DE20105489U1 - Stud welding head with linear drive - Google Patents

Description

Stud welding head with linear drive

A stud welding head according to the preamble of claim 1 is known from DE 200 03 132 Ul. There, a servo-electric linear drive with an electromagnetic position measuring system is proposed for controlling the lifting and lowering movement of a stud during the welding process. The linear drive is housed together with other elements for power supply and position measurement coaxially with a welding piston in a housing.

Automated stud welding should also be carried out in hard-to-reach places and on complex components. This requires compact, maintenance-friendly welding heads. With conventional welding heads, the area of application is limited to easily accessible places due to the length resulting from the coaxial arrangement of the linear drive and welding piston. Maintenance is also complex and time-consuming due to the integrated design.

The invention is based on the object of at least partially eliminating disadvantages that occur with comparable welding heads according to the state of the art. A more specific object can be seen in providing a particularly compact, maintenance-friendly welding head that allows automated stud welding with consistently high quality even in hard-to-reach places.

The solution to this problem according to the invention is specified in claim 1. The parallel arrangement of the drive axis of the linear drive and the main axis of the welding piston enables a particularly short design. The spatial separation of the drive and welding piston also facilitates maintenance.

Furthermore, the side-by-side arrangement of the linear drive and welding stud makes it possible to provide an external position measuring system without increasing the overall length of the welding head. An external position measuring system can be larger and more precise than the internal position measuring systems usually available and is easier to access for adjustment.

The design of the invention according to claim 2 is favorable from the standpoint of short overall length. The development according to claim 3 allows easy removal of the welding piston for maintenance purposes and increases the versatility of the welding head.

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According to claims 4 and 5, an application-specific optimized position measuring system can be used which is, for example, particularly dirt-resistant, temperature-resistant and/or insensitive to electromagnetic fields.

Claims 6 and 7 relate to a particularly suitable drive which, due to the precise path and speed control, allows the repeatable welding of even thin welding studs.

The invention is explained in more detail below with reference to the drawing, which shows a longitudinal section through a welding head according to the invention with linear drive, linear guide and welding piston.

According to the drawing, the welding head 1 comprises a servo-electric linear drive 2, which consists of a housing 3, a cylindrical rotor 4a and a stator 4b, wherein the rotor 4a can move along a drive axis 5 in the stator 4b.

6 shows an internal position measuring system, which is common in linear drives, for detecting the relative movement between the rotor 4a and the stator 4b. Such position measuring systems have a resolution that allows a positioning accuracy of ±0.1 mm.

For applications that require greater precision, an external position measuring system 7 is arranged at the lower end of the slider 4a in the welding head 1 described here, which detects the relative movement between the slider 4a and the housing 3 and operates with a resolution in the μηη range. An electromagnetic, opto-electronic or inductive position measuring system is suitable. Such a more precise and higher-resolution position measuring system does increase the length of the linear drive, but does not increase the overall length of the welding head due to the parallel arrangement of the linear drive and the welding piston.

A driver 8 is attached to the lower end of the runner 4a, to which the lower end of a guide carriage 9 can be coupled. The guide carriage 9 is mounted on the housing 3 via a linear guide 10 and is arranged such that it overlaps with the runner 4a of the linear drive 2 in the axial direction. The linear guide 10 is adjusted such that its direction of movement runs exactly parallel to the drive axis 5.

A welding piston 11 is attached to the guide carriage 9, the main axis 12 of which runs parallel to the drive axis 5. At the lower end of the welding piston 11, a bolt 13 is shown, which is located in a bolt

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holder 16 is located at a distance above a workpiece surface 14. A feeding device 15 is attached to the welding piston 11, which automatically feeds studs 13 into the stud holder 16.

The linear drive 2, the position measuring system 7 and the welding piston 11 are connected to a control and power supply (not shown) via control and power lines (not shown).

The entire welding head 1 can, for example, be attached to a robot arm (not shown) or another suitable handling device.

For welding, the robot arm guides the welding head 1 to the desired welding position and places the bolt 13, which is seated in the bolt holder 16, onto the workpiece surface 14 when the linear drive 2 is de-energized. In this position, the position of the runner is zeroed using the position measuring system 7. A pre-current is supplied to the bolt 13 via the welding piston 11 and the bolt holder 16, and the linear drive 2 lifts the bolt 13 off the workpiece via the driver 8, the linear guide 10, the guide carriage 9 and the welding piston 11.

The main current is then fed to the bolt 13, whereby the arc that is created between the bolt 13 and the workpiece surface 14 melts the opposing surfaces of the bolt 13 and the workpiece surface 14. According to a programmable path/speed profile, the linear drive 2 dips the bolt 13 into the resulting melt after a certain period of time, whereupon the welding current is switched off. After the melt has cooled, the bolt 13 is welded to the workpiece surface 14.

For the lowering movement of the bolt 13 into the melt, a path/speed profile is advantageous in which the speed decreases steadily, the bolt 13 dips into the melt at a very low speed and the bolt movement is stopped before the bolt 13 hits the bottom of the melt. In this way, ideally, the entire volume of material in the melt is available for the weld joint. Weld spatter is largely avoided and the quality of the weld joint is improved.

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For a subsequent welding, the feeding device 15 feeds a new stud 13 to the stud holder 16 and the welding robot moves the welding head 1 to the next welding position.

Summary

A compact, maintenance-friendly welding head 1 is used to weld bolts 13 to a workpiece surface 14 using an arc, in which the lifting and lowering movement of a welding piston 11 is controlled via a linear drive 2, wherein the drive axis 5 of the linear drive 2 and the main axis 12 of the welding piston 11 run parallel. The welding piston 11 is coupled to the linear drive 2 via a linear guide 10 and a driver 8.

List of reference symbols

1 Welding head 2 linear actuator 3 Housing 4a runner 4b stator 5 Drive axle 6 Internal position measuring system 7 External position measuring system 8th Driver 9 Guide carriage 10 Linear guide 11 Welding iron 12 Main axis 13 bolt 14 Workpiece surface 15 Feeding device 16 Bolt holder

Claims (7)

1. Welding head ( 1 ) with a welding piston ( 11 ) and a linear drive ( 2 ) for welding bolts ( 13 ) to a workpiece surface ( 14 ) by means of an electric arc, characterized in that the drive axis ( 5 ) of the linear drive ( 2 ) and the main axis ( 12 ) of the welding piston ( 11 ) run parallel. 2. Welding head according to claim 1, characterized in that the welding piston ( 11 ) is fastened to a guide carriage ( 9 ) which is coupled to the rotor ( 4a ) of the linear drive ( 2 ) via a linear guide ( 10 ) and overlaps with the rotor ( 4a ) in the axial direction. 3. Welding head according to claim 2, characterized in that the welding piston ( 11 ) is exchangeably connected to the guide carriage ( 9 ). 4. Welding head according to one of the preceding claims, characterized in that the linear drive ( 2 ) is provided with an external position measuring system ( 7 ) arranged in its longitudinal axis. 5. Welding head according to claim 4, characterized in that the position measuring system ( 7 ) is an electromagnetic, optoelectronic or inductive position measuring system. 6. Welding head according to one of the preceding claims, characterized in that the linear drive ( 2 ) is a servo-electric linear drive. 7. Welding head according to claim 6, characterized in that the linear drive ( 2 ) is adjustable according to a predetermined path/speed profile.