Closed-Loop Automatic Setting Adjustments for Additive Manufacturing Based on Layer Imaging

Abstract

A fabrication of a build structure by an additive layer manufacturing machine is assessed and controlled. A first portion of a first material is selectively heated to form a first formed layer of the build structure having a first thickness. An image of a predefined region of the first formed layer is generated. The image depicts topographical characteristics within the predefined region of the first formed layer. A subsequent portion of the first or a second material is selectively heated to form a subsequent formed layer of the build structure attached to the first formed layer. The subsequent formed layer has a second thickness that correlates with the depicted topographical characteristics.

Claims

1. A method of assessing and controlling a fabrication of a build structure by an additive layer manufacturing machine, comprising the steps of: setting a first layer of a first material over a substrate, an entirety of the first layer of the first material when set over the substrate having a first height in a first direction orthogonal to a plane defined by the substrate; selectively heating the first layer of the first material with a first high energy beam to form a first formed layer of a build structure; generating a first image of a predefined region of the first formed layer, the first image depicting one or more topographical characteristics within the predefined region of the first formed layer; setting a subsequent layer of the first material or a second material different from the first material over the first formed layer, an entirety of the subsequent layer having a second height different from the first height in the first direction, the second height being determined based on the depicted topographical characteristics; and selectively heating the subsequent layer with the first high energy beam or a second high energy beam to form a subsequent formed layer of the build structure over the first formed layer.

2. The method of claim 1, wherein the one or more depicted topographical characteristics result from applied energy magnitudes of energy applied by the first high energy beam within the predefined region of the first formed layer.

3. The method of claim 1, wherein the substrate is a platform moveable relative to a fixed platform, and further comprising the steps of: lowering the substrate a first distance relative to the fixed platform to a first position, the substrate being at the first position during the steps of setting the first layer of the first material over the substrate and selectively heating the first layer of the first material over the substrate; and lowering the substrate a second distance relative to the fixed platform and different from the first distance to a second position, the substrate being at the second position during the steps of setting the subsequent layer over the first formed layer and selectively heating the subsequent layer over the first formed layer.

4. (canceled)

5. The method of claim 1, wherein the first high energy beam is directed from a first energy beam source having a first energy beam setting during the step of selectively heating the first layer of the first material, further comprising the step of: altering the first energy beam setting of the first energy beam source to a second energy beam setting of the first energy beam source based on the first image, wherein the first high energy beam is directed from the first energy beam source having the second energy beam setting during the step of selectively heating the subsequent layer.

6. The method of claim 51, wherein the first high energy beam is directed from a first energy beam source having a first power during the step of selectively heating the first layer and the second high energy beam is directed from the first energy beam source or a second energy beam source during the step of selectively heating the subsequent layer and having a second powers during the step of selectively heating the subsequent layer.

7. The method of claim 1, wherein the first high energy beam is directed from a first energy beam source having a first scan speed setting corresponding to a first scan speed of the first high energy beam during the step of selectively heating the first layer and the second high energy beam is directed from the first energy beam source or a second energy beam source, the second high energy beam having a second scan speed setting corresponding to a second scan speed of the second high energy beam during the step of selectively heating the subsequent layer.

8. The method of claim 1, wherein the first high energy beam is directed from a first energy beam source having a combination of a first scan speed setting corresponding to a first scan speed of the first high energy beam and one or more first power input settings corresponding at least in part to a first power provided by the first energy beam source during the step of selectively heating the first layer, and wherein the second high energy beam is directed from the first energy beam source or a second energy beam source, the second high energy beam having a combination of a second scan speed setting corresponding to a second scan speed of the second high energy beam and one or more second power input settings corresponding at least in part to a second power provided by the one of the first energy beam source or the second energy beam source from which the second high energy beam is directed during the step of selectively heating the subsequent layer.

9. The method of claim 1, wherein the first high energy beam is directed from a first energy beam source having a first energy beam setting during the step of selectively heating the first layer and the second high energy beam is directed from the first energy beam source or a second energy beam source during the step of selectively heating the subsequent layer, further comprising the steps of: comparing, automatically via a computer processor, a first image intensity value corresponding to one of the one or more depicted topographical characteristics within a first predefined area of the first image to a first preset intensity value; and setting, automatically via a computer processor, the second energy beam setting based on a difference between the first image intensity value and the first preset intensity value.

10. The method of claim 1, wherein the first high energy beam is directed from a first energy beam source having a first energy beam setting during the step of selectively heating the first layer and the second high energy beam is directed from the first energy beam source or a second energy beam source during the step of selectively heating the subsequent layer, further comprising the steps of: determining, automatically via a computer processor, a first image intensity value corresponding to one of the one or more depicted topographical characteristics within a first predefined area of the first image; and setting, automatically via a computer processor, the second energy beam setting based on the first image intensity value.

11-16. (canceled)

17. The method of claim 1, further comprising the steps of: comparing, automatically via a computer processor, a first image intensity value corresponding to one of the one or more depicted topographical characteristics within a first predefined area of the first image to a first preset intensity value; and setting, automatically via a computer processor, the second height based on a difference between the first image intensity value and the first preset intensity value.

18. The method of claim 1, further comprising the steps of: determining, automatically via a computer processor, a first image intensity value corresponding to one of the one or more depicted topographical characteristics within a first predefined area of the first image; and setting, automatically via a computer processor, the second height based on the first image intensity value.

19. The method of claim 1, wherein the step of setting the first layer of the first material over the substrate includes setting the first material over a prior layer or prior layers of additional material overlying the substrate.

20-23. (canceled)

24. A method of assessing and controlling a fabrication of a build structure by an additive layer manufacturing machine, comprising the steps of: selectively heating a first portion of a first material to form a first formed layer of a build structure having a first thickness as measured in a first direction; generating a first image of a predefined region of the first formed layer, the first image depicting one or more topographical characteristics within the predefined region of the first formed layer; and selectively heating a subsequent portion of the first material or a second material different from the first material to form a subsequent formed layer of the build structure attached to the first formed layer, the subsequent formed layer having a second thickness as measured in the first direction, wherein the second thickness correlates with the depicted topographical characteristics.

25. The method of claim 24, wherein the one or more depicted topographical characteristics result from applied energy magnitudes of energy applied by a first high energy beam within the predefined region of the first formed layer.

26. The method of claim 24, further comprising the steps of: comparing, automatically via a computer processor, a first set of image intensity values corresponding to respective ones of the depicted topographical characteristics within respective ones of a first set of predefined areas of the first image to a corresponding first set of preset intensity values, wherein the first set of predefined areas of the first image correspond to respective portions of the predefined region of the first formed layer; and setting, automatically via a computer processor, a height of the one of the first material or the second material based on a first set of differences between the respective ones of the first set of image intensity values and the first set of preset intensity values, wherein the second thickness results from the set height.

27. The method of claim 26, further comprising setting the height based on a statistical average of the first set of differences.

28. (canceled)

29. The method of claim 24, wherein the step of selectively heating the first portion of the first material is a step of selectively heating a first layer of the first material with a first high energy beam and the step of selectively heating the subsequent portion of the first material or the second material is a step of selectively heating a subsequent layer of the first material or the second material with the first high energy beam or a second high energy beam, wherein the first high energy beam is provided by a first energy beam source having a first set of energy beam settings to form the first formed layer of the build structure, the first set of energy beam settings controlling a first set of properties of the first high energy beam, and wherein the second high energy beam is provided by the first energy beam source having a second set of energy beam settings or a second energy beam source having the second set of energy beam settings when the subsequent formed layer is formed by the second high energy beam, the second set of energy beam settings controlling a second set of properties of the second high energy beam when the subsequent formed layer is formed by the second high energy beam, the first set of properties being the same types of properties as the second set of properties.

30. The method of claim 29, wherein the first set of energy beam settings include a first set of power input settings of the first energy beam source and the second set of energy beam settings include a second set of power input settings of the respective one of the first energy beam source and the second energy beam source with which the subsequent formed layer is selectively heated, and wherein each of the first set of power input settings are set for selectively heating respective predefined portions of the first layer during the formation of the first formed layer of the build structure and corresponding ones of the second set of power input settings are set, during the formation of the subsequent formed layer of the build structure, for selectively heating respective predefined portions of the subsequent layer corresponding to the predefined portions of the predefined region of the first formed layer, and further comprising setting at least one of the second set of power input settings based on the depicted topographical characteristics such that the at least one of the second set of power input settings is different from the corresponding one of the first set of power input settings.

31. The method of claim 29, wherein the first set of energy beam settings control a first scan speed of the first high energy beam and the second set of energy beam settings control a second scan speed of the respective one of the first high energy beam and the second high energy beam with which the subsequent formed layer is selectively heated, wherein the second scan speed is based on the depicted topographical characteristics such that the second scan speed is different from the first scan speed, and wherein the step of selectively heating the first layer of the first material includes scanning the first layer of the first material at the first scan speed, and wherein the step of selectively heating the one of the subsequent layer of the first material and the first layer of the second material includes scanning the respective one of the first high energy beam and the second high energy beam with which the subsequent formed layer is selectively heated at the second scan speed.

32-35. (canceled)

36. The method of claim 24, wherein the formed first layer is an initial formed layer of the build structure or an intermediate formed layer of the build structure.

37. The method of claim 24, wherein the subsequent layer is formed directly on the first formed layer.

38. (canceled)

39. (canceled)

40. A method of assessing and controlling a fabrication of a build structure by an additive layer manufacturing machine, comprising the steps of: setting a first layer of a material onto or over a substrate, an entirety of the first layer of material having a first height as measured in a first direction; selectively heating the first layer of the material with a first high energy beam to form a first formed layer of a build structure; setting a second layer of the material onto the first formed layer, an entirety of the second layer of the material having the first height in the first direction; setting a further layer of the material onto or over the second layer of the material without directing a high energy beam onto the second layer, an entirety of the further layer of the material having the first height in the first direction; selectively heating the further layer of the material with the first high energy beam or a second high energy beam to form a subsequent formed layer of the build structure attached to the first formed layer.

41. (canceled)

42. (canceled)

43. The method of claim 40, wherein the first height corresponds to a slice of a computer-aided design (CAD) model of the build structure.

44-47. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0066] A more complete appreciation of the subject matter of the present invention and various advantages thereof may be realized by reference to the following detailed description, in which reference is made to the following accompanying drawings, in which:

[0067] FIG. 1 is a schematic illustration of an additive manufacturing device in accordance with an embodiment;

[0068] FIGS. 2A-2C are cross-sectional views of a build chamber showing a fabrication of a set of constructs in accordance with an embodiment; and

[0069] FIGS. 3 and 4 are process flow diagrams of processes for assessing and controlling the fabrication of a build structure by an additive layer manufacturing machine in accordance with separate embodiments.

DETAILED DESCRIPTION

[0070] Referring to the drawings, as shown in FIG. 1, additive manufacturing (AM) device 1 includes laser beam generation apparatus 10, but a device consistent with the present disclosure may be one configured with an electron beam generation apparatus that generates an electron beam, as described for example in U.S. Patent Application Publication No. 2020/0023435 A1, the entire disclosure of which is hereby incorporated by reference herein, or may be embodied in other forms and should not be construed as being limited to the embodiments set forth herein. In the example shown, laser beam generation apparatus 10 generates laser beam 15 and is at least partially contained in vacuum chamber 40 which maintains a substantially vacuum environment. While part of apparatus 10 may be positioned outside chamber 40 for access and electrical connectivity, the beam generation apparatus is configured for generating and transmitting laser beam 15 within the vacuum environment, as well as for directing the beam towards powder bed 53.

[0071] AM device 1 further includes, among other components as well-known to those skilled in the art, build platform 50, powder deposition system 30, one or more sensors 70, monitoring controller 72, and machine process controller 20. Build platform 50 supports substrate 51 during a build of a construct, e.g., a medical implant. In operation, a layer of material, which may be conductive powder 33 gathered to form powder bed 53, is placed upon substrate 51 and selectively heated to form one layer of the construct to be formed. Upon the completion of heating of the one layer of the construct, build platform 50 moves downward within a build chamber to allow a successive power bed layer to be deposited onto the newly completed layer by powder deposition system 30. In this manner, as further shown in FIG. 1, successive fused layers 52 are formed over substrate 51 supported by build platform 50 until the construct to be formed is completed.

[0072] More specifically, in this example, a three-dimensional (3D) construct is formed by progressively melting conductive powder 33 to form liquid melt zone 54 and cooling the melt zone into fused layers 52 on substrate 51. Liquid melt pool 54 is formed by selectively beam-melting powder 33, e.g., suitable powder such as but not limited to titanium, titanium alloys, stainless steel, cobalt chrome alloys, gold, silver, tantalum, and niobium. Powder deposition system 30 includes powder container 32 which stores powder 33 and powder feeder 31 which uniformly deposits the powder, e.g., with a rake or a roller or other suitable powder delivery mechanisms having a controlled speed, on top of substrate 51 for the first layer 52 and then onto previous layers 52 for successive powder depositions. In this example, powder feeder 31 obtains powder 33 from powder containers 32 on opposite sides of substrate 51. While not shown in FIG. 1 for simplicity, vacuum chamber 40 may be evacuated using a vacuum subsystem, e.g., turbo-molecular pump, ducts, valves etc., as understood by those skilled in the art. Sintering or full melting of powder 33 may be carried out based on a set of design data, e.g., computer-aided design (CAD) data or other 3D design files, imported to process controller 20. In some arrangements, the 3D design data is divided into a set of successive 2D cross-sections, e.g., slices, by process controller 20 to create design data usable for the fabrication process or is provided to the process controller already divided into such slices. According to the information contained in the design data useable for the fabrication process, process controller 20 commands beam generation apparatus 10 to direct laser beam 15 towards processing area A and thereby sinter or fully melt selective regions on powder bed 53 by setting suitable process parameters on beam generation apparatus 10.

[0073] Still referring to FIG. 1, in providing an in-situ process monitoring and control system for AM device 1, process controller 20 may be electrically connected to one or multiple sensors 70, as in the example shown, to detect and measure one or more specific process features of interest of powder bed 53 and liquid melt zone 54. The information received by sensors 70 corresponding to the process features of interest is relayed to monitoring controller 72, which is connected to process controller 20 as a set of sensor data 71. Monitoring controller 72 receives, and in some arrangements stores within computer memory of the monitoring controller, sensor data 71 and performs one or more algorithms, represented collectively as algorithm 100 in FIG. 1, to interpret the sensor data relative to user-defined parameters.

[0074] Monitoring controller 72 transmits electrical signals to process controller 20 to modify process parameters 21-24 for AM device 1 as needed. For example, monitoring controller 72 may transmit electrical signals to process controller 20 to either one or both of alter the powder deposition rate of powder feeder 31 and laser beam properties by modifying the settings of beam generation apparatus 10.

[0075] Monitoring controller 72 may be configured to operate as an integrating system which consists of components responsible for process data collection, storage, interpretation, comparison, and information or instructional digital signal generation. High-speed data acquisition boards may be used for real-time acquisition of large volumes of process data associated with a high-speed time-series feedback signal and digital images, e.g., those generated by a thermal imaging device. Monitoring controller 72 may include sufficient read only memory (ROM), random access memory (RAM), electronically-erasable programmable read only memory (EEPROM), etc., of a size and speed sufficient for executing algorithm 100 as set forth below. Monitoring controller 72 may also be configured or equipped with other required computer hardware, such as a high-speed clock, requisite analog-to-digital (A/D) and digital-to-analog (D/A) circuitries, any necessary input or output circuitries and devices (I/O), as well as appropriate electrical signal conditioning and/or buffer circuitry. Any algorithms resident in AM machine 1 or accessible thereby, including algorithm 100, as described below, may be stored in memory and automatically executed to provide the respective functionality.

[0076] In the example shown in FIG. 1, algorithm 100, which may be embodied as a single algorithm or multiple algorithms, is automatically executed by monitoring controller 72 to interpret sensor data 71 and by process controller 20 on AM device 1 to modify process parameters during the AM process. Interpretation of sensor data 71 by monitoring controller 72 identifies an appropriate action to be taken and determines input parameters 73, which may be transmitted as a set of input parameters, to be sent from monitoring controller 72 to process controller 20, needed to modify process settings, in order to maintain part quality and process efficiency, in which in some arrangements such settings may be limited by preset limits stored in the monitoring controller or the process controller. Process controller 20 transmits electrical signals corresponding to process parameters 21-23 to beam generation apparatus 10 to modify settings of the beam generation apparatus and transmits electrical signals corresponding to process parameter 24 to powder deposition system 30 to modify settings of the powder deposition system. In this manner, a closed-loop process feedback control is formed between monitoring controller 72, working with process controller 20, and system components, e.g., beam generation apparatus 10, powder deposition system 30, etc., of AM device 1 to allow for a real-time modification to final control parameters 21-24.

[0077] The process features of interest to be monitored across the processing area, as indicated by arrow A in FIG. 1, during the AM process are associated with one or more sensors 70. In some arrangements, sensors 70 may be integrated into AM device 1 and operated independently or in combination with each other depending on the particular application. As further shown in FIG. 1, in some arrangements, one or more of sensors 70 may be mounted inside vacuum chamber 40. In some arrangements, sensors 70 may be one or multiple thermal imaging devices, which may be thermographic cameras, e.g., infrared cameras Images obtained from thermal imaging devices may correspond to any one or any combination of a temperature of powder bed 53, a temperature of liquid melt zone 54, a temperature of solidified melted surface 65.

[0078] Referring now to FIGS. 2A-2C, in one example which is not to be construed as limiting, first layer 152A of powder 33 having a first thickness is deposited on substrate 151 supported by build platform 50 and then selectively melted to form first formed layers 155A of a set of constructs to be prepared. In this example, three separate constructs are being prepared simultaneously. A thermal image of one or all of first formed layers 155A is taken and digitized into thermal imaging data 71 by thermal imaging device 70.

[0079] In some arrangements, the thermal image is taken of a predefined region, or preferably the entirety of, first formed layers 155A and remaining unmelted powder 33 from first layer 152A at a predetermined time, which may be for example following the completion of the first formed layers and prior to the deposition of second layer 152B of powder 33. Thermal imaging data 71 associated with the entirety of first formed layers 155A and remaining unmelted powder 33 from first layer 152A is received by monitoring controller 72 and stored in a data logger of, or in electrical communication with, the monitoring controller.

[0080] Monitoring controller 72 may convert thermal imaging data 71 into a greyscale image and generate a first matrix of a first set of image intensity values, corresponding to depicted topographical characteristics detected by the thermal imaging data across the imaged area, according to individual pixels in the image in which the pixels are assigned a value of 0-255 based on RGB values as known to those skilled in the art. In this example, each pixel is located at a discrete location within the image that is the size of the individual pixel. Variations in the depicted topographical characteristics and thus variations in the image intensity values of the first set of image intensity values derived from thermal imaging data 71 result from variations in topographical characteristics of formed layers caused by variations in applied energy magnitudes of energy applied by beam 15 in forming an imaged formed layer. The first set of image intensity values are then compared by the monitoring controller using algorithm 100 or portion, i.e., steps, of algorithm 100, such as by a digital comparator, to a first set of preset intensity values within a second matrix assigned to a corresponding location within the first matrix associated with each of the first set of image intensity values. In some arrangements, the second matrix also may be stored in the data logger of the monitoring controller. The locations within the first matrix may correspond to the locations of the pixels within the image. The first set of preset intensity values may be values assigned according to the locations at which the next powder layer is to be selectively heated, in this example melted. In some arrangements, the first set of preset intensity values may be determined and stored in monitoring controller 72 based on empirical data derived through prior fabrications of the constructs to be prepared. Based on the comparisons between the first set of image intensity values and the first set of preset intensity values, monitoring controller 72 may determine a percentage increase or decrease in beam energy needed within horizontal locations, i.e., locations within an area parallel to substrate 51, of the subsequent build layer corresponding to the respective horizontal locations within first formed layers 155A and remaining unmelted powder 33 from first layer 152A to which the pixels of the greyscale image are associated. In this manner, less energy may be applied to areas that may be subjected to otherwise relatively high applied energy magnitudes to avoid part deformation or other non-compliant part or process characteristics while more energy may be applied to areas that may be subjected to otherwise relatively low applied energy magnitudes in order to ensure adequate melting to prevent porosity caused by a lack of melt pool formation in desired areas. Applying less energy through either one or both of an increase in scan speed and an increase in hatch spacing may decrease processing time and thereby increase production throughput.

[0081] In some arrangements, if an image intensity value for one horizontal location falls below a low threshold for that location or exceeds a high threshold for that location, then the high energy beam may be applied with a corresponding higher or lower relative energy density. In some such arrangement, if an image intensity value for one horizontal location or for another set number of horizontal locations falls outside of a range that includes the low and the high thresholds for that location, the monitoring controller may instruct the AM machine to stop the fabrication of constructs that is in process.

[0082] Once the percentage increase or decrease in beam energy is determined, monitoring controller 20 sends input parameters 73 to process controller which in turn determines process parameters 21-23 to be sent to beam generation apparatus 10 in order to modify settings of beam generation apparatus 10 for the selective melting of the subsequent build layer. Process parameters 21-23 may include beam power 21, scan speed 22, or another parameter 23, e.g., hatch spacing, affecting beam generation apparatus 10. In this manner, in some arrangements, beam generation apparatus 10 may apply laser beam 15 either one or both with more or less power and at greater or lesser scan speeds at predefined regions of the subsequent build layer. For example, the beam power may be set at 100 W with a scan speed of 500 mm/s at a first horizontal location in forming first formed layers 155A and a beam power set at 200 W with a scan speed of 200 mm/s at a second horizontal location in forming first formed layers 155A. Based on the image intensity values of the first and second locations from the image taken by thermal imaging device 70 and the given preset intensity values at these locations, monitoring controller 72 may provide input parameters 73 to process controller 20 which in turn may determine appropriate process parameters 21-23 to direct beam generation apparatus 10 to apply beam 15 with a power of 75 W and a scan speed of 400 mm/s at the first horizontal location and a power of 250 W and a scan speed of 250 mm/s at the second horizontal location in forming second formed layers 155B. In the same manner, each subsequent layer of powder may be imaged immediately following the processing of each such layer and thermal imaging data derived from those images may be used by monitoring controller 72 to determine input parameters 73 for process controller 20 such that the controllable beam settings, e.g., beam power and scan speed, at various locations for successive layers are altered based on the images taken to lower beam energy applied to areas that may be subjected to otherwise relatively high applied energy magnitudes to avoid part deformation or other non-compliant part or process characteristics while raising beam energy applied to areas that may be subjected to otherwise relatively low applied energy magnitudes in order to ensure adequate melting to prevent porosity caused by a lack of melt pool formation in desired areas.

[0083] With reference to FIG. 2B, based on the comparisons between the first set of image intensity values corresponding to depicted topographical characteristics derived in forming first formed layers 155A and the first set of preset intensity values, a thickness of second layer 152B of powder 33 to be deposited on the remaining powder of first layer 152A and first formed layers 155A also may be altered automatically by instructions 24 in the form of electrical signals sent from process controller 20 to deposition system 30 of AM device 1. In the example shown, based on the comparisons, process controller 20 instructed deposition system 30 to have powder container 32 deposit a thicker layer of powder 33 for second layer 152B than was deposited for first layer 152A. Similarly, and with particular reference to FIG. 2C, second formed layer 155B may be imaged by thermal imaging device 70 and then each of additional layers 152C-152F of powder 33 may be deposited and formed additional layers 155C-155E may be imaged successively before subsequent such layers are deposited such that the thicknesses of such additional layers 152C-152F may be set appropriately based on the image intensity values determined by monitoring controller 72. As shown, the thicknesses of each deposited layer 152A-152F may vary from one or more other ones of such deposited layers.

[0084] In some arrangements, to determine the thicknesses of subsequent layers of powder, such as second layer 152B and additional layers 152C-152F, a portion, i.e., additional steps, of algorithm 100 may be applied by monitoring controller 72 based on thickness input parameters. Such thickness input parameters always include a value associated with a thickness of a feature that will be formed in part by the subsequent layer being deposited and may include values corresponding to any one or any combination of beam power, beam scan speed, and beam hatch spacing, and the thickness of the layer of powder 33 just deposited. In some arrangements, which may be fully autonomous arrangements, thicknesses of each subsequent layer, e.g., layers 152B-152F, used in forming complete constructs, may be determined automatically by monitoring controller 72. In some arrangements, which may be semi-autonomous arrangements, thicknesses of some subsequent layers, e.g., some of layers 152B-152F, may be determined automatically by monitoring controller 72 while the thicknesses of other layers, such as the thicknesses of other layers of layers 152B-152F not determined automatically, may be preset by a programmer prior to the fabrication of the constructs. In some such arrangements, thermal imaging device 70 may be programmed not to take images of one or more formed layers when the thicknesses of the successive layers of such one or more formed layers is preset. However, thermal imaging device 70 may still take an image of any formed layer if a thickness of its successive layer is preset in some arrangements, such as when the image may be used for altering of controllable beam settings as described previously herein. In some fully manual thickness arrangements, the thicknesses of each of the deposited layers, e.g., layers 152B-152F, of powder 33 may be preset prior to the fabrication of the constructs. In such arrangements, thermal imaging device 70 may not be employed or may be employed for other purposes, such as for the alteration of the controllable beam settings. In any of these arrangements, preset thicknesses may be programmed based on empirical data from prior builds, experimentation, modeling data, or other methodologies.

[0085] In some arrangements, any one or any combination of the controllable beam settings, e.g., beam power, scan speed, hatch spacing, may be altered for all areas of a subsequent layer to be formed based on the image intensity values determined from the prior layer. In still further arrangements, the controllable beam settings as well as the thickness of the powder layer to be deposited for the subsequent layer to be formed may be altered based on the image intensity values determined from the prior layer. In some arrangements, only the thickness, and not any of the controllable beam settings or other parameters of beam generation apparatus 10, may be altered for the subsequent layer based on the image intensity values determined from the prior layer. It is to be understood that the ability to modify the controllable beam settings and the thicknesses of layers during a build process can also be useful in compensating for deterioration of aspects of AM device 1, e.g., laser beam degradation over time, small gas leaks, substrate deterioration, and other wear issues. In this manner, this ability prolong the period before maintenance of AM device 1 is needed and thereby reduce downtime and may even prolong the useful life of the AM device.

[0086] Referring now to FIG. 3, a fabrication of a build structure by an additive layer manufacturing machine may be assessed and controlled in a process 280. In a step 282 of process 280, a first layer of a first material having a first height may be set, e.g., deposited, over, and in some arrangements onto, a substrate of an additive manufacturing machine. In a step 284, the first layer of the first material may be selectively heated with a first high energy beam to form a first formed layer of the build structure. In a step 286, a first image of a portion or of an entirety of the first formed layer may be generated to identify one or more applied energy magnitudes within the respective portion or entirety of the first formed layer. In a step 288 which is repeated until the last layer is set, a subsequent layer or further subsequent layer of first material or second material may be set, e.g., deposited, over the first formed layer and any previous formed layer and have a respective height based on the depicted topographical characteristics. In a step 290 which is repeated until completion of the build structure, the subsequent layer may be selectively heated with the first or a second high energy beam to form a subsequent formed layer or a further formed layer. In a step 292, a subsequent image of a portion or an entirety of a subsequent formed layer just selectively heated may be generated to depicted topographical characteristics with the subsequent formed layer just selectively heated. Once the build structure is complete at step 290, at step 295, the completed build structure may be removed from the additive manufacturing machine, and if necessary, post-processed, e.g., either one or both of heat treated and polished.

[0087] Referring now to FIG. 4, in a similar arrangement, a fabrication of a build structure by an additive layer manufacturing machine may be assessed and controlled in a process 380. In a step 382 of process 380, a first layer of a material having a first height may be set, e.g., deposited, over, and in some arrangements onto, a substrate of an additive manufacturing machine. In a step 384, the first layer of the material may be selectively heated with a first high energy beam to form a first formed layer of the build structure. The first formed layer may have a first thickness. In a step 386, a first image of a portion or of an entirety of the first formed layer depicting one or more topographical characteristics within the respective portion or entirety of the first formed layer may be generated. As described previously herein, in some arrangements, the one or more depicted topographical characteristics may result from applied energy magnitudes of energy applied by the first high energy beam. In a step 388 which is repeated until the last layer or set of layers of the build structure to be selectively melted is set, a subsequent layer or set of subsequent layers of the material may be set, e.g., deposited, over the first formed layer and any previous formed layer. The subsequent layer or each subsequent layer of the set of subsequent layers of the material may have the first height such that a height of the set of subsequent layers of the material may be a multiple of the first height. For example, the first layer of material may be set with a height of 25 mm and each subsequent layer may be set with a height of 25 mm such that a set of three subsequent layers of the material has a height of 75 mm. In some arrangements, this height may correspond to a slice of a computer-aided design (CAD) model of the build structure used in preparing a file for use by the additive manufacturing machine, e.g., .STL or g-code files.

[0088] In a step 390 which is repeated until completion of the build structure, the subsequent layer or set of subsequent layers may be selectively heated with the first or a second high energy beam to form a subsequent formed layer or a further formed layer. In this setup, only the last layer of a set of subsequent layers of material is selectively heated by the high energy beam and the high energy beam is not directly applied onto the prior layers of the set of subsequent layers set during step 388. The subsequent formed layer may have approximately the same thickness as the first formed layer or a second thickness, e.g., one that is a multiple of the first thickness when the subsequent formed layer is formed from a set of subsequent layers of material having a height that is a multiple of the first height. In a step 392, a subsequent image of a portion or an entirety of a subsequent formed layer just selectively heated and layer depicting one or more topographical characteristics within that layer may be generated. Once the build structure is complete at step 390, at step 395, the completed build structure may be removed from the additive manufacturing machine, and if necessary, post-processed, e.g., either one or both of heat treated and polished.

[0089] In some alternative arrangements, any one of the subsequently deposited layers of material used in the fabrication of the build structure may be selectively heated by a second energy beam rather than the first energy beam used to heat the first layer of a build construct. In operation, the second energy beam may be controlled by process controller 20 or may be controlled by a second process controller in the same manner as the first energy beam 15 such that the applied energy onto a build layer from the second energy beam may be based on depicted topographical characteristics determined for a prior layer as well as other preset process parameters as described previously herein.

[0090] In some alternative arrangements, any one of the subsequently deposited layers of material used in the fabrication of the build structure may be made of a different material than the deposited material used for a prior layer where fabrication of such different material is compatible with the material used in the prior layer and the fabrication and use of such material in the prior layer. For example, the material used for one layer may be titanium or a titanium alloy while the material used for an immediately subsequent layer may be silver or a silver alloy. In such arrangements, powder deposition system 30 may include multiple powder containers 32 in which each container may contain a different powder than another one of the powder containers.

[0091] In some alternative arrangements, polymeric, other plastic materials, ceramic, cermet, or other suitable materials may be employed in conjunction with an AM device in which either one or both of beam parameters such as beam power and beam scan speed may be altered within one region of a layer and from layer to layer based on thermographic images and powder thickness may be altered from one layer to the next as described previously herein.

[0092] In some alternative arrangements in which multiple thermographic cameras 70 are used, each camera may take images of only a portion of a processing area. Thermal imaging data 71 from each camera may be received by monitoring controller 72 to determine intensity values associated with the imaged area that are to be compared to the preset intensity values.

[0093] In other embodiment, AM device 1 may be replaced by a device providing MHD drop-on-demand ejection and liquid droplet deposition on a moving substrate, such as the MagnetoJet printing process commercialized by Xerox Corporation. This system is described for example in Sukhotskiy, et al., “Liquid Metal 3D Printing,” Flow-3D: Solving the World's Toughest CFD Problems, the disclosure of which is hereby incorporated herein by reference. In such an embodiment, one or more layers, and preferably each of the layers, deposited by the MHD device may be imaged, such as by thermal imaging device 70. Based on the thermal imaging data, in an analogous manner to monitoring controller 72 and process controller 20 of AM device 1, one or more controllers of the MHD device may direct changes to the process parameters of the MHD device. For example, the one or more controllers of the MHD device may direct more or less current through coil windings of the MHD device through which metal feedstock, e.g., wire from an aluminum spool, is fed in order to apply more or less relative energy in the form of heat to the metal feedstock. In another example, the one or more controllers of the MHD device may direct more or less current through coils extending along a substrate onto which a build structure is built such that the substrate applies more or less heat to the build structure. In still another example, the one or more controllers of the MHD device may direct the deposition of a greater amount of droplets at a time while building the build structure or a different amount of feedstock to be heated a given time. Any of these options may be applied in combination with any of the other options for any given layer, whether based on a digital image taken during production or programmed pre-production. In this manner, part quality and production efficiency may be improved.

[0094] It is to be understood that the disclosure set forth herein includes any possible combinations of the particular features set forth above, whether specifically disclosed herein or not. For example, where a particular feature is disclosed in the context of a particular aspect, arrangement, configuration, or embodiment, that feature can also be used, to the extent possible, in combination with and/or in the context of other particular aspects, arrangements, configurations, and embodiments of the invention, and in the invention generally.

[0095] Furthermore, although the invention disclosed herein has been described with reference to particular features, it is to be understood that these features are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention. In this regard, the present invention encompasses numerous additional features in addition to those specific features set forth in the claims below.