Three-dimensional additive manufacturing system, control method therefor, and control program therefor

Abstract

In order to perform shaping control in accordance with a molten state of a shaping surface in three-dimensional additive manufacturing, provided is a three-dimensional additive manufacturing system that performs additive manufacturing by using a shaping beam in a vacuum. The three-dimensional additive manufacturing system is characterized by comprising: a thermal electron detection unit that detects an amount of thermal electrons emitted from the shaping surface by irradiating the shaping surface with the shaping beam; and a control unit that controls the operation of the shaping beam in accordance with the amount of thermal electrons. Also provided are a control method therefor and a control program therefor.

Description

Three-dimensional additive manufacturing system, its control method, and control program

[0001] The present invention relates to a three-dimensional additive manufacturing system, a control method thereof, and a control program.

[0002] In the above technical field, Patent Document 1 discloses a technology in which thermoelectrons emitted from the molding surface are captured by a protective cover to prevent metal vapor generated from the molten part during molding, or metal spatter from fireworks, from being deposited on the inner wall of the vacuum container, and the captured thermoelectrons are detected as a current by a voltage superimposed current amplifier to calculate the temperature of the molding surface.

[0003] Japanese Patent Publication No. 2022-050034

[0004] However, the technology described in the above document does not allow for molding control according to the melting state of the entire molding surface.

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

[0006] In order to achieve the above-mentioned object, the system of the present invention is a three-dimensional additive manufacturing system that performs additive manufacturing in a vacuum using an electron beam or laser for manufacturing, and is equipped with: a thermoelectron detection unit that detects the amount of thermoelectrons emitted from the manufacturing surface when the electron beam or laser is irradiated onto the manufacturing surface; and a control unit that controls the operation of the electron beam or laser according to the amount of thermoelectrons.

[0007] In order to achieve the above-mentioned object, the method of the present invention is a control method for a three-dimensional additive manufacturing system that performs additive manufacturing in a vacuum using a manufacturing beam, and includes: a thermoelectron detection step of detecting the amount of thermoelectrons emitted from the manufacturing surface when the manufacturing beam is irradiated onto the manufacturing surface; and a control step of controlling the operation of the manufacturing beam in accordance with the amount of thermoelectrons.

[0008] In order to achieve the above-mentioned object, the program of the present invention is a control program for a three-dimensional additive manufacturing system that performs additive manufacturing using a manufacturing beam in a vacuum, and causes a computer to execute the following steps: a thermoelectron detection step that detects the amount of thermoelectrons emitted from the manufacturing surface when the manufacturing beam is irradiated onto the manufacturing surface; and a control step that controls the operation of the manufacturing beam in accordance with the amount of thermoelectrons.

[0009] According to the present invention, it is possible to control molding in accordance with the melting state of the molding surface.

[0010] FIG. 1 is a block diagram showing the configuration of a three-dimensional additive manufacturing system according to a first embodiment. FIG. 2 is a block diagram showing the configuration of a three-dimensional additive manufacturing system according to a second embodiment. FIG. 3 is a graph showing the relationship between the melting temperature at the irradiation position and the amount of thermoelectrons according to the second embodiment. FIG. 4 is a flowchart showing the processing procedure of the three-dimensional additive manufacturing system according to the second embodiment. FIG. 5 is a diagram showing the configuration of a conversion table according to the second embodiment. FIG. 6 is a diagram explaining an overview of a three-dimensional additive manufacturing system according to a third embodiment. FIG. 7 is a block diagram showing the configuration of a three-dimensional additive manufacturing device according to the third embodiment. FIG. 8 is a block diagram showing the configuration of a three-dimensional additive manufacturing device according to a fourth embodiment. FIG. 9 is a block diagram showing the configuration of a three-dimensional additive manufacturing device according to a fifth embodiment.

[0011] Hereinafter, embodiments of the present invention will be described in detail by way of example 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.

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

[0013] 1, the three-dimensional additive manufacturing system 100 includes a thermoelectron detection unit 101 and a control unit 102. The thermoelectron detection unit 101 detects the amount of thermoelectrons 113 emitted from a manufacturing surface 112 when the manufacturing surface 112 is irradiated with a manufacturing beam 111 (electron beam or laser).

[0014] The control unit 102 controls the operation of the manufacturing beam 111 in accordance with the amount of the thermoelectrons 113 .

[0015] According to this embodiment, it is possible to perform molding control according to the melting state of the molding surface.

[0016] Second Embodiment Next, a 3D additive manufacturing system 200 according to a second embodiment of the present invention will be described with reference to Figures 2 and subsequent drawings. The 3D additive manufacturing system 200 according to this embodiment detects the amount of thermoelectrons emitted from a surface to be built that has been irradiated with a modeling beam. The thermoelectrons are detected by detecting the current output from a positively charged metal plate. In this embodiment, the metal plate is supported on an insulator on a building table and positioned close to the surface to be built, and the connection between the metal plate and the current detection unit is positioned away from the surface to be built.

[0017] 2 is a block diagram showing the configuration of a 3D additive manufacturing system 200 according to this embodiment. The 3D additive manufacturing system 200 includes an additive manufacturing device 201, a thermoelectron detection unit 205, and a control unit 206.

[0018] (Configuration of the additive manufacturing apparatus) In the additive manufacturing apparatus 201, an electron gun 212 is attached to a vacuum vessel 211, and a building frame (building box) 213 having a circular or rectangular cross section is provided inside the vacuum vessel 211. A Z-drive mechanism 214 is located below and inside the building frame 213, and is capable of moving a powder table 215 in the Z direction (up and down). A heat-resistant flexible seal 216 is located in the gap between the building frame 213 and the powder table 215, and the flexible seal 216 and the inner surface of the building frame 213 provide sliding and airtightness. The inside of the vacuum vessel 211 is evacuated by a vacuum pump (not shown), and a vacuum is maintained.

[0019] Unsintered metal powder 223 is spread on the powder table 215, and a building plate 219 is placed on the powder table 215 to build the object 218 in a raised state. The building plate 219 is grounded to the powder table 215, which is at GND potential, via a GND line 220 to prevent it from floating electrically. The layered object 218 is formed on the building plate 219, and as each layer is built, a linear funnel 222 filled with metal powder 221 moves left and right in the figure to spread the metal powder 221 to approximately the same height as the upper surface of the building frame table 213. Powder is replenished into the linear funnel 222 as needed from a powder hopper (not shown).

[0020] The surface layer of the spread metal powder 223 is two-dimensionally melted by the electron beam from the electron gun 212, and the resulting layers are superimposed to form the object 218. On the building plate 219, the metal powder 224 spread in the area other than the object 218 is pre-sintered by the electron beam from the electron gun 212, and is therefore electrically conductive.

[0021] A grounded protective cover 225 is attached between the build surface 232 and the electron gun 212 to prevent metal vapor generated during build and metal spatter caused by fireworks from being deposited on the inner walls of the chamber. The protective cover 225 also serves as a radiation shield from the high-temperature build surface.

[0022] A thermoelectron detection electrode 230 for detecting thermoelectrons is provided inside the protection cover 225. Thermoelectron detection electrode guides 231, to which the thermoelectron detection electrodes 230 are attached via insulators 217, are attached to both ends of the build frame 213, which experiences little temperature rise during build. The thermoelectron detection electrodes 230 are made of a metal electrode such as Ti, which emits a small amount of secondary electrons due to electron excitation. The insulators 217, which electrically insulate the thermoelectron detection electrode 230 from ground potential, are positioned far from the build surface 232, thereby suppressing a decrease in insulation resistance due to temperature rise.

[0023] A voltage-superimposed current amplifier 251 is connected to the thermoelectron detection electrode guide 231 via a current introduction terminal 228. The voltage-superimposed current amplifier 251 is a circuit that converts the amount of thermoelectrons attracted by the thermoelectron detection electrode 230 into a current. A low voltage of +several volts or less is applied to the voltage-superimposed current amplifier 251 so that it has almost no effect on the primary electron beam relative to GND and so that only thermoelectrons with lower energy than secondary electrons are attracted. As a result, thermoelectrons emitted from the melting point of the model 218 are attracted to the thermoelectron detection electrode 230 by a positive potential gradient, and the amount of electrons is detected as a current.

[0024] Applying a positive voltage improves the detection efficiency of thermoelectrons even when the electron beam is turned off or when the laser beam is melting. It is also possible to change the applied voltage depending on whether the temperature is relatively low or high. For example, by increasing the positive voltage when the temperature is relatively low and decreasing the voltage when the temperature is relatively high, the device can be used across the entire temperature range without changing the gain of the current amplifier. Specifically, thermoelectrons are detected by the electrode 230, a positively charged metal plate supported by an insulator 217 on the build frame base 213 and positioned close to the build surface, and the current detector 251, which detects the current output from the electrode 230. The connection 228 to the current detector 251 is positioned away from the build surface 232.

[0025] 2, the deposition protection cover 225 is structured to hang below the electron gun 212, but the present invention is not limited to this, and it is also possible to place a guide with GND potential via an insulator on the thermoelectron detection electrode guide 231, and then place the deposition protection cover 225 on top of that. In this way, the thermoelectron detection electrode 230 and the deposition protection cover 225 can be attached together on the printing surface.

[0026] The thermoelectron detection unit 205 has a voltage superimposed current amplifier 251, an A / D conversion unit 252, and a thermoelectron quantity acquisition unit 253. The A / D conversion unit 252 converts the analog current value output from the voltage superimposed current amplifier 251 into a digital current value. Then, the thermoelectron signal generation unit 253 generates a thermoelectron signal corresponding to the thermoelectron quantity and sends it to the control unit 206.

[0027] The control unit 206 includes a comparator 261 for comparing the thermoelectron image signal with a set value, a scan generator 262, and a deflection amplifier 263, and is connected to a deflector (deflection coil) 229 in the electron gun 212. The control unit 206 controls the operation of the electron beam or laser according to the calculated dwell time (timing). That is, the control unit 206 moves the irradiation position at a dwell time (timing) estimated to reach a predetermined value for the amount of thermoelectrons at the irradiation position of the electron beam or laser on the surface to be built. Alternatively, the control unit 206 moves the irradiation position at a speed such that the amount of thermoelectrons at the irradiation position of the electron beam or laser on the surface to be built does not reach a predetermined value. The beam current may be changed instead of the dwell time.

[0028] (Operation) The modeling sequence is a "squeegeeing process" to spread the powder, a "preheating process" to heat the spread powder, a "melting process" for the modeling area, and an "afterheating process" to prepare for the next squeegeeing. This is performed for each layer, and the model is created by repeating this process.

[0029] At the start of the squeegeeing process, the powder table 215 is lowered by the Z drive mechanism 214 so that the upper surface of the shaping plate 219 is positioned slightly lower than the upper surface of the shaping frame base 213. This slight lowering ΔZ corresponds to the subsequent layer thickness in the Z direction. The linear funnel 222 filled with metal powder 221 is moved along the upper surface of the shaping plate 219 to the opposite side (right side in the figure), and the metal powder 221 of ΔZ amount is spread on and around the shaping plate 219.

[0030] In the preheating step, the metal powder 221 spread on the shaping plate 219 is heated by irradiating an electron beam from the electron gun 212 in an area slightly smaller than the shaping plate 219, thereby causing preliminary sintering.

[0031] In the melting process, a previously prepared design object is sliced ​​at ΔZ intervals, and the two-dimensional shape is melted by an electron beam from the electron gun 212. The electron beam is scanned according to a preset scan path, and each point is melted with a preset 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 is melted, a thermoelectron signal from the voltage superimposed current amplifier 251 is detected.

[0032] The beam is irradiated at the start point of the scan, and the comparison unit 261 compares the set value of the thermionic signal with the thermionic signal from the thermionic detection unit 205. The moment the thermionic signal reaches the set value, a trigger signal is input to the scan generator 262, and the electron beam moves in the scan direction by the scan pitch (SP). At the next point, the thermionic signal similarly stays in that position until it reaches the set value, and then moves to the next point. In this way, movement is repeated at each point until the thermionic signal reaches the set value, and the two-dimensional shape is melted.

[0033] In the after-heating process, the build surface 232 of the build plate 219 covered with the spread powder 224 is placed at approximately the same height as the upper surface of the build frame 213, and the electron beam from the electron gun 212 is irradiated onto an area slightly narrower than the entire upper surface of the build plate 219, thereby raising the temperature in advance to a temperature at which the metal powder 221 is pre-sintered. This makes it possible to suppress scattering of the metal powder 221 due to charging up.

[0034] In the 3D additive manufacturing system 200, an example is shown in which the additive manufacturing device 201 and the control unit 206 are arranged in close proximity to each other, but the additive manufacturing device 201 and the control unit 206, or part of the control unit 206, may also be arranged remotely and exchange information via wired or wireless communication.

[0035] <Reason for detecting the amount of thermoelectrons at the melting position> Figure 3 is a graph showing the relationship between the melting temperature at the irradiation position and the amount of thermoelectrons. Figure 3 shows the results of calculating the amount of thermoelectrons generated from a φ0.5 mm region of a Ti64 alloy as a function of temperature. As can be seen from Figure 3, the amount of thermoelectrons increases exponentially with increasing temperature. For example, in the case of Ti64, the build surface is heated to approximately 750°C during preheating, and the amount of thermoelectrons emitted from the entire region is approximately 0.5 pA (picoamperes). In contrast, the amount of thermoelectrons emitted from a φ0.5 mm region at the melting point (approximately 1650°C) is approximately 1 μA (microamperes), and when the melting temperature reaches approximately 2000°C, the amount is approximately 100 μA (microamperes), and when the melting temperature reaches approximately 2400°C, the amount of thermoelectrons generated is more than 4 mA (milliamperes).

[0036] On the other hand, the thermoelectrons emitted when heating the printing surface during pre-heating and after-heating are 2 If the temperature is 1000°C, the current is small, at around 20 nA (nanoamperes). During melting, temperatures other than the melting point are lower than this, so the thermoelectron signal detected during melting reflects the temperature of the melting point (melt pool), which is at a high temperature.

[0037] <Processing Procedure of 3D Additive Manufacturing System> Fig. 4 is a flowchart showing the processing procedure of the 3D additive manufacturing system 200. This flowchart is executed by a CPU (Central Processing Unit) of the control unit 206 using RAM (Random Access Memory), and realizes the components of Fig. 2 so as to operate the 3D additive manufacturing device.

[0038] In step S401, the control unit 206 waits for the acquisition of the additive manufacturing data. When the acquisition of the additive manufacturing data is completed, in step S403, the control unit 206 instructs the additive manufacturing device 201 to perform squeegeeing of the additive manufacturing powder.

[0039] Once the squeegeeing is completed, in step S405, the additive manufacturing apparatus 201 is instructed to perform preheating to heat the laid powder.

[0040] When the preheating is complete, the control unit 206 instructs the additive manufacturing apparatus 201 to "melt" the area to be molded in step S407. In step S409, the control unit 206 instructs the additive manufacturing apparatus 201 to perform "afterheating (AH)" in preparation for the next squeegeeing, and the additive manufacturing apparatus 201 positions the manufacturing surface 232 at approximately the same height as the upper surface of the molding frame 213, and irradiates it with an electron beam from the electron gun 212 to heat the metal powder 221 to a temperature at which it is temporarily sintered.

[0041] When the afterheating is completed, the control unit 206 instructs the additive manufacturing device 201 to lower the modeling plate by one layer in step S411. In step S413, it is determined whether the additive manufacturing is complete. If not, the process returns to step S403 and the modeling of the next layer is repeated. In step S407, the "melting" of the modeling object area is performed as the modeling surface monitoring method of this embodiment, with the processes of steps S471 to S477 being performed.

[0042] In step S471, the control unit 206 acquires a thermoelectron signal at the melting point. In step S473, the control unit 206 compares the acquired thermoelectron signal with a set value. If the thermoelectron signal exceeds the set value, the process proceeds to step S475, where melting control is performed to move to the next melting point. The set value is derived in advance from a conversion table between thermoelectron signals and temperature, and the deflector 229 is controlled to maintain a constant melting temperature. Even in dot melting without a predetermined scan path, the timing of movement to the next point is determined so that the thermoelectron signal value reaches a constant value. This allows the thermoelectron emission during melting to be controlled to be constant, thereby maintaining a constant melting temperature and enabling uniform melting across the build surface, leading to reduced defects.

[0043] (Conversion Table) Fig. 5 shows an example of a conversion table for calculating the set value. The conversion table is used to convert the amount of thermoelectrons into the melting temperature. The conversion table is generated as follows. The relationship between the temperature T of a radiation thermometer or the like and the thermoelectron current I detected by the voltage superimposed current amplifier 251 is measured in advance, and fitting is performed using the following equation (1), where a and b are constants: I = a T 2 ・e b / T (1) Alternatively, in the expanded equation shown in the following 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 linear equation. The linear equation can be determined relatively easily using the least squares method, etc. 2 )=b·1 / T+ln a (2) Using equation (1) that determines a and b, the relationship between the thermoelectron current and temperature is determined and converted to temperature.

[0044] Since it is difficult to perform the above-mentioned measurements in the molten state, a relatively large area is scanned to measure the temperature of that area and the thermoelectrons from that area, and the area is expanded to a melt size such as a beam size to determine the relationship between the temperature and the thermoelectrons in the required spot area.In addition, when the relationship between temperature and the thermoelectrons is determined, the thermoelectron signal for the required temperature can be calculated in advance as a threshold value, and the value can be used as a parameter to realize the melting process at the required melting temperature.

[0045] By using such a conversion table, the value of the thermoelectrons at which the electron beam should move to the next point can be calculated from the upper limit temperature at the melting point, and the value of the thermoelectrons can be set as the set value. In addition, multiple such set values ​​can be stored according to the type of metal powder, and can be read and used according to the metal powder information input before molding.

[0046] As described above, in this embodiment, the scan attributes (scan pitch, scan speed, line pitch, etc.) are controlled according to the value of the thermoelectron signal. The thermoelectron signal value at each melting point is kept constant. The dwell time of the electron beam is changed for each melting point so that the integrated value of the thermoelectron signal remains constant.

[0047] This makes it possible to easily and accurately keep the melting temperature at each melting point on the modeling surface constant, thereby improving modeling quality.

[0048] Since electron beams do not respond quickly to current control, it is more effective to change the timing or scan speed rather than the current value. On the other hand, when using a laser, power control (control by changing the pulse width) can be used. Furthermore, by making the scan pitch finer, it is possible to eliminate variations in the melting temperature across the entire build surface.

[0049] Conventionally, control that keeps the residence time of the electron beam constant at each melting point or control that applies an empirically determined correction to the residence time near the turning point has not been able to achieve optimal melting control for objects with complex shapes or for surfaces on which the powder particle density varies at different points. However, according to this embodiment, it is possible to perform high-quality molding even for objects under such conditions.

[0050] Third Embodiment Next, a 3D additive manufacturing system according to a third embodiment of the present invention will be described with reference to Figures 6 and 7. The 3D additive manufacturing system according to this embodiment differs from the second embodiment in that it performs simulation control rather than feedback control. Since the other configurations and operations are the same as those of the second embodiment, the same configurations and operations are denoted by the same reference numerals and detailed descriptions thereof will be omitted.

[0051] When the amount of thermoelectrons generated is simulated according to the molding conditions, it shows a good match with the thermoelectron image. For example, a simulation image can be generated in which the shading changes line by line, as shown in image 601 in Figure 6. Therefore, the residence time of the electron beam at each point is calculated so that a thermoelectron image 602 with no shading is output. As a result, the residence time of the electron beam at each point on the molding surface becomes as shown in image 603. Melting is controlled according to the calculated residence time in this way to mold the part.

[0052] That is, the thermoelectron image during the melting process is simulated to determine the input energy (residence time, beam current, etc.) at each melting point so that the amount of thermoelectrons at each melting point reaches a set value (constant value), a scan path is created for that input energy, and melting control is performed under those conditions.

[0053] 7 is a diagram showing the configuration of a three-dimensional additive manufacturing system 700 according to this embodiment. The control unit 706 of the three-dimensional additive manufacturing system 700 includes a storage unit 761, a thermoelectron estimation unit 762, and a timing calculation unit 763. The storage unit 761 stores a thermoelectron image detected by the thermoelectron detection unit 205 in association with the manufacturing data (electron beam scan trajectory data).

[0054] The thermoelectron estimation unit 762 estimates a thermoelectron image by referring to the data stored in the storage unit 761. For example, when the same (or similar) object is repeatedly formed, the thermoelectron image can be estimated using a thermoelectron signal detected in the past.

[0055] The timing calculation unit 763 calculates the stay time (timing) using the estimated thermoelectron image. Since the timing calculation unit 763 outputs a trigger signal at the calculated timing, a comparator or the like is not required and the trigger signal is input directly to the scan generator 262.

[0056] The control unit 206 controls the operation of the electron beam or laser according to the calculated dwell time (timing). That is, the control unit 206 moves the irradiation position at a dwell time (timing) estimated to be when the amount of thermoelectrons at the electron beam or laser irradiation position on the surface to be built reaches a predetermined value. Alternatively, the control unit 206 moves the irradiation position at a speed that does not cause the amount of thermoelectrons at the electron beam or laser irradiation position on the surface to be built to reach a predetermined value. The beam current may be changed instead of the dwell time.

[0057] This allows the melting temperature to be controlled to a constant value regardless of the size or location of the melted area during the melting process. Optimizing the melting temperature also enables the creation of objects of consistently stable quality.

[0058] [Fourth Embodiment] Next, a three-dimensional additive manufacturing device according to a fourth embodiment of the present invention will be described with reference to Fig. 8. The three-dimensional additive manufacturing device according to this embodiment differs from the second and third embodiments in that it combines feedback control (second embodiment) with simulation control (third embodiment). The other configurations and operations are the same as those of the second embodiment, and therefore the same configurations and operations are denoted by the same reference numerals and detailed description thereof will be omitted.

[0059] For example, this embodiment is effective when the shape is complex and it is difficult to completely reproduce the thermoelectron signal by simulation. For example, in the printing area, the inner part where the thermoelectron signal is estimated with high accuracy is calculated in advance and controlled, and the outer part where the estimation accuracy is thought to be low is compared with the set value for the thermoelectrons detected in real time.

[0060] 8 is a diagram showing the configuration of a three-dimensional additive manufacturing system 800 according to this embodiment. The three-dimensional additive manufacturing system 800 includes a timing calculation unit 763 and a selection unit 864.

[0061] The timing calculation unit 763 estimates the amount of thermoelectrons emitted from the surface being modeled through simulation. The selection unit 864 selects, for each region on the surface being modeled, either the estimated residence time (timing) or the timing at which the detected thermoelectron signal reaches a preset value according to a preset criterion, and passes this to the scan generator 262.

[0062] For example, the selection unit 864 selects the residence time (timing) from the timing calculation unit 763 near the center of the printing surface 232, and selects the timing from the comparator 261 that outputs the timing at which the actual thermoelectron signal reaches a set value near the periphery of the printing surface 232. Conversely, the selection unit 864 may select the timing signal from the timing calculation unit 763 near the periphery of the printing surface 232, and select the timing signal from the comparator 261 near the center of the printing surface 232. For example, the selection unit 864 may determine the complexity for each region of the printing surface, and select the timing signal from the comparator 261 based on the actual thermoelectron signal in regions where the complexity is equal to or greater than a predetermined value, and select the timing signal from the timing calculation unit 763 in regions where the complexity is less than the predetermined value.

[0063] According to this embodiment, the melting temperature can be controlled with higher precision so as to be always constant regardless of the size or location of the melted region in the melting process. Furthermore, by optimizing the melting temperature, it is possible to form objects of consistently stable quality.

[0064] Fifth Embodiment Next, a three-dimensional additive manufacturing apparatus according to a fifth embodiment of the present invention will be described with reference to Fig. 9. The three-dimensional additive manufacturing apparatus 900 according to this embodiment differs from the third embodiment in that it uses artificial intelligence to estimate a thermoelectron image. Since the other configurations and operations are the same as those of the third embodiment, the same configurations and operations are denoted by the same reference numerals and detailed descriptions thereof will be omitted.

[0065] The machine learning unit 961 performs machine learning using, as training data, the thermoelectron signal detected by the thermoelectron detection unit 205 and the correspondence between the thermoelectron image data and the shaping data stored in the external database 970, to generate a thermoelectron image estimation model. The thermoelectron estimation unit 962 estimates a thermoelectron image using the generated thermoelectron image estimation model.

[0066] According to this embodiment, the melting temperature can be controlled with higher precision so as to be always constant regardless of the size or location of the melted region in the melting process. Furthermore, by optimizing the melting temperature, it is possible to form objects of consistently stable quality.

[0067] [Other Embodiments] In the above embodiment, the case of an electron beam type PBF was shown, but the melting temperature can also be measured by thermions during melting with a wire or powder type DED. Also, with a laser type, thermions can be measured in a vacuum, so the melting temperature can be measured during melting. In the case of laser beam melting, thermions are detected even during beam irradiation.

[0068] Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the above embodiments. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the technical scope of the present invention. Furthermore, systems or devices that combine the separate features included in each embodiment in any manner are also included in the technical scope of the present invention.

[0069] The present invention may be applied to a system consisting of multiple devices or to a single device. Furthermore, the present invention may also be applied when an information processing program that realizes the functions of the embodiments is supplied to a system or device and executed by a built-in processor. The technical scope of the present invention also includes a program installed on a computer to realize the functions of the present invention, a medium storing the program, a server from which the program is downloaded, and a processor that executes the program. In particular, the technical scope of the present invention includes at least a non-transitory computer-readable medium storing a program that causes a computer to execute the processing steps included in the above-described embodiments.

Claims

1. A three-dimensional additive manufacturing system that performs additive manufacturing in a vacuum using a modeling beam, comprising: a thermoelectron detection unit that detects the amount of thermoelectrons emitted from a modeling surface when the modeling beam is irradiated onto the modeling surface; and a control unit that controls the operation of the modeling beam in accordance with the amount of thermoelectrons.

2. A three-dimensional additive manufacturing system as described in claim 1, wherein the control unit moves the irradiation position at a timing when the amount of thermoelectrons at the irradiation position of the manufacturing beam on the manufacturing surface reaches a predetermined value.

3. A three-dimensional additive manufacturing system as described in claim 1, wherein the control unit moves the irradiation position at a speed such that the amount of thermoelectrons at the irradiation position of the electron beam or laser on the surface to be built does not reach a predetermined value.

4. A three-dimensional additive manufacturing system as described in claim 1, further comprising an estimation unit that estimates the amount of thermoelectrons emitted from the surface being built during the manufacturing process through simulation, and the control unit controls the operation of the manufacturing beam according to the estimated amount of thermoelectrons.

5. A three-dimensional additive manufacturing system as described in claim 1, further comprising an estimation unit that estimates the amount of thermoelectrons emitted from the surface being built through simulation, and the control unit controls the operation of the building beam according to the estimated amount of thermoelectrons, and moves the irradiation position at the timing when the amount of thermoelectrons at the irradiation position of the building beam on the surface being built reaches a predetermined value.

6. A three-dimensional additive manufacturing system as described in claim 1, further comprising an estimation unit that estimates the amount of thermoelectrons emitted from the surface being built through simulation, and the control unit controls the operation of the electron beam or laser according to the estimated amount of thermoelectrons, while moving the irradiation position of the building beam on the surface to be built at a speed such that the amount of thermoelectrons at the irradiation position does not reach a predetermined value.

7. The three-dimensional additive manufacturing system according to claim 1, wherein the thermoelectron detection unit comprises: a positively charged metal plate; and a current detection unit that detects the current output from the metal plate.

8. A three-dimensional additive manufacturing system as described in claim 7, wherein the metal plate is supported on an insulator on a building table and positioned close to the building surface, and the connection between the metal plate and the current detection unit is positioned away from the building surface.

9. A control method for a three-dimensional additive manufacturing system that performs additive manufacturing in a vacuum using a manufacturing beam, comprising: a thermoelectron detection step of detecting the amount of thermoelectrons emitted from the manufacturing surface when the manufacturing beam is irradiated onto the manufacturing surface; and a control step of controlling the operation of the manufacturing beam in accordance with the amount of thermoelectrons.

10. A control program for a three-dimensional additive manufacturing system that performs additive manufacturing in a vacuum using a manufacturing beam, the control program causing a computer to execute the following steps: a thermoelectron detection step that detects the amount of thermoelectrons emitted from a manufacturing surface when the manufacturing beam is irradiated onto the manufacturing surface; and a control step that controls the operation of the manufacturing beam according to the amount of thermoelectrons.

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