Patent Application
20250001506
The present disclosure relates generally to laser powder bed fusion additive manufacturing and, more particularly, to a method of monitoring a laser powder bed fusion additive manufacturing process.
Laser powder bed fusion (LPBF) additive manufacturing is an additive manufacturing, or 3-D printing, technology that uses a laser to sinter or fuse metallic or polymeric particles together in a layer-by-layer process. LPBF is typically used as an industrial process to make near net shape parts. Some LPBF processes sinter the build powder particles, while others melt and fuse the build powder particles. LPBF is also known as direct metal laser sintering (DMLS).
LPBF additive manufacturing processes are dynamic, high temperature, high energy processes in which conditions change rapidly as a laser scans a build powder bed to form a melt pool. The combination of rapidly changing conditions and high temperature/high energy create an environment in which defects can form in parts made with an LPBF additive manufacturing process. Because defects formed in such parts can be difficult to detect without elaborate inspection techniques, including, for example, computed tomography scans (CT or CAT scans), certifying parts made with an LPBF additive manufacturing process for commercial use can be a challenge.
One aspect of this disclosure is directed to a laser powder bed fusion (LPBF) additive manufacturing system that includes a build plate, a build station piston configured to adjust the height of the build plate as a part is built on top of the build plate, and a powder chamber configured to contain loose build powder, wherein the powder chamber surrounds the build plate. The LPBF additive manufacturing system also includes a laser system configured to direct a laser beam onto the loose build powder to form a melt pool. The melt pool forms a layer of the part as the melt pool solidifies. As each layer of the part is formed, the build station piston lowers the build plate and part by a predetermined distance corresponding to a desired thickness of a next layer of the part. The LPBF additive manufacturing system further includes a powder coater configured to distribute additional build powder over the part after completion of each layer of the part, a controller, at least one neuromorphic sensor configured capture asynchronous data indicative of visually observable changes to the melt pool, optionally, at least one synchronous sensor configured to capture synchronous data that includes at least one of melt pool temperature and melt pool pressure, and means to transmit to the controller the asynchronous data from the at least one neuromorphic sensor and, optionally, the synchronous data from the at least one synchronous sensor. The controller is configured to process the asynchronous data from the at least one neuromorphic sensor and, optionally, the synchronous data from the at least one synchronous sensor to determine whether conditions in the LPBF additive manufacturing system are suitable for formation of or protentional formation of defects in the part. The controller is further configured to take at least one predetermined mitigation action to mitigate the formation of or potential formation of defects in the part.
Another aspect of the disclosure is directed to a method for correlating laser powder bed fusion (LPBF) additive manufacturing system data with formation of defects in LPBF manufactured parts. The method includes determining data available from the LPBF additive manufacturing system, selecting at least one build design to be a basis for collecting data to correlate LPBF additive manufacturing system data with formation of defects in LPBF manufactured parts, and building a plurality of test pieces of the at least one build design using a LPBF additive manufacturing system and collecting at least a portion of the data available from the LPBF additive manufacturing system as each of the plurality of test pieces is built. The method also includes inspecting each of the plurality of test pieces to determine if any of the test pieces have defects, assessing any defects identified as a result of the inspection to determine when the defects formed during the build process and the likely cause of the defect, and correlating data collected when the defects formed during the build process to the identified defects. The method further includes determining which of the LPBF additive manufacturing system operating conditions that are observable with the at least one neuromorphic sensor and the at least one synchronous sensor can be used as criteria to indicate the formation of or potential formation of defects; and providing to a LPBF additive manufacturing system controller the identified criteria to indicate the formation of or potential formation of defects in a part, whereby the LPBF additive manufacturing system controller is configured to provide a real time indication of the formation of or potential formation of defects in the part during a build cycle.
Yet another aspect of this disclosure is directed to a method for additive manufacturing parts using a laser powder bed fusion (LPBF) additive manufacturing system. The method includes the steps of providing to the LPBF additive manufacturing system an initial batch of build powder, building a part using selected LPBF additive manufacturing system operating parameters, and collecting data about the LPBF additive manufacturing system operating conditions with at least one neuromorphic sensor and, optionally, at least one synchronous sensor. The method also includes transmitting to a LPBF additive manufacturing system controller the data collected about the LPBF additive manufacturing system operating conditions with at least one neuromorphic sensor and, optionally, at least one synchronous sensor and processing, by the LPBF additive manufacturing system controller, the data collected about the LPBF additive manufacturing system operating conditions with the at least one neuromorphic sensor and, optionally, the at least one synchronous sensor to determine whether conditions in the LPBF additive manufacturing system are suitable for the formation of or protentional formation of defects. If the controller determines that conditions are suitable for the formation of or potential formation of defects, the controller takes at least one predetermined mitigation action to mitigate the formation of or potential formation of defects.
Laser powder bed fusion (LPBF) additive manufacturing is an option to make near net shape parts. The dynamic, high temperature, high energy processes conditions that are characteristic of LPBF additive manufacturing processes create an environment that is challenging to monitor using conventional techniques. For example, the rapid changes that occur in a LPBF melt pool cannot be captured readily using conventional high speed cameras due to frame rate limitations. Similarly, the high temperatures associated with the LPBF melt pool create a dynamic range challenge for high speed cameras. As a result, it is difficult or even impossible to detect the formation of defects in parts during manufacture using an LPBF additive manufacturing process. For the same reason, it has been difficult or even impossible to control the LPBF process to limit or prevent the formation of such defects.
The relatively recent development of neuromorphic sensors, also known as event cameras, has created the possibility of monitoring LPBF additive manufacturing processes in real time. Neuromorphic sensors do not capture images using a shutter as conventional (frame) cameras do. Rather, neuromorphic sensors capture images as a collection of individual pixels that operate independently and asynchronously from all of the other pixels in the neuromorphic sensor. Each pixel reports changes in brightness as they occur and remains silent if there is no change in brightness. This feature allows neuromorphic sensors to have microsecond responsiveness and allows for a higher sampling rate that is possible using other techniques, such as high speed cameras.
The asynchronous data collection from the neuromorphic sensors can be used to identify anomalies and instabilities in the melt pool, including anomalies associated with the formation of defects in the additively manufactured part. Defects known to occur in LPBF manufactured parts include porosity, unfused powder, balling, cracking, warping, delamination, swelling, formation of humps and valleys, and other defects. Data collected from neuromorphic sensors can be supplemented with data from other sensors compatible with the LPBF environment, such as laser sensors, voltage sensors, and other sensors to create a “sensor fusion” environment to provide a richer set of data for monitoring the LPBF process.
A typical LPBF system 10 includes a build plate 12, a build station piston 14 that adjusts the height of the build plate 12, a workpiece or part 16 that is built on top of the build plate 12, a powder chamber 18 to contain loose, and unconsolidated build powder 20 that surrounds the workpiece 16. A typical LPBF system 10 also includes a powder coater 22 that distributes additional build powder 24 over the workpiece 16 after completion of each layer formed on the workpiece 16. A laser system 26 combined with a controlled laser mirror 28 directs a laser beam 30 onto loose build powder 20 to form a melt pool (not shown) that, when solidified, forms a layer of the workpiece 16. As each layer of the workpiece 16 is formed, the build station piston 14 lowers the build plate 12 and workpiece 16 by a predetermined distance that corresponds to the desired thickness of the next layer of the workpiece 16. The powder coater 22 then moves across the top of the loose build powder 20 to distribute a layer of additional build powder 24 that will then be consolidated with the laser beam 30 to form the next layer of the workpiece 16.
Controller 32 controls the height of the build plate 12 by moving the build station piston 14, which in turn controls the thickness of each layer of the workpiece 16. Controller 32 also controls the movement of the powder coater 22 as it distributes additional build powder 24 and the movement of the laser beam 30 as it forms the melt pool that consolidates loose build powder 20 to form each layer of the workpiece 16. For example, the controller 32 controls LPBF system 10 operating parameters, including:
Controller 32 typically includes a reference database 34 and processor 36. Reference database 34 contains processing data relevant to the LPBF system 10, build powder to be used to produce the workpiece 16, and the specific work piece 16 to be produced. Processor 36 contains programming to interface with the reference database 34 to control the LPBF system 10 to products parts, such as workpiece 16, as is known to a person of ordinary skill in the art. Workpiece 16 can be a near-net-shaped part (i.e., initial production of the part that is very close to the final (net) shape).
Controller 32 can also collect data from sensors used to monitor the LPBF process, including at least one neuromorphic sensor 38, which provides an asynchronous data stream indicative of visually observable changes to the LPBF process, including changes to the melt pool. The at least one neuromorphic sensor 38, can collect data from any portion of the observable electromagnetic spectrum associated with the LPBF process. For example, the neuromorphic sensors 38 can be configured to collect data across a range of desirable wave lengths, including wave lengths commonly associated with the infrared band, the visible band, and the ultraviolet band as well as other bands of the electromagnetic spectrum. Due to the high sampling rate (e.g., 1 MHz or 1,000,000 equivalent frames per second) of the neuromorphic sensors 38 compared with other image capture devices, such as high resolution cameras and high speed/ultra-high speed cameras, the neuromorphic sensors 38 have a microsecond temporal resolution that permits capture of data from very rapidly occurring events. In addition, the neuromorphic sensors 38 have a much higher dynamic range (e.g., 120 dB) compared with other image capture devices, allowing capture of data at a high resolution. Combining the high sampling rate with high resolution imaging allows the neuromorphic sensors 38 to produce a rich dataset for assessing the LPBF process.
The at least one neuromorphic sensor 38, which provides fast, high resolution asynchronous data can optionally be combined with at least one synchronous sensor 40 to capture additional data such as melt pool temperature, pressure, and other visual and environmental data. Similarly, data from the at least one neuromorphic sensor 38 and the at least one synchronous sensor 40 can optionally be combined with the LPBF system 10 operating parameters discussed above, including:
With the availability of a comprehensive data set, the method depicted in
At step 106, a plurality of test pieces of the at least one build design are built using a LPBF system. Different combinations of LPBF system operating parameters should be selected so the test pieces represent a range of anticipated LPBF system operating parameters for the types of parts for data to correlate LPBF system data with the formation of defects in LPBF manufactured parts will be collected. If desired, the LPBF system operating conditions can be selected to induce the formation of defects including, but are not limited to, porosity, unfused powder, balling, cracking, warping, delamination, swelling, formation of humps and valleys, and other defects. Inducing defects into the plurality of test pieces can be useful in later correlating data with the formation of such defects. During step 106, at least a portion of the data identified in step 102 is collected as each of the plurality of test pieces is built. The data collected in step 106 can be reviewed as it is collected and, in any case, is recorded for analysis in later steps of the method 100.
At step 108, each of the plurality of test pieces are inspected to determine if any of the test pieces have defects including, but are not limited to, porosity, unfused powder, balling, cracking, warping, delamination, swelling, formation of humps and valleys, and other defects. The plurality of test pieces can be inspected for defects using any relevant inspection techniques including visual inspection, dye penetrant inspection, x-ray inspection (including CT/CAT scans), destructive inspection, and any other type of inspections that would be useful for identifying the presence of defects in the plurality of test pieces.
In step 110, any defects identified as a result of the inspection step 108 are assessed to determine when they formed during the build process and the likely cause of the defect. The data collected in step 106 are then reviewed to correlate data collected when the defects formed during the build process to the defects themselves. The correlated data are then reviewed to determine which of the LPBF operating system operating conditions, including melt pool conditions, that are observable with the at least one neuromorphic sensor 38 and the at least one synchronous sensor 40 can be used as criteria to indicate the formation of or potential formation of defects. Going forward, in step 112, the identified criteria to indicate the formation of or potential formation of defects can be provided to (e.g., coded into) the LPBF system controller 32 to provide a real time indication of the formation of or potential formation of defects during a build cycle.
During step 206, the data about the LPBF system operating conditions, including melt pool conditions, are collected with the at least one neuromorphic sensor 38 and, optionally, the at least one synchronous sensor 40 and transmitted to the LPBF system controller 32 through means known in the art for transmitting signals from sensors to a controller. The LPBF system controller 32 processes data from the neuromorphic sensors 38 and, optionally, synchronous sensors 40 to determine whether conditions in the LPBF system, including at the melt pool, are suitable for the formation of or potential formation of defects.
If the controller 32 determines at step 206 that conditions are suitable for the formation of or potential formation of defects, the controller 32, at step 208, takes at least one predetermined mitigation action to mitigate the formation of or potential formation of defects. The mitigation action can be at least one of:
The disclosed system and method uses asynchronous data collection from neuromorphic sensors to identify anomalies and instabilities in the melt pool that are associated with the formation of defects in the additively manufactured part. By identifying the formation of or potential formation of defects during the build process, certain defects can be mitigated during the build process or, if not suitable mitigation is available, the build process can be terminated or stopped early, avoiding the time and expense of completing a part known to be defective. Further, the use of the disclosed system and method can improve the repeatability of a build process to the point that parts made with the process can be certified for commercial use without elaborate inspection techniques, including, for example, computed tomography scans (CT or CAT scans.
The following are non-exclusive descriptions of possible embodiments of the present invention.
A laser powder bed fusion (LPBF) additive manufacturing system, comprising: a build plate; a build station piston configured to adjust the height of the build plate as a part is built on top of the build plate; a powder chamber configured to contain loose build powder, wherein the powder chamber surrounds the build plate; a laser system configured to direct a laser beam onto the loose build powder to form a melt pool, wherein when the melt pool forms a layer of the part as the melt pool solidifies and wherein as each layer of the part is formed the build station piston lowers the build plate and part by a predetermined distance corresponding to a desired thickness of a next layer of the part; a powder coater configured to distribute additional build powder over the part after completion of each layer of the part; a controller; at least one neuromorphic sensor configured to capture asynchronous data indicative of visually observable changes to the melt pool; and means to transmit to the controller the asynchronous data from the at least one neuromorphic sensor and, optionally, the synchronous data from the at least one synchronous sensor. The controller is configured to process the asynchronous data from the at least one neuromorphic sensor to determine whether conditions in the LPBF additive manufacturing system are suitable for formation of or protentional formation of defects in the part. The controller is further configured to take at least one predetermined mitigation action to mitigate the formation of or potential formation of defects in the part.
The LPBF additive manufacturing system of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional elements.
A further embodiment of the foregoing system, further comprising at least one synchronous sensor configured to capture synchronous data that includes at least one of melt pool temperature and melt pool pressure, wherein the controller is configured to process the asynchronous data from the at least one neuromorphic sensor and the synchronous data from the at least one synchronous sensor to determine whether conditions in the LPBF additive manufacturing system are suitable for formation of or protentional formation of defects in the part.
A further embodiment of any of the foregoing systems, wherein the controller is further configured to process at least one of laser beam power, laser beam velocity, laser beam spot size, build plate temperature, layer thickness, laser hatch distance, laser hatch delay time, and laser hatch stripe width along with the asynchronous data from the at least one neuromorphic sensor and the synchronous data from the at least one synchronous sensor to determine whether conditions in the LPBF additive manufacturing system are suitable for the formation of or protentional formation of defects in the part.
A further embodiment of any of the foregoing systems, wherein the at least one predetermined mitigation action is at least one of: notifying an operator of the formation of or potential formation of defects in the part; changing at least one LPBF system operating parameter for at least the next layer of the build process; reworking all or part of a layer in which the defect was detected; stopping the build process so the part can be reworked manually; and stopping the build process so the part can be scrapped.
A further embodiment of the foregoing system, wherein notifying an operator of the formation of or potential formation of defects includes providing a visual or aural alert.
A further embodiment of the foregoing system, wherein changing at least one LPBF additive manufacturing system operating parameter for at least the next layer of the build process includes changing at least one of laser beam power, laser beam velocity, laser beam spot size, build plate temperature, layer thickness, laser hatch distance, laser hatch delay time, and laser hatch stripe width.
A method for correlating laser powder bed fusion (LPBF) additive manufacturing system data with formation of defects in LPBF manufactured parts, comprising the steps of: determining data available from the LPBF additive manufacturing system; selecting at least one build design to be a basis for collecting data to correlate LPBF additive manufacturing system data with formation of defects in LPBF manufactured parts; building a plurality of test pieces of the at least one build design using a LPBF additive manufacturing system and collecting at least a portion of the data available from the LPBF additive manufacturing system as each of the plurality of test pieces is built; inspecting each of the plurality of test pieces to determine if any of the test pieces have defects; assessing any defects identified as a result of the inspection to determine when the defects formed during the build process and the likely cause of the defect; correlating data collected when the defects formed during the build process to the identified defects; determining which of the LPBF additive manufacturing system operating conditions that are observable with the at least one neuromorphic sensor and the at least one synchronous sensor can be used as criteria to indicate the formation of or potential formation of defects; and providing to a LPBF additive manufacturing system controller the identified criteria to indicate the formation of or potential formation of defects in a part, whereby the LPBF additive manufacturing system controller is configured to provide a real time indication of the formation of or potential formation of defects in the part during a build cycle.
The LPBF additive manufacturing system of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional elements.
A further embodiment of the foregoing method, wherein the build design is representative of parts to be built using the LPBF additive manufacturing system.
A further embodiment of any of the foregoing methods, wherein building a plurality of test pieces of the at least one build design using a LPBF additive manufacturing system includes selecting LPBF additive manufacturing system operating parameters so the test pieces represent a range of LPBF additive manufacturing system operating parameters.
A further embodiment of any of the foregoing methods, wherein building a plurality of test pieces of the at least one build design using a LPBF additive manufacturing system includes selecting LPBF additive manufacturing system operating parameters to induce the formation of defects in the plurality of test pieces.
A further embodiment of any of the foregoing methods, wherein the defects in the plurality of test pieces include one or more of porosity, unfused powder, balling, cracking, warping, delamination, swelling, and formation of humps and valleys.
A further embodiment of any of the foregoing methods, wherein building a plurality of test pieces of the at least one build design using a LPBF additive manufacturing system includes selecting LPBF additive manufacturing system operating parameters so the test pieces represent a range of LPBF additive manufacturing system operating parameters.
A further embodiment of any of the foregoing methods, wherein collecting at least a portion of the data available from the LPBF additive manufacturing system includes recording the data for analysis.
A further embodiment of any of the foregoing methods, wherein inspecting each of the plurality of test pieces to determine if any of the test pieces have defects, includes inspecting the test pieces by at least one of visual inspection, dye penetrant inspection, x-ray inspection (including CT/CAT scans), and destructive inspection.
A method for additive manufacturing parts using a laser powder bed fusion (LPBF) additive manufacturing system, comprising the steps of: providing to the LPBF additive manufacturing system an initial batch of build powder; building a part using selected LPBF additive manufacturing system operating parameters; collecting data about the LPBF additive manufacturing system operating conditions with at least one neuromorphic sensor and, optionally, at least one synchronous sensor; transmitting to a LPBF additive manufacturing system controller the data collected about the LPBF additive manufacturing system operating conditions with the at least one neuromorphic sensor and, optionally, the at least one synchronous sensor; processing, by the LPBF additive manufacturing system controller, the data collected about the LPBF additive manufacturing system operating conditions with the at least one neuromorphic sensor and, optionally, the at least one synchronous sensor to determine whether conditions in the LPBF additive manufacturing system are suitable for the formation of or protentional formation of defects; and if the controller determines that conditions are suitable for the formation of or potential formation of defects, taking, by the controller, at least one predetermined mitigation action to mitigate the formation of or potential formation of defects.
The LPBF additive manufacturing system of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional elements.
A further embodiment of the foregoing method, wherein the selected LPBF additive manufacturing system operating parameters include at least one of laser beam power, laser beam velocity, laser beam spot size, build plate temperature, layer thickness, laser hatch distance, laser hatch delay time, and laser hatch stripe width.
A further embodiment of any of the foregoing methods, wherein the at least one predetermined mitigation action is at least one of: notifying an operator of the formation of or potential formation of defects; changing at least one of the LPBF additive manufacturing system operating parameters for at least the next layer of the build process; reworking all or part of a layer in which the defect was detected; stopping the build process so the part can be reworked manually; and stopping the build process so the part can be scrapped.
A further embodiment of the foregoing method, wherein notifying an operator of the formation of or potential formation of defects includes providing a visual or aural alert.
A further embodiment of the foregoing method, wherein changing at least one LPBF additive manufacturing system operating parameter for at least the next layer of the build process includes changing at least one of laser beam power, laser velocity, laser spot size, build plate temperature, layer thickness, and laser hatch distance, laser hatch delay time, and laser hatch stripe width.
While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.
