JP2010253535A - Welding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve problems in which profiling control is required even under an unstable state of welding current immediately after the start of welding and in which high gain profiling control is required for moving to a regular aim position in a short time, for the purpose of dispensing with the need of correcting a welding starting position by a touch sensor. <P>SOLUTION: This is a welding method using an arc sensor, in which, in a first period after the start of welding, positional correction in a direction vertical to a weaving direction is not performed but only positional correction in a horizontal direction as the weaving direction is performed and in which, after a lapse of the first period, both positional corrections in the horizontal and the vertical direction are performed. Also, in a second period after the start of welding and of the arc sensor, positional correction is performed by computing the amount of positional correction using a gain higher than a preliminarily set normal gain. After a lapse of the second period, positional correction is performed by computing the amount of positional correction using the normal gain. Consequently, movement to a regular aim position is accomplished in a short time. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a weaving welding, and relates to a welding method using an arc sensor that performs position copying control.

  The principle of arc sensor scanning control in consumable electrode arc welding will be described with reference to FIGS.

  FIG. 1 shows a schematic configuration near the tip of a general welding torch. A welding wire 12 as a consumable electrode is supplied through a power supply tip 11 provided inside the nozzle 10 of the welding torch.

  A voltage (hereinafter referred to as “welding voltage”) is provided between the welding wire 12 and the base material 20 via a feeding point (not shown) in the feeding tip 11 (where the welding wire 12 and the feeding tip 11 are in contact). Is applied. Thereby, an arc 30 is generated between the base material 20 and the welding wire 12, and the base material 20 and the welding wire 12 are melted by the arc heat. Then, the welding wire 12 is continuously supplied, whereby the arc 30 is continued and welding is performed.

  Note that the length of the arc 30 is determined from the relationship between the welding voltage and the speed at which the welding wire 12 is supplied (hereinafter referred to as “wire feeding speed”). The length of the arc 30 determines the length of the welding wire 12 from the power feed tip 11 (more precisely, the power feed point) to the arc 30 (hereinafter referred to as “protrusion length”), and the resistance value therebetween determines this. The value of the flowing current (hereinafter referred to as “welding current”) is determined.

  FIG. 2 shows an example in which weaving, which is a reciprocating operation of the welding torch, is performed while maintaining the wire feed speed and the welding voltage substantially constant. In FIG. 2, a weaving operation (direction) is indicated by arrows in the left-right direction with respect to the paper surface. 2 shows an example in which the power supply tip 11 and the welding wire 12 shown at three locations in FIG. 2 are located at both ends of the weaving and at the center of the weaving.

  As the position of the welding wire 12 with respect to the joint in the base material 20 changes as shown in FIG. 2, the protrusion length changes. As a result, the welding current also changes. That is, as the protrusion length becomes shorter, the welding current increases, so the welding current increases at both ends of the weaving (positions E1 and E2 in FIG. 2), and the welding current decreases at the center of the weaving (position C in FIG. 2). Become. In this way, a change in the welding current synchronized with the weaving occurs.

  As shown in FIG. 2, when weaving is performed around the joint position, and when the weaving center (position C1 in FIG. 3) is slightly shifted from the joint position as shown in FIG. The change in the protrusion length with the operation is different, and as a result, the change pattern of the welding current is also different.

  In automatic scanning control of a weld line, it is a common practice to use the difference in the welding current change pattern that accompanies the difference in the protrusion length. The following prior arts are widely known as this type of method.

  In this prior art, the welding current change pattern when the weaving center and the joint position coincide as shown in FIG. 2 and the weaving center and the joint position do not coincide as shown in FIG. The fact that the welding current change pattern is different is used (for example, see Patent Document 1).

  That is, in copying in the weaving direction, the difference ΔIL between the maximum current value and the minimum current value during the stroke from one weaving end to the other weaving end, and the maximum current value and the minimum current value during the reverse stroke, It is determined which of the differences ΔIR is larger, which of the weaving centers is shifted in the weaving direction. Then, in every weaving half cycle, the position is corrected in the direction to cancel the deviation, and the weaving center is automatically copied to the joint position.

JP-A 61-144272

  In order to perform arc sensor control using the welding current change pattern, it is assumed that welding is performed in a state where the welding current is stable. However, the welding current gradually increases for a while after the start of welding, and it takes some time to stabilize. Therefore, the arc sensor cannot function until it is stabilized. Therefore, it is implicitly assumed that welding is started from a state where the welding start position is correctly at the joint position. In general, an arc sensor is often used for the purpose of following displacement of a joint position due to thermal strain generated during welding.

  In order to prevent the welding start position from deviating from the target weld joint, a method of “adjusting the welding start position using a touch sensor” is generally known. However, in order to perform this method, there is a problem that hardware and software for performing a touch sensor are required and the cost thereof is required. In addition, there is an operational problem that time for performing the sensing operation of the touch sensor is necessarily required before starting welding. For this reason, the user's desire to omit the touch sensor is great.

  However, when the touch sensor is omitted, it is not guaranteed that “the welding start position is correctly at the joint position”, and welding starts from a shifted position. At that time, it is required to quickly move to the correct welding position for the joint and perform welding by the control of the arc sensor. Here, the problem is that “the arc sensor does not function for a certain period of time after the start of welding”. It is necessary to eliminate this and make the scanning control of the arc sensor function in a short time after the start of welding.

  An object of this invention is to provide the welding method which solves the said subject.

  In order to solve the above problems, the welding method of the present invention is a welding method using an arc sensor that detects a deviation amount of a target position of welding based on a welding current when welding is performed by weaving a welding torch. In the first predetermined period after the start of welding, only the position correction in the horizontal direction that is the weaving direction is performed without performing the position correction in the vertical direction with respect to the weaving direction, and the first predetermined period is performed. After the elapse of time, both position correction in the horizontal direction and position correction in the vertical direction are performed.

  In addition to the above, the welding method of the present invention calculates the position correction amount by using a gain higher than a preset normal gain in the second predetermined period after starting welding, thereby correcting the position. After the elapse of the second predetermined period, the position correction amount is calculated using the normal gain to perform position correction.

  Further, in the welding method of the present invention, in addition to the above, the second predetermined period includes a first predetermined period, and the second predetermined period is longer than the first predetermined period. Is the method.

  According to the present invention, when the welding start position is deviated from the target welding position for the target welded joint, the welding torch can be moved to the desired welding target position in a short time after the start of welding. Can be shortened.

  Therefore, it is not necessary to use the touch sensor to adjust the welding start position, and the hardware and software costs for performing the touch sensor are not required, and the time for performing the touch sensor is not required, thereby increasing the tact time. It becomes possible.

Diagram showing the general vicinity of the tip of a general welding torch Diagram showing how weaving is performed around the joint position The figure which shows a mode that weaving is performed centering on the position shifted from the joint position The figure which shows the state where the distance between a welding torch and a base material became long Diagram showing the change in welding current when weaving is performed around the joint position The figure which shows the change of the welding current when weaving around the position shifted from the joint position The figure which shows the change of welding current when the distance of a welding torch and a base material becomes long. Diagram showing the change in welding current after the start of welding The figure which shows the operation | movement after the welding start in Embodiment 1 of this invention. The figure which shows the operation | movement after the welding start in Embodiment 2 of this invention.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to FIGS.

(Embodiment 1)
In the present embodiment, the same parts as those in FIGS. 1 to 3 described in the background art are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 2 is a diagram illustrating a state in which weaving is performed around the joint position. An example is shown in which weaving is performed between the position E1 and the position E2, with one end being a position E1 around the position C and the other end being a position E2.

  In FIG. 2, H indicates the position shift control direction in the weaving direction by the arc sensor of the present embodiment. V represents a position shift control direction perpendicular to the weaving direction (H direction). The arc sensor according to the present invention realizes copying by shifting the position in two directions, the H direction and the V direction. In FIG. 2, L is a weld line, which is a direction orthogonal to the paper surface.

  First, position shift control in the H direction will be described.

  As described in the background art, when weaving is performed around the joint position (position C) shown in FIG. 2 and when the weaving center (position C1) is slightly shifted from the joint position shown in FIG. The change in the protrusion length accompanying the weaving operation is different, and as a result, the welding current changes in different patterns. Then, focusing on the difference between the average welding current in the predetermined period near one weaving end and the average welding current in the predetermined period near the other weaving end (this is called “deviation welding current”), the weaving center position Deviation in the weaving direction with respect to the joint position of this causes a difference in deviation welding current.

  FIG. 5 schematically shows a change in welding current when weaving welding is performed in a state where the joint position and the weaving center coincide with each other as shown in FIG. FIG. 6 schematically shows a change in welding current when weaving welding is performed with the joint position and the weaving center shifted as shown in FIG. The difference between the average welding current in the predetermined period in the vicinity of the weaving end E1 in FIG. 5 and the average welding current in the predetermined period in the vicinity of the weaving end E2 is defined as a deviation welding current ΔIE, and in the predetermined period in the vicinity of the weaving end E11 in FIG. If the difference between the average welding current and the average welding current in the vicinity of the weaving end E21 in a predetermined period is the deviation welding current ΔIE1, there is a difference between the deviation welding current ΔIE and the deviation welding current ΔIE1.

  Here, the position shift control in the H direction by the arc sensor of the present embodiment repeatedly executes the following series of processes. In other words, the current deviation welding current is obtained with respect to the predetermined target deviation welding current and the last two consecutive weaving ends, the shift correction in the H direction is calculated from these, and the weaving center position is controlled using this. is there.

  For example, assuming that the state shown in FIG. 5 is the relationship between the target weaving center position and the joint position, the deviation welding current ΔIE is the target deviation welding current, and the relationship between the weaving center position and the joint position in the state shown in FIG. When applied to the control for the current state in FIG. 5, as shown in the following equation, the difference between the target deviation welding current ΔIE and the current deviation welding current ΔIE1 is multiplied by the H direction gain (coefficient) to correct the shift in the H direction. Determine the amount.

[ΔIE1-ΔIE] × H direction gain → H direction shift correction amount The H direction position control of the weaving center position is performed according to the H direction shift correction amount (movement distance and direction). Here, the H direction gain is a parameter for generating an H direction shift amount of the weaving center position in a direction to cancel the difference between the target deviation welding current and the current deviation welding current. The H direction gain is obtained in advance through experiments or the like, for example.

  Next, position shift control in the V direction (direction orthogonal to the weaving direction) will be described.

  FIG. 4 shows an example of a state in which the distance from the tip of the tip 11 to the weld line L is longer and the overall protrusion length is longer than in the state shown in FIG. As the protrusion length increases, the welding current decreases. Considering the average welding current, the state shown in FIG. 4 is lower than the case shown in FIG. FIG. 7 schematically shows a change in welding current in the state shown in FIG. When the average welding current IAV in a predetermined period in FIG. 5 showing the welding current in the state of FIG. 2 and the average welding current IAV2 in the predetermined period in FIG. 7 showing the welding current in the state of FIG. It differs from the current IAV2 depending on the protrusion length.

  The position shift control in the V direction by the arc sensor according to the present embodiment repeatedly executes the following series of processes. That is, the V-direction shift correction amount is calculated from the predetermined target average welding current and the average welding current for the most recent predetermined period, and using this, for example, the distance between the tip of the tip 11 and the weld line L of the joint is calculated. Take control. For example, when the state shown in FIG. 2 is set as the target state, the target average welding current is obtained by performing welding in the state shown in FIG. 2 and obtaining an average value of the welding current. And let this be a target average welding current.

  For example, what is shown in FIG. 5 is a change in the welding current in the case of the distance between the tip of the target tip 11 and the weld line L of the joint, and the average welding current IAV for the predetermined period is set as the target average welding current. 7, when applied to the control of the current state, which is the distance between the tip of the tip 11 and the weld line L of the joint, the current average welding current IAV2 and the current average welding current IAV2 are expressed by the following equations. Is multiplied by a V-direction gain (coefficient) to determine a V-direction shift correction amount.

[IAV2-IAV] × V direction gain → V direction shift correction amount The distance between the tip of the tip 11 and the weld line L of the joint is controlled according to the V direction shift correction amount (distance and direction). Specifically, for example, the position of the welding torch is changed by operating a robot holding the welding torch.

  Here, the V-direction gain is a V-direction shift amount for changing the distance between the tip of the tip 11 and the weld line L of the joint in a direction to cancel the difference between the target average welding current and the current average welding current. It is a parameter to generate.

  In the above, for convenience of explanation, the position shift control in the H direction and the position shift control in the V direction have been described separately, but in reality, the two controls work simultaneously and the shift control in the two directions is performed simultaneously.

  Further, in order to perform copying by shift control in two directions, it is ideal that the welding current is only a change due to the above-described content (deviation of the weaving center position) and is not changed by other factors. However, it takes time for the welding current to increase to the steady welding current (main welding current) immediately after the start of welding.

  FIG. 8 schematically shows the change over time in the average welding current from the start of welding until the welding current starts flowing until the steady welding current is reached.

  It is obvious that the position shift control in the V direction based on the average welding current for a predetermined period does not function during the period in which the average welding current at the beginning of welding gradually increases. That is, during the increase period of the average welding current, the average welding current is necessarily smaller than a predetermined target average welding current as a reference. Therefore, even if the distance between the tip of the tip 11 and the weld line L of the joint is a target distance, a difference from the reference target average welding current is generated. Even if they match, it is determined that they do not match. Therefore, position shift control in the V direction cannot be performed in a period in which the average welding current after the start of welding increases.

  On the other hand, since the position shift control in the H direction using the deviation welding current uses deviation, it is considered that it can function even if it is not sufficient.

  Therefore, if the average welding current at the beginning of welding gradually increases, only the shift correction in the H direction works, and the shift correction in the V direction does not work, only copying by the shift control in the H direction is performed. Can do. Note that the period during which the average welding current gradually increases can be obtained, for example, by experiments. Further, if the shift correction in the V direction is applied during the period when the average welding current at the beginning of welding is gradually increased, the distance between the tip of the tip 11 and the weld line L of the joint is controlled to be shortened. In the period in which the average welding current at the beginning is gradually increasing, it is necessary to prevent the shift correction in the V direction from working.

  Thus, in the welding method using the arc sensor in the present embodiment, the control in the H direction is executed only for the time specified after the start of welding. That is, as shown in FIG. 9, during the set time of “predetermined time 1” after the start of welding, only the shift correction in the H direction is performed, and copying is performed accordingly. After the elapse of the set time of “predetermined time 1”, not only the H direction but also the V direction shift correction is started, and normal copying is performed in which both the H direction and the V direction are corrected.

  As described above, according to the present embodiment, copying control to the joint position immediately after the start of welding is performed, and the influence at the time of gradually increasing the welding current can be avoided.

  In addition, as an apparatus which performs the welding method of this Embodiment, the following are mentioned, for example.

  A robot, a robot control device that controls the operation of the robot, a welding torch held by the robot, and a welding machine are provided. The robot control device or the welding machine is provided with a current detection unit, and the robot control device is provided with a calculation unit that performs calculation based on the detection result of the current detection unit. The calculation unit performs calculation of the average current, calculation of the difference between the target average current and the current average current, calculation of the shift amount, and the like. The robot control device controls the operation of the robot based on the calculation result of the calculation unit. In the robot control device, there is also provided a timer unit for measuring “predetermined period 1”.

(Embodiment 2)
In the present embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. The main difference from the first embodiment is that “initial gain” in the V direction and H direction different from the V direction gain and H direction gain (also referred to as “normal gain”) described in the first embodiment is provided, and welding is performed. The “predetermined period 2” after the start is that the shift correction amount is obtained using “initial gain” (coefficient) instead of “normal gain” (coefficient). Note that the “normal gain” and “initial gain” in the V direction and the H direction can be obtained by experiments or the like, for example.

  In the welding method using the arc sensor according to the present embodiment, the control that applies the “initial gain” different from the “normal gain” is executed for the specified time after the start of welding. The “initial gain” is larger than the “normal gain”.

  The control of this embodiment will be described with reference to FIG.

  For example, as shown in FIG. 10, “predetermined time 1” is a period during which only shift control in the H direction works as in the first embodiment. The “predetermined time 2” is a period in which the “initial gain” is used. The “predetermined time 2” is longer than the “predetermined time 1”. The “predetermined time 1” and the “predetermined time 2” are obtained in advance by, for example, experiments.

  Therefore, after the start of welding, first, during the “predetermined time 1”, shift control only in the H direction is performed using the initial gain in the H direction. When “predetermined time 1” elapses, shift control in two directions, H direction and V direction, is performed, and control is performed using an initial gain in the H direction and an initial gain in the V direction. When “predetermined time 2” elapses, shift control in two directions, H direction and V direction, is performed using the normal gain in the H direction and the normal gain in the V direction.

  As described above, according to the present embodiment, even when the weaving center is deviated from the weld line L at the start of welding, copying only in the H direction works immediately after the start of welding and is larger than the “normal gain”. By performing the shift control using the “initial gain”, the shift amount is larger than when using the “normal gain”, and the desired aim is achieved in a shorter time than when performing the shift control using the “normal gain”. Copying that moves to a position (on the weld line L) can be performed.

  And in the normal welding part after the weaving center which has shifted | deviated at the time of a welding start moves to the welding line L, normal stable follow-up is attained.

  Here, if the gain is too high, there may be a problem that the weld bead is disturbed. Therefore, in this embodiment, in order to move the weaving center shifted at the start of welding to the welding line L in a short time, control is performed using an “initial gain” that is larger than the “normal gain” immediately after the start of welding, After the weaving center moves to the welding line L, control is performed using a “normal gain” suitable for steady welding that is smaller than the “initial gain” in order not to cause problems such as disturbance of the weld bead.

  In this embodiment, the example in which the control is performed using the “initial gain” during the “predetermined time 2” has been described, but whether or not the “initial gain” is used may be selected. That is, it may be selected whether to perform the control of the first embodiment or the control of the second embodiment.

  Moreover, as a joint to which the welding method of Embodiment 1 or Embodiment 2 is applied, fillet, a V groove, an I groove having a gap, or the like can be given.

  According to the present invention, when the welding start position is deviated from the target welding position for the target welded joint, the welding torch can be moved to the desired welding target position in a short time after the start of welding, and the arc sensor is used. This is industrially useful as a welding method.

10 Nozzle 11 Tip 12 Welding wire 20 Base material 30 Arc C Position of weaving center C1 Position of weaving center E1 Position of one end of both ends of weaving E2 Position of the other end of both ends of weaving E11 Position of one end of both ends of weaving E21 Position of the other end of the weaving ends W Weaving surface L Weld line of the joint H Shift correction direction vector in the same direction as the weaving direction V Shift correction direction vector in a direction perpendicular to the weaving direction

Claims (3)

A welding method using an arc sensor that detects a deviation amount of a target position of welding based on a welding current when performing welding by weaving a welding torch,
In the first predetermined period after starting welding, only the position correction in the horizontal direction which is the weaving direction is performed without performing the position correction in the vertical direction with respect to the weaving direction,
A welding method that performs both the horizontal position correction and the vertical position correction after the first predetermined period. In the second predetermined period after starting welding, position correction is performed by calculating a position correction amount using a gain higher than a preset normal gain, and after the elapse of the second predetermined period, The welding method according to claim 1, wherein the position correction is performed by calculating a position correction amount using a normal gain. The welding method according to claim 2, wherein the second predetermined period includes a first predetermined period, and the second predetermined period is longer than the first predetermined period.

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