WIRE FEED DEVICE AND METHOD FOR FEEDING WIRE

Abstract

The invention relates to a wire-feed device for conveying a wire and to a method for feeding wire using a wire-feed device, in particular for a thermal joining apparatus, having at least one a drive element which can be operated by a feed drive and can be placed against a wire guided through the wire-feed device, exerting a contact pressure, in order to transfer drive movement by friction. According to the invention, an actuator which is coupled to the at least one drive element and can be controlled by a controller using the values measured for the contact pressure, is provided for variably setting the contact pressure acting on the wire.

Claims

1. A wire-feed device (11) to convey a wire (13) for a thermal joining apparatus, comprising: at least one drive element (1) operated by a feed drive (5) and positioned onto a wire (13) that is passing through the wire-feed device (11), said at least one drive element (1) exerting a contact pressure (15) to frictionally transmit a driving movement (14), an actuator (8) that is coupled to the at least one drive element (1), at least one measuring means (21, 22) configured to determine the actuator position (19) and/or to determine the feed of the wire (13) and/or to monitor the wire geometry, a control unit (12) configured to control said actuator (8) using values measured for the contact pressure (15) for variably setting the contact pressure (15) that acts upon the wire (13), wherein the contact pressure (15) is controlled and/or regulated as a function of at least one wire-conveying parameter, and/or as a function of the prescribing feed and/or the ascertained wire geometry, and/or as a function of a welding parameter such as welding current.

2. The wire-feed device (11) according to claim 1, further comprising a pressure rocker (16) between the drive element (1) and the actuator (8).

3. The wire-feed device (11) according to claim 2, wherein the pressure rocker (16) has a restoring spring (17) whose restoring force (18) acts counter to the contact pressure (15).

4. The wire-feed device (11) according to claim 3, wherein the pressure rocker (16) has an actuating cam (10) that constitutes the output of the actuator (8), and a pressure tappet (23) coupled to the drive element (1) and actuated with the actuating cam (10).

5. (canceled)

6. (canceled)

7. The wire-feed device (11) according to claim 1, wherein the at least one measuring means (21, 22) detects the wire geometry optically (21) or mechanically (22).

8. A method for feeding a wire (13) through a wire-feed device (11), comprising: frictionally transmitting a driving movement (14) to the wire (13) with a drive element (1, 4) that is coupled to a feed drive (5), wherein the drive element (1,4) presses against the wire (13) with a contact pressure (15), wherein the contact pressure (15) is variably adjustable to various values with an actuator (8) that is controlled and/or regulated on the basis of measured values for the contact pressure (15), and wherein the contact pressure (15) is controlled and/or regulated as a function of at least one wire-conveying parameter, and/or as a function of the prescribed feed and/or the ascertained wire geometry, and/or as a function of a welding parameter, such as the welding current, and setting the contact pressure (15) at an initial value when the wire feed device (11) is put into operation, and increasing the contact pressure (15) to a value above a slippage limit if slippage between the drive element (5) and the wire (13) occurs, wherein the initial value of the contact pressure (15) corresponds to the most recent value set for the contact pressure (15) and, in the absence of slippage between the drive element (5) and the wire (13) during ongoing operation of the wire-feed device (11), the contact pressure (15) is reduced and, if slippage occurs anew, it is raised once again to a value above the slippage limit.

9. The method according to claim 8, comprising: controlling or regulating the contact pressure (15) as a function of at least one wire-conveying parameter, and/or as a function of the prescribed feed and/or the ascertained wire geometry, and/or as a function of a welding parameter such as welding current.

10. (canceled)

11. (canceled)

12. The method according to claim 8, wherein the contact pressure (15) is incrementally set to discrete values.

13. The method according to claim 8, wherein the contact pressure (15) is set continuously or virtually continuously to different values.

14. The method according to claim 8, wherein the contact pressure (15) is regulated as a function of a parameter measured on the wire-feed device (11) or on a welding unit that is connected to the wire-feed device (11).

15. The method according to claim 14, wherein an algorithm upon which the contact pressure (15) regulation is based is provided according to the principle of a proportional (P) controller, a proportional-integral (PI) controller, a proportional-integral-derivative (PID) controller, an integral (I) controller or a proportional-derivative (PD) controller.

16. The method according to claim 8, wherein values to which the contact pressure (15) is modified or adjusted are temporarily stored and evaluated in order to ascertain system state.

17. The method according to claim 8, wherein force curves are stored and then reconciled with reference curves by means of envelope monitoring.

18. The wire-feed device (11) according to claim 1, wherein the at least one wire conveying parameter is slippage between the drive element (1) and the wire (13) to be conveyed.

19. The method according to claim 8, wherein the at least one wire conveying parameter is slippage between the drive element (1) and the wire (13) to be conveyed.

20. A method for feeding a wire through a wire-feed device, comprising: pressing a drive element to the wire, wherein said drive element is coupled to a feed drive; setting contact pressure of the drive element pressed on the wire to an initial value; adjusting the contact pressure of the drive element on the wire to a value different from the initial value with an actuator, wherein the actuator is controlled and/or regulated in response to measured contact pressure values as a function of at least one wire-conveying parameter selected from the group consisting of: slippage between the drive element and the wire, prescribed feed of the wire, ascertained wire geometry of the wire, a welding parameter, a welding current, and combinations of the foregoing wire-conveying parameters; reducing the contact pressure in absence of slippage being detected between the drive element and the wire; and increasing the contact pressure to a value above a slippage limit if slippage between the drive element and the wire is detected.

21. The method according to claim 20, wherein the contact pressure is regulated as a function of a parameter measured on the wire-feed device or on a welding unit that is connected to the wire-feed device.

22. The method according to claim 21, wherein an algorithm upon which the contact pressure regulation is based is provided according to the principle of a proportional (P) controller, a proportional-integral (PI) controller, a proportional-integral-derivative (PID) controller, an integral (I) controller or a proportional-derivative (PD) controller.

23. The method according to claim 20, wherein values to which the contact pressure is modified or adjusted are temporarily stored and evaluated in order to ascertain system state.

24. The method according to claim 20, wherein force curves are stored and then reconciled with reference curves by means of envelope monitoring.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In this context, the following is shown, at times schematically:

[0045] FIG. 1 a perspective view of a wire-feed device with a mechanical measuring apparatus,

[0046] FIG. 2 a perspective view of the wire-feed device with an optical measuring apparatus,

[0047] FIG. 3 a top view of a section of the wire-feed device with an actuator and a pressure rocker according to FIG. 1 or 2,

[0048] FIG. 4 a perspective view of the section according to FIG. 3,

[0049] FIG. 5 another perspective view of the section according to FIG. 3,

[0050] FIG. 6 a detailed view of the pressure rocker,

[0051] FIG. 7 a perspective view of the detailed view according to FIG. 6,

[0052] FIG. 8 a schematic depiction of the driving movement of a wire,

[0053] FIG. 9 a perspective view of a wire-feed device with a drive belt,

[0054] FIG. 10 a perspective view with a section of a wire-feed device with a drive belt,

[0055] FIG. 11 a perspective detailed view of a wire-feed device with a directly actuated pressure tappet, and

[0056] FIG. 12 a flowchart for determining the contact pressure.

[0057] For the sake of clarity, identical components or those having the same effect are provided with the same reference numerals in the figures shown below.

DESCRIPTION OF THE DISCLOSURE

[0058] The subject matter of the invention relates to wire-feed devices 11, especially those that can be employed not only in the realm of manually guided welding torches but also in machine-guided torches. In the wire-feed device 11 described in the present embodiment, there is at least one drive element 1, 4 that serves to frictionally impart a driving movement to a wire electrode or to a wire 13 that is passing through the wire-feed device 11.

[0059] Here, the drive element 1 is configured as a drive roller; as set forth in the invention, it is likewise conceivable to employ a so-called caterpillar track or a drive belt 4 as the drive element. A wire-feed device 11 with the drive element configured as a drive belt 4 can be seen in FIG. 9 and FIG. 10.

[0060] FIG. 1 and FIG. 2 illustrate the wire-feed device 11 that serves to convey the wire 13, especially for a thermal joining device.

[0061] As can be seen in FIG. 1 and FIG. 2 as well as especially in the detailed views of the wire-feed device 11 according to FIGS. 3 to 5, the wire-feed device 11 has a connection port 2 for a tube pack through which the wire, the power and/or an inert gas can be supplied. The wire 13 is inserted into the wire-feed device 11 via a central connection 3.

[0062] The wire-feed device 11 here has at least one drive element 1 that can be operated by a feed drive 5, whereby said drive element 1 can be placed onto the wire 13 which is inserted all the way through the wire-feed device 11, thereby exerting a contact pressure 15, in order to frictionally transmit a driving movement 14, as illustrated in FIG. 8.

[0063] In the present embodiment, the feed drive 5 can be actuated by means of a wire-feed pushbutton 6, as can be seen in FIGS. 1 to 5.

[0064] In order to use of wires having different diameters, conveying rollers adapted to the wire diameter can be provided so that, as a result, it is always ensured that approximately the same amount of wire is unrolled by the conveying rollers, even in the case of different wire diameters. This adaptation of the conveying rollers can be implemented by means of different groove shapes that are created on the surface of the conveying rollers. In this manner, despite different wire diameters, the amount of wire can be derived from the rotational speed. Moreover, due to this adaptation of the conveying rollers, no provision needs to be made for a feedback to the motor control unit. This allows the contact pressure acting on the wire to be set according to the invention independently of the wire drive.

[0065] FIG. 1 and FIG. 2 as well as FIG. 9 and FIG. 10 also show an actuator 8 that is coupled to the at least one drive element 1 and that can be controlled by a control unit 12 using the values measured for the contact pressure 15 for variably setting the contact pressure 15 that acts upon the wire 13. Here, the actuator 8 drives an actuating cam 10 that acts upon a force measuring means 7 that is configured as a pressure rocker 16. The pressure rocker 16 can have a restoring element, especially a restoring spring 17, so that the restoring force brings it back to its initial position after the activation.

[0066] A display 9, especially an LED unit, can be provided in order to display the contact pressure 15, optionally also for allowing manual readjustment of the contact pressure 15.

[0067] In this context, the variable setting or adjustment of the contact pressure 15 is preferably carried out while the feed drive 5 is running. The setting of the contact pressure 15, which is preferably done by means of an electric motor, allows optimal setting, even of drives that are physically difficult to access because of having been integrated into complex installations. For this purpose, the system can be simplified in such a way that it does not involve an active regulation in the process that would cause the force to vary, but rather, the setting is carried out by means of remote control employing, for example, Panel or Bluetooth, WLAN or the like.

[0068] FIG. 6 and FIG. 7 show that the pressure rocker 16 arranged in a housing 20 between the drive element 1 and the actuator 8 is configured as a coupling gear with a pressure tappet 23 and a restoring spring 17 whose restoring force 18 acts counter to the contact pressure 15. An actuator-generated damping movement which serves to set the contact pressure 15 can be reduced in a suitable manner so that it is also possible to use an actuator 8 whose stroke between its end positions is relatively large. At the same time, a suitable selection of the reduction of the coupling gear allows the operating point of the actuator 8 to be set in such a way that the force generated by the actuator 8 can be controlled or regulated particularly easily.

[0069] FIG. 1 and FIG. 2 respectively show a measuring means 21, 22 for determining an actuator position 19, whereby FIG. 1 depicts at least one mechanical measuring means 21 and FIG. 2 at least one optical measuring 22 to determine the feed of the wire 13 and/or to monitor the wire geometry. The mechanical measuring means 21 or the optical measuring means 22 detects the feed or the wire geometry optically or mechanically, respectively.

[0070] In a perspective detailed view of the wire-feed device 11, FIG. 11 shows a pneumatic or hydraulic contact-pressure force regulator instead of the actuating cam 10. In the embodiment according to FIG. 11, this is a direct drive, whereby the pressure tappet 23 is directly actuated, for example, by means of a pneumatic or hydraulic drive. The other figures show an indirect drive.

[0071] The method according to the invention for feeding a wire 13 that is passing through the wire-feed device 11, especially a wire-feed device 11 of the type described above, will be explained in greater detail below on the basis of a flowchart according to FIG. 12.

[0072] The feed drive 5 frictionally transmits a driving movement 14 to the wire 13 via a drive element 1 coupled to the feed drive 5. In this process, the drive element 1 presses against the wire 13 with a contact pressure 15. The contact pressure 15 can be variably set to different values by means of an actuator 8 that is controlled and/or regulated on the basis of the measured values for the contact pressure 15.

[0073] Fundamentally, the actuator 8 can be based on an electric motor-powered, a pneumatic or a hydraulic mode of operation, or else on a combination thereof, so that the contact pressure in the present embodiments can be configured so as to be electric motor-powered, pneumatic or hydraulic.

[0074] The contact pressure 15 is controlled or regulated as a function of at least one wire-conveying parameter, preferably the slippage between the drive element 1 and the wire 13 that is to be conveyed, and/or as a function of the prescribed feed and/or of the ascertained wire geometry and/or of a welding parameter, especially the welding current.

[0075] In this process, when the wire-feed device 11 is put into operation, first of all, the contact pressure 15 is set at an initial value and increased to a value above a slippage limit if slippage between the drive element 1 and the wire 13 occurs.

[0076] The initial value of the contact pressure 15 corresponds to the last value set for the contact pressure 15. In the absence of slippage between the drive element 1 and the wire 13 during ongoing operation of the wire-feed device 11, the contact pressure 15 is reduced and, if slippage occurs anew, it is raised once again to a value above the slippage limit.

[0077] This setting of the contact pressure 15 can be done either incrementally to discrete values or else continuously or virtually continuously to different values.

[0078] In the present embodiment, the contact pressure 15 is regulated as a function of a parameter measured at the wire-feed device 11 or at a welding unit that is connected to the wire-feed device 11.

[0079] An algorithm upon which the regulation is based is provided according to the principle of a proportional (P) controller, a (PI) proportional-integral controller, a proportional-integral-derivative (PID) controller, an integral (I) controller or a proportional-derivative (PD) controller.

[0080] In particular, in the case of the present embodiment, it is provided for the minimum contact pressure 15 for the wire-conveying system to be ascertained prior to the first time the wire is conveyed during a so-called learning phase. For this purpose, within the scope of a learning run, preferably when a new wire 13 is being threaded in or after a maintenance procedure, the contact pressure 15 is raised incrementally until slippage no longer occurs. This value for the ascertained minimum contact pressure 15 is stored since, as the minimum contact pressure 15, no value falls below it during all of the subsequent wire conveyance procedures until a new learning run is carried out.

[0081] After the learning phase, the wire-feed device works under normal operating conditions. In the eventuality that slippage, that is to say, a non-permissible deviation, occurs during normal operation, the contact pressure 15 is raised proportionally to the deviation and to the preceding contact pressure. If a deviation occurs over several measuring points, these deviations are added up and the contact pressure 15 is additionally increased as a function thereof. The contact pressure 15 is thus raised quickly or “aggressively”, whereby briefly exceeding the absolutely required contact pressure 15 beyond the requisite value can be accepted. For this reason, a subsequent reduction of the contact pressure 15 is necessary and provided for.

[0082] If, after the increase of the contact pressure 15, no new deviation is measured, the contact pressure 15 is reduced proportionally to the preceding increase. The time interval for the measurement is either constant or else it is adapted to the wire-conveying rate that corresponds to a constant wire-conveying quantity.

[0083] Following each wire-conveying cycle without a measurable deviation, the contact pressure 15 is additionally reduced. In this process, the reduction is carried out incrementally over several wire-conveying cycles, whereby the minimum contact pressure 15 is known from the learning phase described above.

[0084] The values to which the contact pressure 15 is modified or adjusted are temporarily stored and evaluated in order to ascertain the system state.

[0085] It is likewise conceivable as set forth in the invention that the force curves are stored and then reconciled with reference curves by means of envelope monitoring.

[0086] As set forth in the invention, it can likewise be provided that, at the moment of the geometric reorientation of an arc-welding torch or of the laser optics, the output, for instance, the current intensity or the laser output is changed at a defined trajectory position in each cycle. This increases the resistance of the wire feed, thus translating into a raised contact pressure 15 which, however, can be viewed as a normal process behavior. For instance, if a single threshold value is used for the entire cycle course, then this threshold value has to be taken into account as the maximum value over the entire trajectory, meaning that wire-feeding problems might remain unrecognized at different places along the trajectory.

[0087] However, if this trajectory-dependent threshold value is only taken into consideration in the area of the reorientation, then the contact pressure 15 can be compared to the concrete trajectory-dependent target value.

[0088] As set forth in the invention, it is likewise conceivable for the wire 13 to run in a meandering pattern over the drive belts 4 as shown in FIGS. 9 and 10. This wire movement can be mechanically coupled to the drive 8. However, a separate drive for the wire is likewise conceivable in order to attain the meandering movement. In this manner, the belt 4 is uniformly abraded over virtually its entire surface area, so that the durability of the belt is markedly increased. The belt width can preferably be about 20 mm.

LIST OF REFERENCE NUMERALS

[0089] 1 drive element (drive roller) [0090] 2 connection port [0091] 3 central connection [0092] 4 drive element (drive belt) [0093] 5 feed drive [0094] 6 wire-feed pushbutton [0095] 7 force-measuring means [0096] 8 actuator [0097] 9 display [0098] 10 actuating cam [0099] 11 wire-feed device [0100] 12 control unit [0101] 13 wire [0102] 14 driving movement [0103] 15 contact pressure [0104] 16 pressure rocker [0105] 17 restoring spring [0106] 18 restoring force [0107] 19 actuator position [0108] 20 housing for the pressure rocker [0109] 21 mechanical measuring means [0110] 22 optical measuring means [0111] 23 pressure tappet