Wire feeding system

Abstract

To provide a wire feeding system which can improve efficiency of slag removal.SOLUTION: A wire feeding system 1 comprises: a wire feeding part 10 for feeding a welding wire 4; and a wire feeding control part 16 that causes the welding wire 4 to approach a base material while performing normal and reverse feeding for alternatively repeating normal feeding for feeding the welding wire 4 in a normal direction and reverse feeding for feeding the welding wire 4 in a reverse direction at the time of arc start, and controls the wire feeding part 10 so that feeding control amounts for normal feeding and reverse feeding become coincident with each other until arc occurs after detection of contact between the welding wire 4 and the base material. The wire feeding control part 16 controls the wire feeding part 10 so that the welding wire 4 during the normal feeding contacts the base material when being fed at a peak speed when performing the control so that the feeding control amount are coincident.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a wire feeding system.

Background Art

[0002] When arc welding is performed, slag is generated and may adhere to the end of the welding wire or the base material. When slag adheres to the end of the welding wire or the like, an arc cannot be generated between the welding wire and the base material, which becomes a factor causing a delay in the welding operation.

[0003] Patent Document 1 below discloses a slag removal process that removes slag by repeatedly moving a welding wire back and forth at high speed toward a workpiece as the base material in the ignition process. In this slag removal process, the welding wire is fed forward by a certain path length and then fed backward by a smaller path length, so that the welding wire approaches the base material while moving back and forth at high speed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the slag removal process of Patent Document 1, after starting the process, when the first contact between the welding wire and the base material is detected by the motor current monitoring unit, it is possible to change the path length of the welding wire fed forward to the path length of the previous backward feed.

[0006] However, in order to efficiently perform slag removal, it is not sufficient to simply move the welding wire back and forth at high speed depending on the path length of the backward feed immediately before contact, and there is room for improvement.

[0007] Therefore, one of the objectives of the present invention is to provide a wire feeding system that can improve the efficiency of slag removal. [Means for solving the problem]

[0008] A wire feeding system according to one aspect of the present invention includes a wire feeding unit that feeds a welding wire, and a wire feeding control unit that controls the wire feeding unit so that the feeding control amount for forward feeding and reverse feeding matches from the time contact between the welding wire and the base material is detected until an arc is generated, while performing forward and reverse feeding, which alternately feeds the welding wire in the forward direction and feeds the welding wire in the reverse direction at the start of the arc. The wire feeding control unit controls the wire feeding unit so that the welding wire contacts the base material when it is being fed at its peak speed during forward feeding.

[0009] According to this embodiment, while feeding the welding wire in both forward and reverse directions at arc start, the welding wire is brought close to the base material, and from the time contact between the welding wire and the base material is detected until the arc is generated, the welding wire is fed at peak speed and can be kept in contact with the base material. This makes it possible to strike the welding wire against the base material with the greatest possible energy.

[0010] In the above embodiment, when the wire feeding control unit controls the wire feeding amount to match, it may control the wire feeding unit such that the feeding error, which is the difference between the feeding command value output to the wire feeding unit and the feeding response value to the feeding command value, exceeds a threshold value set based on the feeding error when the welding wire contacts the base material at peak speed.

[0011] According to this embodiment, it is possible to repeatedly strike the base material with a welding wire at peak speed from the time contact is detected until an arc is generated.

[0012] In the above embodiment, when the wire feeding control unit controls the feeding control amount to match, it may control the feeding control amount such that the feeding error falls between a threshold and another threshold that is greater than the said threshold.

[0013] According to this embodiment, when the welding wire at peak speed is struck against the base material from the time contact is detected until an arc is generated, it is possible to strike the base material within a range that does not damage it.

[0014] In the above embodiment, the wire feeding unit includes a first wire feeding unit for feeding welding wire, a wire buffer for accommodating the welding wire fed by the first wire feeding unit, and a second wire feeding unit for feeding the welding wire accommodating the wire buffer to the welding torch. The wire feeding control unit may stop the feeding of the welding wire by the first wire feeding unit when contact between the welding wire and the base material is detected.

[0015] According to this embodiment, when contact between the welding wire and the base material is detected, the feeding of the welding wire by the first wire feeding unit can be stopped, thereby preventing the amount of welding wire contained in the wire buffer from exceeding a specified amount.

[0016] In the above embodiment, a detection unit may be further provided that detects contact between the welding wire and the base material when the accumulated value of the feeding error for each cycle of forward and reverse feeding reaches a predetermined value.

[0017] According to this embodiment, contact between the welding wire and the base material can be detected based on a value obtained by accumulating the feeding error, thereby improving the accuracy of contact detection.

[0018] In the above embodiment, the feeding error may be the error between a first feeding speed corresponding to the feeding command value and a second feeding speed corresponding to the feeding response value.

[0019] According to this embodiment, the forward and reverse feeding of the wire by the wire feeding unit can be controlled by the feeding speed.

Effect of the Invention

[0020] According to the present invention, it is possible to provide a wire feeding system capable of improving the efficiency of slag removal.

Brief Description of the Drawings

[0021] [Figure 1] It is a block diagram illustrating a schematic configuration of a wire feeding system according to an embodiment. <​​​​​​​​​​​​​​​​​​​​​​​The first wire feeding unit 11 feeds the welding wire 4 wound on the wire reel 2 toward the welding torch 3. The first wire feeding unit 11 includes, for example, a roller (not shown) that moves the welding wire 4 forward or backward, a motor (not shown) that rotates the roller, and an encoder (not shown) that detects the rotation position of the motor, etc. Moving the welding wire 4 forward means that the welding wire 4 moves toward the welding torch 3 (hereinafter also referred to as the "forward direction"), and moving the welding wire 4 backward means that the welding wire 4 moves toward the wire reel 2 (hereinafter also referred to as the "reverse direction").

[0026] The motor of the first wire feeding unit 11 rotates the rollers so that the welding wire 4 moves in the forward or reverse direction, according to instructions from the control unit 15. For example, when welding, the first wire feeding unit 11 feeds the welding wire 4 in the forward direction, according to instructions from the control unit 15.

[0027] The second wire feeding unit 13 feeds the welding wire 4, which is housed in the wire buffer 12 (described later), to the welding torch 3. The second wire feeding unit 13, like the first wire feeding unit 11 described above, includes, for example, rollers, a motor, and an encoder. Since the rollers, motor, and encoder are the same as those in the first wire feeding unit 11, their description is omitted here.

[0028] For example, when welding, the second wire feeding unit 13 feeds the welding wire 4 to the welding torch 3 by performing forward feeding, which alternates at high speed between feeding the welding wire 4 in the forward direction, and feeding the welding wire 4 in the reverse direction, in accordance with instructions from the control unit 15.

[0029] The wire buffer 12 is provided between the first wire feeding unit 11 and the second wire feeding unit 13, and stores the welding wire 4 fed by the first wire feeding unit 11 and passes the stored welding wire 4 to the second wire feeding unit 13. The amount of welding wire 4 stored in the wire buffer 12 (hereinafter also referred to as the "buffer amount") fluctuates based on the amount of welding wire 4 fed in the forward direction by the first wire feeding unit 11 and the amount of welding wire 4 fed in the forward direction by the second wire feeding unit 13.

[0030] For example, the buffer amount increases when the amount of welding wire 4 fed in the forward direction by the first wire feeding unit 11 is greater than the amount of welding wire 4 fed in the forward direction by the second wire feeding unit 13. On the other hand, the buffer amount decreases when the amount of welding wire 4 fed in the forward direction by the first wire feeding unit 11 is less than the amount of welding wire 4 fed in the forward direction by the second wire feeding unit 13.

[0031] By converting such increases or decreases in buffer volume into the length of the welding wire 4 and adding or subtracting it from the standard length, the buffer volume can be expressed as the length of the welding wire 4 contained in the wire buffer 12.

[0032] The control unit 15 shown in Figure 1 is physically composed of a control unit including, for example, a processor, memory (storage device), and a communication interface. The control unit 15 realizes the functions of, for example, the wire feeding control unit 16 and the detection unit 17 shown in Figure 1 by having the processor execute a predetermined program stored in memory.

[0033] The wire feeding control unit 16 controls the wire feeding unit 10, which includes a first wire feeding unit 11 and a second wire feeding unit 13. Specifically, the wire feeding control unit 16 outputs a feeding command value to the first wire feeding unit 11 and the second wire feeding unit 13. The feeding command value may include, for example, the feeding speed, or it may include a value for calculating the feeding speed. The first wire feeding unit 11 and the second wire feeding unit 13 will perform forward feeding or forward / reverse feeding at the feeding speed corresponding to the feeding command value.

[0034] The wire feeding control unit 16 controls, for example, the execution of the arc start process. The arc start process is performed before the welding process begins. Specifically, the arc start process is performed after the welding start command, by feeding the welding wire 4 in the forward direction at a slowdown feeding speed that is slower than the feeding speed during steady-state welding, up to a predetermined upper limit of time, in order to generate an arc. In the arc start process in this embodiment, the welding wire 4 is fed while being fed in both forward and reverse directions, as an example.

[0035] The forward and reverse wire feeding performed during the arc start process is carried out while a voltage for generating the arc is continuously applied. The voltage for generating the arc is output by a welding power supply unit (not shown), which can be included in the wire feeding system 1, for example. The welding power supply unit may be provided separately as a welding power supply device. The upper limit time for performing the arc start process and the slowdown feeding speed can be set in advance as welding conditions, for example.

[0036] The arc start process ends when an arc is generated, or when the maximum time limit for performing the arc start process has elapsed without an arc being generated. Whether or not an arc has been generated can be determined by monitoring the welding current. This is because an arc is generated when the welding wire 4 fed towards the base metal short-circuits with the base metal, causing a welding current to flow.

[0037] By performing the arc start process while feeding the welding wire 4 in both forward and reverse directions, even if foreign matter such as slag that hinders arc generation is present between the welding wire 4 and the base material, it becomes possible to destroy or remove the slag during the arc start process. If the slag can be destroyed or removed, an arc can be generated between the welding wire 4 and the base material, and welding can be started.

[0038] Here, the presence of slag between the welding wire 4 and the base material occurs, for example, when slag adheres to the end of the welding wire 4 or when slag adheres to the surface of the base material. There can be various situations in which slag adheres, depending on the degree of adhesion and the size of the slag.

[0039] Under these circumstances, as described in Patent Document 1, simply moving the welding wire back and forth at high speed based on the path length of the backward feed just before contact with the base material when the welding wire and base material first come into contact may not be able to efficiently break up or remove the slag. Therefore, in the wire feeding system 1 according to this embodiment, after detecting contact between the welding wire 4 and the base material, the system is controlled so that the welding wire 4 makes contact with the base material when it is being fed at its peak speed during forward feeding. Details of this control are described below.

[0040] In this embodiment, the wire feeding control unit 16 controls the wire feeding unit 10 so that the feeding control amount for forward feeding and reverse feeding matches from the time of arc start when the welding wire 4 is brought close to the base material while feeding in both forward and reverse directions, until the arc is generated. Preferably, the feeding control amount is calculated using, for example, the feeding speed of the welding wire 4, the feeding time of the welding wire 4, or the amount of welding wire 4 fed.

[0041] Specifically, when the wire feeding control unit 16 controls the wire feeding control amount to match that for forward feeding and reverse feeding, it controls the wire feeding unit 10 so that the welding wire 4 contacts the base material when it is being fed at its peak speed during forward feeding. By bringing the welding wire into contact with the base material at its peak speed, it becomes possible to strike the welding wire against the base material with the greatest possible energy.

[0042] To achieve such contact, it is preferable that the wire feeding control unit 16 controls the wire feeding unit 10 such that the error between the feeding command value output to the wire feeding unit 10 and the feeding response value to that feeding command value (hereinafter also referred to as the "feeding error") exceeds a preset threshold (hereinafter also referred to as the "first threshold").

[0043] The first threshold can be set based on the feeding error when the welding wire 4 contacts the base material at peak speed. For example, it is preferable to set the first threshold within a range that can be calculated as the feeding error when the welding wire 4 contacts the base material at peak speed.

[0044] Furthermore, in addition to the first threshold, a threshold larger than the first threshold (hereinafter also referred to as the "second threshold") may be set, and the feed control amount for forward and reverse feed may be controlled so that the feed error falls between the first threshold and the second threshold. Preferably, the second threshold is set within a range that can be calculated as the feed error when the welding wire 4 contacts the base material at peak speed, and within a range that does not damage the base material.

[0045] The feeding speed corresponding to the feeding response value can be calculated, for example, based on the position information detected by the encoder of the second wire feeding unit 13 and the feeding time.

[0046] Here, the detection unit 17 shown in Figure 1 is responsible for detecting contact between the welding wire 4 and the base material. The detection unit 17 detects contact between the welding wire 4 and the base material, for example, when the feeding error exceeds a third threshold (a predetermined value). The third threshold, like the first threshold, can be set based on the feeding error when the welding wire 4 contacts the base material at peak speed, but it may be a different value from the first threshold or the same value. For example, it is preferable to set the third threshold as the smallest possible feeding error among the feeding errors that can be calculated when the welding wire 4 contacts the base material, while reliably determining that the welding wire 4 is in contact with the base material.

[0047] Referring to Figure 2, an example of the process for controlling the feeding of the welding wire 4 during arc start in this embodiment will be described.

[0048] In a normal arc-starting process, an arc is generated before the welding wire 4 first contacts the base metal W at time t1 in Figure 2. However, if, for example, slag or other debris is present between the welding wire 4 and the base metal W, the arc will not be generated, and the welding wire 4 will contact the base metal W. This is a state of arc-starting failure. Therefore, the process illustrated in Figure 2 is a process included in the arc-starting process, which involves removing the slag or other debris after the initial arc-starting fails, and then generating the arc.

[0049] Figure 2(A) is a chart showing the time change of the feeding speed corresponding to the feeding command value output from the wire feeding control unit 16 to the second wire feeding unit 13. Figure 2(B) is a chart showing the time change of the feeding speed corresponding to the feeding response value for the feeding command value in Figure 2(A). Figure 2(C) is a chart showing the time change of the average speed of the feeding speed in Figure 2(A), and Figure 2(D) is a chart showing the time change of the feeding error, which is the difference between the feeding speed in Figure 2(A) and the feeding speed in Figure 2(B).

[0050] As shown in Figure 2(A), the feeding time required for forward and reverse feeding in each feeding cycle is the same, and from time t0 to time t4, the peak speed of forward feeding is faster than the peak speed of reverse feeding. As a result, the welding wire 4 approaches the base material W while being fed in both forward and reverse directions.

[0051] Furthermore, as shown in Figure 2(A), after time t4, the feeding time required for forward and reverse feeding remains the same, while the peak speeds of forward and reverse feeding are adjusted to be the same. As a result, the average feeding speed shown in Figure 2(C) changes from a positive speed to 0 after time t4.

[0052] At times t1, t2, and t3, when the welding wire 4 comes into contact with the base material W, its forward movement is obstructed and it stops, so the feeding speed corresponding to the feeding response value shown in Figure 2(B) becomes 0. As a result, feeding errors shown in Figure 2(D) occur at times t1, t2, and t3 and beyond.

[0053] At time t4, if the feeding error shown in Figure 2(D) exceeds the third threshold, the detection unit 17 detects contact between the welding wire 4 and the base material W. When contact is detected by the detection unit 17, the wire feeding control unit 16 controls the wire feeding unit 10 so that the feeding control amount for forward feeding and reverse feeding matches. In this process, as shown in Figure 2(A), the peak speed during reverse feeding after time t4 is changed to the same speed as the peak speed during forward feeding.

[0054] The method for matching the feed control amounts for forward and reverse feed is not limited to the above. For example, the peak speed during forward feed may be changed to the same speed as the peak speed during reverse feed. Alternatively, the feed time for at least one of forward or reverse feed may be changed to match the feed amount during forward feed with the feed amount during reverse feed.

[0055] This process will continue to run from time t4 until an arc occurs, or until the maximum time limit for executing the arc start process has elapsed without an arc occurring.

[0056] Next, with reference to Figure 3, an example of a procedure for controlling the feeding of the welding wire 4 in this embodiment will be described. This procedure begins, for example, with the start of the arc start process.

[0057] First, the wire feeding control unit 16 outputs a feeding command value to the second wire feeding unit 13, causing the welding wire 4 to be fed in forward or reverse directions (step S101).

[0058] Next, the control unit 15 determines whether or not an arc has been generated (step S102). If this determination is YES (step S102; YES), the control unit 15 performs arc welding (step S107) and terminates this procedure.

[0059] In step S102, if it is determined that no arc has occurred (step S102; NO), the detection unit 17 determines whether or not contact between the welding wire 4 and the base material has been detected (step S103). If this determination is NO (step S103; NO), the determination in steps S102 and S103 is repeated while forward and reverse feeding continues.

[0060] In step S103, if it is determined that contact between the welding wire 4 and the base material has been detected (step S103; YES), the wire feeding control unit 16 controls the wire feeding unit 10 so that the feeding control amounts for forward feeding and reverse feeding match (step S104).

[0061] Next, the control unit 15 determines whether or not an arc has occurred (step S105), and if no arc has occurred (step S105; NO), it determines whether or not the upper limit time for executing the arc start process has elapsed (step S106). If it determines that the upper limit time has not elapsed (step S106; NO), it continues forward and reverse feeding and repeats the determinations in steps S105 and S106.

[0062] In step S105, if it is determined that an arc has occurred (step S105; YES), the control unit 15 performs arc welding (step S107) and terminates this procedure.

[0063] Furthermore, if it is determined in step S106 that the maximum time limit has elapsed (step S106; YES), this procedure will also terminate.

[0064] As described above, according to the wire feeding system 1 in the embodiment, while feeding the welding wire 4 in both forward and reverse directions at arc start, the welding wire 4 is brought close to the base material, and from the time contact between the welding wire 4 and the base material is detected until the arc is generated, the welding wire 4, which is being fed at peak speed, is repeatedly brought into contact with the base material. This makes it possible to repeatedly execute the process of striking the welding wire 4 against the base material with the greatest energy from the time contact is detected until the arc is generated.

[0065] Therefore, according to the wire feeding system 1 in the embodiment, it is possible to improve the efficiency of slag removal.

[0066] [Differentiation] The embodiments described above are provided to facilitate understanding of the present invention and are not intended to limit its interpretation. The elements of the embodiments, as well as their arrangement, materials, conditions, shapes, and sizes, are not limited to those exemplified and can be modified as appropriate.

[0067] For example, in the embodiment described above, the detection unit 17 detects contact between the welding wire 4 and the base material when the feeding error exceeds a third threshold, but the conditions for detecting contact between the welding wire 4 and the base material are not limited to this. For example, contact between the welding wire 4 and the base material may be detected when it is first detected, or contact between the welding wire 4 and the base material may be detected when it has been detected a predetermined number of times (two or more times).

[0068] Alternatively, contact between the welding wire 4 and the base material may be detected when the cumulative value of the feeding error for each cycle of forward and reverse feeding reaches a predetermined value. Preferably, the predetermined value is set to be as small as possible, for example, from the cumulative value of the feeding error calculated when the welding wire 4 contacts the base material, while still allowing for reliable determination that the welding wire 4 is in contact with the base material.

[0069] Furthermore, in the above-described embodiment, when the detection unit 17 detects contact between the welding wire 4 and the base material, the wire feeding control unit 16 may stop the feeding of the welding wire 4 by the first wire feeding unit 11. When the welding wire 4 comes into contact with the base material, its forward movement is blocked and it stops, so the amount of welding wire 4 contained in the wire buffer 12 increases due to the feeding of the welding wire 4 by the first wire feeding unit 11. Therefore, by stopping the feeding of the welding wire 4 by the first wire feeding unit 11 when contact between the welding wire 4 and the base material is detected, it is possible to prevent the amount of welding wire 4 contained in the wire buffer 12 from increasing too much beyond the specified limit. [Explanation of symbols]

[0070] 1...Wire feeding system, 2...Wire reel, 3...Welding torch, 4...Welding wire, 10...Wire feeding unit, 11...First wire feeding unit, 12...Wire buffer, 13...Second wire feeding unit, 15...Control unit, 16...Wire feeding control unit, 17...Detection unit

Claims

1. A wire feeding unit that feeds welding wire, During arc start, the wire feeding control unit controls the wire feeding section so that the feed control amounts for the forward feeding and the reverse feeding are the same, while alternately feeding the welding wire in the forward direction and feeding the welding wire in the reverse direction, while bringing the welding wire close to the base material, and from the time contact between the welding wire and the base material is detected until the arc is generated. Equipped with, The wire feeding control unit controls the wire feeding unit so that the amount of wire feeding matches the amount of wire feeding, and so that the welding wire during forward feeding contacts the base material when it is being fed at its peak speed. Wire feeding system.

2. The wire feeding control unit controls the wire feeding unit so that the feeding error, which is the difference between the feeding command value output to the wire feeding unit and the feeding response value to the feeding command value, exceeds a threshold value set based on the feeding error when the welding wire contacts the base material at peak speed, when controlling the amount of feeding control to match. The wire feeding system according to claim 1.

3. The wire feeding control unit controls the feeding control amount to match the feeding control amount, such that the feeding error falls between the threshold and another threshold that is greater than the threshold. The wire feeding system according to claim 2.

4. The wire feeding unit includes a first wire feeding unit for feeding the welding wire, a wire buffer for receiving the welding wire fed by the first wire feeding unit, and a second wire feeding unit for feeding the welding wire received in the wire buffer to the welding torch. The wire feeding control unit stops the feeding of the welding wire by the first wire feeding unit when contact between the welding wire and the base material is detected. The wire feeding system according to claim 1.

5. The system further includes a detection unit that detects contact between the welding wire and the base material when the accumulated value of the feeding error for each cycle of forward and reverse feeding reaches a predetermined value. The wire feeding system according to claim 2.

6. The feeding error is the error between the first feeding speed corresponding to the feeding command value and the second feeding speed corresponding to the feeding response value. The wire feeding system according to claim 2.

Images