Wire feeding system and wire feeding method

Abstract

To provide a wire feeding system which can shorten tact time to improve welding quality.SOLUTION: A wire feeding system comprises: a wire feeding part 10 that feeds a welding wire 4; and a wire feeding control part 16 that controls the wire feeding part 10 so that forward and reverse feeding by which forward feeding that feeds the welding wire 4 in a forward direction and reverse feeding that feeds the welding wire 4 in the opposite direction are repeated alternately. The wire feeding control part 16 controls the wire feeding part 10 so that the welding wire 4 is fed in the forward and reverse directions while keeping on applying voltages for generating arc, at least in order to increase respective peak speeds at the time of the forward feeding and at the time of the reverse feeding or to lengthen respective duration time of the forward feeding and the reverse feeding which are repeated alternately, in a period of time of slow-down feeding processing at the time when arc starts.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a wire feeding system and a wire feeding method. [Background technology]

[0002] When arc welding is performed, slag is generated and may adhere to the end of the welding wire or the base metal. If slag adheres to the end of the welding wire, an arc cannot be generated between the welding wire and the base metal, which causes delays in the welding work.

[0003] The following Patent Document 1 discloses a welding method for performing a slag removal process in which slag is removed by repeatedly moving a welding wire back and forth at high speed toward a workpiece, which is a base material. In this welding method, the slag removal process is performed by moving the welding wire back and forth at high speed at a constant frequency. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5230600 Summary of the Invention [Problem to be solved by the invention]

[0005] In the welding method described in Patent Document 1, the welding wire is moved back and forth at high speed at a constant frequency, so depending on the frequency set, the slag may not be completely destroyed, which may increase the tact time. In addition, depending on the frequency set, the base material may be scratched, which may cause a decrease in welding quality.

[0006] Therefore, an object of the present invention is to provide a wire feeding system and a wire feeding method that can shorten the tact time and improve welding quality. [Means for solving the problem]

[0007] 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 to perform forward and reverse feeding that alternately repeats forward feeding, in which the welding wire is fed in a forward direction, and reverse feeding, in which the welding wire is fed in a reverse direction. The wire feeding control unit controls the wire feeding unit to feed the welding wire in forward and reverse directions while a voltage for generating an arc is continuously applied during a period of slow-down feeding processing at the start of an arc, and at least controls the wire feeding unit so that the peak speed during forward feeding and reverse feeding are increased and so that the duration of each of the alternating forward and reverse feeds is lengthened.

[0008] According to this aspect, during the slow-down feed process at the start of an arc, the welding wire is fed in both forward and reverse directions, and the peak speed during forward feed and reverse feed can be gradually increased, or the duration of each of the forward feed and reverse feed can be gradually increased. Therefore, even if slag is present between the welding wire and the base metal, for example, the slag can be destroyed or removed during the slow-down feed process.

[0009] In the above aspect, the welding apparatus may further include a memory unit that stores an arc history regarding the success or failure of the arc for each section of arc welding, and the wire feed control unit may change at least either the degree to which the peak speed is increased or the degree to which the duration is extended based on the stored arc history.

[0010] According to this aspect, it is possible to specify a section of arc welding where an arc has failed in the past, and to change the degree to which the peak speed is increased during forward feed and reverse feed and the degree to which the duration of forward feed and reverse feed is increased depending on the severity of the failure. Therefore, it is possible to specify a welding section where slag is likely to be present, and perform a different forward and reverse feed for each specified welding section, thereby making it possible to efficiently destroy and remove slag.

[0011] In the above aspect, the arc history includes the number of times that an arc fails to be generated or the percentage of times that an arc fails to be generated, and when the number of times exceeds a predetermined number or the percentage exceeds a predetermined percentage, the wire feed control unit may at least either increase the peak speed to a degree greater than a currently set degree and increase the duration to a degree greater than a currently set degree in the peak speed and duration in the slow-down feed processing of the corresponding arc welding section.

[0012] According to this aspect, different forward and reverse feed can be performed for each section of arc welding depending on the number and rate of arc generation failures, thereby making it possible to further improve the efficiency of slag destruction and removal.

[0013] In the above aspect, the predetermined number of times and the predetermined ratio may be set and changed for each section of arc welding.

[0014] According to this aspect, the threshold number of times and the threshold ratio can be set and changed for each section of arc welding, making it possible to flexibly respond to sections where slag is likely to be present.

[0015] A wire feeding method according to another aspect of the present invention is a wire feeding method executed in a wire feeding system that feeds a welding wire, the wire feeding method including: a feeding step of feeding the welding wire; and a control step of controlling the feeding of the welding wire in the feeding step so as to perform forward and reverse feeding that alternately repeats forward feeding, in which the welding wire is fed in a forward direction, and reverse feeding, in which the welding wire is fed in a reverse direction. The control step controls the feeding of the welding wire in the feeding step by feeding the welding wire in forward and reverse directions while a voltage for generating an arc is continuously applied during a period of a slow-down feeding process at the time of arc start, so as to at least increase the peak speed during forward feeding and reverse feeding, and to lengthen the duration of each of the alternately repeated forward feeding and reverse feeding.

[0016] According to this aspect, during the slow-down feed process at the start of an arc, the welding wire is fed in both forward and reverse directions, and the peak speed during forward feed and reverse feed can be gradually increased, or the duration of each of the forward feed and reverse feed can be gradually increased. Therefore, even if slag is present between the welding wire and the base metal, for example, the slag can be destroyed or removed during the slow-down feed process. Effect of the Invention

[0017] According to the present invention, it is possible to provide a wire feeding system and a wire feeding method that can shorten the tact time and improve the welding quality. [Brief description of the drawings]

[0018] [Figure 1] 1 is a block diagram illustrating a schematic configuration of a wire feeding system according to an embodiment; [Diagram 2] 11 is a timing chart for explaining an example of changing peak speeds and durations in forward feed and reverse feed. [Diagram 3] 4 is a flowchart for explaining an example of a wire feeding method according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described with reference to the accompanying drawings, in which like reference numerals denote like or similar structures.

[0020] FIG. 1 is a block diagram illustrating a schematic configuration of a wire feeding system according to the present invention. The wire feeding system 1 is a system that feeds a welding wire 4 wound around a wire reel 2 to a welding torch 3 that performs arc welding. The wire feeding system 1 includes, for example, a wire feeding unit 10, a control unit 15, and a storage unit 18. Note that the wire feeding unit 10, the control unit 15, and the storage unit 18 do not need to be included in the same device. For example, they may be distributed and included in a wire feeding device including the wire feeding unit 10, a control device including the control unit 15, and a storage device including the storage unit 18. The storage unit 18 stores, for example, arc history information 19. The arc history information 19 stores, for example, history information related to arc welding.

[0021] The wire feeder 10 includes a first wire feeder 11, a wire buffer 12, and a second wire feeder 13. Each part of the wire feeder 10 will be described in detail below.

[0022] The first wire feeder 11 feeds the welding wire 4 wound around the wire reel 2 toward the welding torch 3. The first wire feeder 11 has, 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 rotational position of the motor, etc. The forward movement of the welding wire 4 means that the welding wire 4 moves in the direction of the welding torch 3 (hereinafter also referred to as the "forward direction"), and the backward movement of the welding wire 4 means that the welding wire 4 moves in the direction of the wire reel 2 (hereinafter also referred to as the "reverse direction").

[0023] The motor of first wire feeder 11 rotates a roller so that welding wire 4 moves in the forward or reverse direction according to an instruction from control unit 15. Exemplarily, first wire feeder 11 feeds welding wire 4 in the forward direction according to an instruction from control unit 15 during welding.

[0024] The second wire feeder 13 feeds the welding wire 4 stored in a wire buffer 12 (described later) to the welding torch 3. The second wire feeder 13 has, for example, a roller, a motor, and an encoder, similar to the above-described first wire feeder 11. Since the roller, motor, and encoder are similar to those of the first wire feeder 11, description thereof will be omitted here.

[0025] For example, when welding, the second wire feeder 13 feeds the welding wire 4 to the welding torch 3 by performing forward and reverse feeding in which the welding wire 4 is fed in the forward direction and the reverse feeding in which the welding wire 4 is fed in the reverse direction alternately and repeatedly at high speed in accordance with instructions from the control unit 15.

[0026] Wire buffer 12 is provided between first wire feeder 11 and second wire feeder 13. Wire buffer 12 stores welding wire 4 fed by first wire feeder 11 and passes the stored welding wire 4 to second wire feeder 13. The amount of welding wire 4 stored in wire buffer 12 (hereinafter also referred to as "buffer amount") varies based on the amount of welding wire 4 fed in the forward direction by first wire feeder 11 and the amount of welding wire 4 fed in the forward direction by second wire feeder 13.

[0027] For example, when the amount of welding wire 4 fed in the forward direction by first wire feeder 11 is greater than the amount of welding wire 4 fed in the forward direction by second wire feeder 13, the buffer amount increases. On the other hand, when the amount of welding wire 4 fed in the forward direction by first wire feeder 11 is less than the amount of welding wire 4 fed in the forward direction by second wire feeder 13, the buffer amount decreases.

[0028] Such an increase or decrease in the buffer amount is converted into the length of the welding wire 4, and the buffer amount can be expressed as the length of the welding wire 4 accommodated in the wire buffer 12 by adding or subtracting from a reference length.

[0029] The control unit 15 shown in Fig. 1 is physically configured by a control unit including, for example, a processor, a memory (storage device), and a communication interface. The control unit 15 realizes, for example, a function as the wire feed control unit 16 shown in Fig. 1 by the processor executing a predetermined program stored in the memory.

[0030] Wire feed control unit 16 controls first wire feeder 11 and second wire feeder 13. Specifically, wire feed control unit 16 outputs a feed command value to first wire feeder 11 and second wire feeder 13. The feed command value may include, for example, a feed speed or a value for calculating the feed speed. First wire feeder 11 and second wire feeder 13 perform forward feed or forward / reverse feed at a feed speed corresponding to the feed command value.

[0031] The wire feed control unit 16 controls, for example, the execution of a slow-down feed process. The slow-down feed process is a process included in an arc start process executed before starting a welding process, and specifically, after a welding start command, the welding wire 4 is fed at a slow-down feed speed slower than the feed speed during steady welding, with a predetermined time as the upper limit, to generate an arc. In the slow-down feed process in this embodiment, for example, the welding wire 4 is fed while being fed forward and backward. The forward and reverse feed executed in the slow-down feed process is executed in a state in which a voltage for generating an arc is continuously applied. The voltage for generating an arc is output by, for example, a welding power source unit (not shown) that may be included in the wire feed system 1. The welding power source unit may be provided separately and distributed as a welding power source device. The upper limit time and the slow-down feed speed for executing the slow-down feed process can be set in advance as welding conditions.

[0032] The slow-down feed process ends when an arc occurs, or when the upper limit time for executing the slow-down feed process has elapsed without an arc occurring. Whether an arc has occurred can be determined by monitoring the welding current. This is because an arc occurs when the welding wire 4 fed toward the base metal is short-circuited with the base metal and a welding current flows.

[0033] By performing the slow-down feeding process while feeding the welding wire 4 in the forward and reverse directions, even if there is a foreign object such as slag between the welding wire 4 and the base metal that prevents the generation of an arc, it is possible to destroy the slag during the slow-down feeding process. If the slag can be destroyed or removed, an arc can be generated between the welding wire 4 and the base metal, and welding can be started.

[0034] Here, the presence of slag or the like between the welding wire 4 and the base material corresponds to, for example, a case where slag or the like is attached to the end of the welding wire 4 or a case where slag or the like is attached to the surface of the base material. There are various situations of adhesion of slag or the like, depending on, for example, the degree of adhesion and the size of the slag or the like. Under such a situation, if forward and reverse feeding is performed at a constant frequency as in Patent Document 1, depending on the frequency set, the slag may not be completely destroyed or the base material may be damaged. Therefore, in the wire feeding system 1 according to the present embodiment, it is decided to vary the forward and reverse feeding movement performed in the slow-down feeding process.

[0035] When feeding the welding wire 4 forward and backward in the slow-down feeding process, the wire feed control unit 16 performs at least one of the following (1) and (2).

[0036] (1) The wire feeding section 10 is controlled so that the peak speeds during forward feeding and reverse feeding are increased during the above-mentioned period. The peak speeds do not necessarily have to be increased compared to the previous peak speeds during forward feeding and reverse feeding, and may remain the same, but it is preferable that the peak speeds gradually increase throughout the above-mentioned period.

[0037] (2) The wire feeder 10 is controlled so that the duration of each of the alternately repeated forward feed and reverse feed is increased during the above-mentioned period. The duration does not necessarily have to be longer than the duration of each of the previous forward feed and reverse feed, and may remain the same, but it is preferable that the duration gradually increases throughout the above-mentioned period.

[0038] In this way, by gradually increasing or lengthening the peak speed and duration in the forward and reverse feed, the accuracy of breaking and removing slag, etc. can be improved. Therefore, it is possible to reduce the number of places where welding is not performed due to the presence of slag, etc., and it is possible to shorten the tact time.

[0039] In addition, at the start of the slow-down feeding process, forward and reverse feeding is performed with the peak speed and duration suppressed, and if the state where the slag, etc. is not removed and no arc is generated continues thereafter, the peak speed can be gradually increased and the duration can be gradually lengthened. Therefore, the impact on the base metal due to forward and reverse feeding can be suppressed, and the welding quality can be improved.

[0040] Next, referring to FIG. 2, an example of changing the peak velocity and duration in forward and reverse feed will be described.

[0041] 2 is a timing chart showing the change over time in the feed speed in second wire feeder 13. The vertical axis shows the feed speed, and the horizontal axis shows time.

[0042] At time t0, the slow-down feed process at the start of an arc starts, and the welding wire 4 is fed in both directions toward the base metal W. Thereafter, at time t13, an arc is generated, the slow-down feed process ends, and the welding process starts. In both the slow-down feed process and the subsequent welding process, forward and reverse feed is performed, but the peak speeds and durations are different. The respective peak speeds and durations can be preset as welding conditions.

[0043] 2, normal feeding is performed in the periods from time t0 to t1, from time t2 to t3, from time t4 to t5, from time t6 to t7, from time t8 to t9, from time t10 to t11, and from time t12 to t13. The length of time corresponding to each period is the duration of each normal feeding, and the maximum speed (normal) in each period is the peak speed during each normal feeding.

[0044] Similarly, in the slow-down feed process, reverse feed is performed in the periods from time t1 to t2, from time t3 to t4, from time t5 to t6, from time t7 to t8, from time t9 to t10, from time t11 to t12, and from time t13 to t14. The length of time corresponding to each period is the duration of each reverse feed, and the maximum speed (negative) in each period is the peak speed during each reverse feed.

[0045] In the figure, the peak speeds during each forward feed from time t0 to time t3 are set to the same magnitude, the peak speeds during each forward feed from time t4 to time t7 are set to be larger than the previous period and to be the same magnitude, and the peak speeds during each forward feed from time t8 to time t13 are set to be larger than the previous period and to be the same magnitude. In other words, the peak speeds during forward feed are set to gradually increase throughout the period of the slow-down feed process. The peak speeds during reverse feed are also set in the same way as the peak speeds during forward feed.

[0046] In addition, the duration of each forward feed from time t0 to time t9 is set to the same length, and the duration of each forward feed from time t10 to t13 is set to be longer than the previous period and to be the same length. In other words, the duration of each repeated forward feed is set to gradually become longer throughout the period of the slow-down feed process. The duration of each reverse feed is also set to the same length as the duration of each forward feed.

[0047] Next, an example of a procedure in the wire feeding method according to the embodiment will be described with reference to Fig. 3. This procedure begins, for example, when a slow-down feeding process is started in an arc start process.

[0048] First, wire feed control unit 16 outputs a feed command value to second wire feeder 13 to feed welding wire 4 forward and backward at a slow-down feed speed (step S101).

[0049] Next, the wire feed control unit 16 controls the second wire feed unit 13 based on, for example, preset welding conditions so that the peak speed during forward feed and reverse feed gradually increases and the duration of each of the alternating forward feed and reverse feed gradually increases (step S102).

[0050] Next, the control unit 15 judges whether or not an arc has occurred (step S103). If this judgment is NO (step S103; NO), the control unit 15 returns the process to the above step S101.

[0051] In the above step S103, when it is determined that an arc has occurred (step S103; YES), the control unit 15 performs arc welding (step S104), and ends this procedure.

[0052] The procedure also ends if the upper limit time for executing the slow-down feeding process has elapsed without generating an arc.

[0053] As described above, according to the wire feeding system 1 in the embodiment, during the period in which the slow-down feeding process is being performed at the time of arc start, the welding wire 4 can be fed in both forward and reverse directions, and the peak speed during each of the forward feeding and reverse feeding can be gradually increased, or the duration of each of the forward feeding and reverse feeding can be gradually increased. Therefore, even if slag S or the like is present between the welding wire 4 and the base material W, it is possible to destroy or remove the slag S during the slow-down feeding process.

[0054] This makes it possible to reduce the number of areas where welding is not performed due to the presence of slag S, etc., and to suppress the impact on the base material W caused by forward and reverse feed.

[0055] Therefore, according to the wire feeding system 1 of the embodiment, it is possible to shorten the tact time and improve the welding quality.

[0056] [Variations] The above-described embodiment is intended to facilitate understanding of the present invention, and is not intended to limit the present invention. The elements of the embodiment, as well as their arrangement, materials, conditions, shapes, sizes, etc., are not limited to those exemplified, and may be modified as appropriate. For example, the following modified examples 1 and 2 may be used.

[0057] [Variation 1] In the above-described embodiment, forward and reverse feeding is performed in the slow-down feeding process, but the present invention is not limited to this. The welding wire 4 may be forward fed at the start of the slow-down feeding process, and forward and reverse feeding may be performed when it is detected that no arc is generated. For example, a situation in which it is detected that no arc is generated corresponds to a situation in which slag or the like is interposed between the welding wire 4 and the base material. For example, the following (1) to (3) can be used as conditions for determining that slag or the like is interposed between the welding wire 4 and the base material.

[0058] (1) The load current of the motor of the second wire feeder 13 exceeds a predetermined current value. (2) The error between the feed command to second wire feeder 13 and the response value in second wire feeder 13 exceeds a predetermined threshold value. (3) The amount of buffer stored in the wire buffer 12 exceeds a predetermined amount.

[0059] [Variation 2] In the above-described embodiment, the peak speed and duration in the slow-down feed process are changed based on the preset welding conditions, but the method of changing them is not limited to this. For example, the degree to which the peak speed is increased and the degree to which the duration is extended may be changed based on the arc history information 19 stored in the memory unit 18.

[0060] Arc history information 19 stores history information about arc welding for each section of arc welding. The history information about arc welding includes, for example, the number of times an arc generation failure occurred and the ratio of times an arc generation failure occurred.

[0061] When the number of times that an arc fails to be generated exceeds a predetermined number, or when the rate at which an arc fails to be generated exceeds a predetermined rate, the wire feed control unit 16 implements at least one of the following (1) and (2) for the peak speed and duration in the slow-down feed process of the corresponding arc welding section.

[0062] (1) Increase the peak speed by a degree greater than the currently set degree. (2) Increase the duration by a degree greater than the degree currently set.

[0063] The predetermined number of times and the predetermined ratio can be set and changed for each section of arc welding. The predetermined number of times and the predetermined ratio may be set in a plurality of stages. [Explanation of symbols]

[0064] REFERENCE SIGNS LIST 1...wire feeding system, 2...wire reel, 3...welding torch, 4...welding wire, 10...wire feeding section, 11...first wire feeding section, 12...wire buffer, 13...second wire feeding section, 15...control section, 16...wire feeding control section, 18...storage section, 19...arc history information

Claims

1. a wire feeder that feeds a welding wire; a wire feed control unit that controls the wire feed unit so as to perform forward and reverse feeding that alternately repeats forward feeding in which the welding wire is fed in a forward direction and reverse feeding in which the welding wire is fed in a reverse direction; Equipped with the wire feed control unit controls the wire feed unit in such a manner that, during a period of a slow-down feed process at the time of an arc start, the welding wire is fed in the forward and reverse directions while a voltage for generating an arc is continuously applied, and at least a peak speed during the forward feed and a peak speed during the reverse feed are increased over time, and a duration of each of the alternately repeated forward feed and reverse feed is increased over time. Wire feeding system.

2. A memory unit that stores an arc history regarding the success or failure of an arc for each section of arc welding, The wire feed control unit changes at least one of a degree of increasing the peak speed and a degree of increasing the duration based on the stored arc history. The wire feeding system of claim 1 .

3. The arc history includes a number of failures to strike an arc or a percentage of failures to strike an arc, When the number of times exceeds a predetermined number of times or when the ratio exceeds a predetermined ratio, the wire feed control unit at least performs one of the following with respect to the peak speed and the duration in the slow-down feed process of the corresponding arc welding section: increasing the degree of increase of the peak speed to a value greater than a currently set value and increasing the degree of increase of the duration to a value greater than a currently set value. The wire feeding system of claim 2.

4. The predetermined number of times and the predetermined ratio are set and changeable for each section of the arc welding. The wire feeding system of claim 3.

5. 1. A wire feeding method performed in a wire feeding system for feeding a welding wire, comprising: a feeding step of feeding the welding wire; a control step of controlling feeding of the welding wire in the feeding step so as to perform forward and reverse feeding, which alternately repeats forward feeding in which the welding wire is fed in a forward direction and reverse feeding in which the welding wire is fed in a reverse direction; Including, the control step controls the feeding of the welding wire in the feeding step in such a way that, during a period of a slow-down feeding process at the time of an arc start, the welding wire is fed in the forward and reverse directions while a voltage for generating an arc is continuously applied, and at least a peak speed during the forward feeding and a peak speed during the reverse feeding are increased over time, and a duration of each of the alternately repeated forward feeding and reverse feeding is increased over time. Wire feeding method.

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