Focus Adjustment and Laser Beam Caustic Estimation via Frequency Analysis of Time Traces and 2D Raster Scan Data

Patent metadata

Field	Value
Publication number	US-2021146617-A1
Application number	US-201916689316-A
Country	US
Kind code	A1
Filing date	Nov 20, 2019
Priority date	Nov 20, 2019
Publication date	May 20, 2021
Grant date	—

Abstract

Methods of determining at least one parameter of an irradiation device of an apparatus for additively manufacturing three-dimensional objects may include generating an energy beam and guiding the energy beam across a structured test surface, generating a signal by detecting radiation that is emitted from the test surface, and determining the at least one parameter based on a frequency spectrum of the signal.

First claim

What is claimed is:

1 . A method of determining at least one parameter, in particular an irradiation parameter, of an irradiation device of an apparatus for additively manufacturing three-dimensional objects by means of successive layerwise selective irradiation and consolidation of layers of a build material which can be consolidated by means of an energy beam, the method comprising:
generating an energy beam and guiding the energy beam across a structured test surface; generating a signal by detecting radiation that is emitted, in particular reflected, from the test surface; and determining the at least one parameter based on a frequency spectrum of the signal, in particular based on a Fourier transformation of the signal.

2 . The method of claim 1 , wherein the parameter is or relates to a focus position of the energy beam, in particular a z-position of the energy beam, and/or a caustic of the energy beam for at least one position relative to a build plane.

3 . The method of claim 1 , wherein the focus position is determined based on a frequency spectrum of a time trace of the signal and/or the beam width is determined based on a frequency spectrum of a two-dimensional distribution of the signal, in particular a raster scan of the energy beam.

4 . The method of claim 1 , wherein for determining a minimum beam width the focus position is changed until a maximum bandwidth of the transformed signal is found.

5 . The method of claim 1 , wherein the determination is performed for at least two positions relative to a build plane, in particular two different positions in a build plane.

6 . The method of claim 5 , wherein the determination is performed in at least one part of a build plane in which at least one part of an object, in particular a critical part, is to be built in an additive manufacturing process.

7 . The method of claim 1 , wherein the determination is performed during an additive manufacturing process, wherein a surface of the object and/or a surface of build material is used as test surface.

8 . The method of claim 1 , wherein the test surface is periodically or aperiodically structured, in particular resembling a periodic structure or a random structure, particularly white noise.

9 . The method of claim 1 , wherein a length scale of changes of the structure of the test surface, in particular a change in reflectivity, of the test surface is below a beam width of the energy beam.

10 . The method of claim 1 , wherein a length scale of a beam guiding unit is calibrated based on a spectral distance of two peaks of the frequency spectrum of the signal.

11 . The method of claim 1 , wherein the test surface is sand blasted and/or micro structured, in particular structured via the or an energy beam.

12 . The method of claim 1 , wherein the test surface is a glass surface and/or a metal surface and/or a powder surface.

13 . The method of claim 1 , wherein the energy beam is scanned along a path, in particular a circle or a random path, for generating the signal.

14 . A determination device for determining at least one parameter, in particular an irradiation parameter, of an irradiation device of an apparatus for additively manufacturing three-dimensional objects by means of successive layerwise selective irradiation and consolidation of layers of a build material which can be consolidated by means of an energy beam, wherein the determination device is adapted to:
generate an energy beam and guide the energy beam across a structured test surface; generate a signal by detecting radiation that is emitted, in particular reflected or scattered, from the test surface; and determine the at least one parameter based on the frequency spectrum of the signal, in particular based on a Fourier transformation of the signal.

15 . The determination device of claim 14 , wherein the parameter is or relates to a focus position of the energy beam, in particular a z-position of the energy beam, and/or a caustic of the energy beam for at least one position relative to a build plane.

16 . The determination device of claim 14 , wherein the determination device is configured to determine the focus position based on a frequency spectrum of a time trace of the signal; and/or wherein the determination device is configured to determine the beam width based on a frequency spectrum of a two-dimensional distribution of the signal, in particular a raster scan of the energy beam.

17 . The determination device of claim 14 , wherein for determining a minimum beam width, the determination device is configured to change the focus position until a maximum bandwidth of the transformed signal is found.

18 . The determination device of claim 14 , wherein the determination device is configured to perform the determination for at least two positions relative to a build plane, in particular two different positions in a build plane.

19 . The determination device of claim 18 , wherein the determination device is configured to perform the determination in at least one part of a build plane in which at least one part of an object, in particular a critical part, is to be built in an additive manufacturing process.

20 . An apparatus for additively manufacturing three-dimensional objects by means of successive layerwise selective irradiation and consolidation of layers of a build material which can be consolidated by means of an energy beam, the apparatus comprising the determination device according to claim 14 .

Assignees

• Concept Laser Gmbh

Inventors

• Dicken Christian
• Kleinschmidt Ann-Kathrin
• Klaussner Tim
• Gaerber Bertram

Classifications

• B23K26/03 Primary

  Observing, e.g. monitoring, the workpiece · CPC title

• B33Y10/00 Primary

  Processes of additive manufacturing · CPC title

• B22F12/90

  Means for process control, e.g. cameras or sensors · CPC title

• B22F10/80

  Data acquisition or data processing · CPC title

• B22F10/366

  Scanning parameters, e.g. hatch distance or scanning strategy · CPC title