JP2014113607A - Arc start method and welding system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an arc start method capable of excellently maintaining a generation state of an arc over a long period, by restraining an advance of unsharpening of the electrode tip of a welding torch by contact with a welding object in an arc start.SOLUTION: A welding system for executing the arc start of a touch start system, executes operation for contacting with an apex part 14c of a tip part 14a of an electrode 14 by inclining the electrode 14 at (an angle α°) to a surface Ma of the welding object M when contacting the tip part 14a of the electrode 14 of the welding torch 13 with the surface Ma of the welding object M.

Description

  The present invention relates to a welding system including a welding robot and a non-consumable electrode type arc welder, and more particularly to an arc start method thereof.

  As an arc start method in non-consumable electrode type arc welding such as TIG welding, a high frequency start method, a touch start method, and the like are known. The high frequency start method is a method in which a high frequency voltage of several thousand volts is applied between the electrode of the welding torch and the workpiece, and the initial arc is generated without contacting the electrode of the welding torch with the workpiece.

  On the other hand, in the touch start method, an initial arc is generated by bringing the welding torch electrode into contact (touch) with the welding torch while the no-load voltage is applied between the welding torch electrode and the workpiece and then pulling them apart. It is a method to make it. The arc start method by the touch start is disclosed in, for example, Patent Documents 1 to 3 and the like.

JP-A-53-95155 JP-A-55-54271 JP 2000-176640 A

  By the way, in the touch start method, although the influence of the circuit element withstand voltage and electromagnetic noise is small compared to the high frequency start method using high voltage and high frequency, it is necessary to bring the electrode of the welding torch into contact with the workpiece.

  In the welding system in which the welding robot and the arc welding machine perform arc welding in cooperation, the movable arm (manipulator) of the welding robot that supports the welding torch is operated to contact the electrode of the welding torch. In this case, a general operation is to bring the electrodes of the welding torch into close contact with each other while maintaining a vertical posture with respect to the surface of the workpiece.

  On the other hand, the electrode tip of the welding torch is generally polished in a tapered shape, and the arc generation point is stabilized, that is, the arc is stabilized. However, even though it is a non-consumable electrode, the electrode tip caused by the arc is slightly consumed and gradually becomes less sharp. In addition to this, by repeating the operation of bringing the welding torch electrode into vertical contact with the workpiece surface every time the arc starts, the top of the electrode tip is crushed by the pressing force during the contact operation. Deformation further advances the non-sharpening of the top of the electrode tip. As a result, there are concerns that the arc generation point at the tip of the electrode will move variously at an early stage, resulting in an early occurrence of deterioration in arc start performance and unstable arc during welding.

  The present invention has been made in order to solve the above-mentioned problems, and its purpose is to suppress the progress of the electrode tip of the welding torch due to contact with the workpiece to be welded at the time of arc start, and to prevent arcing. It is an object of the present invention to provide an arc start method capable of maintaining the state of occurrence of this well for a long period of time and a welding system using the arc start method.

  An arc start method that solves the above-described problem includes a welding robot and a non-consumable electrode arc welding machine, and supports a welding torch of the welding machine by a movable arm of the welding robot, and an electrode tip of the welding torch and a workpiece to be welded An arc that generates an initial arc at the electrode tip of the welding torch in a welding system that generates an arc between the workpiece and performs a series of arc welding of the workpiece with the operation of the welding torch by the movable arm. In the starting method, the welding power source provided in the welding machine is controlled to apply a predetermined voltage to the electrode of the welding torch, and the operation of the movable arm of the welding robot is controlled to connect the electrode of the welding torch. A touch start method is used in which an initial arc is generated by bringing the workpiece into contact with a workpiece and then pulling it away, and the tip of the electrode of the welding torch is used. The portion has a tapered shape, and when the tip is brought into contact with the surface of the workpiece, the top of the tip of the electrode is tilted with respect to the surface of the workpiece. In order to make contact, the operation control of the movable arm of the welding robot is performed.

  According to this configuration, in the arc start of the touch start method, when the tip of the electrode is brought into contact with the surface of the workpiece, the top of the tip of the electrode is tilted with respect to the surface of the workpiece. The operation which contacts is performed. As a result, of the pressing force during the contact operation, the force in the direction of crushing the top of the tip of the electrode (axial direction) is the component force, so the top of the tip of the electrode in the process of repeating the arc start The deformation that crushes (progress to non-sharpening) is suppressed, and the arc generation state can be maintained well over a long period of time.

In the arc start method described above, it is preferable that the top angle of the tip of the electrode is set to an acute angle.
According to this configuration, when the angle of the top of the tip of the electrode is set to an acute angle, a situation in which the top of the tip of the electrode is easily crushed is likely to occur. Application is very effective.

In the arc start method described above, it is preferable to control so that the current applied to the electrode gradually increases when the electrode is separated from the workpiece.
According to this configuration, when the electrode is pulled away from the workpiece, the current applied to the electrode is gradually increased. In other words, it is possible to maintain the generated arc while reducing the burden on the electrode by reducing the applied current to the electrode at the time of contact with the workpiece and increasing it as it is separated.

  Further, in the above arc start method, a filler wire is supported in the vicinity of the welding torch so as to be able to supply, and the filler wire to be supported and the welding torch operate integrally, and the electrodes of the welding torch It is preferable that the welding torch is tilted in a direction in which the filler wire is separated from the work piece during the tilting.

  According to this configuration, since the welding torch is tilted so that the filler wire operating integrally with the welding torch is in a direction away from the workpiece, the filler wire contacts the workpiece during the tilting operation. Need not be considered.

As a welding system for solving the above-mentioned problems, the above arc start method is used.
According to this configuration, it is possible to suppress the progress of the electrode tip of the welding torch in the process of repeating the arc start of the touch start method, and to provide a welding system that can favorably maintain the arc generation state over a long period of time. Is possible.

  According to the arc start method of the present invention and the welding system using the arc start method, it is possible to suppress the progress of the electrode tip of the welding torch due to contact with the workpiece at the time of arc start, and to generate an arc. The state can be maintained well over a long period of time.

It is a schematic structure figure of a welding system in an embodiment. (A) (b) is explanatory drawing of the arc start operation | movement in embodiment. (A) (b) is explanatory drawing of the arc start operation | movement in a comparative example. It is a schematic block diagram for demonstrating the electrode support aspect in embodiment. It is explanatory drawing of the arc start operation | movement in another example. It is explanatory drawing of the arc start operation | movement in another example.

Hereinafter, an embodiment of an arc start method and a welding system will be described.
As shown in FIG. 1, the welding system 10 is a system configured such that a welding machine 11 and a welding robot 21 operate in cooperation.

  The welding machine 11 is a TIG welding machine which is one of non-consumable electrode type arc welding machines. The welding machine 11 includes a welding power source 12 that generates electric power for arc welding from a commercial power source or the like, the workpiece M is connected to the plus side output terminal of the welding power source 12, and welding is performed to the minus side output terminal of the welding power source 12. A torch 13 is connected. An arc is generated at the tip of the electrode 14 supported by the welding torch 13 based on the supply of the generated power from the welding power source 12, and arc welding of the workpiece M is possible. Such a welding power source 12 is provided with a control device 15, and the control device 15 performs various controls such as electric power control that makes the arc appropriate from time to time and arc start control that generates an initial arc. Yes. Further, the control device 15 is configured to be capable of cooperative control with the control device 25 of the welding robot 21.

  The welding robot 21 includes a movable arm (manipulator) 22, and the welding torch 13 of the welding machine 11 is supported at the tip of the movable arm 22. The welding robot 21 operates the movable arm 22 based on the operation control by the accompanying control device 25, and performs a predetermined operation including the movement / posture of the welding torch 13 (electrode 14). Moreover, it is comprised so that cooperation control with the control apparatus 15 of the welding power supply 12 is possible, and the electrical control of the welding power supply 12 according to operation | movement of the movable arm 22 is interlocked and performed.

Next, the operation (action) of the welding system 10 of the present embodiment will be described.
In the welding system 10, when performing welding on the workpiece M, the user teaches a series of welding operations of both the welding robot 21 and the welding machine 11 (welding power source 12) to the workpiece M using the teach pendant TP. The teaching program is stored in the control device 25 on the welding robot 21 side.

  Then, based on the welding start command, the control device 25 on the welding robot 21 side executes a teaching program in cooperation with the control device 15 on the welding power source 12 side, and mechanical operation of the movable arm 22 of the welding robot 21 is performed. A series of weldings of the workpiece M is performed in cooperation with the electrical operation of the welding power source 12.

  The series of welding operations includes a touch start type arc start operation. As shown in FIGS. 2A and 2B, in the arc start operation of the present embodiment, first, the electrode 14 of the welding torch 13 approaches the workpiece M to the predetermined separation position P1. Next, a no-load voltage is applied between the electrode 14 and the workpiece M, and the tip portion 14a of the electrode 14 of the welding torch 13 moves close to the contact position P0 where it contacts the surface Ma of the workpiece M. In the present embodiment, the attitude of the welding torch 13 is set so that the central axis L1 of the electrode 14 of the welding torch 13 is perpendicular to the surface Ma of the workpiece M at the predetermined separation position P1. As the electrode 14 of the welding torch 13 approaches the electrode 14, the electrode 14 is tilted by a predetermined angle α ° to contact the surface Ma of the workpiece M.

  Here, the tip end portion 14a of the electrode 14 of the welding torch 13 is processed into a tapered shape (conical shape), and in this embodiment, the angle β ° is, for example, 30 ° (15 ° with respect to the central axis L1 of the electrode 14). ) And processed into a sharper shape. When the electrode 14 is in contact, for example, about half of the angle formed by the slope 14b of the tip 14a of the electrode 14 and the surface Ma of the workpiece M ((90 ° −15 °) / 2 = about 37.5 °). An inclination angle α ° is set. That is, the axis L1 of the electrode 14 is inclined at an angle α ° with respect to the surface Ma of the workpiece M, and contact with the workpiece M is achieved at the apex portion 14c of the tip portion 14a of the electrode 14.

  Thereby, although the top part 14c of the tip 14a of the electrode 14 of the welding torch 13 abuts against the surface Ma of the workpiece M, of the pressing force generated by the contact operation of the movable arm 22, the tip 14a of the electrode 14 The force acting in the direction of crushing the top portion 14c (in the direction of the axis L1) is a component force of the pressing force. Therefore, the deformation | transformation which crushes the top part 14c of the front-end | tip part 14a of the electrode 14 at the time of contact operation is suppressed.

  On the other hand, in the arc start operation in the comparative example shown in FIGS. 3A and 3B, the electrode 14 is perpendicular to the surface Ma of the workpiece M when the electrode 14 contacts the workpiece M. In this state, the contact is made by simply bringing them close to each other along the same direction.

  In the operation of the comparative example, since all of the pressing force during the contact operation acts in the direction of crushing the top portion 14c of the tip portion 14a of the electrode 14, the top portion 14c is not sharpened in the process of repeating the arc start. Advance to. As a result, the arc generation point at the tip end portion 14a (the top portion 14c) of the electrode 14 moves variously at an early stage, and the arc generation state may be deteriorated at an early stage. In particular, in the case of using a sharper tip shape in which the angle β ° of the top portion 14c of the tip portion 14a is set to, for example, 30 °, in other words, the electrode 14 having a shape in which the top portion 14c is likely to be crushed and deformed, When such an arc start operation is performed, the apex portion 14c progresses more rapidly to the non-sharpening, and the arc generation state is likely to deteriorate earlier.

  Therefore, if the electrode 14 is brought into contact with the surface Ma of the workpiece M at a predetermined angle α ° as in the present embodiment shown in FIGS. Since the crushing deformation of the top portion 14c of the tip portion 14a of the electrode 14 is difficult to occur, the progress to the non-sharpening of the top portion 14c is slow, and the arc generation state such as arc start property and arc stability during welding is prolonged. It is possible to maintain it well throughout. In particular, the effect is greater as the electrode 14 having an acute tip shape is used.

  As shown in FIG. 4, as a support mode of the electrode 14 with respect to the welding torch 13, the support is generally made with an elastic force in a direction intersecting the axis L <b> 1 of the electrode 14. This is because a shock sensor for detecting an accidental collision with the workpiece M or other member when a force is applied in the lateral direction (cross-axis direction) of the electrode 14 in accordance with the operation of the movable arm 22 is incorporated. It is because it is. The shock sensor has a structure that does not work against the axial force of the electrode 14. That is, the electrode 14 has a support mode that does not have an elastic force in the axial direction.

  Considering such a support mode of the electrode 14, in the comparative example shown in FIG. 3, the crest deformation of the top portion 14 c of the tip end portion 14 a is more likely to occur when the electrode 14 is in contact, but as in the present embodiment shown in FIG. 2. If the electrode 14 is inclined and contacted, the reaction force at the time of contact is absorbed by the elastic force of the shock sensor, and the crushing deformation of the top portion 14c is less likely to occur. With such a support mode of the electrode 14, the effectiveness of the present embodiment is further increased.

  After the contact operation, the electrode 14 of the welding torch 13 is separated from the contact position P0 to the predetermined separation position P1, so that an initial arc is generated mainly from the top portion 14c based on the no-load voltage applied to the electrode 14. Thereafter, the arc start control in which the arc start operation as described above is performed is switched to the normal arc control, and a series of arc welding of the workpiece M with the operation of the welding torch 13 by the movable arm 22 is performed.

Next, characteristic effects of the present embodiment will be described.
(1) In the welding system 10 that performs a touch start type arc start, when the tip 14a of the electrode 14 of the welding torch 13 is brought into contact with the surface Ma of the workpiece M, the electrode 14 is placed on the surface of the workpiece M. An operation is performed in which the apex portion 14c of the tip end portion 14a of the electrode 14 contacts with an inclination (angle α °) relative to Ma. As a result, the force in the direction of crushing the top portion 14c of the tip end portion 14a of the electrode 14 (the direction of the axis L1) out of the pressing force during the contact operation is the component force, so the electrode 14 in the process of repeating the arc start The deformation | transformation (progress to non-sharpening) which crushes the top part 14c of the front-end | tip part 14a can be suppressed, and the generation | occurrence | production state of an arc can be maintained favorably over a long term.

  (2) The more the angle β ° of the apex portion 14c of the tip end portion 14a of the electrode 14 is set to an acute angle, the more easily the deformation that crushes the apex portion 14c of the tip end portion 14a of the electrode 14 occurs. The application to the welding system 10 as in this embodiment using is effective.

In addition, you may change the said embodiment as follows.
FIG. 5 is a welding system 10 using a filler wire 16. The filler wire 16 is supported in the vicinity of the welding torch 13 (in the vicinity of the tip end portion 14a of the electrode 14) so as to be able to supply, and the supported filler wire 16 and the welding torch 13 operate integrally. When the electrode 14 of the welding torch 13 is inclined, the inclination operation of the welding torch 13 is performed in a direction in which the filler wire 16 is separated from the workpiece M. That is, since the tilting operation of the welding torch 13 is performed so that the filler wire 16 that operates integrally with the welding torch 13 is in a direction away from the workpiece M, the workpiece of the filler wire 16 during the tilting operation is performed. There is no need to consider contact with M.

  As shown in FIG. 6, when the electrode 14 is separated from the workpiece M, that is, when the electrode 14 is moved from the contact position P0 to the predetermined separation position P1, the welding power source 12 is controlled so that the applied current I to the electrode 14 is gradually increased. May be performed. In other words, the applied current I to the electrode 14 is low at the time of contact with the workpiece M, and is increased as it is separated, thereby reducing the burden on the electrode 14 and maintaining the generated arc. it can.

  The angle β ° of the apex portion 14c of the tip end portion 14a of the electrode 14 may be a tapered electrode 14 set to other angles such as 60 ° or 120 ° other than 30 °. In this case, as the angle β ° of the top portion 14c is an acute angle less than 90 ° less than the obtuse angle, and the sharper angle less than 45 ° among the acute angles, the effect obtained is greater.

  In the above embodiment, when the electrode 14 is in contact, the inclination angle α ° of the electrode 14 is set to be half of the angle formed by the slope 14b of the tip 14a of the electrode 14 and the surface Ma of the workpiece M. Not limited to this. As long as the apex portion 14c of the tip end portion 14a of the electrode 14 is in an angle range in contact with the workpiece M, it may be appropriately changed.

  -When the electrode 14 is in contact with the workpiece M, a contact time that is considered to be sufficient contact may be set. In this way, it is expected that the initial arc is surely generated when the electrode 14 is subsequently separated.

  The inclination angle α ° of the electrode 14 may be changed in accordance with the usage state of the electrode 14 (for example, the number of arc starts correlated with the degree of wear of the electrode 14). If it does in this way, it can be anticipated that the contact state of the electrode 14 from time to time will be in an appropriate state according to the degree of wear.

Next, a technical idea that can be grasped from the above embodiment and another example will be added below.
(A) An arc start method characterized in that a contact time of a predetermined time or more is set when the electrode contacts the workpiece.

  (B) An arc start method characterized by changing an inclination angle of the electrode according to a use situation of the electrode.

DESCRIPTION OF SYMBOLS 10 Welding system 11 Welding machine 12 Welding power supply 13 Welding torch 14 Electrode 14a Tip part 14c Top part 16 Filler wire 21 Welding robot 22 Movable arm I Applied current M Workpiece Ma Surface

Claims (5)

A welding robot and a non-consumable electrode type arc welding machine, supporting a welding torch of the welding machine by a movable arm of the welding robot, generating an arc between an electrode tip of the welding torch and an object to be welded; In a welding system for performing a series of arc welding of the workpiece with the operation of the welding torch by the movable arm, an arc start method for generating an initial arc at the electrode tip of the welding torch,
The welding power source provided in the welding machine is controlled to apply a predetermined voltage to the electrodes of the welding torch, and the operation of the movable arm of the welding robot is controlled to temporarily contact the electrodes of the welding torch with the workpiece. The touch start method is used to generate an initial arc by pulling it away.
The tip of the electrode of the welding torch has a tapered shape, and when the tip is brought into contact with the surface of the workpiece, the electrode is inclined with respect to the surface of the workpiece. An arc start method characterized in that operation control of a movable arm of the welding robot is performed so as to contact the top of the tip of the electrode. The arc start method according to claim 1,
The arc start method characterized in that the electrode has an acute angle at the top of the tip. In the arc start method according to claim 1 or 2,
An arc start method comprising controlling the current applied to the electrode to gradually increase when the electrode is separated from the workpiece. In the arc start method according to any one of claims 1 to 3,
A filler wire is supported in the vicinity of the welding torch so as to be able to supply, and the filler wire to be supported and the welding torch operate integrally.
An arc start method, wherein when the electrode of the welding torch is inclined, the inclination operation of the welding torch is performed in a direction in which the filler wire is separated from the workpiece.   A welding system using the arc start method according to any one of claims 1 to 4.