Search

CA-3028129-C - TRANSVERSE POWER DISTRIBUTION AND ASSIST GAS CONTROL

CA3028129CCA 3028129 CCA3028129 CCA 3028129CCA-3028129-C

Abstract

A method of laser processing of a metallic material comprises the steps of: - providing a laser beam emitting source; - collimating the laser beam along an optical axis of propagation incident on the material; - focusing the collimated laser beam in an area of a working plane of the material; and - conducting said focused laser beam along a working path on the metallic material, wherein the laser beam is shaped: - by reflecting the collimated beam by means of a deformable controlled surface reflecting element having a plurality of independently movable reflection areas, and- by controlling the arrangement of the reflection areas to establish a predetermined transverse power distribution of the beam on at least one working plane of the metallic material as a function of the area of the current working plane and/or of the current direction of the working path on the metallic material.

Inventors

  • Maurizio Sbetti

Assignees

  • ADIGE S.P.A.

Dates

Publication Date
20260505
Application Date
20170706
Priority Date
20160706

Claims (20)

  1. 33 CLAIMS: I. A method of laser processing of a metallic material by means of a focused laser beam having a predetermined transverse power distribution at at least one working plane of the metallic material, comprising the steps of: providing a laser beam emitting source; leading the laser beam emitted by said emitting source along a beam transport optical path to a working head arranged in proximity of said metallic material; collimating the laser beam along an optical axis of propagation incident on the metallic material; focusing said collimated laser beam in an area of said working plane of said metallic material; and conducting said focused laser beam along a working path on the metallic material comprising a succession of working areas, the method comprising shaping the laser beam, wherein shaping the laser beam compnses: reflecting said collimated beam by means of a deformable controlled surface reflecting element having a reflecting surface with a continuous curvature including a plurality of independently movable reflection areas, and controlling the arrangement of said reflection areas to establish a predetermined transverse power distribution of the beam at said at least one working plane of the metallic material as a function of at least one among the area of the current working plane and the current direction of the working path on the metallic material, the method further comprising the steps of: delivering a flow of assist gas towards said area of the working plane of the metallic material along an axis of the assist gas flow, translating the axis of the assist gas flow relatively to the working path on the metallic material, detecting at least one among the current position and the direction of the current translation of the axis of the assist gas flow, automatically controlling the transverse power distribution of the laser beam according to at least one among the detected current position and the detected current translation direction of the axis of the assist gas flow by controlling the arrangement of said reflection areas to establish Date Re9ue/Date Received 2023-12-29 84954252 34 said predetermined transverse power distribution of the beam in an area of the working plane on the metallic material comprised within a delivering area of said assist gas flow.
  2. 2. The method according to claim 1, wherein the automatic control of the transverse power distribution of the laser beam according to at least one among the current position and of the detected current translation direction of the axis of the assist gas flow is performed by reference to a predetermined control pattern or program.
  3. 3. The method according to claim 1 or 2, comprising the step of controlling the arrangement of said reflection areas to establish said transverse power distribution of the beam in said area of said at least one working plane on the metallic material having a Gaussian form with a predetermined diameter.
  4. 4. The method according to claim 1 or 2, comprising the step of controlling the arrangement of said reflection areas to establish said transverse power distribution of the beam in said area of said at least one working plane on the metallic material having an annular shape.
  5. 5. The method according to claim 1 or 2, compnsmg the step of controlling the arrangement of said reflection areas to establish said transverse power distribution of the beam in said area of said at least one working plane on the metallic material having a flat profile shape with a predetermined diameter.
  6. 6. The method according to claim 1 or 2, comprising the step of controlling the arrangement of said reflection areas to establish said transverse power distribution of the beam in said area of said at least one working plane on the metallic material including a Gaussian distribution with a predetermined diameter and an annular distribution externally concentric to the Gaussian distribution.
  7. 7. The method according to claim 1 or 2, comprising the step of controlling the arrangement of said reflection areas to establish said transverse power distribution of the beam in said area of said at least one working plane on the metallic material including a Gaussian distribution with a predetermined diameter and a semi-annular distribution externally concentric to the Gaussian distribution. Date Re9ue/Date Received 2023-12-29 84954252
  8. 8. The method according to claim 7, comprising the orientation of the axis of symmetry of said transverse power distribution of the beam including said Gaussian distribution with said predetermined diameter and said semi-annular distribution externally concentric to the Gaussian distribution in the area of the working plane, depending on the local direction of the working path.
  9. 9. The method according to claim 1 or 2, comprising the step of controlling the arrangement of said reflection areas in order to establish said transverse power distribution of the beam in said area of said at least one working plane on the metallic material having a Gaussian form with an elliptical section.
  10. 10. The method according to claim 9, comprising the orientation of the axis of symmetry of said transverse power distribution of the beam having said Gaussian form with said elliptical section in the area of the working plane, depending on the local direction of the working path.
  11. 11. The method according to claim 1, comprising the relative translation of the axis of the assist gas flow along the working path on the metallic material, the detection of at least one among the current position and the detection of the current direction of translation of the axis of the assist gas flow, and the automatic adjustment of the position optical axis of propagation of the laser beam according to at least one among the detected current position and the detected current direction of translation of the axis of the assist gas flow.
  12. 12. The method according to claim 11, wherein the automatic adjustment of the position of the optical axis of propagation of the laser beam according to at least one among the detected current position and the detected current direction of translation of the axis of the assist gas flow is performed by reference to a predetermined adjustment pattern or program.
  13. 13. The method according to claim 12, comprising the step of controlling the arrangement of said areas of reflection to establish an overall transverse power distribution of the beam in said area of said at least one working plane on the metallic material corresponding to a TEMIO transverse electromagnetic mode, including a combination of two Gaussian distributions with a predetermined diameter transversely aligned with respect to the direction of the working path, Date Re9ue/Date Received 2023-12-29 84954252 36 wherein the relative position of the optical propagation axis and a focusing plane of said two Gaussian distributions varies cyclically over time depending on the local direction of the working path according to a law which includes the combination of the following movements: advancement of a barycenter of an overall power distribution along the local direction of the working path; when projected onto a horizontal plane, movement of the optical axis of each of said two Gaussian distributions according to an elliptical revolving trajectory around a respective predetermined time revolution geometric barycenter, respectively clockwise at the right of the barycenter of the overall power distribution with respect to the progressing direction of working, and counter-clockwise at the left of the barycenter of the overall power distribution with respect to the progressing direction of working; during the time revolution movement around the respective predetermined barycenter, varying the location of the focusing plane of each of said two Gaussian distributions along the respective optical axis of propagation, with retrograde evolution along a parallelogram trajectory in projection on a sagittal plane; progressing of the barycenters of revolution of the optical axis of each of said two Gaussian distributions along directions which are parallel to the direction of movement of the barycenter of the overall power distribution, respectively to the right and to the left thereof.
  14. 14. The method according to claim 13, wherein a cyclic variation of the relative position of the optical axis of propagation of each of said two Gaussian distributions and of the location of the focusing plane of each of said two Gaussian distributions along its respective optical axis of propagation occurs with a frequency that is an integer multiple of v/2D, where vis a progressing speed of the barycenter of the overall power distribution and D is the diameter of the focusing spot of the laser beam in a waist of the laser beam.
  15. 15. The method according to any one of claims 1 to 14, wherein controlling the arrangement of said reflection areas of the controlled surface reflecting element comprises controlling a combination of moves of said areas with respect to a reflecting reference flat surface.
  16. 16. The method according to claim 15, wherein controlling said combination of moves of said reflection areas of the controlled surface reflecting element comprises controlling at least one among a translation movement of said reflection areas along the optical axis of the reflecting Date Re9ue/Date Received 2023-12-29 84954252 37 element and a rotation of said areas to obtain an inclination with respect to the optical axis of the reflecting element.
  17. 17. The method according to any one of claims 1 to 16, compnsmg providing said deformable controlled surface reflecting element having said reflecting surface with said continuous curvature including said plurality of independently movable reflection areas by means of a corresponding plurality of movement modules which include a central area and a plurality of ranks of circular crown sectors concentric to said central area.
  18. 18. The method according to claim 17, wherein said ranks of concentric circular crown sectors are in number of 6, the circular crown sectors are in number of 8 for each rank, and the height of the circular crown sectors is increasing from the first to the third rank and from the fourth to the sixth rank in the radial direction towards the outside of the reflecting element, the height of the circular crown sectors of the fourth rank being intermediate between the height of the circular crown sectors of the first and second rank.
  19. 19. A machine for laser processing of a metallic material by means of a focused laser beam having a predetermined transverse power distribution at at least one working plane of the metallic material, comprising: a laser beam emitting source; means for leading the laser beam emitted by said emitting source along a beam transport optical path to a working head arranged in proximity of said metallic material; optical means for collimating the laser beam along an optical axis of propagation incident on the metallic material; optical means for focusing said collimated laser beam in an area of said working plane of said metallic material, wherein at least said focusing optical means of said collimated laser beam are carried by said working head at a controlled distance from said metallic material; means for adjusting the mutual position between said working head and said metallic material, adapted to conduct said focused laser beam along a working path on the metallic material comprising a succession of working areas, optical means for shaping the laser beam including a deformable controlled surface reflecting element having a reflecting surface with a continuous curvature including a plurality of Date Re9ue/Date Received 2023-12-29 84954252 38 independently movable reflection areas, adapted to reflect said collimated laser beam, the arrangement of said reflection areas being adapted to establish a predetermined transverse power distribution of the beam at said at least one working plane of the metallic material; and electronic processing and control means arranged to control the arrangement of said reflection areas to establish said predetermined transverse power distribution of the beam at said at least one working plane of the metallic material as a function of at least one among the area of the current working plane and the current direction of the working path on the metallic material, the machine further comprising a nozzle adapted to direct a flow of an assist gas toward the working area on the material, and wherein said electronic processing and control means are further arranged to: translate the axis of the assist gas flow relatively to the working path on the metallic material, detect at least one among the current position and the direction of the current translation of the axis of the assist gas flow, and automatically control the transverse power distribution of the laser beam according to at least one among the detected current position and the detected current translation direction of the axis of the assist gas flow.
  20. 20. Computer-readable memory storing a computer-executable program comprising one or more computer-executable code modules that, when executed by electronic processing and control means in a machine for laser processing of a metallic material, cause the machine to perform a method of shaping a laser beam, wherein said machine comprises: optical means for shaping the laser beam including a deformable controlled surf ace reflecting element having a reflecting surface with a continuous curvature including a plurality of independently movable reflection areas, adapted to reflect a collimated laser beam, the arrangement of said reflection areas being adapted to establish a predetermined transverse power distribution of the beam at at least one working plane of the metallic material; and electronic processing and control means arranged to control the arrangement of said reflection areas to establish a predetermined transverse power distribution of the beam at said at least one working plane of the metallic material as a function of at least one among the area of the current working plane and the current direction of the working path on the metallic material, and wherein said method of shaping said laser beam comprises automatically controlling the Date Re9ue/Date Received 2023-12-29 84954252 39 transverse power distribution of the laser beam according to at least one among a detected current position and a detected current translation direction of the axis of an assist gas flow delivered towards the area of the working plane, by controlling the arrangement of said reflection areas to establish said predetermined transverse power distribution of the beam in the area of the working plane on the metallic material comprised within a delivering area of said assist gas flow. Date Re9ue/Date Received 2023-12-29

Description

1 Transverse Power Distribution and Assist Gas Control The present invention relates to the laser processing of a metallic material, more specifically, a laser processing method for cutting, drilling or welding of said material. According to other aspects, the present invention relates to a machine for laser processing of a metallic material arranged to implement the laser processing method, and a computer program comprising one or more code modules for implementing the aforementioned method when the program is executed by electronic processing means. In the following description and the claims, the term "metallic material" is used to define any metallic workpiece such as a sheet or elongated profile having indifferently a closed crosssecti on - for example a hollow circular, rectangular or square form - or an open one - e.g. a flat section or a section in the form of an L, C, U, etc. In industrial metal processing methods, and in particular those of metallic sheets and profiles, the laser is used as a thermal tool for a wide variety of applications that depend on the interaction parameters of the laser beam with the material being processed, specifically on the energy density per incidence volume of the laser beam on the material and on the interaction time interval. For example, by directing a low energy density ( on the order of tens of W per mm2 of surface) for a prolonged time ( on the order of seconds), a hardening process is achieved, while directing a high energy density ( on the order of tens of MW per mm2 of surface) for a time on the order of femtoseconds or picoseconds, a photo-ablation process is achieved. In the intermediate range of increasing energy density and decreasing working time, the control of these parameters enables welding, cutting, drilling, engraving and marking processes to be carried out. Date Re9ue/Date Received 2023-12-29 WO 2018/007967 PCT/1B2017/054067 2 In many processes, including drilling and cutting processes, an assist gas flow must be provided to the working region wherein the interaction between the laser beam and the material occurs which has the mechanical functions of propulsion of the molten material, or the chemical functions of assisting the combustion, or even the technological functions of shielding from the environment surrounding the working region. In the field of laser processing of metallic materials, laser cutting, drilling and welding are processing operations that may be carried out by the same machine, which is adapted to generate a high-powered focused laser beam having a predetermined transverse power distribution on at least one working plane of the metallic material, typically a laser beam with a power density ranging from l to 10000 kW/mm2 , and to govern the beam direction and position of incidence along the material. The difference between the different types of processing that may be performed on a material is substantially ascribable to the power of the laser beam used and the time of interaction between the laser beam and the :material subject to processing. Laser processing machines according to the prior art are shown in figures l and 2. Figure 1 schematically shows an industrial processing machine with a CO2 laser with an optical path of the laser beam in the air, which comprises an emitting source 10, such as a CO2 laser generator device, capable of emitting a single-mode or multi-mode laser beam B, and a plurality of reflective mirrors 12a, 12b, and 12c adapted to conduct the laser beam emitted from the emitting source along a beam transport optical path towards a working head, indicated collectively at 14, arranged in proximity of a material WP. The working head 14 comprises an optical focusing system 16 of the laser beam, generally consisting of a focusing lens, adapted to focus the laser beam along an optical axis of propagation incident on the metallic material. A nozzle 18 is arranged downstream of the focusing lens and is crossed by the laser beam directed towards an area of a working plane of the material. The nozzle is adapted to direct a beam of an assist gas injected by a corresponding system not shown toward the working area on the material. The assist gas is used to control the execution of a working process as well as the quality of the processing obtainable. For example, the assist gas may comprise oxygen, which favors an exothermic WO 2018/007967 PCT/1B2017/054067 3 reaction with the metal, allowing the cutting speeds to be increased, or an inert gas such as nitrogen which does not contribute to the fusion of the material but protects the material from unwanted oxidation at the edges of the working profile, protects the working head from any splashes of molten material and may also be used to cool the sides of the groove produced on the material, confining the expansion of the thermally altered area. Figure 2 shows schematically an industrial processing machine with the laser beam channeled through fiber optics. It compr