Patent Application
20200406390
At the beginning of the nineties of the last century, friction stir welding was developed. In the meantime, friction stir welding is being successfully used among other things for the welding of aluminum alloys in many areas of industry.
The applications range here from one-off pieces and small batches through to larger batches. Apart from the outstanding quality of the weld seam, other factors contributing to the commercial success are the high degree of reproducibility and the little preparational work and expenditure on finishing.
In friction stir welding, frictional heat is generated in the joining region of the materials to be connected by means of the friction between a rotating tool which at the same time is moved translationally and to which pressure is applied. The tool is moved along the joining region and stirs the plastified material in the interior of the seam of the materials to be connected that are butting against one another. The applied pressure presses the plastified material together. At the end of the weld seam created, the tool is withdrawn from the region of the connection and the weld seam can be subjected to loading immediately.
For prior art, reference is made to DE 10 2014 005 315 B3, originating from the applicant.
This concerns a method and a device for detecting the mechanical forces at the welding pin tip during the operation of friction stir welding and also a computer program and a machine-readable carrier with a program for carrying out the method.
The invention provided there is based on the object of optimizing the welding operation during friction stir welding in such a way that the decisive process parameters, such as the axial force of the tool occurring, the torque occurring and the temperature of the welding pin tip can be detected exactly, even in 3D applications.
According to patent claim 1, to achieve this object, it is a matter of optimizing a device for detecting the mechanical forces at the welding pin tip during the operation of friction stir welding in such a way that the decisive process parameters,
However, breakages of friction pins can occur during the operation of systems for friction stir welding as a result of local changes in the material within welding assemblies, for example due to variations in hardness in the case of cast materials.
The present invention is therefore based on the object of ensuring the commercial operation of a system for friction stir welding and avoiding breakage of the friction pin within the welding process.
This object is achieved by the features in patent claim 1
a device for avoiding an interruption of the welding process during friction stir welding, in particular breakage of the friction pin, with the following features:
And the method according to patent claim 5. A method for avoiding an interruption of the welding process during friction stir welding, in particular breakage of the friction pin, with the following features:
The device according to the invention is described in more detail below: Specifically:
Here, 1 designates a sensor for measuring the pressure between a fastening flange 2 and a drive 3 for the rotation of the gear mechanism and a tool 3. On the side of the drive 3, the control line for the entire friction welding head is designated by 4. On the underside of the drive 3, a fastening plate 5 for the tool dome flange 6, which carries the tool dome 6, can be seen.
In order to be able to detect the movement of the tool dome 6 by measuring instrumentation, strain gages 8 with temperature compensation are mounted at the circumference of the tool dome 6, fastened at regular intervals in the longitudinal direction. This serves the purpose of counteracting the changes in temperature occurring during welding in the region of the strain gage, and consequently a signal shift. A union nut 9 keeps the tool dome 7 on the central axis of the friction welding head.
The pin tip 12 is guided in the welding shoe 11. The laser measuring sensor 10 shown serves for measuring the distance between the welding shoe 11 and the pin tip 12.
The weld seam 15 applied to the parts to be joined 13 is observed by a camera 14 for checking the weld seam.
The sensor 22, installed in the same region, in the cross-sectional narrowing shown of the tool receiving cone 28 guiding the welding pin, serves for measuring the axial force acting at this point, the torque and the bending moment.
The signal transmission of the measured values determined by the sensor 22 takes place by way of a signal amplifier 23, which can rotate with the tool receiving cone 28, and a tube antenna.
The reception and passing on of the measured values determined by the sensor 22 takes place by way of a statically fixed antenna 16.
An inductive power supply, the static, primary winding of which is designated by 24 and the movable, secondary winding of which is designated by 25, serves for supplying power to the described measuring systems.
Openings 20 for the material outflow of the smoke residue of the parts to be joined on the welding pin 19 are provided in the region of the pin tip 12, and also a sensor 21 for measuring for measuring the material outflow of the parts to be joined.
The welding shoe 11 guiding the welding pin 19 is held by a union nut 9.
The camera 14 serves for registering and recording the operations during the welding operation.
Apart from the pin tip 12, a structure-borne sound sensor 29, which is directed with its directional effect into the region between the welding pin 19 and the welding shoe 11, is installed in the region of the upper end of the union nut 9. In this respect, reference is made to
Arranged opposite the laser measuring sensor 10 is an airborne sound sensor 30.
With regard to the exact position, reference is also made here to
The eddy current sensor 31 can be used for measuring extremely small distances. Its arrangement transversely to the welding direction is advantageous.
Here it is shown how a deviation of the welding pin 19 with its pin tip 12 from its normal central position within the round hole 27 in the welding shoe 11 can be detected and exactly measured by means of the laser measuring sensor 10 shown and the airborne sound sensor 30 arranged opposite.
In addition, the eddy current sensor 31 known from
The directional arrow 26 indicates the direction of movement of the welding pin 19. In a particular embodiment, a special welding shoe temperature sensor that is not designated any more specifically is provided. After all, in the case of full contact of the rotating pin against the shoulder bore (worst case scenario), there is a temperature increase of approximately 100 degrees C. That is a significant increase in the temperature in comparison with the actual welding operation.
Seen from the outside inward, the concentric circles shown represent the edge of the tool dome 7, the outer delimitation of the welding shoe 11 and the following inner delimitation, not designated any more specifically, of the welding shoe 11. At the circumference of the outer delimitation of the welding shoe 11, designated in the direction of movement of the arrow 26 directed to the right are a sensor 8. These sensors 8, distributed altogether at the circumference of the tool dome 7, can also be taken from
Sketched at the inner delimiting line of the welding shoe 11 is the structure-borne sound sensor 29 known from
Eccentric in relation to the circle described, the welding pin 19 with its pin tip 12 is represented with various distance lines, the line 33 representing the ideal line of the distance of the welding pin 19 from the inner delimiting line of the welding shoe 11, the so-called gap zone.
The delimiting lines of the gap zone are represented by 32 and 35 and the critical region that can lead to breakage of the welding pin 19 begins at 34. The shortest distance between the welding pin 19 and the welding shoe 11 is represented as an active zone. The greatest friction between the inner delimitation of the welding shoe 11 and the welding shoe 19 prevails in this region. This distance is dependent on the rate of advancement (arrow 26) of the frictional welding head and the rotational speed of the welding pin 19. The forces occurring laterally thereby are detected by way of the tool dome or rather with the sensors 8, 8a and 8b fastened on it.
With the following sensors, the further forces occurring are measured:
1. With the laser measuring sensor 10, the distance of the welding pin 19 from the welding shoulder is measured.
2. With the structure-borne sound sensor 29, the vibrations in the welding pin 19 are measured.
3. With the airborne sound sensor 30, the vibrations in the welding shoe 11 and at the tool dome 7 are measured.
4. With the eddy current sensor 31, the direction of the material in the gap between the delimitation 32 and 35 is measured.
The ideal line, at which the pin tip 12 achieves the greatest useful life, is reached with the line 33. It signifies the optimum between optimum advancement and the rotational speed of the tool.
The welding-in depth is 4.3 mm and the rate of advancement of the pin tip is 0.85 m/mm. The beginning of the measurable resistance of the pin tip can be seen in the left marking line; after approximately 1.7 seconds, the prevention time ends and then a further approximately 0.8 seconds pass until there is a breakage.
In this time period, the machine controller can provide relief, whereby an elastic “springback” of the pin is achieved. Therefore, no disadvantageous damage occurs.
After that, after this period of time, permanent damage then occurs.
In
The gap zone 32 represented (cf.
The dimension X is the dimension by which the remaining shoulder can enter the welding shoe 11.
The remaining shoulder Y is of importance, in order that the material to be welded receives the necessary temperature in order to gain sufficient plasticity to be able to flow through the gap Z. At too low a temperature, a buildup occurs, and the pin shaft 19 is damaged.
The dimension X (0.01 to 0.1 mm) is respectively set according to the material (alloy). The remaining shoulder generates heat, which also has an influence on the smoothing operation by the welding shoe 11 on the finished weld seam.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2018 001 774.6 | Mar 2018 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/DE2019/000044 | 2/22/2019 | WO | 00 |
