JP7746751B2 - Three-dimensional modeling method and three-dimensional modeling device - Google Patents

Description

This disclosure relates to a three-dimensional printing method and a three-dimensional printing device.

Patent Document 1 discloses an apparatus and method for forming a three-dimensional object by irradiating powder material spread evenly inside a chamber with an electron beam, melting and solidifying the powder material.

Patent No. 6101707

The printing quality of parts manufactured by a 3D printing device is affected by various factors during the printing operation. For example, printing quality is affected by the amount of heat applied per unit volume of the object to be printed (hereinafter referred to as "heat input"). For example, if the heat input is too low, the powder material will not melt, leaving defects, while if the heat input is too high, the powder material will melt away. The heat input depends on parameters that determine the heat input (e.g., beam output, speed, etc.). However, because it is difficult to measure the parameters that determine the heat input during actual printing operations, the actual heat input was unknown. As a result, it was not possible to determine whether the printed object had the desired printing quality.

This disclosure therefore describes a three-dimensional printing method and a three-dimensional printing device that can ensure that the object produced has the desired printing quality.

A three-dimensional modeling method according to one aspect of the present disclosure comprises: a first preparatory step of capturing a video including the energy beam irradiation point by photographing the plate while irradiating the plate with an energy beam in accordance with a beam irradiation setting including a heat input setting indicating an allowable range for a parameter that determines the amount of heat input imparted to a powder material by the energy beam and trajectory information that determines the irradiation position of the energy beam; a second preparatory step of analyzing the video to obtain measurement results for the parameter that determines the amount of heat input; a third preparatory step of determining whether the measurement results are within the allowable range; and a modeling step of spreading the powder material evenly on the plate and irradiating the spread powder material with the energy beam to form a three-dimensional model.

This three-dimensional printing method captures a video of the point irradiated with an energy beam according to beam irradiation settings, which include information defining the allowable range of parameters defining the amount of heat input and the movement of the beam. The three-dimensional printing method analyzes the video to obtain the measurement results of the parameters. The three-dimensional printing method determines whether the measurement results are within the allowable range. In this case, it is determined whether the measurement results of the actual parameters are within the allowable range of the parameters. If the measurement results are within the allowable range, it is determined that the range of heat input to the three-dimensional object is within the allowable range. This makes it possible to ensure that the object has the desired printing quality.

The second preparation step may involve counting the number of frames in which the energy beam is continuously visible by determining whether each frame of the video contains an energy beam irradiation point, and obtaining the speed at which the energy beam irradiation point moves along the trajectory as a measurement result based on the number of frames in which the energy beam is visible, the length of the energy beam trajectory, and the frame rate of the video. In this case, the actual speed at which the energy beam is irradiated is obtained as the measurement result. This makes it possible to more precisely ensure that the heat input, which is determined by the speed, is within an allowable range. Therefore, it becomes possible to ensure that the molded object has the desired molding quality.

In the first preparation step, the energy beam may be irradiated so that its trajectory is circular. In this case, even in a narrow area on the plate, the distance irradiated by the energy beam becomes longer, making it possible to more accurately determine the irradiation trajectory. As a result, measurement results can be made more accurate.

The first preparation step may involve irradiating the energy beam so that the speed at which the energy beam moves along the trajectory is constant. In this case, the energy beam appears in the video frames at a constant speed while being irradiated. As a result, more accurate measurement results can be obtained.

A three-dimensional printing apparatus according to one aspect of the present disclosure includes an irradiation unit that irradiates an energy beam onto a plate in accordance with a beam irradiation setting that includes a heat input setting indicating the allowable range of a parameter that determines the amount of heat input imparted to a powder material by the energy beam and trajectory information that determines the irradiation position of the energy beam; an imaging unit that photographs the plate and outputs a video that includes the energy beam irradiation point; and a control unit that analyzes the video to obtain measurement results of the parameter that determines the amount of heat input and determines whether the measurement results are within the allowable range. The irradiation unit spreads the powder material evenly on the plate and irradiates the spread powder material with an energy beam to form a three-dimensional object. For the reasons described above, this three-dimensional printing apparatus can ensure that the object has the desired printing quality.

The control unit may include a counting unit that counts the number of frames in which the energy beam is continuously captured by determining whether the energy beam irradiation point is included in each frame of the video, and a speed calculation unit that obtains the speed at which the energy beam irradiation point moves along the trajectory as a measurement result based on the number of frames in which the energy beam is captured, the length of the energy beam trajectory, and the frame rate of the video. Even in this case, it is possible to ensure that the modeled object has the desired modeling quality for the reasons described above.

The control unit may control the irradiation of the energy beam by the irradiation unit so that the trajectory of the energy beam is circular. Even in this case, the measurement results can be made more accurate for the reasons described above.

The control unit may control the irradiation of the energy beam by the irradiation unit so that the speed at which the energy beam moves along the trajectory is constant. Even in this case, the measurement results can be made more accurate for the reasons described above.

The three-dimensional printing method and three-dimensional printing device disclosed herein can ensure that the object produced has the desired printing quality.

FIG. 1 is a schematic diagram showing the configuration of a three-dimensional modeling apparatus. FIG. 2 is a block diagram showing the main configuration related to parameter measurement. FIG. 3 is a diagram illustrating an example of a hardware configuration of the control unit. 4A and 4B are diagrams showing examples of trajectory information, in which Fig. 4A shows a circular trajectory, Fig. 4B shows an intermittent trajectory, and Fig. 4C shows a trajectory in which acceleration and deceleration are performed. FIG. 5 is a flowchart illustrating an example of processing by the counting unit. FIG. 6 is a flowchart showing the operation of the three-dimensional modeling apparatus.

The three-dimensional printing method and three-dimensional printing apparatus disclosed herein will be described in detail below with reference to the drawings. Note that identical or equivalent parts in each drawing will be designated by the same reference numerals, and duplicate explanations will be omitted.

The three-dimensional rotational additive manufacturing apparatus (hereinafter referred to as "three-dimensional modeling apparatus 1") shown in Figure 1 is a so-called 3D printer that manufactures a model PA (three-dimensional model) from powder material P. The three-dimensional modeling apparatus 1 uses, for example, an electron beam as the energy beam. For example, the three-dimensional modeling apparatus 1 uses the so-called electron gun powder bed fusion method.

The powder material P is a metal powder, such as titanium-based metal powder, Inconel powder, or aluminum powder. Furthermore, the powder material P is not limited to metal powder. It may also be a powder containing carbon fiber and resin, such as CFRP (Carbon Fiber Reinforced Plastics). The powder material P may also be other electrically conductive powders. The powders disclosed herein are not limited to those that are electrically conductive. For example, if a laser is used as the energy beam, the powder material P does not need to be electrically conductive.

The three-dimensional modeling apparatus 1 applies energy to the powder material P. In other words, the three-dimensional modeling apparatus 1 increases the temperature of the powder material P. As a result, the powder material P melts or sinters. When the three-dimensional modeling apparatus 1 stops applying energy, the temperature of the powder material P drops, causing it to solidify. In other words, the three-dimensional modeling apparatus 1 produces a model PA by repeatedly applying and stopping energy application multiple times. Note that, in this disclosure, "solidifying the powder material P" includes both solidifying the powder material P that has been heated to a temperature higher than its melting point and sintering it by heating it to a temperature lower than its melting point. The model PA is, for example, a mechanical part. The model PA may also be other structures.

The three-dimensional modeling apparatus 1 has a drive unit 2, a processing unit 3, a control unit 4, a housing 5, a window unit 6, and a camera 7 (photographing unit). The drive unit 2 performs various operations required for modeling. The processing unit 3 processes powder material P to obtain a model PA. The processing of powder material P includes supplying the powder material P, preheating the powder material P, and modeling the powder material P. The control unit 4 controls the entire three-dimensional modeling apparatus 1. The housing 5 is supported by multiple columns. The housing 5 forms a modeling space S. The modeling space S is an airtight space that can be decompressed to process the powder material P using the processing unit 3. The window unit 6 is a viewing window that allows the modeling space S to be viewed from outside the three-dimensional modeling apparatus 1. The window unit 6 is provided in the housing 5. The camera 7 photographs the top of a plate 51, which will be described later.

A plate 51 and a modeling tank 52 are arranged in the modeling space S. The plate 51 is a processing stage on which the modeling process is carried out. The plate 51 is, for example, a circular plate, and powder material P, the raw material for the model PA, is placed on the plate 51. The plate 51 is positioned so that its central axis overlaps with the central axis of the housing 5. A drive unit 2 is connected to the plate 51. Therefore, the plate 51 rotates and moves linearly along the rotation axis due to the drive unit 2. The modeling tank 52 is a container that holds the powder material P. The modeling tank 52 is positioned to surround the plate 51.

The drive unit 2 rotates and elevates the plate 51. The drive unit 2 has a rotation drive mechanism 21 and an elevation drive mechanism 22. The rotation drive mechanism 21 rotates the plate 51. The upper end of the rotation drive mechanism 21 is connected to the plate 51. The lower end of the rotation drive mechanism 21 is attached to a drive source. The elevation drive mechanism 22 elevates and lowers the plate 51 relative to the modeling tank 52. This elevation is along the rotation axis of the rotation drive mechanism 21. Note that the drive unit 2 is not limited to the above mechanism, as long as it is a mechanism that can rotate and elevate the plate 51.

The processing unit 3 is disposed on the plate 51. The processing unit 3 faces the main plate surface 51a of the plate 51. The processing unit 3 has a feeder 3a, a heater 3b, and a beam source 3c (irradiation unit). The feeder 3a supplies the powder material P. The heater 3b preheats the powder material P. The beam source 3c shapes the powder material P.

The feeder 3a supplies powder material P to the plate 51. For example, the feeder 3a has a raw material tank and a leveling unit. The raw material tank stores powder material P and supplies powder material P to the plate 51. The leveling unit levels the surface of the powder material P on the plate 51. For example, the surface layer of powder material P on the plate 51 comes into contact with the leveling unit as the plate 51 rotates and is spread and leveled. Note that the three-dimensional modeling device 1 may have a roller unit, a rod-shaped member, a brush unit, etc. instead of the leveling unit. The feeder 3a forms a supply area on the plate's main surface 51a. The supply area is an area where the powder material P is supplied to the plate 51 and leveled. For example, the supply area has a rectangular shape with the longitudinal direction aligned with the diameter (radial direction) of the plate 51, but is not limited to this.

The heater 3b heats the powder material P placed on the plate 51. The heater 3b raises the temperature of the powder material P by radiating heat. For example, an infrared heater may be used as the heater 3b. Preheating here refers to a process of heating the powder material P so that its temperature in the preheating area is higher than that in the supply area. This heating process may also be, for example, a process of pre-sintering the powder material P. Pre-sintering is a state in which the powder material P diffuses and bonds at its smallest point due to the diffusion phenomenon. For example, the heater 3b heats the powder material P to a temperature equal to or greater than half the melting point of the powder material P. This is because the diffusion phenomenon of sintering generally becomes active at a temperature equal to or greater than half the melting point. For example, if the powder material P is titanium, the pre-sintering temperature is 700°C to 800°C. The melting point of titanium alloys is approximately 1500°C to 1600°C. If the powder material P is aluminum, the pre-sintering temperature is 300°C. The melting point of aluminum is approximately 660°C. The heater 3b forms a preheating region on the plate main surface 51a. The preheating region is a region where the temperature of the powder material P is increased. The preheating region may be, for example, fan-shaped, but is not limited to this.

For example, the beam source 3c irradiates the powder material P placed on the plate 51 with an electron beam. The beam source 3c is, for example, an electron gun. The electron gun generates an electron beam according to the potential difference generated between the cathode and the anode. The beam source 3c forms a build region on the plate main surface 51a. The build region is an area where the temperature of the powder material P is increased, and this temperature is higher than the temperature in the preheating region. In other words, the temperature of the powder material P in the build region is a temperature (sintering temperature, melting temperature) at which a build object PA can be formed. The beam source 3c irradiates the electron beam to a desired portion within the build region. The shape of the build region is, for example, circular, but is not limited to this. The build region may or may not coincide with the irradiation range (irradiation range) of the beam source 3c.

The positional relationship between the supply area, preheating area, and building area corresponds to the positional relationship between the feeder 3a, heater 3b, and beam source 3c. The supply area, preheating area, and building area may be formed in this order along the rotation direction of the plate 51. The areas occupied by the supply area, preheating area, and building area may be changed as appropriate.

The control unit 4 controls the operation of the drive unit 2 and the processing unit 3 to form a three-dimensional object. The lifting drive mechanism 22 moves the plate 51 upward. The plate 51 is positioned at the top of the modeling tank 52. The rotation drive mechanism 21 rotates the plate 51. The feeder 3a supplies powder material P to the plate 51 and levels the surface layer of the powder material P. The powder material P is supplied while rotating together with the plate 51. The heater 3b preheats the powder material P before it is irradiated with the electron beam. The powder material P is heated while rotating together with the plate 51. The beam source 3c irradiates the powder material P with the electron beam. This melts or sinters the powder material P, and the model PA is formed. The lifting drive mechanism 22 lowers the plate 51. The plate 51 descends as the modeling of the model PA progresses. The descent of the plate 51 may be synchronized with the rotation of the plate 51, but does not have to be completely synchronized. Once the modeling of all layers is complete, the modeling of the object PA is complete.

The control unit 4 also measures parameters that define the amount of heat input imparted to the powder material P by the electron beam. The parameters include, for example, the output power of the electron beam and the scanning speed. The scanning speed is the speed at which the irradiation point of the electron beam moves along the trajectory. The amount of heat input is the amount of heat imparted per unit volume of the molded object PA and depends on the parameters. Figure 2 is a block diagram showing the main components involved in measuring the parameters. As shown in Figure 2, the control unit 4 has a memory unit 41, a beam control unit 42, an acquisition unit 43, a counting unit 44, a distance calculation unit 45, a speed calculation unit 46, and a comparison unit 47. The control unit 4 is electrically connected to the beam source 3c and the camera 7.

The memory unit 41 stores heat input settings and beam irradiation settings. The heat input setting is the allowable range of a parameter that defines the amount of heat input imparted to the powder material P by the electron beam. The allowable range is defined by the reference value and allowable error of the parameter. The allowable range is defined, for example, as a scanning speed of 960 mm/sec and an allowable error of ±20 mm/sec. The beam irradiation settings include, for example, the output of the electron beam, the scanning speed, and trajectory information that defines the irradiation position of the electron beam. The trajectory information defines, for example, the start and end points of the irradiation position and the path along which the irradiation position moves. Details of the trajectory information will be described later.

The beam control unit 42 controls the irradiation of the electron beam. The beam control unit 42 outputs a control signal φ to the beam source 3c according to the beam irradiation settings. The beam source 3c irradiates the electron beam onto the plate 51 in accordance with the control signal φ. When measuring parameters, the plate 51 is not rotating and its elevation position is fixed. Furthermore, no powder material P is supplied onto the plate 51. In other words, the beam source 3c irradiates the electron beam onto the main plate surface 51a of the plate 51.

The camera 7 outputs a video m captured on the plate 51 to the control unit 4. The video m includes images (frames) of the plate 51 taken before the electron beam irradiation begins, while the electron beam is being irradiated, and after the electron beam irradiation has stopped. The frame rate (number of frames per second) of the video m is not limited and may be, for example, 240 frames/sec. The camera 7 may be, for example, a digital camera or a high-speed camera. The camera 7 captures images of the plate 51 from outside the 3D printing device 1 through the window 6.

The acquisition unit 43 acquires the video m from the camera 7. The video m includes the irradiation point of the electron beam. The irradiation point is the position on the plate 51 where the electron beam is irradiated.

The counting unit 44 determines whether or not the moving image m contains an irradiation point of the electron beam for each frame. When the electron beam is irradiated onto the plate 51, the irradiation point becomes hot and emits light. In this embodiment, light emission is described as a state in which there are a predetermined number or more pixels with a brightness higher than the brightness threshold. In the moving image m, light emission appears continuously in the images while the electron beam is being irradiated. The counting unit 44 counts the number of frames in which the electron beam is continuously displayed. Details of the processing by the counting unit 44 will be described later.

The distance calculation unit 45 calculates the scanning length of the electron beam. The scanning length is the length of the electron beam's trajectory. The distance calculation unit 45 calculates the scanning length through image analysis using the video m. Calculation of the scanning length through image analysis may use known techniques. The distance calculation unit 45 may also obtain values measured by an external measuring device by inputting them from the input device 105. For example, the irradiation marks remaining on the plate 51 after irradiation with the electron beam may be measured.

The speed calculation unit 46 calculates the scanning speed based on the number of frames in which the electron beam is projected, the scanning length of the electron beam, and the frame rate of the video. The speed calculation unit 46 obtains the time over which the electron beam is continuously projected from the frame rate and the number of frames counted by the counter 44. The speed calculation unit 46 calculates the scanning speed from the time over which the electron beam is continuously projected and the scanning length (distance) of the electron beam. The scanning speed is an example of a parameter measurement result.

The comparison unit 47 determines whether the measurement result falls within the allowable range. For example, the comparison unit 47 determines whether the scanning speed falls within the allowable error. If the allowable range is a scanning speed of 960 mm/sec and an allowable error of ±20 mm/sec, the comparison unit 47 determines whether the measured scanning speed falls within the range of 940 to 980 mm/sec.

The control unit 4 is realized by any combination of hardware and/or software. Each function may be realized by two or more physically and/or logically separated devices that are directly and/or indirectly connected to each other.

Figure 3 is a diagram showing an example of the hardware configuration of the control unit. As shown in Figure 3, the control unit 4 may be physically configured as a computer device including a processor 101, memory 102, storage 103, communication device 104, input device 105, output device 106, bus 107, etc. Each function of the control unit 4 is realized by loading specific software (programs) onto hardware such as the processor 101, memory 102, etc., causing the processor 101 to perform calculations and control communication via the communication device 104 or the reading and writing of data from and to the memory 102 and storage 103.

The processor 101 controls the entire computer by running an operating system, for example. The processor 101 may be configured as a central processing unit (CPU). For example, various processes of the control unit 4 may be implemented by the processor 101. The processor 101 also reads programs (program code), software modules, and data from the storage 103 or the communication device 104 into the memory 102 and executes various processes in accordance with these. The function of executing various processes of the control unit 4 may be implemented by a control program stored in the memory 102 and executed by the processor 101. Note that various processes in the control unit 4 may be executed by one processor 101, or may be executed simultaneously or sequentially by two or more processors 101.

Memory 102 is a computer-readable recording medium and may be composed of at least one of, for example, ROM (Read Only Memory), EPROM (Erasable Programmable ROM), EEPROM (Electrically Erasable Programmable ROM), RAM (Random Access Memory), etc.

Storage 103 is a computer-readable recording medium. Storage 103 may be composed of at least one of, for example, a hard disk drive, a flexible disk, a magneto-optical disk, an optical disk such as a CD-ROM (Compact Disc ROM), etc. The above-mentioned storage medium may be, for example, a database including memory 102 and storage 103, a server, or other suitable medium.

The communication device 104 is a device for communicating between computers via a wired and/or wireless network. For example, some of the various processes of the control unit 4 may be implemented by the communication device 104.

The input device 105 is an input device (e.g., a keyboard, etc.) that accepts input from the outside. The output device 106 is an output device (e.g., a display, etc.) that outputs to the outside.

The above devices are connected by a bus 107 for communicating information. The bus 107 may consist of a single bus, or may consist of different buses between the devices.

An example of trajectory information will be described with reference to Figure 4. The trajectory information disclosed herein must satisfy three conditions: it must be a so-called one-stroke trajectory, the scanning speed must not fluctuate during electron beam irradiation, and it must be on the plate 51 and within the field of view of the camera 7. As long as these conditions are met, the shape of the trajectory is not important.

The trajectory information T1 shown in FIG. 4(a) satisfies all three of the above-mentioned conditions. The trajectory information T1 has a path that traces a circle clockwise (CW) from the starting point ST to the end point ED. The diameter D of the circle is, for example, approximately 200 mm. The center of the circle is, for example, on the central axis of the plate 51. The beam source 3c irradiates the plate 51 with an electron beam along the trajectory information T1. As the irradiation point moves along the trajectory information T1, a circular trajectory is left on the plate 51 due to heating. The circular trajectory has a width W (for example, 100 μm) corresponding to the width of the electron beam. Such trajectory information T1 is stored in the memory unit 41. Note that the trajectory indicated by the trajectory information T1 is not limited to an exact circle. The trajectory indicated by the trajectory information T1 may have any shape that allows the length of the trajectory to be obtained. For example, the trajectory information T1 may have a path that traces an ellipse. Furthermore, when the trajectory information T1 defines a circular trajectory indicated by the diameter D, it is not required that the trajectory actually irradiated with the electron beam exactly match the set trajectory. The allowable deviation of the actual trajectory from the trajectory indicated by the trajectory information T1 may be set based on the allowable error in determining the amount of heat input.

The trajectory information T2 shown in Figure 4(b) is a reference example that does not satisfy the above-mentioned conditions. The start point ST and end point ED of the trajectory information T2 are located on the circumference of a circle. The start point ST is located at one end of a straight line LN that passes through the center of the circle, and the end point ED is located at the other end of the straight line LN. The trajectory information T2 has a path T2a that arcs clockwise from the start point ST to the other end of the straight line LN. The trajectory information T2 also has a path T2b that passes along the straight line LN and moves from the other end of the straight line LN to one end. The trajectory information T2 also has a path T2c that arcs counterclockwise from one end of the straight line LN to the end point ED. In the trajectory information T2, the electron beam is not irradiated when passing along the straight line LN. The trajectory information T2 may have movement paths created by multiple beam sources 3c. The trajectory information T2 may include, for example, a first path that arcs clockwise from the start point ST to the end point ED, and a second irradiation point that arcs counterclockwise from the start point ST to the end point ED. Such trajectory information T2 does not satisfy the condition of being drawn in one stroke, and therefore does not need to be stored in the memory unit 41.

The trajectory information T3 shown in Figure 4(c) is a reference example that does not satisfy the above-mentioned conditions. The trajectory information T3 has a single-stroke path that moves in a roughly rectangular shape. In the trajectory information T3, the first, second, third, and fourth sides are defined in order of proximity to the starting point ST, and each side is divided into two sections (first half section and second half section). The trajectory information T3 has a path that decelerates in the second half section A1 of the first side, accelerates in the first half section A2 of the second side, decelerates in the second half section A3 of the second side, and accelerates in the first half section A4 of the third side. This type of trajectory information T3 does not need to be stored in the memory unit 41 because the scanning speed fluctuates.

An example of the processing of the counting unit 44 will be described with reference to the flowchart shown in Figure 5. The counting unit 44 initializes the number of the frame to be processed (hereinafter referred to as "frame No.") and the number of frames F in which the electron beam is continuously projected (step S1). For example, the counting unit 44 sets frame No. to 1 and frame number F to 0. Next, image analysis is performed on the frame to be processed (step S2). For example, the counting unit 44 analyzes the image of frame No. 1 to obtain the luminance of each pixel. The counting unit 44 counts the number of pixels with a luminance equal to or greater than Lu, which is a luminance threshold.

The counting unit 44 determines whether the number of pixels with a brightness of Lu or greater is equal to or greater than the threshold value E (step S3). If the number of pixels with a brightness of Lu or greater is equal to or greater than the threshold value E, this indicates that the frame being processed is an image taken during irradiation with the electron beam. On the other hand, if the number of pixels with a brightness of Lu or greater is less than the threshold value E, this indicates that the frame being processed is an image taken before or after irradiation with the electron beam.

If the number of pixels with a brightness equal to or greater than Lu is equal to or greater than the threshold value E (Yes in step S3), the process proceeds to step S4. The counting unit 44 increments the frame number (step S4). In other words, the counting unit 44 counts up the number of frames by adding 1 to the current frame number. Next, the counting unit 44 increments the frame number (step S5). In other words, the counting unit 44 moves on to the next frame as the frame to be processed.

If the number of pixels with a brightness equal to or greater than Lu is less than the threshold value E (No in step S3), processing proceeds to step S6. The counting unit 44 determines whether the frame number F is 0 (step S6). If the frame number F is 0, this indicates that the frame being processed is before irradiation with the electron beam. In this case (Yes in step S6), processing proceeds to step S5. If the frame number is not 0 (No in step S6), processing ends.

After step S5, processing returns to step S2. As processing returns to step S2, the frames to be processed are switched sequentially. When all processing is completed, the counter 44 outputs the frame number F. The frame number F indicates the number of images currently being irradiated with the electron beam.

Next, the three-dimensional modeling method executed by the three-dimensional modeling device 1 will be described with reference to the flowchart shown in Figure 6. It is assumed that heat input settings and beam irradiation settings are stored in advance in the memory unit 41. Hereinafter, the allowable ranges for the parameters in the heat input settings are assumed to be: scanning speed: 960 [mm/sec], tolerance: ±20 [mm/sec].

As a first preparation step, the three-dimensional modeling apparatus 1 photographs the surface of the plate 51 (step S10). The three-dimensional modeling apparatus 1 photographs the surface of the plate 51 while irradiating the plate 51 with an electron beam according to the beam irradiation settings. The three-dimensional modeling apparatus 1 then acquires a video m including the irradiation point of the electron beam. More specifically, after starting to photograph the surface of the plate 51 with the camera 7, the beam source 3c irradiates the plate 51 with an electron beam. The control unit 4 controls the irradiation of the electron beam by the beam source 3c so that the trajectory of the electron beam is circular. The control unit 4 also controls the irradiation of the electron beam by the beam source 3c so that the scanning speed is constant. If the scanning speed is not constant, the heat input may also vary depending on the scanning speed. In this disclosure, a scanning speed is considered "constant" if it is within a range in which unintended fluctuations in the scanning speed do not affect measurement accuracy. "Constant" is defined as being within the allowable range of the heat input parameter setting. The control unit 4 controls the irradiation of the electron beam so that the scanning speed is within an allowable range. When the irradiation of the electron beam stops, the camera 7 outputs the video m to the control unit 4.

The three-dimensional modeling device 1 analyzes the video m frame by frame (step S11). The three-dimensional modeling device 1 obtains the number of frames F in which the electron beam is continuously captured based on the video m through the process shown in FIG. 4.

The three-dimensional modeling device 1 calculates the scanning length of the electron beam (step S12). The distance calculation unit 45 calculates the scanning length using the video m. The distance calculation unit 45 detects the trajectory of the electron beam, for example, by edge detection on the frame after irradiation with the electron beam, and calculates the length of the trajectory.

The three-dimensional modeling device 1 calculates the scanning speed of the electron beam (step S13). If the frame rate of the video m is c [frames/sec], the shutter interval of the camera 7 is 1/c [sec]. Assuming that the timing of the camera 7 captures images simultaneously with the start and end of electron beam irradiation, the scanning time t can be expressed by the following equation (1) using the number of frames F [frames].

However, the timing of camera 7's image capture and at least one of the start and stop of electron beam irradiation are not necessarily synchronized. As a result, at least one of the start and stop of irradiation may miss up to 1/c [sec] of an image capture. Therefore, the actual scanning time t [sec] satisfies the range of the following equation (2).

Here, if the scanning speed is v and the scanning length is L [mm], the scanning speed v is calculated by scanning length L/scanning time t. From equations (1) and (2), the scanning speed v satisfies the range of the following equation (3).

Therefore, the measured value of the velocity expressed by the following equation (4) is defined as v _m [mm/sec] by averaging the upper and lower limit values that can be considered from the measurement results.

The three-dimensional modeling apparatus 1 obtains the scanning speed v _m as the measurement result of the parameter using Equation (4). The above-described steps S11 to S13 can be considered as a second preparation step for obtaining the measurement result of the parameter that defines the heat input by analyzing the moving image m.

As a third preparation step, the 3D modeling apparatus 1 evaluates the scanning speed v _m (step S14). The comparison unit 47 evaluates the scanning speed v _m by determining whether the measured scanning speed v _m is within the allowable range of 940 to 980 mm/sec.

When the scanning speed _vm is within the allowable range, it can be said that the amount of heat actually input to the powder material P is appropriate. Therefore, it can be said that the heat input to the powder material P is appropriate in the modeling operation performed immediately before or after measuring this scanning speed _vm . If the amount of heat input is appropriate, it can be said that the quality of the model evaluated based on the amount of heat input meets the standard.

In the modeling process, the three-dimensional modeling device 1 spreads powder material P evenly on the plate 51 and irradiates the spread powder material P with an electron beam to form a model PA (step S15).

The three-dimensional modeling method includes a first preparatory step of irradiating the plate 51 with an electron beam in accordance with a heat input setting indicating the allowable range of a parameter that determines the amount of heat input imparted to the powder material P by the electron beam and a beam irradiation setting including trajectory information that determines the irradiation position of the electron beam, and capturing an image of the plate 51 to obtain a video m that includes the irradiation point of the electron beam; a second preparatory step of analyzing the video m to obtain measurement results of the parameter that determines the amount of heat input; a third preparatory step of determining whether the measurement results are within the allowable range; and a modeling step of spreading the powder material P evenly on the plate 51 and irradiating the spread powder material P with the electron beam to form a model PA.

This three-dimensional printing method captures a video m of points irradiated with an electron beam in accordance with beam irradiation settings, which include information defining the allowable range of parameters defining the amount of heat input and information defining the movement of the beam. The three-dimensional printing method analyzes the video m to obtain parameter measurement results. The three-dimensional printing method determines whether the measurement results are within the allowable range. In this case, it is determined whether the actual parameter measurement results are within the allowable range of the parameter. If the measurement results are within the allowable range, it is determined that the range of heat input to the object PA is within the allowable range. This makes it possible to ensure that the object PA has the desired printing quality.

The second preparation process counts the number of frames F in which the electron beam is continuously captured by determining whether each frame of the video m contains an electron beam irradiation point, and obtains the speed at which the electron beam irradiation point moves along the trajectory as a measurement result based on the number of frames F in which the electron beam is captured, the length of the electron beam trajectory, and the frame rate of the video m. In this case, the actual speed at which the electron beam is irradiated is obtained as the measurement result. This makes it possible to more precisely ensure that the heat input, which is determined by the speed, is within an allowable range. Therefore, it becomes possible to ensure that the model PA has the desired modeling quality.

The first preparation step involves irradiating the electron beam so that its trajectory is circular. In this case, even in a small area on the plate 51, the distance irradiated by the electron beam is long, making it possible to more accurately determine the irradiation trajectory. As a result, measurement results can be made more accurate.

The first preparation step involves irradiating the electron beam so that the speed at which the electron beam moves along the trajectory is constant. In this case, during irradiation of the electron beam, the electron beam appears in the frame of video m at a constant speed. As a result, more accurate measurement results can be obtained.

Additive manufacturing is a relatively new manufacturing technology. The object PA obtained by additive manufacturing not only has the desired shape, but also requires mechanical properties such as strength. However, a method for evaluating whether an object PA manufactured by additive manufacturing has the desired quality has not yet been established. Heat input is one parameter that affects the quality of the object PA. If the heat input is too high or too low, defects will occur inside the object PA. Therefore, if it is possible to confirm that the heat input is properly managed, it can at least be proven that there are no defects caused by inadequate heat input. Therefore, the inventors conducted extensive research into a method that can measure the heat input of an object PA with enough precision to be applicable to quality control, and as a result, they came up with the three-dimensional printing method and three-dimensional printing device 1 disclosed herein.

The three-dimensional printing apparatus 1 includes a beam source 3c that irradiates an electron beam onto a plate 51 in accordance with a heat input setting indicating the allowable range of a parameter that determines the amount of heat input imparted to a powder material P by the electron beam and a beam irradiation setting including trajectory information that determines the irradiation position of the electron beam; a camera 7 that photographs the plate 51 and outputs a video m that includes the electron beam irradiation point; and a control unit 4 that analyzes the video m to obtain measurement results of the parameter that determines the amount of heat input and determines whether the measurement results are within the allowable range. The beam source 3c spreads the powder material P evenly on the plate 51, and irradiates the spread powder material P with an electron beam to form a model PA. For the reasons described above, this three-dimensional printing apparatus 1 can ensure that the model PA has the desired printing quality.

The control unit 4 has a counting unit 44 that counts the number of frames F in which the electron beam is continuously captured by determining whether or not the electron beam irradiation point is included in each frame of the moving image m, and a speed calculation unit 46 that acquires the speed at which the electron beam irradiation point moves along the trajectory as a measurement result based on the number of frames F in which the electron beam is captured, the length of the electron beam trajectory, and the frame rate of the moving image m. Even in this case, for the reasons described above, it is possible to ensure that the object PA has the desired molding quality.

The control unit 4 controls the irradiation of the electron beam by the beam source 3c so that the electron beam trajectory is circular. Even in this case, the measurement results can be made more accurate for the reasons described above.

The control unit 4 controls the irradiation of the electron beam by the beam source 3c so that the speed at which the electron beam moves along the trajectory is constant. Even in this case, the measurement results can be made more accurate for the reasons described above.

The three-dimensional printing method and three-dimensional printing device disclosed herein are not limited to the above-described embodiments, and various modifications are possible without departing from the spirit and scope of the present disclosure.

In the embodiment, an example has been described in which the scanning speed is obtained as the measurement result, but the measurement result may also be the scanning length, the output of the electron beam, etc. In addition, in the three-dimensional printing method, the processing of step S15 may be performed before step S10. Even in these cases, if the measurement result is within the allowable range, it can be determined that the range of the heat input to the molded object PA is within the allowable range. This makes it possible to ensure that the molded object PA has the desired printing quality.

The three-dimensional modeling method may obtain a first measurement result through steps S10 to S14, and then, after step S15, perform steps S10 to S14 to obtain a second measurement result. In this case, if the first and second measurement results are within a predetermined range, it can be determined that the parameter measurement results are stable in the modeling process (step S15).

The camera 7 may output an image of the plate 51 to the control unit 4 separately from the video m. For example, the camera 7 may output an image of the plate 51 after the electron beam irradiation has stopped to the control unit 4 in order to calculate the scanning length. The camera 7 may be provided inside the three-dimensional printing device 1. The plate 51 may be rotating during parameter measurement, or powder material P may be placed on the plate 51. Even in these cases, it is possible to ensure that the molded object PA has the desired molding quality for the reasons described above.

REFERENCE SIGNS LIST 1 Three-dimensional modeling apparatus 2 Drive unit 3 Processing unit 3a Feeder 3b Heater 3c Beam source 4 Control unit 5 Housing 6 Window unit 7 Camera 21 Rotation drive mechanism 22 Elevation drive mechanism 41 Memory unit 42 Beam control unit 43 Acquisition unit 44 Counting unit 45 Distance calculation unit 46 Speed calculation unit 47 Comparison unit 51 Plate 51a Plate main surface 52 Modeling tank 101 Processor 102 Memory 103 Storage 104 Communication device 105 Input device 106 Output device 107 Bus φ Control signal m Video P Powder material PA Model S Modeling space

Claims (8)

a first preparation step of irradiating the energy beam onto a plate in accordance with a heat input setting indicating an allowable range of a parameter that defines the heat input amount imparted to the powder material by the energy beam and a beam irradiation setting including trajectory information that defines a trajectory where a start point and an end point of the irradiation position of the energy beam overlap, and capturing an image of the plate to obtain a video including the irradiation point of the energy beam;
a second preparation step of acquiring measurement results of parameters that define the heat input amount by analyzing the video;
a third preparation step of determining whether the measurement result is within the allowable range;
a manufacturing process of manufacturing a three-dimensional object by irradiating the energy beam onto the powder material while spreading the powder material evenly on the plate;
A three-dimensional modeling method comprising: The second preparation step includes:
Counting the number of frames in which the energy beam is continuously projected by determining whether or not the energy beam irradiation point is included in each frame of the video;
The three-dimensional printing method according to claim 1, wherein the speed at which the irradiation point of the energy beam moves along the trajectory is obtained as the measurement result based on the number of frames over which the irradiation point of the energy beam moves, the length of the trajectory of the energy beam, and the frame rate of the video. The three-dimensional printing method according to claim 1 or 2, wherein the first preparation step irradiates the energy beam so that the trajectory of the energy beam is circular. The three-dimensional printing method according to any one of claims 1 to 3, wherein the first preparation step irradiates the energy beam so that the speed at which the energy beam moves along the trajectory is constant. an irradiation unit that irradiates the energy beam onto a plate in accordance with a beam irradiation setting including a heat input setting indicating an allowable range of a parameter that defines a heat input amount imparted to the powder material by the energy beam and trajectory information that defines a trajectory where a start point and an end point of the irradiation position of the energy beam overlap;
an imaging unit that captures an image of the plate and outputs a video including the irradiation point of the energy beam;
a control unit that analyzes the video to obtain a measurement result of a parameter that defines the heat input amount, and determines whether the measurement result is within the allowable range;
The irradiation unit spreads a powder material evenly on the plate and irradiates the energy beam onto the powder material, thereby forming a three-dimensional object. The control unit
a counting unit that counts the number of frames in which the energy beam is continuously projected by determining whether or not the energy beam irradiation point is included in each frame of the moving image;
a velocity calculation unit that acquires, as the measurement result, a velocity at which the irradiation point of the energy beam moves along the trajectory based on the number of frames in which the energy beam is captured, the length of the trajectory of the energy beam, and the frame rate of the video.
The three-dimensional modeling apparatus according to claim 5 . The three-dimensional printing device according to claim 5 or 6, wherein the control unit controls the irradiation of the energy beam by the irradiation unit so that the trajectory of the energy beam is circular. 8. The three-dimensional modeling apparatus according to claim 5, wherein the control unit controls the irradiation of the energy beam by the irradiation unit so that the speed at which the energy beam moves along the trajectory is constant.