WO2022132564A1 - Surveillance et optimisation en service de fabrication additive par fusion de lit de poudre laser à l'aide d'une détection d'émission thermo-ionique - Google Patents

Surveillance et optimisation en service de fabrication additive par fusion de lit de poudre laser à l'aide d'une détection d'émission thermo-ionique Download PDF

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Publication number
WO2022132564A1
WO2022132564A1 PCT/US2021/062621 US2021062621W WO2022132564A1 WO 2022132564 A1 WO2022132564 A1 WO 2022132564A1 US 2021062621 W US2021062621 W US 2021062621W WO 2022132564 A1 WO2022132564 A1 WO 2022132564A1
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WIPO (PCT)
Prior art keywords
electronic controller
current flow
powder bed
laser
flow signal
Prior art date
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PCT/US2021/062621
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English (en)
Inventor
Aiden Alexander Martin
Philip James Depond
Original Assignee
Lawrence Livermore National Security, Llc
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Publication date
Priority claimed from US17/127,271 external-priority patent/US20210138551A1/en
Application filed by Lawrence Livermore National Security, Llc filed Critical Lawrence Livermore National Security, Llc
Publication of WO2022132564A1 publication Critical patent/WO2022132564A1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y10/00—Processes of additive manufacturing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
    • B22F10/20—Direct sintering or melting
    • B22F10/28—Powder bed fusion, e.g. selective laser melting [SLM] or electron beam melting [EBM]
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
    • B22F10/30—Process control
    • B22F10/36—Process control of energy beam parameters
    • B22F10/368—Temperature or temperature gradient, e.g. temperature of the melt pool
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F12/00—Apparatus or devices specially adapted for additive manufacturing; Auxiliary means for additive manufacturing; Combinations of additive manufacturing apparatus or devices with other processing apparatus or devices
    • B22F12/90—Means for process control, e.g. cameras or sensors
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y30/00—Apparatus for additive manufacturing; Details thereof or accessories therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y50/00—Data acquisition or data processing for additive manufacturing
    • B33Y50/02—Data acquisition or data processing for additive manufacturing for controlling or regulating additive manufacturing processes

Definitions

  • the present disclosure relates to additive manufacturing systems which make use an optical light source to heat a powder bed material layer and to melt the powder bed, and more particularly to systems and methods which perform in situ monitoring of thermionic emission from a powder bed and substrate surface being acted on by an optical light source, and using information obtained during the monitoring for quality control and/or quality assurance, to enhance or optimize characteristics of a material layer formed as the powder bed is melted and solidifies.
  • AM additive manufacturing
  • process monitoring approaches due to the stochastic nature of defects produced during AM processes, and because the primary applications of AM are in industries with stringent materials requirements.
  • in situ monitoring provides a unique view into the interior of a built part during its construction, which would otherwise be subsequently difficult to access once the manufacture of the part is completed.
  • Process monitoring data collected voxel-by-voxel during a build can provide a so-called “digital thread” for increased confidence in final parts that is fundamentally part of today’s Industry 4.0 paradigm.
  • LPBF Laser Power Bed Fusion
  • the optical diagnostics have been employed in an effort to detect defects as they occur, to reduce cycle time and to improve the fundamental understanding of the process-structure-property relationship of a part made using LPBF.
  • High resolution imaging of the powder bed surface to detect and classify morphological anomalies such as powder spreading flaws and elevated regions has been investigated and show promise in identifying catastrophic errors, provided the right thresholding or ground truths are developed.
  • High speed imaging of laser-powder interactions illustrates the complex dynamics of spatter and the vapor plume, which are dominated by a metal vapor jet caused by recoil pressure, but do not capture surface structure at the part scale.
  • Coaxial process monitoring where the melt pool region is viewed through the process laser, has been implemented as a method to understand the relationship between melt pool dimensions and reflected incandescence intensity to solidified morphology, sub-surface and topographic defects.
  • SD-OCT Spectral-domain Optical Coherence Tomography
  • Still another challenge with existing AM systems is the focusing of a laser beam.
  • This focusing operation has typically been a complex procedure which is performed ex situ before beginning a manufacturing operation using the beam.
  • Even more challenging is the co-alignment of two or more lasers so that the “spot” formed by a second laser is focused to a minimum point size, as well as perfectly, or nearly perfectly, co-aligned with the spot produced by a first laser.
  • the present disclosure relates to a system comprising an electronic controller, an optical light source controlled by the electronic controller to generate a beam having an output power level, and a current measuring subsystem.
  • the current measuring subsystem may be in electrical communication with at least one of a conductive substrate or a powder bed layer deposited on the conductive substrate, and also in communication with the electronic controller.
  • the current measuring subsystem may operate to detect a current flow as at least one of the conductive substrate or the powder bed layer is heated as the beam from the optical light source is scanned, and to generate a current flow signal in accordance with the detected current flow.
  • the electronic controller may be configured to receive the current flow signal and to use the current flow signal to determine when a detected temperature of at least one of the conductive substrate or the powder bed layer is at least one of above or below a desired temperature.
  • an additive manufacturing system which may comprise an electronic controller, a memory for storing predetermined temperature information and a laser controlled by the electronic controller to generate a laser beam having an output power level.
  • a current measuring subsystem may also be included which is electrically in communication with at least one of a conductive substrate and a powder bed layer deposited on the conductive substrate, and also in communication with the electronic controller. The current measuring subsystem may operate to detect a current flow as at least one of the conductive substrate or the powder bed layer is heated as the laser is scanned over at least one of the conductive substrate or the powder bed layer, and to generate a current flow signal in accordance with the detected current flow.
  • the electronic controller may be configured to receive the current flow signal and to control the output power level of the laser to maintain a desired current level which ensures that at least one of the substrate or the powder bed layer is maintained at least at one of a desired temperature level or within a desired temperature range.
  • the present disclosure relates to a method for additively manufacturing a part.
  • the method may comprise using a laser beam to heat at least one of a conductive substrate or a powder bed of particles resting on the conductive substrate.
  • the method may further include using a current measuring subsystem in communication with at least one of the conductive substrate or the powder bed, to measure a current flow produced as a result of thermionic emission as the laser beam is scanned over at least one of the conductive substrate or the powder bed, and heats at least one of the conductive substrate or the powder bed.
  • the method may further include causing the electronic control to use the measured current flow to control an output power level of the laser beam while scanning the laser beam over the powder bed to at least one of eliminate or mitigate, at least one of an over-temperature condition or an under-temperature condition, of at least one of the substrate or the powder bed layer, during the scan.
  • the present disclosure relates to a system for calibrating a laser.
  • the system may comprise an electronic controller, an optical light source and a current measuring subsystem.
  • the optical light source may be controlled by the electronic controller to generate a beam having an output power level, the beam being directed at one of a substrate or a laser meltable powder bed layer disposed on the substrate.
  • the current measuring subsystem is in electrical communication with at least one of a conductive substrate or a powder bed layer deposited on the conductive substrate, and in further communication with the electronic controller.
  • the current measuring subsystem is configured to detect a current flow resulting from thermionic emission of electrons as at least one of the conductive substrate or the powder bed layer is heated by the beam, and to generate a current flow signal in accordance therewith.
  • the electronic controller is configured to receive the current flow signal and to use the current flow signal to focus the beam.
  • FIG. 1 is a high level schematic drawing of one embodiment of the present disclosure showing an additive manufacturing (AM) system in the form of a Laser Powder Bed Fusion (LPBF) system which incorporates an in situ monitoring subsystem;
  • AM additive manufacturing
  • LPBF Laser Powder Bed Fusion
  • Figure 2 is a flowchart illustrating various operations that may be performed by the system of Figure 1 in producing a part; and [0020]
  • Figure 3 is a graph illustrating one example of current flow generated versus time during a laser scan of the powder bed;
  • FIG. 4 is high level block diagram of on another embodiment of a system in accordance with the present disclosure where the system incorporates dual lasers and dual focus/scan units;
  • Figures 5a and 5b represent a high level flowchart illustrating various operations that may be carried out using the system of Figure 4 in focusing a first beam, as well as co-aligning the beams from both of the lasers of the system.
  • a system 10 is shown in accordance with one example of the present disclosure.
  • the system 10 forms an additive manufacturing system, and more specifically a Laser Powder Bed Fusion (“LPBF”) system.
  • the system 10 may include an optical light source 12, for example a laser (hereinafter referred to for convenience as “laser 12”) having sufficient power to melt metal powder or other high temperature materials.
  • the laser 12 may be a diode or diode to fiber laser.
  • the laser 12 may be a 500W, 1070 nm, Ytterbium doped YAG fiber laser.
  • the laser 12 may have its power controlled by an electronic controller 14.
  • the laser 12 receives laser power control signals from the electronic controller 14 and generates a laser beam 16 which may be applied to a laser focus and scan unit (e.g., focusing lens) 18 which focuses the beam 16 to a beam 16’ having a desired spot size.
  • the laser focus and scan unit 18 may be controlled by a separate laser scan controller 19 which may or may not be in communication with the electronic controller 14.
  • the beam 16’ is directed at a powder bed 20 by the laser focus and scan unit 18, where the powder bed 20 is disposed on an electrically conductive substrate 22.
  • the powder bed 20 may be formed by powder particles, for example, metallic powder particles.
  • the substrate 22 is typically a metallic substrate.
  • the substrate 22 rests on an electrically non-conductive surface layer 24, which may in turn be supported by a motion stage 26.
  • the motion stage 26 may simply be a fixed material support surface which remains stationary throughout operation of the system 10. However, if the motion stage 26 is included, then it is typically movable in the Z axis to facilitate the deposition of each subsequent powder material layer as the part is built layer by layer. However, in some implementations the motion stage 26 may be movable in the X-Y axes as well. In either event, if the motion stage 26 is included it may be controlled by suitable control signals, for example control signals from the electronic controller 14, so that the beam 16’ may be scanned over the powder bed 20 as needed to form each layer of a part. Alternatively, the laser 12 and the laser scan controller 18 may be moved while the substrate 22 is held stationary during operation of the system 10 when making a part. Both implementations are envisioned by the present disclosure.
  • the system 10 may also include a current measuring subsystem 28, for example a current preamplifier or possibly an ammeter 28, in communication with the substrate 22 for reading a current flow created by electrons being displaced as the powder bed 20 is heated by the laser 12. The electrons are displaced by thermionic emission as the metallic particles forming the powder bed 20 are heated.
  • the current measuring subsystem 28 will be referred to as “the current preamplifier 28” throughout the following discussion.
  • the current flow signal which in this example is an analog signal, may be transmitted to an analog-to-digital (“A/D”) converter 30 via a suitable conductor or electrical cable 32.
  • A/D converter 30 in this example is shown incorporated in the electronic controller 14, however, it may alternatively be included in a circuit together with the current preamplifier 28, or possibly even be included as a fully separate subsystem.
  • the electronic controller 14 may be provided as a field programmable gate array (FPGA), or alternatively as any other suitable form of processor/computing component.
  • the electronic controller 14 may include a non-volatile memory (e.g., RAM and/or ROM) 34 for storing a control software module 36.
  • the control software module 36 may include one or more distinct software modules and/or look-up table(s) for use by the electronic controller 14 during its operation.
  • a display screen (e.g., LED, CRT, etc.) 38 may be incorporated along with an optional user input peripheral (e.g., keyboard, mouse, etc.) 40.
  • the display screen 38 (e.g., LED screen, LCD screen or Cathode Ray Tube (CRT)) may be used by an operator to monitor current and/or temperature data during a scanning operation to help control the system 10 as a part is being formed using the powder bed 20.
  • the input peripheral 40 may be provided to enable the user to input at least one of data or commands to the electronic controller 14 during operation of the system 10 or during a calibration operation before making a part.
  • the part may be formed in a layer-by-layer process where each layer is heated by the laser beam 16’ to fuse select portions or all of the powder layer, and then a subsequent quantity of powdered material is added on top of the just-fused layer to form a new subsequent layer. This operation may be repeated (i.e., depositing new powder layer, fusing select portions or all of the layer, depositing new powder layer, fusing, etc.) until a three dimensional part is formed on the substrate 22.
  • the system 10 takes advantage of the fact that when the laser 12 heats the powder bed 20 using the laser beam 16’, thermionic emission takes place in which electrons are emitted from the heated surface of the powder bed 20.
  • the powder bed 20 typically includes metallic particles in powder form.
  • the electrical connection of the current preamplifier 28 between ground and the substrate 22 enables electrons to flow to the substrate 22 and to the depleted work surface (i.e., to the powder bed 20) from ground through the current preamplifier.
  • electrons may not always flow from the current preamplifier 28 to the substrate 22 and to the powder bed 20 (i.e., depleted work surface). Interactions with the gas produced during the heating may cause the electrons to flow back into the substrate 22.
  • the substrate 22/powder bed 20 may be float at a desired potential (e.g., either a positive voltage or a negative voltage), which is indicated in Figure 1 by voltage source V1 .
  • a desired potential e.g., either a positive voltage or a negative voltage
  • the current flow is measured by the current preamplifier 28 and the current preamplifier provides an analog signal representative of same to the electronic controller 14.
  • the A/D converter 30 converts this analog signal into a digitized signal.
  • the current measured is proportional to the temperature. It is not critical that the exact temperature of the powder bed 20 and/or substrate 22 is known, but rather simply a detected change in temperature is required (e.g., a change from a “known acceptable” or “steady state” temperature is acceptable).
  • the digitized signal may therefore be representative of a temperature of the powder bed 20 at specific locations of the powder bed 20 as the laser beam 16’ is scanned over the powder bed 20.
  • the electronic controller 14 uses the control software module 36 to evaluate the digitized signal and, in one embodiment, uses it to determine if an under-temperature condition or overtemperature condition exists during the scanning of the powder bed 20. In one embodiment the electronic controller 14 adjusts the laser power control signals applied to the laser 12 to eliminate or mitigate the under-temperature or over-temperature condition(s) during the scanning. Over-temperature and/or under-temperature information may be displayed, in one embodiment, in real time on the display screen 38.
  • a high level flowchart 100 is shown of operations that may be performed by the system of Figure 1 .
  • the laser 12 generates the laser beam 16’.
  • the laser scan controller 19 is used to control the laser focus and scan unit 18 to scan the laser beam 16’ across the powder bed 20.
  • the current preamplifier 28 reads the current flow and provides an analog signal representative of same to the A/D converter 30 of the electronic controller 14.
  • the flowchart of Figure 2 illustrates three different control methodologies for making use of the digitized signal from the A/D converter 30: “Process Monitoring” control; “Setup Optimization” control; and “On-the-Fly” control.
  • the control software module 36 may include suitable software for one, two or all of these control methodologies.
  • the Process Monitoring control may be executed at operation 110 in Figure 2 and may involve using the current preamplifier 28 to measure current as a function of time during processing (i.e., fusing) of the powder bed 20.
  • the output e.g., temperature
  • the operator may identify if the measured temperature is within a predetermined normal or expected range for the laser/powder bed material, conditions.
  • the user may determine or identify areas of over-temperature or under-temperature to known (i.e., predetermined) temperature parameters.
  • the user may use the input peripheral 40 to input any needed laser power changes to modify the laser power control signals applied to the laser 12 as needed to increase or decrease the power of the laser beam 16’.
  • operations 116 and 118 may instead involve the use of a “smart” system that performs the operation of determining and generating any needed laser power changes via machine learning software or other like software. In either case, if the part is not complete, as indicated at operation 120, then operations 104-110 and 116-120 may be repeated until the part is complete.
  • the “Setup Optimization” of operation 112 in Figure 2 is the second control option for the system 10.
  • the Setup Optimization operation 112 may instead involve a calibration-like procedure which is performed before the system 10 is used to make a part. This may involve calibrating laser 12 focus by scanning the laser scan unit 18 through a predefined range while the laser beam 16’ is directed at the substrate 22 (e.g., which may be a metal plate), and measuring the resulting current flow using the ammeter 28. The optimum laser focus point occurs at the maximum measured current. Areas where the current increases above the steady state or “known good” current may be automatically identified and the laser power adjusted in these regions, with such laser power adjustments saved to the memory 34 for subsequent recall and use by the electronic controller 14 during a subsequent scan.
  • the laser scan process is repeated, and the laser power adjusted, until the measured current is constant for all regions of the scan pattern.
  • this process may involve the electronic controller 14 continuously comparing the measured current to a predetermined current range stored in the memory 34 and associated with the “Setup Optimization” control routine, as a scan is being carried out, and from this comparison any changes in laser power, as well as specific locations during the scan noted where such laser power changes are needed, are stored by the electronic controller 14 so that same can be applied during the process of actually heating and fusing a powder bed layer.
  • a laser power “map” is created which identifies any area or region during a scan where laser power needs to be temporarily increased or decreased, which is used by the electronic controller 14 during every subsequent scan to apply the needed laser power corrections.
  • the needed adjustment in operation 116 may involve the power and/or the laser focus
  • the actual adjustment made in operation 118 may involve the laser power and/or laser focus.
  • Operation 114 in Figure 2 is the third control option which provides closed loop, “on-the-fly” control over power applied to the laser beam 16’.
  • This methodology involves using the electronic controller 14 to compare the measured steady state current in real-time, during processing of the powder bed 20.
  • This embodiment may require the electronic controller 14 to be provided in the form of a Field Programmable Gate Array (FPGA) to provide the necessary processing power and speed.
  • the laser output power level is adjusted by the electronic controller 14 in real time as the laser beam 16’ is being scanned over the powder bed 20.
  • FPGA Field Programmable Gate Array
  • the on-the-fly control methodology may involve translating the digitized electrical signals from the A/D converter 30 into corresponding temperature signals and then comparing the temperature signals to a predetermined temperature threshold value to determine if laser 12 power needs to be decreased or increased.
  • the temperature signals could be compared to a predetermined, desired temperature range within which it is desired to maintain the detected temperature during all or part of a scan.
  • one or more look-up tables of temperature/laser power may be stored in the memory 34 and used by the electronic controller 14 to apply the needed laser power correction signals to the laser 12.
  • the on-the-fly control methodology may be employed using a pure closed loop control methodology, or optionally an open loop control methodology using look-up table(s) or other stored information.
  • the electronic controller 14 monitors the temperature of the powder bed 20 during the scan, in real time, and applies the laser power control signals to the laser 12, in real time, to maintain the temperature of the power bed within a predetermined temperature range throughout the entire scan of the powder bed.
  • the electronic controller 14 may be used to automate operations 116, 118 and 120. Accordingly, in this implementation, the system 10 may not require any user involvement while a part is being constructed using the system 10. It will be appreciated that in some instances the memory 34 may have suitable software for implementing two or more of the above described control methodologies at operations 110, 112 and 114. As such, the system 10 is not limited to use with only one of the above described control methodologies at a time. It is also possible that modifications of one or more of the control methodologies 110, 112 and 114 may be implemented without departing from the spirt and scope of the present disclosure. Each of the methodologies of operations 110, 112 and 114 enable laser power correction signals to be applied, in situ, when forming each layer of a multi-layer 3D part.
  • Figure 3 illustrates a graph of a waveform 200 to show one example of current flow versus time that results when the laser beam 16’ is scanned over the powder bed 20.
  • the dips 202 and 204 in the waveform 200 represent points of overheating of the powder bed 20.
  • the relatively steady state portions 206 represent a temperature at or under a desired, predetermined temperature, and portion 208 represents turning off of the laser at the end of a track.
  • the system 10 and method of the present disclosure therefore provides a system with an in-process monitoring and power adjustment tool for use in a laser powder bed fusion platform which enables in situ modifications to be made to the laser power to optimize the temperature of the powder bed 20 across the entire scan.
  • the system 10 and method provides a number of important advantages over previously designed systems. For one, the signal detection method described herein is relatively inexpensive to implement into a LPBF system when compared to other methods.
  • the current signal generated during scanning can also be measured with high bandwidth (high sampling rate, up to 1 MHz or possibly even higher).
  • the current signal can be measured by the system 10 during processing over all build length scales (i.e., over an entire layer of virtually any size).
  • the current output signal generated by the system 10 is also relatively straightforward to interpret, and is easily coupled to suitable processing electronics (e.g., electronic controller 14) for on-the-fly control and automation of applied laser power corrections.
  • suitable processing electronics e.g., electronic controller 14
  • the results are reducible to fundamental physical equations and the temperature resolved from the measured current, for example, using the Richardson-Dushman relationship and material specific constants.
  • FIG 4 there is shown a system 300 in accordance with another embodiment of the present disclosure.
  • the system 300 in this example incorporates many of the components of the system 10, and therefore the system shown uses the same reference number as those used in Figure 1 for components which are identical to those described in connection with the system 10 of Figure 1.
  • the system 300 makes use of two optical light sources 12a and 12b, which in this example may be identical in construction and operation, but need not necessarily be identical in either of construction or operation.
  • the system 300 also makes use of two focus and scan units 18a and 18b, each being associated with a respective one of the lasers 12a and 12b.
  • laser 12a feeds the beam 16a’ to the focus and scan unit
  • laser 12b feeds the beam 16b’ to the focus and scan unit 318b.
  • Both lasers 12a and 12b may be in communication (uni-directional or bi-directional communication) with the electronic controller 14, such that each may have its output power controlled by the electronic controller 14 and optionally may provide a feedback signal to the electronic controller 14 if closed loop feedback is used for the power control.
  • a focus of each laser 12a and 12b may be initially carried out by first moving the beam 16a’ from the laser 12a along a track on the substrate 22 (i.e., build plate). This may be explained with reference to flowchart 400 in Figure 5a. Initially at operation 402, laser beam 16a’ from the laser 12a is focused at an initial focus setting, and then the beam is scanned along a track on the substrate 22 (or along a sample material layer). At operation 404 the current measuring subsystem 28 measures the current flow in real time as the beam 16a’ is scanned along the track and records the electronic controller 14 records the average current measured over the full track.
  • the controller 14 then focuses the beam 16a’ in a desired incremental step (i.e., to an incrementally different focus setting) and repeats the scanning of the beam 16a’ over the full track, and then records the average current measured over the track by the current measuring subsystem 28.
  • the electronic controller 14 checks if all the focus setting have been checked, and if not, repeats operation 406. When all the possible focus settings of the laser 12a have been checked, then at operation 410 the electronic controller 14 identifies the focus setting that created the maximum current flow across the track, and then focuses the beam 16a’ of laser 12a to that specific focus setting.
  • the electronic controller 14 may then add that specific focus setting to a calibration data file 36a ( Figure 4) that it maintains in the memory 36 for future manufacturing operations to be carried out by the system 300.
  • the electronic controller 14 may check if all of the lasers of the system 300 have been focused and, if they one or more have not, then at operation 414 the next laser being used in the system that has not yet been focused is selected. Operations 402-410 are then repeated. When the check at operation 412 produces a “YES” answer, then the focusing of each of the lasers 12a, 12b, etc. of the system is complete.
  • the beam 16a’ of the first selected laser for example laser 12a
  • the beam 16b’ from a second one of the lasers being used, for example laser 12b is aimed at the substrate 22 in the vicinity of the first target spot.
  • the electronic controller 14 begins moving the beam 16b’ from the laser 12b in a desired pattern, for example and without limitation a raster pattern, around the first target spot.
  • the electronic controller 14 records the magnitude of the current measured by the current measuring subsystem 28, in real time, which is produced by thermionic emission as a result of the combined optical signals from the of the two beams 16a’ and 16b’, at a plurality of X/Y locations around the first target spot. The electronic controller 14 then identifies the X/Y location where the current signal was at a maximum, and records that X/Y location in the calibration data file 36a.
  • the electronic controller 14 then makes a check if all the predesignated target spots on the substrate 22 have been imaged by the two lasers 12a and 12b. If not, then at operation 422 the electronic controller 14 moves the beam 16a’ from the first laser 12a to the next predesignated target spot and aims the beam 16b’ in a vicinity of the second predetermined target spot. Operation 418 is then repeated and the X/Y location of the 16b’ where the beams 16a’ and 16b’ together produce the maximum current flow is recorded in the calibration data file 36a. Operations 418-422 are repeated until the check at operation 420 indicates that all of the predetermined target spots on the substrate 22 (build plate) have been checked.
  • operation 420 produces a “YES” answer, then a check is made if all of the lasers 12 of the system 300 have been co-aligned. If the answer to this inquiry is “NO”, then the electronic controller 14 selects the next laser 12 for co-alignment, and operations 420-422 are repeated. When the check at operation 424 indicates a “YES” answer, then the co-alignment process for all the lasers 12 is finished. It will be appreciated that all of the lasers 12 used in the system 300 may be co-aligned to the first laser 12a, or all of the lasers 12 may be co-aligned to any other laser being used in the system 300.
  • the spacing of the predesignated target spots may be, in one example, every 1 mm such that the substrate is divided into an X/Y grid of 1 mm x 1 mm squares.
  • the beam 16a’ is then aimed at the center of each 1 mm x 1 mm square, and the beam 16b’ scanned around the full area of the 1 mm x 1 mm square to determine the precise location of the beam 16b’ where the current signal produced by the two beams is maximized.
  • the scanning be done in accordance with other scan patterns, and that the co-alignment process described above is not limited to any specific scanning pattern.
  • the substrate 22 could be divided into a series of concentric rings, and the scanning carried out in a circular pattern around each ring, one ring at a time.
  • Other scanning patterns are also possible.
  • the electronic controller 14 can slightly modify the aiming of the laser 12b as both lasers are scanned over the substrate 22, so that the co-alignment of the two lasers 12a and 12b is maintained as the lasers 12a and12b travel over all areas of the substrate 22.
  • operations 412-418 may be used to co-align any number of independent lasers over the full area of the substrate 22.
  • This feature has significant importance as it enables the focusing of each laser, and the co-alignment of two or more beams, to be quickly and easily checked and calibrated, in situ, without additional equipment being required to be coupled to the system 300, and without complex calibration procedures.
  • This ensures optimum build conditions to best ensure that component parts built using the systems 10 or 300 are built under identical conditions over the full area of the substrate 22, regardless if one laser is used or if multiple lasers are used during the build process.
  • these calibration procedures require extensive ex situ analysis and are not routinely performed during each component build.
  • Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail.
  • first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments.
  • Spatially relative terms such as “inner,” “outer,” “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Automation & Control Theory (AREA)
  • Analytical Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Plasma & Fusion (AREA)
  • Laser Beam Processing (AREA)

Abstract

La présente divulgation concerne un système qui peut posséder un dispositif de commande électronique, une source de lumière optique commandée par le dispositif de commande électronique, qui génère un faisceau possédant un niveau de puissance de sortie, et un sous-système de mesure de courant (CMS) électriquement couplé à un substrat conducteur (par exemple, un substrat métallique (MS)), pendant qu'une couche de lit de poudre (PBL) est déposée sur le substrat métallique. Le CMS peut être en communication avec le dispositif de commande électronique et détecte un flux de courant lors du chauffage du MS et/ou de la PBL lorsque le faisceau est balayé sur la PBL. Le CMS génère un signal de flux de courant en fonction du flux de courant détecté. Le signal de flux de courant est utilisé par le dispositif de commande électronique pour déterminer lorsque la température du substrat et/ou de la PBL est au moins supérieure et/ou inférieure à une température souhaitée.
PCT/US2021/062621 2018-06-27 2021-12-09 Surveillance et optimisation en service de fabrication additive par fusion de lit de poudre laser à l'aide d'une détection d'émission thermo-ionique WO2022132564A1 (fr)

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