METHOD FOR PREPARING AN AUTOMATED WELDING METHOD FOR A WELDING PROCESS AND WELDING DEVICE FOR CARRYING OUT AN AUTOMATED WELDING METHOD

Abstract

A method for preparing an automated welding method for a welding process moves a welding torch with a consumable welding wire during a movement phase at a positioning speed from an actual to a desired start position of a welding seam, and bridges the distance of the welding wire end from the workpiece during a creep phase. The creep phase is at least partially carried out during the movement phase. The wire is moved toward the workpiece at a first specified forward feed speed until a first wire end-workpiece contact is detected, moved away from the workpiece after first contact detection and then recurrently moved away from the workpiece, and the contact is interrupted again upon detection of further contacts, and the movement of the welding wire towards the workpiece and movement away from the workpiece after the contact is repeated until the start position is reached.

Claims

1. A method for preparing an automated welding method for a welding process (SP), wherein a welding torch (2) with a consumable welding wire (3) is moved during a movement phase (BP) at a positioning speed (v.sub.R) from an actual position (IST) to a desired start position (A) of a welding seam (X), which is to be produced during the welding process (SP), and the distance (d) of the end (4) of the welding wire (3) from the workpiece (W) is bridged in that the welding wire (3) is moved to the workpiece (W) during a creep phase (AP) until the welding wire end (4) contacts the workpiece (W), whereupon the welding process (SP) is started at the start position (A) with ignition of an arc (LB), wherein the creep phase (AP) is carried out at least partially during the movement phase (BP), and the welding wire (3) is moved in the direction of the workpiece (W) at a first specified forward feed speed (v.sub.dV1) during the creep phase (AP) until a first contact of the welding wire end (4) with the workpiece (W) is detected, the welding wire (3) is moved away from the workpiece (W) after detection of the first contact, and the welding wire (3) is then recurrently moved away from the workpiece (W) and the contact is interrupted again in response to the detection of further contacts, and the movement of the welding wire (3) to the workpiece (W) until the welding wire end (4) contacts the workpiece (W) and movement away from the workpiece (W) after the contact is repeated until the start position (A) of the welding torch (2) is reached.

2. The method according to claim 1, wherein during the movement phase (BP) after detection of the first contact, the welding wire (3) is moved away from the workpiece (W) at a specified backward feed speed (v.sub.dR) during a specified first time period (Δt.sub.1), and the welding wire (3) is then recurrently moved away from the workpiece (W) in response to the detection of further contacts at a specified backward feed speed (v.sub.dR) during a specified first time period (Δt.sub.1), wherein the backward feed speed (v.sub.dR) is preferably adapted individually in response to each movement of the welding wire (3) away from the workpiece (W) until the start position (A) of the welding torch (2) is reached.

3. The method according to claim 1, wherein the welding wire (3) is moved at a specified second forward feed speed (v.sub.dv2) in the direction of the workpiece (W) for a specified second time period (Δt.sub.2) during the movement phase (BP) after the backward movement of the welding wire (3) from the workpiece (W) after detection of a contact of the welding wire end (4) with the workpiece (W).

4. The method according to claim 1, wherein the welding wire (3) is moved a specified distance (Δ1) in the direction of the workpiece (W) during the movement phase (BP) after the backward movement of the welding wire (3) from the workpiece (W) after detection of a contact of the welding wire end (4) with the workpiece (W).

5. The method according to, claim 1, wherein the creep phase (AP) is carried out for a specified period of time (Δt.sub.AP) after the start of the movement phase (BP).

6. The method according to claim 1, wherein the contact of the welding wire end (4) with the workpiece (W) is detected via a drop of the welding voltage (U).

7. The method according to claim 1, wherein the contact of the welding wire end (4) with the workpiece (W) is determined via a feed device (7) for the welding wire (3).

8. The method according to claim 1, wherein the backward feed speed (v.sub.dR) of the welding wire (3) during the movement phase (BP) is larger than the positioning speed (v.sub.R) of the welding torch (2) in the direction of the workpiece (W) during the movement phase (BP), in particular on average at least 1.5 times as large, preferably at least 2 times as large, particularly preferably at least 5 times as large.

9. The method according to claim 1, wherein the forward movement of the welding wire (3) in the direction of the workpiece (W) during the movement phase (BP) is stopped after reaching a specified maximum free wire length (l.sub.so).

10. The method according to claim 9, wherein the forward movement of the welding wire (3) in the direction of the workpiece (W) during the movement phase (BP) prior to the first contact of the welding wire end (4) with the workpiece (W) is stopped after reaching a specified maximum free wire length (l.sub.so) of 5 mm to 50 mm, preferably 20 mm to 30 mm.

11. The method according to claim 1, wherein the welding wire (3) is moved in the direction of the workpiece (W) during the creep phase (AP) at a first specified forward feed speed (v.sub.dV1) between 0.5 m/min and 200 m/min, in particular between 1.5 m/min and 20 m/min.

12. The method according to claim 3, wherein during the movement phase (BP) after the backward movement of the welding wire (3) from the workpiece (W) after detection of a contact of the welding wire end (4) with the workpiece (W), the welding wire (3) is moved in the direction of the workpiece (W) at a specified second forward feed speed (v.sub.dv2) between 0.5 m/min and 200 m/min, in particular between 1.0 m/min and 10 m/min.

13. The method according to claim 2, wherein during the movement phase (BP), the welding wire (3) is moved away from the workpiece (W) at a specified backward feed speed (v.sub.dR) between 0.5 m/min and 200 m/min, in particular between 5 m/min and 60 m/min.

14. The method according to claim 1, wherein a protective gas (G) is activated during the movement phase (BP) a specified time period (Δt.sub.G) after the detection of the first contact of the welding wire end (4) with the workpiece (W), preferably after 0 s to 10 s.

15. A welding device (1) for carrying out an automated welding method, comprising a welding torch (2) with consumable welding wire (3), a welding current source (5), a feed device (7) for the welding wire (3), and a control device (6), wherein the control device (6) is formed for carrying out the method according to claim 1.

Description

[0024] The present invention will be described in more detail on the basis of the enclosed drawings, in which:

[0025] FIG. 1a shows a schematic image of a welding device for carrying out an automated welding method;

[0026] FIG. 1b shows an illustration of the movement of a welding torch to the start position of a welding seam and while carrying out a welding process;

[0027] FIG. 2 shows the time courses of the positioning movement of a welding robot carrying the welding torch, of the distance of the end of the consumable welding wire from the workpiece, of the welding start command, of the welding voltage, of the feed speed of the welding wire, of the welding current, and of the activation of the protective gas prior to carrying out a welding process according to the prior art;

[0028] FIG. 3 shows the time courses of the positioning movement of a welding robot carrying the welding torch, of the distance of the end of the consumable welding wire from the workpiece, of the start command for the creep phase, of the welding start command, of the welding voltage, of the feed speed of the welding wire, of the welding current, and of the activation of the protective gas prior to carrying out a welding process according to a first embodiment of the method according to the invention; and

[0029] FIG. 4 shows the time courses of the positioning movement of a welding robot carrying the welding torch, of the distance of the end of the consumable welding wire from the workpiece, of the start command for the creep phase, of the welding start command, of the welding voltage, of the feed speed of the welding wire, of the welding current, and of the activation of the protective gas G prior to carrying out a welding process according to a second embodiment of the method according to the invention.

[0030] FIG. 1a shows a schematic image of a welding device 1 for carrying out an automated welding method. The welding device 1 includes a welding torch 2 for a consumable welding wire 3, which is moved by a robot 10 or similar manipulator for the automated welding method. The welding torch 2 is connected to a welding current source 5 and to a feed device 7 as well as usually to a gas tank 8 for a protective gas G via a hose package 9. A corresponding control device 6, which specifies the time courses of all components, is located in the welding current source 5.

[0031] FIG. 1b shows the illustration of the movement of a welding torch 2 to the start position A of a welding seam X and for carrying out a welding process SP according to the prior art. Prior to the start of an automated welding method, the welding torch 2 is on a specific actual position IST. Prior to starting a welding process SP, during which a welding seam X from a start position A to an end position E is to be welded, the welding torch 2 has to be moved from the actual position IST to the desired start position A during a movement phase BP. The movement takes place at a corresponding positioning speed v.sub.R of the welding torch 2. After the movement phase BP, the distance d of the end 4 of the welding wire 3 to the workpiece W is bridged in that the welding wire 3 is moved to the workpiece W during a subsequence creep phase AP at a usually relatively low forward feed speed until the welding wire end 4 contacts the workpiece W. After the contact, the welding process SP can be started with ignition of the arc LB. The creep phase AP can sometimes be relatively long, for example between 50 ms and 500 ms, which can lead to unwanted delays in the cycle time in the case of a plurality of welding seams X.

[0032] According to the invention, the creep phase AP is thus already carried out at least partially during the movement phase BP, and the welding wire 3 is moved at a first specified forward feed speed v.sub.dV1 in the direction of the workpiece W during the creep phase AP until a first contact of the welding wire end 4 with the workpiece W is detected. After the detection of the first contact of the welding wire end 4 with the workpiece W, the welding wire 3 is moved away from the workpiece W again, and the welding wire 3 is then recurrently moved away from the workpiece W in response to the detection of further contacts and the contact is interrupted again, and the movement of the welding wire 3 to the workpiece W is repeated until the welding wire end 4 contacts the workpiece W and is moved away from the workpiece W after the contact until the start position A of the welding torch 2 is reached. An approach of the welding wire end 4 to the surface of the workpiece W thus already takes place during the movement phase BP, so that the welding wire end 4 is always spaced apart from the workpiece W only by a small distance d when reaching the welding torch 2 at the start position A of the welding seam X, and the ignition process can be continued right away, and the welding process SP can be started.

[0033] FIG. 2 shows, schematically, the time courses of the positioning movement of a welding torch 2 carried by the welding robot 10, of the distance d of the welding wire end 4 of the consumable welding wire 3 from the workpiece W, of the welding start command S2, of the welding voltage U, of the feed speed v.sub.d of the welding wire 3, of the welding current I, and of the activation of the protective gas G prior to carrying out a welding process SP according to the prior art. During a movement phase BP, the welding torch 2 is moved by means of the robot 10 at a positioning speed v.sub.R to the start position A of the welding seam X. During the creep phase AP, the welding wire 3 is then moved to the workpiece W, whereby the distance d between welding wire end 4 and surface of the workpiece W is reduced more and more. To prevent that the welding wire 3 impinges on the surface of the workpiece W at an excessive speed, a relatively low forward feed speed v.sub.dv3 of the welding wire 3 is selected during the creep phase AP. The creep phase AP can last correspondingly long. During the creep phase AP, the no-load voltage U.sub.LL is applied to the welding wire 3. If the welding wire end 4 contacts the surface of the workpiece W, the drop of the no-load voltage U.sub.LL is detected, and an arc LB can be ignited, whereupon the welding current I rises accordingly, and the welding process SP can be started. During the welding process SP, the welding current I or the welding voltage U, respectively, and the feed speed v.sub.d of the welding wire 3 are controlled accordingly until the end position E of the welding seam X is reached. The welding process SP is then ended. In the case of the common use of a protective gas G, for example of argon, the supply of the protective gas G is already started with the onset of or during the movement phase BP, which is why a relatively large amount of protective gas G is wasted prior to the ignition of the arc LB at the start of the welding process SP.

[0034] FIG. 3 shows the time courses of the positioning movement of a welding robot 10 carrying the welding torch 2, of the distance d of the welding wire end 4 of the consumable welding wire 3 from the workpiece W, of the start command S1 for the creep phase AP, of the welding start command S2, of the welding voltage U, of the feed speed v.sub.d of the welding wire 3, of the welding current I, and of the activation of the protective gas G prior to carrying out a welding process SP according to a first embodiment of the method according to the invention. In contrast to the prior art (FIG. 2), the creep phase AP is already carried out during the movement phase BP, during which the welding torch 2 is moved from the actual position IST to the start position A of the welding seam X by means of the robot 10 at a positioning speed v.sub.R, and the distance d of the welding wire end 4 to the surface of the workpiece W is decreased. This takes place in that the welding wire 3 is moved in the direction of the workpiece W at a first specified forward feed speed v.sub.dV1 until a first contact of the welding wire end 4 with the workpiece W is detected. The distance d of the welding wire end 4 to the surface of the workpiece W changes continuously during the movement phase BP by means of the forward and backward movement of the welding wire 3, and preferably lies between 0 mm and a maximum value defined by the specified backward feed speed v.sub.dR of the welding wire 3 and the specified first time period Δt.sub.1, after the first contact of the welding wire end 4 with the surface of the workpiece W. The detection can take place by the drop of the no-load voltage U.sub.LL or by measuring the force or force change at the motor or also by detection of a speed change of a feed device 7. After detection of the first contact, the welding wire 3 is moved away from the workpiece W at a backward feed speed v.sub.dR, and the contact is interrupted again. The backward movement of the welding wire 3 can thereby take place for a specified first period of time Δt.sub.1, wherein the specified first period of time Δt.sub.1 corresponds at least to the period of the short circuit of the welding wire end 4 with the workpiece W. In this exemplary embodiment, the welding wire 3 is then stopped.

[0035] When the welding wire 3 is moved a specified distance Δl in the direction of the workpiece W during the movement phase BP after the backward movement of the welding wire 3 away from the workpiece W after detection of a contact of the welding wire end 4 with the workpiece W, it can be prevented that an excessive free wire length l.sub.so (“stick-out”) protrudes from the welding torch 3, which could be bent when contacting the workpiece surface (not illustrated). Such a case could arise when irregularities are located on one or also on several workpiece surfaces in the movement path of the welding wire 3 or of the welding wire end 4, respectively, during the positioning. This movement path during the positioning is understood to be that region in the space, which the welding wire end 4 passes through or spans, respectively, during the movement phase BP. On the one hand, this movement path thus consists of the movement of the welding robot 10 from the actual position IST to the start position A and, on the other hand, by the overlapped forward and backward movement of the welding wire 3. A bending of the free welding wire end 4 when contacting the workpiece W could occur when gaps, joint gaps, holes, pores, bores, rough or uneven mechanical machining grooves, or similar irregularities are located in the movement path, in the region of one or several workpiece surfaces, and a contact with a workpiece surface thus does not take place. Elevations or raised points, respectively, on the workpiece surface could further also lead to problems. Insufficiently deburred workpieces W, irregular joint gaps, contaminations, weld spatters, but also general surface errors of the workpieces W are mentioned here, for example. Workpieces W with a general surface texture, a directed texture, or an uncommonly high surface roughness could further also unintentionally bend the welding wire 3. The process of the forward and backward movement of the welding wire 3 could be repeated until the welding torch 2 has reached the start position A of the welding seam X. The arc LB is then ignited and the welding process SP is started. After reaching the end position E of the welding seam X, the welding process SP is ended. Due to the fact that the creep phase AP is already carried out during the moment phase BP, and the distance d of the welding wire end 4 from the workpiece W is minimized or bridged, respectively, the creep phase AP can be reduced significantly in time compared to the prior art, and the cycle time of the welding method can thus be increased.

[0036] The creep phase AP can be divided into a first creep phase AP1, which is already carried out during the movement phase BP of the welding robot 10, and a second creep phase AP2, which is carried out after reaching the start position A of the welding seam X. The first creep phase AP1 is thereby the part of the creep phase AP according to the invention, while the second creep phase AP2 corresponds to the creep phase AP known from the prior art.

[0037] The supply of the protective gas G can take place as a function of the detection of the first contact of the welding wire end 4 with the workpiece W or a specified time period Δt.sub.G after the detection of the contact, whereby protective gas G can be saved during the movement phase BP. A specified time period Δt.sub.G of 0 s, i.e., a turn-on of the protective gas G immediately after the first contact of the welding wire end 4 with the workpiece W, is illustrated in FIG. 3. The specified time period Δt.sub.G is thus not illustrated explicitly in FIG. 3.

[0038] FIG. 4 shows the chronological sequences of the positioning movement of a welding torch 2 carried by the welding robot 10, of the distance d of the welding wire end 4 of the consumable welding wire 3 from the workpiece W, of the start command S1 for the creep phase AP, of the welding start command S2, of the welding voltage U, of the feed speed v.sub.d of the welding wire 3, of the welding current I, and of the activation of the protective gas G prior to carrying out a welding process SP according to a second embodiment of the method according to the invention. In contrast to the embodiment according to FIG. 3, the welding wire 3 is not stopped here after the backward movement after the detection of the first contact of the welding wire end 4 with the workpiece W, but is moved in the direction of the workpiece W at a specified second forward feed speed v.sub.dv2. The forward movement of the welding wire 3 at the specified second forward feed speed v.sub.dv2 can be carried out for a specified second time period Δt.sub.2. This is preferably used when the used wire feed system (wire feed motor) has a higher inertia, whereby a larger distance of the welding wire end 4 to the workpiece W appears after the end of a backward movement. Due to the repeated forward movement of the welding wire 3 for a certain time period Δt.sub.2, the distance is kept as small as possible. After detection of the next contact of the welding wire end 4 with the workpiece W, a backward movement of the welding wire away from the workpiece W could take place again at the backward feed speed v.sub.dR (not illustrated in FIG. 4). After reaching the start position A, the arc LB is ignited and the welding process SP is started. The supply of the protective gas G can take place again as a function of the detection of the first contact of the welding wire end 4 with the workpiece W or a specified time period Δt.sub.G after the detection of the contact. A specified time period Δt.sub.G of 0 s, i.e. a turn-on of the protective gas G immediately after the first contact of the welding wire end 4 with the workpiece W is also illustrated in FIG. 4. The specified time period Δt.sub.G is thus not illustrated explicitly in FIG. 4.

[0039] Here, the creep phase AP can also be divided into a first creep phase AP1, which is already carried out during the movement phase BP of the welding robot 10, and a second creep phase AP2, which is carried out after reaching the start position A of the welding seam X.

[0040] As suggested in the uppermost time diagram of the embodiment according to FIG. 4, the creep phase AP can also be carried out a specified period of time Δt.sub.AP after the start of the movement phase BP, thus after the start of the movement of the welding torch 2 from the actual position IST in the direction of the start position A. For example, this period of time Δt.sub.AP1 can be between 200 ms and 2000 MS.

[0041] The present method for preparing an automated welding method for a welding process SP and the welding device 1 provided for this purpose for carrying out an automated welding method provides for a reduction of the time delay during the creep phase AP, whereby the welding process SP can be started more quickly and protective gas G can be saved as well.