Control method of a welding device

Abstract

The forward feeding action is performed after the reverse feeding action of the welding wire (21) is performed. After the forward feeding action is started, a first current value (la') is detected at a first time (a'). A first time (Tab') from the first time (a') to a second time (b') is detected. After the second time (b') is passed, a second current value (Ic') is detected at a third time (c'). At least one of the first current value (la'), the second current value (Ic'), and the first time (Tab') is compared with a corresponding first set current value (la), a second set current value (Ic), and a first set time (Tab) set in advance, thereby judging the abnormality of the conduit cable (16).

Description

Technical Field

[0001] This invention relates to a control method for a welding apparatus. Background Technology

[0002] Patent document 1 discloses a wire feeding method for welding, in which optical sensors are installed on the extrusion side and the lead-out side to directly measure the wire feeding speed. By measuring and comparing the wire feeding conditions on the extrusion side and the lead-out side, poor wire feeding caused by the contact resistance inside the conduit cable is detected.

[0003] Patent Document 1: Japanese Patent Publication No. 09-295141 Summary of the Invention

[0004] -The technical problem the invention aims to solve-

[0005] However, in existing inventions, in order to detect poor wire feeding, it is necessary to set up an optical sensor on the extrusion side and an optical sensor on the lead-out side, which increases the overall cost of the device.

[0006] This invention was made in view of this purpose, and its objective is to enable the identification of abnormalities in conduit cables with a relatively simple structure.

[0007] -Technical solutions for solving technical problems-

[0008] The first aspect relates to a control method for a welding apparatus, the welding apparatus including a welding torch, a conduit cable connected to the welding torch and guiding a welding wire, and a feed motor for feeding the welding wire through the conduit cable. The control method for the welding apparatus includes the steps of: performing a forward feed action to feed the welding wire after a reverse feed action of pulling in the welding wire; detecting a first current value Ia' flowing through the feed motor at a first moment a' after the start of the forward feed action, where the increase in the torque of the feed motor is below a predetermined value; and detecting the current value Ia' flowing from the first moment a' to after the first moment a'. The steps include: a first time Tab' up to a second time b' when the increase in torque of the feed motor reaches a predetermined value; a third time c' after the second time b', detecting a second current value Ic' flowing through the feed motor; and a step of comparing at least one of the first current value Ia', the second current value Ic', and the first time Tab' with a pre-set corresponding first set current value Ia, second set current value Ic, and first set time Tab to determine whether the conduit cable has malfunctioned.

[0009] In the first aspect, a forward feed is performed after a reverse feed of the welding wire. After the forward feed begins, a first current value Ia' is detected at a first time a'. A first time Tab' from the first time a' to the second time b' is detected. After the second time b', a second current value Ic' is detected at a third time c'. At least one of the first current value Ia', the second current value Ic', and the first time Tab' is compared with a pre-set corresponding first set current value Ia, second set current value Ic, and first set time Tab to determine an abnormality in the conduit cable.

[0010] In this way, by detecting the current flowing through the feed motor and the elapsed time at various moments determined by the increase in torque of the feed motor, abnormalities in the conduit cable can be determined. Therefore, there is no need to install additional sensors for detecting poor wire feed, thus suppressing cost increases.

[0011] Secondly, based on the first aspect, if Tab′ < Tab × α (α is a specified coefficient), it is determined that the conduit cable has malfunctioned.

[0012] In the second aspect, if the first time Tab' is shorter than the first set time Tab, it can be determined that the conduit cable is bent or broken, or that the welding wire is blocked in the middle of the conduit cable.

[0013] The third aspect, based on the first aspect, is that under the conditions of Tab' = Tab × α, Ia' = Ia × β, and Ic' > Ic × γ (α, β, and γ are specified coefficients), it is determined that the conduit cable has malfunctioned.

[0014] In the third aspect, if the second current value Ic' is higher than the second set current value Ic, it can be determined that the welding wire is blocked on the welding torch side, that is, at the top of the conduit cable.

[0015] The fourth aspect, based on the first aspect, is that under the conditions that Tab' = Tab × α, Ia' > Ia × β, and Ic' > Ic × γ (α, β, and γ are specified coefficients), it is determined that the conduit cable has malfunctioned.

[0016] In the fourth aspect, if the first current value Ia' is higher than the first set current value Ia, it can be determined that the welding wire is blocked at the root of the feed motor side, i.e., the conduit cable.

[0017] -The Effects of the Invention-

[0018] According to the technical solution disclosed herein, abnormalities in conduit cables can be determined with a relatively simple structure. Attached Figure Description

[0019] Figure 1 This is a diagram showing the overall structure of the welding apparatus according to this embodiment;

[0020] Figure 2 This is a diagram used to illustrate the position of the welding wire inside the conduit cable at the end of the reverse feed;

[0021] Figure 3 This is a diagram used to illustrate the position of the welding wire inside the conduit cable at the end of the forward feed;

[0022] Figure 4 It is a graph showing the change of motor current over time when the conduit cable is in a normal state;

[0023] Figure 5 It is a graph showing the change of feed speed of the conduit cable over time under normal conditions;

[0024] Figure 6 This is a flowchart used to determine abnormalities in conduit cables;

[0025] Figure 7 It is a graph showing the change of motor current over time when welding wire blockage occurs midway through the conduit cable;

[0026] Figure 8 It is a graph showing the change of motor current over time when the welding wire is blocked at the top of the conduit cable;

[0027] Figure 9 This is a graph showing the change of motor current over time when welding wire blockage occurs at the root of the conduit cable. Detailed Implementation

[0028] The embodiments of the present invention will now be described with reference to the accompanying drawings. It should be noted that the following description of preferred embodiments is merely illustrative and is not intended to limit the scope of the invention, its application, or its uses.

[0029] like Figure 1 As shown, the welding apparatus 1 includes a welding torch 10, a welding torch cable 15, a feed device 20, a gas supply unit 25, and a power supply unit 30. The welding apparatus 1 performs arc welding on the workpiece W.

[0030] The welding torch 10 is connected to the feed device 20 via the welding torch cable 15. The welding torch 10 feeds the welding wire 21 from the feed device 20 to the workpiece W.

[0031] The welding torch cable 15 has a conduit cable 16 and a gas hose (not shown). A welding wire 21 is inserted into the conduit cable 16. The conduit cable 16 guides the welding wire 21 to the welding torch 10. The gas hose of the welding torch cable 15 is connected to the gas hose 26 of the gas supply unit 25.

[0032] The gas supply unit 25 is connected to the feed device 20 via the gas hose 26. The protective gas supplied from the gas supply unit 25 flows inside the gas hose of the conduit cable 16 and is sprayed from the tip of the welding torch 10 toward the workpiece W.

[0033] The feeding device 20 includes a welding wire 21 and a feeding motor 22. The welding wire 21 is wound on a welding wire spool (not shown). The feeding motor 22 feeds the welding wire 21 by driving a feed roller (not shown) to rotate. The feeding device 20 sends a signal indicating the motor current value of the feeding motor 22 to the power supply device 30 via the motor current signal line 5.

[0034] The feed device 20 switches between forward and reverse feed actions by changing the rotation direction of the feed motor 22. In the forward feed action, the welding wire 21 is fed from the feed device 20 to the welding torch 10. In the reverse feed action, the welding wire 21 is pulled from the welding torch 10 into the feed device 20.

[0035] The power supply unit 30 includes a power supply unit 31, a welding control unit 32, an arithmetic unit 33, a storage unit 34, and a display unit 35.

[0036] The power supply unit 31 supplies power to the feed device 20 via the power cable 7. The power supply unit 31 applies voltage to the workpiece W via the base material cable 8. A positive voltage is applied to the welding wire 21. A negative voltage is applied to the workpiece W. As a result, an arc discharge is generated between the tip of the welding wire 21 and the workpiece W, thereby performing arc welding.

[0037] The welding control unit 32 controls the operation of the feed device 20. The welding control unit 32 sends a feed command to the feed device 20 via the control signal line 6. The feed device 20 feeds the welding wire 21 by controlling the feed motor 22 at the indicated command speed.

[0038] The calculation unit 33 receives a signal representing the motor current value sent from the feed device 20 via the motor current signal line 5. Details will be described later. The calculation unit 33 compares the first current value Ia', the second current value Ic', and the first time Tab' detected during the feeding of the welding wire 21 with preset first set current values ​​Ia, second set current values ​​Ic, and first set time Tab. Based on the comparison results, the calculation unit 33 determines whether an abnormality has occurred in the conduit cable 16. The calculation results of the calculation unit 33 are stored in the storage unit 34.

[0039] The storage unit 34 stores data representing various welding conditions, including welding current and welding voltage values. Various parameters, such as a first set current value Ia, a second set current value Ic, and a first set time Tab, are pre-stored in the storage unit 34.

[0040] Display unit 35 displays specified information. For example, display unit 35 displays the welding current value and welding voltage value during the arc welding process. In addition, display unit 35 displays warning information indicating that an abnormality has occurred in the conduit cable 16.

[0041] However, when performing arc welding using the welding apparatus 1, the welding torch 10 needs to be moved to various positions and angles. Therefore, the conduit cable 16 inside the welding torch cable 15 repeatedly bends in various directions and curvatures. As a result, the conduit cable 16 itself sometimes bends or breaks.

[0042] In addition, sometimes due to prolonged use of the welding device 1, a portion of the welding wire 21 may be cut off during the feeding process and accumulate inside the conduit cable 16, causing blockage inside the conduit cable 16.

[0043] In this way, when abnormalities such as breakage or blockage of the conduit cable 16 occur, the feed rate of the welding wire 21 will become unstable, resulting in unstable arc welding and welding defects.

[0044] Therefore, in this embodiment, by determining whether the conduit cable 16 is abnormal, it is possible to appropriately determine when to replace or maintain the conduit cable 16.

[0045] <Changes in motor current under normal conditions in conduit cables>

[0046] like Figure 2 and Figure 3 As shown, in the case of abnormal diagnosis of conduit cable 16, firstly, the feed motor 22 performs a reverse feed action to pull in the welding wire 21, and then performs a forward feed action to send out the welding wire 21.

[0047] Specifically, with the welding torch cable 15 wound once, the total length of the welding wire 21 inside the conduit cable 16 differs at the end of the reverse feed and the end of the forward feed. Figure 2 At the end of the reverse feed, welding wire 21 is laid along the inner circumferential surface of the coil portion of the conduit cable 16. Figure 3 When the forward feed ends, welding wire 21 is laid along the outer circumference of the coil portion of the conduit cable 16.

[0048] Here, regarding the total length of the welding wire 21 within the conduit cable 16, it is shorter at the end of the reverse feed than at the end of the forward feed. When from the state at the end of the reverse feed (refer to...) Figure 2 When the forward feed begins, until the state at the end of the forward feed is reached (see reference). Figure 3 Until then, the welding wire 21 will not protrude from the welding torch 10.

[0049] Therefore, before the feed device 20 starts the forward feed action, the timing of the protrusion of the welding wire 21 is different depending on whether it is in the state at the end of the reverse feed or the state at the end of the forward feed.

[0050] Therefore, in this embodiment, when performing anomaly diagnosis on the conduit cable 16, it is first brought to the state where reverse feed has ended (see reference). Figure 2 Then proceed with the forward feed action.

[0051] Figure 4 This is a graph showing the change of motor current over time when the conduit cable 16 is in a normal state. It should be noted that... Figure 4 The values ​​shown in the graph are obtained under the assumption that the welding torch cable 15 is bent one turn at φ600mm.

[0052] like Figure 4 As shown, the moment when the forward feed action begins after the feed motor 22 has performed a reverse feed action is set to 0. After the forward feed action begins, current is applied to the feed motor 22 in a manner that the welding wire 21 is fed at a constant speed (see reference). Figure 5 (solid line).

[0053] The power supply unit 30 sends a signal indicating the current value applied to the feed motor 22 via the motor current signal line 5. The calculation unit 33 calculates the change of motor current over time. At the first moment a when the change of motor current is constant, the calculation unit 33 determines that the increase in torque of the feed motor 22 is below a predetermined value.

[0054] For example, if the change in motor current per unit time is below a specified threshold (2.5 A / sec), it is determined that the increase in torque of the feed motor 22 is below a specified value. The period from the start of the forward feed action of the feed motor 22 to the first moment a is the transition period for reaching any feed speed.

[0055] The feed device 20 detects the first current value Ia flowing through the feed motor 22 at the first moment a.

[0056] The calculation unit 33 determines, at the second time b after the motor current begins to increase from the first time a, that the increase in torque of the feed motor 22 has reached or exceeded a predetermined value. The calculation unit 33 detects the first time Tab from the first time a to the second time b.

[0057] After the second moment b, at the third moment c when the welding wire 21 protrudes from the top of the welding torch 10, the feed device 20 detects the second current value Ic flowing through the feed motor 22.

[0058] like Figure 5As shown by the dashed line, during the period from the second time b to the third time c, the feed speed of the welding wire 21 at the tip of the welding torch 10 gradually increases. The period from the second time b to the third time c is the period during which the welding wire 21 begins to protrude from the tip of the welding torch 10, and the wire feeding speed at the tip of the welding torch 10 continuously approaches the commanded feed speed (the feed speed of the feed motor 22).

[0059] At the third moment c, the commanded feed rate is consistent with the wire feeding rate at the tip of the welding torch 10. After the third moment c, the feed rate of the welding wire 21 is maintained at the feed rate command value given to the feeding device 20.

[0060] Here, as Figure 4 As shown, the reason for the inflection points at the first moment a and the second moment b is that after the feed motor 22 performs a reverse feed action, it performs a forward feed action, thus creating a clearance before the welding wire 21 protrudes from the tip of the welding torch 10. In other words, from the start of the forward feed action of the feed motor 22 until the second moment b, the welding wire 21 does not protrude from the tip of the welding torch 10; the period from the first moment a to the second moment b is the clearance absorption period within the conduit cable 16.

[0061] Therefore, as Figure 4 As shown by the dashed line, when the feed motor 22 does not perform a reverse feed action, there is no turning point at the first moment a and the second moment b, and the motor current rises to the second current value Ic.

[0062] The first current value Ia detected when the conduit cable 16 is in a normal state is stored in the storage unit 34 as the first set current value Ia. The second current value Ic is stored in the storage unit 34 as the second set current value Ic. The first time Tab is stored in the storage unit 34 as the first set time Tab.

[0063] In the event of wire blockage occurring midway through the conduit cable,

[0064] like Figure 6 As shown, in step S11, the feeding device 20 performs a forward feeding action after performing a reverse feeding action.

[0065] In step S12, after the feed device 20 starts the forward feed action, at the first moment a' when the increase in torque of the feed motor 22 becomes below a predetermined value, the first current value Ia' flowing through the feed motor 22 is detected.

[0066] In step S13, the first time Tab' is detected from the first time a' to the second time b' when the increase in torque of the feed motor 22 after the first time a' becomes above a predetermined value.

[0067] In step S14, after the second time b', at the third time c' when the welding wire 21 protrudes from the top of the welding torch 10, the second current value Ic' flowing through the feed motor 22 is detected.

[0068] In steps S15 to S17, at least one of the first current value Ia', the second current value Ic', and the first time Tab' is compared with the corresponding preset first set current value Ia, the second set current value Ic, and the first set time Tab to determine whether the conduit cable 16 has an abnormality.

[0069] exist Figure 7 In the diagram, solid lines represent the changes in motor current value when the conduit cable 16 is in a normal state, and dashed lines represent the measured values ​​of motor current when diagnosing abnormalities in the conduit cable 16.

[0070] exist Figure 7 In the example shown, if the first current value Ia' is compared with the first set current value Ia, then Ia' = Ia.

[0071] If we compare the first time Tab' with the first set time Tab, then Tab' < Tab. It should be noted that the first set time Tab, which serves as the threshold for determining anomalies in the conduit cable 16, is preferably set to a shorter time than the first set time Tab detected when the conduit cable 16 is in a normal state, multiplied by a predetermined coefficient α. Specifically, it is preferable that when α = 0.8, the first set time Tab = Tab × 0.8. It should be noted that the predetermined coefficient α is only one example and can be arbitrarily set.

[0072] exist Figure 7 In the example shown, the condition Tab' < Tab × α is met in the abnormal diagnosis of conduit cable 16 (in Figure 6 (In step S15, it is marked "Yes"). That is to say, the timing of the motor current increase is earlier than when the conduit cable 16 is in a normal state.

[0073] Therefore, in Figure 7 In the example shown, it can be determined that the conduit cable 16 was bent or broken, and that the welding wire 21 became blocked midway through the conduit cable 16. Figure 6 (Step S18). Then, simply display a warning message indicating that an abnormality has occurred in the conduit cable 16 on the display unit 35.

[0074] <In the event of wire blockage at the tip of the conduit cable>

[0075] exist Figure 6 If "No" is selected in step S15, proceed to step S16.

[0076] exist Figure 8 In the example shown, if the first current value Ia' and the first set current value Ia are compared, then Ia' = Ia. It should be noted that the first set current value Ia, which serves as the threshold for determining abnormalities in the conduit cable 16, is preferably set as follows: to flexibly accommodate different application ranges, it is preferable to use the first set current value Ia detected when the conduit cable 16 is in a normal state as a reference, multiplied by a predetermined coefficient β, thereby setting it within ±20% of the current value in the normal state. Specifically, it is preferable that when β is set to the range of 0.8 to 1.2, the first set current value Ia = Ia × 0.8 to 1.2.

[0077] If we compare the first time Tab' and the first set time Tab, then Tab' = Tab. It should be noted that the first set time Tab, which serves as the threshold for determining anomalies in the conduit cable 16, is preferably set as follows: to flexibly accommodate different application ranges, it is preferable to use the first set time Tab detected when the conduit cable 16 is in a normal state as a reference, multiplied by a predetermined coefficient α, thereby setting it within ±20% of the normal state time. Specifically, it is preferable that when α is set to the range of 0.8 to 1.2, the first set time Tab = Tab × 0.8 to 1.2.

[0078] If the second current value Ic' and the second set current value Ic are compared, then Ic' > Ic. It should be noted that the second set current value Ic, which serves as the threshold for determining abnormalities in the conduit cable 16, is preferably a value larger than the second set current value Ic detected when the conduit cable 16 is in a normal state, multiplied by a predetermined coefficient γ. Specifically, it is preferable that when γ = 1.7, the second set current value Ic = Ic × 1.7.

[0079] It should be noted that the specified values ​​of coefficients α, β, and γ are only one example and can be set arbitrarily.

[0080] exist Figure 8 In the example shown, in the abnormal diagnosis of conduit cable 16, the conditions Tab' = Tab × α, Ia' = Ia × β, and Ic' > Ic × γ are met (in Figure 6 In step S16, the setting is "Yes". That is, compared to the normal state of the conduit cable 16, the motor current value increases when the welding wire 21 protrudes from the tip of the welding torch 10. Therefore, it can be determined that the welding wire 21 is blocked on the welding torch 10 side, i.e., at the tip of the conduit cable 16. Figure 6 Step S18).

[0081] <In the case of wire blockage at the root of the conduit cable>

[0082] exist Figure 6If "No" is selected in step S16, proceed to step S17.

[0083] exist Figure 9 In the example shown, if the first current value Ia' and the first set current value Ia are compared, then Ia' > Ia. It should be noted that the first set current value Ia, which serves as the threshold for determining anomalies in the conduit cable 16, is preferably a value larger than the first set current value Ia detected when the conduit cable 16 is in a normal state, multiplied by a predetermined coefficient β. Specifically, it is preferable that when β = 1.7, the first set current value Ia = Ia × 1.7.

[0084] If we compare the first time Tab' and the first set time Tab, then Tab' = Tab. It should be noted that the first set time Tab, which serves as the threshold for determining anomalies in the conduit cable 16, is preferably set as follows: to flexibly accommodate different application ranges, it is preferable to use the first set time Tab detected when the conduit cable 16 is in a normal state as a reference, multiplied by a predetermined coefficient α, thereby setting it within ±20% of the normal state time. Specifically, it is preferable that when α is set to the range of 0.8 to 1.2, the first set time Tab = Tab × 0.8 to 1.2.

[0085] If the second current value Ic' and the second set current value Ic are compared, then Ic' > Ic. It should be noted that the second set current value Ic, which serves as the threshold for determining abnormalities in the conduit cable 16, is preferably a value larger than the second set current value Ic detected when the conduit cable 16 is in a normal state, multiplied by a predetermined coefficient γ. Specifically, it is preferable that when γ = 1.7, the second set current value Ic = Ic × 1.7.

[0086] It should be noted that the specified values ​​of coefficients α, β, and γ are only one example and can be set arbitrarily.

[0087] exist Figure 9 In the example shown, in the abnormal diagnosis of conduit cable 16, the conditions Tab' = Tab × α, Ia' > Ia × β, and Ic' > Ic × γ are met (in Figure 6 In step S17, the value is "Yes". That is, compared to when the conduit cable 16 is in a normal state, the motor current value when the welding wire 21 is fed from the feed device 20 is higher. Therefore, it can be determined that the welding wire 21 is blocked on the feed motor 22 side, i.e., at the root of the conduit cable 16. Figure 6 Step S18).

[0088] It should be noted that, in Figure 6 If "No" is found in step S17, the conduit cable 16 is determined to be normal (step S19), and the process ends.

[0089] -Effects of this implementation method-

[0090] As described above, by employing the control method of the welding apparatus 1 according to this embodiment, at each moment determined based on the increase in torque of the feed motor 22, the abnormality of the conduit cable 16 can be determined by detecting the current value flowing through the feed motor 22 and the elapsed time. Therefore, there is no need to separately install sensors for detecting poor feed of the welding wire 21, thus suppressing cost increases.

[0091] Furthermore, by comparing at least one of the first current value Ia', the second current value Ic', and the first time Tab' with a pre-set corresponding first set current value Ia, second set current value Ic, and first set time Tab, it is possible to estimate at which location of the conduit cable 16 the abnormality occurred. This allows for a reduction in maintenance time.

[0092] -Industry Applicability-

[0093] As described above, the present invention achieves the effect of being able to determine the abnormality of conduit cables with a relatively simple structure, which is highly practical and therefore very useful and has high industrial applicability.

[0094] -Symbol Explanation-

[0095] 1 Welding equipment

[0096] 10 Welding torches

[0097] 16 Conduit Cable

[0098] 20 Feed device

[0099] 21 Welding wire

[0100] 22 feed motors

[0101] 32 Welding Control Department

[0102] 33. Arithmetic Unit

[0103] 34. Storage Department.

Claims

1. A control method for a welding apparatus, the welding apparatus comprising a welding torch, a conduit cable connected to the welding torch and guiding a welding wire, and a feed motor for feeding the welding wire through the conduit cable, characterized in that: The control method for the welding apparatus includes: After performing the reverse feed action of pulling in the welding wire, the forward feed action of feeding out the welding wire is performed. After the forward feed action begins, at the first moment a' when the increase in torque of the feed motor becomes below a predetermined value, a step is taken to detect the first current value Ia' flowing through the feed motor; The step of detecting the first time Tab' from the first time a' until the second time b' after the first time a' when the increase in torque of the feed motor becomes above a predetermined value; After the second time b', at the third time c', when the welding wire protrudes from the tip of the welding torch and the wire feeding speed at the tip of the welding torch matches the commanded feed speed of the feed motor, the step of detecting the second current value Ic' flowing through the feed motor; and The step of comparing at least one of the first current value Ia', the second current value Ic', and the first time Tab' with a pre-set corresponding first set current value Ia, second set current value Ic, and first set time Tab to determine whether the conduit cable has experienced an abnormality.

2. The control method for the welding apparatus according to claim 1, characterized in that: If Tab' < Tab × α, it is determined that the conduit cable has malfunctioned, where α is a specified coefficient.

3. The control method for the welding apparatus according to claim 1, characterized in that: When Tab' = Tab × α, Ia' = Ia × β, and Ic' > Ic × γ, it is determined that the conduit cable has malfunctioned, where α, β, and γ are specified coefficients.

4. The control method for the welding apparatus according to claim 1, characterized in that: If Tab' = Tab × α, Ia' > Ia × β, and Ic' > Ic × γ, it is determined that the conduit cable has malfunctioned, where α, β, and γ are specified coefficients.

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