Patent Application
20220088684
The present disclosure relates generally to additive manufacturing systems, and more particularly, to processing three-dimensional (3D) printed parts.
AM systems, also described as three-dimensional (3D) printers, can produce structures (referred to as build pieces) with geometrically complex shapes, including some shapes that are difficult or impossible to create by relying on conventional manufacturing processes, such as machining. AM parts can advantageously be printed with diverse geometries and compositions using materials that allow the part to have specifically-tailored properties for a target application.
Various post-processing techniques may be used in AM systems after completion of the build piece to add or enhance features for the build piece, or to address imperfections or other artifacts in the build piece that may have been created during the print. Given the existing limitations in conventional post-processing techniques, which may result in quality problems, manufacturing latencies and other shortcomings, practitioners are continually seeking better ways to manufacture parts in a manner that helps achieve maximum manufacturing throughput while meeting quality requirements.
The following presents a simplified summary of one or more aspects in order to provide a basic understanding of such aspects. This summary is not an extensive overview of all contemplated aspects, and is intended to neither identify key or critical elements of all aspects nor delineate the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that is presented later.
The present disclosure is directed to multi-phase sensor systems for 3D printing, including a first sensor that senses during a first phase and a second sensor that senses during a second phase. In various embodiments, a multi-phase sensor system may include a first sensor that senses during a first time period, and a second sensor that senses during a second time period that may be mutually exclusive with or partially overlap with the first time period. In various embodiments, the sensors may be arranged at different locations. For example, the first sensor may be positioned to sense a larger portion of the printing area (e.g., by being positioned higher in a print chamber to have a larger field of view), and the second sensor may be positioned to sense a smaller portion of the printing area (e.g., by being positioned lower in the build chamber, closer to the build piece). The sensing of the second sensor may be, for example, based on the sensing information from the first sensor. For example, sensing information from the first sensor may be used to direct the second sensor to a specific area of interest sensed by the first sensor. The second sensor may provide, for example, a more detailed (e.g., higher resolution) sensing, which may for example include a different type of sensing than the first sensor. In various embodiments, the first sensor may be an image sensor (such as an optical camera, infrared imager, etc.) and the second-tier sensor may be another type of sensor (such as an eddy current sensor, etc.).
In various embodiments, an image sensor, or array thereof, may be positioned above a powder bed to image the bed as a weld pool migrates across the powder bed's surface. The weld pool may include a selected portion of the 3D printer's upper print layer(s) as it undergoes scanning by the printer's energy beam source. Because the energy beam has caused the print material in the weld pool to exceed its melting point, the weld pool may temporarily be in liquid form until it solidifies to form an intended part of the build piece. The weld pool can in this respect be a variable surface region of the powder bed, changing over time as different regions of deposited layers of print material are scanned. Images captured by the image sensor may be used to determine spatter of material ejected from weld pools caused by the intense heating of the high-energy beam, and the sensing information of the image sensor may be used to estimate a landing location of the ejected bit of material. The second sensor, such as an eddy current sensor, may be directed to the estimated landing location to perform additional sensing.
Imaging may be used to identify potential print defects such as matter ejected from the weld pool onto a landing location. The landing location may, for instance, be located on a different region from the build piece in progress. The eddy current sensor may detect potential defects not just on, but also within, a volume of print material including a build piece. As mentioned above, in various embodiments, a second sensor like the eddy current sensor may obtain from the image sensor the landing location information of the particle ejected from the weld pool. The particle may include a ceramic, an intermetallic, or the like. The eddy current sensor can more specifically identify features like the location, orientation or size of the particle. These identified features and other criteria can be used by one or more processors to determine a course of action, if any, to address the defect. In various embodiments, the processor(s) may suspend 3D printing while the defect is removed or repaired. Printing can thereafter resume. In other embodiments, the processor may physically mark the defective area so that the site can be identified and repaired later.
The sensors may detect other types of defects. Examples of defects include voids, (which can be a source of crack initiation in the final part if left unaddressed) inclusions (which can include the ejected matter above, and other foreign particulates), regions of unsintered or partially sintered powder in the build piece (that should otherwise be solidified in that region), geometrical anomalies in the build piece (e.g., a jagged edge instead of a curve), and others. The first and second sensors can work in concert to enable the processor(s) to identify these defects and provide instructions for any necessary repair or removal, whether during or after the print.
In one aspect of the disclosure, a sensor system for a three-dimensional (3D) printer includes a first sensor configured to determine a landing location of matter ejected during heating of print material to form a weld pool. The weld pool defines a portion of a build piece once the weld pool hardens. The sensor system includes a second sensor configured to detect a defect in the build piece based on the determination of the landing location.
In another aspect of the disclosure, a three-dimensional (3D) printer includes a processor, a build plate, and a recoater. The recoater is configured to successively deposit layers of print material onto the build plate. The 3D printer further includes an energy beam source. The energy beam source is configured to form a weld pool by heating selected regions of the print material in each layer to form a build piece. The 3D printer further includes an optical sensor. The optical sensor is configured to image an area including the weld pool to determine a landing location of matter ejected during heating of the print material to form the weld pool. The 3D printer also includes a non-optical sensor. The non-optical sensor is configured to detect a defect in the build piece based on the determination of the landing location.
In still another aspect of the disclosure, a method for 3D printing a build piece is disclosed. Layers of print material are successively deposited onto a build plate. A weld pool forms on the layers using an energy beam to heat the print material. The weld pool defines a portion of a build piece once the weld pool hardens. A first sensor is used to determine a landing location of matter ejected during heating of the print material to form the weld pool. A second sensor is used to detect a defect in the build piece based on the determination of the landing location.
One or more aspects comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative features of the one or more aspects. These features are indicative, however, of but a few of the various ways in which the principles of various aspects may be employed, and this description is intended to include all such aspects and their equivalents.
Various aspects of multi-sensing technologies for print artifacts in 3D printing and for addressing said defects in situ (in place) will now be presented in the detailed description by way of example, and not by way of limitation, in the accompanying drawings, wherein:
The detailed description set forth below in connection with the appended drawings is intended to provide a description of various exemplary embodiments of the concepts disclosed herein and is not intended to represent the only embodiments in which the disclosure may be practiced. The terms “exemplary” and “example” used in this disclosure mean “serving as an example, instance, or illustration,” and should not be construed as excluding other possible configurations or as preferred or advantageous over other embodiments presented in this disclosure. The detailed description includes specific details for the purpose of providing a thorough and complete disclosure that fully conveys the scope of the concepts to those skilled in the art. However, the disclosure may be practiced without these specific details. In some instances, well-known structures and components may be shown in block diagram form, or omitted entirely, in order to avoid obscuring the various concepts presented throughout this disclosure.
The combined sensor apparatuses and methods for multi-phase sensing, which may include identifying and potentially repairing potential defects, in this disclosure will be described in the following detailed description and illustrated in the accompanying drawings by various elements such as blocks, components, circuits, processes, algorithms, etc. These elements may be implemented using electronic and mechanical hardware, computer software, or any combination thereof.
By way of example, an element, or any portion of an element, or any combination of elements may be implemented using one or more processors. Examples of processors, such as that shown in element 129 of
The one or more processors may execute software. Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software components, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, object code source code, or otherwise.
Accordingly, in one or more example embodiments herein for providing sensor systems and 3D printers having the sensor systems, for 3D printing parts (build pieces), imaging print artifacts, sensing spatter, determining landing points of the spatter, combining received data to use in performing responsive actions such as automated in situ repairs, manipulating eddy currents for adjusting magnetic fields, removing inclusions, filling voids, melting unsintered or partially sintered print material, and performing other functions described herein, the functions may be implemented in hardware, software, or any combination thereof. If implemented in software, the functions may be stored on or encoded as one or more instructions or code on a computer-readable medium. Computer-readable media, as described below with reference to
This principles of this disclosure may be applicable to a variety of 3D printer types, including but not limited to powder bed fusion (PBF) printers including selective laser sintering (SLS), direct metal laser sintering (DMLS), selective laser melting (SLM), electron beam melting (EBM), etc.
The present disclosure is directed to advanced sensor systems that enhance the quality and accuracy of data generated during 3D printing. The sensor systems can include a combination of optical and non-optical sensors that provide real-time data about the presence of undesirable inclusions, voids, and other defects in the part being printed. A common problem in certain 3D printers is spatter, or matter ejected during the heating of print material to form a weld pool. Matter can be ejected, for example, from the area of the weld pool itself as the print material is heated quickly by an energy beam. Matter can be ejected, for example, from the area around the weld pool as the weld pool moves quickly across the surface of a layer of the print material. For example, metal powder in area around the melt pool may be thrown upwards by the intense heat and motion of the melt pool. Ejected matter may fall into another region of the build piece. For example, ejected matter may land at a location in the powder bed that will be, but has not yet been, fused to create part of the build piece. In other words, the ejected matter may land on powder that will be fused. In this case, for example, the ejected matter might cause a defect in the build piece when the powder is fused. For example, the ejected matter might cause an inclusion in the build piece when the fused powder solidifies. Notably, once the ejected matter becomes the defect upon solidification, the defect may not be able to be imaged, e.g., by an image sensor, such as an optical sensor. In addition to identifying the defects or other foreign particles, the sensor systems described in various configurations herein can provide information concerning their trajectory, velocity, landing location, size, orientation, composition, weight, and other characteristics. The 3D printer may use this data together with existing print specifications for the part (e.g., the CAD model, manufacturer's specifications, etc.) to evaluate whether identified defects or other artifacts require fixing or removal, including when any such actions should be initiated, if at all.
In some cases, implementing corrective measures during the print may be most useful while those defects are most accessible. Accordingly, in various embodiments, the data from the combined sensor system enables the 3D printer and its related hardware components to repair the defect during printing, such as by temporarily suspending the print job and extracting an inclusion (e.g., an undesirable ceramic or intermetallic matter particle) from the build piece without adversely affecting surrounding regions of the part.
As another example, the 3D printer may identify a defect in or near real time using combined information from different types of sensors. The processor may instruct the 3D printer to suspend the print. The 3D printer may repair the (then easily-accessible) defect, or extract the foreign matter, using a CNC machine tool, automated robotic arm, or other mechanism such as a brush or blade. In some arrangements, the processor may instruct the recoater to make selective deposits of additional print material, after which the processor may activate the 3D printer's laser or electron beam source to selectively re-melt and solidify the deposited powder. The energy beam source may also be used to melt an identified pocket of unsintered powder that is already present in the powder bed.
Immediately following the repairs or shortly thereafter, 3D printing can resume. In other arrangements, the processor may determine based on the detailed data that a fix is not needed and that the identified defect is innocuous and not harmful to the build piece. The processor(s) can therefore evaluate the diverse data about the defect to its benefit, determining in these cases that the print can proceed without further interruption.
Addressing fixes during the print may be quicker because the 3D printer has direct access to the problem. The system does not in that case have to unearth numerous layers before reaching the problem area, as may otherwise be required if every identified problem is just deferred until post-processing. Here, by contrast, post-processing times can beneficially be reduced, or reserved to other tasks. Another problem faced by manufacturers is whether the defect can even be detected or accessed at the post-processing stage in the first place. If the defect is buried in the middle of hardened metallic layers, for example, the defect may be difficult or impossible to detect, and even if it is detected might be infeasible to fix. The combined sensor system of the present disclosure can, however, provide additional, more diverse data to the processor that characterizes the nature of the defect. The 3D printer can better determine an appropriate time for the fix that increases quality assurance without causing undue inefficiencies.
In further embodiments, the 3D printer sensor system as disclosed herein also may include superior techniques to both identify and address defects. For example, an integrated sensor system may include optical sensors that are oriented to enable a three-dimensional representation. With these 3D views, the precise location of ejected material can be facilitated. Further, such defects can be neutralized quickly or immediately. In some embodiments, upon determining a landing location of ejected a particle of matter, the 3D printer may use an eddy current sensor to determine whether the particle creates or will create a defect in the build piece before they become deeply lodged underneath the layers.
PBF system 100 can also include a build floor 111 positioned within a powder bed receptacle. The walls of the powder bed receptacle 112 are shown in cross-section. In practice, the powder bed receptacle walls 112 may or may not form a closed perimeter, depending on the type and features of the 3D printer. The walls 112 generally define the boundaries of the powder bed receptacle, the latter of which is sandwiched between the walls 112 from the side and abuts a portion of the build floor 111 below. Build floor 111 can progressively lower build piece 107 so that recoater 101 can deposit a next layer. The entire mechanism may reside in a chamber 113 that can enclose the other components, thereby protecting the equipment, enabling atmospheric and temperature regulation and mitigating contamination risks.
Recoater 101 can receive print material from a separate hopper (not shown). In some arrangements, the hopper may be integrated with or part of recoater 101. A separate depositor may also be included in some 3D printers. The purpose of all of these embodiments, in general, is to provide print material to the powder bed 121. In the embodiment shown, recoater 101 is separate from the hopper. In other embodiments, the hopper may be configured as a large drum or source of metal powder. Recoater 101 contains a powder 124, such as a metal or alloy-based powder, and a leveler or blade 119 that can level the top of each layer of deposited powder 124 as it flows through powder flow aperture 177 during a recoating cycle. The hopper may act as a powder source that periodically fills the recoater 101 with powder (e.g., during a scan cycle) to enable the recoater 101 to deposit powder layers across the total necessary span of the powder bed 121.
During the recoating cycle, the energy beam 103 may be off while the recoater 141 moves horizontally along the direction of arrow 141. In so doing, recoater 101 may deposit a layer 161 of material. The thickness of layers 161 is exaggerated in the figure for clarity. That is, recoater 101 is positioned to deposit powder 124 in a space created over the top surfaces of build piece 109 and powder bed 121 and bounded by powder bed receptacle walls 112. In this example, recoater 101 progressively moves over the defined space while releasing powder 124 via powder flow aperture 177. As noted above, blade 119 can level the released powder to form a powder layer 161 that leaves a surface of the powder bed 121 configured to receive fusing energy from energy beam source 103 in a subsequent scanning cycle.
In some cases, the recoater 101 is configured bi-directionally, meaning that recoater 101 may deposit a layer 161 of powder in two directions. That is, in addition to depositing material as it moves from left-to-right along the axis of arrow 141, recoater 101 may also deposit a layer of powder through powder flow aperture 177 when it travels from right to left along the same. In this bi-directional embodiment of recoater 101, an additional blade (not shown) similar to blade 119 may be arranged opposite blade 119 and may be configured to level powder deposited when the recoater 101 is moving from right to left. Thus, for example, a first recoater cycle may occur where recoater 101 deposits a first layer 161 moving left to right, followed by a scanning cycle. Then the recoater 101 can perform another scan as it moves from right to left to deposit another layer 161 of powder. Another scanning step can occur, and so on until build piece 109 is completed.
In this way, one scan cycle may follow every recoater cycle. During the scan cycle, the energy beam source 103 uses deflector 105 to produce an energy beam 127 (e.g., a laser beam) for selectively fusing a cross-sectional region of the uppermost layer that will become a portion of build piece 109. The regions of the top layer that will not be part of the finished build piece may be left unsintered.
During this scanning cycle, energy beam source 103 forms a weld pool 186, which includes a region of powder 124 that is scanned by the energy beam 127, and that temporarily melts as a result. The melted region in the weld pool 186 soon thereafter can solidify as intended to form a permanent part of build piece 109.
Each time energy beam source 103 completes the scan of a layer, build floor 111 can lower by a thickness of one of the powder layers 161. The lowering of build floor 111 causes build piece 109 and powder bed 121 to drop by that powder layer thickness, so that the top of build piece 109 and powder bed 121 are lower than the top of powder bed receptacle wall 112 by an amount equal to the thickness of one of the powder layers 161. In this way, for example, a space with a consistent thickness equal to this powder layer thickness can be created over the tops of build piece 109 and powder bed 121.
In various embodiments, the deflector 105 can include one or more gimbals and actuators that can rotate and/or translate the energy beam source to position the energy beam. In various embodiments, energy beam source 303 and/or deflector 305 can modulate the energy beam, e.g., turn the energy beam on and off as the deflector scans so that the energy beam is applied only in the appropriate areas of the powder layer. For example, in various embodiments, the energy beam can be modulated by a digital signal processor (DSP). In embodiments incorporating electron beams as the energy source, deflector 105 can include deflection plates that can generate an electric field or a magnetic field that selectively deflects the electron beam to cause the electron beam to scan across areas designated to be fused. Deflector 105 can include an optical system that uses reflection and/or refraction to manipulate a laser beam to scan selected areas to be fused. Deflector 105 may be a lens, mirror, or another device that the processor can steer using its magnetic fields, for example, to direct the flow of an electron beam source. Because the electrons are charged particles, the processor can control their flow via the electric and magnetic fields. Where a laser is involved, which includes uncharged photons, a lens or mirror of the defector 105 can be directed in some embodiments to use reflection, refraction and other techniques to properly focus the laser on the correct area of the surface of the powder bed 121.
Also shown in
In some embodiments, processor 129 may retrieve in the memory 155 a computer-aided design (CAD) model representing the build piece 109. Processor 129 may compile the CAD model into a number of executable instructions corresponding to slices that the processor can use to print the build piece 109 using the scanning and recoating techniques described above. In some embodiments, the CAD model is already compiled by another source, and the compiled instructions are provided to processor 129 via memory 155. Processor 129 can use the print instructions to direct the behavior of the recoater, the energy beam source, and the deflector to properly produce build piece 109.
In various embodiments, PBF printer system includes an image sensor 148, which is positioned in this arrangement at the surface of chamber 113, as two adjacent cameras. In various embodiments, image sensor 148 may be, for example, a single image sensor (such as a single camera). In various embodiments, a plurality of image sensors or video monitors may be positioned at any relevant portion of the PBF system 100 to enable the image sensor 148, for example, to provide multiple views of the weld pool and its vicinity. Image sensor 148 may be communicatively coupled to processor 129 via controller bus 174. Image sensor 148 may be selectively activated, or in other cases, they may be powered on during the entire print job. Image sensor 148 may image the powder bed and may be automatedly controlled in some arrangements to follow the weld pool.
Image sensor 148 may take snapshots or make continuous views in the area of the weld pool or other parts of the powder bed. In various embodiments, image sensor 148 may be positioned to take images along the side of the powder bed so that multiple angles may be recorded. In some variations described further below, image sensor 148 may be oriented in a manner that can provide the processor with three-dimensional images of the weld pool and other portions of the powder bed. Both image sensor 148 and processor 129 may be communicatively coupled to an integrated machine tool 184 including robotic arm 185, so that in some embodiments, automated fixes may be performed in or near real time as described further below.
Referring still to
In some embodiments, image sensor 148 may be arranged on a swiveling or moving structure, such that image sensor 148 can be moved to different desired positions above the powder bed 121 or can be rotated above the powder bed 121.
3D printing system 100 may further include an eddy current sensor 171. While the eddy current sensor 171 can be coupled to different structures in various embodiments, in the embodiment of
In operation, an eddy current sensor 171 may induce a changing magnetic field, which can penetrate the layers 161 of the powder bed 121. This induced magnetic field can create eddy currents within the conducting metallic powder layer 121, including in the solid material in the build piece 109. The measured properties associated with the eddy currents (such as the magnitude and direction of the opposing magnetic field created by the currents) can be used to determine features of the build piece not only on the surface of, but also within, the build piece. In
In various embodiments, the eddy current sensor 171 (via processor 179 or its own internal circuitry) can receive data from the image sensor 148 relating to a landing location of ejected matter. During an ensuing recycling period, the eddy current sensor 171 can use the sensing heads 163 and 164 to measure features related to the ejected matter, including size, shape, geometry, density, and chemical composition. The eddy current sensor 171 can send its measurements to the processor 129. The processor 129 can use these measurements along with the data from the image sensor 148 to make real time determinations including (i) whether some type of on-site repair or removal is necessary; (ii) if a fix is necessary, whether the fix should be implemented immediately, at a specific time, or after the print in post-processing, and (iii) the nature and extent of the fix. As for (iii), for example, the fix may involve fusing a crack, adding and sintering material to fill voids, or removing ejected matter, among other possibilities.
In various embodiments, the image sensor 148 and eddy current sensor 171, together with the integrated machine tool 184 including robotic arm 185 and processor 129, can form a closed loop wherein the processor 129 can make on the fly assessments about the need for repairs. Processor 129 can further communicate with robotic arm 185 over controller bus 174. Processor 129 can, for example, submit commands for the 3D printer to suspend printing (if necessary), and to use robotic arm 185 to perform machining in the powder bed 121 or the build piece 109 to fix a defect, remove an inclusion, etc. In some configurations, the integrated machine tool 184 with the robotic arm 185 may be configured to perform conventional types of machining operations. For example, the robotic arm 185 may be configured to perform subtractive manufacturing to remove spatter that became fused to the build piece 109. The 3D printer may then apply “patches” to add and solidify material to the build piece where the spatter was removed, before the 3D printer resumes full print mode. In the case of partially sintered or unsintered material in the build piece 109, the robotic arm 185 may be configured to remove just enough material to access the area of partially sintered or unsintered powder, after which the 3D printer may apply an energy beam source 103 to the region to solidify the powder and remove the defect.
While integrated machine tool 184 and its robotic arm 185 can be an effective way to perform in situ repairs, some 3D printers may lack this equipment. In that case, the repairs can be performed using different types of equipment or even external equipment, so that the machine tool 184 may be omitted in some embodiments.
In various embodiments, other types of non-optical sensors may be used in the 3D printer 100. Exemplary types of sensors may include acoustic sensors, capacitive sensors, seismic sensors, etc. These different sensors may be used together with (e.g., to complement), or in lieu of, eddy current sensor 171 to feed information to the processor 129 about defects that they uncover. The defects may include not only inclusions as noted, but other problems such as subsurface voids (empty regions below the surface of the powder bed 121), or a region of partially sintered or unsintered print material that should otherwise be solidified in the build piece. Capacitive sensors function by detecting changes in the electric field. In some embodiments, capacitive sensors may be placed relatively close to a surface of the powder bed such that a sufficient dielectric can be implemented to allow an alternating source to measure an electric field of the dielectric during operation of the capacitive sensor. Likewise, in practical implementations, the acoustic sensor is placed sufficiently close to the powder bed 121 to render reliable acoustic measurements. Acoustic wave devices or sensors may be integrated in the respective ends of the re-coater, and may use piezoelectric material to apply an oscillating electric field to the powder bed region. Changes can be detected based on changes to the field. Some acoustic sensors rely on changes in audible noise to detect the presence of potential defects or foreign matter.
The support structures 210a-c are not part of the build pieces 208a-c, and may be removed (e.g., via dissolution, controlled physical force, etc.) after the print is completed. Portions of 3D print parts exceeding a certain angle (e.g.,) 45° may require support structures so that the members do not deform due to thermal effects encountered during the 3-D printing process or otherwise lose their dimensional integrity under their own weight. In some printers, portions of a build piece that extend by an amount greater than 45° from a vertical position—such as the horizontally disposed “Region ‘O’” segment of build piece 208c—may require support structures 210a-c to maintain the integrity of the respective build pieces 208a-c. This helps prevent the build pieces from deforming due to lack of sufficient thermal conduction or other forces. In these cases, the supports 210a-c can be removed after printing.
Recoater 201 may receive print material from powder depositor 202, not shown for clarity. Recoater 201 may include a powder outlet 259 for spreading powder during the recoating step. As recoater 201 proceeds towards recoating direction 214 over the powder bed 247, the recoater 201 leaves spread powder 206 in its wake. Recoater blade 204 may level the powder as it is deposited to ensure that the new powder layer is evenly distributed across the powder bed. As in the 3D printer 100 of
3D printer and sensor system 200 further includes sensor arrays # 1 and 2 (216 and 220), which in the present embodiment include eddy current sensors. In various embodiments, sensor arrays 216 and 220 may be, for example, acoustic sensor arrays, capacitive sensor arrays, optical sensor arrays, etc. 3D printer and sensor system 200 also includes a printer housing 255, only a portion of which is shown to avoid unduly obscuring the concepts of the disclosure. Printer housing 255 may, for example, be a portion of a print chamber or outer wall. The interior of printer housing 255 may include an image sensor 242, such as an optical sensor (e.g., a camera or video monitor), an infrared sensor, etc., which may be pivotally or movably affixed on a surface of the inner housing. Image sensor 242 may, like in
Eddy current (EC) sensors, such as in sensor arrays 216 and 220, need not be limited to examining landing areas of ejected matter. EC sensor arrays 216 and 220 may further be configured to detect finer defects on or within the build pieces 208a-c such as very small cracks or voids. In some embodiments, this method may be used to detect the edges of the build piece (including with the assistance of data from the image sensor 242) and to map progress of the build geometry as it evolves during the additive manufacturing process. In this way, digital representations of the geometry of the actual build piece can be generated as the build piece is being printed, e.g., in real or near-real time. These digital representations of the build pieces 208a-c may be matched against the nominal (CAD) geometry, such as that identified in the original CAD models, to ascertain part accuracy data. The digital representations generated by the sensors may also be used in combination with other process knowledge (such as other known contributors to distortion) after removal of support structures 210a-c, heat treatment and machining, etc. Information from, for example, the EC sensors information can be combined or otherwise used with imaging data from the image sensor 242 to further increase quality assurance in additive manufacturing systems. For example, EC sensors can be capable of sensing phenomena below the surface of the build piece and powder layer, and in fact may be able to sense multiple layers below. Because the energy beam may melt not just the powder layer, but also may melt a portion of the previous powder layer(s) or re-melt a portion of one or more previously-fused layers below, the energy beam may cause irregularities in the geometry of the build piece that cannot be determined by sensing the top surface (e.g., with image sensor 242). In this way, for example, a sensor that can sense below the surface of the build piece and/or powder layer(s) may provide valuable additional information that may be used with the information from a sensor that senses the surface.
More generally, sensor arrays 216 and 220 may be positioned and held at a fixed gap relative to the surface of the deposited powder layer for a stable reference position of the sensor arrays. The sensor arrays 216 and 220 in the embodiment of
In some embodiments, sensor arrays, such as recoater-mounted sensor arrays, may include a variety of different types of sensors, e.g. in the dual recoater locations on opposite sides of the blade and deposition mechanism (e.g., arrays 216 and 220). For example, with reference to sensor arrays 216 and 220 of
In various additional embodiments, imaging sensors can be positioned on the recoater 201 as described above, but the image sensor 242 can remain as an additional source of image sensing, which can advantageously be used during the scanning cycle, e.g., to scan for ejected matter and to determine an initial landing location. The various image and non-image sensor circuitry on the recoater 201 can thereafter perform more precise measurements based on the landing location and additional data than any conventional known 3D printers.
For defect detection, the eddy current sensor or other electrical-based sensor can use electrical or magnetic fields (or in some cases applied current) to determine a target impedance in the area of the powder bed 247 or the build piece 208a-c being sensed. The measurement of target impedance may beneficially enable the sensor arrays 216, 220 or processor(s) (e.g., processor(s) 129) receiving the sensor data to determine and account for potentially unexpected discontinuities in the material, which may increase its measured impedance. Thus, by measuring localized impedance to a high enough spatial resolution, the sensor may flag those impedance values outside of an acceptable range as potential discontinuities in a build piece being printed. These discontinuities may then be fixed, especially if crack initiation has begun to occur. With insufficient spatial resolution, computer simulations may be used to determine the expected impedance measurements and flag deviations from this expected value. Thus computer measurements can further increase the precision of the sensors in identifying unwanted artifacts.
The sensing head(s), e.g., sensor arrays 216 and 220, including eddy-current sensing and/or other sensors, may also be used to detect subsurface voids formed in the material. The rapid melting process in metal additive manufacturing can result in voids that form in the lower layers of the part being printed while the outermost surface may appear perfectly smooth. This detection may advantageously anticipate cracks that may form after subsequent thermal cycling/re-melting in the additive manufacturing process.
Thus, for example, image sensor 242 can monitor the progress of the scan and can flag any unusual anomalies, such as spatter material landing in an area of powder to be fused or in an area of the build piece already fused. Eddy current (EC) sensors (e.g., sensor arrays 216 and/or 220) can use this data to identify whether voids may be present in the lower layers. As an example, the processor(s) 129 (
Some 3D printer designs utilize a single recoating (powder deposition) direction and other more efficient designs utilize bi-directional recoating. In the case of single-direction recoating, the recoater 201 may commonly be equipped with two sets of sensing heads (a first set and a second set) on either side of the recoater 201. In this single-direction case, one set of sensing heads (e.g., array 216) is always on the leading edge of recoater 201 as the recoater travels to deposit and spread powder 206. The other set of sensing heads (e.g., array 220) is always on the trailing edge of the recoater, because the recoater deposits powder while traveling in one direction only. In the single direction recoating case, similar to the bi-directional recoating case, the sensors on the re-coater may obtain measurements both before and after powder deposition, because one sensor takes measurements before powder deposition and the other sensor takes measurements after.
Conversely, in the case of bi-directional recoating in which the recoater 201 is equipped with two sets (a first array 216 and a second array 220) of sensing heads on either side of the recoater 201, the first set (array 216) is on the leading edge and the second set (array 220) is on the trailing edge when the recoater travels in one direction to deposit powder, and the first set (array 216) is on the trailing edge and the second set (array 220) is on the leading edge when the recoater 201 travels in the other direction to deposit powder.
One advantage of incorporating the sensing head(s) into the recoater 201 as described in
Recoater 300 includes powder outflow 212, which may correspond to the aperture 177 from which powder can flow in a controlled manner onto the powder bed 121 as the recoater 300 progresses. In some embodiments, recoater 300 can be equipped with a twin recoater blade element or rubber wiper, which may be inserted on the twin recoater blade/wiper base 306 using the blade/wiper recess 308. One leveler 119 (
Eddy current sensor 371 may be integrated as an array of sensors 302 and 304, along with associated sensor circuitry, into respective flat portions 320 and 340 of the recoater 300. The illustrated configuration of
In the embodiments presented heretofore, with the eddy current sensors integrated in the recoater 500, signals may be transmitted and received for producing and sensing eddy currents (e.g., in one embodiment, by powering an electromagnet that sends magnetic fields into the relevant portions of the powder bed to generate eddy currents). It is also necessary to receive signals that can be tracked to determine the value of the fields or the currents at any given time, to thereby determine impedance values and other measurements that may characterize defects in the print job.
A wide variety of possible methods may be available to provide these signals, each of which is intended to fall within the scope of the present disclosure. For example, various such techniques involve retrieving the eddy current sensing head signals out of the build chamber and to a control box, which may either be incorporated as a modular system external to the 3D printers or which may instead be fully embedded outside the build chamber but otherwise connected to the 3D printer. For example, in one such embodiment, a sensor line, e.g. for power, sensing signals, control signals, etc., can include small wires 502 routed along, or hidden within, the build chamber walls 504. This configuration can minimally impact the air flow uniformity in the print chamber required for solid process performance during the print. The wires 502 for the sensor can be routed through a small aperture in the build chamber walls 504 and thereafter into the eddy current sensor. On the other end, the sensor line can be routed to and from the modular system described above. The modular system in this embodiment is outside the build chamber walls and therefore can generate large currents or perform other functions for the eddy current sensor, without disrupting operation of other aspects of the printer.
Over time, the data from both the various sensors can be used to improve build piece accuracy by comparing as-printed geometry to the nominal geometry. This data may be used to determine if any calibration drift has occurred in the scanning system in the additive manufacturing system. Algorithms may be used to enable a better fit of the as-printed geometry to the nominal geometry. Furthermore, this data may eliminate or reduce other costly destructive and non-destructive inspections including mechanical witness specimen tests, coordinate measuring machines (CMMs) or structured light scans for dimensional verification, x-ray computed microtomography (XCT) for material verification, etc., in non-design specific, flexible, fixture-less manufacturing systems that use additive manufacturing and advanced robotic assembly systems. A dimensional verification step of scanning the additively manufactured build piece and comparing it to the nominal CAD geometry may be performed prior to assembly by advanced robotic assembly systems due to the current state of print accuracy (˜1% typical), and a robotic path may be compensated accordingly using such scan information. In other words, a pre-inspection step comprising dimensional verification by scanning the additively manufactured part and comparing it to the nominal CAD geometry prior to assembly may be required to consider the overall part accuracy, resulting from both the printing accuracy and process accuracy (e.g. post-processing, support removal from 3D printed part, etc.). This pre-inspection step can help infer whether a target geometric variation will be achieved or not. These functions can be integrated within the sensors and processors of the 3D printer described herein.
The present disclosure may also yield other advantages for manufacturing techniques that may follow the 3D printing. For example, the 3D printed build piece may subsequently be assembled into a larger part. This larger part may be a vehicle, an aircraft, spacecraft, and another type of transport device. In some cases, the larger part may be a machine that may or may not have any mobility or transport functions. The various sensor data obtained during the 3D printing step can, in various embodiments, be used to streamline the assembly of the 3D printed part, such as when the subsequent assembly is performed at a robotic station. The robotic station may be a cell in the same facility, or it may be off-site. The imaging and non-optical data gathered during 3D printing can be transferred to the robotic assembly station and used to ensure coherent assembly of the 3D printed part, often, but not necessarily, on a fully automated basis. Thus with or without recognized defects, the detailed geometric and compositional data gathered during the 3D printing of the build piece may be invaluable for use by the robotic station in the subsequent assembly.
In various embodiments, incorporating the eddy current sensing systems with the image sensing systems, for example, the data traceable to the build piece in the printer (the part accuracy) may be used to guide robotic path compensation to account for distortion/variation with respect to nominal characteristics of the CAD part model during a subsequent robotic assembly process involving the printed part. This technique is sometimes known as “move, measure, correct.” In these embodiments, the build piece accuracy as tracked by the 3D print sensor data can provide additional detail to a subsequent advanced robotic assembly involving the part, potentially avoiding pre-inspection of the printed part. In short, the data gathered by the sensors during the printing of the build piece may be used in significant applications for characterizing the part after the print.
At 604, the sensor data in the memory (e.g., memory 155) can, after the print, be transferred to a separate robot assembly system prior to assembly of the build piece, e.g., within a vehicle or other mechanized assembly. Thus, for example, the controller bus 174 of
At 606, the data used to determine the accuracy of the 3D print job can also be used to guide installation during the robotic assembly into the larger mechanical structure. This may include using the 3D print data to compensate for prospective deviations from the 3D CAD print model, for example, and the build piece. In various embodiments, all of these techniques can be performed automatedly, without the requirement of manufacturer intervention.
As an example of 606 of
Some of this matter may fall back down into the weld pool and solidify as normal. Other portions of the ejected matter may be so small such that they would be deemed not significant, or at least not of enough volume to cause noticeable flaws in the build piece or performance problems. For example, small, high velocity particles pose a relatively low risk to build quality and are highly likely to be carried away with the gas stream within the build chamber away from the powder bed. A more significant event may be a large spatter particle which may be likely to fall back into the powder bed or build piece. In general, such large spatter may be expected to move slower than the weld pool's movement across the surface of the powder bed.
An even more significant event may occur where this ejected matter particle falls into an area of the build volume occupied by the component being manufactured—namely, the build piece itself. As described above, much of such ejected matter may include (i) various ceramic compounds (carbides, silicides, oxides or nitrides), or (ii) intermetallics of the metallic powder alloy constituents. These categories of ejected matter are likely to be resistant to re-melting and, as such, can potentially create an inclusion. Where an inclusion is present, more likely than not, some amount of powder material underneath the ceramic/intermetallic matter may remain in powder form due to inefficient or no sintering due to the inclusion blocking the laser source. Partially sintered or un-sintered powder material may cause premature failure in the finished product, if left unaddressed.
In short, while some of the high velocity smaller particulates from the weld pool vicinity may be less significant, some of the ejected matter may be big enough and hot enough to have a trajectory sufficient to cause the ejected matter to fall into another portion of the build. The heat carried by the ejected matter can cause damage to the layers or portions of the build piece on which it lands. These types of ejected material can be imaged by the image solutions to determine a trajectory and landing location. Other sensors, e.g., non-optical sensors, or a combination of non-optical sensors, may use this landing information to identify the features of the ejected material, whether the area underneath the landing location is unmelted or partially melted where it otherwise should be a solid portion of the build piece, and other characteristics that may be ideal or a non-optical sensor.
Various embodiments may include tagged monitoring of the area of the weld pool with the eddy current sensing system, an acoustic sensor, etc. for a prescribed number of n build layers. The inclusion can be monitored for evidence of crack initiation. Builds may be stopped or flagged for later repair/inspection as warranted. It may be desirable to continue the print job until more than one, or a number, of defects are identified. That way the 3D printer can efficiently continue without interruption, as the builds are flagged for later repair or further inspection. In some embodiments, processor 129 (
In embodiments where the inclusion is later determined by sensors to be trapped internally in the part, a conduit can be 3D printed as a feature with the part to provide mechanical or fluid access to the inclusion. Referring back to
This 3D printed conduit can enable removal of the inclusion via a mechanical removal (e.g. machining tool or vacuum), or use of chemical agents. Referring briefly to FIG. 2, after the inclusion 293 is removed, the conduit can be filled with the parent material, casting material, or any other suitable material to occupy the void left by the inclusion 293. Conduit 292 may be filled in by 3D printing (e.g., by another 3D printer) in a size that is commensurate with the inclusion 293. 3D printing may be suspended while the conduit 292 is inserted into the powder bed 247 and the inclusion 293 is removed.
In more complex cases where an inclusion is oriented such that it covers unsintered print material that is part of a printed part itself, a conduit can first be 3D printed and used to remove the inclusion 293. The conduit can then be filled with molten print material, or other material in liquid form that solidifies at room temperature and that has features consistent with that of the build piece from which the unmelted powder originated. Additional layers can be added, via the conduit or otherwise, and then melted to reinforce the part, or to substitute for that portion of the build piece that was occupied by the inclusion.
In various embodiments, the sensors may act in concert with the processor(s) and other systems to form a closed repair loop. As shown in
Due to the difference in magnetic properties and the reactions of the ceramic inclusion and metal, the inclusions can be identified based on their permeability and then expelled, using magnetic fields, from the powder bed. Once the inclusions are removed, the magnetic field can be adjusted to increase and excite the metal particles even more, filling the void left by the inclusion as well as any empty space.
The exemplary embodiment of
As noted above, the eddy current settings can be configured to identify defects in the powder bed that may cause a reaction shown by arrows 812a-d to selectively cause the ceramic particles (potential inclusions) with permeability μ2 to be identified distinctly from the powder bed 802. The ejected particles are shown as particles 858. Accordingly, eddy current sensors can be used for both magnetic and paramagnetic materials to selectively identify defects in the powder bed and to fill void regions with print material as needed.
In some embodiments, other tools, including robotic arm 185 (
In various embodiments, additional powder can be laid down or coated, whether as a layer or selectively in different locations of the powder bed 702, after which an additional laser exposure may be used to re-melt the defective areas. Using this technique, build pieces can be strengthened by removing unmelted powder that may be identified by the combined sensor system. In still additional embodiments, the 3D printer's recoating action can also be used to remove spatter of a certain size (such as, for example, a size larger than 60% of the layer thickness), mechanically from the top layer.
In further embodiments, the image sensors can be positioned in a 3D printer in a manner that provides a three-dimensional representation of potential spatter and other defects during the heating of the print material to form the weld pool.
In
Camera two 904 is positioned at an angle of 15° from camera one 902. This is shown by the dashed line of camera two 904 terminating at point P of the powder bed and forming an angle of 15° with the dashed line corresponding to camera one 902. Camera two 904 also has a field of view of angle θ° onto the powder bed 924 extending between points 906b and 906d, as shown by the two intersecting dashed lines at point P labeled 908c on powder bed 924.
In other aspects of the disclosure, 3D printers can be installed with separately, or manufactured and integrated with, combined sensor systems that include special image detector for phenomenon like plumes and spatter. Plumes and spatter are defects that can occur in systems such as selective laser melting (SLM) and similar 3D printers.
In addition to combining types of sensor systems, in one aspect of the disclosure, novel image sensors can be installed with or integrated into 3D printers for providing views with different resolutions and from different angles. In some embodiments, image sensors can be adjusted to differentiate plumes and spatters. A plume can be identified as the gas or the vapor that evolves off the weld pool. Plume and light spatter is generally less important than the heavier spatter, or matter particles that can cause damage to the build piece. In some embodiments, the image sensors are configured such that, while both plume and spatter are imaged, they are imaged in a way that the processor's software can distinguish the two.
The methods in
Beginning at 1102, the recoater of a 3D printer deposits a layer of print material onto a powder bed. At 1104, and as typically performed in between successive deposition cycles of 1102, an energy beam such as a laser beam forms a weld pool that defines portions of the build piece once the weld pool hardens. That is, the laser or other energy beam source heats the intended print material to thereby melt the material so that the material can fuse into an intended portion of the build piece. The beam is configured to avoid striking the layers that do not form parts of the build piece.
At 1106, one or more first sensors—which may include virtually any type of imaging device, whether in the infrared, visible or ultraviolet spectrum, for example, and regardless of whether one or multiple shots are taken, or video streams are taken, or both—determine a landing location of matter that is ejected during the heating of print material to form the weld pool. For example, the first sensors may sense first information, such as optical images of ejected matter, and the processor can determine, based on the first information, a landing location of the ejected matter.
In an exemplary embodiment, the first sensor may include a first camera adjacent a second camera, and at 1112, the sensor may obtain a three-dimensional representation of a trajectory of the ejected matter. Based upon a known orientation, one or more position measurements, or other measurements such as velocity (using a timing measurement), can be taken and provided to the processors or the print controller as data for use in a subsequent closed loop repair process, or in manual repair processes.
At 1108, a second sensor, such as an optical sensor, an acoustic sensor, an eddy current sensor, a capacitive sensor, a seismic sensor, a non-optic sensor, etc., may detect a defect in the build piece based on the determination of the landing location as provided by one or more of the image sensors. The information from the image sensor may, for example, have been forwarded to the processor via memory, and with other known initial conditions or factors, the processor may compute the necessary information. In other embodiments, the landing location is determined directly by the image sensors, and this data is provided promptly to the processors and non-optical sensors for further use.
In some embodiments, the second sensor system, such as the eddy current, may be coupled with the recoater. Thus the sensor system may move the non-optical sensors upon moving the recoater, as described in 1114. Other types of sensors may in some arrangements also be coupled with the recoater. If not directly coupled with the recoater, the sensors may otherwise be designed to keep pace with (or shortly behind) the recoater using an optional mounting feature.
At 1110, the processor receives information from either one or both of the sensors. The information from the image sensor may include velocity information or other information that may have been computed at the sensor. In other embodiments, the processor performs calculations based on the received images. The information from the eddy current sensor, for example, may include the magnitudes of the eddy currents, the amplitudes and directions of the generated magnetic (or electric) fields, impedances computed based on the generated fields and currents, and other values relevant to the defects. That is, in 1118, additional sensors may be configured to measure information about defects in the build piece and may provide the additional necessary information about the defects to the processor(s).
At 1120, the 3D printer may modify the printing of the build piece based on the received information. For example, in one embodiment, the 3D printer may be configured to 3D print a mark, tag, number or flag on a portion of the build piece that has a defect, so that the defect can be addressed at a subsequent time. In other embodiments discussed above, the 3D printer may suspend printing, repair the defect promptly, and then resume printing.
At 1124, the 3D printer modifies the printing. In various embodiments, the 3D printer may modify the printing, e.g., at or near the landing location of the ejected matter based on the information received from the sensors. In various embodiments, the 3D printer may take other action such as stopping the build, such as at 1199. Thus a closed loop system can be achieved to repair or take other action. At 1122, the 3D printer may print into the build piece a conduit, as discussed above with as a brush, blade, drill, sander, polisher, or other machining device of the 3D printer to perform the correction.
Based upon the complementary information retrieved by more than one sensor type, the 3D printer may have significant advantages reference to
At 1206, the 3D printer system may sense first information with a first sensor, such as an image sensor, for example. Based on the first information, the 3D printer system may determine a landing location of matter ejected during the heating of print material to form the weld pool, such as shown in 1208. Having determined the location of the matter, the 3D printer system can then use a sensor to sense second information based on the landing location (1210). The sensor may be the image sensor, or it may be an eddy current sensor, etc. At 1212, the 3D printer system, based on the sensed information and the determination of the landing location, may detect a defect in the build piece. Various remedial measures may be taken by the 3D printer system at that point as described in detail herein, or in other cases, the information may just be report for later use.
The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these exemplary embodiments presented throughout this disclosure will be readily apparent to those skilled in the art. Thus, the claims are not intended to be limited to the exemplary embodiments presented throughout the disclosure, but are to be accorded the fu011 scope consistent with the language claims. All structural and functional equivalents to the elements of the exemplary embodiments described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 U.S.C. § 112(f), or analogous law in applicable jurisdictions, unless the element is expressly recited using the phrase “means for” or, in the case of a method claim, the element is recited using the phrase “step for.”
This application claims the benefit of and right of priority to U.S. Provisional Patent Application No. 63/080,621, entitled “Realtime Quality Assurance Suited For High-Throughput Additive Manufacturing via Re-coater Mounted Sensing Systems”, filed Sep. 18, 2020, the contents of which are hereby incorporated by reference as if expressly set forth herein.
| Number | Date | Country | |
|---|---|---|---|
| 63080621 | Sep 2020 | US |
