EP3530359B1 - Device and method for machining workpieces or objects - Google Patents

Description

The invention relates to a device and a method for processing workpieces or objects with the features of the preamble of the independent claims.

It is known that when introducing workpieces into objects, the feed force for introducing the tool or workpiece into the object can be significantly reduced if the tool or workpiece is subjected to vibrations, in particular ultrasonic vibrations.

Out of DE 10 2006 045518 A1 an ultrasonic vibration transducer for ultrasonic drilling is known.

Out of US 7,740,088 For example, an ultrasound-assisted hammer drill is known.

Out of DE 10 2014 203 757 A1 a method for connecting two components using the punch riveting process is known, in which a rivet and/or components are caused to vibrate by means of a device.

By introducing the vibrations, the required feed force can be reduced by up to a factor of 10. Known devices are based on vibrations being transmitted to a tool and/or workpiece by an oscillator via a pulse transmission element. The transmitted impulses expose the tool or workpiece to regular loads, which increases the friction between the tool and workpiece on the one hand and the object on the other and thus the

Press-in force can be reduced. The impulse transmission element is designed as a separate component from the oscillator. Particularly when using ultrasonic vibrations, the oscillator oscillates in a resonance mode. The impulse transmission element is separated from the oscillator as a separate element and does not oscillate in resonance, but primarily serves to transmit the impulse from the oscillator to the tool or workpiece. The impulse transmission element is designed as a wearing part and can be easily replaced without having to replace the oscillator, which is more complex to produce. In addition, the pulse transmission element can also be made long and/or thin according to the requirements of the application, without having to take resonant tuning into account. However, this division into oscillator and impulse transmission element has various disadvantages. In particular, the lack of connection between the impulse transmission element and the oscillator can lead to misalignment and thus to quality problems. Likewise, the impulse transmission is often not optimal, so that excessively high power has to be applied by the oscillator. In addition, there is the problem, especially at the end of processes (for example when the tool or workpiece to be driven in encounters resistance), that vibrations from the oscillator are coupled into the workpiece or tool via the impulse transmission element. In this case, there is a risk of unintentional connection in the area of the interfaces between the oscillator and the impulse transmission element and/or the impulse transmission element and the workpiece/tool.

It is therefore an object of the present invention to avoid the disadvantages of the known, in particular to create a device and a method which guarantee a high and consistent quality of processing, which enable optimal use of energy and/or which prevent unintentional connection between Prevent the oscillator, impulse transmission element and tool or workpiece.

It is also conceivable that undesirable adhesion occurs between the impulse transmission element and a guide. These should also be prevented.

According to the invention, these and other tasks are solved with a device and a method according to the characterizing part of the independent claims.

The device according to the invention is used to process workpieces. For this purpose, it includes a tool by means of which the workpiece can be processed directly (e.g. if the tool is a drill) or indirectly (e.g. if the tool acts on a workpiece that is driven into the object). The device has a pressing device by means of which the tool can be pressed against the workpiece or object. The tool or workpiece can be driven into the object by pressing. The device also has a vibration generating device and a pulse transmission element.

The vibration generating device comprises a vibrator and is used to generate vibrations on a work surface of the vibrator. In particular, ultrasonic vibrations can be generated in a manner known per se.

The pulse transmission element has an excitation surface and a pulse transmission surface which lies opposite the excitation surface. The excitation surface can be brought into contact with the working surface of the oscillator. In this way, pulses can be transmitted from the oscillator to the pulse transmission element. The impulse transmission surface can be brought into contact with the tool, the workpiece or an intermediate piece. An intermediate piece can, for example, be part of the tool, form the tool or be present as a passive additional part.

By means of the pulse transmission element, vibrations can be transmitted from the vibration generating device to the workpiece and/or tool.

According to the invention, a centering arrangement is provided between the oscillator and the pulse transmission element. In particular, the working surface of the oscillator is concave and the excitation surface of the pulse transmission element is convex. Alternatively, the working surface of the oscillator is convex and the excitation surface of the pulse transmission element is concave. Due to this convex/concave geometry, the impulse transmission element is automatically centered in relation to the oscillator. Misalignments, which can lead to quality problems, are automatically avoided. An additional fixation or centering of the impulse transmission element is therefore not necessary. Centering and consistently high quality of the machined workpiece or object are achieved in a structurally simple manner. Particularly preferably, the concave surface has a radius of curvature that is greater than or equal to the radius of curvature of the convex surface. In particular, the concave working surface of the oscillator is provided in a central section with a radius of curvature that is greater than or equal to the radius of curvature in a central section of the convex excitation surface of the impulse transmission element. In the case of a convex working surface of the oscillator, the radius of curvature in a central section of the working surface of the oscillator is less than or equal to the radius of curvature in a central section of the concave excitation surface of the momentum transfer element.

According to the invention, the pulse transmission element has an end section of a certain length to the excitation surface and/or in an end section of the same length adjacent to the impulse transmission surface has a greater mass than in a middle section of again the same length between the sections. In this way, the impulse transmission can be optimized. A heavier end section adjacent to the excitation surface is able to absorb a larger impulse (i.e. mass times speed). A heavier section adjacent to the impulse transfer surface is suitable for transmitting a larger impulse to the workpiece or tool. While such an arrangement with a larger mass in one or both end sections is advantageous on its own, it goes without saying that it can also be used advantageously in combination with the above-mentioned concave/convex design of the excitation surface and working surface.

The greater mass of the end regions can be achieved in various ways: It is preferably conceivable that the excitation surface and/or the impulse transmission surface has a larger cross section than the central section.

Alternatively or additionally, it is also conceivable to use a material with a greater density in one or both end sections than in the middle section. In this case, the impulse transmission element can preferably be constructed from a base body which consists of a first material. In at least one of the end sections, an insert made of a second material can be inserted into the base body adjacent to the excitation surface and/or adjacent to the impulse transmission surface. Due to the material properties, especially density and strength, tungsten is conceivable and preferred. But it is also conceivable to have inserts made of different materials on the two end sections to use. It is important that the second material has a higher density than the first material.

The cross-sectional area of the excitation surface is preferably at least 150% of the cross-sectional area of the impulse transmission surface.

According to yet another aspect of the invention, the device is operable in a first pulse transmission mode and in a second vibration coupling mode. In the vibration coupling mode, the vibration parameters and/or the contact force of the pressing device are selected differently than in the pulse transmission mode. In particular, in the pulse transmission mode, the contact force and/or the amplitude of the vibration is greater than in the vibration coupling mode. It was found that as the workpiece and/or tool progresses, a point in time occurs at which the force acting on the tool or workpiece increases sharply. This is the case, for example, when the workpiece or tool comes into contact with a stop surface or when the workpiece or tool encounters an obstacle, for example an area of higher density in the body into which the workpiece or tool is driven. In such a case, it is conceivable that there is no longer a pure impulse transmission from the oscillator to the tool or workpiece, but that the tool or workpiece couples to the impulse transmission element in terms of vibration. In this case, the oscillator, the impulse transmission element and the workpiece and/or tool vibrate together and the undesirable connection explained above can occur.

In other words, between the pulse transmission mode and the vibration coupling mode, there is a transition between a classic movement sequence without resonant vibration phenomena and a resonance operation.

By specifically adjusting the vibration parameters and/or reducing the contact force in the vibration coupling mode, such an undesirable connection can be prevented. In principle, it is conceivable to control and reduce or change the contact force or the amplitude or the frequency by a control arrangement if it is determined that the device is in the vibration coupling mode.

However, it is also conceivable to achieve a force reduction through passive elements. In particular, it is conceivable and advantageous to provide the device with a stop surface on which the impulse transmission element can be supported when the device enters the vibration coupling mode. In particular, the stop surface causes the force to be absorbed by the stop surface in the vibration coupling mode. The tool and/or workpiece is therefore subjected to a lower force. Due to the lower force, there is no coupling or the energy transferred into the workpiece/tool is also reduced due to the reduced force. In this way, unintentional connection can be effectively prevented using simple means.

However, it is also conceivable to provide the device with a measuring unit. The measuring unit can measure the path traveled by the tool, the force acting on the tool, the frequency of the vibration or the power consumed by the vibration generating device (or combinations thereof). A control unit of the device can switch the operation of the device from the pulse transmission mode to the oscillation coupling mode depending on these measured values. This can occur in particular when a target path traveled by the tool is exceeded, when a target force acting on the tool is exceeded and/or when the power or frequency of the vibration generator changes beyond a target value.

According to a preferred embodiment, the device can be operated in a third release mode by means of the control unit after the oscillation clutch mode. In the detachment mode, the contact force generated by the pressing device is reduced and detachment vibrations are generated with the vibration generating device. The separation oscillations can preferably be generated with the same frequency and with the same or lower amplitude as the oscillations in the pulse transmission mode or in the oscillation coupling mode. If, despite the reduction in the vibration parameters and/or the force in the vibration coupling mode, an unintentional connection occurs between the oscillator, the impulse transmission element and the workpiece/tool, this connection can be separated again in the release mode by the release vibrations. The detachment vibrations can in particular as in the pending application PCT/EP2018/052030 be designed as described by the same applicant.

The tool according to the device according to the invention can preferably be a drill, a hammer, a punch, a rivet former or a perforation needle. It is conceivable that the tool is formed directly by the impulse transmission element, is designed as a separate part but is firmly connected to it, or is designed as a separate additional element. In particular, in the case of a hammer, the impulse transmission element can directly take over the function of the hammer. In the case of a drill or a perforating needle, the tool is typically designed as a separate element.

Other applications include expanding rivets for creating composite materials, for example from CFRP and aluminum, punching out holes or perforating with needles, especially in non-plasticized materials.

The dimension of the impulse transmission element is of course adapted to the corresponding application. Typical dimensions are 5 to 200 mm, preferably 50 to 100 mm and particularly preferably 60 to 80 mm. Preferred diameters in the area of the impulse transmission surface are typically 5 to 15 mm, preferably 6 to 10 mm and particularly preferably 7 to 8 mm.

According to a further preferred embodiment, the pulse transmission element can be provided with slots and/or reinforcing ribs. This increases process accuracy, especially in combination with relatively thin diameters. Slots can also cause the vibration coupling mode to only kick in at higher contact pressures.

A slit also leads to cooling. Cooling can also prevent or reduce unwanted adhesion.

Typically, the vibration generating device is designed to generate ultrasonic vibrations with a frequency of 10 to 30 kHz, in particular 15 to 25 kHz. For this purpose, the vibration generating device has a generator and a converter with piezoelectric elements in a manner known per se. The converter is coupled to the oscillator. Linear oscillations are preferably generated in the direction of a longitudinal axis of the impulse transmission element. However, other forms of vibration, for example torsional vibrations, are not excluded and are also covered by the present invention.

According to a further preferred embodiment, the impulse transmission element is resiliently mounted in a direction opposite to the direction of action of the vibrations.

While the device according to the invention described above, which can be operated in a pulse transmission mode and a vibration coupling mode, is advantageous on its own, it goes without saying that further advantages are available in combination with the convex/concave configuration of the contact surfaces described above and with the configuration described above the end sections with a higher mass is particularly advantageous.

Thanks to the aforementioned features, reductions in feed forces by a factor of 10, for example from 40 kN to 4 kN, can be achieved with consistently high process quality and simple design.

Yet another aspect of the invention relates to a method for machining a workpiece or object. For this purpose, a device as described above is used. A tool is pressed against a workpiece or object. Vibrations, in particular ultrasonic vibrations, are generated on a working surface of a vibrator. An excitation surface of a pulse transmission element is subjected to the vibrations generated in this way. Pulses are transmitted from the excitation surface to a pulse transmission surface of the pulse transmission element opposite the excitation surface. The impulses are ultimately transferred from the impulse transfer surface to the workpiece or tool. The transmission can take place directly or indirectly via an intermediate piece or via another part of the tool. According to the invention, the device is operated in a pulse transmission mode in a first phase and in a vibration coupling mode in a second phase. In the vibration coupling mode, the vibration parameters and/or the contact pressure of the pressing device are different than in the pulse transmission mode. In particular, in the pulse transmission mode, the contact force and/or the amplitude of the vibration is greater than in the vibration coupling mode.

Preferably, a measurement can additionally be carried out in the method, in particular a measurement of the path traveled by the tool, the force acting on the tool or the workpiece, the frequency of the vibration and/or the power absorbed by the vibration generating device.

The switch from the pulse transmission mode to the oscillation coupling mode can then take place depending on the measured values. A switchover occurs in particular when a target path traveled by the tool, a target force acting on the tool is exceeded and/or when the power or frequency of the vibration generating device changes beyond a target value. This can be an absolute setpoint or a differential setpoint (increase per unit of time is above a setpoint).

Preferably, in a detachment mode following the vibration coupling mode, the contact pressure generated by the pressing device can be reduced and detachment vibrations can be used to prevent adhesion between the working surface of the oscillator and the excitation surface of the impulse transmission element or between the impulse transmission surface of the impulse transmission element and the workpiece or the tool or an intermediate piece.

Figur 1:

Schematische Darstellung einer erfindungsgemässen Vorrichtung,

Figur 2:

Schematische Darstellung einer erfindungsgemässen Vorrichtung gemäss einem ersten Aspekt der Erfindung,

Figuren 3a - 3e:

Verschiedene Ausführungen von erfindungsgemässen Anordnungen,

Figur 4:

Schematische Darstellung einer erfindungsgemässen Anordnung mit einer Anschlagfläche zur Aufnahme von Kräften,

Figur 5:

Schematische Darstellung einer erfindungsgemässen Vorrichtung mit einer federnden Rückstellvorrichtung,

Figur 6:

Schematische Darstellung der verschiedenen Komponenten einer erfindungsgemässen Vorrichtung,

Figuren 7a & 7b:

Verlauf der Leistung und Kraft in Abhängigkeit der Zeit und

Figuren 8a - 8c

Schematische Darstellung von verschiedenen Werkzeugen oder Werkstücken.

The invention is explained in more detail below in exemplary embodiments and with reference to the drawings. Show it:

Figure 1:

Schematic representation of a device according to the invention,

Figure 2:

Schematic representation of a device according to the invention according to a first aspect of the invention,

Figures 3a - 3e:

Various versions of arrangements according to the invention,

Figure 4:

Schematic representation of an arrangement according to the invention with a stop surface for absorbing forces,

Figure 5:

Schematic representation of a device according to the invention with a resilient reset device,

Figure 6:

Schematic representation of the various components of a device according to the invention,

Figures 7a & 7b:

Course of performance and power as a function of time and

Figures 8a - 8c

Schematic representation of various tools or workpieces.

Figure 1 schematically shows essential features of a device 1 according to the invention. The device 1 has a vibration generating device 20 and a pulse transmission element 11. According to Figure 1 the pulse transmission element 11 is part of a tool 10 for machining a workpiece 40. An optional intermediate piece 8 between the pulse transmission element 11 and the workpiece 40 is shown only schematically in dashed lines. The optional, schematically illustrated intermediate piece 13 can typically be a separate tool part (for example a perforating needle, see Figure 8a , or one Drill, see Figure 8c ) act. Without an intermediate piece 8, the tool 10 is formed exclusively by the impulse transmission element 11, for example when the tool 40 acts as a hammer.

The vibration generating device 20 has a vibrator 21. The oscillator 21 is provided with a work surface 22. The vibration generating device 20 (see also in detail Figure 6 ) has an ultrasonic generator, by means of which vibrations are generated in a manner known per se with a converter (not shown) with piezoelectric elements and can be transmitted to the oscillator 21.

The oscillator 21 is designed in such a way that vibration maxima occur in the area of the work surface 22 when vibration is stimulated. In an area in which vibration minima occur in a resonant oscillation operation (vibration nodes), the oscillator 21 is mounted via a fastening flange 24 in a schematically illustrated pressing device 30. With the pressing device 30, a contact pressure F can be exerted on the oscillator 21. In Figure 1 The amplitude with which the oscillator 21 oscillates is shown schematically on the left side. The working surface 22 is located at a distance λ/2 from an excitation surface (not shown) of the oscillator 21. The bearing at the vibration minimum (amplitude almost zero) is at a distance λ/4 from an excitation surface. The oscillator 21 is designed as a longitudinal sonotrode in a manner known per se.

The pulse transmission element 11 has an excitation surface 12. During operation, the excitation surface 12 can be brought into contact with the working surface 22 of the oscillator 21. A pulse transmission surface 13 is arranged on the side of the pulse transmission element 11 opposite the excitation surface 12. From The pulse transmission surface 13 transmits pulses directly or indirectly to the workpiece 40 or to the intermediate piece 8. Figure 1 is to be understood as a schematic representation of the device according to the invention for explanation. The individual aspects of the invention are explained below with reference to the other figures.

Figure 2 shows a first exemplary embodiment according to the invention. The oscillator 21 is concave in a central section 23 on its work surface 22. The pulse transmission element 11 is convex in a central section 14 on its excitation surface 12. The radii of curvature R1 and R2 of the working surface 22 or excitation surface 12 are chosen to be essentially the same. However, it is also conceivable to make the radius of curvature R2 of the excitation surface 12 smaller. In Figure 2 the complete work surface and the complete excitation surface 12 are concave and convex, respectively. However, it is also conceivable to make only the central sections 14 and 23 curved. This can also be used to achieve the desired centering effect.

The pulse transmission element 11 has a cross-sectional taper 45. This leads to the cross section in an end section 15 adjacent to the excitation surface 12 (with diameter D seen perpendicular to the longitudinal axis L) being larger than in a middle section 16 and in an end section 17 (with diameter d). This results in the mass of the end section 15 over a length 11 being greater than the respective masses of the middle section 16 (on the same length l2) and the end section 17 adjacent to the impulse transmission surface 13 (on the same length l3). This improves impulse transmission. However, it is also conceivable to provide a section with an enlarged cross-section between the middle section 16 and the end section 17 (in Figure 2 not shown) if the mass of the end section 17 is to be increased.

The pulse transmission element 11 is also provided with schematically shown slots 41a and/or ribs 41b. It is conceivable to provide one or more slots 41a but no ribs, one or more ribs 41b (but no slots), or combinations of ribs and slots.

Figures 3a - 3e show various alternative embodiments of devices according to the invention in the area of the interface between oscillator 21 and pulse transmission element 11. According to Figure 3a the working surface 22 of the oscillator 21 is provided with a blind hole 26. The excitation surface 12 of the pulse transmission element 11 is also provided with a blind hole 43. A centering bolt 42 can be inserted into the two blind holes 26, 43. In Figure 3a a concave/convex configuration of the work surface 22 and the excitation surface 12 is shown. When using a centering bolt 42, these surfaces can alternatively also be flat. In Figure 3a A cross-sectional taper 45 is also shown, similar to that in Figure 11.

Figure 3b shows an oscillator 21, which is also provided with a blind hole 26. In contrast to the exemplary embodiment according to Figure 3a the excitation surface 12 of the pulse transmission element 11 is continuous and without a blind hole. Instead, the outer diameter of the pulse transmission element 11 in the end section 15 adjacent to the excitation surface 12 is designed so that it fits into the blind hole 26 in the oscillator 21. This also allows centering to be created.

Figure 3c shows schematically an oscillator 21, which is provided with a translation section 25. Due to a cross-sectional reduction in the area of the translation section 25, the oscillator 21 is created in a manner known per se Amplitude transformation. The desired vibration amplitude on the work surface 22 can be defined in this way.

Figure 3d shows a pulse transmission element 11, in which inserts 19a, 19b are inserted into a base body 18 at the two end sections 15 in the area of excitation surface 12 or pulse transmission surface 13. The base body is typically made of steel or titanium. However, other materials such as ceramics are conceivable. The inserts 19a, 19b are made of a heavier material, typically tungsten. The inserts are inserted into the base body 18 using any connecting mechanisms known to those skilled in the art, for example pressed in, glued in or screwed in. It is important that in order to increase the mass in the end regions 15 and 17, the material of the inserts 19a, 19b has a higher density than the material of the base body 18. Of course, it is conceivable to only provide corresponding inserts on one of the end sections 15, 17 . In Figure 3d an insert 27 is also shown in the area of the work surface 22 of the oscillator 21. The insert 27 is in particular made of a more resistant material, which means that wear on the oscillator 21 can be reduced.

Figure 3e shows an alternative arrangement in which the working surface 22 of the oscillator 21 is convex and the excitation surface 12 of the impulse transmission element is concave. The radius of curvature R1 of the working surface 22 of the oscillator 21 is the same as the radius of curvature R2 of the excitation surface 12 of the pulse transmission element 11.

According to a preferred embodiment, the oscillators 21 shown above are operated at a frequency of 25 kHz. The length of the pulse transmission element 11 in this exemplary embodiment is 75 mm, with the lengths l1, l2 and l3 of the sections 15, 16, 17 each being 25 mm. The diameter d of the pulse transmission element 11 in the area of the pulse transmission surface 13 is 7.5 mm. The diameter D of the excitation surface 12 is approximately 9.4 mm (see Figure 2 ). The cross-sectional area of the excitation area is therefore approximately 150% of the cross-sectional area of the impulse transfer area 13.

Typical oscillation widths (i.e. double amplitudes) in the area of the working surface 22 are 100 μm.

Typical power recorded by the oscillator 21 is around 2 kW.

In the case of a coupling between pulse transmission mode and oscillation coupling mode (if the operating parameters are not changed), the power consumed can increase from 2 kW to 6 kW in a short time (typically over half a second).

Figure 4 shows schematically a pulse transmission element 11, which is provided with a stop surface 44. If the pulse transmission element 11 is due to the pressing device 30 (see Figures 1 and 6 ) generated feed force has been moved along a predetermined path, the stop surface 44 comes into contact with a stop surface 31 of a schematically shown stop element. The stop surface 44 is arranged at a distance λ/4 (measured from the wavelength of the longitudinal oscillation of the oscillator 21) from the excitation surface 12. This results in operation in a vibration coupling mode (see the following explanations). Figures 7a and 7b ) a vibration node in the area of the stop surface 44 and therefore virtually no losses due to the stop. When the stop surface 44 comes into contact with the stop surface 31, the force exerted by the impulse transmission element 11 on the tool 10 and/or workpiece 40 no longer increases to, but is reduced. Coupling of the vibrations from the pulse transmission element 11 to the tool 10 or workpiece 40 is thereby prevented.

Figure 5 shows another alternative embodiment of a storage of a pulse transmission element 11 according to the invention. The pulse transmission element 11 has a similar structure as described above Figure 2 described a cross-sectional taper 45. A restoring element 47 is resiliently mounted and has a receptacle 48, the shape of which is adapted to the outer shape of the impulse transmission element 11. At the end of the machining process, the pulse transmission element 11 can be retrieved with the restoring element 47. As a result, any undesirable adhesions that may occur between the pulse transmission element 11 and the workpiece 10 or tool 40 can be resolved. It is important that the restoring element 47 can generate a restoring force directed counter to the direction of action E of the vibration. The restoring element 47 is part of a restoring unit 33, which can be designed passively (resilient mounting) or which can be made by the reference to Figure 6 Control unit 2, described in detail below, can be actively operated.

Figure 6 shows schematically the individual components of the device 1 according to the invention and the type of their interaction. The device 1 is controlled centrally by a control device 2. The control device 2 controls the operation of an ultrasonic generator 3. If necessary, the ultrasonic generator 3 returns information regarding frequency and power to the control unit 2, so that the control unit 2 can control the operation according to these values. The ultrasonic generator 3 operates the oscillator 20 by exciting piezoelectric elements (not shown) in a manner known per se.

The control device 2 also controls the pressing device 30, which exerts the contact pressure F on the oscillator 21. The device 1 also has a measuring unit 32. With the measuring unit 32, in particular, the feed path of the oscillator 21 or also of the pulse transmission element 11 or a tool 10 can be measured. The measuring unit 32 can also be part of the generator 3 and measure the power consumed by the oscillator 21. It is also conceivable to integrate the generator and control device 2 in one component. The control device 2 is used to operate the device 1 according to different operating modes. These are referred to Figures 7a and 7b explained in more detail.

In a transient phase ES, a contact force F _PRESS is built up by the pressing device 30 and the oscillation in the oscillator 21 is generated by the generator 3. After the transient phase ES, the device 1 is operated in a pulse transmission mode I. For this purpose, the pressing device 30 exerts a substantially constant contact force F _PRESS on the oscillator 20 (see FIG. 7b). Due to this contact force F _PRESS , a feed is transmitted to the impulse transmission element 11 and to the workpiece 40 or tool 10. There is a continuous feed while simultaneously applying ultrasonic vibrations to the pulse transmission element 11 and the tool/workpiece. In Figure 7a the power P emitted by the generator and received by the oscillator 21 is shown over time. As long as the device 1 operates in pulse transmission mode I, the power P consumed remains essentially constant. If the distance traveled by the tool 10 or workpiece 40 exceeds a certain value, that is, if the tool 10 or workpiece 40 comes to a stop, for example, the power consumed increases due to vibrations being coupled into the tool/workpiece. At this switching time t _U, the operation of the generator 3 is switched to a vibration coupling mode S. As a result, the power consumed (see curve 1 shown in dashed lines) decreases again in contrast to a hypothetical power consumption without switching (curve 2 shown in dashed lines). The switching time tU is triggered by the measuring unit 32 as explained above. In particular, switching occurs when the power increase per unit of time (dP/dt) is above a certain value.

While it is conceivable to reduce the power P by reducing the generator power, the contact force F _PRESS is preferably reduced. Figure 7b shows schematically the contact pressure F _PRESS , which is generated by the pressing device 30 and the force F _WS acting on the workpiece 40 over time. After the transient phase ES, the contact force F _PRESS generated by the pressing device 30 during the pulse transmission mode I is essentially identical to the force F _WS transmitted to the workpiece 40. At the switching time tU, it is conceivable to keep the contact pressure F _PRESS generated by the pressing device 30 constant (see dashed line 1), but to keep a part of the acting force in the above with reference to Figure 4 to accommodate the arrangement explained by a stop surface 31. As a result, the force F _WS acting on the workpiece 40 is suddenly reduced (see solid line 2). Only a fraction of the contact force F _PRESS applied by the pressing device 30 is transferred to the workpiece 40. However, it is also conceivable to continuously reduce the contact pressure F _PRESS generated by the pressing device 30 (see dashed line 3) without using a stop element. In this case, the force F _WS acting on the workpiece 40 in turn corresponds to the contact pressure F _PRESS generated by the pressing device 30 (see dashed line). As explained above, the switching between pulse transmission mode I and vibration coupling mode S takes place actively when certain target values are reached or passively when the stop surface 44 is at the corresponding stop surface 31. However, combinations are also conceivable: In particular, it is conceivable to reduce the contact pressure F _PRESS of the pressing device 30 and/or the power of the generator 3 if it is determined that the stop surface 44 abuts the stop surface 31.

At the end of the oscillation coupling phase S (see Figure 7a ) a release phase L takes place. In the release phase L, the contact pressure F _PRESS generated by the pressing device 30 is (further) reduced and release oscillations are given to the oscillator 21. In this phase L or at the end of the vibration coupling phase S, the workpiece can also relax due to the vibrations introduced.

Figures 8a - 8c show examples of various workpieces 40 and tools 10. According to Figure 8a a hole is made in a workpiece 40 in the form of a plate using a tool 10 in the form of a needle. Of course, tools with several needles 10 are also conceivable and a matrix-like perforation structure can be introduced into the workpiece 40. For example, filter applications or the production of porous membranes are conceivable.

Figure 8b shows a tool 10 in the form of a punch rivet. With the punch rivet 40, which also has anchoring ribs 39, different layers 46a, 46b, 46c can be connected to one another. This allows composite materials, such as lightweight construction elements, to be produced.

Figure 8c shows a tool 10 in the form of a drill, by means of which a drill hole is to be made in a workpiece 40. With reference to those in the Figures 7a and 7b The following should be noted in the pulse transmission phases I and oscillation coupling phases S explained: In the embodiment according to Figure 8a A switchover typically occurs when the tool 10 has traveled a predetermined distance Δl. The switchover in the exemplary embodiment according to Figure 8b occurs when the head of the punch rivet 40 comes into contact with the top layer 46a, which leads to an increase in the power consumed by the oscillator 21, which can be detected by the generator 3. According to Figure 8c A switchover occurs when the drill 10 has been advanced by a predetermined feed path Δl or even if an increase in the power absorbed by the oscillator 21 is detected due to the drill tip hitting an obstacle 49 (for example material of greater density). In particular if the switching is to take place when a predetermined path Δl is reached (see Figures 8a or 8c ) or if the tool 40 according to Figure 8b should not be brought into position, switching can be done passively using the in Figure 4 described combination of stop surface 44 and stop surface 31.

Claims (17)

1. Device (1) for machining workpieces (40) or objects, comprising

   - a tool (10) by means of which the workpiece (40) or the object can be machined,

   - a pressing device (30) by means of which the tool (10) can be pressed against the workpiece (40) or the object,

   - a vibration generating device (20) with a vibrator (21) for generating vibrations on a working surface (22) of the vibrator (21), in particular ultrasonic vibrations, and

   - a pulse transmission element (11) with an excitation surface (12) and a pulse transmission surface (13) opposite the excitation surface (12), wherein the excitation surface (12) can be brought into contact with the working surface (22) of the vibrator (21), and wherein in particular the working surface (22) of the vibrator (21) is concave and the excitation surface (12) of the pulse transmission element (11) is convex or the working surface (22) of the vibrator (21) is convex and the excitation surface (12) of the pulse transmission element (11) is concave, and

   wherein the pulse transmission surface (13) can be brought into contact with the tool (10), the workpiece (40) or an intermediate piece (8), so that vibrations can be transmitted from the vibration generating device (20) to the workpiece (40) or tool (10) by means of the pulse transmission element (11),

   characterized in that

   a centering arrangement is provided between the vibrator (21) and the pulse transmission element (11),

   wherein the pulse transmission element (11) has a greater mass in an end section (15) of a certain length (l1) adjacent to the excitation surface (12) and/or in an end section (17) of the same length (l3) adjacent to the pulse transmission surface (13) than in a central section (16) of the same length (l2) between the end sections (15, 17).
2. Device (1) according to claim 1,

   wherein the concave working surface (22) of the vibrator (21) has, in a central portion (23), a radius of curvature (R1) which is greater than or equal to the radius of curvature (R2) in a central portion (14) of the convex excitation surface (12) of the pulse transmission element (11), or

   wherein the convex working surface (22) of the vibrator (21) has a radius of curvature (R1) in a central portion (23) which is smaller than or equal to the radius of curvature (R2) in a central portion (14) of the concave excitation surface (12) of the pulse transmission element (11).
3. Device (1) according to any one of claims 1 and 2, wherein the excitation surface (12) and/or the pulse transmission surface (13) has a larger cross section and/or a larger density than the central section (16).
4. Device (1) according to claim 3, wherein the pulse transmission element (11) substantially consists of a base body (18) of a first material and in at least one end section (15, 17) adjacent to the excitation surface (12) and/or the pulse transmission surface (13) an insert (19a, 19b) of a second material, in particular tungsten, is inserted into the base body (18), the second material having a higher density than the first material.
5. Device according to any of claims 3 and 4, wherein the cross section of the excitation surface (12) is at least 150% of the cross section of the pulse transmission surface (13).
6. Device (1) for processing workpieces (40) or objects according to any of claims 1 to 5,
   characterized in that the device (1) is operable in a first pulse transmission mode (I) and in a second vibration coupling mode (S), wherein in the vibration coupling mode (S) the vibration parameters and/or the pressing force (F) of the pressing device (30) are different than in the pulse transmission mode (I), wherein in particular in the pulse transmission mode (I) the pressing force (F) and/or the amplitude of the vibration is greater than in the vibration coupling mode (S).
7. Device according to claim 6, wherein the device (1) has a stop surface (31) on which the pulse transmission element (11) can be supported in the vibration coupling mode (S).
8. Device according to any one of claims 6 and 7, wherein the device comprises a measuring unit (32) for measuring the distance travelled by the tool (10), the force acting on the tool (40), the frequency of the vibration and/or the power absorbed by the vibration generating device (20), and wherein the device (1) comprises a control unit (2) which switches the operation of the device from the pulse transmission mode (I) to the vibration coupling mode (S) as a function of the measured values of the measuring unit (32), in particular when a set path covered by the tool (10), a set force acting on the tool (10) and/or when the power or the frequency of the vibration generating device (20) changes above a set value.
9. Device according to claim 8, wherein the control unit (2) is designed in such a way that the device (1) can be operated in a third release mode (L) after the vibration coupling mode (S), wherein in the release mode (L), the pressing force (F) generated by the pressing device (30) is reduced and release vibrations can be generated with the vibration generating device (20).
10. Device according to any one of claims 1 to 9, wherein the tool (10) is selected from the group consisting of drill, hammer, punch, rivet transformer, perforation needle.
11. Device according to one of claims 1 to 10, wherein the pulse transmission element (11) has a length of 5 to 200 mm, preferably 50 to 100 mm, in particular preferably 60 to 80 mm and/or a diameter in the region of the pulse transmission surface (13) of 5 to 15 mm, preferably 6 to 10 mm, in particular 7 to 8 mm.
12. Device according to one of claims 1 to 11, wherein the pulse transmission element (11) is provided with slots (41a) and/or reinforcing ribs (41b).
13. Device according to one of the claims 1 to 12, wherein vibration generating device (20) is designed for generating vibrations with a frequency of 10 to 30 kHz, in particular 15 to 25 kHz, in particular linear vibrations in the direction of a longitudinal axis (L) of the pulse transmission element (11).
14. Device according to one of claims 1 to 13, wherein the pulse transmission element (11) is mounted so as to vibrate in a direction opposite to the direction of action (E) of the vibrations.
15. Method for machining workpieces (40) or objects, with a device (1) according to one of claims 1 to 14, comprising the steps of

    - pressing a tool (10) against a workpiece (40) or an object by means of a pressing device (30),

    - generating vibrations on a working surface (22) of a vibrator (21), in particular ultrasonic vibrations,

    - applying the generated vibrations to an excitation surface (12) of a pulse transmission element (11),

    - transmitting pulses from the excitation surface (12) to a pulse transmission surface (13) of the pulse transmission element (11) opposite the excitation surface (12),

    - transmitting the pulses from the pulse transmission surface (13) to the workpiece (40) or the tool (10),

    wherein the device is operated in a first phase in a pulse transmission mode (I) and in a second phase in a vibration coupling mode (S), wherein in the vibration coupling mode (S), the vibration parameters and/or the pressing force (F) of the pressing device (30) are different than in the pulse transmission mode (I), that in particular in the pulse transmission mode (I) the contact force (F) and/or the amplitude of the vibration is greater than in the vibration coupling mode (S).
16. Method according to claim 15, comprising the further steps of

    - measuring the distance travelled by the tool (10), the force acting on the tool (10), the frequency of the vibration and/or the power absorbed by the vibration generating device (20),

    - switching from the pulse transmission mode (I) to the vibration coupling mode (S) as a function of the measured values, in particular when a set path covered by the tool (10), a set force acting on the tool (10) and/or when the power or the frequency of the vibration generating device (20) is changed above a set value.
17. Method according to any one of claims 15 and 16, comprising the further steps of

    - reducing the pressing force (F) generated by the pressing device (30) in a release mode (L) following the vibration coupling mode (S),

    - generating releasing vibrations to prevent adhesion between the working surface (22) of the vibrator (21) and the excitation surface (12) of the pulse transmission element (11) or between the pulse transmission surface (13) of the pulse transmission element (11) and the workpiece (40), the tool (10) or an intermediate piece (8).

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