Deposition manufacturing method, deposition manufacturing device, and program

Abstract

Provided is a deposition manufacturing method for forming a deposition manufacture article 30 by using consumable electrode arc welding. During multiple repetitions of a welding cycle TW including first and second periods T1, T2, welding beads 3i formed by passing a welding current IW through a welding wire 23 are deposited to form the deposition manufacture article 30. Welding beads 3i are formed in the first period T1, and a robot 28, to which is attached a welding torch 25 holding the welding wire 23, is moved at a second speed V2 in the second period T2. The moving speed V of the robot 28 during the first period T1 is a first speed V1 (V1 < V2). The second period T2 includes an arc period TA during which an arc 27 is generated between the welding wire 23 and the deposition manufacture article 30.

Description

Layered manufacturing method, layered manufacturing device, and program

[0001] The present disclosure relates to an additive manufacturing method and an additive manufacturing apparatus.

[0002] In recent years, there has been growing interest in additive manufacturing technologies, such as 3D printers, and research and development is progressing toward practical application of additive manufacturing technologies using metallic materials in particular. Additive manufacturing technologies using metallic materials use a heat source such as a laser or arc to melt metal powder or metal wire, and then layer the molten metal to create an additively manufactured object.

[0003] For example, Patent Document 1 proposes a method for manufacturing an additive manufacturing object using a consumable electrode arc welding technique. The conventional method disclosed in Patent Document 1 includes a process for manufacturing a molten bead, a process for monitoring the temperature of the molten bead, and a process for measuring the cooling time until the molten bead is cooled to an appropriate temperature. The manufacturing of the next layer begins when the appropriate temperature is reached, and the manufacturing time for the next layer is set to be equal to or longer than the cooling time. This enables additive manufacturing using a stable arc while ensuring manufacturing accuracy.

[0004] Patent No. 6822881

[0005] However, additive manufacturing methods using consumable electrode arc welding are prone to defects specific to additively manufactured objects, such as humping, flattening, and drooling (hereinafter simply referred to as defects), due to factors such as the condition of the underlying layer of the weld bead during formation and the temperature of the weld bead and its vicinity during welding. To prevent these defects, Patent Document 1 proposes a method of monitoring the temperature of the molten bead and a method of providing a cooling time. However, measuring the temperature of the molten bead requires expensive equipment such as an infrared thermograph. Furthermore, providing a cooling time between passes, such as between the first and second layers, leads to reduced productivity.

[0006] The present disclosure has been made in consideration of these points, and its purpose is to provide an additive manufacturing method and additive manufacturing device that can suppress the occurrence of defects and form additive manufactured objects with good appearance.

[0007] In order to achieve the above-mentioned object, the additive manufacturing method according to the present disclosure is an additive manufacturing method for forming an additive manufactured object using consumable electrode arc welding, wherein a welding cycle is defined as a first period and a second period consecutive to the first period, and the additive manufactured object is formed by stacking weld beads formed by passing a welding current through a welding wire during a plurality of repeated welding cycles, wherein at least the weld beads are formed during the first period, and during the second period, a robot having a welding torch attached to a tip thereof that holds the welding wire is moved so that the tip moves at a second speed, and the moving speed of the tip of the robot during the first period is a first speed, which is lower than the second speed, and the second period includes an arc period in which an arc is generated between the welding wire and the additive manufactured object.

[0008] The additive manufacturing apparatus according to the present disclosure is an additive manufacturing apparatus that forms an additively manufactured object using consumable electrode arc welding, and includes at least a welding power source, a welding torch electrically connected to the welding power source, a robot that holds the welding torch at a tip and moves the welding torch along a predetermined trajectory, a wire feeder that feeds a welding wire held by the welding torch, an output controller that controls a welding output output from the welding power source, a wire feed speed controller that controls a feed speed of the welding wire, and a robot controller that controls operation of the robot, and by synchronizing the output controller, the wire feed speed controller, and the robot controller with each other, a welding cycle is defined as a first period and a second period that is consecutive to the first period, and the welding wire is fed while a plurality of welding cycles are repeated. the welding power source, the wire feeder, and the robot are controlled so as to form the additive object by laminating weld beads formed by passing a welding current through a welding wire; during the first period, the welding power source and the wire feeder are controlled to form at least the weld bead; during the second period, the robot is moved so that the moving speed of the tip of the robot is a second speed; when the moving speed of the tip of the robot during the first period is a first speed, the robot control unit controls the operation of the robot so that the first speed is lower than the second speed; and during the second period, the welding power source and the wire feeder are controlled so as to include an arc period in which an arc is generated between the welding wire and the additive object.

[0009] The program according to the present disclosure causes one or more processors to function as the output control unit, the wire feed speed control unit, and the robot control unit in the additive manufacturing apparatus.

[0010] According to the present disclosure, it is possible to form an additive manufacturing object with a good appearance by suppressing the occurrence of defects such as humping, flattening, and drooping. In addition, it is possible to form a weld bead stably, thereby improving productivity when forming additive manufacturing objects.

[0011] FIG. 1 is a schematic diagram of the configuration of an additive manufacturing apparatus according to the first embodiment. FIG. 2 is a time chart of various output waveforms. FIG. 3A is a time chart of various output waveforms in a first period. FIG. 3B is a time chart of various output waveforms in a second period. FIG. 4 is a time chart of the robot movement speed, average feed speed, and average welding current. FIG. 5 is a cross-sectional schematic diagram of an additively manufactured object according to a conventional method. FIG. 6 is a perspective view of an additively manufactured object according to a conventional method and an additively manufactured object according to the first embodiment. FIG. 7 is a cross-sectional schematic diagram of an additively manufactured object according to the first embodiment. FIG. 8 is a schematic diagram for explaining the movement trajectory of the tip position of the welding tip relative to the welding advance direction. FIG. 9 is a schematic diagram for explaining the movement position of a welding torch according to a modified example. FIG. 10A is a time chart of various output waveforms in a first period according to the second embodiment. FIG. 10B is a time chart of various output waveforms in a first period according to the second embodiment.

[0012] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the following description of the preferred embodiments is merely exemplary in nature and is not intended to limit the present disclosure, its applications, or its uses.

[0013] 1 is a schematic diagram of an additive manufacturing apparatus according to embodiment 1. The additive manufacturing apparatus 50 includes a welding power source 17, a welding condition setting unit 18, a wire feeder 24, a welding torch 25, a robot 28, and a robot control unit 29. The configuration of the additive manufacturing apparatus 50 is similar to that of a consumable electrode arc welding apparatus.

[0014] The welding power source 17 has a main transformer 2, a primary side rectifier 3, a switching unit 4, a DCL (reactor) 5, a secondary side rectifier 6, a welding current detector 7, a welding voltage detector 8, a control switching unit 9, an output controller 10, a wire feed speed controller 13, and a memory unit 16.

[0015] The control switching unit 9, the output control unit 10, and the wire feed speed control unit 13 are each configured with one or more central processing units (CPUs). Alternatively, the control switching unit 9, the output control unit 10, and the wire feed speed control unit 13 are each configured with one or more micro control units (MCUs). The control switching unit 9, the output control unit 10, and the wire feed speed control unit 13 may be configured with the same CPU or MCU.

[0016] Output control unit 10 has a pulse welding control unit 11 and a short-circuit welding control unit 12. Wire feed speed control unit 13 has a wire feed speed detection unit 14 and a calculation unit 15. Primary side rectification unit 3 rectifies the input voltage input from an input power source (three-phase AC power source) 1 external to welding power source 17. Switching unit 4 controls the output of primary side rectification unit 3 to an output suitable for welding. Main transformer 2 converts the output of switching unit 4 into an output suitable for welding.

[0017] The secondary side rectifier 6 rectifies the output of the main transformer 2. The DCL (reactor) 5 smoothes the output of the secondary side rectifier 6 to a current suitable for welding. The welding current detector 7 detects the welding current I flowing through the welding wire 23. Ｗ The welding voltage detection unit 8 detects the welding voltage V applied between the welding wire 23 and the layered object 30. Ｗ Detect.

[0018] The control switching unit 9 is a switching unit that outputs the timing of switching between a first period T1 and a second period T2 (see FIG. 2 ) to the output control unit 10. The control switching unit 9 has a timekeeping function and outputs the timing of switching between a first period T1 and a second period T2 (see FIG. 2 ) to the output control unit 10. Ｗ (see FIG. 2) and outputs the timing for switching between the first period T1 and the second period T2 to the output control unit 10, the wire feed speed control unit 13, and the robot control unit 29.

[0019] The output control unit 10 outputs a control signal to the switching unit 4 to control the welding output. The pulse welding control unit 11 controls pulse welding when the welding condition setting unit 18 sets the first period T1 as the pulse welding period. The short circuit welding control unit 12 controls short circuit welding in the second period T2, which is the short circuit welding period. The short circuit welding control unit 12 also controls short circuit welding when the welding condition setting unit 18 sets the first period T1 as the short circuit welding period. As will be described in detail later, the average welding current I Ｓ and average welding voltage V Ｓ or average feeding speed W Ｓ are different.

[0020] Here, the average welding current I Ｓ means the welding cycle T Ｗ Welding current I Ｗ The moving average value of the average welding voltage V Ｓ is the welding cycle T Ｗ Welding voltage V Ｗ The average feeding speed W Ｓ is the welding cycle T Ｗ The feed speed of the welding wire 23 in Ｆ ) is the moving average of

[0021] The output control unit 10 controls the average welding current I set for each of the first period T1 and the second period T2. Ｓ The welding current I Ｗ Control.

[0022] The wire feed speed control unit 13 controls the wire feed unit 24 to set the wire feed speed W Ｆ The wire feed speed detection unit 14 controls the wire feed speed W Ｆ The calculation unit 15 calculates the integrated amount of the feed of the welding wire 23 based on the signal from the wire feed speed detection unit 14. Specifically, the calculation unit 15 calculates the integrated amount of the feed of the welding wire 23 based on the signal from the wire feed speed detection unit 14. Ｆ The wire feed speed control unit 13 compares the command value and the detected value to determine the difference, and then calculates the integrated amount of the difference. The wire feed speed control unit 13 calculates the actual wire feed speed W ＦThe wire feeder 24 is feedback controlled so that the wire feeder 24 matches the command value.

[0023] The storage unit 16 is configured with a semiconductor memory such as a read-only memory (ROM), a random access memory (RAM), or an SSD (solid-state drive). Alternatively, the storage unit 16 is configured with a magnetic memory such as an HDD. The storage unit 16 stores a program describing the procedure for forming the additive manufacturing object 30. The program describes the welding output control procedure, the welding wire 23 feeding procedure, and the operation control procedure for the robot 28 for each of the first period T1 and the second period T2. The storage unit 16 also stores various setting conditions input from the welding condition setting unit 18. The storage unit 16 may be a storage medium that is detachable from the welding power source 17, such as a USB memory.

[0024] A welding condition setting unit 18 is connected to the welding power source 17. The welding condition setting unit 18 is an input unit for setting welding conditions in the welding power source 17. The welding condition setting unit 18 has a welding speed setting unit 19, a welding time setting unit 20, and an average welding current setting unit 21. The welding operator operates the welding speed setting unit 19 to set the welding speed V, in other words, the movement speed V of the tip of the robot 28 holding the welding torch 25. As will be described in detail later, the movement speed V1 in the first period T1 (hereinafter sometimes referred to as the first speed V1) and the movement speed V2 in the second period T2 (hereinafter sometimes referred to as the second speed V2) are set to be different (see FIG. 4). The welding operator also operates the welding time setting unit 20 to set the welding speed V during the welding period T Ｗ , and further, the welding period T Ｗ The welding operator sets the ratio of the first period T1 to the second period T2 in the welding time. Ｓ , and further, the average welding current I in the first period T1 Ｓ and the average welding current I in the second period T2 ＳFurthermore, welding condition setting unit 18 sets the type of welding to be performed in first period T1 in response to an operation by the welding operator. Specifically, welding condition setting unit 18 sets whether pulse welding or short-circuit welding will be performed in first period T1 in response to an operation by the welding operator.

[0025] A welding wire 23, which is a consumable electrode stored in a wire storage unit 22, is fed by a wire feed unit 24. The welding wire 23 is supplied with a welding current I via a welding tip 26 provided on a welding torch 25. Ｗ In this embodiment, the material of the welding wire 23 is mild steel, and the wire diameter is in the range of 0.8 mm to 1.6 mm. However, the material and the wire diameter of the welding wire 23 are not particularly limited to these.

[0026] Robot 28 is a known articulated robot, and holds welding torch 25 at its tip. Robot control unit 29 is composed of one or more CPUs or one or more MCUs. In response to a control command from robot control unit 29, robot 28 moves welding torch 25, which holds welding wire 23, so that the tip of welding wire 23 traces a predetermined trajectory.

[0027] Furthermore, when forming the additive manufacturing object 30 on the base 40, the welding program stored in the storage unit 16 is read out and the welding power source 17 and the robot 28 are operated. At this time, the output control unit 10, the wire feed speed control unit 13, and the robot control unit 29 are synchronized with one another to control the operation of each unit of the additive manufacturing device 50. This will be described in detail later.

[0028] [Additive Manufacturing Method] When forming the additively shaped object 30 on the base 40, arc welding is performed using a welding wire 23, which is a consumable electrode, to first form a first-layer weld bead 31 on the base 40. For example, when forming a cylindrical additively shaped object 30, a circular first-layer weld bead 31 is formed on the base 40, and a second-layer weld bead 32 is formed by overlapping the first-layer weld bead 31. This process is then repeated sequentially to obtain the additively shaped object 30.

[0029] In the additive manufacturing method shown in this embodiment, the welding cycle TW is divided into a first period T1 and a second period T2, and the moving speed V of the robot 28 and the average feeding speed W Ｓ and average welding current I Ｓ and average welding voltage V Ｓ This will be explained further below.

[0030] Fig. 2 is a time chart of various output waveforms. Fig. 3A is a time chart of various output waveforms in a first period. Fig. 3B is a time chart of various output waveforms in a second period. Fig. 4 is a time chart of the robot movement speed, average feed speed, and average welding current.

[0031] During arc welding, a welding cycle T includes a first period T1 and a second period T2. Ｗ 2, the output control unit 10 and the wire feed speed control unit 13 control the wire feed speed W Ｆ and welding current I Ｗ In response to these periodic fluctuations, the welding voltage V Ｗ also fluctuates periodically.

[0032] These behaviors will be described in more detail. As shown in FIG. 3A, in the first period T1, the forward and reverse feed of the welding wire 23 is alternately repeated, and thus the arc period T Ａ and short circuit period T Ｓ As shown at time t1 in FIG. 3A, the arc period T Ａ During the short-circuit period T Ｓ In the example, after the droplet 23A formed at the tip of the welding wire 23 is transferred to the surface of the layered object 30, the welding wire 23 is fed in the reverse direction to mechanically release the short circuit.

[0033] As shown in FIG. 3B , in the second period T2, the forward and reverse feed of the welding wire 23 is alternately repeated, so that the arc period T Ａ and short circuit period T Ｓ As shown at time t3 in FIG. 3B, the arc period T Ａ During the short-circuit period T Ｓ In the example, after the droplet 23A formed at the tip of the welding wire 23 is transferred to the surface of the layered object 30, the welding wire 23 is fed in the reverse direction to mechanically release the short circuit.

[0034] However, the average welding current I in the second period T2 Ｓ Current value I Ｌ (hereinafter, the second average welding current value I Ｌ ) is the average welding current I Ｓ Current value I Ｈ (hereinafter, the first average welding current value I Ｈ The output control unit 10 controls the welding current I Ｗ In response to this, the average feeding speed W Ｌ (Hereinafter, the second average feeding speed W Ｌ ) is the average feeding speed W Ｈ (Hereinafter, the first average feeding speed W Ｈ The wire feed speed control unit 13 controls the wire feed speed W Ｆ is controlled. In addition, the average welding voltage V Ｓ Voltage value V Ｌ (hereinafter, the second average welding voltage value V Ｌ ) is the average welding voltage V Ｓ Voltage value V Ｈ (hereinafter, the first average welding voltage value V Ｈ The output control unit 10 controls the welding output so that the welding power is smaller than the welding power (sometimes referred to as the welding power).

[0035] As shown in Fig. 4, the first period T1 in this embodiment is 0.15 seconds, and the second period T2 is 0.20 seconds. However, this is not particularly limited to this. In addition, the first average welding current value I Ｈ is 100 A, and the second average welding current value I Ｌ is 50 A. The first average feed rate W Ｈ is 5.0 m / min, and the second average feeding speed W Ｌ However, the first average welding current value I Ｈ is the second average welding current value I Ｌ The first average feeding speed W Ｈ is the second average feeding speed W Ｌ It is sufficient to set it to be higher than

[0036] 4, the first speed V1 is zero (0 m / min), and the second speed V2 is 0.7 m / min. However, the first speed V1 and the second speed V2 are not particularly limited to this. The first speed V1 may be set to be lower than the second speed V2, and the first speed V1 may be a value higher than zero.

[0037] In the additive manufacturing method described above, in the first period T1, the weld bead 3i is formed by short-circuit welding. On the other hand, in the second period T2, the welding torch 25 moves along the welding direction, and the arc period T Ａ and short circuit period T Ｓ However, the weld bead 3i is not substantially formed.

[0038] [Effects, etc.] As described above, the additive manufacturing method according to this embodiment forms the additive manufacturing object 30 using consumable electrode arc welding.

[0039] Specifically, a first period T1 and a second period T2 consecutive to the first period T1 are defined as a welding cycle T Ｗ and a plurality of welding periods T Ｗ While the above steps are repeated, the welding wire 23 is supplied with a welding current I Ｗ The weld beads 3i formed by pouring the metal are stacked to form the layered object 30.

[0040] In the first period T1, at least a weld bead 3i is formed, and in the second period T2, a robot 28 having a welding torch 25 attached to its tip that holds a welding wire 23 is moved so that the moving speed V of the tip of the robot 28 becomes a second speed V2.

[0041] The moving speed V of the tip of the robot 28 in the first period T1 is a first speed V1, which is lower than a second speed V2. The second period T2 is an arc period T Ａ Includes:

[0042] According to this embodiment, it is possible to suppress the occurrence of defects such as humping, flattening, and dripping, and to form a layered object 30 with a good appearance. This will be further explained.

[0043] FIG. 5 is a schematic cross-sectional view of a layered object manufactured by a conventional method.

[0044] In the conventional method shown in FIG. 5 and FIG. 6 described later, the moving speed V of the robot 28 is kept constant to form the weld bead 3i. In addition, the average welding current I during the period when the weld bead 3i is formed is Ｓ , average welding voltage V Ｓ and average feeding speed W Ｓ are constant.

[0045] As shown in the upper part of Figure 5, weld beads 3i to 3(i+3) are all designed to have the same height. However, when additive manufacturing object 30 is actually formed using the method described above, it was found that the actual shape of additive manufacturing object 30 has variations in the thickness and width of weld beads 3i to 3(i+3), resulting in a wavy surface, as shown in the lower part of Figure 5.

[0046] Unlike normal arc welding, when forming the additively manufactured object 30, weld beads 3(i+1), 3(i+2), and so on are stacked on top of a narrow weld bead 3i. The width of the weld bead 3i is approximately the same as or several times the wire diameter described above. Therefore, in the example shown in this embodiment, the width of the weld bead 3i is approximately 1 mm to several mm.

[0047] As a result, heat input during arc welding tends to be trapped in the weld bead 3i, etc., causing the width of the weld bead 3i to vary along the welding direction, resulting in a so-called humping bead. Furthermore, the upper surface of the weld bead 3i may soften and flatten due to the heat. If the effect of the heat input becomes even greater, the upper portion of the weld bead 3i may melt and drip.

[0048] In other words, with conventional methods, even when arc welding is performed under welding conditions that are deemed appropriate, the width and height of the weld bead 3i will fluctuate somewhat in each direction. Even if no significant fluctuations are observed when one or a few layers are stacked, when a dozen or so layers of weld beads 3i are stacked, fluctuations in the weld beads of the lower layers will be accentuated, and there is a risk of significant irregularities occurring on the surface of the additive manufacturing object 30.

[0049] On the other hand, according to the present embodiment, the robot 28 is substantially stopped and the weld bead 3i is formed in the first period T1 with the increased heat input. This reduces the amount of variation in the width and height of the weld bead 3i along each direction compared to the conventional case. In addition, even when the robot 28 is substantially stopped and a high welding current I is applied, the amount of variation in the width and height of the weld bead 3i along each direction can be reduced compared to the conventional case. Ｗ and wire feed speed W Ｆ Because arc welding is performed at this temperature, lower weld bead 3i is sufficiently melted or softened, resulting in small irregularities, which in turn suppresses variations in width and height of weld beads 3(i+1), 3(i+2), ... formed thereon.

[0050] Furthermore, during the second period T2, the robot 28 is moved while the amount of heat input to the layered object 30 is reduced, and the second period T2 also functions as a period during which the weld bead 3i is essentially cooled.

[0051] As a result, defects such as humping, flattening, and dripping caused by heat buildup in the weld bead 3i can be suppressed, and an additive manufacturing product 30 with a good appearance can be formed.

[0052] FIG. 6 is a perspective view of a layered object according to a conventional method and a layered object according to the first embodiment.

[0053] 6, when the layered object 30 was formed by the conventional method, the surface of the layered object 30 became significantly wavy due to humping, flattening, sagging, etc., and the desired shape could not be obtained. On the other hand, when the layered object 30 was formed by the method described in this embodiment, the waviness on the surface of the layered object 30 was significantly suppressed, and the layered object 30 with the desired shape could be obtained.

[0054] Also, the arc period T Ａ By providing this, it is possible to suppress the influence of the state of the arc 27 becoming unsteady at the start and end of the first period T1. For example, it is possible to suppress the state of the arc 27 from becoming unstable at the start of the first period T1. In other words, it is possible to ensure the stability of the arc welding. Furthermore, by increasing the stability of the arc welding, it is possible to suppress the generation of spatter during welding.

[0055] Furthermore, according to this embodiment, the welding period T Ｗ The welding cycle T is clearly divided into a first period T1 in which robot 28 is moved at a first low speed V1 to form weld bead 3i, and a second period T2 in which robot 28 is moved at a second high speed V2 to form weld bead 3i. Ｗ Each time, the weld bead 3i is reliably formed one block at a time, thereby forming the layered object 30.

[0056] For example, as shown in FIG. 7, in the weld beads 3i to 3(i+3), the welding period T Ｗ , and a continuous weld bead 3i is formed along the welding direction.

[0057] Furthermore, in the conventional method disclosed in Patent Document 1, a cooling period equal to or shorter than the period for forming the weld bead is provided between the period for forming the lower layer weld bead and the period for forming the upper layer weld bead, which results in a long time required to form the layered object 30, reducing productivity.

[0058] On the other hand, according to this embodiment, the weld bead 3i is formed in the first period T1, and then in the subsequent second period T2, the robot 28 is moved at a high second speed V2 while the amount of heat input to the layered object 30 is reduced. This eliminates the need for the cooling period described above, and improves productivity when forming the layered object 30.

[0059] The first speed V1 is preferably zero, and by doing so, the welding cycle T Ｗ In addition, since the tip of welding wire 23 is moved along the welding proceeding direction while arc 27 is generated during second period T2, weld bead 3i is dragged, and as a result, weld bead 3i is formed continuously along the welding proceeding direction.

[0060] In the first period T1, the welding current I Ｗ The average welding current value is the first average welding current value I Ｈ The welding current I Ｗ and the average feed speed of the welding wire 23 is set to a first average feed speed W Ｈ The welding wire 23 is fed so as to

[0061] Furthermore, in the second period T2, the welding current I Ｗ The average welding current value of the second average welding current value I Ｌ The welding current I Ｗ and the average feed speed of the welding wire 23 is set to a second average feed speed W Ｌ The welding wire 23 is fed so as to

[0062] In this case, the first average welding current value I Ｈ is the second average welding current value I Ｌ or the first average feed rate W Ｈ is the second average feeding speed W Ｌ It is preferable that the temperature is higher than 1000°C or higher than 1000°C, or both of these conditions are satisfied.

[0063] By doing so, the wire feed rate and heat input rate in the first period T1 can be reliably set to be greater than those in the second period T2. That is, by setting the first period T1 to a period of high heat input and high feed rate, the deposition rate of the welding wire 23 can be increased, ensuring the formation of the weld bead 3i. On the other hand, by setting the second period T2 to a period of low heat input and low feed rate and setting the second speed V2 higher than the first speed V1, the formation of the weld bead 3i in the second period T2 can be suppressed, and the heat input to the weld bead 3i and the underlying weld bead 3(i-1) can be reduced. This suppresses excessive heat input to the additively shaped object 30, thereby preventing defects such as humping, flattening, and sagging, resulting in the formation of an additively shaped object 30 with a good appearance.

[0064] First average welding current value I Ｈ is the second average welding current value I Ｌ or more than 1.2 times the first average feed rate W Ｈ is the second average feeding speed W Ｌ It is more preferable that the value is 1.2 times or more, or that both of the above conditions be satisfied.

[0065] This ensures that the heat input and wire feed rate in the first period T1 are different from the heat input and wire feed rate in the second period T2. This ensures that the weld bead 3i is formed in the first period T1. Furthermore, the heat input to the weld bead 3i and the underlying weld bead 3(i-1) can be reduced in the second period T2. These factors prevent defects such as humping, flattening, and sagging, and allow the formation of an additive manufacturing object 30 with a good appearance.

[0066] Welding voltage V in the first period T1 Ｗ The average welding voltage value is the first average welding voltage value V Ｈ and the welding voltage V in the second period T2 Ｗ The average welding voltage value of the second average welding voltage value V Ｌ If the first average welding voltage value V Ｈ is the second average welding voltage value V Ｌ It is preferable that the first average welding voltage value V Ｈis the second average welding voltage value V Ｌ It is more preferable that the ratio is 1.1 times or more.

[0067] This ensures a difference between the amount of heat input in the first period T1 and the amount of heat input in the second period T2. This ensures that the weld bead 3i is formed in the first period T1. Furthermore, the heat input to the weld bead 3i and the underlying weld bead 3(i-1) can be reduced in the second period T2. These factors prevent defects such as humping, flattening, and sagging, and allow the formation of an additive manufacturing object 30 with a good appearance.

[0068] In this embodiment, the first average welding voltage value V Ｈ and the second average welding voltage value V Ｌ is preferably set lower than the average welding voltage value in normal arc welding, which forms a weld bead on the base material and performs welding. In this way, excessive heat input to the additively manufactured object 30 is suppressed, and the occurrence of defects such as humping, flattening, and sagging is suppressed, making it possible to form an additively manufactured object 30 with a good appearance.

[0069] In each of the first period T1 and the second period T2, the welding wire 23 is repeatedly fed forward and backward, thereby forming an arc period T Ａ and short circuit period T Ｓ It is preferable to alternately generate the arc periods T and T. In this way, it is possible to suppress the heat input to the layered object 30 and to suppress the occurrence of spatters. As will be described later, in the first period T1, Ａ and short circuit period T Ｓ Alternatively, the weld bead 3i may be formed by a method other than so-called short-circuit welding, in which the welding is alternately performed.

[0070] The additive manufacturing apparatus 50 according to this embodiment is an apparatus that forms an additive manufacturing object 30 using consumable electrode arc welding.

[0071] The additive manufacturing apparatus 50 includes at least a welding power source 17, a wire feeder 24, a welding torch 25, a robot 28, and a robot controller 29. The welding power source 17 also includes an output controller 10 and a wire feed speed controller 13.

[0072] Welding torch 25 is electrically connected to welding power source 17. Robot 28 holds welding torch 25 at its tip and moves welding torch 25 along a predetermined trajectory. Wire feeder 24 feeds welding wire 23 held by welding torch 25. Output controller 10 controls the welding output output from welding power source 17. Wire feed speed controller 13 controls the feed speed of welding wire 23. Robot controller 29 controls the operation of robot 28.

[0073] The output control unit 10, the wire feed speed control unit 13, and the robot control unit 29 are synchronized with each other to perform the following control. Ｗ While the above steps are repeated, the welding wire 23 is supplied with a welding current I Ｗ The welding power source 17, the wire feeder 24, and the robot 28 are controlled so that the welding beads 3i formed by the flow of the welding wire are stacked to form the layered object 30.

[0074] During first period T1, welding power source 17 and wire feeder 24 are controlled to form at least weld bead 3i. During second period T2, robot 28 is moved so that the moving speed V of the tip of robot 28 becomes second speed V2.

[0075] When the moving speed V of the tip of the robot 28 during the first period T1 is a first speed V1, the robot control unit 29 controls the operation of the robot 28 so that the first speed V1 is lower than the second speed V2.

[0076] In the second period T2, an arc period T is generated between the welding wire 23 and the layered object 30. Ａ The welding power source 17 and the wire feeder 24 are controlled to include the above.

[0077] By configuring the additive manufacturing device 50 in this manner, it is possible to suppress the occurrence of defects such as humping, flattening, and drooping, and to form an additive manufacturing object 30 with a good appearance. Furthermore, it is possible to suppress the influence of the arc 27 becoming in an unsteady state at the start and end of the first period T1, thereby ensuring the stability of arc welding. Furthermore, by improving the stability of arc welding, it is possible to suppress the occurrence of spatter during welding.

[0078] It is also preferable that the output control unit 10 and the wire feed speed control unit 13 perform the following control.

[0079] In the first period T1, the output control unit 10 controls the welding current I Ｗ The average welding current value is the first average welding current value I Ｈ The welding power source 17 is controlled so that the average feed speed of the welding wire 23 is equal to or greater than the first average feed speed W Ｈ The wire feeder 24 is controlled so that:

[0080] In the second period T2, the output control unit 10 controls the welding current I Ｗ The average welding current value of the second average welding current value I Ｌ The welding power source 17 is controlled so that the average feed speed of the welding wire 23 is equal to or greater than the second average feed speed W Ｌ The wire feeder 24 is controlled so that:

[0081] By synchronizing the output control unit 10 and the wire feed speed control unit 13, the first average welding current value I Ｈ is the second average welding current value I Ｌ or the first average feed rate W Ｈ is the second average feeding speed W Ｌ Alternatively, the welding power source 17 and the wire feeder 24 are controlled so that both of the above conditions are satisfied.

[0082] This ensures a difference between the amount of heat input in the first period T1 and the amount of heat input in the second period T2. This ensures that the weld bead 3i is formed in the first period T1. Furthermore, the heat input to the weld bead 3i and the underlying weld bead 3(i-1) can be reduced in the second period T2. These factors prevent defects such as humping, flattening, and sagging, and allow the formation of an additive manufacturing object 30 with a good appearance.

[0083] In the present embodiment, output control unit 10 and wire feed speed control unit 13 are incorporated into welding power source 17, and robot control unit 29 is provided external to welding power source 17, but this is not particularly limited. For example, robot control unit 29 may be incorporated into welding power source 17, or wire feed speed control unit 13 may be provided external to welding power source 17. Furthermore, output control unit 10, wire feed speed control unit 13, and robot control unit 29 may be configured by the same CPU. Furthermore, welding condition setting unit 18 may be incorporated into welding power source 17.

[0084] Furthermore, the program according to this embodiment causes one or more CPUs (processors) to function as the output control unit 10 , the wire feed speed control unit 13 , and the robot control unit 29 in the additive manufacturing device 50 .

[0085] By configuring the program in this manner, it is possible to suppress the occurrence of defects such as humping, flattening, and drooping, and to simply and accurately control each part of the additive manufacturing device 50 to form an additive manufacturing object 30 with a good appearance.

[0086] <Modification> Fig. 8 is a schematic diagram for explaining the movement trajectory of the tip position of the welding tip relative to the welding direction. Fig. 9 is a schematic diagram for explaining the movement position of the welding torch according to a modification. For ease of explanation, in Fig. 8 and the subsequent drawings, parts that are the same as those in embodiment 1 are given the same reference numerals, and detailed explanations thereof will be omitted.

[0087] In this modified example, a case will be described in which welding torch 25 is moved in a direction away from the surface of additive manufacturing object 30 during first period T1. In the following description, the stacking direction of weld beads 3i and the direction away from additive manufacturing object 30 will be referred to as the first direction, and the stacking direction of weld beads 3i and the direction approaching additive manufacturing object 30 will be referred to as the second direction. In this modified example, the first speed V1 described above is zero (0 m / min).

[0088] 8, immediately after the start of first period T1, robot 28 moves welding torch 25 in a first direction in response to a control command from robot control unit 29 (see time point A in FIG. 8). At this time, welding torch 25, more specifically, the tip of welding tip 26, moves to first position H1 relative to initial position H0.

[0089] As shown in FIG. 9 , the initial position H0 is a position that is at least a projection length L along the first direction from the surface of the layered object 30 that faces the welding wire 23. ＥＸ The first position H1 is a position that is at least a thickness tb of the weld bead 3i away from the initial position H0 along the first direction. ＥＸ is the length from the tip of the welding tip 26 to the tip of the welding wire 23 in the second direction.

[0090] Furthermore, in response to a control command from robot control unit 29, robot 28 stops welding torch 25 when the tip of welding tip 26 reaches first position H1 (see time point B in FIG. 8 ). That is, during first period T1, welding torch 25 moves along the first direction and then stops. During this time, weld bead 3i is formed.

[0091] When first period T1 ends and second period T2 begins, robot 28 moves welding torch 25 in the welding direction and also in the second direction (see time point C in FIG. 8 ) in response to a control command from robot control unit 29. Robot control unit 29 controls the operation of robot 28 so that the tip of welding tip 26 reaches initial position H0 at the end of second period T2, i.e., at the start of first period T1.

[0092] The protrusion length L during the formation of the weld bead 3i ＥＸ If this fluctuates, the state of arc 27 and, in turn, the shape of weld bead 3i will not be stable.

[0093] According to this modification, welding torch 25 is moved along the first direction during first period T1 in which weld bead 3i is formed, so that protrusion length L ＥＸThis allows the state of arc 27 in first period T1, and therefore the shape of weld bead 3i, to be stabilized.

[0094] Furthermore, by making the tip of the welding tip 26 reach the first position H1 at the end of the first period T1, it is possible to make the surface of the layered object 30 and the tip of the welding wire 23 have a predetermined distance. Ａ In addition, when the welding wire 23 is fed forward, it is possible to prevent the welding wire 23 from penetrating the surface of the layered object 30 and causing spatter.

[0095] Furthermore, this modification can achieve the same effects as the method described in embodiment 1. That is, it is possible to suppress the occurrence of defects such as humping, flattening, and drooping, and form an additive manufacturing object 30 with a good appearance. It is also possible to suppress the effect of the arc 27 becoming unsteady at the start and end of the first period T1, thereby ensuring the stability of arc welding. Furthermore, the increased stability of arc welding can suppress the occurrence of spatter during welding.

[0096] (Embodiment 2) Fig. 10A is a time chart of various output waveforms in a first period according to embodiment 2. Fig. 10B is a time chart of various output waveforms in a first period according to embodiment 2. Note that, for ease of explanation, in Figs. 10A and 10B, the same parts as those in embodiment 1 are denoted by the same reference numerals, and detailed explanations thereof will be omitted. Furthermore, since the various output waveforms shown in Fig. 10B are the same as the various output waveforms shown in Fig. 3B, detailed explanations of Fig. 10B will be omitted.

[0097] This embodiment differs from the method shown in embodiment 1 in that pulse welding is performed to form weld bead 3i during first period T1.

[0098] As shown in FIG. 10A, the peak period T ｐ Then, the welding wire 23 is supplied with a peak current I ｐ (Current value: I ｐ ) is flowing. ｐIn this case, a droplet 23A is formed at the tip of the welding wire 23 (time t5 in FIG. 10A), and during the peak period T ｐ During this time, a droplet 23A grows.

[0099] Peak period T ｐ The base period T ｂ Then, the base current I ｂ (Current value: I ｂ ) is flowing. Peak current I ｐ Current value I ｐ is the base current I ｂ Current value I ｂ The base period T ｂ At this time, droplet 23A that has grown at the tip of welding wire 23 is detached (time t6 in FIG. 10A). After the detachment, droplet 23A is formed at the tip of welding wire 23 (time t7 in FIG. 10A).

[0100] That is, in this embodiment, in the first period T1, the wire feeding speed W Ｆ A constant value W Ｈ１ At the same time, a base current I ｂ and base current I ｂ The peak current I ｐ and are alternately flowed to form the weld bead 3i.

[0101] Also, the first average welding current value I Ｈ１ is the second average welding current value I during the second period T2. Ｌ１ In addition, the first average welding voltage value V in the first period T1 is set to be greater than Ｈ１ is the second average welding voltage value V during the second period T2. Ｌ１ is set to be larger than

[0102] As shown in this embodiment, by using pulse welding in the first period T1, the heat input can be made larger than by using short-circuit welding as shown in embodiment 1. In other words, it is possible to reliably create a difference between the heat input and wire feed rate in the first period T1 and the heat input and wire feed rate in the second period T2.

[0103] This ensures that the weld bead 3i is formed reliably in the first period T1. Furthermore, the heat input to the weld bead 3i and the underlying weld bead 3(i-1) can be reduced in the second period T2. As a result, defects such as humping, flattening, and sagging can be suppressed, and an additive manufacturing object 30 with a good appearance can be formed.

[0104] The additive manufacturing method of the present disclosure is useful because it can suppress the occurrence of defects such as humping, flattening, and drooping, and can form additive manufactured objects with good appearance.

[0105] REFERENCE SIGNS LIST 1 Input power supply 2 Main transformer (transformer) 3 Primary side rectifier 4 Switching unit 5 DCL (reactor) 6 Secondary side rectifier 7 Welding current detection unit 8 Welding voltage detection unit 9 Control switching unit 10 Output control unit 11 Pulse welding control unit 12 Short circuit welding control unit 13 Wire feed speed control unit 14 Wire feed speed detection unit 15 Calculation unit 16 Memory unit 17 Welding power source 18 Welding condition setting unit 19 Welding speed setting unit 20 Welding time setting unit 21 Average welding current setting unit 22 Wire storage unit 23 Welding wire 23A Droplet 24 Wire feed unit 25 Welding torch 26 Welding tip 27 Arc 28 Robot 29 Robot control unit 30 Layered object 3i Weld bead of ith layer (i is a positive integer) 40 Base 50 Additive Manufacturing Equipment

Claims

1. An additive manufacturing method for forming an additive object using consumable electrode arc welding, wherein a welding cycle consists of a first period and a second period consecutive to the first period, and the additive object is formed by stacking weld beads formed by passing a welding current through a welding wire during a plurality of repeated welding cycles, wherein at least the weld beads are formed during the first period, and during the second period, a robot having a welding torch attached to its tip that holds the welding wire is moved so that the tip moves at a second speed, and the moving speed of the tip of the robot during the first period is a first speed, and the first speed is lower than the second speed, and the second period includes an arc period in which an arc is generated between the welding wire and the additive object.

2. The additive manufacturing method according to claim 1, wherein the first speed is zero.

3. An additive manufacturing method according to claim 1, wherein, during the first period, the welding current is passed through the welding wire so that the average welding current value of the welding current becomes a first average welding current value, and the welding wire is fed so that the average feed speed of the welding wire becomes a first average feed speed; and during the second period, the welding current is passed through the welding wire so that the average welding current value of the welding current becomes a second average welding current value, and the welding wire is fed so that the average feed speed of the welding wire becomes a second average feed speed; and wherein the additive manufacturing method satisfies either one of the following conditions: the first average welding current value is greater than the second average welding current value, or the first average feed speed is higher than the second average feed speed.

4. An additive manufacturing method according to claim 3, characterized in that the first average welding current value is 1.2 times or more the second average welding current value, or the first average feed rate is 1.2 times or more the second average feed rate, or both of these conditions are satisfied.

5. An additive manufacturing method according to claim 3, wherein the average welding voltage value of the welding voltage during the first period is a first average welding voltage value, the average welding voltage value of the welding voltage during the second period is a second average welding voltage value, and the first average welding voltage value is higher than the second average welding voltage value.

6. The additive manufacturing method according to claim 5, wherein the first average welding voltage value is 1.1 times or more the second average welding voltage value.

7. An additive manufacturing method according to claim 1, characterized in that, during at least the second period, the welding wire is fed forward and backward repeatedly, thereby alternately generating the arc period and a short-circuit period in which the welding wire is short-circuited to the additive manufacturing object.

8. An additive manufacturing method according to claim 7, characterized in that during the first period, the forward and reverse feed of the welding wire is repeated to alternately generate the arc period and the short circuit period, thereby forming the weld bead.

9. An additive manufacturing method according to claim 7, characterized in that during the first period, the welding wire feed speed is kept constant and a base current and a peak current having a current value higher than the base current are alternately passed through the welding wire to form the weld bead.

10. An additive manufacturing method according to claim 1, wherein immediately after the start of the first period, the welding torch is moved from an initial position along a first direction, and during the second period, the welding torch is moved along a second direction so as to be located at the initial position, the first direction being the stacking direction of the weld bead and a direction away from the additive manufactured object, and the second direction being the stacking direction of the weld bead and a direction approaching the additive manufactured object.

11. An additive manufacturing method according to claim 10, wherein the initial position is a position at least the protrusion length away from the surface of the additively manufactured object facing the welding wire along the first direction, and during the first period, the welding torch is moved from the initial position along the first direction to a position at least the thickness of the weld bead, and the protrusion length is the length from the tip of a tip that is held by the welding torch and through which the welding wire is inserted to the tip of the welding wire.

12. An additive manufacturing device that forms an additive object using consumable electrode arc welding, comprising at least: a welding power source; a welding torch electrically connected to the welding power source; a robot that holds the welding torch at its tip and moves the welding torch along a predetermined trajectory; a wire feeder that feeds a welding wire held by the welding torch; an output controller that controls a welding output output from the welding power source; a wire feed speed controller that controls the feed speed of the welding wire; and a robot controller that controls operation of the robot, wherein the output controller, the wire feed speed controller, and the robot controller are synchronized with each other to define a welding cycle consisting of a first period and a second period that follows the first period, and the welding power source, the wire feeder, and the robot are controlled to form the additive object by stacking weld beads formed by passing a welding current through the welding wire during a plurality of repeated welding cycles; and the welding power source and the wire feeder are controlled to form at least the weld bead during the first period. the robot is moved in the second period so that the moving speed of the tip of the robot is a second speed; and when the moving speed of the tip of the robot in the first period is a first speed, the robot control unit controls the operation of the robot so that the first speed is lower than the second speed; and the welding power source and the wire feeder are controlled so that the second period includes an arc period in which an arc is generated between the welding wire and the layered object.

13. An additive manufacturing device according to claim 12, wherein, during the first period, the output control unit controls the welding power source so that the average welding current value of the welding current becomes a first average welding current value, and the wire feed speed control unit controls the wire feed unit so that the average feed speed of the welding wire becomes a first average feed speed; and during the second period, the output control unit controls the welding power source so that the average welding current value of the welding current becomes a second average welding current value, and the wire feed speed control unit controls the wire feed unit so that the average feed speed of the welding wire becomes a second average feed speed; and by synchronizing the output control unit and the wire feed speed control unit, the additive manufacturing device controls the welding power source and the wire feed unit so that either the first average welding current value is greater than the second average welding current value, or the first average feed speed is higher than the second average feed speed, or both of these conditions are satisfied.

14. A program for causing one or more processors to function as the output control unit, the wire feed speed control unit, and the robot control unit in the additive manufacturing device described in claim 12 or 13.

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