3D additive manufacturing apparatus, manufacturing surface monitoring method, and information processing program

Abstract

Provided is a three-dimensional additive manufacturing device that makes it possible to easily ascertain the melt state of an entire fabricated surface. Specifically provided is a three-dimensional additive manufacturing device that uses a manufacturing beam to perform additive manufacturing in a vacuum, said device comprising: a thermoelectron detection unit that detects the amount of thermoelectrons emitted from a fabricated surface irradiated with the manufacturing beam; a storage unit that stores the positions at which the fabricated surface is irradiated with the manufacturing beam in association with the amounts of thermoelectrons detected by the thermoelectron detection unit at the times of irradiation with the manufacturing beam, and a display control unit for displaying a thermoelectron distribution image obtained by superimposing an image expressing the amounts of thermoelectrons, said image being stored at the storage unit, on an image of the fabricated surface.

Description

Technical Field

[0001] The present invention relates to a three-dimensional laminating manufacturing apparatus, a manufacturing surface monitoring method, and an information processing program.

Background Art

[0002] In the above technical field, Patent Document 1 discloses an anti-deposition cover for preventing metal vapor generated during manufacturing or metal sputtering by fireworks from depositing on the inner wall of a vacuum chamber. The anti-deposition cover captures thermoelectrons emitted from the manufacturing surface, detects them as current by a voltage superimposed current amplifier, and calculates the manufacturing surface temperature.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, with the technology described in the above document, it was not possible to easily grasp the melting state of the entire manufacturing surface.

[0005] An object of the present invention is to provide a technology for solving the above problems.

Means for Solving the Problems

[0006] To achieve the above object, a three-dimensional laminating manufacturing apparatus according to the present invention is a three-dimensional laminating manufacturing apparatus that performs laminating manufacturing using a manufacturing beam in a vacuum, a thermoelectron detection unit that detects the amount of thermoelectrons emitted from a manufacturing surface irradiated with the manufacturing beam, A storage unit that stores in association the irradiation position of the molding surface irradiated with the molding beam and the amount of thermionic electrons detected by the thermionic electron detection unit at the timing of irradiation with the molding beam, A display control unit for displaying a thermionic electron distribution image obtained by superimposing an image representing the amount of thermionic electrons stored in the memory unit onto an image of the fabricated surface, It is equipped.

[0007] To achieve the above objective, the molding surface monitoring method according to the present invention is A method for monitoring the surface of a fabricated object in 3D additive manufacturing, A thermionic detection step for detecting the amount of thermionic electrons emitted from the fabrication surface irradiated by the fabrication beam used for additive manufacturing, A storage step involves storing in a storage unit the irradiation position of the molding surface irradiated with the molding beam and the amount of thermionic electrons detected at the timing of the molding beam irradiation, in association with each other. A display control step for displaying a thermionic electron distribution image obtained by superimposing an image representing the amount of thermionic electrons stored in the memory unit onto an image of the fabricated surface, including

[0008] To achieve the above objective, the information processing program according to the present invention is: A thermionic quantity acquisition step is to acquire the amount of thermionic electrons emitted from the fabrication surface irradiated by the fabrication beam used for additive manufacturing, A storage step involves storing in a storage unit the irradiation position of the molding surface irradiated with the molding beam and the amount of thermionic electrons acquired at the timing of the molding beam irradiation, in association with each other. A display control step for displaying a thermionic electron distribution image obtained by superimposing an image representing the amount of thermionic electrons stored in the memory unit onto an image of the fabricated surface, Have the computer execute it. [Effects of the Invention]

[0009] This invention makes it possible to easily grasp the melting state of the entire molded surface. [Brief explanation of the drawing]

[0010] [Figure 1] It is a block diagram showing the configuration of a three-dimensional layer manufacturing apparatus according to the first embodiment. [Figure 2] It is a block diagram showing the configuration of a three-dimensional layer manufacturing apparatus according to the second embodiment. [Figure 3] It is a graph showing the relationship between the melting temperature and the thermoelectron amount at the irradiation position according to the second embodiment. [Figure 4A] It is a diagram showing the configuration of a thermoelectron amount storage table according to the second embodiment. [Figure 4B] It is a diagram showing the configuration of a thermoelectron amount display image table according to the second embodiment. [Figure 5] It is a flowchart showing the processing procedure of a three-dimensional layer manufacturing apparatus according to the second embodiment. [Figure 6] It is a diagram showing a display screen displayed by a three-dimensional layer manufacturing apparatus according to the second embodiment. [Figure 7] It is a block diagram showing the configuration of a three-dimensional layer manufacturing apparatus according to the third embodiment. [Figure 8] It is a diagram showing the configuration of a conversion table according to the third embodiment. [Figure 9] It is a diagram showing the processing procedure and processing content of a three-dimensional layer manufacturing apparatus according to the fourth embodiment. [Figure 10] It is a block diagram showing the configuration of a three-dimensional layer manufacturing apparatus according to the fifth embodiment. [Figure 11] It is a block diagram showing the configuration of a three-dimensional layer manufacturing apparatus according to the sixth embodiment.

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be illustratively and specifically described with reference to the drawings. However, the components described in the following embodiments are merely examples, and are not intended to limit the technical scope of the present invention thereto.

[0012] [First Embodiment] A three-dimensional additive manufacturing apparatus 100 as a first embodiment of the present invention will be described with reference to Figure 1. The three-dimensional additive manufacturing apparatus 100 is an apparatus that performs additive manufacturing using a manufacturing beam in a vacuum.

[0013] As shown in Figure 1, the 3D additive manufacturing apparatus 100 includes a thermionic electron detection unit 101, a storage unit 102, and a display control unit 103. The thermionic electron detection unit 101 detects the amount of thermionic electrons 113 emitted from the manufacturing surface 112 irradiated by the manufacturing beam 111. The storage unit 102 stores the irradiation position 121 of the manufacturing surface 112 irradiated by the manufacturing beam 111 and the amount of thermionic electrons 122 detected by the thermionic electron detection unit 101 at the timing of the irradiation of the manufacturing beam 111, in association with each other. The display control unit 103 displays a thermionic electron distribution image 114, which is obtained by superimposing an image 131 representing the amount of thermionic electrons stored in the storage unit 102 onto an image 132 of the manufacturing surface.

[0014] According to this embodiment, the melting state of the entire fabricated surface can be easily grasped by a thermionic electron distribution image, which is obtained by superimposing an image representing the amount of thermionic electrons onto an image of the fabricated surface. In Figure 1, the amount of thermionic electrons is represented by the size of the display dots, but this is not the only option; a heat map image using display brightness, density, or color differences may also be used.

[0015] [Second Embodiment] Next, a three-dimensional additive manufacturing apparatus 200 according to a second embodiment of the present invention will be described. The three-dimensional additive manufacturing apparatus 200 according to this embodiment detects the amount of thermionic electrons emitted from the manufacturing surface irradiated with a manufacturing beam, stores the irradiation position of the manufacturing surface irradiated with the manufacturing beam and the amount of thermionic electrons detected at the timing of the manufacturing beam irradiation in association, and displays a thermionic electron distribution image by superimposing an image representing the amount of thermionic electrons onto an image of the manufacturing surface. Here, the image representing the amount of thermionic electrons may be a heat map image. Thermionic electrons are detected by detecting the current output from a positively charged metal plate. In this embodiment, the metal plate is supported by an insulator on the build plate and positioned close to the manufacturing surface, and the connection between the metal plate and the current detection unit is positioned away from the manufacturing surface.

[0016] <Configuration and operation of a 3D additive manufacturing system> Figure 2 is a block diagram showing the configuration of the 3D additive manufacturing apparatus 200 according to this embodiment. The 3D additive manufacturing apparatus 200 comprises an additive manufacturing unit 290 and an information processing unit 240.

[0017] (Configuration of the additive manufacturing section) In the additive manufacturing unit 290 shown in Figure 2, an electron gun 202 is mounted on a vacuum chamber 201, and a build frame (build box) 203 with a circular or rectangular cross-section is provided inside the vacuum chamber 201. A Z-drive mechanism (a mechanism that changes the direction of rotation vertically) 204 is located on the lower inside of the build frame 203, and the powder tray 205 can be driven in the Z direction by a rack and pinion or a ball screw. A heat-resistant flexible seal 206 is provided in the gap between the build frame 203 and the powder tray 205, and sliding surfaces on the inner surface of the build frame 203 provide sliding and sealing properties. The vacuum chamber 201 is evacuated by a vacuum pump (not shown), and the inside of the vacuum chamber 201 is maintained under vacuum.

[0018] A build plate 209 is positioned on the powder tray 205, with the build plate 209 being constructed on a raised surface of unsintered powder 213. The build plate 209 is grounded to the powder tray 205, which is at ground potential, by a GND line 210 to prevent it from floating electrically. The build plate 208 is formed on the build plate 209, and during the construction of each layer, metal powder 211 is spread using a linear funnel 212 filled with metal powder up to approximately the same height as the top surface of the build frame base 203. The linear funnel 212 is replenished with powder as needed from a powder hopper (not shown). An electron beam from an electron gun 202 melts the area of ​​the build plate 208 on the spread layer of unsintered powder 213 in two dimensions, and the build plate 208 is constructed by overlapping these melted layers. The areas of the powder (unsintered) 213 spread on the build plate 209 other than the built object 208 are partially sintered powder (spread powder (partially sintered) 214) by the electron beam from the electron gun 202, and are electrically conductive.

[0019] A protective cover 215, grounded to GND, is installed between the build surface and the electron gun 202 to prevent the deposition of metal vapor and metal sputter from the fireworks onto the inner wall of the chamber during build. This cover also serves as a radiation shield from the high-temperature build surface.

[0020] In this embodiment, a dedicated thermionic detection electrode 220 is used to detect thermionic electrons. The metal used for the thermionic detection electrode 220 is a metal electrode such as Ti, which has a low secondary electron emission rate during electron excitation. The insulator used to electrically isolate the electrode from ground potential is kept away from the fabrication surface to suppress the decrease in insulation resistance due to temperature rise.

[0021] A thermionic electrode guide 221, with thermionic electron detection electrodes 220 attached via an insulator 217, is mounted on both ends of the build frame 203, which has a small temperature rise during the build process. A voltage-superimposed current amplifier 219 is connected to the thermionic electrode guide 221 via a current introduction terminal 218 attached to the vacuum vessel 201. The voltage-superimposed current amplifier 219 has almost no effect on the primary electron beam relative to GND. Furthermore, a low voltage of +several volts or less is applied so that only thermionic electrons with lower energy than secondary electrons are attracted, drawing thermionic electrons emitted from the melting point of the build object 208 during the melting process into the thermionic electron detection electrode 220 by a positive potential gradient, and detecting the amount of electrons as a current. Applying a positive voltage can also improve the detection efficiency of thermionic electrons when the electron beam is OFF or during laser beam melting. The amount of drawn-in thermionic electrons can be controlled by changing the positive applied voltage, and the applied voltage is changed depending on whether the temperature is relatively low or high. For example, by increasing the positive applied voltage at relatively low temperatures and decreasing it at higher temperatures, the current amplifier can be used across the entire temperature range without changing its gain.

[0022] In the configuration shown in Figure 2, the anti-adhesion cover 215 hangs below the electron gun 202. However, a guide for the GND potential can be placed on top of the thermionic electron detection electrode guide 221 via an insulator, and the anti-adhesion cover 215 can be mounted on top of that. This is convenient because it allows the thermionic electron detection electrode 220 and the anti-adhesion cover 215 to be mounted together on the build surface.

[0023] (Configuration of the information processing unit) The information processing unit 240 in Figure 2 comprises a thermionic detection unit 250, a storage unit 260, and a display control unit 270. Here, thermionic detection unit 250, storage unit 260, and display control unit 270 correspond to the thermionic detection unit 101, storage unit 102, and display control unit 103 in Figure 1.

[0024] The thermionic electron detection unit 250 includes a voltage superimposed current amplifier 219, an A / D conversion unit 251, and a thermionic electron quantity acquisition unit 252. The voltage superimposed current amplifier 219 is a circuit that converts the amount of thermionic electrons drawn in by the thermionic electron detection electrode 220 into an electric current, as explained in the additive manufacturing unit 290. The A / D conversion unit 251 converts the analog current value, which is the output of the voltage superimposed current amplifier 219, into a digital current value. The thermionic electron quantity acquisition unit 252 then acquires the digital current value corresponding to the amount of thermionic electrons and stores it in the storage unit 260 in association with the irradiation position.

[0025] The memory unit 260 has a thermionic quantity memory table 261, in which the amount of thermionic electrons is stored in association with the irradiation position. The display control unit 270 has a thermionic quantity display image table 271, and generates a display screen by superimposing an image representing the amount of thermionic electrons that can be identified in association with the irradiation position, based on the amount of thermionic electrons stored in the thermionic quantity memory table 261 of the memory unit 260, with an image of the fabricated surface, so that the irradiation positions overlap. The generated thermionic quantity display screen is then transmitted to the display unit 280 for display.

[0026] (operation) The upper surface of the build plate 209, covered with the spread-out powder, is positioned at approximately the same height as the upper surface of the build frame base 203. An electron beam from the electron gun 202 is irradiated onto a slightly narrower area than the entire upper surface of the build plate 209 to preheat it to a temperature sufficient for the metal powder 211 to partially sinter. At the start of the build process, the powder tray 205 is lowered by the Z-drive mechanism 204 so that the upper surface of the build plate 209 is positioned slightly lower than the upper surface of the build frame base 203. This slight lowering of ΔZ corresponds to the subsequent layer thickness in the Z direction. The linear funnel 212 filled with metal powder 211 is moved along the upper surface of the build plate 209 to the opposite side, spreading ΔZ worth of metal powder 211 on and around the build plate 209. The electron beam from the electron gun 202 is irradiated onto the powder spread on the build plate 209 in an area slightly smaller than the build plate 209, heating the metal powder 211 spread on the build plate 209 and ensuring that the metal powder in the irradiated area is pre-sintered.

[0027] The fabrication sequence involves "squeegeeing" to spread the powder, "powder heating (PH)" to heat the spread powder, then "melting" the fabrication area, and finally "preheating (AH)" to prepare the next squeegee. This process is repeated for each layer to create the fabrication object. In the melting process, the electron beam from the electron gun 202 melts the 2D shape region according to the 2D shape obtained by slicing the pre-prepared design object at ΔZ intervals. The melting process involves scanning the electron beam according to a pre-set campus, melting each point one by one with a pre-set beam current, beam diameter, and scanning speed (determined by the dwell time at one point and the distance to the next point). As each point melts, thermionic signals from the voltage-superimposed current amplifier 219 are detected, and the intensity distribution of thermionic electrons is imaged as the brightness signal of the corresponding point in the 2D shape of the fabricated object.

[0028] In the 3D additive manufacturing apparatus 200 shown in Figure 2, the additive manufacturing unit 290 and the information processing unit 240 are shown as an example where they are located close together. However, the additive manufacturing unit 290 and the information processing unit 240, or a part of the information processing unit 240, may be located remotely and communicate with each other via wired or wireless communication.

[0029] <Reasons why thermionic electrons are detected at the melting point> Figure 3 is a graph showing the relationship between the melting temperature and thermionic electron quantity at the irradiation position according to this embodiment. Figure 3 shows the results of calculating thermionic electrons generated from a φ0.5 mm region in a Ti64 alloy as a function of temperature.

[0030] As can be seen from Figure 3, the amount of thermionic electrons increases exponentially with increasing temperature. For example, in the case of Ti64, the fabrication surface is heated to about 750°C during the powder heating (PH) process before melting, and the amount of thermionic electrons emitted from the entire area is about 0.5 pA (picoamperes). In contrast, thermionic electron emission from a φ0.5 mm region at the melting point (about 1650°C) is about 1 μA (microamperes), it becomes about 100 μA (microamperes) when the melting temperature reaches about 2000°C, and furthermore, at about 2400°C, thermionic electrons of 4 mA (milliamperes) or more are generated.

[0031] On the other hand, thermionic electrons emitted when heating the build surface during powder heating (PH) or preheating (AH) are present when the build surface is 110 x 110 mm. 2 In that case, even if the temperature is 1000°C, the current is small, only about 20 nA (nanoamperes). When melting, the temperature outside the melting point is lower, so the thermionic electrons detected during melting reflect the temperature of the melting point (melt pool), which is high. Because thermionic electrons in the molten state are orders of magnitude larger, the thermionic electron image, assuming that the melting area is approximately the same, will reflect the melting temperature distribution.

[0032] For example, the memory unit 260 stores the irradiation position where the molding beam was irradiated and the integrated value of thermionic electrons detected by the thermionic electron detection unit 250 at a predetermined time related to the irradiation timing of the molding beam, associating them with each other. For example, the residence time is a current amount of several tens of microseconds (25 microseconds), and is a current value that can be read at around 100 kHz, depending on the amplifier bandwidth. For more accurate thermionic measurement, it is desirable to turn off the electron beam from the electron gun 202 to avoid the influence of electrons from the electron gun 202 (primary electrons) and secondary electrons generated from the powder by the electron beam. Alternatively, the electron beam from the electron gun 202 may be pulsed, and lock-in detection may be performed at that frequency. Furthermore, if the electron beam is pulsed and lock-in detection is performed, it is not necessary to turn off the electron beam at predetermined time intervals. Also, if the irradiation current from the electron gun 202 is constant, its effect can be processed as an offset in the thermionic current, allowing the amount of thermionic electrons to be converted even while the beam is irradiated.

[0033] (Thermionic electron storage table) Figure 4A shows the configuration of the thermionic quantity storage table 261 according to this embodiment. The thermionic quantity storage table 261 is used in the storage unit 260 to store the thermionic quantity in association with the irradiation position.

[0034] The thermionic quantity storage table 261 stores the thermionic quantity in association with the X-coordinate in the X direction and the Y-coordinate in the Y direction, which indicate the irradiation position on the fabricated surface. Coordinates that are not part of the fabricated object (not irradiated) are stored with a value of zero or not a thermionic quantity. In Figure 4A, the coordinates are set to "0001" to "0FFF", but are not limited to this.

[0035] (Thermionic electron quantity display image table) Figure 4B shows the configuration of the thermionic quantity display image table 271 according to this embodiment. The thermionic quantity display image table 271 is used by the display control unit 270 to generate a display screen in which the thermionic quantity image and the fabricated surface image are superimposed.

[0036] The thermionic quantity display image table 271 includes image data representing the amount of thermionic electrons (thermionic quantity distribution image data) 471 and image data of the fabricated surface (fabricated surface image data) 472. The thermionic quantity distribution image data 471 stores image data converted from the amount of thermionic electrons stored in Figure 4A into an identifiable display. The fabricated surface image data 472 stores image data that allows identification of parts of the fabricated object and parts that are not fabricated. Image data of the fabricated surface may also be used as the fabricated surface image data 472.

[0037] <Processing procedure for 3D additive manufacturing equipment> Figure 5 is a flowchart showing the processing procedure of the 3D additive manufacturing apparatus according to this embodiment. This flowchart realizes the components shown in Figure 2 so that the CPU (Central Processing Unit) of the information processing unit 240 executes the process using RAM (Random Access Memory) to operate the 3D additive manufacturing apparatus.

[0038] In step S501, the information processing unit 240 waits for the acquisition of additive manufacturing data. Once the additive manufacturing data is acquired, in step S503, the information processing unit 240 instructs the additive manufacturing unit 290 to squeegee the additive manufacturing powder. In step S505, the information processing unit 240 instructs the additive manufacturing unit 290 to perform "powder heating (PH)" to heat the laid powder. In step S507, the information processing unit 240 instructs the additive manufacturing unit 290 to "melt" the manufacturing area. In step S509, the information processing unit 240 instructs the additive manufacturing unit 290 to perform "preheating (AH)" to prepare the next squeegee. In step S511, the information processing unit 240 instructs the additive manufacturing unit 290 to lower the build plate by one layer. In step S513, the information processing unit 240 determines whether or not the additive manufacturing is complete. If it is not complete, it returns to step S503 and repeats the manufacturing of the next layer.

[0039] In step S507, during the "melting" of the fabricated area, the fabrication surface monitoring method of this embodiment is performed by carrying out the processes in steps S571 to S581. In step S571, the information processing unit 240 acquires the amount of thermionic electrons. In step S573, the information processing unit 240 stores the acquired amount of thermionic electrons in the storage unit 260, corresponding to the irradiation position. In step S575, the information processing unit 240 determines whether or not the melting process in the current fabrication layer is complete. If the melting process in the current fabrication layer is not complete, the information processing unit 240 returns to step S571 and acquires the amount of thermionic electrons corresponding to the next irradiation position.

[0040] If the amount of thermionic electrons is to be converted to the melting temperature once the melting process in the current build layer is complete, the information processing unit 240 converts the amount of thermionic electrons to the melting temperature in step S577. On the other hand, if the amount of thermionic electrons is not to be converted to the melting temperature once the melting process in the current build layer is complete, the information processing unit 240 proceeds to step S579. In step S579, the information processing unit 240 superimposes a thermionic electron distribution image (melting temperature distribution image) onto the image of the build surface. Then, in step S581, the information processing unit 240 controls the display of the superimposed thermionic electron distribution image (melting temperature distribution image).

[0041] (display screen) Figure 6 shows the display screen shown by the 3D additive manufacturing apparatus 200 according to this embodiment. Figure 6 shows the fabricated surface and the thermionic image when that surface is melted.

[0042] The arrow 611 shown on the fabrication surface 610 indicates the scanning direction of the molten beam. Since the scanning motion is a back-and-forth motion across the molten region, the return portion is affected by the energy input during the forward (forward) path, resulting in a higher melting temperature and a slight bulge on the fabrication surface.

[0043] The thermionic image 620 shows an image that includes a region 621 with a high amount of thermionic electrons, reflecting this. This is because the fabrication is performed with a constant input energy. By controlling the input energy so that the signal intensity in the thermionic image 620 remains constant, this bulging can be avoided, and fabrication with consistently stable quality can be achieved. The signal intensity of this thermionic image is also sufficient as an indicator of the melting temperature distribution.

[0044] Note that while Figure 6 shows the amount of thermionic electrons based on differences in display brightness, it is not limited to this; heatmap images based on differences in dot size, display density, or color may also be used.

[0045] According to this embodiment, the melting state of the entire fabricated surface can be easily grasped by a thermionic electron distribution image, which is obtained by superimposing an image representing the amount of thermionic electrons onto an image of the fabricated surface.

[0046] In other words, by detecting thermionic electrons during molten material, it is now possible to measure the melting temperature and its index at each melting point in the molten region. Furthermore, it is no longer necessary to change parameters such as melting energy and observe the molten surface shape during fabrication or internal defects and the fabricated surface shape after fabrication to determine the optimal melting conditions; the amount of thermionic electrons corresponding to the melting temperature can be measured. This allows for control to maintain a constant melting temperature throughout the melting process, regardless of the size or location of the molten region. Moreover, optimizing the melting temperature enables the fabrication of consistently high-quality objects.

[0047] [Third Embodiment] Next, a three-dimensional additive manufacturing apparatus according to the third embodiment of the present invention will be described. The three-dimensional additive manufacturing apparatus according to this embodiment differs from the second embodiment in that it displays a melting temperature distribution image, which is an image representing the melting temperature calculated based on the amount of thermionic electrons rather than thermionic electrons themselves, superimposed on an image of the fabricated surface. The image representing the melting temperature may be a heat map image. The other configurations and operations are the same as in the second embodiment, so the same reference numerals are used for the same configurations and operations and their detailed descriptions are omitted.

[0048] <Configuration and operation of a 3D additive manufacturing system> Figure 7 is a block diagram showing the configuration of the 3D additive manufacturing apparatus 700 according to this embodiment. In Figure 7, the same reference numerals are used for components that are the same as those in Figure 2, and redundant explanations are omitted.

[0049] Figure 7 shows a thermionic quantity-temperature conversion unit 780 and a display control unit 770. Thermionic quantity-temperature conversion unit 780 has a conversion table 781 and converts the thermionic values ​​in the storage unit 260 into melting temperatures. The display control unit 770 has a melting temperature display image table 771 and generates an image representing the melting temperature that can be identified in association with the irradiation position, based on the melting temperature converted by the conversion table 781 of the thermionic quantity-temperature conversion unit 780. It then generates a melting temperature distribution display screen by superimposing the image representing the melting temperature and an image of the fabricated surface so that the irradiation positions overlap. The generated display screen is then transmitted to the display unit 280 for display.

[0050] (Conversion Table) Figure 8 shows the configuration of the conversion table 781 according to this embodiment. The conversion table 781 is used by the thermionic-temperature conversion unit 780 to convert thermionic quantity to the melting temperature.

[0051] The conversion table 781 is generated as follows. The relationship between the temperature T of a radiation thermometer or the like and the thermionic current I detected by the voltage superimposed current amplifier 219 is measured in advance, and a and b are determined as constants by fitting them with the following equation (1). [Mathematics 1] I = a·T 2 ·e b / T (1) Alternatively, in the expanded equation as shown in equation (2), the relationship between ln(I / T²) and 1 / T can be plotted, and a and b can be determined from the slope b and intercept ln a of the resulting linear equation. The linear equation in this case can be found relatively easily using the least squares method, etc. (see Figure 8). [Math 2] ln (I / T 2 ) = b·1 / T + ln a (2) Using equation (1) from which a and b were obtained, the relationship between thermionic current and temperature is determined and converted to temperature.

[0052] Furthermore, since the above measurements are difficult to perform at the molten state, a sufficiently large area is scanned, and the temperature and thermionic electrons from that area are measured. The area is then expanded to a melt size such as the beam size, and the relationship between temperature and thermionic electrons in the required spot area is determined. In addition, once the relationship between temperature and thermionic electrons is determined, the thermionic electron signal for the required temperature is calculated in advance as a threshold value, and by using this value as a parameter, a melting process at the required melting temperature can be achieved.

[0053] According to this embodiment, the melting state of the entire fabricated surface can be more easily understood by superimposing an image representing the melting temperature onto an image of the fabricated surface to create a thermionic electron distribution image.

[0054] In other words, by detecting the temperature during melting, it became possible to measure the melting temperature and its index at each melting point in the melting region. Furthermore, it became unnecessary to change parameters such as melting energy and determine the optimal melting conditions by observing the molten surface shape during molding and the internal defects and surface shape after molding; the melting temperature could be measured directly. This allows for control to maintain a constant melting temperature throughout the melting process, regardless of the size or location of the melting region. Moreover, optimizing the melting temperature enables the creation of consistently high-quality molded objects.

[0055] [Fourth Embodiment] Next, a three-dimensional additive manufacturing apparatus according to the fourth embodiment of the present invention will be described. The three-dimensional additive manufacturing apparatus according to this embodiment differs from the second and third embodiments in that it corrects the amount of thermionic electrons (melting temperature) according to the surrounding conditions of the irradiation position to obtain a more accurate amount of thermionic electrons (melting temperature). That is, the amount of thermionic electrons (melting temperature) is divided by the area of ​​the region between the irradiation position to which the molding beam was irradiated and the adjacent irradiation position to obtain the amount of thermionic electrons (melting temperature) at the irradiation position to which the molding beam was irradiated. The other configurations and operations are the same as those of the second and third embodiments, so the same reference numerals are used for the same configurations and operations and their detailed descriptions are omitted.

[0056] <Processing Procedures and Contents of 3D Additive Manufacturing Equipment> Figure 9 shows the processing procedure and processing details of the 3D additive manufacturing apparatus according to this embodiment.

[0057] (Processing procedure) The left diagram (flowchart) in Figure 9 illustrates the processing procedure of the 3D additive manufacturing apparatus. In the flowchart of Figure 9, steps identical to those in Figure 5 are given the same step numbers, and redundant explanations are omitted.

[0058] In step S978, the information processing unit 240 corrects the amount of thermionic electrons (melting temperature) taking into account the surrounding area of ​​the irradiation position.

[0059] (Processing details) The corrections of this embodiment will be explained with reference to the right-hand figure in Figure 9.

[0060] When the melting temperature is estimated by detecting thermionic electrons at each melting point, as in the embodiment described above, the fact that heat diffusion around the melting point differs depending on the shape of the molded object and the location of the melting within that shape is not taken into account. Generally, the bulk part of the molded object has a higher thermal conductivity than the surrounding pre-sintered part. Therefore, when melting the inside of the molded surface, the energy input required to reach the same temperature is greater due to the greater heat diffusion, and the melt pool becomes relatively large. On the other hand, at the vertices of a triangular molded surface as shown in Figure 9, heat diffusion is small, so the temperature rises more locally, and the melt pool becomes relatively small.

[0061] Therefore, in this embodiment, in order to estimate a more appropriate input energy, the assumption that the melt pool size is the same at each melting point, as in the above embodiment, is abandoned. Then, the thermionic image is displayed as the amount of thermionic signal per unit area that takes into account the arrangement of melting points determined according to the fabricated shape, thereby reflecting the temperature distribution that is in line with the fabricated shape. By controlling the input energy at each melting point so that the temperature distribution is constant, melting unevenness can be reduced, leading to defect suppression.

[0062] For example, in the case of a triangular build surface as shown in Figure 9, a scanspace is pre-set as indicated by the arrows during melting, and the position of the melting points is determined by the scan pitch (the interval between melting points in the scanning direction) and the line pitch (the interval to the next scan line). At each melting point, the intensity of the thermionic signal during melting is divided by the area enclosed by the surrounding melting points, and this value is imaged as the intensity at that melting point.

[0063] At vertex 901 of the triangular build surface in Figure 9, there is one melting point at the vertex, and the next scan line is spaced by the line pitch, with the spacing of the melting points on that line determined by the scan pitch. If the scan line length is not a multiple of the scan pitch, a fractional value will be left over, and the handling of this varies depending on the device. Here, it depends on whether it is greater than or less than half of the scan pitch. If it is greater than or equal to half, the line pitch becomes shorter and one point is placed at the end of that line. On the other hand, if it is less than half, the line pitch becomes longer when combined with the previous scan pitch, and one point is placed at the end of the line. In the triangular build surface in Figure 9, the second line end from the top (rightmost end) corresponds to the former, and the sixth corresponds to the latter.

[0064] When melting vertex 901 of the triangular build surface, the area enclosed by the vertex and the three points of the second line, as indicated by the grid, is the area of ​​the triangle enclosed by the melting points. When melting internal point 902 of the triangular build surface, the area enclosed by the six surrounding points, as indicated by the grid, is the area of ​​the melting points. When melting the final scanning point 903 of one line of the triangular build surface, the area enclosed by the four surrounding points, as indicated by the grid, is the area of ​​the melting points. When melting the final scanning line point 904 of the triangular build surface, the area enclosed by the four surrounding points, as indicated by the grid, is the area of ​​the melting points. Similarly, the areas enclosed by the melting points for other melting points are shown by filling in the grid. These areas can be easily calculated by determining the melting points with a pre-set scan pitch and line pitch.

[0065] The amount of thermionic electrons (melting temperature) is divided by the area of ​​the region between the irradiation position where the build beam was applied and adjacent irradiation positions to obtain the amount of thermionic electrons (melting temperature) at the irradiation position where the build beam was applied. In this way, if the melting point is far from the surrounding area (region with low melting point density), the insufficient melting due to the decrease in density can be compensated for by raising the temperature of that one point, resulting in a build with fewer defects. Conversely, if the melting points are densely packed (region with high melting point density), the excessive melting due to the increase in density can be compensated for by raising the temperature of that one point, resulting in a build with fewer defects and faster construction.

[0066] According to this embodiment, a more accurate amount of thermionic electrons (melting temperature) can be obtained, allowing for precise adjustment of melting parameters (irradiation intensity, scanning speed, beam diameter, film thickness, etc.).

[0067] [Fifth Embodiment] Next, a three-dimensional additive manufacturing apparatus according to the fifth embodiment of the present invention will be described. The three-dimensional additive manufacturing apparatus according to this embodiment differs from the second to fourth embodiments in that it detects thermionic electrons using a conductor in the existing anti-adhesion cover. In this embodiment, the positively charged metal plate for detecting thermionic electrons is provided inside the anti-adhesion cover that prevents the emission of vapors radiated from the manufacturing surface. The other configurations and operations are the same as in the second to fourth embodiments, so the same reference numerals are used for the same configurations and operations and their detailed descriptions are omitted.

[0068] <Configuration and operation of a 3D additive manufacturing system> Figure 10 is a block diagram showing the configuration of the 3D additive manufacturing apparatus 1000 according to this embodiment. In Figure 10, components similar to those in Figure 2 are given the same reference numerals, and redundant explanations are omitted.

[0069] (Configuration of the additive manufacturing section) The apparatus configuration when using the anti-adhesion cover 1015 for thermionic electron detection is as shown in the additive manufacturing section 1090 of Figure 10, with the anti-adhesion cover 1015 attached to the bottom of the electron gun 202 via an insulator 1017. In Figure 10, it is attached to the electron gun 202, but it may also be attached to the top surface of the vacuum vessel 201, or electrodes for thermionic electron detection may be provided inside the grounded anti-adhesion cover 1015. A voltage-superimposed current amplifier 219 is connected to the anti-adhesion cover 1015 via a current introduction terminal 218 attached to the vacuum vessel 201. The voltage-superimposed current amplifier 219 applies a voltage of +several volts or less relative to GND, which has almost no effect on the primary electron beam, and thermionic electrons emitted from the melting point of the fabricated object 208 during the melting process are drawn into the anti-adhesion cover 1015 by a positive potential gradient, and the amount of electrons is detected as a current.

[0070] (Configuration of the information processing unit) The information processing unit 240 in this embodiment is the same as in Figure 2, except that the conductive material for thermionic detection is the protective cover 1015. It may also be the same as the information processing unit 740 in Figure 7.

[0071] (operation) The operation of the 3D additive manufacturing apparatus in this embodiment is the same as in the above embodiment, so redundant explanations will be omitted.

[0072] According to this embodiment, without providing a new conductor to attract thermionic electrons as in the second embodiment, the melting state of the entire fabricated surface can be easily grasped by a thermionic electron distribution image obtained by superimposing an image representing the amount of thermionic electrons onto an image of the fabricated surface.

[0073] [Sixth Embodiment] Next, a three-dimensional additive manufacturing apparatus according to the sixth embodiment of the present invention will be described. The three-dimensional additive manufacturing apparatus according to this embodiment differs from the second to fifth embodiments in that the additive manufacturing parameters can be automatically adjusted by the information processing unit. The other configurations and operations are the same as those of the second to fifth embodiments, so the same reference numerals are used for the same configurations and operations and their detailed descriptions are omitted.

[0074] <3D additive manufacturing equipment> Figure 11 is a block diagram of the 3D additive manufacturing apparatus 1100 according to this embodiment. In Figure 11, the same reference numerals are used for components that are the same as those in Figures 2, 7, and 10, and redundant explanations are omitted.

[0075] The information processing unit 1140 in Figure 11 includes an additive manufacturing adjustment unit 1190. The additive manufacturing adjustment unit 1190 adjusts the irradiation intensity, scanning speed, layer thickness, beam diameter, etc., so that the melting temperature shown in the melting temperature distribution image from the display control unit 770 becomes the target melting temperature. Note that the additive manufacturing parameters to be adjusted are not limited to these.

[0076] According to this embodiment, remelting due to insufficient melting for each layer, or adjusting the melting state for the next layer, can be performed in real time. For example, variations in the melting state can be predicted from the constructed thermionic electron distribution image, and the remelting energy distribution at each point in the melted region can be calculated accordingly to remelt the region so that it has a uniform thermionic electron distribution. Such remelting can also be limited to only localized areas of insufficient melting.

[0077] [Other embodiments] The above embodiment shows the case of an electron beam type PBF, but similarly, the melting temperature can be measured by thermionic electrons during melting with wire or powder type DEDs. Similarly, with laser types, thermionic electron measurement can be performed in a vacuum, allowing for the measurement of the melting temperature during melting. In the case of laser beam melting, thermionic electrons are also detected during beam irradiation.

[0078] Although the present invention has been described above with reference to embodiments, the present invention is not limited to the above embodiments. Various modifications to the structure and details of the present invention can be made, as can be understood by those skilled in the art within the technical scope of the present invention. Furthermore, any system or apparatus that combines the separate features included in each embodiment is also within the technical scope of the present invention.

[0079] Furthermore, the present invention may be applied to a system composed of multiple devices or to a single device. Moreover, the present invention is also applicable when an information processing program that realizes the functions of the embodiment is supplied to a system or device and executed by a built-in processor. The technical scope of the present invention includes programs installed on a computer to realize the functions of the present invention on a computer, or a medium storing such a program, a server that downloads such a program, and a processor that executes such a program. In particular, at least a non-transitory computer-readable medium storing a program that causes a computer to execute the processing steps included in the embodiments described above is included in the technical scope of the present invention.

Claims

1. A three-dimensional additive manufacturing apparatus that performs additive manufacturing using a shaping beam in a vacuum, An irradiation unit that scans the aforementioned molding beam and irradiates it onto each position on the molding surface, An acquisition unit that acquires the irradiation position on the molding surface from the scanning data of the molding beam, A thermionic electron detection unit detects the amount of thermionic electrons emitted from the surface of the fabrication that has been irradiated with the fabrication beam, A storage unit that stores in association the irradiation position of the molding surface irradiated with the molding beam and the amount of thermionic electrons detected by the thermionic electron detection unit at the timing of irradiation with the molding beam, A display control unit for displaying an image representing the amount of thermionic electrons stored in the memory unit, A 3D additive manufacturing device equipped with [specific features / features].

2. The three-dimensional additive manufacturing apparatus according to claim 1, wherein the display control unit displays a thermionic electron distribution image obtained by superimposing an image representing the amount of thermionic electrons stored in the storage unit onto an image of the fabricated surface.

3. The three-dimensional additive manufacturing apparatus according to claim 1, wherein the display control unit displays a temperature distribution image obtained by superimposing an image representing the melting temperature calculated based on the amount of thermionic electrons onto an image of the fabricated surface.

4. The three-dimensional additive manufacturing apparatus according to claim 3, wherein the image representing the melting temperature is a heat map image.

5. The thermionic electron detection unit is A positively charged metal plate, A current detection unit that detects the current output from the metal plate, A three-dimensional additive manufacturing apparatus according to claim 1, comprising:

6. The three-dimensional additive manufacturing apparatus according to claim 5, wherein the metal plate is supported by an insulator on the build plate and positioned close to the build surface, and the connection between the metal plate and the current sensing unit is positioned away from the build surface.

7. The three-dimensional additive manufacturing apparatus according to claim 5, wherein the metal plate is provided inside an anti-adhesion cover that prevents the emission of vapors radiated from the molded surface.

8. The three-dimensional additive manufacturing apparatus according to claim 1, wherein the display control unit divides the amount of thermionic electrons stored in the storage unit by the area of ​​the region between the irradiation position irradiated by the molding beam and the adjacent irradiation position to obtain the amount of thermionic electrons at the irradiation position irradiated by the molding beam.

9. The three-dimensional additive manufacturing apparatus according to claim 1, wherein the storage unit stores in association the irradiation position to which the molding beam was irradiated and the integrated value of thermionic electrons detected by the thermionic electron detection unit at a predetermined time related to the irradiation timing of the molding beam.

10. A method for monitoring the surface of a fabricated object in 3D additive manufacturing, A thermionic detection step for detecting the amount of thermionic electrons emitted from the fabrication surface irradiated by the fabrication beam used for additive manufacturing, A storage step involves storing in a storage unit the irradiation position of the molding surface irradiated with the molding beam and the amount of thermionic electrons detected at the timing of the molding beam irradiation, in association with each other. A display control step for displaying an image representing the amount of thermionic electrons stored in the memory unit, A method for monitoring the fabricated surface in three-dimensional additive manufacturing, including the method described above.

11. A thermionic quantity acquisition step is to acquire the amount of thermionic electrons emitted from the fabrication surface irradiated by the fabrication beam used for additive manufacturing, A storage step involves storing in a storage unit the irradiation position of the molding surface irradiated with the molding beam and the amount of thermionic electrons acquired at the timing of the molding beam irradiation, in association with each other. A display control step for displaying an image representing the amount of thermionic electrons stored in the memory unit, An information processing program that causes a computer to execute something.

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