Method and device for applying a surface structuring to a workpiece on a machine tool

Abstract

Method for applying a surface structuring to a surface of a workpiece (WS) on a machine tool (1000), comprising: - carrying out a feed movement of a milling tool (90) with at least one projecting cutting edge along the surface of the workpiece (WS), which milling tool (90) is driven in rotation by a work spindle (1040) of the machine tool (1000) and is accommodated in a tool head (10) of the machine tool (1000), - applying the surface structuring according to a predetermined pattern to the surface of the workpiece (WS) during the feed movement of the milling tool (90) on the basis of a control signal to an actuator (20) integrated in the tool head (10), which actuator is designed to drive an oscillation of the milling tool (90) on the basis of the control signal, wherein the control signal comprises a high-frequency carrier signal and a useful signal modulating the carrier signal, which is generated on the basis of data indicating the predetermined pattern, characterized in that the control signal is transmitted contactlessly via a transmitter unit arranged on the work spindle (1040) to a receiver unit arranged on the tool head (10), and the actuator (20) is driven on the basis of the useful signal after demodulation of the control signal.

Description

[0001] The present invention relates to a method for applying a surface structuring to a surface of a workpiece on a machine tool. Furthermore, the present invention relates to a device and a machine tool on which the aforementioned method can be carried out. Furthermore, the present invention relates to a computer program product with which the aforementioned method can be carried out. BACKGROUND OF THE INVENTION

[0002] DE 10 2012 002 140 B4 discloses a generic method, in particular a face milling method, for applying a surface structuring to the surface of a workpiece. Such surface structuring or marking can serve, for example, decorative purposes or for coding the component or workpiece, for example, by applying image and / or text patterns to the surface of the workpiece.

[0003] In this case, a milling tool or face milling tool can be used on a machine tool. This tool has, for example, an axially protruding cutting edge that is not located in the tool axis and rotates around the tool axis when the tool is driven. Unlike simple face milling, the milling tool has, for example, a tip, which can be formed by a protruding cutting edge of the milling tool and can be created by grinding back or dismantling the remaining cutting edges.

[0004] The structuring of the workpiece surface takes place during the face milling process, i.e. the tool (e.g. an end mill or a cutter head, or another milling tool) moves in a rotating cutting motion across the face of a workpiece and is moved by one or more machine axes (linear and / or rotary axes) of the machine tool. The tip or protruding cutting edge of the milling tool rotating around the tool axis is not located in the tool's center of rotation but further out. The exact position of the tip above the workpiece surface can be determined from the position of the tool center (e.g. the so-called tool center point) and the current angle of rotation of the tool.

[0005] If a short, pulsed deflection of the tip axially forward in the direction of the tool axis occurs at predetermined positions based on the desired pattern, this tool tip presses a pixel into the workpiece surface. Through multiple, precisely positioned deflections, any desired pixel pattern (e.g., an image and / or text pattern) can be created.

[0006] However, in the prior art method according to DE 10 2012 002 140 B4, the dimensions of the tool head holding the tool must be relatively large. The described method is based on a piezo stack actuator being deflected by a rectangular pulse voltage. Since the deflection is directly proportional to the voltage and the length of the piezo stack, the tool must automatically be very large and provide high power and energy.

[0007] Furthermore, the required pulsed voltage signals cannot be transmitted using inductive or contactless power or signal transmission, as the inductances always influence the signal. If short pulse sequences are transmitted inductively at low frequencies (approximately 1 to 5 kHz), the signal is severely distorted due to the high inductances, so that the pattern or surface structuring is not applied with the desired image quality. However, if slip rings are used for signal transmission using contact, this is disadvantageous in industrial practice, particularly due to the susceptibility to maintenance caused by wear and contamination.

[0008] The method known in the prior art therefore has the disadvantages of a large (and thus inappropriately dimensioned) tool head and a wire-based (or slip-ring) energy transmission.

[0009] DE 10 2011 077 568 A1 relates to a method for machining a workpiece with a tool, in which the tool engages the workpiece, and a cutting movement is induced between the two. Furthermore, a relative first vibration movement superimposed on the cutting movement is induced between the workpiece and the tool in such a way that one or more characteristic values ​​of the first vibration movement and one or more characteristic values ​​of the cutting movement are adjusted relative to one another. The superimposed vibration movement can also be induced in such a way that distinguishable surface areas of the workpiece are created.

[0010] EP 2 946 859 A1 relates to a processing device comprising a main body side equipped with a power supply unit that outputs alternating voltage; a tool side rotatable relative to the main body side, the tool side being equipped with an ultrasonic transducer to which a tool is connected; a pair of a primary current coil and a secondary current coil arranged between the main body side and the tool side on a concentric axis with a rotatable center axis of the tool side, wherein a drive power is supplied via the primary and secondary current coils from the power supply unit on the main body side to the ultrasonic transducer on the tool side; a pair of signal coils arranged between the main body side and the tool side such that the signal coils are positioned on a concentric axis with the current coils on the main body side and the tool side, respectively.a detection device provided on the tool side for detecting a vibration state of the ultrasonic transducer, and wherein a detection signal from the detection device is transmittable from the tool side to the main body side via the signal coils; and a power supply control device provided on the main body side for controlling a power supply frequency to the primary power coil based on the detection signal from the detection device. SUMMARY OF THE INVENTION

[0011] With a view to avoiding the above-described disadvantages of the previously known method for applying a surface structuring to a surface of a workpiece, it is an object of the present invention to provide an improved method for applying a surface structuring to a surface of a workpiece, which can be implemented with smaller and more compact dimensions of the tool, tool holder or tool head as well as with improved energy transmission or signal transmission and higher image quality of the applied pattern.

[0012] To achieve the above-described object, the invention proposes a method for applying a surface structuring to a surface of a workpiece according to claim 1. Furthermore, a control device of a machine tool according to claim 11, a machine tool according to claim 12, and a computer program product according to claim 13 are proposed. Furthermore, a tool head with a demodulator can be provided. Dependent claims relate to preferred exemplary embodiments of the invention.

[0013] According to one aspect of the invention, in particular, a method for applying a surface structuring to a surface of a workpiece on a machine tool is proposed, which comprises: carrying out a feed movement of a milling tool, which is driven in rotation by a work spindle of the machine tool and accommodated in a tool head of the machine tool, with at least one protruding cutting edge along the surface of the workpiece, applying the surface structuring according to a predetermined pattern to the surface of the workpiece during the feed movement of the milling tool on the basis of a control signal to an actuator integrated in the tool head, which actuator is configured to drive an oscillation of the milling tool on the basis of the control signal, wherein the control signal comprises a high-frequency carrier signal and a useful signal modulating the carrier signal,which is generated on the basis of data specifying the given pattern.,

[0014] The invention is based on the idea that a control signal of a method for applying a surface structuring to a workpiece surface for driving a vibration-inducing actuator on a tool head of a machine tool is transmitted to the tool head not as a direct wanted signal but as a control signal modulated with the wanted signal and containing a high-frequency carrier signal. This enables the use of inductive energy transmission to the tool head, allowing the tool head to be designed to be less prone to maintenance and more compact.

[0015] In particular, an improved method for applying a surface structuring to a surface of a workpiece can be provided, which can be realized with smaller and more compact dimensions of the tool, tool holder or tool head as well as with improved energy transmission or signal transmission and higher image quality of the applied pattern.

[0016] According to a practical preferred embodiment of the invention, the data specifying the predefined pattern can comprise image data, in particular bitmap image data. This has the advantage that the pattern can be specified simply and efficiently.

[0017] According to an expedient preferred embodiment of the invention, the control signal can be transmitted contactlessly via a transmitter unit arranged on the work spindle to a receiver unit arranged on the tool head, particularly preferably by means of an inductive energy transmission.

[0018] According to a preferred embodiment of the invention, the actuator is driven based on the modulated control signal. This has the advantage that small, compact, and reliable ultrasonic tool heads can be used for the process, even if they lack a demodulation circuit.

[0019] According to a practical preferred embodiment of the invention, the actuator is alternatively driven based on the wanted signal after demodulation of the control signal. This has the advantage that the image quality of the applied pattern can be further improved.

[0020] According to an expedient preferred embodiment of the invention, the high-frequency carrier signal is amplitude-modulated and / or frequency-modulated on the basis of the useful signal.

[0021] According to a preferred embodiment of the invention, the carrier signal has a frequency in the ultrasonic range. The frequency of the carrier signal can preferably be greater than 10 kHz, in particular greater than 15 kHz, and preferably less than 60 kHz. The carrier signal can preferably have a substantially sinusoidal waveform.

[0022] According to an expedient preferred embodiment of the invention, the actuator is designed to drive an oscillation in the axial direction of the milling tool, ie in particular in the direction of the tool axis of the milling tool or in the direction of the rotation axis of the milling tool.

[0023] According to an expedient preferred embodiment of the invention, the surface structuring has a pattern corresponding to the predetermined pattern.

[0024] According to an expedient preferred embodiment of the invention, the actuator is configured to drive (possibly in addition or alternatively to an axial oscillation) a rotational oscillation about the axial direction of the milling tool.

[0025] According to a practical preferred embodiment of the invention, the actuator comprises one or more piezo elements, in particular a stack of several plate-shaped piezo elements. This allows the actuator to be designed in a particularly simple and reliable manner.

[0026] According to a preferred embodiment of the invention, an axial direction of the tool is oriented parallel to a normal vector of the workpiece surface during the feed movement along the surface of the workpiece. The axial direction of the tool is, in particular, the direction of the tool axis of the milling tool or the direction of the rotation axis of the milling tool.

[0027] According to an expedient preferred embodiment of the invention, the tool is moved perpendicular to a normal vector of the surface of the workpiece during the feed movement along the surface of the workpiece.

[0028] According to one aspect of the invention, a control device of a machine tool for controlling a method according to one of the preceding aspects is further proposed. Such a control device comprises, in particular, a memory device for storing data indicating the predetermined pattern and / or a receiving device for receiving data indicating the predetermined pattern, and / or a control signal generating device for generating the control signal with the high-frequency carrier signal and the useful signal modulating the carrier signal, which is generated based on the data indicating the predetermined pattern.

[0029] According to one aspect of the invention, a machine tool with such a control device is further proposed, which in particular further comprises a tool head which is configured to receive a milling tool with at least one protruding cutting edge, and / or an actuator integrated in the tool head which is configured to drive an oscillation of the received milling tool on the basis of a control signal of the control device.

[0030] According to one aspect of the invention, a computer program product is further proposed comprising a computer program stored on a computer-readable data storage medium, which computer program is executable on a numerical control device of a numerically controlled machine tool or in a computer connected to a control device of a numerically controlled machine tool, and which is configured to control a method according to one of the preceding aspects on the machine tool.

[0031] Although the invention is not limited to the fact that the actuator of the tool head is supplied with the demodulated control signal without the components of the carrier signal, but the method can be carried out in a particularly simple manner by supplying the modulated control signal directly to the actuator, it is also possible, e.g. for reasons of a desired surface quality, to supply the useful signal or the demodulated control signal to the actuator.

[0032] In this context, according to embodiments, a tool head for a machine tool is proposed, which is configured to receive a milling tool with at least one protruding cutting edge on a tool holder, and which comprises an actuator configured to drive an oscillation of the milling tool on the basis of the control signal, wherein the control signal comprises a high-frequency carrier signal and a useful signal modulating the carrier signal, which is generated on the basis of data indicating the predetermined pattern.

[0033] Furthermore, the tool head can have a demodulation device (e.g. a demodulation circuit) which is designed to demodulate the modulated control signal received from the control device of the machine tool at the tool head or to reconstruct the useful signal (without or substantially without components of the carrier signal) by demodulating the modulated control signal, and to input the demodulated control signal or reconstructed useful signal to the actuator for controlling the oscillation of the tool on the basis of the demodulated control signal or reconstructed useful signal.

[0034] Further aspects and their advantages as well as advantages and more specific embodiments of the aspects and features described above are described in the following, but in no way limiting, descriptions and explanations of the attached figures. BRIEF DESCRIPTION OF THE CHARACTERS Fig. 1 shows an example of a tool holder (tool head) in sectional view, which can be used in the method according to the invention according to embodiments; Fig. 2 shows, by way of example, a schematic representation of a machine tool with a tool holder (tool head), which can be used in the method according to the invention according to embodiments; Fig. 3A shows, by way of example, a flow diagram of a method of transmitting a control signal in a method for applying a surface structuring to a surface of a workpiece on a machine tool according to an embodiment; Fig. 3B shows, by way of example, a flow diagram of a method of transmitting a control signal in a method for applying a surface structuring to a surface of a workpiece on a machine tool according to a further exemplary embodiment; Fig. 4A shows, by way of example, a flow diagram of a method of receiving a control signal and applying a surface structuring to a surface of a workpiece on a machine tool according to an embodiment; Fig. 4B shows, by way of example, a flow diagram of a method of receiving a control signal and applying a surface structuring to a surface of a workpiece on a machine tool according to a further embodiment; and Fig. 5 shows examples of a carrier signal, a useful signal, an amplitude-modulated control signal and a frequency-modulated control signal according to embodiments. DETAILED DESCRIPTION OF THE FIGURES AND PREFERRED EMBODIMENTS OF THE PRESENT INVENTION

[0035] Examples and embodiments of the present invention are described in detail below with reference to the accompanying figures. Identical or similar elements in the figures may be designated by the same reference numerals, although sometimes different reference numerals may be used.

[0036] It should be emphasized, however, that the present invention is in no way limited or restricted to the exemplary embodiments and their embodiment features described below, but further comprises modifications of the exemplary embodiments, in particular those which are encompassed by modifications of the features of the described examples or by combination of one or more of the features of the described examples within the scope of protection of the independent claims.

[0037] Fig. 1 shows an exemplary structure of a tool holder 10 (tool head) that can be used in the method according to the invention.

[0038] At one end of the tool holder 10 there is a tool receiving section 11 for receiving a tool 90 (in Fig. 1 not shown). In the tool holder 10, several, e.g., six, perforated disk-shaped first piezo elements 21 are arranged, for example, stacked, which are connected, for example, via a transmission section 12, to the tool receiving section 11 and, for example, form an ultrasonic transducer 20 (ultrasonic generator / actuator) for converting an electrical voltage into a mechanical oscillation (e.g., with a frequency in the ultrasonic range).

[0039] For example, the mechanical vibration of the first piezo elements 21 is transmitted to the tool 90 via the transmission section 12. The first piezo elements 21 can be designed, for example, as piezoceramic discs with electrodes arranged between them.

[0040] The energy supply or control of the ultrasonic transducer 20 is carried out, for example, via a transformer (first transformer), which, for example, comprises a first pot core and a primary winding 32 (transmitter unit / transmitter coil) on the machine side (in Fig. 1 not shown) and, for example, comprises on the tool side a second shell core 33 and a secondary coil 34 (receiver unit / receiver coil), which are arranged, for example, as ring elements on the outside of the tool holder 10.

[0041] On a side of the stack of first piezo elements 21 facing away from the tool receiving section 11, a perforated disk-shaped piezoelectric sensor element 40 is arranged, for example, which comprises, for example, a piezo element 41 and two contacts 42 and which is, for example, mechanically coupled to the first piezo elements 21, but is electrically insulated from the first piezo elements 21 by an insulating element 43, which can consist of a ceramic perforated disk. By means of a further insulating element 43, the piezoelectric sensor element 40 is, for example, electrically insulated from a fastening element 13, e.g., a fastening nut.

[0042] The fastening element 13 serves to fasten the piezoelectric sensor element 40 to the ultrasonic transducer 20 (ultrasonic generator / actuator) and to preload the first piezo elements 21 due to the dynamic load.

[0043] The first piezo elements 21 and the piezoelectric sensor element 40 are oriented in the same way, which on the one hand enables the generation and detection of the vibration in the same direction and on the other hand achieves a space-saving arrangement of the elements in the tool holder 10 (tool head).

[0044] The piezoelectric sensor element 40 converts the mechanical vibrations of the vibratory system, which comprises the tool 90, the transmission section 12, the ultrasonic transducer 20 and the piezoelectric sensor element 40, into a sensor signal which is transmitted, for example, as an electrical voltage via a wire connection 50 from the piezoelectric sensor element 40 through the tool holder 10 to a transmitter element on the outside of the tool holder 10.

[0045] From the transmitter element 61 and 62 at a bore 70, the sensor signal is transmitted, for example, contactlessly to a machine-side receiver element (in Fig. 1 not shown).

[0046] The transmitter element 61 and 62 is, for example, part of another transformer (second transformer) and includes, for example, a first ferrite core and a primary winding; the receiver element is also part of the second transformer and includes a second ferrite core and a secondary winding. However, it is also possible to provide an optical transmitter element.

[0047] Thus, the sensor signal can be transmitted inductively from the tool holder 10 to a machine-side sensor signal evaluation device.

[0048] Fig. 2 shows, by way of example, a schematic representation of a machine tool 1000 according to an embodiment of the invention, with a tool holder 10 (tool head), which can be used in the method according to the invention according to embodiments.

[0049] The machine tool 1000 can be configured, for example, as a numerically controlled milling machine, a numerically controlled universal milling machine, or a numerically controlled machining center. To control a relative movement between the tool and the workpiece, the machine tool can have a plurality of controllable linear axes (usually referred to as the X-axis, Y-axis, and / or Z-axis, for example) and / or one or more circular or rotary axes (usually referred to as the A-axis, B-axis, and / or C-axis, for example).

[0050] For example, the machine tool 1000 in Fig. 2 comprises a machine bed 1010, a machine stand 1020 and a spindle head 1030, wherein the machine bed 1010 carries, for example, a workpiece table 1050 and the spindle head 1030 carries, for example, a work spindle 1040.

[0051] The tool table 1050 is mounted, for example, on horizontal linear guides 1051 arranged in a horizontal direction on the machine bed 1010, and is movable in a horizontal direction, and is movably controllable via a linear drive 1052 of a first linear axis of the machine tool 1000. A workpiece WS is clamped, for example, on the tool table in a workpiece clamping device 1053.

[0052] The spindle head 1030 is mounted, for example, on vertical linear guides 1031, which are arranged on the machine stand 1020 in a vertical direction, so as to be linearly movable in the vertical direction, and is movable and controllable via a linear drive 1032 of a second linear axis of the machine tool 1000, so that the work spindle 1040, on which a tool head 10 (tool holder) holding a tool 90 is received, is also vertically movable.

[0053] In further embodiments, one or more further linear axes may be provided, e.g. to additionally enable a linear movement of the workpiece relative to the tool in a direction perpendicular to the drawing plane of the Fig. 2 to enable.

[0054] Furthermore, one or more rotary or rotary axes can be provided, for example a rotary axis with a rotary axis drive for rotating the tool table 1050 (so-called rotary table).

[0055] By means of the above-described linear and, if applicable, circular or rotary axes or their drives, a relative movement of the tool 90 relative to the workpiece WS can be controlled.

[0056] For this purpose, a control device 1100 of the machine tool 1000 has a machine control device 1110, which, for example, comprises a CNC or NC control device 1112, which is configured to control the functions or machining processes on the machine tool 1000, for example based on NC data stored in a storage device 1111. In addition, the machine control device 1110 has, for example, a PLC or SPS device 1113 ("PLC" for Programmable Logic Controller or "SPS" for Programmable Logic Controller).

[0057] The PLC or SPS device 1113 is particularly preferably configured to transmit control signals to actuators of the machine tool based on control commands of the NC control device 1112 or, if appropriate, independently of the NC control device 1112, for example to the linear drives 1052 or 1032 of the linear axes or generally to drives of the machine axes or also to the spindle drive 1042 of the work spindle 1040.

[0058] In addition, the PLC or SPS device 1113 is configured to receive or read out sensor signals from position measuring sensors (not shown) of the machine tool 1000, which indicate actual positions of the drives and / or machine axes measured in real time during machining, and optionally forward them to the NC control device 1112. The PLC or SPS device 1113 can also be configured to enable other machine-internal or external devices or apparatuses to read out position data from the PLC or SPS device 1113 that indicate the actual positions of the drives and / or machine axes.

[0059] In addition to the spindle drive 1042 already mentioned above, the work spindle 1040 further comprises a tool holder 1041 (tool holder section) on which the tool head 10 is received and can be driven in rotation by means of the spindle drive 1042 (in particular for generating the cutting movement).

[0060] The tool head 10 is shown only schematically and has, for example, a tool interface body 14 (e.g. a tool taper, or steep or hollow shank taper, or also a Morse taper or other tool interfaces), with which the tool head 10 is received on the tool holder 1041 of the work spindle 1040. For example, the tool head 10 can be analogous to Fig. 1. In contrast to the tool holder 10 of the embodiment according to Fig. 1, the tool head 10 has Fig. 2 additionally has a demodulator 15 which will be described in more detail later.

[0061] The tool head 10 has, for example, an inductive receiver unit 34 (e.g. analogous to the secondary coil or winding 34 of the Fig. 1) for contactless or inductive reception of a control signal from the transmitter unit 32 (primary coil or winding) which is attached to the spindle head (or to the spindle).

[0062] For example, the tool head 10 in Fig. 2 further comprises an actuator 20 (e.g. ultrasonic transducer or ultrasonic generator, possibly comprising one or more piezo elements by way of example) which is designed to cause the tool head 10 or the tool 90 accommodated in the tool head 10 to oscillate (in particular in the direction of the tool axis 92) on the basis of the control signal, preferably in particular in the ultrasonic range, ie in particular at ultrasonic frequencies or at frequencies above 10 kHz or in particular e.g. above 15 kHz, e.g. up to 60 kHz.

[0063] For example, the tool head 10 in Fig. 2 further comprises a demodulator 15 (e.g. a demodulating circuit, possibly with a microcontroller) connected upstream of the actuator 20, which demodulator demodulates the control signal received via the receiver unit 34 or reconstructs a low-frequency carrier signal with which a high-frequency carrier signal is modulated on the control device side.

[0064] However, the invention is not limited to tool heads with demodulator 15, but the modulated control signal can also be input directly to the actuator in other embodiments.

[0065] The tool head 10 also has the tool receiving section 11, on which the milling tool 90 is received or held. The tool 90 has a tool axis 92, about which the tool is driven in rotation via the spindle drive 1042. The tool tip 91 is formed, for example, by a milling cutter edge that is arranged protruding in the axial direction of the tool axis 92 on an outer side of the milling tool 90, i.e., in particular, spaced from the tool axis 92. When the tool 90 is driven in rotation, the milling cutter edge or tool tip 91 rotates around the tool axis 92.

[0066] To drive the actuator 20 or to control the vibration of the tool 90, the control device 1100 of the machine tool 1000 has a further control device 1120, which generates the control signal and outputs it via the transmitter unit 32 to the tool head 10 for transmission to the receiver device 34 for the actuator 20. In further embodiments, the control device 1120 can also be integrated into the machine control device 1110 and / or comprise an external data processing device, e.g., a computer, or be formed by an externally connected data processing device, e.g., a computer.

[0067] The control device 1120 comprises, for example, a generator 1124 for generating the high-frequency carrier signal. The high-frequency carrier signal can, for example, be a substantially periodic or preferably substantially sinusoidal carrier signal, which preferably has a fixed frequency and / or a fixed amplitude. The frequency of the carrier signal is high-frequency (ie, in particular, with a frequency greater than 10 kHz, preferably greater than 15 kHz) and is preferably in the ultrasonic range.

[0068] The control device 1120 further comprises, for example, a storage device 1121 for storing pattern data that specify the pattern or image and / or text pattern to be applied to the surface of the workpiece WS. The pattern data can represent image data (e.g., data storing a bitmap graphic or other image data formats) that specify the pattern in an image data format.

[0069] Alternatively, the control device 1120 can store in the storage device 1121 pattern position data that is generated based on pattern data or image data specifying the pattern (e.g., data storing a bitmap graphic or other image data formats) and already specifies a position-image / pattern relationship, ie, data that specifies positions on the surface of the workpiece at which the image and / or text pattern is to be applied, pattern position data that specifies deflection positions for a plurality of cutting edge positions of the tool tip 91 on the surface of the workpiece WS based on the specified pattern (e.g., with high deflection at positions of the pattern and with low or no deflection at positions where no pattern is to be applied). This can, for example, be prepared and pre-stored in the form of a table.

[0070] The control device 1120 further comprises, for example, a data processing device 1122, which is configured to read the data from the storage device 1121 and can also read positions, in particular axis positions, from the machine control device 1110. This can preferably take place in real time during the machining of the workpiece WS, wherein, on the one hand, current actual positions of the axes and drives of the machine tool 1000, e.g., from the PLC or SPS control device 1113 (and / or from the NC control 1112), can preferably be read out in real time, or, on the other hand, current target positions can be read out from the NC control 1112.

[0071] In particular, the data processing device 1122 is preferably configured, on the basis of the read-out position data of the machine control, to calculate the cutting position of the tool tip 91 of the tool 90 relative to the workpiece WS (e.g., on the basis of the calculated position of the tool axis 92, on the basis of the axis positions of the machine tool 1000 and on the basis of the angular position of the work spindle, in particular taking into account the distance of the tool tip to the tool axis 92).

[0072] Alternatively, it is also possible for the position of the tool axis 92 or the cutting position of the tool tip 91 to be calculated in the NC control 1112 and read out by the data processing device 1122.

[0073] On the basis of the calculated or read cutting position of the tool tip 91 of the tool 90 relative to the workpiece WS and in comparison with the data of the storage device 1121 indicating the pattern, the data processing device 1122 is configured to determine or calculate a currently desired deflection of the tool 90 on the basis of the desired pattern at the current cutting position and to output it to a useful signal generator 1123 as a desired value.

[0074] Based on the calculations or specifications of the data processing device 1122, the useful signal generator 1123 generates a possibly continuous useful signal with low-frequency pulses, in particular at (average) frequencies less than 10 kHz and particularly preferably less than 7 or in particular 5 kHz and preferably on average greater than approximately 1 kHz. The pulses of the useful signal can, for example, be rectangular (see, for example, Fig. 5), however, the pulses of the useful signal can also be Gaussian or correspond to a sine half-wave.

[0075] Furthermore, the control device 1120 also comprises a modulator 1125 (or modulating circuit, possibly with a microcontroller) which is configured to modulate the high-frequency carrier signal generated by the generator 1124 with the useful signal generated by the useful signal generator 1123 and thus to generate the modulated control signal on the basis of the carrier and useful signals, which is to be output to the tool head 10.

[0076] Here, it is possible to modulate the carrier signal with the wanted signal through amplitude modulation. However, it is also possible to modulate the carrier signal with the wanted signal through frequency modulation. Combinations of amplitude and frequency modulation are also possible. If a demodulator 15 is provided on the tool head 10, the wanted signal can be reconstructed there, and the type of modulation plays only a minor role.

[0077] However, if the tool head 10 does not include a demodulator and the modulated control signal is delivered directly to the actuator 20, the type of modulation changes the appearance of the applied pattern. In this case, it is possible in embodiments for the operator to independently adjust, depending on their preference and need, whether amplitude or frequency modulation, or a combination thereof, should be used.

[0078] On the one hand, in embodiments without a demodulator on the tool head, the carrier signal can be modulated with the wanted signal by amplitude modulation. This leads, for example, to a greater deflection of the actuator 20 being generated at the times of a pulse of the wanted signal due to the higher amplitude. Thus, the impacts of the tool cutting edge of the tool tip 91 are deeper into the surface of the workpiece 90 at the times of a pulse of the wanted signal, with the frequency of the carrier signal remaining constant (greater penetration depth with a pulse of the wanted signal), so that the pattern on the surface can be generated by depths and heights in the surface structuring.

[0079] However, in embodiments without a demodulator on the tool head, it is also possible to modulate the carrier signal with the wanted signal by frequency modulation. This results, for example, in a different (preferably higher) frequency of the actuator 20 being generated at the same amplitude at the same time during a pulse of the wanted signal due to the higher frequency of the control signal. Thus, the impacts of the tool cutting edge of the tool tip 91 are the same depth but at different frequencies (e.g., higher frequency at the pulse of the wanted signal), so that the pattern on the surface of the workpiece 90 can be generated by different shades in the surface structuring.

[0080] Likewise, in embodiments without a demodulator on the tool head, it is possible to modulate the carrier signal with the wanted signal by amplitude and frequency modulation. This leads, for example, to a higher frequency of the actuator 20 being generated at times of a pulse of the wanted signal due to the higher frequency of the control signal, and also to a greater deflection of the actuator 20 being generated at times of a pulse of the wanted signal due to the higher amplitude. Thus, the impacts of the tool cutting edge of the tool tip 91 are deeper into the surface of the workpiece 90 at times of a pulse of the wanted signal (greater penetration depth at pulse of the wanted signal) and the impacts of the tool cutting edge of the tool tip 91 are at different frequencies (e.g. higher frequency at pulse of the wanted signal), so that the pattern on the surface can be generated by depths and heights and by different shades in the surface structuring.

[0081] Fig. 5 shows examples of a carrier signal, a useful signal, an amplitude-modulated control signal and a frequency-modulated control signal according to embodiments.

[0082] Here, a high-frequency sinusoidal carrier signal V_TS and a (merely exemplary) periodic wanted signal V_NS with exemplary rectangular pulses are shown. It should be noted that the wanted signal V_NS generally does not have periodically occurring pulses of the same pulse width, since the pulse frequency and pulse width vary individually depending on the respective pattern.

[0083] An example is Fig. 5 further control signals which can be generated by modulating the carrier signal V_TS on the basis of the useful signal V_NS, namely, for example, the amplitude-modulated control signal V_SS_am and the frequency-modulated control signal V_SS_fm.

[0084] Fig. 3A shows, by way of example, a flow diagram of a method of transmitting a control signal in a method for applying a surface structuring to a surface of a workpiece WS on a machine tool 1000 according to an embodiment.

[0085] In step S301A, pattern data is provided that indicates the pattern of the predefined surface structuring to be applied. This can be, for example, image data that indicates the text and / or image pattern to be applied (e.g., bitmap graphic data or image data in another image data format, e.g., as a JPEG file).

[0086] In step S302, machine control data for controlling the feed movement of the tool 90 relative to the workpiece WS is provided. This can include, for example, NC data (e.g., one or more NC programs) that describe a feed movement of the tool along the surface of the workpiece WS, e.g., for performing a face milling process across the surface of the workpiece WS. If the workpiece has a free-form surface, the workpiece WS is preferably machined on the free-form surface such that the machine control data specify a feed movement in which the tool axis 92 is always aligned coaxially with the respective (orientation-changing) normal vector of the workpiece WS at all times. If the workpiece surface is flat at the location of the pattern to be applied, the feed movements are preferably carried out with a constant orientation of the tool axis 92 perpendicular to the workpiece surface.

[0087] In step S303, the machine controller 1110 performs the feed movement of the tool 90 relative to the workpiece WS based on the machine control data.

[0088] During machining and the executed feed movement, current position data are determined in real time in step S304 (see above), which directly or indirectly (i.e., for example, after calculation from the position data) indicate the position of the tool axis 92 of the tool 90 or the position of the tool 90.

[0089] In step S305, angle data are determined simultaneously with step S305, which directly or indirectly (e.g., after calculation from the angle data) indicate the angular position of the tool 90 or the tool tip 91.

[0090] In step S306, the current cutting edge position of the tool tip 91 of the tool 90 is determined or calculated based on the position and angle data. Thus, the position of the tool tip 91 of the tool 90 above the surface of the workpiece is known at this time.

[0091] On the basis of the determined current cutting edge position of the tool tip 91 of the tool 90, the corresponding useful signal is generated in step S307A on the basis of the predetermined pattern data, in particular, for example, in such a way that the useful signal has a deflection pulse or pulse (a higher or high amplitude) at positions of the pattern (or when the tool tip is located at a position of the pattern) and has no deflection pulse or pulse (i.e. a lower or low amplitude) at other positions (or when the tool tip is not located at a position of the pattern).

[0092] In step S308, the high-frequency carrier signal is modulated with the useful signal and the modulated control signal is generated, which is then transmitted to the receiver unit 34 of the tool head 10 in step S309.

[0093] In the above example, in step S307A the useful signal is generated in real time on the basis of the pattern data (e.g. image data or bitmap image data). In further embodiments, for example, another type of data can be generated before machining, which is generated on the basis of pattern data (e.g. image data or bitmap image data) and indicates positions on the tool surface (e.g. in the machine tool coordinate system) at which the pattern is to be applied. This can be a table, for example. In particular, this can be data (pattern position data) which is generated on the basis of image data and indicates positions of the pattern (e.g. pixel positions) on the surface of the workpiece WS in the workpiece and / or machine tool coordinate system.

[0094] Fig. 3B shows, by way of example, a flow diagram of a method of transmitting a control signal in a method for applying a surface structuring to a surface of a workpiece on a machine tool according to a further exemplary embodiment.

[0095] In step S301B, image data are provided which indicate the pattern in an image data format, and in step S301C these are no longer converted into pattern position data during, but rather, for example, before the actual machining process, or pattern position data are determined on the basis of the image data which, for example, indicate positions of the pattern on the surface of the workpiece WS (e.g. in the workpiece and / or machine tool coordinate system).

[0096] In step S307B, the useful signal is then generated or adjusted in real time during workpiece machining based on the determined pattern position data and the determined cutting edge position. This may enable faster and more efficient data processing in real time, since simplified, usable pattern position data is generated or determined before the machining process begins (e.g., starting in S303).

[0097] The other steps S302, S303, S304, S305, S306, S308 and S309 can be carried out analogously to Fig. 3A should be carried out.

[0098] Fig. 4A shows, by way of example, a flow diagram of a method of receiving a control signal and applying a surface structuring to a surface of a workpiece on a machine tool according to an embodiment.

[0099] In step S401, the data recorded in step S309 (according to Fig. 3A or Fig. 3B) is received at the receiver unit 34 of the tool head 10 (e.g. inductively) and, in step S403A, is transmitted directly to the actuator 20, so that the actuator is controlled on the basis of the received control signal.

[0100] Thus, for example, the pattern of the surface structuring is applied to the surface of the workpiece in step S404A by the controlled feed movement (step S303) and the driving of the actuator 20 (S403A) based on the received (modulated) control signal.

[0101] Fig. 4B shows, by way of example, a flow diagram of a method of receiving a control signal and applying a surface structuring to a surface of a workpiece on a machine tool according to a further embodiment.

[0102] In step S401, the data recorded in step S309 (according to Fig. 3A or Fig.3B) is received at the receiver unit 34 of the tool head 10 (e.g. inductively) and demodulated in step S402 at the demodulator 15 of the tool head 10, in particular for reconstructing the useful signal from the modulated control signal.

[0103] The demodulated control signal or the reconstructed useful signal is transmitted, for example, to the actuator 20 in S403B, so that the actuator is controlled on the basis of the demodulated control signal or the reconstructed useful signal.

[0104] Thus, for example, the pattern of the surface structuring is applied to the surface of the workpiece in step S404B by the controlled feed movement (step S303) and the driving of the actuator 20 (S403B) on the basis of the demodulated control signal or the reconstructed useful signal.

[0105] Examples or embodiments of the present invention and their advantages have been described in detail above with reference to the attached figures.

[0106] It should be emphasized again that the present invention is in no way limited or restricted to the exemplary embodiments and their embodiment features described above, but further comprises modifications of the exemplary embodiments, in particular those which are encompassed by modifications of the features of the described examples or by combination of one or more of the features of the described examples within the scope of protection of the independent claims.

Claims

[1] Method for applying a surface structuring to a surface of a workpiece (WS) on a machine tool (1000), comprising: - carrying out a feed movement of a milling tool (90) with at least one projecting cutting edge along the surface of the workpiece (WS), which milling tool (90) is driven in rotation by a work spindle (1040) of the machine tool (1000) and is accommodated in a tool head (10) of the machine tool (1000), - applying the surface structuring according to a predetermined pattern to the surface of the workpiece (WS) during the feed movement of the milling tool (90) on the basis of a control signal to an actuator (20) integrated in the tool head (10), which actuator is designed to drive an oscillation of the milling tool (90) on the basis of the control signal, wherein the control signal comprises a high-frequency carrier signal and a useful signal modulating the carrier signal, which is generated on the basis of data indicating the predetermined pattern, characterized by , that the control signal is transmitted contactlessly via a transmitter unit arranged on the work spindle (1040) to a receiver unit arranged on the tool head (10), and the actuator (20) is driven on the basis of the useful signal after demodulation of the control signal. [2] Method according to claim 1, characterized by that the data specifying the predetermined pattern comprises image data, in particular bitmap image data. [3] Method according to one of the preceding claims, characterized by that the high-frequency carrier signal is amplitude-modulated based on the useful signal. [4] Method according to one of the preceding claims, characterized by that the high-frequency carrier signal is frequency-modulated based on the useful signal. [5] Method according to one of the preceding claims, characterized by that the carrier signal has a frequency in the ultrasonic range. [6] Method according to one of the preceding claims, characterized by that the actuator (20) is designed to drive an oscillation in the axial direction of the milling tool (90). [7] Method according to claim 3 and 6, characterized by that the surface structuring has a pattern corresponding to the specified pattern. [8] Method according to one of the preceding claims, characterized by that the actuator (20) comprises one or more piezo elements. [9] Method according to one of the preceding claims, characterized by that an axial direction of the tool is oriented parallel to a normal vector of the surface of the workpiece (WS) during the feed movement along the surface of the workpiece (WS). [10] Method according to one of the preceding claims, characterized bythat the tool (90) is moved perpendicular to a normal vector of the surface of the workpiece (WS) during the feed movement along the surface of the workpiece (WS). [11] Control device of a machine tool (1000) for controlling a method according to one of the preceding claims, with - a storage device for storing data indicating the predetermined pattern and / or a receiving device for receiving data indicating the predetermined pattern, and - a control signal generating device for generating the control signal with the high-frequency carrier signal and the useful signal modulating the carrier signal, which is generated on the basis of the data indicating the predetermined pattern. [12] Machine tool (1000) with a control device according to claim 11, a tool head (10) which is adapted to receive a milling tool (90) with at least one projecting cutting edge, and an actuator (20) integrated in the tool head (10) which is configured to drive an oscillation of the received milling tool (90) on the basis of a control signal from the control device. [13] Computer program product comprising a computer program stored on a computer-readable data storage medium, which is executable on a numerical control device of a numerically controlled machine tool (1000) or in a computer connected to a control device of a numerically controlled machine tool (1000), and which is configured to control a method according to one of claims 1 to 10 on the machine tool (1000).

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