Control unit and control procedure for additive manufacturing system

Abstract

Control unit (9) for an additive manufacturing system (100) for emitting a heat source (L) to a feed material (53) which is fed to a workpiece (13) in order to melt the feed material (53) and solidify it into grains, and to form an object (12) by stacking the grains on the workpiece (13), wherein the control unit (9) controls a power of the heat source (L) on the one hand and / or a raster speed of the heat source (L) and a material feed speed of the feed material (53) on the other hand, based on melt bath state measurement information, wherein the melt bath state measurement information is a value which is obtained by measuring a state of a melt bath, wherein the melt bath is the molten feed material (53), wherein the control unit (9) comprises: a processing condition output unit (93) which outputs values ​​of the power of the heat source (L), the raster speed of the heat source (L) and the material feed rate to the additive manufacturing system (100); a heat source power addition unit (94) which adds a predetermined addition value (ΔP) to the power of the heat source (L) output by the processing condition output unit (93) and outputs the power of the heat source (L) to which the predetermined addition value (ΔP) has been added to the processing condition output unit (93) when: (i) a melt pool state error is less than a predetermined threshold, wherein the melt pool state error is a difference between a melt pool target state information and the melt pool state measurement information, where the melt pool target state information is a target value of the melt pool state; (ii) the power output value of the heat source (L) output by the processing condition output unit (93) is less than a maximum power (Pmax) of the heat source (L); and (iii) the scanning speed of the heat source (L) is less than a maximum scanning speed (Fmax); a melt pool state error calculation unit (91) which calculates the melt pool state error from a recorded image of the state of the melt pool; a velocity addition unit (95), which: a raster speed change value (ΔF) is added to the raster speed output by the processing condition output unit (93), and a material feed rate change value (ΔW) is added to the material feed rate output by the processing condition output unit (93); and outputs the raster speed, to which the raster speed change value (ΔF) is added, and the material feed rate, to which the material feed rate change value (ΔW) is added, to the processing condition output unit (93), wherein the raster speed change value (ΔF) is a change value of the raster speed and depends on the predetermined addition value (ΔP), wherein the material feed rate change value (ΔW) is a change value of the material feed rate and depends on the raster speed change value (ΔF), a speed adjustment unit (96) which, based on the addition of the predetermined addition value (ΔP) to the power of the heat source (L) and the addition of the raster speed change value (ΔF) and the material feed speed change value (ΔW) to the raster speed and material feed speed respectively, adjusts the raster speed of the heat source (L) and the material feed speed based on the melt pool condition error.

Description

Area

[0001] The present disclosure relates to a control device and a control method for an additive manufacturing system which adds a material to a workpiece in order to produce an object. background

[0002] A well-known method for producing a three-dimensional object is additive manufacturing (AM). One of the techniques of additive manufacturing is directed energy deposition (DED), in which a beam is emitted towards a workpiece and material is fed to an irradiation position to melt the material and form an object.

[0003] The material forms used in GED technology are broadly classified as either wire or powder. These materials are fed into a melt pool created at the workpiece by a heat source, such as radiation, causing the material to melt. Simultaneously with the material feed, the radiation position is rasterized, so that material solidifies into a grain at a point where no heat is applied. Repeating this grain formation process vertically results in the production of a three-dimensional object.

[0004] An additive manufacturing process using GED technology with laser beam irradiation is disadvantageous due to the higher heat input in the object with a larger number of stacked layers. With a constant laser output power (hereinafter simply referred to as laser power), the heat input to a region with high heat input is very large, leading to material sagging, very large grain size, etc. This results in a problem of reduced formation accuracy. However, it is difficult to set a lower laser power and estimate the amount of heat input in advance because the degree of heat input depends on the type of material being fed in, the type of workpiece material, the shape to be produced, and the number of stacked layers. To counteract this, a control technique is often used that adjusts the shape, grain size, etc.The laser measures the temperature of the melt pool and adjusts the laser power to control the amount of heat input. Although another known method is to increase the scanning speed to reduce the amount of heat input per unit length, laser power provides melt pools with high sensitivity to commands and is also easier to control than scanning speed. For this reason, in many cases, laser power is controlled as a target to be manipulated.

[0005] Patent literature 1 discloses an additive manufacturing technology using a laser-based, powder-based GED technique, which captures an image of the melt pool, detects the width or shape of the melt pool from the captured image, and, based on the detected width or shape, controls the output power and / or the raster speed of a light beam, such as a laser beam. This enables the formation of highly accurate three-dimensional stacked layers.

[0006] Patent literature 2 discloses an additive manufacturing process using a GED technique, in which the temperature of an emerging heat source is extracted from measured surface temperature data of a workpiece, and a stacking condition is modified based on a formable volume calculated from the extracted temperature of the emerging heat source. The term "stacking condition," as used herein, refers to the stacked layer height, stacked layer width, output power value, feed rate, and speed. Patent literature 3 relates to a lamination mold technology using a laser powder deposition process with laminating powder, which improves the accuracy and quality of the shape or the strength of the laminated material by controlling the lamination process.A laminating forming device comprises: a control unit for the laminating process; a laser light output mechanism for irradiation with laser light; a powder feed mechanism for supplying the laminating powder; a sensor for detecting the area of ​​a melt pool consisting of base metal and laminating powder; and a sensor for detecting or a computer for calculating the specific heat capacity of the laminated material consisting of base metal and laminating powder. The control unit comprises: a section for calculating the target value of the melt pool area based on the specific heat capacity; and a section for feedback control of the laser light output, which approximates the target value of the melt pool area. Citation list of patent literature Patent literature 1: WO 2017 / 163 429 A1 Patent literature 2: WO 2020 / 261 386 A1 Patent literature 3: JP 2019 - 112 677 A Brief description of the invention Problem to be solved by the invention

[0007] In the technology described in patent reference 1, a camera or optical sensor detects the width or shape of a melt pool, and control is performed under processing conditions such that the value of this detection data equals a setpoint. With this control, the heat source power is reduced as the number of stacked layers of shape-forming grains increases, along with the amount of heat input. This leads to a high probability that the integrated heat source output device will not fully utilize its capacity. Furthermore, when the screen speed is increased during control, the amount of material fed per unit area decreases in the technology described in patent reference 1 due to a constant material feed rate. Therefore, increasing the screen speed reduces the grain height, which leads to a problem of reduced formation accuracy.The technology described in patent literature 2, which modifies a stacking condition based on the temperature of heat generated in a workpiece, changes the stacking condition such that the stacked layer volume of a section of the workpiece in which high-temperature heat is generated is reduced. This causes a problem of decreasing the formation rate as the degree of heat generation increases.

[0008] The present disclosure was made in consideration of the above, and it is an objective of the present disclosure to provide an additive manufacturing system with a control unit which is designed not only to increase formation accuracy and formation speed, but also to make it less likely, compared to conventional technologies, that the heat source output device will not fully utilize its capacity, even when the number of stacked layers of formed grains is increased. Means to solve the problem

[0009] To solve the problem and achieve the goal described above, the present disclosure relates to a control device for an additive manufacturing system for emitting a heat source to a feed material that is fed to a workpiece in order to melt the feed material and solidify it into grains, and to form an object by stacking the grains on the workpiece, wherein the control device controls a power of the heat source on the one hand and / or a raster speed of the heat source and a material feed speed of the feed material on the other hand, based on melt bath state measurement information, wherein the melt bath state measurement information is a value that is obtained by measuring a state of a melt bath, wherein the melt bath is the molten feed material.The control unit comprises: a processing condition output unit, a heat source power addition unit, a melt pool condition error calculation unit, a velocity addition unit, and a velocity adjustment unit. The processing condition output unit provides values ​​for the heat source power, the heat source raster velocity, and the material feed velocity to the additive manufacturing system.The heat source power addition unit adds a predetermined value to the heat source power output by the processing condition output unit and outputs the heat source power with the predetermined value added to it to the processing condition output unit when: (i) a melt pool state error is less than a predetermined threshold, where the melt pool state error is a difference between a melt pool setpoint information and the melt pool state measurement information, where the melt pool setpoint information is a setpoint of the melt pool state; (ii) the heat source power output value from the processing condition output unit is less than a maximum heat source power; and (iii) the heat source raster speed is less than a maximum raster speed.The melt pool state error calculation unit calculates the melt pool state error from a captured image of the melt pool state.The speed addition unit adds a raster speed change value to the raster speed output by the processing condition output unit and adds a material feed rate change value to the material feed rate output by the processing condition output unit; and outputs the raster speed to which the raster speed change value is added and the material feed rate to which the material feed rate change value is added to the processing condition output unit, wherein the raster speed change value is a change value of the raster speed and depends on the predetermined addition value, wherein the material feed rate change value is a change value of the material feed rate and depends on the raster speed change value.The speed adjustment unit adjusts the raster speed of the heat source and the material feed rate based on the melt pool condition error by adding the predetermined addition value to the power of the heat source and adding the raster speed change value and the material feed rate change value to the raster speed and material feed rate, respectively. Effects of the invention

[0010] A control unit for an additive manufacturing system according to the present disclosure provides an advantage in that it not only increases the formation accuracy and formation speed, but also makes it less likely, compared to conventional technologies, that the heat source output device will not fully utilize its capacity, even when the number of stacked layers of formed grains is increased. Brief description of drawings Fig. Figure 1 is a schematic diagram showing an example of a configuration of an additive manufacturing system according to a first embodiment. Fig. Figure 2 is a block diagram showing an example of a functional configuration of an NC device included in the additive manufacturing system according to the first embodiment. Fig. Figure 3 is a flowchart showing an example of a procedure of a control method for maximizing the processing speed, which is carried out in the NC device of the additive manufacturing system according to the first embodiment. Fig. Figure 4 is a diagram showing an example of a relationship between the laser power and the melt pool width in a control method for the additive manufacturing system according to the first embodiment. Fig. Figure 5 is a diagram showing an example of a relationship between the raster speed and the melt pool width in the control method for the additive manufacturing system according to the first embodiment. Fig. Figure 6 is a perspective view showing an example of a method for deriving a material feed rate required for forming in the control unit for the additive manufacturing system according to the first embodiment. Fig. Figure 7 is a cross-sectional view showing an example of the method for deriving a material feed rate required for forming in the control unit for the additive manufacturing system according to the first embodiment. Fig. Figure 8 is a perspective view that schematically shows an example of a configuration of a shaped object formed by the additive manufacturing system. Fig. Figure 9 is a diagram showing an example of the effect of increasing the forming speed in a first layer, which is provided in the control method for the additive manufacturing system according to the first embodiment. Fig. Figure 10 is a diagram showing an example of the effect of increasing the forming speed in a second and upper layer, which is provided in the control method for the additive manufacturing system according to the first embodiment. Fig. Figure 11 is a diagram showing an example of behavior when the raster speed reaches a maximum achievable raster speed in the control method for the additive manufacturing system according to the first embodiment. Fig. Figure 12 is a perspective view showing an example of a method for deriving a material feed rate required for forming in the control unit for the additive manufacturing system according to a second embodiment. Fig. Figure 13 is a cross-sectional view showing an example of the method for deriving a material feed rate required for forming in the control unit for the additive manufacturing system according to the second embodiment. Fig. Figure 14 is a diagram showing an example of a hardware configuration of the NC device of the additive manufacturing system according to the first and second embodiments. Description of embodiments

[0011] A control unit and a control method for an additive manufacturing system according to embodiments of the present disclosure are described in detail below with reference to the drawings. First embodiment.

[0012] Fig. Figure 1 is a schematic diagram showing an example of a configuration of an additive manufacturing system according to a first embodiment. An additive manufacturing system 100 is an additive manufacturing system that uses a directed energy deposition (GED) technique to produce an object 12 by emitting a heat source to a feed material 53, which is fed to a workpiece 13, causing the feed material to melt and solidify into grains, which are then stacked onto the workpiece 13. The heat source can be an electric arc, a laser beam L, an electron beam, or the like. The following description assumes, for example, that the heat source is the laser beam L.

[0013] The additive manufacturing system 100 comprises a sample table 1, a processing head 2, a laser oscillator 3, a gas supply unit 4, a material feed unit 5, a raster axis drive unit 6, a camera 7, an analyzer 8 and a numerical control unit (NC unit) 9.

[0014] The sample table 1 is an element for placing and securing a substrate 11 on it. The object 12 is formed on the substrate 11. The workpiece 13 comprises the substrate 11 and the object 12 formed on the substrate 11.

[0015] The processing head 2 emits the laser beam L to a processing point where the feed material 53 is to be melted. The processing head 2 comprises a beam nozzle 21 for emitting the laser beam L to the processing point and a gas nozzle 22 for injecting a protective gas G to the processing point. The processing point, which is the irradiation position of the laser beam L, is the area where the feed material 53 is added. The processing point moves along a processing path during the additive manufacturing process.

[0016] The laser oscillator 3 oscillates the laser beam L, which is the heat source. The laser oscillator 3 is connected to the beam nozzle 21 via a fiber optic cable 31. The laser beam L, oscillated by the laser oscillator 3, propagates through the fiber optic cable 31 to the beam nozzle 21 of the processing head 2. The laser beam L is then emitted from the tip of the beam nozzle 21. The laser oscillator 3 is an example of a heat source generation device for generating the heat source.

[0017] The gas supply unit 4 injects the protective gas G from a gas supply source (not shown) through the gas nozzle 22 to the processing point. An example of a gas supply source is a gas cylinder. The gas supply source is connected to the gas nozzle 22 via a tube. The gas supply unit 4 can change the flow rate of the protective gas G based on a command value from the NC device 9. The protective gas G serves to reduce or prevent oxidation near the processing point and to provide air cooling for the object 12. Therefore, the protective gas G is preferably an inert gas, such as argon gas.

[0018] The material feeder 5 guides the feed material 53 to the irradiation position of the laser beam L, i.e., the processing point, on the workpiece 13. The material feeder 5 comprises a material feed source 51 and a material feed nozzle 52. The material feed nozzle 52 guides the feed material 53, which is supplied by the material feed source 51, to the processing point. In the first embodiment, the feed material 53 is in the form of a wire. Fig. Figure 1 shows an example of a side-feed type, in which the feed material 53 is supplied by the material feed nozzle 52, which is arranged obliquely above the processing point. Instead of a side-feed type, the material feed device 5 can be a center-feed type, in which the feed material 53 is supplied by the material feed nozzle 52, which is arranged directly above the processing point. The material feed device 5, which is operated by servo motors (not shown), can therefore change the feed rate of the feed material 53 as desired based on a command value from the NC device 9.

[0019] The raster axis drive unit 6 moves the processing head 2 and the material feeder 5 in an X-axis direction, a Y-axis direction, and a Z-axis direction. The X-axis, Y-axis, and Z-axis are perpendicular to each other. The X-axis and Y-axis are horizontal axes, and the Z-axis is a vertical axis. Furthermore, the Z-axis is defined as positive in the vertical upward direction. An example of the raster axis drive unit 6 is a set of a servo motor (not shown) for moving the processing head 2 and the material feeder 5 in the X-axis direction, a servo motor (not shown) for moving the processing head 2 and the material feeder 5 in the Y-axis direction, and a servo motor (not shown) for moving the processing head 2 and the material feeder 5 along the Z-axis direction.The operation of these servomotors makes it possible to move the irradiation position of the laser beam L and the feed position of the feed material 53 to any position within the travel range.

[0020] Camera 7, an imaging device oriented in the positive Z-axis direction coaxial with the laser beam L, captures an image of an area encompassing the processing point. For example, camera 7 captures an image of a phenomenon at the processing point and outputs the captured image to the analysis device 8 at the processing point.

[0021] The analyzer 8 analyzes the image at the processing point input from the camera 7 and detects a melt pool width, which is defined as the width of a melt pool 14. The analyzer 8 outputs the detected melt pool width, i.e., a measured melt pool width, to the NC device 9. This allows the melt pool width to be obtained in real time during the formation process. As used here, the melt pool 14 refers to a mass of molten metal formed from the workpiece 13 and the feed material 53 melted by irradiation with the laser beam L. The melt pool width is an example of melt pool state information. Melt pool state information is a value that represents a state of the melt pool 14. The measured melt pool width corresponds to melt pool state measurement information.

[0022] The NC device 9 controls the additive manufacturing system 100 according to a processing program and processing conditions. The processing program includes descriptions of a motion command and a speed command. The motion command is a command to move the processing head 2 and the material feeder 5 along a preset path. The speed command is a command for a speed along a preset raster axis. The processing conditions are a set of parameters including the height and width of a grain to be formed and the information required to achieve that height and width. The information required to form a grain includes the laser power, the raster speed of the laser beam L, the material feed rate, and the gas flow rate.The NC device 9 controls the raster axis drive unit 6, thereby moving the processing head 2 and the material feeder 5 along a path of motion specified by the processing program. The NC device 9 also provides commands to the laser oscillator 3, the raster axis drive unit 6, the material feeder 5, and the gas supply unit 4 regarding laser power, raster speed, material feed speed, and gas flow rate, respectively, which are preset according to the processing conditions. The NC device 9 corresponds to a control unit for controlling the additive manufacturing system 100. In the first embodiment, the NC device 9 is also a control unit that controls the power of the laser beam L on the one hand and / or the raster speed of the laser beam L and the material feed speed of the feed material 53 on the other hand, based on the melt pool condition measurement information. The laser beam L is the heat source.The melt bath condition measurement information is a value obtained by measuring the condition of the melt bath 14, which is formed from the molten feed material 53.

[0023] The NC device 9 can be one of the components of the additive manufacturing system 100 or can be a device that is external to the additive manufacturing system 100.

[0024] An overview of the operating mode of the additive manufacturing system 100 is now given. After the substrate 11 is attached to the sample stage 1, the NC device 9 operates the laser oscillator 3, the raster axis drive unit 6, the gas supply unit 4, and the material feed unit 5. This means that the NC device 9 controls the raster axis drive unit 6 based on the processing program. The raster axis drive unit 6 moves the processing head 2 and the material feed unit 5 along a path of movement specified by the processing program. The NC device 9 also controls the laser oscillator 3, the material feed unit 5, and the gas supply unit 4 based on the processing conditions. Therefore, the feed material 53 is guided to the processing point, the laser beam L is emitted from the laser oscillator 3 through the processing head 2 to the processing point, and the protective gas G is injected to the processing point.The emitted laser beam L forms the melt pool 14 on the workpiece 13. Upon movement of the processing head 2 and the material feed device 5 along the movement path, the irradiation position of the laser beam L and the material feed position move, so that the molten feed material 53 solidifies into a grain along the movement path.

[0025] Next, the functionality of the NC device 9 will be described. Fig. Figure 2 is a block diagram showing an example of a functional configuration of the NC device of the additive manufacturing system according to the first embodiment. Fig. In the first embodiment, the NC device 9 is given an initial processing condition 101, which includes initial values ​​for the heat source power (i.e., the laser power), the raster speed, the material feed rate, and the gas flow rate. The NC device 9 also receives a melt pool setpoint 102 and a measured melt pool width 81. The melt pool setpoint 102 was set by a user, and the measured melt pool width 81 was obtained by the analyzer 8. The melt pool setpoint 102 is the width of the melt pool 14 to be obtained by the control system and can be set to any value by the user. The melt pool setpoint 102 corresponds to a melt pool condition setpoint. Since the first embodiment is based on the assumption that the melt pool width is equal to the width of a formed grain, the value set as the melt pool setpoint 102 is the grain size that the user wishes to achieve.Furthermore, the measured melt pool width 81 is the width of the melt pool 14, which is detected by the analyzer 8 from an image captured by the camera 7. Since the image acquisition by the camera 7 and the detection by the analyzer 8 are performed during the formation process, a real-time value of the measured melt pool width 81 is entered into the NC device 9 during the formation process. In one example, the initial processing condition data 101 and the target melt pool width 102 are stored in a memory unit, which is provided either inside or outside the NC device 9.

[0026] The NC device 9 comprises a melt bath width error calculation unit 91, a processing condition adjustment unit 92, a processing condition output unit 93, a laser power addition unit 94, a speed addition unit 95, a speed adjustment unit 96 and an average processing condition calculation unit 97.

[0027] The melt pool width error calculation unit 91 calculates a melt pool width error from the difference between the target melt pool width 102 and the measured melt pool width 81. The melt pool width error is an error between the target melt pool width 102 and the measured melt pool width 81. The melt pool width error calculation unit 91 outputs the calculated melt pool width error to the processing condition adjustment unit 92. The melt pool width error corresponds to a melt pool state error. The melt pool width error calculation unit 91 is a melt pool state error calculation unit that calculates the melt pool state error from an image obtained by mapping the state of the melt pool 14.

[0028] The processing condition adjustment unit 92 receives the melt pool width error. If the melt pool width error is greater than a predetermined threshold, the processing condition adjustment unit 92 adjusts the processing conditions so that the melt pool width error becomes equal to or less than the set threshold. When a grain, i.e., a first object layer, is to be formed on the substrate 11, the processing condition adjustment unit 92 outputs the initial processing condition 101 to the processing condition output unit 93. This means that the NC device 9 performs processing with the initial processing condition 101. The processing condition adjustment unit 92 then determines whether the melt pool width error, obtained by real-time monitoring of the melt pool 14, is less than or equal to the threshold.If the melt pool width error exceeds the threshold, the processing condition adjustment unit 92 adjusts the laser power and / or the screening speed so that the melt pool width error becomes equal to or less than the set threshold. This means that the processing condition adjustment unit 92 regulates the laser power and / or the screening speed based on the melt pool width error. It should be noted that when the processing condition adjustment unit 92 changes the screening speed, it also adjusts the material feed rate in relation to the screening speed to ensure that the grain height remains unchanged. The processing condition adjustment unit 92 continues to adjust the applied processing condition until the melt pool width error becomes equal to or less than the set threshold.

[0029] The threshold is a reference value used to determine whether the measured melt pool width 81 corresponds to the target melt pool width 102 within the error range. The user can set the threshold value to any desired value. This means that the threshold is a value that allows the measured melt pool width 81 to determine whether the target melt pool width 102 and the measured melt pool width 81 correspond within the error range.

[0030] The processing condition output unit 93 receives values ​​for laser power, raster speed, and material feed rate, which are output by the processing condition adjustment unit 92, the laser power addition unit 94, the rate addition unit 95, and the rate adjustment unit 96, as described later. The processing condition output unit 93 outputs these input values ​​for laser power, raster speed, and material feed rate to the additive manufacturing system 100, i.e., the laser oscillator 3, the raster axis drive unit 6, and the material feeder 5. The laser oscillator 3, the raster axis drive unit 6, and the material feeder 5 operate according to command values ​​from the processing condition output unit 93.

[0031] If the melt pool width error is greater than the threshold, the processing conditions are entered from the processing condition adjustment unit 92 into the processing condition output unit 93. If the melt pool width error is less than or equal to the threshold, the processing conditions are entered from the laser power addition unit 94, the velocity addition unit 95, and the velocity adjustment unit 96 into the processing condition output unit 93.

[0032] If the melt pool width error, which is a difference between the target melt pool width 102 and the measured melt pool width 81, is smaller than the predetermined threshold and the laser power output by the processing condition output unit 93 is smaller than the maximum power of the laser oscillator 3, the laser power addition unit 94 outputs a post-add value of the laser power to the processing condition output unit 93, where the post-add value is the laser power value to which a predetermined addition value has been added. Specifically, the laser power addition unit 94 receives the laser power and raster speed values ​​output by the processing condition output unit 93.If the entered laser power value falls within a certain range of the maximum power of the laser oscillator 3 contained in the additive manufacturing system 100, and the entered raster speed value does not reach the maximum achievable raster speed Fmax, the laser power addition unit 94 adds a predetermined addition value ΔP to the laser power value. The laser power addition unit 94 outputs the laser power value with the added value to the processing condition output unit 93. The addition value ΔP is a value that can be set by the user to any desired value. The laser power addition unit 94 is equivalent to a heat source power addition unit.

[0033] If the raster speed value output by the processing condition output unit 93 is less than a predetermined value, the speed addition unit 95 outputs a post-addition raster speed to the processing condition output unit 93, where the post-addition value is the raster speed to which a raster speed change value ΔF (hereinafter referred to as a raster speed change value ΔF) has been added, the raster speed change value being dependent on the laser power addition value ΔP. Specifically, the speed addition unit 95 receives the raster speed and material feed speed values ​​output by the processing condition output unit 93.Once the laser power addition unit 94 has added the addition value ΔP to the laser power value, the velocity addition unit 95 adds the screen speed change value ΔF to a screen speed F based on the laser power addition value ΔP, such that the melt pool width does not exceed the target melt pool width 102. The velocity addition unit 95 also adds a change value ΔW of the material feed rate (hereinafter referred to as material feed rate change value ΔW) to a material feed rate W based on the screen speed change value ΔF, ensuring that the grain height remains constant. The velocity addition unit 95 outputs the post-addition values ​​of the screen speed and the material feed rate to the processing condition output unit 93.

[0034] The laser power addition unit 94 and the speed addition unit 95 change the processing conditions incrementally, which can cause the melt pool width error to exceed the value obtained through the control performed by the processing condition adjustment unit 92. In response, the speed adjustment unit 96 adjusts the raster speed and the material feed rate based on the melt pool width error. Specifically, the speed adjustment unit 96 receives the melt pool width error and adjusts the raster speed so that the melt pool width error is equal to or less than the set threshold value.When the speed adjustment unit 96 adjusts the screening speed, it also simultaneously adjusts the material feed rate based on the screening speed adjustment amount (hereinafter referred to as the screening speed adjustment value) so that the grain height remains unchanged. This means that the speed adjustment unit 96 controls both the screening speed and the material feed rate based on the melt pool width error. The speed adjustment unit 96 outputs the adjusted screening speed and material feed rate values ​​to the processing condition output unit 93.It should be noted that the configuration discussed herein has a function of preferential maintenance of the laser power, to which the addition value by the laser power addition unit 94 has been added, and therefore the laser power is not adjusted.

[0035] The mean processing condition calculation unit 97 receives the laser power, raster speed, and material feed rate values ​​output by the processing condition output unit 93 and calculates mean values ​​for the same object layer. This means that the mean processing condition calculation unit 97 calculates mean laser power, mean raster speed, and mean material feed rate values ​​at the time of grain formation in a single object layer. The mean laser power is a mean heat source power.

[0036] It should be noted that the processing condition adjustment unit 92 causes the additive manufacturing system 100 to operate using the initial processing condition 101 and performs a control of the laser power on the one hand and / or the raster speed and the material feed rate on the other hand, wherein the initial processing condition 101 is predetermined initial values ​​of the laser power, the raster speed and the material feed rate at the beginning of the formation of a first object layer formed from a grain.Furthermore, when changing the object layer being formed, the processing condition adjustment unit 92 instructs the additive manufacturing system 100 to operate using the values ​​of the average laser power, average raster speed, and average material feed rate of an object layer formed immediately before the change. These values ​​are then used as the laser power, raster speed, and material feed rate values ​​at the beginning of the object layer formation process after the change. The processing condition adjustment unit 92 then regulates the laser power on the one hand and / or the raster speed of the heat source and the material feed rate on the other.In this way, the processing condition adjustment unit 92 uses the values ​​of the mean laser power, mean raster speed and mean material feed rate calculated by the mean processing condition calculation unit 97.

[0037] Next, the internal processing of the NC device 9 is described. Fig. Figure 3 is a flowchart illustrating an example procedure of a control method for maximizing processing speed, which is performed in the NC device of the additive manufacturing system according to the first embodiment. First, the processing condition adjustment unit 92 receives the initial processing condition 101 and the melt pool setpoint 102 (step S11). The initial processing condition 101 includes values ​​for the laser power, raster speed, and material feed rate. Next, processing begins based on the initial processing condition 101 (step S12). The processing condition adjustment unit 92 outputs the initial processing condition 101 to the processing condition output unit 93.The processing condition output unit 93 outputs an initial laser power value to the laser oscillator 3, outputs an initial raster speed value to the raster axis drive unit 6, and outputs an initial material feed speed value to the material feed device 5.

[0038] After processing starts, camera 7 captures an image of the processing position, i.e., an image showing the state of the melt pool 14, and outputs the image to the analyzer 8. The analyzer 8 detects the measured melt pool width 81 from the image and inputs the measured melt pool width 81 into the melt pool width error calculation unit 91. The melt pool width error calculation unit 91 then calculates a melt pool width error, which is the difference between the target melt pool width 102 and the measured melt pool width 81 output by the analyzer 8 (step S13). The melt pool width error calculation unit 91 determines whether the melt pool width error is less than or equal to a predetermined threshold value (step S14).

[0039] If the melt pool width error is not less than or equal to the threshold value (the "no" case in step S14), the processing condition adjustment unit 92 receives the melt pool width error from the melt pool width error calculation unit 91 and adjusts the laser power value on the one hand and / or the raster speed and material feed rate values ​​on the other hand according to the melt pool width error value (step S15). A conceivable adjustment method for use in this process is, for example, a control system such as a proportional-integral differential (PID) controller. When the processing condition adjustment unit 92 adjusts the raster speed, it also adjusts the material feed rate as described above, depending on the raster speed change value, so that the height of the grain to be formed does not change.

[0040] If the melt pool width error is a positive value, meaning that the melt pool width in the forming process is smaller than the target melt pool width 102, the processing condition adjustment unit 92 issues a command to increase the laser power or decrease the raster speed. Conversely, if the melt pool width error is a negative value, meaning that the melt pool width in the forming process is larger than the target melt pool width 102, the processing condition adjustment unit 92 issues a command to decrease the laser power or increase the raster speed.

[0041] The processing condition adjustment unit 92 then outputs the adjusted laser power and / or the adjusted raster speed and material feed speed to the processing condition output unit 93. The processing condition output unit 93 provides the processing condition, which reflects either the adjusted laser power value or the adjusted raster speed and material feed speed values ​​(step S16). When adjusting the laser power, the processing condition output unit 93 outputs the adjusted laser power value to the laser oscillator 3. When adjusting the raster speed, the processing condition output unit 93 outputs the adjusted raster speed value to the raster axis drive unit 6 and outputs the adjusted material feed speed value to the material feeder 5.The laser oscillator 3 on the one hand and / or the raster axis drive unit 6 and the material feed device 5 on the other hand operate with the command value entered into them in order to change the melt pool width in the formation process so that the changed melt pool width corresponds to the melt pool setpoint width 102.

[0042] The process then determines whether processing for the individual object layer has been completed (step S22). In an example, this determination is made by the processing condition adjustment unit 92. If processing for this individual object layer has not yet been completed (the "no" case in step S22), the process returns to step S13. The processing condition adjustment unit 92 then repeats the processing shown in steps S15 and S16 until the melt pool width error is equal to or less than the threshold value. This means that only the control process by the processing condition adjustment unit 92 is carried out until the melt pool width in the formation process matches the melt pool target width 102.

[0043] In contrast, the case in which the melt pool width error is less than or equal to the threshold value in step S14 (the "yes" case in step S14) is the case in which the melt pool width changes as a result of the process in steps S15 and S16 and corresponds to the melt pool target width 102 with the error range. In this case, the laser power addition unit 94 receives the laser power and raster speed values ​​from the processing condition output unit 93 and determines whether the adjusted laser power is less than an oscillator's own maximum power Pmax and the raster speed is less than the maximum achievable raster speed Fmax. In the case of Fig. Step 3, the laser power addition unit 94, determines from the obtained laser power value whether the laser power P is less than the oscillator's own maximum power Pmax (step S17). Then, the laser power addition unit 94 determines whether the raster speed F is less than the maximum achievable raster speed Fmax, i.e., the maximum raster speed achievable by the raster axis drive unit 6 (step S18). The determination in step S17 is performed based on the hardware of the included laser oscillator 3. The determination in step S18 is performed based on processing stability.

[0044] The oscillator's maximum power Pmax represents the maximum possible output value provided by the hardware specifications of the laser oscillator 3, which is included in the additive manufacturing system 100, and which can be used in processing. Furthermore, the maximum achievable raster speed Fmax represents the highest raster speed that ensures control stability. In an example, the maximum achievable raster speed Fmax is derived from an index representing control stability, which is determined as a result of preliminary experimental processing performed using different raster speeds.

[0045] If the adjusted laser power P is less than the oscillator's own maximum power Pmax (the "yes" case in step S17) and the raster speed F is less than the maximum achievable raster speed Fmax (the "yes" case in step S18), the laser power addition unit 94 determines that an increase in laser power is feasible. This means that the laser power addition unit 94 adds the predetermined addition value ΔP to the laser power P (step S19) and outputs the laser power value P with the added addition value ΔP to the processing condition output unit 93. The processing condition output unit 93 then commands the laser oscillator 3 with the laser power value to which the addition value was added.

[0046] Adding the addition value to the laser power value at step S19 will increase the melt pool width above the target melt pool width 102. Therefore, when adding the addition value to the laser power at step S19, the velocity addition unit 95 adds the raster speed change value ΔF to the raster speed F. Adding the raster speed change value ΔF to the raster speed F reduces the amount of heat input per unit length, thus reducing the melt pool width. To maintain a constant grain height, the velocity addition unit 95 adds the material feed rate change value ΔW to the material feed speed W as a function of the raster speed change value ΔF (step S20).

[0047] When the processing conditions are changed incrementally, i.e., the laser power, the raster speed, and the material feed rate, at steps S19 and S20, the measured melt pool width 81 may not match the target melt pool width 102. To counteract this, the speed adjustment unit 96 adjusts the raster speed and the material feed rate depending on the melt pool width error, which is obtained from the melt pool width error calculation unit 91 (step S21). This means that the speed adjustment unit 96 controls the raster speed and the material feed rate depending on the melt pool width error.In one example, the speed adjustment unit 96 adjusts the raster speed F using a raster speed adjustment value ΔFfb to control the raster speed based on the melt pool width error. The speed adjustment unit 96 also adjusts the material feed rate W using a material feed rate adjustment value ΔWfb to control the material feed rate based on the melt pool width error. This reduces the resulting melt pool width error. It should be noted that, in order to maintain the command value to which the addition value was added in step S19, the laser power value is not adjusted in the process at step S21.

[0048] The processing condition adjustment unit 92 then determines whether processing for that single object layer has been completed (step S22). If processing for that single object layer has not yet been completed (the "no" case at step S22), the process returns to step S13 to continue processing for the same object layer. This means that if the melt pool width error is less than or equal to the threshold, processing is performed using the laser power, raster speed, and material feed rate values ​​obtained by the adjustment and addition in the process from step S17 to step S21, after which the process returns to step S13 to readjust the processing conditions.

[0049] If the laser power P is greater than or equal to the oscillator's own maximum power Pmax at step S17 (the case "no" at step S17) or if the raster speed F is greater than or equal to the maximum achievable raster speed Fmax at step S18 (the case "no" at step S18), the laser power addition unit 94 determines that increasing the laser power is not feasible and the process proceeds to step S22.

[0050] If the processing condition adjustment unit 92 determines at step S22 that processing for that single object layer is complete (the "yes" case at step S22), the processing condition adjustment unit 92 determines whether the formation is complete (step S23). If the processing condition adjustment unit 92 determines that the formation of an object is not yet complete (the "no" case at step S23), it is time to switch the object layer being formed. When the object layer being formed is switched, the formation position and heat generation state change. Therefore, it is not desirable for the processing conditions obtained through adjustment and / or addition in the process from step S15 to step S21 during the formation of the object layer immediately before the switch to continue being used for processing the object layer after the switch.Furthermore, the use of the initial processing condition 101 can lead to instability of the formation process immediately after the start of processing due to a different heat generation state.

[0051] In the first embodiment, the mean processing condition calculation unit 97 therefore calculates mean values ​​of the processing conditions that were used for the object layer formed immediately before the changeover. This means that the mean processing condition calculation unit 97 calculates the mean laser power, mean raster speed, and mean material feed rate, which are mean values ​​of the laser power, raster speed, and material feed rate for the object layer formed immediately before the changeover (step S24). Processing of the next object layer then begins based on the values ​​of the mean laser power, mean raster speed, and mean material feed rate, which are mean values ​​of the processing conditions that were used for the object layer formed immediately before the changeover (step S25).Because the average laser power, average raster speed, and average material feed rate are processing conditions that reflect the heat generation state in the object layer formed immediately before the changeover, the stability immediately after the start of processing is improved compared to the case in which the initial processing condition 101 is used. The process then proceeds to step S13. However, if the processing condition adjustment unit 92 determines that object formation is complete (the "yes" case at step S23), the processing condition output unit 93 terminates the process.

[0052] A method in which the velocity addition unit 95 calculates the material feed rate change value ΔW as a function of the raster velocity change value ΔF is described next. Fig. Figure 4 is a diagram showing an example of a relationship between the laser power and the melt pool width in the control method for the additive manufacturing system according to the first embodiment. Fig. Figure 5 is a diagram showing an example of the relationship between the raster speed and the melt pool width in the control method for the additive manufacturing system according to the first embodiment. In graph G11 in the upper section of Fig. 4 represents the horizontal axis (position) and the vertical axis (laser power). In graph G12, in the lower section of Fig. 4 represents the horizontal axis, the position, and the vertical axis represents the melt pool width. Fig. Figure 4 shows graph G11 in the upper section and graph G12 in the lower section, with their positions aligned relative to each other. In graph G21 in the upper section of Fig. In graph G22, the horizontal axis represents the position and the vertical axis represents the raster velocity. In the lower section, the horizontal axis represents the position and the vertical axis represents the melt pool width. Fig. Figure 5 shows graph G21 in the upper section and graph G22 in the lower section, with the positions aligned relative to each other. The position represented along the horizontal axis in each of these graphs is, for example, a position on a movement path.

[0053] In Fig. 4 denotes ΔM as the change in melt pool width (hereinafter referred to as the melt pool width change value) when the laser power is increased by the predetermined addition value ΔP. The melt pool width change value ΔM can be expressed as equation (1) below, assuming that the melt pool width change value ΔM is a function with one variable, which is the addition value ΔP of the laser power. This relationship between the melt pool width change value ΔM and the addition value ΔP of the laser power must be determined beforehand. ΔM=f(ΔP)

[0054] Furthermore, in Fig. 5 ΔF is the raster speed change value for reducing the melt pool width by ΔM. The raster speed change value ΔF can be expressed as equation (2) below, assuming that the raster speed change value ΔF is a function with one variable, which is the melt pool width change value ΔM. This relationship between the raster speed change value ΔF and the melt pool width change value ΔM must be determined beforehand. ΔF=g(ΔM)

[0055] The raster speed change value ΔF, by which the raster speed must be changed to maintain the melt pool width when the laser power changes by the addition value ΔP, can be derived from equations (1) and (2) as expressed by equation (3) below. ΔF=g(f(ΔP))

[0056] This means that equation (3) can provide the raster velocity change value ΔF when the laser power is changed by the addition value ΔP.

[0057] It takes time to acquire and analyze the image before calculating the measured melt pool width 81. A change in the raster speed results in a delayed response in the melt pool width. These factors cannot be ignored if the raster speed exceeds a predetermined value, which would lead to the raster speed not being adjusted correctly. This raster speed limit, which allows for correct adjustment, is called the maximum achievable raster speed Fmax. This maximum achievable raster speed Fmax is set by the user, who takes into account the camera sampling rate 7, the analysis duration of the analyzer 8, the command output period of the NC device 9, and the melt pool width's response delay with respect to the raster speed.

[0058] If the raster speed is greater than the maximum achievable raster speed Fmax, the laser power addition unit 94 does not perform any laser power addition operation, and the speed addition unit 95 does not perform any addition operations of the raster speed and the material feed speed. This means that the speed adjustment unit 96 does not adjust the raster speed and the material feed speed.

[0059] Fig. Figure 6 is a perspective view showing an example of a method for deriving a material feed rate required for forming in the control unit for the additive manufacturing system according to the first embodiment. Fig. Figure 7 is a cross-sectional view showing an example of the method for deriving a material feed rate required for forming in the control unit for the additive manufacturing system according to the first embodiment. As shown in Fig. 6 and Fig. As shown in Figure 7, if the feed material 53 is in wire form, all of the feed material 53 is melted and a grain 15 is formed without excess or vacancy, such that the volume of grain 15 formed per unit time is equal to the volume of feed material 53 supplied per unit time. In this respect, the material feed rate W, the screen speed F, and a grain cross-sectional area S are related, as expressed by equation (4) below. W=F×S

[0060] As in Fig. As shown in Figure 7, a grain size M, which is the width of the grain 15 at a cross-section of the grain 15, and a grain height H, which is the height of the grain 15 at the cross-section of the grain 15, form a quadrilateral, and the proportion of a grain cross-sectional area S to the area of ​​this quadrilateral is given by a grain cross-sectional area factor K. This grain cross-sectional area factor K is introduced to account for the geometric shape of the grain 15, and its value can be set by the user to any desired value. The grain cross-sectional area S is expressed by equation (5) below using the grain size M, the grain height H, and the grain cross-sectional area factor K. S=M×H×K

[0061] Accordingly, equation (4) can be rewritten as equation (6) below using the grain size M, the grain height H and the grain cross-sectional area factor K. W=F×(M×H×K)

[0062] From the above, the change value ΔW of the material feed rate W, which is to be used when the screen speed F is changed by ΔF, can be calculated as equation (7) below. It should be noted that the grain height H is a target formation height H. soll is a value that can be set by the user to any desired value. Assuming that the melt pool width is equal to the grain size, a measured melt pool width M can also be used. messen The grain size M, which is obtained in real time during the formation process, is used. This means that the velocity addition unit 95 calculates the material feed rate change value ΔW using the measured melt pool width M. messen , the target level of education H soll , the raster velocity change value ΔF and the geometric shape of the grain 15 can be calculated. ΔW=ΔF×(Mmessen×Hsoll×K)

[0063] Fig. Figure 8 is a perspective view that schematically shows an example of a configuration of a shaped object formed by the additive manufacturing system. Fig. Figure 8 shows a situation in which the object, which is formed from six layers of grains 15, is formed on the substrate 11.

[0064] Fig. Figure 9 is a diagram showing an example of the effect of improving the forming speed in a first layer, as provided in the control method for the additive manufacturing system according to the first embodiment. In graph G31 in the upper section of Fig. 9 represents the horizontal axis as the position and the vertical axis as the measured melt pool width. In graph G32, in the middle section of Fig. 9 represents the horizontal axis as the position and the vertical axis as the laser power. In graph G33 in the lower section of Fig. 9 represents the horizontal axis (position), the left vertical axis (raster speed), and the right vertical axis (material feed speed). Fig. Figure 9 shows graph G31 in the upper section, graph G32 in the middle section, and graph G33 in the lower section, with the positions aligned relative to each other. It should be noted that the position represented along the horizontal axis in each of these graphs, for example, is a position along a movement path.

[0065] The first layer, i.e., a grain 15a of the first layer on the substrate 11 of Fig. 8, will be, as in Fig. Figure 9 shows the processing such that processing begins using the values ​​of an initial laser power, an initial material feed rate, and an initial raster speed, which were determined as the initial processing condition 101. The processing condition adjustment unit 92 adjusts the laser power so that the measured melt pool width 81 matches the target melt pool width 102. When changing the position from S0 to S1, this means that the raster speed and the material feed rate remain constant, but only the laser power is reduced, thus enabling the measured melt pool width 81 to match the target melt pool width 102.

[0066] While the measured melt pool width 81 matches the target melt pool width 102 at position S1, the laser power P at position S1 is lower than the oscillator's maximum power Pmax in graph G32, and the raster speed F at position S1 is lower than the maximum achievable raster speed Fmax in graph G33. Therefore, the laser power addition unit 94 adds the value ΔP to the laser power P. This involves adding change values ​​ΔF and ΔW to the raster speed F and the material feed rate W, respectively. After adding these change values, the measured melt pool width 81 deviates from the target melt pool width 102, resulting in a melt pool width error. Consequently, the raster speed F and the material feed rate W are adjusted to control the melt pool width error so that the controlled error reaches or falls below the threshold value.As a result, the raster speed F and the material feed rate W are not constant, but increase slowly in graph G33, while the laser power P in graph G32 has a constant value between the addition of the addition value ΔP to the laser power P and the next addition of the addition value ΔP to the laser power P, after the measured melt pool width 81 matches the melt pool target width 102.

[0067] The addition of the additive value ΔP to the laser power P is then performed several times, increasing the laser power P to the maximum power Pmax of the integrated oscillator. Simultaneously with the addition of the additive value ΔP to the laser power P, the change value ΔF is added to the raster speed F, and the change value ΔW is added to the material feed rate W. Then, after the laser power P reaches the maximum power Pmax of the integrated oscillator at position S2, the processing condition adjustment unit 92 continues the adjustment process by regulating the processing conditions.

[0068] As described above, increasing the laser power P to the oscillator's own maximum power allows the material feed rate W to increase, leading to an improvement in the formation rate.

[0069] Fig. Figure 10 is a diagram showing an example of the effect of increasing the forming speed in second and higher layers, as provided in the control method for the additive manufacturing system according to the first embodiment. In graph G41 in the upper section of Fig. In graph G42, in the middle section of... Fig. 10 represents the horizontal axis as the position and the vertical axis as the laser power. In graph G43 in the lower section of Fig. 10 represents the horizontal axis as the position, the left vertical axis as the raster speed, and the right vertical axis as the material feed speed. Fig. Figure 10 shows graph G41 in the upper section, graph G42 in the middle section, and graph G43 in the lower section, with the positions aligned relative to each other. It should be noted that the position represented along the horizontal axis in each of these graphs is, for example, a position along a movement path.

[0070] The values ​​of the mean laser power, mean raster speed, and mean material feed rate for the immediately preceding object layer are used as the values ​​of the laser power, raster speed, and material feed rate at the beginning of the formation of the second and subsequent upper layers, with an example of this being grain 15b of a fifth layer in Fig. 8 is. Since the formation begins with processing conditions that reflect the heat generation state, the accuracy of the formation is improved. This is because the time elapsed until the measured melt pool width 81 matches the melt pool target width 102 is lower compared to using the initial processing condition 101 in Fig. 9 is reduced.

[0071] Fig. Figure 11 is a diagram showing an example of the behavior when the raster speed reaches the maximum achievable raster speed in the control method for the additive manufacturing system according to the first embodiment. In graph G51 in the upper section of Fig. Figure 11 represents the horizontal axis as the position and the vertical axis as the measured melt pool width. In graph G52, in the middle section of Fig. Figure 11 represents the horizontal axis as the position and the vertical axis as the laser power. In graph G53, in the lower section of Fig. 11 represents the horizontal axis as the position, the left vertical axis as the raster speed, and the right vertical axis as the material feed speed. Fig. Figure 11 shows graph G51 in the upper section, graph G52 in the middle section, and graph G53 in the lower section, with the positions aligned relative to each other. It should be noted that the position represented along the horizontal axis in each of these graphs is, for example, a position along a path of movement.

[0072] As in Fig. As shown in Figure 11, if the raster speed F reaches the maximum achievable raster speed Fmax before the laser power P reaches the oscillator's own maximum power Pmax, no addition process is performed for the laser power P, thus preventing the laser power P from reaching the oscillator's own maximum power Pmax. This means that in some cases, depending on the setting value of the maximum achievable raster speed Fmax or the heat generation state, the laser power P may not reach the oscillator's own maximum power Pmax. Therefore, using the oscillator's own maximum power Pmax from the start of processing is unsuitable; however, the laser power P must be increased incrementally.

[0073] According to the first embodiment, the laser power on the one hand and / or the raster speed and material feed rate on the other hand are controlled until the melt pool width error becomes zero, i.e., until the measured melt pool width 81 matches the target melt pool width 102. If the raster speed does not reach the maximum achievable raster speed Fmax after the measured melt pool width 81 matches the target melt pool width 102, the laser power for processing is increased to the oscillator's own maximum power Pmax, and simultaneously the raster speed and material feed rate are increased. In this case, the raster speed and material feed rate are adjusted by a control system based on the melt pool width error.This not only makes it less likely that the laser output device, which is the heat source, will not fully utilize its capacity, but also ensures that the highest possible formation rate is achieved with the output power of the integrated oscillator while maintaining a desired grain height. Because it becomes possible to reduce or prevent the reduction in grain height that would occur with an increase in the screening speed, formation rate can be improved without compromising formation accuracy. Conventional technology reduces the amount of heat input per unit area, particularly for the upper layer section of stacked grains with high heat input, by decreasing the laser power or increasing the screening speed. In contrast, the first embodiment increases both the screening speed and the material feed rate without reducing the laser power.This makes it possible to improve the formation accuracy and formation speed compared to conventional technology, even in an upper layer section of object 12, which has a higher heat output than a section without heat output.

[0074] When forming the next object layer, the average laser power, average raster speed, and average material feed rate of the immediately preceding object layer are used as the processing conditions at the start of the next object layer formation. This can improve the formation accuracy because the processing stability of each object layer is improved compared to the start of processing the respective object layer using the preset initial processing condition 101. Second embodiment.

[0075] The in Fig. The material feed device 5 shown in Figure 1 guides the feed material 53 from the material feed nozzle 52. The first embodiment was described with reference to an example of the feed material 53 in wire form. A second embodiment is described with reference to an example of the feed material 53 in powder form.

[0076] The additive manufacturing system 100 of the second embodiment is configured essentially the same as that of the first embodiment. Differences from the first embodiment are described below. As described above, in the second embodiment, the material feeder 5 supplies the feed material 53 in powder form from the material feed nozzle 52. Although the form of the feed material 53 has changed from a wire to a powder, the same advantages can be provided by the modified method for deriving the material feed rate required for formation in the rate-adding unit 95.

[0077] Fig. Figure 12 is a perspective view showing an example of a method for deriving a material feed rate required for forming in the control unit for the additive manufacturing system according to the second embodiment. Fig. Figure 13 is a cross-sectional view showing an example of the method for deriving a material feed rate required for generation in the control unit for the additive manufacturing system according to the second embodiment. It should be noted that Fig. Figure 12 shows an example in which the material feed nozzle 52 of the material feed device 5 is arranged in the processing head 2.

[0078] Not all of the feed material 53 contributes to the formation because some of the feed material 53, in powder form, does not fall into the melt bath 14 during feeding. Feed material 53a, which does contribute to the formation, can be expressed by equation (8) below, where the symbol W schmelz The feed rate of the feed material 53a, which contributes to the formation, is represented, and symbol A represents a formation contribution rate, where the feed rate W is assumed to be schmelz of the feed material 53a, which contributes to the formation, is proportional to the material feed rate W and the formation contribution rate A is a ratio of the feed rate W schmelz The ratio of the feed material 53a to the material feed rate W is the educational contribution rate A, which can be set to any value by the user, taking into account the device configuration, etc. Wmelting = W×A

[0079] This means that replacing the material feed rate W in the first embodiment with the feed rate W schmelz of the feed material 53a, which contributes to the formation, it makes it possible to calculate the change value ΔW of the material feed rate W in the second embodiment, as shown in equation (9) below. ΔW=ΔF×(Mmeasure×Hsoll×K) / A

[0080] Advantages equivalent to those of the first embodiment can also be provided in the second embodiment by calculating the change value ΔW of the material feed rate W using equation (9), which takes into account a feed material 53x that does not contribute to the formation.

[0081] It should be noted that in the preceding description, the laser power addition unit 94 performs the addition process on the laser power, whereupon the velocity addition unit 95 then performs an addition process on the raster speed and the material feed speed. However, these addition processes can be performed in reverse order. This means that the process at step S19 and the process at step S20 in Fig. 3 can be swapped.

[0082] Furthermore, the speed adjustment unit 96 and the processing condition adjustment unit 92 of the first and second embodiments adjust the applied processing conditions, receiving the melt pool width error as an input for this purpose. However, the adjustment of the processing conditions can be performed with an input of a difference from a target value of the area or shape of the melt pool 14 instead of the difference from the target value of the melt pool width. This means that the melt pool state can be the area or shape of the melt pool 14, and the processing conditions can be adjusted with an input of a difference between the melt pool target state information, which is a target value of the melt pool 14 state, and a melt pool state measurement information, which is a measured value of the melt pool 14 state.

[0083] A hardware configuration of the NC device 9 of the additive manufacturing system 100 is now described. Fig. Figure 14 is a diagram showing an example of a hardware configuration of the NC device of the additive manufacturing system according to the first and second embodiments.

[0084] The NC device 9 can be integrated into a control circuit 300, i.e., a processor 301 and a memory 302, which are in Fig. Examples of the 301 processor include a central processing unit (CPU) (also known as a processing unit, arithmetic unit, microprocessor, microcomputer, processor, and digital signal processor (DSP)) and a highly integrated system. Examples of the 302 memory include random-access memory (RAM) and read-only memory (ROM).

[0085] If a functionality of the melt bath width error calculation unit 91, the processing condition adjustment unit 92, the processing condition output unit 93, the laser power addition unit 94, the velocity addition unit 95, the velocity adjustment unit 96 and the mean processing condition calculation unit 97 of Fig.2. The functionality of the processor 301 is implemented partially or completely in the processor 301 and software, firmware, or a combination of software and firmware. The software or firmware is described in the form of a program and is stored in memory 302. The processor 301 reads a program stored in memory 302 and executes it to partially or completely implement the functionality of the melt pool width error calculation unit 91, the processing condition adjustment unit 92, the processing condition output unit 93, the laser power addition unit 94, the velocity addition unit 95, the velocity adjustment unit 96, and the mean processing condition calculation unit 97.

[0086] If the functionality of the melt pool width error calculation unit 91, the processing condition adjustment unit 92, the processing condition output unit 93, the laser power addition unit 94, the speed addition unit 95, the speed adjustment unit 96 and the average processing condition calculation unit 97 is partially or completely implemented in the processor 301, the NC device 9 is configured such that the memory 302 stores the program which causes steps to be executed, wherein these steps are to be partially or completely carried out by the melt pool width error calculation unit 91, the processing condition adjustment unit 92, the processing condition output unit 93, the laser power addition unit 94, the speed addition unit 95, the speed adjustment unit 96 and the average processing condition calculation unit 97.It can also be said that the program stored in memory 302 causes a computer to carry out a procedure or process which is to be carried out partially or completely by the melt bath width error calculation unit 91, the processing condition adjustment unit 92, the processing condition output unit 93, the laser power addition unit 94, the velocity addition unit 95, the velocity adjustment unit 96 and the mean processing condition calculation unit 97.

[0087] A control program, which is to be executed by the processor 301 and describes a control procedure for the additive manufacturing system 100, can be stored in a computer-readable storage medium in the form of an installable or executable file and provided as a computer program product. Furthermore, the control program to be executed by the processor 301 can be provided to the NC device 9 of the additive manufacturing system 100 via a network, such as the Internet.

[0088] Furthermore, the NC device 9 can be implemented in a dedicated hardware element. Additionally, the functionality of the NC device 9 can be implemented partly in a dedicated hardware element and partly in software or firmware.

[0089] The configurations described in the preceding embodiments are merely examples. These configurations can be combined with other known technologies, and configurations of different embodiments can be combined with one another. Furthermore, a portion of such configurations can be omitted and / or modified without altering their essence. Reference symbol list 1 sample table; 2 processing heads; 3 Laser oscillator; 4 Gas supply unit; 5 Material feeder; 6 grid axis drive unit; 7 cameras; 8 Analyzer; 9 NC device; 11 Substrate; 12 shaped object; 13 workpieces; 14 Melt bath; 15, 15a, 15b grain; 21 jet nozzle; 22 Gas nozzle; 31 fiber optic cables; 51 Material supply source; 52 Material feed nozzle; 53 Supply material; 53a Feed material which contributes to shaping; 53x feed material that does not contribute to shaping; 91 Melt pool width error calculation unit; 92 Processing condition adjustment unit; 93 Processing condition output unit; 94 Laser power addition unit; 95 Speed ​​Addition Unit; 96 Speed ​​Adjustment Unit; 97 Average processing condition calculation unit; 100 Additive manufacturing system; G Shielding gas; L laser beam.

Claims

[1] Control unit (9) for an additive manufacturing system (100) for emitting a heat source (L) to a feed material (53) which is fed to a workpiece (13) in order to melt the feed material (53) and solidify it into grains, and to form an object (12) by stacking the grains on the workpiece (13), wherein the control unit (9) controls a power of the heat source (L) on the one hand and / or a raster speed of the heat source (L) and a material feed speed of the feed material (53) on the other hand, based on melt bath state measurement information, wherein the melt bath state measurement information is a value which is obtained by measuring a state of a melt bath, wherein the melt bath is the molten feed material (53), wherein the control unit (9) comprises: a processing condition output unit (93) which outputs values ​​of the power of the heat source (L), the raster speed of the heat source (L) and the material feed rate to the additive manufacturing system (100); a heat source power addition unit (94) which adds a predetermined addition value (ΔP) to the power of the heat source (L) output by the processing condition output unit (93) and outputs the power of the heat source (L) to which the predetermined addition value (ΔP) has been added to the processing condition output unit (93) when: (i) a melt pool state error is less than a predetermined threshold, wherein the melt pool state error is a difference between a melt pool target state information and the melt pool state measurement information, where the melt pool target state information is a target value of the melt pool state; (ii) the power output value of the heat source (L) output by the processing condition output unit (93) is less than a maximum power (Pmax) of the heat source (L); and (iii) the scanning speed of the heat source (L) is less than a maximum scanning speed (Fmax); a melt pool state error calculation unit (91) which calculates the melt pool state error from a recorded image of the state of the melt pool; a velocity addition unit (95), which: a raster speed change value (ΔF) is added to the raster speed output by the processing condition output unit (93), and a material feed rate change value (ΔW) is added to the material feed rate output by the processing condition output unit (93); and outputs the raster speed, to which the raster speed change value (ΔF) is added, and the material feed rate, to which the material feed rate change value (ΔW) is added, to the processing condition output unit (93), wherein the raster speed change value (ΔF) is a change value of the raster speed and depends on the predetermined addition value (ΔP), wherein the material feed rate change value (ΔW) is a change value of the material feed rate and depends on the raster speed change value (ΔF), a speed adjustment unit (96) which, based on the addition of the predetermined addition value (ΔP) to the power of the heat source (L) and the addition of the raster speed change value (ΔF) and the material feed speed change value (ΔW) to the raster speed and material feed speed respectively, adjusts the raster speed of the heat source (L) and the material feed speed based on the melt pool condition error. [2] Control unit (9) for the additive manufacturing system (100) according to claim 1, wherein the velocity addition unit (95) calculates the raster velocity change value (ΔF) using a predetermined relationship between the power of the heat source (L) and the state of the melt pool and a predetermined relationship between the raster velocity and the state of the melt pool. [3] Control unit (9) for the additive manufacturing system (100) according to claim 1, wherein the velocity addition unit (95) calculates the material feed rate change value (ΔW) using the melt bath state measurement information, the raster velocity and a geometric shape of one of the grains. [4] Control unit (9) for the additive manufacturing system (100) according to any one of claims 1 to 3, further comprising: a processing condition adjustment unit (92) which causes the additive manufacturing system (100) to operate at the beginning of the formation of a first object layer formed from one of the grains, using predetermined initial values ​​for the power of the heat source (L), the screen speed of the heat source (L), and the material feed rate, and to adjust the power of the heat source (L) on the one hand and / or the screen speed of the heat source (L) and the material feed rate on the other hand, wherein, when changing an object layer to be formed, the processing condition adjustment unit (92) causes the additive manufacturing system (100) to use values ​​of an average heat source power,to work with a mean raster speed and a mean material feed rate for an object layer formed immediately before the changeover as values ​​of the power of the heat source (L), the raster speed of the heat source (L) and the material feed rate at the beginning of the formation of an object layer after the changeover and to adjust the power of the heat source (L) on the one hand and / or the raster speed of the heat source (L) and the material feed rate on the other hand. [5] Control unit (9) for the additive manufacturing system (100) according to claim 4, further comprising an average processing condition calculation unit (97) which calculates the values ​​of the average heat source power, the average raster speed and the average material feed rate at a time of formation of one of the grains of a single object layer. [6] Control method for a control unit (9) for controlling an additive manufacturing system (100) for emitting a heat source (L) to a feed material (53) which is fed to a workpiece (13) in order to melt the feed material (53) and solidify it into grains, and to form an object (12) by stacking the grains on the workpiece (13), wherein the control unit (9) controls a power of the heat source (L) on the one hand and / or a raster speed of the heat source (L) and a material feed speed of the feed material (53) on the other hand, based on melt bath state measurement information, wherein the melt bath state measurement information is a value which is obtained by measuring a state of a melt bath, wherein the melt bath is the molten feed material (53), wherein the control method comprises: a processing condition output step in which the control unit (9) outputs values ​​of the power of the heat source (L), the raster speed of the heat source (L) and the material feed rate to the additive manufacturing system (100); a heat source power addition step in which the control unit (9) adds a predetermined addition value (ΔP) to a value of the heat source power (L) when: a melt pool state error is less than a predetermined threshold, wherein the melt pool state error is a difference between a melt pool setpoint information and the melt pool state measurement information, where the melt pool setpoint information is a setpoint of the melt pool state; the value of the heat source power (L) output by the control unit (9) is less than a maximum power (Pmax) of the heat source (L); and the raster speed of the heat source (L) is less than a maximum raster speed (Fmax); a melt pool state error calculation step in which the control unit (9) calculates the melt pool state error from an image of the state of the melt pool; a velocity addition step in which the control unit (9) adds a raster velocity change value (ΔF) to the output raster velocity and adds a material feed velocity change value (ΔW) to the output material feed velocity, wherein the raster velocity change value (ΔF) is a change value of the raster velocity and depends on the predetermined addition value (ΔP), wherein the material feed velocity change value (ΔW) is a change value of the material feed velocity and depends on the raster velocity change value (ΔF); a speed adjustment step in which the control unit (9) adjusts the raster speed of the heat source (L) and the material feed rate based on the melt pool condition error to the addition of the predetermined addition value (ΔP) to the power of the heat source (L) and the addition of the raster speed change value (ΔF) and the material feed rate change value (ΔW) to the raster speed and the material feed rate, respectively. where steps from the processing condition output step to the speed adjustment step are repeated until the power of the heat source (L) reaches the maximum power of the heat source (L). [7] Control method for the additive manufacturing system (100) according to claim 6, wherein the control unit (9) in the velocity addition step calculates the raster velocity change value (ΔF) using a predetermined relationship between the power of the heat source (L) and the state of the melt pool and a predetermined relationship between the raster velocity and the state of the melt pool. [8] Control method for the additive manufacturing system (100) according to claim 6, wherein the control unit (9) in the velocity addition step calculates the material feed rate change value (ΔW) using the melt bath state measurement information, the raster velocity and a geometric shape of one of the grains. [9] Control method for the additive manufacturing system (100) according to any one of claims 6 to 8, further comprising: a processing condition adjustment step in which the control unit (9) causes the additive manufacturing system (100) to operate at the beginning of the formation of a first object layer formed from one of the grains, using predetermined initial values ​​for the power of the heat source (L), the raster speed of the heat source (L), and the material feed rate, and to adjust the power of the heat source (L) on the one hand and / or (ii) the raster speed of the heat source (L) and the material feed rate on the other hand, wherein, in the processing condition adjustment step, when changing an object layer to be formed, the control unit (9) causes the additive manufacturing system (100) to use values ​​of an average heat source power,to work with a mean raster speed and a mean material feed rate for an object layer formed immediately before the changeover as values ​​of the power of the heat source (L), the raster speed of the heat source (L) and the material feed rate at the beginning of the formation of an object layer after the changeover and to adjust the power of the heat source (L) on the one hand and / or the raster speed of the heat source (L) and the material feed rate on the other hand. [10] Control method for the additive manufacturing system (100) according to claim 9, further comprising an average processing condition calculation step in which the control unit (9) calculates the values ​​of the average heat source power, the average raster speed and the average material feed rate at a time of formation of one of the grains of a single object layer.

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