Laminate molding welding method

Abstract

To provide a laminate molding welding method using arc welding for manufacturing a molded object of high quality, suppressing the occurrence of an uneven shape on a bead.SOLUTION: A laminate molding welding method manufactures a molded object by: melting, through arc welding, a welding wire 1 fed from a weld torch WT and solidifying the melted welding wire so as to form a bead; and laminating the formed bead. In the method: the arc welding is a welding with two electrode arcs formed of a preceding consumable electrode arc 3b and a subsequent non-consumable electrode arc 3a; and a value of a welding current Ia of the non-consumable electrode arc 3a is calculated using a function to which a feeding speed Fr of the welding wire 1 of the consumable electrode arc 3b is inputted.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an additive manufacturing welding method in which a welding wire fed from a welding torch is melted and solidified by arc welding to form a bead, and the formed beads are stacked to manufacture a molded object. [Background technology]

[0002] 3D printers for metal materials use a heat source such as an arc or laser to melt metal wire or metal powder to form a bead, and then stack the formed beads to produce a model.

[0003] The invention of Patent Document 1 is an additive manufacturing welding method using a consumable electrode arc, which includes a bead forming process for forming a bead layer, a process for measuring the shape of the bead layer, and a smoothing bead forming process for forming a smoothing bead for smoothing the bead layer according to the measured shape of the bead layer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 7203671 Summary of the Invention [Problem to be solved by the invention]

[0005] In the lamination process, if the welding condition becomes unstable, the bead that is formed often has an uneven shape. In some cases, the uneven shape can be improved to be flat by welding the next layer, but in most cases, the uneven shape is not improved and the layers are laminated as is, resulting in a poor appearance. In the invention of Patent Document 1, the uneven shape of the bead is measured and a process of flattening the uneven shape is carried out. However, this method requires a measuring process and a flattening process, which reduces work efficiency.

[0006] Therefore, an object of the present invention is to produce a high-quality object by suppressing the occurrence of uneven shapes in a bead in an additive manufacturing welding method using arc welding. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, the invention of claim 1 comprises: 1. An additive manufacturing welding method for manufacturing a molded object by melting and solidifying a welding wire fed from a welding torch by arc welding to form a bead, and stacking the formed beads, comprising: The arc welding is a two-electrode arc welding formed from a leading consumable electrode arc and a trailing non-consumable electrode arc. The present invention relates to an additive manufacturing welding method.

[0008] The invention of claim 2 is as follows: calculating a value of a welding current of the non-consumable electrode arc using a function having as an input a welding wire feed speed of the consumable electrode arc; 2. The method for additive manufacturing welding according to claim 1.

[0009] The invention of claim 3 is as follows: Detecting an indicator correlated with the stability of the welding state of the consumable electrode arc; Controlling the value of the welding current of the non-consumable electrode arc based on the index 3. The additive manufacturing welding method according to claim 1 or 2.

[0010] The invention of claim 4 is as follows: The consumable electrode arc is a short-circuit transfer arc that repeats a short circuit period and an arc period, The indicator is detected based on at least one of a duration of the short circuit period, a duration of the arc period, and an occurrence of an arc interruption. 4. The method for additive manufacturing welding according to claim 3. Effect of the Invention

[0011] According to the method for additive manufacturing using arc welding according to the present invention, it is possible to manufacture a high-quality object by suppressing the occurrence of irregularities in the bead. [Brief description of the drawings]

[0012] [Figure 1] 1 is a block diagram of a welding apparatus for carrying out an additive manufacturing welding method according to an embodiment of the present invention. [Diagram 2] 2 is a timing chart of each signal in the welding device of FIG. 1 , illustrating the additive manufacturing welding method according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0014] 1 is a block diagram of a welding device for carrying out an additive manufacturing welding method according to an embodiment of the present invention. Each block will be described below with reference to the diagram.

[0015] The welding torch WT surrounded by the dashed line includes a non-consumable electrode 1a, a plasma gas nozzle 4 surrounding the non-consumable electrode 1a, a power feed tip 6 that feeds power to the welding wire 1b, which is a consumable electrode, and a shielding gas nozzle 5 surrounding both the plasma gas nozzle 4 and the power feed tip 6. A tungsten electrode or the like is used for the non-consumable electrode 1a. A non-consumable electrode arc 3a is generated between the non-consumable electrode 1a and the workpiece 2. A consumable electrode arc 3b is generated between the welding wire 1b and the workpiece 2. In the figure, the non-consumable electrode arc 3a is a plasma arc, but it may be a TIG arc. In the figure, both the plasma gas nozzle 4 and the power feed tip 6 are surrounded by one shielding gas nozzle 5, but they may each be surrounded by a different shielding gas nozzle 5. The non-consumable electrode arc 3a and the consumable electrode arc 3b may each be a separate welding torch WT. In this case, each welding torch is mounted on the second robot RM.

[0016] A plasma gas flows through the plasma gas nozzle 4. A shielding gas flows through the shielding gas nozzle 5. Argon gas is used as the plasma gas. Carbon dioxide gas or a mixture of argon gas and carbon dioxide gas is used as the shielding gas.

[0017] The non-consumable electrode arc 3a is generated between the non-consumable electrode 1a and the workpiece 2, and a non-consumable electrode welding current Ia is applied. The consumable electrode arc 3b is generated between the welding wire 1b and the workpiece 2, and a welding current Ib is applied and a welding voltage Vb is applied. The non-consumable electrode arc 3a is generated when the non-consumable electrode 1a is the negative electrode and the workpiece 2 is the positive electrode. The consumable electrode arc 3b is generated when the welding wire 1b is the positive electrode and the workpiece 2 is the negative electrode. A two-electrode arc is formed in which the consumable electrode arc 3b is the leading electrode and the non-consumable electrode arc 3a is the trailing electrode. The distance between the two arcs is set to a distance that forms one molten pool or a distance that forms independent molten pools, and is about 3 to 10 mm. The welding wire 1b fed from the welding torch WT is melted and solidified by the consumable electrode arc 3b, and remelted and solidified by the non-consumable electrode arc 3a so that the bead is flat to form a bead, and the formed beads are stacked to manufacture a molded object.

[0018] The robot RM is equipped with the above-mentioned welding torch WT and a feeder WM, which will be described later, and its movement is controlled by an input of a movement control signal Rc, which will be described later.

[0019] The robot control device RC outputs a movement control signal Rc for controlling the movement of the robot RM according to pre-stored teaching data. The robot control device RC divides the layered object into multiple layers based on the shape data of the layered object, and generates layer shape data representing the shape of each layer. Furthermore, the robot control device RC stores the movement trajectory of the torch tip position as teaching data based on the generated layer shape data.

[0020] The welding voltage setting circuit VR outputs a predetermined welding voltage setting signal Vr, and the feed speed setting circuit FR outputs a predetermined feed speed setting signal Fr.

[0021] The welding voltage detection circuit VD detects the welding voltage Vb and outputs a welding voltage detection signal Vd. The short circuit determination circuit SD receives the welding voltage detection signal Vd and outputs a short circuit determination signal Sd that goes to a high level when the welding voltage detection signal Vd is equal to or greater than a reference voltage value (approximately 10 V) and determines that the welding state of the consumable electrode arc 3b is in a short circuit period, and goes to a low level when the welding voltage detection signal Vd is less than a reference voltage value (approximately 10 V) and determines that the welding state is in an arc period. The welding current detection circuit ID detects the welding current Ib and outputs a welding current detection signal Id.

[0022] The welding condition indicator circuit AD receives the short circuit determination signal Sd and the welding current detection signal Id, performs the following processing, and outputs a welding condition indicator signal Ad. 1) When the time length during which the short circuit determination signal Sd is at a high level (short circuit period) is equal to or longer than a reference value (approximately 10 ms), a welding condition indicator signal Ad that is at a high level for a predetermined period (approximately 50 ms) is output. 2) When the time length during which the short circuit determination signal Sd is at low level (arc period) is equal to or longer than a reference value (approximately 20 ms), a welding condition indicator signal Ad that goes high for a predetermined period (approximately 50 ms) is output. 3) When the value of the welding current detection signal Id becomes 0 and it is determined that an arc has been cut off, a welding condition indicator signal Ad that goes high for a predetermined period (about 50 ms) is output.

[0023] The non-consumable electrode welding current setting circuit IAR receives the above-mentioned feed speed setting signal Fr as an input and outputs a non-consumable electrode welding current setting signal Iar calculated by a predetermined function. The function is a function whose calculated value increases as the value of the feed speed setting signal Fr increases. The function is set in advance by experimentation so that the bead can be flattened by the non-consumable electrode arc 3a.

[0024] The non-consumable electrode welding current control setting circuit ICR receives as input the non-consumable electrode welding current setting signal Iar and the welding state index signal Ad, and outputs the value of the non-consumable electrode welding current setting signal Iar as the non-consumable electrode welding current control setting signal Icr when the welding state index signal Ad is at a low level, and outputs a value obtained by adding a predetermined increase value (approximately 50 A) to the value of the non-consumable electrode welding current setting signal Iar as the non-consumable electrode welding current control setting signal Icr when the welding state index signal Ad is at a high level.

[0025] The non-consumable electrode arc welding power source PSA receives the non-consumable electrode welding current control setting signal Icr and outputs the non-consumable electrode welding current Ia set by the non-consumable electrode welding current control setting signal Icr through constant current control.

[0026] The consumable electrode arc welding power source PSB receives the above-mentioned welding voltage setting signal Vr as an input, and outputs a welding voltage Vb that is set by the welding voltage setting signal Vr through constant voltage control.

[0027] The feeder WM receives the above-mentioned feed speed setting signal Fr and feeds the welding wire 1b at the feed speed set by the feed speed setting signal Fr. While the figure shows a case where the welding wire 1b is fed at a constant speed, forward / reverse feeding may be used in which the welding wire 1b is fed forward during an arcing period and fed backward during a short circuit period.

[0028] Fig. 2 is a timing chart of each signal in the welding device of Fig. 1, which illustrates an additive manufacturing welding method according to an embodiment of the present invention. Fig. 2(A) shows the change over time in the welding voltage Vb of the leading consumable electrode arc, Fig. 2(B) shows the change over time in the welding current Ib of the leading consumable electrode arc, Fig. 2(C) shows the change over time in the non-consumable electrode welding current Ia of the trailing non-consumable electrode arc, and Fig. 2(D) shows the change over time in the welding state indicator signal Ad. The operation of each signal will be described below with reference to Fig. 2 and Fig. 1.

[0029] The figure shows the case of a short-circuit transfer arc in which consumable electrode arc 3b repeats an arc period and a short-circuit period between welding wire 1 and workpiece 2.

[0030] During the short circuit period from time t1 to t2, as shown in Fig. 1(A), the welding voltage Vb has a short circuit voltage value of several volts, and as shown in Fig. 1(B), the welding current Ib increases over time. During the arc period from time t2 to t3, as shown in Fig. 1(A), the welding voltage Vb has an arc voltage value of several tens of volts, and as shown in Fig. 1(B), the welding current Ib decreases over time. The same applies to the operation during the short circuit period from time t3 to t4 and the arc period from time t4 to t5.

[0031] When the time length of the short circuit period from time t5 reaches the reference value at time t51, as shown in FIG. 1B, the welding current Ib increases rapidly to the short circuit release current value. Then, at time t51, as shown in FIG. 1D, the welding state indicator signal Ad goes to high level and maintains the high level for a predetermined period from time t51 to t9. As shown in FIG. 1C, since the welding state indicator signal Ad is low level before time t51, the non-consumable electrode welding current Ia becomes the value set by the non-consumable electrode welding current setting signal Iar in FIG. 1. The non-consumable electrode welding current setting signal Iar becomes a value calculated by a predetermined function that inputs the value of the feed speed setting signal Fr in FIG. 1. The function is a function that calculates a larger value as the value of the feed speed setting signal Fr increases. The function is set in advance by experiment so that the bead can be flattened by the non-consumable electrode arc 3a.

[0032] As shown in FIG. 1C, since the welding state index signal Ad is at a high level during a predetermined period from time t51 to t9, the non-consumable electrode welding current Ia becomes a value obtained by adding a predetermined increase value to the non-consumable electrode welding current setting signal Iar in FIG.

[0033] The period from time t6 to t7 is an arc period, the period from time t7 to t8 is a short circuit period, the period from time t8 to t9 is an arc period, and the period from time t9 to t10 is a short circuit period.

[0034] When the predetermined period ends at time t9, the welding condition indicator signal Ad returns to low level as shown in (D) of the figure, and in response, the non-consumable electrode welding current Ia returns to the value before time t51 as shown in (C) of the figure.

[0035] The welding state indicator signal Ad shown in FIG. 1D is an indicator that correlates with the stability of the welding state of the consumable electrode arc. The welding state indicator signal Ad is determined to be unstable when at least one of the following occurs: the time length of the short circuit period is equal to or greater than a reference value, the time length of the arc period is equal to or greater than a reference value, and an arc interruption occurs, and the welding state indicator signal Ad is at a high level for a predetermined period. During the predetermined period, the value of the non-consumable electrode welding current Ia shown in FIG. 1C is increased by an increased value. This allows the bead to be flattened by increasing the current value of the non-consumable electrode arc to increase the heat input, thereby preventing the bead from becoming uneven due to the welding state of the consumable electrode arc becoming unstable. The predetermined period is the time during which the bead can be flattened, and is about 50 to 100 MS. In FIG. 1D, the short circuit period and the arc period are shown as being two cycles during the predetermined period from time t51 to t9, but in reality, they are about 5 to 10 cycles.

[0036] The effects of this embodiment will be described below. According to this embodiment, in an additive manufacturing welding method in which a welding wire fed from a welding torch is melted and solidified by arc welding to form a bead, and the formed beads are stacked to manufacture a shaped object, the arc welding is two-electrode arc welding formed from a leading consumable electrode arc and a trailing non-consumable electrode arc. A molten pool is formed by the leading consumable electrode arc and then solidified to form a bead. The molten pool in the solidification process is re-melted by the non-consumable electrode arc and then solidified, thereby preventing the bead from becoming uneven and making it flat.

[0037] More preferably, according to this embodiment, the value of the welding current of the non-consumable electrode arc is calculated by a function having the welding wire feed speed of the consumable electrode arc as an input. Since the molten pool becomes larger as the feed speed of the consumable electrode arc increases, the heat input of the non-consumable electrode arc for remelting the molten pool needs to be increased. For this reason, if the value of the welding current of the non-consumable electrode arc is set by a function having the feed speed as an input, the molten pool can be smoothly remelted, and the bead can be more effectively prevented from becoming uneven.

[0038] More preferably, according to this embodiment, an index correlating with the stability of the welding state of the consumable electrode arc is detected, and the value of the welding current of the non-consumable electrode arc is controlled based on the index. When the welding state of the consumable electrode arc becomes unstable, the possibility of the bead having an uneven shape increases. Therefore, if the value of the welding current of the non-consumable electrode arc is changed based on the index correlating with the stability of the welding state of the consumable electrode arc, the occurrence of the uneven shape can be more effectively suppressed.

[0039] More preferably, according to this embodiment, the consumable electrode arc is a short-circuit transfer arc which repeats short circuit periods and arc periods, and the indicator is detected based on at least one of the duration of the short circuit period, the duration of the arc period, and the occurrence of arc interruption. This makes it possible to detect the stability of the welding state of the consumable electrode arc, and by changing the value of the welding current of the non-consumable electrode arc based on the detection result, the occurrence of unevenness can be more effectively suppressed. [Explanation of symbols]

[0040] 1a non-consumable electrode 1b Welding wire (consumable electrode) 2 Work 3a Non-consumable electrode arc 3b consumable electrode arc 4 Plasma gas nozzle 5 Shielding gas nozzle 6 Power supply chip AD Welding condition indicator circuit Ad Welding status indicator signal FR feed speed setting circuit Fr feed speed setting signal Ia Non-consumable electrode welding current IAR Non-consumable electrode welding current setting circuit Iar Non-consumable electrode welding current setting signal Ib (Consumable electrode arc) welding current ICR Non-consumable electrode welding current control setting circuit Icr Non-consumable electrode welding current control setting signal ID Welding current detection circuit Id Welding current detection signal PSA Welding power source for non-consumable electrode arc PSB Consumable electrode arc welding power source RC robot controller Rc Movement control signal RN Robot SD Short circuit detection circuit Sd Short circuit detection signal Vb (Consumable electrode arc) welding voltage VD Welding voltage detection circuit Vd Welding voltage detection signal VR welding voltage setting circuit Vr Welding voltage setting signal WM feeder WT Welding Torch

Claims

1. 1. An additive manufacturing welding method for manufacturing a molded object by melting and solidifying a welding wire fed from a welding torch by arc welding to form a bead, and stacking the formed beads, comprising: The arc welding is a two-electrode arc welding formed from a leading consumable electrode arc and a trailing non-consumable electrode arc. The present invention relates to an additive manufacturing welding method.

2. calculating a value of a welding current of the non-consumable electrode arc using a function having as an input a welding wire feed speed of the consumable electrode arc; The method for additive manufacturing and welding according to claim 1 .

3. Detecting an indicator correlated with the stability of the welding state of the consumable electrode arc; Controlling the value of the welding current of the non-consumable electrode arc based on the index The additive manufacturing welding method according to claim 1 or 2.

4. The consumable electrode arc is a short-circuit transfer arc that repeats a short circuit period and an arc period, The indicator is detected based on at least one of a duration of the short circuit period, a duration of the arc period, and an occurrence of an arc interruption. The method for additive manufacturing and welding according to claim 3 .

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