during additive manufacturing of a target object, the method comprising:

irradiating an object area of a layer of a powdered material provided on a building platform with at least one of the first irradiation beam or the second irradiation beam, wherein the object area is associated with a cross-section of the target object;

irradiating a calibration area of the layer of the powdered material with at least one of the first irradiation beam and the second irradiation beam, wherein the calibration area is associated with a cross-section of a calibration object, thereby forming an intermediate top face of the calibration object, wherein the forming of the intermediate top face of the calibration object includes irradiating the calibration area in a plurality of portions, a first portion of the plurality of portions is irradiated by guiding at least one of the first irradiation beam or the second irradiation beam along scan vectors that run parallel to each other in a first orientation or deviate from running parallel by less than 10°;

guiding the first irradiation beam with the first scanning optic over the intermediate top face so as to melt a first calibration pattern having a first geometrical feature into the intermediate top face;

guiding the second irradiation beam with the second scanning optic over the intermediate top face so as to melt a second calibration pattern having a second geometrical feature into the intermediate top face;

directing a first illuminating light beam onto the intermediate top face, wherein an incident direction of the first illuminating light beam has an azimuthal component in a range from 45° to 90° with respect to the first orientation of the scan vectors of the first portion;

acquiring at least a first image of the intermediate top face including the first calibration pattern and the second calibration pattern while the first illuminating light beam is directed onto the intermediate top face;

using at least the first image, identifying image points related to the first geometrical feature and the second geometrical feature;

from the image points, deriving a spatial offset between positions of the first geometrical feature and the second geometrical feature within the layer of the powdered material; and

aligning at least one of the first scanning optic or the second scanning optic taking into account the spatial offset,

wherein a second portion of the plurality of portions is irradiated by guiding at least one of the first irradiation beam and the second irradiation beam along scan vectors that run parallel to each other in a second orientation or deviate from running parallel by less than 10°, the method further comprising:

directing a second illuminating light beam onto the intermediate top face, wherein an incident direction of the second illumination light beam has an azimuthal component in a range from 45° to 90° with respect to the second orientation,

acquiring a second image of the intermediate top face including the first calibration pattern and the second calibration pattern while the second illuminating light beam is directed onto the intermediate top face, and

generating a superposition of the first image and the second image,

wherein the identifying of the image points related to the first feature and the second feature is performed based on the superposition of the first image and the second image.

9 . A method of aligning a first scanning optic associated with a first irradiation beam and a second scanning optic associated with a second irradiation beam during additive manufacturing of a target object, the method comprising:

irradiating an object area of a layer of a powdered material provided on a building platform with at least one of the first irradiation beam or the second irradiation beam, wherein the object area is associated with a cross-section of the target object;

irradiating a calibration area of the layer of the powdered material with at least one of the first irradiation beam and the second irradiation beam, wherein the calibration area is associated with a cross-section of a calibration object, thereby forming an intermediate top face of the calibration object, wherein the forming of the intermediate top face of the calibration object includes irradiating the calibration area in a plurality of portions, a first portion of the plurality of portions is irradiated by guiding at least one of the first irradiation beam or the second irradiation beam along scan vectors that run parallel to each other in a first orientation or deviate from running parallel by less than 10°;

guiding the first irradiation beam with the first scanning optic over the intermediate top face so as to melt a first calibration pattern having a first geometrical feature into the intermediate top face;

guiding the second irradiation beam with the second scanning optic over the intermediate top face so as to melt a second calibration pattern having a second geometrical feature into the intermediate top face;

directing a first illuminating light beam onto the intermediate top face, wherein an incident direction of the first illuminating light beam has an azimuthal component in a range from 45° to 90° with respect to the first orientation of the scan vectors of the first portion;

acquiring at least a first image of the intermediate top face including the first calibration pattern and the second calibration pattern while the first illuminating light beam is directed onto the intermediate top face;

using at least the first image, identifying image points related to the first geometrical feature and the second geometrical feature;

from the image points, deriving a spatial offset between positions of the first geometrical feature and the second geometrical feature within the layer of the powdered material;

aligning at least one of the first scanning optic or the second scanning optic taking into account the spatial offset, and

for each of the first calibration pattern and the second calibration pattern, melting a plurality of straight-line segments with a flat surface region,

wherein, for each of the first calibration pattern and the second calibration pattern, at least one of the plurality of straight-line segments extends in the first portion and is oriented with respect to the scan vectors used for the first portion with a first intersecting angle in a range from 45° to 90°.

10 . The method of claim 8 , further comprising, for each of the first calibration pattern and the second calibration pattern, melting a plurality of straight-line segments with a flat surface region, wherein, for each of the first calibration pattern and the second calibration pattern, at least one of the plurality of straight-line segments extends in the first portion and is oriented with respect to the scan vectors used for the first portion with a first intersecting angle in a range from 45° to 90°, and at least one of the plurality of straight-line segments extends in the second portion and is oriented with respect to the scan vectors used for the second portion with a second intersecting angle in a range from 45° to 90°.