Device for additive manufacturing

Abstract

An additive manufacturing device comprises a material supply unit that supplies material to an area in which a layer is to be formed on a workpiece, a heat source supply unit that supplies the workpiece with a heat source for melting the material, a temperature measuring unit that measures the temperature of a temperature measuring area that encompasses the entire area in which the object is to be formed, a temperature setting unit that performs the temperature setting by heating or cooling the object, and a control unit that derives a temperature gradient in the object based on temperature distribution information over the temperature measuring area and a solidification rate and a cooling rate in the object based on the temperature distribution information at different times, and determines manufacturing conditions for the formation of a layer to be subsequently formed.so that the derived temperature gradient, derived solidification rate, and derived cooling rate correspond to the temperature gradient, solidification rate, and cooling rate for the formation of a desired structure. The control unit then controls the components based on the manufacturing conditions to perform a manufacturing process.

Description

Area

[0001] The present disclosure relates to an additive manufacturing device for producing an additively manufactured object by depositing an object formed by melting and solidifying a metal material on a workpiece. background

[0002] Additive manufacturing techniques are well-known as a method for producing 3D objects, such as components. Among additive manufacturing processes, direct energy deposition (DED) has the advantage that the time required to produce an object is shorter and the amount of material consumed is lower than with other methods.

[0003] In the aforementioned technical field, patent document 1 discloses a method for deriving the temperature and a temperature gradient of a melt and in a melt based on the intensity of image data of the melt taken by an infrared camera. List of citations from patent literature

[0004] Patent document 1: Japanese patent no. 6228314 Brief description of the invention Problem to be solved by the invention

[0005] As is well known, in additive manufacturing, the internal structure of a manufactured object is not uniform because the heat stored in the object changes from the initial to the final stage of production. For a uniform improvement in the properties of the entire object, it is necessary to give the entire object a desired structure, i.e., to make it homogeneous. However, the technique described in Patent Document 1 only derives the temperature distribution and temperature gradient of the melt from the intensity of the image data. Furthermore, Patent Document 1 does not consider homogenization of the entire object, and it is unclear how the derived temperature distribution and temperature gradient of the melt are to be used. Therefore, a technique that enables structural homogenization of the entire object is desirable.

[0006] The present disclosure arose in consideration of the above considerations, one of its objectives being to provide an additive manufacturing device that enables an unprecedented homogenization of the entire structure of an object. Means of solving the problem

[0007] To solve the problem described above and to fulfill the objective, the present disclosure relates to an additive manufacturing device in which an object is formed by applying a layer, namely a layer of molten metal, to a substrate that serves as the base on which the object is to be formed. The device comprises a material feed unit, a heat source feed unit, a temperature measuring unit, a temperature setting unit, and a control unit. The material feed unit supplies a workpiece on which a layer is to be formed with material in the form of wire or powder for layer formation. The heat source feed unit supplies the workpiece with a heat source for melting the material. The temperature measuring unit measures the temperature within a temperature measuring range that encompasses the entire area in which the object is to be formed.The temperature setting unit adjusts the temperature by heating or cooling the object. The control unit controls the material feed unit, the heat source supply unit, and the temperature setting unit. The control unit derives the temperature gradient within the object based on temperature distribution information, which consists of the results of temperature measurements within the temperature measurement range. It also derives the solidification and cooling rates within the object based on this temperature distribution information at different times. Furthermore, the control unit sets the manufacturing conditions for the formation of a subsequent layer such that the derived temperature gradient, solidification rate, and cooling rate correspond to those required for the formation of a desired structure.The control unit then controls the material feed unit, the heat source feed unit and the temperature setting unit according to the manufacturing conditions in order to carry out the manufacturing process. Effects of the invention

[0008] The device for additive manufacturing according to the present disclosure has the advantage that it can make the entire structure of an object more homogeneous than ever before. Brief description of the characters Fig. Figure 1 shows a schematic representation illustrating an example of the configuration of an additive manufacturing device according to a first embodiment. Fig. Figure 2 shows a representation to explain a method for deriving a temperature gradient and a solidification rate from temperature distribution information. Fig. Figure 3 shows a representation to explain a method for deriving a temperature gradient in the vertical direction from temperature distribution information. Fig. Figure 4 shows a schematic representation illustrating an example of the relationship between the crystal shape of the solidified metal structure and the combination of temperature gradient and solidification rate. Fig. Figure 5 shows a representation to explain a method for deriving a cooling rate from temperature distribution information. Fig. Figure 6 shows a representation to explain a method for deriving a cooling rate in the vertical direction from temperature distribution information. Fig. Figure 7 shows a diagram illustrating an example of a method for reducing the temperature gradient in the vertical direction. Fig. Figure 8 shows a block diagram to illustrate an example of the hardware configuration of a control device included in an additive manufacturing device according to the first embodiment. Fig. Figure 9 shows a flowchart to illustrate an example of the process flow of an additive manufacturing process according to the first embodiment. Fig. Figure 10 shows a flowchart to illustrate an example of the process flow of an additive manufacturing process according to a second embodiment. Fig. Figure 11 shows a flowchart to illustrate an example of the process flow of an additive manufacturing process according to a third embodiment. Description of embodiments

[0009] A device for additive manufacturing according to embodiments of the present disclosure is described in detail below with reference to the figures. First embodiment

[0010] Fig. Figure 1 shows a schematic representation illustrating an example of the configuration of an additive manufacturing device according to a first embodiment. An additive manufacturing device 1 is a device for forming an object 112 by melting a metal material and building up layers of the molten metal on a substrate 111. Specifically, the additive manufacturing device 1 melts a wire W, which is the metal material, together with a portion of a workpiece that serves as a base, to form a melt 115 and creates a layer, called a bead, which is formed by solidifying the melt 115 on the workpiece. In this way, a layer of the metal material is deposited on the workpiece and thus formed on the surface of the workpiece. By applying layers in a desired shape, a desired additively manufactured 3D object can be obtained.In the following, the workpiece serves as a substrate for the formation of a layer, i.e., the workpiece is an object on which a layer is formed, and refers to the substrate 111 or a layer.

[0011] Of the layers, the layer formed on the substrate 111 is called the initial layer 113, and the uppermost layer being formed is called the final layer 114. For example, if the second layer is currently being formed, the second layer is the final layer 114. If the third layer is currently being formed, the third layer is the final layer 114. The object 112 is composed of the layers formed on the substrate 111. Thus, the object 112 consists of the layers from the initial layer 113 to the final layer 114. The object 112 grows during the manufacturing process and ultimately becomes an additively manufactured 3D object with a desired shape. In the first embodiment, the heat source is a laser beam L, and the material is, for example, a metal wire W. The heat source is not limited to a laser beam L and can also be an electric arc or an electron beam.The material is not limited to a metal wire W and can also be a metal powder. In . Fig. 1. The vertical direction is defined as the Z-axis direction, and two directions that are perpendicular to each other in a plane perpendicular to the Z-axis direction are defined as the X-axis direction and the Y-axis direction.

[0012] The additive manufacturing device 1 comprises a table 11, an irradiation device 12, a gas ejection device 13, a wire feeder 14, a head drive unit 15, a laser oscillator 16, a temperature measuring device 17, a temperature setting device 18 and a control device 19. Fig. 1. Dashed lines indicate signal lines.

[0013] The substrate 111, which serves as a base for the formation of object 112, is placed on table 11. In the Fig. In the example shown, substrate 111 is a sheet material, but it can also be a material other than a sheet material.

[0014] The irradiation device 12 is an example of a heat source irradiation unit that irradiates the workpiece with the laser beam L, i.e., the heat source for melting the material. During irradiation with the laser beam L, the workpiece melts, forming the melt 115. Subsequently, the melt 115 solidifies during the cooling process, forming a layer.

[0015] The gas ejection device 13 ejects a shielding gas G in the direction of the processing point, i.e., the irradiation position of the laser beam L. An example of the shielding gas G is an inert gas such as nitrogen or argon. The ejection of the shielding gas G prevents oxidation of the workpiece at the processing point and cools the workpiece. In the example of Fig. In the example of 1, the gas ejection device 13 is attached to the outer circumferential surface of the irradiation device 12 and ejects the shielding gas G along the central axis of the laser beam L emitted by the irradiation device 12. The irradiation device 12 and the gas ejection device 13 are therefore arranged coaxially. Fig. In Figure 1, the irradiation device 12 and the gas ejection device 13 are formed as a single unit and constitute a processing head. However, it is only necessary that the gas ejection device 13 be configured such that the shielding gas G is ejected in the direction of an area encompassing the processing point irradiated by the laser beam L, in order to prevent oxidation of the material that melts and solidifies at the processing point. Therefore, the gas ejection device 13 can eject the shielding gas G in the direction of the processing point at an angle to the Z-axis. That is, the gas ejection device 13 does not have to be formed as a single unit with the irradiation device 12, but can be configured to eject the shielding gas G at an angle to the central axis of the laser beam L emitted by the irradiation device 12.The gas ejection device 13 is an example of a temperature control unit that performs a temperature adjustment by heating or cooling the object 112, and corresponds to a second temperature control unit.

[0016] The wire feeder 14 is a device that feeds the wire W to the processing point on the workpiece where a layer is to be formed. In one example, the wire feeder 14 comprises a wire spool around which the wire W is wound, a rotary motor that rotates the wire spool about a rotary axis, and a wire nozzle, with the wire W being guided from the wire spool to the processing point on the workpiece. The wire feeder 14 is an example of a material feeder unit that supplies the material, in the form of a wire W or a powder, to a workpiece on which a layer is to be formed, in an area where the layer is to be formed.

[0017] The head drive unit 15 moves the irradiation device 12 in the direction of the X-axis, the Y-axis, and the Z-axis, respectively. The head drive unit 15 comprises a servo motor that forms a drive mechanism for moving the irradiation device 12 in the X-axis direction, a servo motor that forms a drive mechanism for moving the irradiation device 12 in the Y-axis direction, and a servo motor that forms a drive mechanism for moving the irradiation device 12 in the Z-axis direction. The head drive unit 15 is a drive mechanism that enables translational movement in each of the three axis directions. Fig. In Figure 1, the illustration of the servo motors was omitted. The additive manufacturing device 1 can shift the irradiation position of the laser beam L on the workpiece by moving the irradiation device 12 with the head drive unit 15. The head drive unit 15 is not limited to movement in the three perpendicular axis directions. A multi-axis drive unit, e.g., a robot arm, can also be used. In the example of Fig. 1 The head drive unit 15 is a device that drives the processing head, since the irradiation device 12 and the gas emission device 13 integrally form the processing head.

[0018] In the Fig. In the example shown, the irradiation device 12 emits the laser beam L in the Z-axis direction. The wire feeder 14 is located in the XY plane away from the irradiation device 12 and feeds the wire W to the processing point from a direction that forms an angle with the Z-axis. It should be noted that the wire nozzle (not shown) of the wire feeder 14 can be attached to the irradiation device 12. The wire nozzle can be attached to the irradiation device 12 such that the feed direction of the wire W is the Z-axis direction.

[0019] The laser oscillator 16 is a beam source that emits the laser beam L, such as a solid-state laser, a gas laser, a fiber laser, or a semiconductor laser. The laser oscillator 16 is connected to the irradiation device 12 via a fiber optic cable. The fiber optic cable is an optical transmission line that carries the laser beam L from the laser oscillator 16 to the irradiation device 12. The laser oscillator 16 and the irradiation device 12 form an irradiation unit that irradiates the workpiece with the laser beam L to melt the wire W. The laser oscillator 16 is an example of a heat source generation unit that generates the heat source for melting the material. The irradiation device 12, the head drive unit 15, and the laser oscillator 16 form a heat source supply unit that supplies the workpiece with the heat source for melting the material.

[0020] The temperature measuring device 17 measures the temperature within a temperature measuring range, i.e., a range encompassing the entire area in which the object 112 is formed. When the object 112 is formed on the substrate 111, the temperature measuring range includes not only the entire area in which the object 112 is to be formed, but also the area encompassing the substrate 111. In this case, the temperature measuring device 17 measures the temperature distribution across the entire processing area on the substrate 111, i.e., the temperature distribution of temperatures at positions within a range that includes at least the entire substrate 111, and outputs the measured temperature distribution as temperature distribution information to the control device 19. The temperature measuring device 17 measures the temperature distribution of the entire object 112 during the formation of the individual layers.The temperature measuring device 17 therefore measures the temperature distribution in the entire object 112 from the initial layer 113 to the final layer 114 that is formed.

[0021] A commercially available infrared camera can be used as the temperature measuring device 17. However, if the temperature of object 112 is measured using an infrared camera, the emissivity must be adjusted. The emissivity varies depending on the material and surface properties of object 112. If a suitable emissivity has not been set according to the material and surface properties of object 112, the control device 19 will therefore obtain values ​​from the temperature measuring device 17 as the temperature of object 112 that deviate from the actual temperature and will perform the control operation based on this discrepancy. In this case, the problem arises that object 112 cannot be obtained with the desired structure.

[0022] In the first embodiment, the temperature measuring device 17 is therefore preferably a two-color thermographic camera that measures the temperature of the temperature measurement area based on the intensity ratio of infrared or visible radiation of two different wavelengths emitted by an object to be measured. A two-color thermographic camera is a radiation thermometer that uses a two-dimensional temperature distribution and determines the surface temperature of an object within the field of view by measuring the object's thermal radiation. As described above, the two-color thermographic camera specifically calculates the radiation intensity ratio from the intensities, i.e., the light intensities of each pixel in an image of the temperature measurement area in the two wavelength bands, and calculates the temperature at each pixel from the radiation intensity ratio.The temperatures at the pixels represent temperature distribution information. Each pixel in the temperature measurement area corresponds to a specific position within that area. This results in temperature distribution information from which the temperature at each pixel in the temperature measurement area image can be derived. By using the results of the temperature measurement area with the two-color thermographic camera, the need to adjust the emissivity, which is required for temperature measurement with a conventional infrared camera, is eliminated. Since the emissivity varies depending on the material and surface properties of object 112, the temperature of object 112 can thus be measured more accurately compared to using an infrared camera without adjusting the emissivity.

[0023] In one example, the temperature measuring device 17 is positioned obliquely next to the irradiation device 12, or it is located at a position where the entire formation area can be measured. If the temperature measuring device 17 is positioned obliquely next to the irradiation device 12, i.e., at an angle to a vertical line, it can measure the temperature not only of the top surface but also of the side surfaces of the object 112 with its vertically stacked layers. That is, the temperature measuring device 17 is positioned so that it can measure the temperature not only of the top but also of the side surfaces of the object 112 within the temperature measurement range that encompasses the entire area in which the object 112 is formed. By relating the temperature distribution measured by the temperature measuring device 17 within the object 112, the temperature of the forming object 112 can be monitored in real time.Furthermore, by using the temperature distribution measured by the temperature measuring device 17, not only the temperature in a forming layer, but also the temperature in one or more previously formed layers can be determined. The temperature measuring device 17 corresponds to a temperature measuring unit.

[0024] The temperature control device 18 heats or cools the substrate 111 so that the temperature of the substrate 111 is maintained at a temperature set by the control device 19. Examples of the temperature control device 18 are a heating device that uses a high-frequency induction heater, a heating device that uses an electric heating wire, such as a hot plate, a cooling device that uses a water-cooled heat sink, a cooling device that uses a thermoelectric cooling element, such as a Peltier module, or the like. Alternatively, the temperature control device 18 can also be a combination of one of the heating devices and one of the cooling devices. In the example of Fig. In the table 11, the temperature control device 18 is mounted such that it heats or cools the substrate 111 from the underside of the substrate 111. The temperature control device 18 is an example of a temperature control unit that performs a temperature adjustment by heating or cooling the object 112 and corresponds to a first temperature control unit.

[0025] The control device 19 controls the additive manufacturing device 1, in particular the irradiation device 12, the gas ejection device 13, the wire feeder 14, the head drive unit 15, the laser oscillator 16, and the temperature control device 18, according to a machining program. In one example, the control device 19 is a numerical control device. The control device 19 corresponds to a control unit. The control device 19 issues a movement command to the head drive unit 15 to control the drive of the head drive unit 15. After the movement command is entered, the head drive unit 15 moves the irradiation device 12 according to the movement command.

[0026] The control device 19 issues a command according to a condition for beam output, i.e. the output of the laser beam L, to the laser oscillator 16 in order to control the laser oscillation of the laser oscillator 16.

[0027] The control device 19 issues a command to the wire feeder 14 according to a material feed condition in order to control the wire feeder 14. The control device 19 controls the drive of the wire feeder 14, more precisely the drive of the rotary motor, to set the feed rate of the wire W in the direction of the irradiation position. The feed rate indicates the amount of material fed per unit of time.

[0028] The control device 19 issues a command to the gas ejection device 13 according to a condition for the supply quantity of the protective gas G, in order to control the supply quantity of the protective gas G ejected by the gas ejection device 13.

[0029] Based on the temperature distribution information obtained from the temperature measuring device 17, the control device 19 adjusts the manufacturing conditions, which include the movement command to the head drive unit 15, the beam output condition, the material feed quantity condition, the shielding gas supply quantity condition, and the temperature condition for the temperature setting device 18, so that the entire structure of the object 112 becomes homogeneous. The control device 19 issues commands to the gas ejection device 13, the wire feeder 14, the head drive unit 15, the laser oscillator 16, and the temperature setting device 18 to fulfill the set manufacturing conditions. The control device 19 issues various commands to control the entire additive manufacturing device 1.

[0030] The adjustment of the manufacturing conditions by the control device 19 is now described, based on the temperature distribution information measured by the temperature measuring device 17. The control device 19 derives a temperature gradient, a solidification rate, and a cooling rate based on the temperature distribution information of the temperature measuring range obtained from the temperature measuring device 17. Specifically, the control device 19 derives the temperature gradient based on the temperature distribution information across the temperature measuring range at a specific time, and derives the solidification rate and the cooling rate based on the temperature distribution information across the temperature measuring range at different times. In doing so, a temperature gradient, a solidification rate, and a cooling rate are derived in the object 112.Every temperature gradient has a value obtained by dividing the temperature difference between any two positions by the distance between the two positions. Regarding temperature gradients, not only are temperature gradients derived between positions in the horizontal direction, but also temperature gradients between positions in the vertical direction. In one example, a temperature gradient between positions in the horizontal direction is derived using the upper surface of the final layer 114 in the temperature distribution information. In another example, a temperature gradient between positions in the vertical direction is derived using the side surface of object 112 in the temperature distribution information. The solidification rate is the speed at which a solid-liquid interface, i.e., the interface between the melt 115 and object 112, moves.The cooling rate is the temperature difference per unit of time, i.e., the amount of temperature change per unit of time at any fixed position in the cooling process.

[0031] Fig. Figure 2 shows a representation to explain a method for deriving a temperature gradient and a solidification rate from temperature distribution information. Fig. Figure 2 shows a schematic manufacturing diagram 31A, which schematically illustrates a state in which the object 112 is formed on the substrate 111, and a temperature distribution diagram 31B, which shows the distribution of temperatures at positions of the final layer 114 shown in the schematic manufacturing diagram 31A.

[0032] Schematic manufacturing diagram 31A shows a state in which the initial layer 113, a layer 114b formed two layers before the final layer 114, and a layer 114a formed one layer before the final layer 114 are stacked on top of each other on the substrate 111, with the final layer 114 being formed on top of layer 114a. In schematic manufacturing diagram 31A, the layers from the initial layer 113 to the final layer 114 form the object 112. The laser beam L (not shown) is directed towards the position of the melt 115, where a portion of the underlying layer 114a and the wire W (not shown) are melted. In this example, the laser beam L is emitted from right to left in the figure. In this example, the final layer 114 is formed by the solidification of the melt 115. The interface between the melt 115 and the final layer 114 in solid form is a solid-liquid interface 116.The speed at which the solid-liquid interface 116 moves per unit of time is the solidification rate.

[0033] In temperature distribution diagram 31B, the horizontal axis represents the position within the temperature measurement range, in this example the horizontal position in the final layer 114, while the vertical axis represents the temperature. Temperature distribution diagram 31B therefore shows the temperatures at positions where the final layer 114 is formed. In the schematic manufacturing diagram 31A, the laser beam L is scanned from right to left; that is, the further to the right, the earlier the melting point. The temperature thus decreases from the position of the melt 115 to the right along the horizontal axis. Although not shown, the left side of the melt 115 is not yet heated and therefore has a lower temperature.

[0034] The control device 19 derives a temperature gradient from the distance and temperature difference between arbitrary horizontal positions a1 and a2 in the final layer 114, based on the referenced temperature distribution information. The temperature gradient can be determined by dividing the calculated temperature difference by the calculated distance. By first obtaining the relationship between distance units in the temperature distribution information and an actual distance on the workpiece within the temperature measurement range, the distance between the arbitrary positions a1 and a2 in the temperature distribution information can be converted into an actual distance on the substrate 111 or the workpiece.

[0035] The control device 19 obtains the melting point of the wire W in advance. Therefore, from the melting point of the wire W and the temperature distribution information, the control device 19 determines the position of the solid-liquid interface 116 between the melt 115 and the object 112. From the positions of the solid-liquid interface 116, obtained from several portions of the temperature distribution information at different times, the control device 19 derives the solidification rate, i.e., the rate of movement of the solid-liquid interface 116. For example, the solidification rate is derived by dividing the magnitude of the change in the position of the solid-liquid interface 116 between two times by the difference between those two times. Therefore, the coordinate position at any given time can be determined from the temperature distribution information obtained by the temperature measuring device 17.By setting the specific temperature to the melting point of the wire W, position information about the solid-liquid interface 116 can be recorded at any time, so that the movement speed of the solid-liquid interface 116, i.e. the solidification rate, can be recorded.

[0036] Fig. Figure 3 shows a representation to explain a method for deriving a temperature gradient in the vertical direction from temperature distribution information. Fig. Figure 3 shows a schematic manufacturing diagram 31A, which schematically represents a state in which the object 112 is formed on the substrate 111, and a temperature distribution diagram 31C, which shows the temperature distribution in the vertical direction at position a1 in the final layer 114 shown in the schematic manufacturing diagram 31A. The same components as in Fig. 2 are labelled with the same reference symbols, but their descriptions are omitted.

[0037] The first embodiment aims not only to homogenize the structure of object 112 in the same layer, but also the structure of a larger area, including that in the vertical direction, i.e., the vertical direction from the initial layer 113 to the final layer 114. Therefore, not only a temperature gradient in the direction of the plane, but also a temperature gradient in the vertical direction is referenced in the temperature measurement area.

[0038] In temperature distribution diagram 31C, the horizontal axis represents the position of a specific point in the temperature measurement area in the vertical direction, and the vertical axis represents the temperature. In the schematic manufacturing diagram 31A, the layers are formed sequentially from the initial layer 113 to the final layer 114; that is, the lower the layer, the earlier the melting point. Therefore, the temperature decreases downwards from position a1 of the melt 115 along the horizontal axis.

[0039] The control device 19 derives a temperature gradient from the distance and temperature difference between any positions a1 and a3 in the vertical direction, based on the related temperature distribution information. The temperature gradient can be obtained by dividing the calculated temperature difference by the calculated distance.

[0040] Fig. Figure 4 shows a schematic representation illustrating an example of the relationship between the crystal shape of a solidified metal structure and the combination of the temperature gradient and the solidification rate. Fig. Figure 4 shows the horizontal axis as the solidification rate of the metal and the vertical axis as the temperature gradient of the metal. The crystal form of the metal structure is generally determined by the relationship between the temperature gradient and the solidification rate at the solid-liquid interface 116. If the crystal form of the structure is a columnar structure, the mechanical properties of the metal exhibit anisotropy. If the crystal form of the structure is an equiaxial structure, the mechanical properties of the metal do not exhibit anisotropy. By controlling the temperature gradient and the solidification rate at the solid-liquid interface 116, the crystal form of the structure of object 112 can therefore be controlled, thereby controlling the mechanical properties of object 112.

[0041] Fig. Figure 5 shows a representation to explain a method for deriving a cooling rate from temperature distribution information. Fig. Figure 5 shows a schematic manufacturing diagram 32A, which schematically represents a state in which the object 112 is formed on the substrate 111, and a diagram of the temperature change over time 32B, which shows the changes in temperature over time at any fixed position A in the final layer 114 shown in the schematic manufacturing diagram 32A. The same components as in the schematic manufacturing diagram 31A of Fig. 2 are provided with the same reference symbols, and their description is omitted.

[0042] In the schematic manufacturing diagram 32A, the laser beam L (not shown) is emitted onto the position of the melt 115, melting layer 114a, which serves as a base for the final layer 114, and the wire W. In this example, the laser beam L is emitted from right to left in the figure. The object 112 is formed by the solidification of the melt 115.

[0043] In the time-dependent temperature change diagram 32B, the horizontal axis represents elapsed time and the vertical axis represents temperature. When the wire W is moved to position A and irradiated with the laser beam L, the substrate layer 114a and the wire W melt at the irradiation position, forming the melt 115. Because the laser beam is scanned from right to left in the schematic manufacturing diagram 32A, the temperature at position A, which was previously low, rises and then falls again. The time-dependent temperature change diagram 32B illustrates how the temperature at position A decreases after irradiation with the laser beam L. In an example, the time-dependent temperature change diagram 32B is created by extracting the temperature at position A from the stored temperature distribution information at each time point.

[0044] From the elapsed time and the temperature profile at any fixed position A, the control device 19 derives the cooling rate, i.e., the control device 19 calculates the temperature difference per unit of time from the graph of the temporal temperature change 32B.

[0045] Fig. Figure 6 shows a representation to explain a method for deriving a cooling rate in the vertical direction from temperature distribution information. Fig. Figure 6 shows a schematic manufacturing diagram 32A, which schematically represents a state in which the object 112 is formed on the substrate 111, and a diagram of the temperature change over time 32C, which shows the changes in temperature over time at any fixed position B in the object 112 shown in the schematic manufacturing diagram 32A. Fig. In section 6, position B is located in layer 114b and not in the final layer 114. The same components as in the schematic manufacturing diagram 31A of Fig. 2 are labelled with the same reference symbols, and their descriptions are omitted.

[0046] In the temperature change over time diagram 32C, elapsed time is represented on the horizontal axis and temperature on the vertical axis. In the schematic manufacturing diagram 32A, the temperature at position B is highest when layer 114b is formed, and the temperature subsequently decreases as layer 114a and the final layer 114 are successively formed on top of layer 114b. The temperature change over time diagram 32C shows how the temperature at position B decreases during the manufacturing process. As an example, the temperature change over time diagram 32C is created by extracting the temperature at position B from the stored temperature distribution information at each point in time.

[0047] The control device 19 derives the cooling rate from the elapsed time and the temperature profile at the arbitrary fixed position B. The control device 19 therefore calculates the temperature difference per unit of time from the diagram of the temperature change over time 32C.

[0048] The cooling rate influences the size of the metal microstructure and the type of precipitated phase after solidification. In this description, the size of the structure refers to the size of the crystal grains that comprise it. In this case, a statistical value such as the mean diameter of the main grain can be used as the size of the crystal grains. The type of precipitated phase indicates the type of intermetallic compound that forms upon cooling of the metal, or the type of microstructure that arises from changes in the crystal structure, such as martensite.

[0049] In one example, a high cooling rate results in a finer metal structure, and the hardness and strength at room temperature increase. Furthermore, a high cooling rate in a steel material after melting leads to the formation of martensite, which increases hardness. Therefore, by controlling the cooling rate, the size of the structure and the type of precipitated phases of object 112 can be controlled, thus allowing the mechanical properties of object 112 to be controlled.

[0050] To achieve a desired homogeneous structure in object 112, the control device 19 determines the manufacturing conditions for the production of a subsequent layer such that the derived temperature gradients, solidification rate, and cooling rate correspond to a predetermined temperature gradient, solidification rate, and cooling rate. The control device 19 thus determines the following subsequent manufacturing conditions: the power of the laser beam L, the scanning rate of the laser beam L, the feed rate of the wire W, the flow rate of the protective gas G, the temperature of the substrate 111, and the waiting time before the manufacturing process of the next layer is carried out, based on the derived temperature gradients, solidification rate, and cooling rate.

[0051] The relationships between temperature gradients, solidification rates, cooling rates, and manufacturing conditions vary depending on the type of wire W and other factors, and cannot be uniformly defined. Therefore, the relationships between temperature gradients, solidification rates, cooling rates, and manufacturing conditions are not particularly restrictive and can be determined in advance using any method. For example, manufacturing with a wire W made of a specific material under various manufacturing conditions can be carried out to determine the temperature gradient, solidification rate, and cooling rate under each of these conditions.Alternatively, a temperature gradient, solidification rate, and cooling rate can be determined in advance under any manufacturing conditions using thermal analysis with the finite element method (FEM). Therefore, if the manufacturing conditions—which include the laser beam output power L, the laser beam scanning rate L, the wire feed rate W, the shielding gas flow rate G, the substrate temperature 111, and the time to layer formation—are varied in different ways, the temperature gradients, solidification rates, and cooling rates obtained through an actual manufacturing process or thermal analysis can be stored as manufacturing condition information.The control device 19 then derives the manufacturing conditions under which a desired temperature gradient, solidification rate, and cooling rate are obtained from the manufacturing condition information and carries out the manufacturing process accordingly. Based on the manufacturing conditions, the control device 19 therefore controls the gas ejection device 13, the wire feeder 14, the head drive unit 15, the laser oscillator 16, and the temperature setting device 18 to execute the manufacturing process. As a result, the desired temperature gradient, solidification rate, and cooling rate are obtained during the formation of the subsequent layer.

[0052] During the manufacturing process, the control device 19 derives temperature gradients and the solidification rate from the temperature distribution information on the object 112 and determines whether the obtained temperature gradients and the solidification rate are within specified threshold values. Fig. Figure 7 shows a diagram illustrating an example of a method for reducing the temperature gradient in the vertical direction. Fig. Figure 7 shows a schematic manufacturing diagram 33A, which schematically represents a state in which the object 112 is formed on a substrate 111, which includes a temperature setting device 18, and a temperature distribution diagram 33B, which shows the temperature distribution of position a1 in the final layer 114 in the vertical direction, as shown in the schematic manufacturing diagram 33A. The same components as in Fig. Two components have the same reference symbols, and the description of these components is omitted.

[0053] In temperature distribution diagram 33B, the temperature distribution in the vertical direction at position a1 is represented by curve T1. The control device 19 derives a temperature gradient TG1 in the vertical direction at position a1 from position a1 and the vertically different position a3. If the control device 19 detects that the derived temperature gradient TG1 is greater than the threshold value, it then reduces the power of the laser beam L or increases the temperature of the substrate 111 using the temperature control device 18. If the manufacturing process is carried out on the next layer under this condition, the temperature distribution in the vertical direction at position a1 changes, as shown in temperature distribution diagram 33B by curve T2. The temperature gradient TG2 in the vertical direction at position a1 is therefore smaller than the temperature gradient TG1.In this way, the temperature gradients in the layers are controlled to reduce them.

[0054] If the control device 19 determines that the obtained solidification rate is below the threshold, it alternatively performs a control to increase the solidification rate in the layer by increasing the scanning rate of the laser beam L or the flow rate of the protective gas G.

[0055] The control device 19 derives the cooling rate from the temperature distribution information of the entire object 112 and determines whether the derived cooling rate is within the specified threshold. If the control device 19 determines that the derived cooling rate is below the threshold, it then performs a control action to increase the cooling rate in the layer by reducing the power of the laser beam L, increasing the scanning speed of the laser beam L, or increasing the flow rate of the protective gas G.Since the control device derives temperature gradients, a solidification rate, and a cooling rate at each position within the temperature measurement range encompassing the entire substrate 111 or the entire area in which the object 112 is to be formed, the manufacturing conditions in the manufacturing process are determined at each position in the next layer based on the temperature gradients, solidification rates, and cooling rates described above. The temperature gradients, solidification rates, and cooling rates at each position of the object 112 during the formation of the previous layer are influenced by the heat storage capacity of the object 112. Therefore, the heat storage capacity is taken into account in the manufacturing conditions for the next layer.

[0056] Next, a hardware configuration of the control device 19 is described. The functions of the control device 19 are implemented using hardware by executing a control program, which is a program for controlling the device for additive manufacturing 1.

[0057] Fig. Figure 8 shows a block diagram illustrating an example of the hardware configuration of a control device included in an additive manufacturing device according to the first embodiment. The control device 19 comprises a central processing unit (CPU) 191, which performs various types of processing, a random access memory (RAM) 192, which has a data storage area, a read-only memory (ROM) 193, which is a non-volatile memory, a storage device 194, and an input / output interface 195 for inputting information into the control device 19 and for outputting information from the control device 19. The Fig. The 8 elements shown are connected to each other via bus 196.

[0058] The CPU 191 executes a program stored in the ROM 193 or in the memory device 194. The overall control of the additive manufacturing device 1, which is carried out by the control device 19, is implemented using the CPU 191.

[0059] Storage device 194 is a hard disk drive (HDD) or a solid-state drive (SSD). Storage device 194 stores the control program and various data. ROM 193 stores software or a program for controlling the hardware, such as a bootloader like the Basic Input / Output System (BIOS) or the Unified Extensible Firmware Interface (UEFI), which is a program for the basic control of a computer or controller, i.e., the control device 19. The control program can be stored in ROM 193.

[0060] The programs stored in ROM 193 and in memory device 194 are loaded into RAM 192. The CPU 191 executes the control program in RAM 192 and performs various types of processing. The input / output interface 195 is an interface for connecting to a device outside the control device 19. The processing program is entered into the input / output interface 195. The input / output interface 195 outputs the various commands. The control device 19 can include input devices such as a keyboard and a pointing device, as well as an output device such as a display.

[0061] The control program can be stored on a computer-readable storage medium. The control device 19 can store the control program stored on the storage medium in the storage device 194. The storage medium can be a portable storage medium, such as a floppy disk, or flash memory, i.e., semiconductor memory. The control program can be installed from another computer or server via a communication network onto a computer or controller serving as the control device 19.

[0062] The functions of the control device 19 can be implemented by processing circuits, which are special hardware for controlling the additive manufacturing device 1. The processing circuit is a single circuit, a combined circuit, a programmed processor, a parallel programmed processor, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or a combination thereof. Some of the functions of the control device 19 can be implemented by special hardware, and others by software or firmware.

[0063] The following describes an additive manufacturing process carried out in the additive manufacturing device 1 according to the first embodiment. The additive manufacturing process produces a three-dimensional additively manufactured object. Therefore, the additive manufacturing process described below is also a method for producing an additively manufactured object. Fig. Figure 9 shows a flowchart to illustrate an example of the process flow of an additive manufacturing process according to the first embodiment. Fig. Figure 9 illustrates a process flow of the control device 19 in the device for additive manufacturing 1.

[0064] First, the control device 19 issues commands to the laser oscillator 16 and the head drive unit 15 to achieve a predetermined output power and scanning speed of the laser beam L, and a command to the wire feeder 14 to achieve a predetermined feed rate (step S11). Subsequently, the wire feeder 14 advances the wire W to the workpiece at the predetermined feed rate, and the irradiation device 12 and the head drive unit 15 emit the laser beam L onto the workpiece at the predetermined output power and scanning speed. As a result, a manufacturing process is carried out in which a layer formed by the molten and solidified wire W is deposited onto the workpiece.

[0065] During the manufacturing process, the temperature measuring device 17 measures the temperature distribution within a temperature measuring range that encompasses the entire area in which the object 112 is to be formed. That is, the temperature measuring device 17 measures the temperature distribution throughout the entire object 112 at the time of the formation of each layer, from the initial layer 113 to the final layer 114, including the forming melt 115. The control device 19 receives temperature distribution information from the temperature measuring device 17, which is the result of the temperature distribution measurement within the temperature measuring range (step S12).

[0066] Next, control device 19 determines whether a subsequent production plan exists (step S13). A production plan is information about the manufacturing of the additively manufactured object, which in this example includes the height of object 112. The subsequent production plan is a plan for forming a layer that follows the currently formed layer in the production plan. If, in this example, the height of object 112 formed so far is less than the height in the production plan, there is a subsequent production plan. If the height of object 112 formed so far is equal to the height in the production plan, there is no subsequent production plan.In one example, the control device 19 can determine, by analyzing the machining program for carrying out the manufacturing process, the presence or absence of a subsequent manufacturing plan according to which the manufacturing process will continue on the layer just formed or the manufacturing process will be completed.

[0067] If the control device 19 determines that there is no subsequent manufacturing plan (NO in step S13), i.e., determines that the manufacturing process is completed with the currently formed layer, the control device 19 terminates the additive manufacturing process.

[0068] If the control device 19 determines that there is a subsequent manufacturing plan (YES in step S13), it derives temperature gradients, a solidification rate, and a cooling rate in object 112 based on the temperature distribution information over the temperature measurement range acquired in step S12 (step S14). In one example, the control device 19 identifies the solid-liquid interface 116 using the temperature distribution information and the melting point of the material and derives temperature gradients at the solid-liquid interface 116. The control device 19 derives temperature gradients in a direction perpendicular to the layer stacking direction and in the vertical direction, which is the stacking direction. The control device 19 derives a solidification rate at the solid-liquid interface 116 by using the temperature distribution information at multiple time points.The control device 19 derives a cooling rate at any given position, using multiple individual temperature distribution data points at different times. It should be noted that the temperature gradients, solidification rate, and cooling rate itself can vary from layer to layer at the same position within the temperature measurement range. For example, the formation of an initial layer results in low heat storage in the workpiece, whereas repeated formation increases heat storage. Therefore, the temperature gradients, solidification rate, and cooling rate are all influenced by the substrate.

[0069] Next, based on the temperature gradients, solidification rate, and cooling rate in object 112 derived in step S14, the control device 19 determines the subsequent manufacturing conditions (step S15). Specifically, the control device 19 determines the manufacturing conditions for the gas ejection device 13, the wire feeder 14, the head drive unit 15, the laser oscillator 16, and the temperature control device 18 at the time of the formation of the next layer, with reference to the manufacturing condition information, such that the derived temperature gradient, solidification rate, and cooling rate in object 112 are within the specified threshold values.

[0070] Subsequently, based on the determined manufacturing conditions, the control device 19 issues commands to the gas ejection device 13, the wire feeder 14, the head drive unit 15, the laser oscillator 16, and the temperature control device 18 (step S16). In this way, the control device 19 controls the subsequent manufacturing conditions in the additive manufacturing device 1, for example, the manufacturing conditions for the next layer to be formed. This control allows the entire workpiece to be formed under manufacturing conditions where the temperature gradients, solidification rate, and cooling rate are close to the desired threshold values, and the overall structure of the workpiece becomes more homogeneous. The process then returns to step S12. The above process is then repeated until there are no further manufacturing plans.

[0071] According to the first embodiment, the temperature measuring device 17 measures the temperature distribution across the entire temperature measuring range, i.e., the formation area on the substrate 111. The control device 19 obtains temperature gradients, a solidification rate, and a cooling rate for each position in the object 112 from the temperature distribution information, which specifies the temperature distribution in the temperature measuring range. Based on the manufacturing condition information, the control device 19 sets the manufacturing conditions such that the temperature gradients, the solidification rate, and the cooling rate in a subsequently formed layer are within the desired threshold values.Accordingly, the control is implemented such that the temperature gradients, solidification rate, and cooling rate in object 112 remain within the desired threshold values ​​in each layer from the initial manufacturing phase to the final phase, within the temperature measurement range. This ensures a uniform structure of the individual layers, and the entire object 112 can achieve the desired homogeneous structure. Furthermore, by extending the temperature measurement range down to the first layer 113, and taking into account the thermal influence on a subsequent pass and heat storage during formation, homogenization of the desired structure across the entire object 112 can be achieved.Furthermore, the use of a two-color thermographic camera as a temperature measuring device 17 enables the acquisition of accurate temperature distribution information over the entire object 112, whose emissivity changes successively.

[0072] It should be noted that the temperature measuring device 17 measures the surface temperature of object 112 and not the internal temperature of object 112. The material fed to the additive manufacturing device 1 is metal, which is generally a material with high thermal conductivity. As a result of the thermal analysis of the temperature distribution during manufacturing, it was confirmed that the temperature profile at a point inside object 112, which was formed from a material with high thermal conductivity, is essentially the same as at a point on the surface of object 112. This means that the surface temperature of object 112 can be used as a substitute for the internal temperature of object 112.Therefore, as described above, the temperature of the surface of object 112 can be measured using the temperature measuring device 17 and, based on the measured surface temperature, the entire structure including the interior of object 112 can be homogenized. Second embodiment

[0073] The second embodiment describes a method for controlling the structure of object 112 by estimating the crystal shape of the structure based on derived temperature gradients and a derived solidification rate, and by performing a heating and cooling treatment after formation. The additive manufacturing device 1 used in the second embodiment corresponds to the one described in the first embodiment, so its description can be omitted. However, the functions of the control device 19 in the additive manufacturing device 1 used in the second embodiment differ from those of the first embodiment.

[0074] The control device 19 derives temperature gradients and a solidification rate from temperature distribution information about object 112 and estimates the crystal shape of object 112's structure at the derived temperature gradients and solidification rates from structural crystal shape information that specifies the relationship between the temperature gradient, the solidification rate, and the crystal shape of the structure. The structural crystal shape information is determined beforehand. The control device 19 determines whether the estimated crystal shape of the structure is the crystal shape of the desired structure. If the estimated crystal shape of the structure differs from the crystal shape of the desired structure, the control device 19 interrupts the manufacturing process and determines heating and cooling conditions for object 112 based on the estimation result.Specifically, the control device 19 determines the heating and cooling conditions under which the desired crystal structure is realized in object 112, based on a temperature gradient and a solidification rate associated with the desired crystal structure, and on the derived temperature gradients and solidification rates. Subsequently, the control device 19 controls the gas ejection device 13, the head drive unit 15, the laser oscillator 16, and the temperature control device 18 based on the determined heating and cooling conditions. This means that the control device 19 does not supply the wire W, but rather performs a heat treatment by controlling the emission of the laser beam L and the emission of the protective gas G onto object 112, and by regulating the temperature of the substrate 111 according to the specified heating and cooling conditions.After heat treatment, the control device 19 carries out the manufacturing process by controlling the gas ejection device 13, the wire feeder 14, the head drive unit 15, the laser oscillator 16, and the temperature control device 18 based on the specified manufacturing conditions. If the estimated crystal shape of the structure is the desired crystal shape, the control device 19 carries out the manufacturing process by controlling the gas ejection device 13, the wire feeder 14, the head drive unit 15, the laser oscillator 16, and the temperature control device 18 based on the specified manufacturing conditions without interrupting the manufacturing process, i.e., without performing any treatment according to the heating and cooling conditions.

[0075] In this description, the heating and cooling conditions refer to the heat treatment conditions after the formation of the final layer 114, in order to control the structure of the object 112 by reheating or recooling the solidified object 112 within a temperature range less than or equal to the melting point of the wire W. In an example, the heat treatment conditions after formation are conditions for controlling the laser beam L, the shielding gas G, and the operation of the temperature control device 18 for reheating or cooling the solidified object 112.

[0076] The relationship between the temperature gradient, solidification rate, and crystal form of the structure is not particularly restricted and can be determined in advance by any method. For example, a temperature gradient and solidification rate can be determined in advance under any manufacturing conditions by thermal analysis using the finite element method, while the structural form of object 112 can be identified in advance under the same manufacturing conditions by structural observation. Information relating manufacturing conditions, temperature gradients, solidification rates, and the crystal forms of the structure as results of structural observation can therefore be stored in advance as structural crystal state information.Alternatively, the relationship between the temperature gradient and the solidification rate and the crystal shape of the structure can be obtained from a known database published in the literature.

[0077] The relationship between heating and cooling conditions, temperature gradient, and solidification rate is not particularly restricted and can be determined in advance using any method. For example, a temperature gradient and solidification rate under any heating and cooling conditions can be determined in advance by thermal analysis using the finite element method. This means that information linking heating and cooling conditions with temperature gradients and solidification rates can be stored in advance. Alternatively, the relationship between the heating and cooling conditions, temperature gradient, and solidification rate can be determined from experimental data using the actual object 112.

[0078] If the desired structure of object 112 is an equiaxial structure and the estimated crystal shape of the structure is a columnar structure, the control device 19, according to an example, interrupts the manufacturing process and determines the heating and cooling conditions under which the structure of object 112 acquires an equiaxial structure, based on the structural crystal shape information that specifies the relationship between the temperature gradient and the solidification rate and the crystal shape of the structure.In one example, the combination of temperature gradient and solidification rate required to achieve the desired structure is obtained, and the heating and cooling conditions for object 112 are determined such that the structure specified by the combination of temperature gradient and solidification rate derived from the temperature distribution information becomes the obtained combination of temperature gradient and solidification rate. Thus, the operating conditions for the gas ejection device 13, the head drive unit 15, the laser oscillator 16, and the temperature control device 18 are determined.The combination of temperature gradient and solidification rate corresponding to the crystal shape of the desired structure is obtained from the structural crystal shape information. The heating and cooling conditions associated with the crystal shape of the desired structure are determined based on the combination of temperature gradient and solidification rate associated with the crystal shape of the desired structure and the combination of temperature gradient and solidification rate derived from the temperature distribution information about object 112. Subsequently, the control device 19 issues commands to the gas ejection device 13, the head drive unit 15, the laser oscillator 16, and the temperature setting device 18 based on the determined heating and cooling conditions. As a result, the heating or cooling treatment is controlled.A control of the heat treatment ensures that the structure of object 112 acquires a coaxial structure. This means that a treatment to achieve the desired structure is carried out by applying heat or cold treatment to object 112, including the formed final layer 114, while the manufacturing process is suspended. Afterwards, the manufacturing process is resumed. The manufacturing process for the next layer is then carried out based on the manufacturing conditions.

[0079] Fig. Figure 10 shows a flowchart to illustrate an example of the process flow of an additive manufacturing process according to the second embodiment. Fig. Figure 10 illustrates a process flow of the control device 19 in the device for additive manufacturing 1. The parts of the process that correspond to those of Fig. The 9 corresponding steps are identified by the same step numbers, and their description is omitted.

[0080] After step S15, the control device 19 estimates the crystal shape of the structure from previously obtained structural crystal shape information, which specifies the relationship between the temperature gradient and the solidification rate and the crystal shape of the structure, and from the temperature gradients and the solidification rate derived in step S14 (step S31).

[0081] The control device 19 then determines whether the estimated crystal shape of the structure corresponds to the crystal shape of the desired structure (step S32). If the control device 19 determines that the estimated crystal shape of the structure is the crystal shape of the desired structure (YES in step S32), the process continues with step S16. If the crystal shape of the structure of the formed object 112 corresponds to the crystal shape of the desired structure, no heat or cooling treatment is required to change the crystal shape of the structure of the object 112. Therefore, based on the established manufacturing conditions, the subsequent manufacturing plan described in the first embodiment is executed.

[0082] On the other hand, if the control device 19 determines that the estimated crystal shape of the structure differs from the crystal shape of the desired structure (NO in step S32), the control device 19 interrupts the manufacturing process (step S33).

[0083] Next, the control device 19 determines the heating and cooling conditions under which the structure of object 112 assumes the crystal form of the desired structure, based on the combination of temperature gradient and solidification rate associated with the crystal form of the desired structure and the combination of temperature gradient and solidification rate derived in step S14 (step S34). Subsequently, based on the determined heating and cooling conditions, the control device 19 issues commands to the gas ejection device 13, the head drive unit 15, the laser oscillator 16, and the temperature setting device 18 (step S35). By controlling the emission of the laser beam L and the ejection of the protective gas G onto object 112 and the temperature of the substrate 111 without the addition of the wire W, a post-formation heat treatment is performed to control the structure of object 112.The process then returns to step S16, and the manufacturing process continues.

[0084] According to the second embodiment, the control device 19 estimates the crystal shape of the structure of object 112 based on temperature gradients and solidification rates. If the estimated crystal shape of the structure corresponds to the crystal shape of a desired structure, the manufacturing process continues. If, on the other hand, the estimated crystal shape of the structure is not the crystal shape of the desired structure, the control device 19 temporarily interrupts the manufacturing process and controls the additive manufacturing device 1 under heating and cooling conditions determined such that the crystal shape of the structure assumes the crystal shape of the desired structure in order to perform heat treatment of object 112.Consequently, treatment based on heating and cooling conditions can be carried out to achieve the desired crystal structure, even if the resulting object 112 does not exhibit the desired crystal structure. As a result, a desired homogeneous structure of the entire object 112 can be obtained. Third embodiment

[0085] In a third embodiment, a method for controlling the structure of object 112 is described, in which the size of the structure and the type of deposited phase are estimated based on a derived cooling rate, and a heating and cooling treatment is performed after formation. The additive manufacturing device 1 used in the third embodiment is the same as that described in the first embodiment, so its description can be omitted. However, the functions of the control device 19 of the additive manufacturing device 1 used in the third embodiment differ from those of the first embodiment.

[0086] The control device 19 derives a cooling rate from temperature distribution information of object 112 and estimates the structure size and precipitated phase type of object 112 at the derived cooling rate from structure and precipitated phase information that specifies the relationship between the cooling rate and the structure size and precipitated phase type of object 112. The structure and precipitated phase information is determined beforehand. The control device 19 determines whether the estimated structure size and precipitated phase type correspond to a desired structure size and precipitated phase type.If the estimated feature size and deposition phase type deviate from the desired feature size and deposition phase type, the control device 19 interrupts the manufacturing process and determines the heating and cooling conditions for object 112 based on the estimation results. Specifically, the control device 19 determines the heating and cooling conditions under which object 112 achieves the desired feature size and deposition phase type from the cooling rate associated with the desired feature size and deposition phase type and the derived cooling rate. Subsequently, the control device 19 controls the gas ejection device 13, the head drive unit 15, the laser oscillator 16, and the temperature control device 18 based on the heating and cooling conditions.The control device 19 therefore does not feed the wire W and performs a heat treatment by controlling the emission of the laser beam L and the discharge of the protective gas G onto the object 112 and the temperature of the substrate 111 using the specified heating and cooling conditions. After the heat treatment, the control device 19 carries out the manufacturing process by controlling the gas discharge device 13, the wire feed 14, the head drive unit 15, the laser oscillator 16, and the temperature control device 18 based on the specified manufacturing conditions. If the estimated feature size and the estimated deposition phase type correspond to the desired feature size and the desired deposition phase type, the control device 19 carries out the manufacturing process under the specified manufacturing conditions without interrupting the manufacturing process, i.e., without performing any further treatment under the heating and cooling conditions.This means that the control device 19 controls the gas ejection device 13, the wire feeder 14, the head drive unit 15, the laser oscillator 16 and the temperature setting device 18 based on the manufacturing conditions and carries out the manufacturing process.

[0087] The relationship between cooling rate, feature size, and deposition phase type is not particularly restrictive and can be determined in advance using any method. For example, the cooling rate under any manufacturing conditions can be determined in advance by thermal analysis using the finite element method, while the feature size and deposition phase type of object 112 under the same manufacturing conditions can be identified in advance through structural observation. This means that information relating manufacturing conditions, cooling rates, feature sizes, and deposition phase types (which are the results of structural observation) can be stored in advance as structure and deposition phase information.Alternatively, the relationship between the cooling rate, the feature size, and the deposition phase type can be obtained from a known database published in the literature or the like. If the estimated feature size and the estimated deposition phase type differ from the desired feature size and the desired deposition phase type, a cooling rate associated with the desired feature size and the desired deposition phase type is obtained, for example, from the feature and deposition phase information, and the heating and cooling conditions associated with the desired feature size and the desired deposition phase type are determined based on the cooling rate associated with the desired feature size and the desired deposition phase type and on the cooling rate derived from the temperature distribution information about object 112.

[0088] The relationship between heating and cooling conditions and cooling rate is not particularly restricted and can be determined in advance using any method. For example, a cooling rate under any heating and cooling conditions can be determined in advance by thermal analysis using the finite element method. This means that information linking heating and cooling conditions to cooling rates can be stored in advance. Alternatively, the relationship between heating and cooling conditions and cooling rate can be derived from experimental values ​​using the actual object 112.

[0089] Fig. Figure 11 shows a flowchart to illustrate an example of the process flow of an additive manufacturing process according to a third embodiment. Fig. Figure 11 illustrates a process flow of the control device 19 in the device for additive manufacturing 1. The parts of the process that correspond to those of Fig. The 9 corresponding steps are identified by the same step numbers, and their description is omitted.

[0090] After step S15, the control device 19 estimates the structure size and the deposition phase type based on the previously obtained structure and deposition phase information, which specifies the relationship between the cooling rate and the structure size and the deposition phase type, and from the cooling rate derived in step S14 (step S51).

[0091] The control device 19 then determines whether the estimated structure size and the estimated deposition phase type correspond to the desired structure size and the desired deposition phase type (step S52). If the control device 19 determines that the estimated structure size and the estimated deposition phase type are the desired structure size and the desired deposition phase type (YES in step S52), the process continues with step S16. If the structure size and the deposition phase type of the formed object 112 correspond to the desired structure size and the desired deposition phase type, then a heating and cooling treatment to change the structure size and the deposition phase type of object 112 is therefore not necessary. Consequently, the subsequent manufacturing plan described in the first embodiment is carried out based on the determined manufacturing conditions.

[0092] If, on the other hand, the control device 19 determines that the estimated feature size and the estimated deposition phase type differ from the desired feature size and the desired deposition phase type (NO in step S52), the control device 19 interrupts the manufacturing process (step S53).

[0093] Next, the control device 19 determines the heating and cooling conditions under which the structure of object 112 acquires the desired structure size and deposition phase type, based on the cooling rate associated with the desired structure size and deposition phase type, and the cooling rate derived in step S14 (step S54). Subsequently, based on the determined heating and cooling conditions, the control device 19 issues commands to the gas ejection device 13, the head drive unit 15, the laser oscillator 16, and the temperature control device 18 (step S55). To control the structure of object 112, post-formation heat treatment is performed by controlling the emission of the laser beam L and the emission of the protective gas G onto the object 112, and by controlling the temperature of the substrate 111 without the addition of wire.The process then returns to step S16, and the manufacturing process continues.

[0094] According to the third embodiment, the control device 19 estimates the structure size and the type of deposited phase of object 112 based on a cooling rate. If the estimated structure size and the estimated deposited phase type correspond to the desired structure size and the desired deposited phase type, the manufacturing process continues. If the estimated structure size and the estimated deposited phase type differ from the desired structure size and the desired deposited phase type, the control device 19 temporarily interrupts the manufacturing process and controls the additive manufacturing device 1 under heating and cooling conditions determined such that the structure size and the deposited phase type correspond to the desired structure size and the desired deposited phase type, in order to perform a heat treatment of object 112.Even if the formed object 112 does not exhibit the desired structure size and deposition phase type, treatment based on heating and cooling conditions can be performed to achieve the desired structure size and deposition phase type. This enables homogenization of the desired structure across the entire object 112.

[0095] The configurations described in the above embodiments are examples and can be combined with other known techniques. The embodiments can be combined with one another. The configurations can be partially omitted or modified without altering the core concept. Reference symbol list 1 Device for additive manufacturing 11 Table 12 Irradiation device 13 Gas ejection device; 14 Wire feed 15 Head drive unit 16 Laser oscillator 17 Temperature measuring device 18 Temperature setting device 19 Control device 111 Substrat 112 objects 113 Initial shift 114 Final layer 114a, 114b Shift 115 Melt 116 Solid-Liquid Interface G Shielding gas L laser beam W wire QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 6228314

[0004]

Claims

[1] Device for additive manufacturing for forming an object by applying a layer, wherein the layer is a layer of molten metal, onto a substrate which serves as a base on which the object is to be formed, the device comprising: a material feed unit for supplying a material in the form of wire or powder to a workpiece on which a layer is to be formed, for layer formation in its area, a heat source supply unit for providing the workpiece with a heat source for melting the material, a temperature measuring unit for measuring the temperature of a temperature measuring range that covers the entire area in which the object is to be formed, a temperature control unit for setting the temperature by heating or cooling the object, and a control unit for controlling the material feed unit, the heat source feed unit and the temperature setting unit, wherein The control unit derives a temperature gradient in the object based on temperature distribution information, which is the result of the temperature measurement in the temperature measurement range, and a solidification rate and a cooling rate in the object based on the temperature distribution information at different times. The control unit sets the manufacturing conditions for the formation of a subsequent layer such that the derived temperature gradient, the derived solidification rate, and the derived cooling rate correspond to the temperature gradient, solidification rate, and cooling rate for the formation of a desired structure, and The control unit controls the material supply unit, the heat source supply unit and the temperature setting unit based on the manufacturing conditions in order to carry out a manufacturing process. [2] Device for additive manufacturing according to claim 1, wherein the temperature measuring unit is a two-color thermographic camera to measure the temperature of the temperature measuring area based on the intensity ratio of two different wavelengths. [3] Device for additive manufacturing according to claim 1 or 2, wherein the temperature control unit comprises a first temperature control unit for heating or cooling the substrate, The temperature measurement unit defines a temperature measurement range that includes the substrate in addition to the entire area in which the object is to be formed, and The control unit controls the material supply unit, the heat source supply unit, and the temperature setting unit based on the manufacturing conditions. [4] Device for additive manufacturing according to one of claims 1 to 3, wherein The temperature control unit includes a second temperature control unit to expel inert gas towards the workpiece for cooling purposes. The temperature measurement unit defines a temperature measurement range that includes the substrate in addition to the entire area in which the object is to be formed, and The control unit controls the material supply unit, the heat source supply unit, and the temperature setting unit based on the manufacturing conditions. [5] Device for additive manufacturing according to claim 3 or 4, wherein The control unit estimates the crystal shape of a structure of the object at the derived temperature gradient and the derived solidification rate from structural crystal shape information that specifies a relationship between the temperature gradient and the solidification rate and the crystal shape of the structure, and The control unit determines whether the estimated crystal shape corresponds to the structure of a desired crystal structure. [6] Device for additive manufacturing according to claim 5, wherein the control unit controls the material supply unit, the heat source supply unit and the temperature setting unit based on the manufacturing conditions when the estimated crystal shape of the structure corresponds to the crystal shape of the desired structure. [7] Device for additive manufacturing according to claim 5, wherein if the estimated crystal shape of the structure does not correspond to the crystal shape of the desired structure, the control unit interrupts the manufacturing process The control unit determines the heating and cooling conditions under which the object assumes the crystal form of the desired structure, based on a combination of temperature gradient and solidification rate linked to the crystal form of the desired structure, and a combination of the derived temperature gradient and the derived solidification rate. The control unit controls the heat source supply unit and the temperature setting unit to carry out a heat treatment based on the heating and cooling conditions, and The control unit controls the material supply unit, the heat source supply unit and the temperature setting unit after heat treatment based on the manufacturing conditions. [8] Device for additive manufacturing according to claim 3 or 4, wherein The control unit estimates the structure size and deposition phase type of the object at the derived cooling rate from structure and deposition phase information that specifies a relationship between the cooling rate and the structure size and deposition phase type, and The control unit determines whether the estimated structure size and the estimated deposition phase type correspond to a desired structure size and a desired deposition phase type. [9] Device for additive manufacturing according to claim 8, wherein the control unit controls the material supply unit, the heat source supply unit and the temperature setting unit based on the manufacturing conditions when the estimated feature size and the estimated deposition phase type correspond to the desired feature size and the desired deposition phase type. [10] Device for additive manufacturing according to claim 8, wherein if the estimated structure size and the estimated deposition phase type do not correspond to the desired structure size and the desired deposition phase type, the control unit interrupts the manufacturing process The control unit determines the heating and cooling conditions under which the object assumes the desired structure size and the desired deposition phase type, based on a cooling rate that is linked to the desired structure size and the desired deposition phase type, and the derived cooling rate. The control unit controls the heat source supply unit and the temperature setting unit to carry out a heat treatment based on the heating and cooling conditions, and The control unit controls the material supply unit, the heat source supply unit and the temperature setting unit after heat treatment based on the manufacturing conditions.

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