EP4335559A1 - Method and device for ultrasonic deburring of an object - Google Patents

Abstract

The invention relates to a device and a method for ultrasonic deburring of an object, in which ultrasound is generated via an ultrasound generator and introduced into an object to be deburred via a sonotrode located in an ultrasound transmission medium, the sonotrode being at a defined distance between a working surface at the tip of the Sonotrode and the surface of the object to be deburred located at this distance in front of this work surface and this work surface of the sonotrode is aligned in a defined manner relative to the surface of the object in such a way that the surface normal of this work surface of the sonotrode points at a predetermined angle to the surface to be deburred Object is aligned, in which Rayleigh waves are generated in the surface of the object, using a sonotrode which has at least one flat working surface, the surface normal of which is inclined relative to the main axis of the sonotrode. This makes possible in contrast to previously used devices and methods for ultrasonic deburring also ultrasonic deburring of areas that were previously difficult or impossible to access, especially on the inner surfaces of an object.

Description

The invention relates to a method and a device for ultrasonic deburring of an object.

A device and a method for ultrasonic deburring of an object are in the DE102016101313A1 and the DE102019006919B3 disclosed. An ultrasonic generator generates ultrasonic vibrations, which are introduced via a working surface on the tip of the sonotrode facing the object to be deburred into an ultrasonic transmission medium, which transmits the vibrations to the object to be treated.

In liquids (and gases), sound only propagates in the form of longitudinal pressure waves, i.e. through alternating areas of higher and lower pressure. If the vapor pressure of the liquid locally falls below, bubbles spontaneously form. This is called cavitation. If the ambient pressure increases, the bubble shrinks and can implode, which then creates a shock wave in the liquid. If this shock wave hits a solid surface, cavitation erosion can occur there.

Solids have specific tensile strengths. If they are stressed beyond that, they break. The tensile strength decreases with the number of loads. Failure occurs even earlier if there is previous damage such as notches. This is the case at the transition between a ridge and the surface of a component. Ultrasound oscillates in the kilohertz range and an oscillation stimulated by ultrasound loads such predetermined breaking points on burrs several thousand times per second and, after a suitable duration and strength of the oscillation, leads to the burr breaking off.

Essential criteria for the deburring effect of the device according to the DE102016101313A1 are according to [Direkt2017 = http://trends.directindustry.de/weberultrasonics/project-22604-144007.html; accessed on October 6, 2019] the amplitude, power and frequency of the ultrasound as well as the distance to the workpiece and the treatment time. Setting these operation-specific parameters makes it possible to carry out the entire spectrum from micro to coarse deburring on components made of aluminum or zinc alloys.

Another important criterion for the deburring effect is in the DE102019006919B3 the orientation of the sonotrode relative to the surface of the object to be deburred is revealed. With a suitable choice of this orientation and the resulting angle of impact of the sound waves, so-called Rayleigh waves form on and in the surface of the object to be deburred. At a material-specific Rayleigh impact angle, such Rayleigh waves form in maximum strength and a resonance catastrophe occurs. This effect also allows the deburring of high-strength materials and can be explained as follows:
If a sound wave strikes the interface between two media at an angle, one part is reflected at the interface into the first medium and the other part penetrates into the second medium. The penetrating sound wave is refracted. In solid bodies, due to the torsional forces that occur during sound transmission, a transverse sound wave (also called shear or shear wave) is also generated by the longitudinal sound wave (also called pressure wave). Depending on the type of solid, total reflection occurs from a specific impact angle, so that only transverse waves propagate in the solid. In a transition area, so-called Rayleigh waves (earthquake waves) can spread on and in the surface of solid bodies. Their movement corresponds to an elliptical superposition of transverse and longitudinal vibration components. The intensity of Rayleigh waves decreases exponentially with penetration depth. However, Rayleigh waves cause strong tensions on the surface.

wobei v_L die materialspezifische Schallgeschwindigkeit der auftreffenden Longitunalwellen und v_R die materialspezifische Schallgeschwindigkeit der angeregten Rayleighwellen bezeichnet.As mentioned above, the strength of the Rayleigh waves depends largely on a material-specific angle of impact of the sound waves on the surface of the object, whereby both the material of the liquid ultrasound transmission medium (usually water) and that of the object to be deburred play a role. The maximum occurs when the incident longitudinal waves in the surface of the object excite Rayleigh waves in such a way that a resonance catastrophe occurs. This is the case with a material-specific impact angle α of $$\mathrm{\alpha }={\sin }^{-1}\left({\mathrm{v}}_{\mathrm{L}}/{\mathrm{v}}_{\mathrm{R}}\right)$$

where v _L denotes the material-specific sound speed of the incident longitudinal waves and v _R denotes the material-specific sound speed of the excited Rayleigh waves.

The superposition of Rayleigh waves excited in the surface of the object to be deburred with the longitudinal pressure waves and implosion-induced shock waves known from the prior art in the ultrasonic transmission fluid leads to a significantly increased load on the surface per unit of time and thereby also enables ultrasonic deburring of high-strength materials.

However, a suitable alignment of the sonotrode relative to the surface of the object to be deburred that is to be acted upon can only be achieved with difficulty or not at all in the case of components with more complex geometry, in particular in the case of burrs located in undercuts and bores or otherwise hidden.

It is therefore the object of the invention to provide a method and a device for ultrasonic deburring of an object, which expand the range of applications of ultrasonic deburring to such hard-to-reach burrs.

The task is related to the method for ultrasonic deburring of an object in which ultrasound is generated via an ultrasound generator and introduced into an object to be deburred via a sonotrode located in an ultrasound transmission medium, the sonotrode being at a defined distance between a working surface at the tip of the sonotrode and the at this distance in front of this work surface of the object to be deburred is arranged, and this work surface of the sonotrode is aligned in a defined manner relative to the surface of the object to be deburred, such that the surface normal of this work surface of the sonotrode is at a predetermined angle to the one to be deburred Surface of the object is aligned, in which Rayleigh waves are generated in the surface of the object, solved according to the invention by using a sonotrode which has at least one flat working surface, the surface normal of which is inclined relative to the main axis of the sonotrode.

Such a method according to the invention for ultrasonic deburring of an object makes this possible through the use of a sonotrode with a flat work surface inclined in this way relative to the main axis of the sonotrode required impact of the sound waves at the material-specific impact angle on the surface of the object to be deburred, even if this surface is in an area of the object that is difficult to access, since the entire sonotrode does not have to be aligned accordingly (which is often the case due to its spatial dimensions). is not possible) but only the flat working surface of the sonotrode needs to be aligned.

The desired impact angle is set in such a way that first the position of the area to be deburred and its accessibility is determined with a sonotrode tip and then a sonotrode with a working surface at a suitable inclination relative to the main axis of the sonotrode is used and positioned appropriately so that the of The sound waves emanating from it hit the area of the object to be deburred at the desired impact angle. To do this, the sonotrode can be inserted into the area that is difficult to access, e.g. into a hole, and the angle of impact can be readjusted if necessary by tilting the sonotrode.

As a result of its vibrations, the inclined working surface of the sonotrode stimulates the emission of longitudinal sound waves in the direction of its surface normal, i.e. inclined to the main axis of the sonotrode. A flat work surface inclined in this way (compared to a usual flat work surface arranged perpendicular to the main axis of the sonotrode) has a reduced sound power (depending on the degree of inclination) in the direction of its surface normal (since part of the sound power is always emitted in the direction of the main axis of the sonotrode but the advantage of better accessibility to hidden areas that are otherwise difficult or even impossible to reach far compensates for this disadvantage. Furthermore, the reduced sound power in the direction of the surface normal of the flat work surface can also be compensated for by increasing the power introduced into the sonotrode.

What is essential here is the flat design of the working surface at the sonotrode tip. Our own experiments have shown that with a curved work surface, in particular a hemispherical sonotrode tip, sufficient sound power cannot be introduced into the area of the object to be deburred. Apparently a curved work surface generates overlapping and mutually disruptive sound waves that are not suitable for the desired deburring.

The method according to the invention for ultrasonic deburring of an object proves to be particularly advantageous if a sonotrode is used which has at least one flat working surface, the surface normal of which is inclined at an angle between 20° and 45° relative to the main axis of the sonotrode.

This represents a good compromise between the improved accessibility of hidden areas and the reduced sound output in the target direction of a work surface that is inclined relative to the main axis of the sonotrode.

In a further advantageous embodiment, the method according to the invention for ultrasonic deburring of an object proves to be used when a sonotrode is used which has at least two flat working surfaces, the respective surface normal of which is inclined in relation to the main axis of the sonotrode, preferably by an angle between 20° and 45° is inclined.

This allows two areas to be deburred to be exposed to sound at the same time, thereby speeding up the process considerably.

Good results are achieved if the two areas to be deburred are located in an area of the object (hidden from the outside) (e.g. in a hole) in such a way that the sonotrode tip can be positioned at the same distance from both areas to be deburred and the respective surface normals are both Flat work surfaces are each aligned with one of the two areas to be deburred and there is no shadowing of the sound waves emitted from them in the direction of the areas to be deburred.

In a particularly advantageous embodiment of the method according to the invention, a sonotrode is used whose at least two flat working surfaces are located on two opposite sides of the sonotrode tip. The work surfaces are then arranged on the tip of the sonotrode in the manner of a gable roof. With such an arrangement, the mutual influence of the sound waves emanating from the two work surfaces is minimal and the deburring effect is optimal.

The arrangement of the two opposing working surfaces on the sonotrode tip, ie the inclination of their respective surface normals to the main axis of the sonotrode, is important (depending on the spatial arrangement of the surface to be deburred Areas within the difficult-to-access area of the object) should be designed in such a way that (when the sonotrode tip is positioned at a suitable distance between the two areas to be deburred) the sound waves emanating from the respective work surface strike the respective area to be deburred at the required material-specific impact angle. Depending on the spatial arrangement of the areas to be deburred within the difficult to access area of the object, an equal or different inclination of the respective surface normals of the two work surfaces can be advantageous.

This principle can be extended to other areas to be deburred, in which case an inclined, flat work surface must be provided for each area to be deburred at the same time. The sonotrode tip is then designed in the form of a three- or four-sided pyramid, for example for three or four areas to be deburred. However, as the number of work surfaces increases, mutual influences and interference with the sound waves they emit also occur. Our own experiments have shown that good deburring can still be achieved with a sonotrode tip in the shape of a four-sided pyramid, i.e. with four working surfaces.

In a further advantageous embodiment of the method according to the invention for ultrasonic deburring of an object, a sonotrode is used whose cross section at its tip perpendicular to its main axis is adapted to the cross section of an inner region of the object to be deburred.

For example, if the inside of a keyhole or its guide slot is to be deburred, a sonotrode is particularly suitable whose cross section at its tip perpendicular to its main axis is adapted to the cross section of the guide slot in such a way that the sonotrode (when positioned within the guide slot). each side of the guide slot has just the defined distance between each of the at least one work surface at the tip of the sonotrode and the surface of the guide slot to be deburred, which is located perpendicular to this work surface. For the deburring of a usual guide slot (such as for a locking cylinder) with a (essentially) rectangular cross-sectional geometry with significantly longer long sides than broad sides, it is sufficient if only the two long sides of the sonotrode tip, which is also rectangular in cross section, have a working surface. If the length of the broad sides of the cross section is greater However, it is advantageous if the two broad sides of the sonotrode tip, which is rectangular in cross section, also have a working surface.

This shape adjustment allows simultaneous deburring of the entire inner circumference of the guide slot and thus a considerable acceleration of the process compared to using a sonotrode with only one working surface, which must be positioned separately at the defined distance and aligned with the areas of the guide slot to be deburred.

The task is related to the device for ultrasonic deburring of an object comprising an ultrasonic generator, a sonotrode, a device for receiving an object to be deburred and a device for the defined adjustment of the distance between a work surface at the tip of the sonotrode and the one located at this distance in front of this work surface surface of the object to be deburred and a device for the defined alignment of this working surface of the sonotrode relative to the surface of the object to be deburred, such that the surface normal of this working surface of the sonotrode can be aligned at a predetermined angle to the surface of the object, solved according to the invention in that the sonotrode has at least one flat working surface, the surface normal of which is inclined relative to the main axis of the sonotrode. During operation of the device, this results in a sound wave emitted by at least one inclined flat work surface striking the surface of the object at a predeterminable angle.

Such a device according to the invention for ultrasonic deburring of an object also enables the deburring of areas of the object that are difficult to access due to the flat working surface of the sonotrode inclined according to the invention and its orientation relative to the surface of the object, which was otherwise not possible in an ultrasound treatment device according to the prior art.

In an ultrasonic treatment device according to the prior art, the entire sonotrode must be aligned in such a way that the sound wave emitted by it hits the surface of the object to be deburred at a material-specific impact angle, and this is in difficult to access areas such as a hole due to the dimensions the sonotrode is usually not possible. In contrast, the one according to the invention Device has a sonotrode with an inclined work surface, the inclination of which relative to the main axis of the sonotrode ideally already corresponds to the material-specific impact angle, so that no further alignment of the sonotrode and thus also of its work surface is required. Otherwise, that is, if the angle of impact on the surface of the object to be deburred resulting from the inclination of the work surface does not correspond to the material-specific angle of impact of the object, all that is required is a mostly minor readjustment of the alignment of the sonotrode, which is necessary in most areas that are difficult to access despite the Dimensions of the sonotrode is still possible.

What is essential here is the flat design of the work surface. Our own experiments have shown that with a curved work surface, especially a hemispherical one, sufficient sound power cannot be introduced into the area of the object to be deburred. Apparently a curved work surface generates overlapping and mutually disruptive sound waves that are not suitable for the desired deburring.

The device according to the invention for ultrasonic deburring of an object proves to be particularly advantageous if it has a sonotrode with at least one flat working surface, the surface normal of which is inclined at an angle between 20° and 45° relative to the main axis of the sonotrode.

This represents a good compromise between the improved accessibility of hidden areas and the reduced sound output in the target direction of a work surface that is inclined relative to the main axis of the sonotrode.

It is further advantageous if the device according to the invention for ultrasonic deburring of an object has a sonotrode with at least two flat working surfaces, the respective surface normal of which is inclined relative to the main axis of the sonotrode, preferably inclined at an angle between 20° and 45°.

This allows two areas to be deburred to be exposed to sound at the same time, thereby significantly improving the effectiveness of the device.

In a particularly advantageous embodiment of the device according to the invention, the sonotrode has at least two flat working surfaces, which are located on two of each other opposite sides of the sonotrode tip. The work surfaces are then arranged on the tip of the sonotrode in the manner of a gable roof. With such an arrangement, the mutual influence of the sound waves emanating from the two work surfaces is minimal and the deburring effect is optimal.

Depending on the spatial arrangement of the areas to be deburred within the difficult-to-access area of the object, an equal or different inclination of the respective surface normals of the two work surfaces can be advantageous.

This principle can be extended to other areas to be deburred, in which case an inclined, flat work surface must be provided for each area to be deburred at the same time. The sonotrode tip is then designed in the form of a three- or four-sided pyramid, for example for three or four areas to be deburred. However, as the number of work surfaces increases, mutual influences and interference with the sound waves they emit also occur. Our own experiments have shown that good deburring can still be achieved with a sonotrode tip in the shape of a four-sided pyramid, i.e. with four working surfaces.

In a further advantageous embodiment of the device according to the invention for ultrasonic deburring of an object, it has a sonotrode, the cross section of which is adapted at its tip perpendicular to its main axis to the cross section of an inner region of the object to be deburred.

If the device is to be used, for example, for deburring the inside of a keyhole or its guide slot, a sonotrode is particularly suitable whose cross section at its tip perpendicular to its main axis is adapted to the cross section of the guide slot in such a way that the sonotrode (when positioned within the guide slot) on each side of the guide slot has just the defined distance between each of the at least one work surface at the tip of the sonotrode and the surface of the guide slot to be deburred, which is located perpendicular to this work surface. For the deburring of a usual guide slot (such as for a locking cylinder) with a (essentially) rectangular cross-sectional geometry with significantly longer long sides than broad sides, it is sufficient if only the two long sides of the sonotrode tip, which is also rectangular in cross section, have a working surface. At However, due to the larger length of the broad sides of the cross section of the guide slot, it is advantageous if the two broad sides of the sonotrode tip, which is rectangular in cross section, also have a working surface.

This shape adjustment of the sonotrode tip allows simultaneous deburring of the entire inner circumference of the guide slot and thus a significantly improved efficiency of the device compared to a device with a sonotrode with only one working surface, which are each positioned separately at the defined distance and aligned with the areas of the guide slot to be deburred must.

The device according to the invention and the method according to the invention for ultrasonic deburring of an object are explained in more detail below using an exemplary embodiment:
According to the exemplary embodiment, ultrasound is generated via an ultrasound generator and introduced into an object to be deburred via a sonotrode located in an ultrasound transmission medium, the sonotrode being at a defined distance between a work surface at the tip of the sonotrode and the one to be deburred at this distance in front of this work surface Surface of the object is arranged and this working surface of the sonotrode is aligned in a defined manner relative to the surface of the object to be deburred, such that the surface normal of this working surface of the sonotrode is aligned at a predeterminable angle to the surface of the object to be deburred, and according to the invention A sonotrode is used that has two flat work surfaces at its tip.

This sonotrode is specially designed for deburring the inside of the guide slot of a locking cylinder with a cross section of 7.5 by 2.5 mm ² and accordingly the cross section of the sonotrode tip is rectangular with a length of 6.5 mm and a width of 1, 9mm. Only the two long sides of the sonotrode tip are beveled and designed as inclined, flat working surfaces, the respective surface normal of which is inclined by 30° relative to the main axis of the sonotrode, so that the sonotrode tip has the shape of a gable roof.

The angle of inclination of the two working surfaces at the sonotrode tip corresponds to the material-specific impact angle of the locking cylinder material.

As a result, no further alignment of the sonotrode is required relative to the inner surface of the guide slot of the locking cylinder to be deburred, but the sonotrode can simply be inserted centrally into the guide slot of the locking cylinder at a uniform speed and thereby operated. Due to this central positioning of the sonotrode within the guide slot and the above-mentioned dimensions of the sonotrode and the guide slot, both working surfaces of the sonotrode have just the required distance from the inner surface of the guide slot to be deburred.

During operation of the sonotrode, the two working surfaces of the sonotrode are thus suitably spaced and aligned so that the ultrasonic waves emitted by them are introduced into the surface of the guide slot to be deburred at an angle of inclination to the surface, in which Rayleigh waves of maximum strength are generated in the surface of the guide slot. According to the exemplary embodiment, water is used as the ultrasound transmission medium.

Ultrasound is transmitted via the ultrasonic transmission medium with a frequency of 20 kHz and an effective power of the sonotrode of 300 W and a distance of the respective work surface from the inner wall of the guide slot to be deburred of 0.25 mm over a process duration of 20-30 seconds and under the impact angle of 30° into the surface of the guide slot of the lock cylinder to be deburred.

The device and the method for deburring objects described above enable (through the at least one flat work surface inclined with respect to the main axis of the sonotrode) the impact of the sound waves required for the formation of Rayleigh waves at the material-specific impact angle on the surface of the object to be deburred, even if if this surface is in an area of the object that is difficult to access, e.g. inside the guide slot of a lock cylinder.

As a result, the device according to the invention and the method according to the invention for ultrasonic deburring of an object prove to be particularly suitable for deburring areas of objects that are difficult to access, for example the guide slot of a lock cylinder.

Claims (10)

Method for ultrasonic deburring of an object in which ultrasound is generated via an ultrasonic generator and introduced into an object to be deburred via a sonotrode located in an ultrasound transmission medium, the sonotrode being at a defined distance between a working surface at the tip of the sonotrode and the distance in front of it The work surface of the object to be deburred is arranged, and this work surface of the sonotrode is aligned in a defined manner relative to the surface of the object to be deburred, such that the surface normal of this work surface of the sonotrode is aligned at a predeterminable angle to the surface of the object to be deburred , in which Rayleigh waves are generated in the surface of the object,
characterized ,
that a sonotrode is used which has at least one flat working surface, the surface normal of which is inclined relative to the main axis of the sonotrode. Method for ultrasonic deburring of an object according to claim 1,
characterized,
that a sonotrode is used which has at least one flat working surface, the surface normal of which is inclined to the main axis of the sonotrode by an angle between 20° and 45°. Method for ultrasonic deburring of an object according to claim 1 or 2,
characterized ,
a sonotrode is used which has at least two flat working surfaces, the respective surface normal of which is inclined relative to the main axis of the sonotrode, preferably each inclined by an angle between 20° and 45°. Method for ultrasonic deburring of an object according to claim 3,
characterized,
that a sonotrode is used whose at least two flat working surfaces are located on two opposite sides of the sonotrode tip. Method for ultrasonic deburring of an object according to one of the preceding claims,
characterized,
that a sonotrode is used whose cross section at its tip perpendicular to its main axis is adapted to the cross section of an interior region of the object to be deburred. Device for ultrasonic deburring of an object comprising an ultrasonic generator, a sonotrode, a device for receiving the object to be deburred and a device for the defined adjustment of the distance between a work surface at the tip of the sonotrode and the surface of the object to be deburred located at this distance in front of this work surface and a device for the defined alignment of this working surface of the sonotrode relative to the surface of the object to be deburred, such that the surface normal of this working surface of the sonotrode can be aligned at a predetermined angle to the surface of the object,
characterized,
that the sonotrode has at least one flat working surface, the surface normal of which is inclined relative to the main axis of the sonotrode. Device for ultrasonic deburring of an object according to claim 6,
characterized,
that the sonotrode has at least one flat working surface, the surface normal of which is inclined at an angle between 20° and 45° relative to the main axis of the sonotrode. Device for ultrasonic deburring of an object according to claim 6 or 7,
characterized,
that the sonotrode has at least two flat working surfaces, the respective surface normals of which are inclined relative to the main axis of the sonotrode, preferably each inclined by an angle between 20° and 45°. Device for ultrasonic deburring of an object according to claim 8,
characterized,
that the sonotrode has at least two flat working surfaces, which are located on two opposite sides of the sonotrode tip. Device for ultrasonic deburring of an object according to one of claims 6 to 9,
characterized,
that the sonotrode is designed in such a way that its cross section at its tip perpendicular to its main axis is adapted to the cross section of an interior region of the object to be deburred.