Device and method for contactless fracture and / or wear monitoring

Abstract

The invention relates to a device and a method for contactless fracture and / or wear monitoring. The invention relates to a device and a method for contactless fracture monitoring in a machine tool and for contactless wear monitoring in a compensated or alternative manner. The apparatus includes a sensor and at least one magnetic field generator. The device measures a local change in the magnetic flux density by means of a sensor at a defined measurement distance and electronically evaluates the measurement signal by means of an electronic evaluation unit. The sensor is designed such that the sensor extends at most 500 [mu] m in the spatial direction, wherein a magnetic field can be measured in at least one spatial direction by means of the sensor.

Description

Technical Field

[0001] The invention relates to a device and a method for contactless detection of fracture and wear phenomena on ferromagnetic tools according to independent claim 1 and independent claim 7. Background Art

[0002] If a machine tool is equipped with a tool for chip-cutting workpieces and processes the workpieces in view of their geometry, unexpected and unforeseeable damage in the form of complete fractures may occur at the tool or minor fractures at the cutting edge may occur. If, for example, a complete fracture of the tool occurs, this often leads to damage to the workpiece in addition to the sudden load on the machine tool. If such a complete fracture of the tool remains unnoticed, in addition, incomplete machining of the workpiece generally occurs in the subsequent steps of the corresponding machine tool, which in turn leads to an undesirably high scrap rate. Wear phenomena in the form of small defects or fractures may also have a negative impact on the workpiece machining.

[0003] Therefore, a device for early recognition of fracture and / or wear phenomena is one of the most important factors for avoiding damage at the machine tool and for improving reliability during machining. Background Art

[0005] A method for contactless fracture and wear monitoring of tools is known from patent application DE 36 08 572 A, in which the position change of two adjacent machine parts equipped with weak magnets, at least one of which is loaded with forces due to the cutting process, is continuously measured and monitored inductively. The deformation of the tool, the tool carrier or the tool base support is used as a measure of the wear of the tool, since the forces on the tool increase with increasing wear.

[0006] The disadvantage of this method is that the monitoring of fractures and wear phenomena at the tool by indirect measurement methods is relatively inaccurate, since only larger fractures at the tool can be detected. Monitoring of the local cutting geometry is not possible at all with this method. Summary of the invention

[0007] The object of the present invention is to provide a device and a method by which a ferromagnetic tool can be reliably and contactlessly tested for fracture and / or wear. The device is contamination-insensitive and cost-effective to manufacture and should simultaneously achieve a relatively high measurement accuracy.

[0008] This object is achieved according to the invention by the features of claims 1 and 7. Advantageous embodiments and developments are described in the respectively dependent claims.

[0009] The device according to the invention is suitable for contactless fracture monitoring of ferromagnetic tools in machine tools and additionally or alternatively for wear monitoring. The device comprises a sensor and at least one magnetic field generator, which can be designed as a permanent magnet, for example. In this case, the device measures a local change in the magnetic flux density at a defined measuring distance with the aid of the sensor and electronically evaluates the measurement signal with the aid of an evaluation unit. The sensor is designed so that the longest extension of the sensitive surface in a spatial direction is at most 500 μm, wherein the magnetic field can be measured by the sensor in at least one spatial direction.

[0010] According to an advantageous development of the invention, the at least one magnetic field generator and the sensor can be arranged along a straight line which runs parallel to or perpendicular to the longitudinal axis of the ferromagnetic tool.

[0011] In another embodiment, the sensor and the at least one magnetic field generator are arranged in a housing of the device, wherein the at least one magnetic field generator is positioned in the housing such that its magnetic bias field extends through the at least one sensor and is coupled into the ferromagnetic tool.

[0012] The sensor advantageously comprises at least one Hall element and, additionally or alternatively, at least one TMR element.

[0013] According to an advantageous development of the invention, the sensor is able to detect at least one other physical variable in addition to measuring the magnetic flux density.

[0014] The physical variable may be, for example, a state variable such as pressure, temperature, etc. For example, it may be a temperature value measured in the field-sensitive region of the sensor, in particular such a temperature value being associated with a ferromagnetic tool.

[0015] The device is advantageously designed to remove contaminants from the device and, additionally or alternatively, from the ferromagnetic tool by means of compressed air and, additionally or alternatively, by means of an alternating magnetic field.

[0016] According to another aspect, the invention comprises a method for contactless fracture monitoring and additionally or alternatively wear monitoring of ferromagnetic tools in a machine tool by means of a device. The device comprises a sensor for point-wise measurement and at least one magnetic field generator. The method comprises the following steps:

[0017] Keep ferromagnetic tools and equipment relatively close;

[0018] Coupling a magnetic bias field into a ferromagnetic tool;

[0019] measuring the magnetic flux density of the magnetic field modulated by the ferromagnetic tool in at least one spatial direction;

[0020] The signal is corrected and evaluated to determine the geometry of the ferromagnetic tool.

[0021] In particular, high resolution of the measuring results can be achieved due to the special point design of the sensor.

[0022] In a further embodiment, the signal correction and the signal evaluation are performed electronically within the device.

[0023] After completion, the result of the signal evaluation is advantageously transmitted to a storage unit and additionally or alternatively to an output unit.

[0024] According to an advantageous development, at least one of the following variables is additionally determined:

[0025] The spatial position of the ferromagnetic tool;

[0026] The measurement distance of the ferromagnetic tool from the sensor;

[0027] ·Angular position of ferromagnetic tool;

[0028] The rotation speed of the ferromagnetic tool;

[0029] The diameter and, additionally or alternatively, the length of the ferromagnetic tool;

[0030] · Temperature of ferromagnetic tools.

[0031] When the device is arranged in a fixed manner, the ferromagnetic tool is advantageously moved relatively in at least one spatial direction during the approach process and the supplementary or alternative measuring process. The ferromagnetic tool can rotate around its longitudinal axis. When the ferromagnetic tool is arranged in a fixed manner, the device can be moved relatively in at least one spatial direction around the ferromagnetic tool during the approach process and the supplementary or alternative measuring process, wherein the ferromagnetic tool rotates around its longitudinal axis. Additionally or alternatively, the movement of the device can also take place on a trajectory around the ferromagnetic tool, wherein the ferromagnetic tool rotates around its longitudinal axis.

[0032] In another design, the evaluating includes the following steps:

[0033] · calling up or calculating a setpoint profile of at least one setpoint variable of a ferromagnetic tool;

[0034] comparing the called or calculated setpoint profile with the measured actual profile of at least one actual variable of the ferromagnetic tool;

[0035] When determining deviations:

[0036] – determine the extent of the deviation; and

[0037] If a defined threshold value is exceeded: performing an in-depth analysis of the measurement and additionally or alternatively aborting the measurement and additionally or alternatively aborting the workpiece processing.

[0038] The threshold value advantageously also takes into account at least one of the following variables:

[0039] The spatial position of the ferromagnetic tool;

[0040] The measurement distance of the ferromagnetic tool from the sensor;

[0041] ·Angular position of ferromagnetic tool;

[0042] The rotation speed of the ferromagnetic tool;

[0043] The diameter and additionally or alternatively the length of the ferromagnetic tool;

[0044] · Temperature of ferromagnetic tools.

[0045] According to an advantageous development, the measured data are evaluated in an in-depth analysis with regard to the wear form, wear parameters, position and condition of the cutting edge, position and condition of the chip groove, material composition, chip adhesion and additionally or alternatively the strength distribution of the ferromagnetic tool.

[0046] The invention is explained in more detail below also with regard to further features and advantages based on the description of exemplary embodiments and with reference to the attached schematic drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 A greatly schematic illustration showing an embodiment of the device according to the invention;

[0048] Figure 2 A greatly schematic illustration of the measuring principle of the device according to the invention is shown in a sectional view;

[0049] Figure 3 Two measurements of a ferromagnetic tool are shown with exemplary first and second actual course of events;

[0050] Figure 4 shows the measurement of a ferromagnetic tool with an exemplary third actual course of events;

[0051] Figure 5 A schematic diagram of the method according to the invention is shown as a flow chart;

[0052] Figure 6 Shown in Figure 5 Schematic diagram of the sub-steps included in the step "Evaluation". DETAILED DESCRIPTION

[0053] Some specific embodiments of the present invention are described in more detail below with reference to the accompanying drawings.

[0054] The device 1 according to the invention is suitable for use in the working space of a machine tool, in which a ferromagnetic tool 4 is to be checked for signs of fracture and additionally or alternatively signs of wear. For this purpose, the ferromagnetic tool 4 is moved relative to the device 1 and a measurement of the magnetic flux density is carried out.

[0055] exist Figure 1 1 shows a ferromagnetic tool 4 and a device 1 according to the invention, which comprises a housing 5, a carrier element 2.1 with a sensor 2 and a magnetic field generator 3. In the exemplary embodiment presented, the sensor 2 and the magnetic field generator 3 are located in the housing 5 of the device 1 according to the invention. The sensor 2 is arranged at that end of the device 1 which is located in the vicinity of the ferromagnetic tool 4, wherein a defined minimum measuring distance d is present between the ferromagnetic tool 4 and the device 1 in the form of an air gap.

[0056] In particular, it is advantageous if the sensor 2 is arranged between the magnetic field generator 3 and the ferromagnetic tool 4 on a straight line orthogonal to the longitudinal axis of the ferromagnetic tool 4. Alternatively, the ferromagnetic tool 4 can also be arranged between the at least one magnetic field generator 3 and the sensor 2, wherein the ferromagnetic tool 4, the sensor 2 and the at least one magnetic field generator 3 are also located on a straight line.

[0057] Thus, the straight line along which the at least one magnetic field generator 3 and the sensor 2 are located can also be parallel to the longitudinal extension of the ferromagnetic tool 4, wherein in this case, only the sensor 2 and the at least one magnetic field generator 3 are located on the straight line extending parallel to the longitudinal axis of the ferromagnetic tool 4. In this case, the sensor 2 should ideally be arranged closer to the tool carrier of the ferromagnetic tool 4 than the at least one magnetic field generator 3.

[0058] The measuring distance d defines the distance between the surface of the device 1 and the circular trajectory of the largest peripheral part of the cross section of the ferromagnetic tool 4. The measuring distance d is usually selected in this case so that a small air gap of between 200 μm and 300 μm remains between the device 1 and the ferromagnetic tool 4. The measuring distance d can therefore be constant during each inspection process or alternatively can be varied, for example depending on the diameter of the ferromagnetic tool 4 or the current temperature of the ferromagnetic tool 4 or the temperature of its environment.

[0059] In this case, a ferromagnetic tool 4 can be understood as a tool for producing a workpiece, wherein the machine tool predetermines or influences a relative movement (or movements) between the device 1 and the ferromagnetic tool 4 in the working space of the machine tool. In particular, this can be understood as single-edged and multi-edged tools for chip production methods, which have a cutting material with ferromagnetic properties. For example, drills, milling tools, reamers, broaching tools, turning tools or indexable inserts made of tool steel or carbide belong to this category.

[0060] For example, the ferromagnetic tool 4 can be moved by a machine tool in all three spatial directions x, y, z and rotated in a defined manner about its longitudinal axis (φ direction).

[0061] The magnetic bias field of at least one magnetic field generator 3 is coupled into the ferromagnetic tool 4, so that a magnetic field modulated by the ferromagnetic tool 4 is generated. The magnetic field modulated by the ferromagnetic tool 4 is characteristic in terms of the local magnetic flux density depending on the local cross-sectional geometry of the ferromagnetic tool 4. As a result, a concentration of magnetic field lines and therefore an increased magnetic flux density occurs at the cutting edge. In the chip groove of the ferromagnetic tool 4, there is a relatively low magnetic flux density, which makes it possible to distinguish between the cutting edge and the chip groove.

[0062] The sensor 2 is capable of measuring the magnetic flux density in at least one spatial direction x, y, z with a defined measuring distance d. The measurement is performed in a point-like manner, wherein the resolution of the measurement is predetermined by the sensitive surface of the sensor 2. In the spatial direction x, y, z with the longest extension, the sensitive surface advantageously has a size of less than 500 μm, in particular less than 200 μm and advantageously less than 100 μm. The size of the sensitive surface of the sensor 2 is decisive for the spatial resolution of the sensor 2. The bandwidth of the sensor 2 describes the (analog) measuring frequency and advantageously lies at least 10 kHz.

[0063] The device 1 measures the magnetic flux density in three spatial directions x, y, z using exactly one sensor. For this purpose, the sensor 2 can, for example, comprise three sensitive surfaces, wherein the sensitive surfaces can consist of three Hall elements or, supplementarily or alternatively, TMR elements arranged orthogonally to one another, which enable the magnetic flux density to be measured in three spatial directions x, y, z. However, the magnetic flux density can also be measured in only one or two spatial directions x, y, z. The choice of (one or more) spatial directions x, y, z is here situation-dependent, i.e., for example, dependent on the relative position of the device 1 and the ferromagnetic tool 4, wherein the (one or those) spatial directions x, y, z which provide the most reliable (one or more) measurement signals are always included in the measurement or evaluation.

[0064] A Hall element may be understood as a Hall effect element which may be implemented, for example, as a semiconductor component. A Hall element may in particular measure at least one Hall voltage, by means of which at least one local directional component of a magnetic field may be inferred.

[0065] A TMR element may be understood as an element which uses the tunnel magnetoresistance effect to determine at least one local directional component of a magnetic field. A TMR element may furthermore be implemented as a part of a semiconductor device.

[0066] In addition to the magnetic flux density, the device 1 can advantageously additionally detect another physical variable. This physical variable can be, in particular, a temperature value. For this purpose, a temperature measuring element can be provided either in the sensor 2 or, alternatively, on the carrier element 2.1. In this case, the temperature in the region of the sensor 2 can be measured either, for example, by a thermistor, or the temperature in the field-sensitive region of the sensor 2 can be measured, for example, by a microbolometer element or a pyrometer.

[0067] During the approach process, the ferromagnetic tool 4 is moved toward the end of the device 1 at which the sensor 2 is located. The magnetic flux density of the ferromagnetic tool 4 located at the measuring distance d is then measured by the sensor 2. The ferromagnetic tool 4 can be moved, for example, in the z direction during the measuring process. In addition or alternatively, the ferromagnetic tool 4 can also be rotated about its longitudinal axis.

[0068] As soon as the ferromagnetic tool 4 is located in the magnetic bias field of the magnetic field generator 3, the magnetic field lines 3.1 of the magnetic field generator 3 are coupled into the ferromagnetic tool 4. The coupled-in field lines 3.1 are then aligned in a defined manner, i.e., at a local characteristic magnetic flux density, according to the local cross-sectional geometry of the ferromagnetic tool 4. The now modulated magnetic field is measured and evaluated by the sensor 2 with respect to at least one of the three spatial directions x, y, z.

[0069] The magnetic field generator 3 can be designed as a permanent magnet or an electromagnet, wherein the device 1 can include more than one magnetic field generator 3. If more than one magnetic field generator 3 is provided, they can be designed identically or differently, i.e. the device 1 can include, for example, permanent magnets and electromagnets as magnetic field generators 3.

[0070] Such an electromagnet comprises an electromagnetic coil with a defined number of windings, wherein a magnetic field is formed when an electric current flows. Typically, the electromagnetic coil additionally comprises at least one (open) core made of a soft magnetic material (e.g. iron), which guides and strengthens the magnetic field. If a direct current is passed through the electromagnetic coil, the device can be simply cleaned of magnetic chips when necessary by interrupting the current supply to the electromagnet and removing any adhering chips and metal dust manually or automatically (e.g. by compressed air). Alternatively, an alternating current can flow through the electromagnetic coil. In this case, manual or automated cleaning of the device 1 and, in addition or as an alternative, of the ferromagnetic tool 4 is not necessarily required, since the magnetization of the chips and metal dust is evenly neutralized due to the phase changes that occur periodically and repeatedly. In order to obtain particularly good cleaning results, a combination of cleaning with compressed air and cleaning with the aid of an alternating magnetic field can also be carried out.

[0071] According to a second embodiment, which is not shown in greater detail in the figures, the device 1 can have two magnetic field generators 3, one of which is responsible for generating the magnetic bias field and the second magnetic field generator is responsible for demagnetizing the device 1 and, additionally or alternatively, the ferromagnetic tool 4. The second magnetic field generator can be arranged either in the device 1, for example in the form of an electromagnet, or outside the device, for example in the form of an electromagnet with a gradually decaying magnetization.

[0072] When the device 1 is fixedly arranged in the working space of the machine tool, the ferromagnetic tool 4 performs relative movement in at least one spatial direction x, y, z during the approach process and the supplementary or alternative measurement process. The ferromagnetic tool 4 can rotate relative to its own longitudinal axis in particular. When the ferromagnetic tool 4 is fixedly arranged in the working space of the machine tool, the device 1 can be moved relatively in at least one spatial direction x, y, z around the ferromagnetic tool 4 during the approach process and the supplementary or alternative measurement process, wherein the ferromagnetic tool 4 rotates around its own longitudinal axis. Alternatively or additionally, this can occur on a trajectory around the ferromagnetic tool 4, wherein the ferromagnetic tool 4 rotates in particular around its own longitudinal axis. In this case, the device 1 can be placed at the robot arm of an industrial robot as an end effector, for example, so that the end effector can be moved in multiple degrees of freedom.

[0073] The device 1 can be fixedly coupled to a machine tool, for example to a milling table of a milling machine, and the ferromagnetic tool 4 can be moved linearly toward the fixed device 1 , wherein the ferromagnetic tool 4 can be rotated at a defined speed if necessary.

[0074] Alternatively, the ferromagnetic tool 4 can be fixedly coupled to the machine tool, for example to the headstock of a lathe, and the device 1 can be moved toward the ferromagnetic tool 4 by a linear method, for example on a slide.

[0075] As in Figure 1 As shown in FIG. 1 , the magnetic field lines 3.1 of the permanent magnet 3 are coupled into the ferromagnetic tool 4 through the sensor 2 according to the first embodiment. The influence of the magnetic bias field of the permanent magnet 3 is compensated during the signal evaluation or signal correction, so that only the modulated magnetic field of the ferromagnetic tool 4 is taken into account when generating the actual course of the magnetic flux density.

[0076] Figure 2 The highly schematic illustration shows the coupling process of the magnetic field of the permanent magnet 3 of the device 1 into the ferromagnetic tool 4 rotating about its longitudinal axis. The coupling of the magnetic bias field into the ferromagnetic tool 4 is strongly dependent on the rotation angle φ or the local position of the cutting edge and the chip groove in the longitudinal or cross section of each infinitesimal width of the ferromagnetic tool 4.

[0077] exist Figure 2 In the following explanation of a to 2d, for the considered cross section of the ferromagnetic tool 4 it applies that z is constant and φ is varied in the clockwise direction.

[0078] Here, Figure 2 a shows a cross section through the ferromagnetic tool 4 at time t1 , wherein the profile of the ferromagnetic tool 4 is aligned such that the magnetic field lines 3 . 1 of the permanent magnet 3 are approximately parallel to the x-axis and are coupled through the sensor 2 to the ferromagnetic tool 4 .

[0079] exist Figure 2 At time point t2 in b, Figure 2 The angular position of the cross section of the ferromagnetic tool 4 shown in a has changed by several degrees, which leads to a characteristic deflection of the magnetic field lines 3.1 of the permanent magnet 3. These magnetic field lines are now coupled intensified into that sub-region of the cross section of the ferromagnetic tool 4 with the smallest measuring distance d, which leads to an increase in the magnetic flux density there.

[0080] This effect is Figure 2 c is more obvious. Figure 2 c shows the coupling-in of the magnetic field lines 3.1 at time t3. At this time, the ferromagnetic tool 4 has been moved further by several angles and there is now a still small sub-region of the ferromagnetic tool 4 with the smallest measuring distance d, which leads to a higher magnetic flux density in this sub-region.

[0081] Finally, in Figure 2 d, the cutting edge of the ferromagnetic tool 4 is at a maximum measuring distance d, so that a chip groove is present relative to the sensor 2. In such an angular position of the ferromagnetic tool 4, the magnetic field lines 3.1 of the permanent magnet 3 characteristically fan out and couple into the ferromagnetic tool 4 over a relatively large sub-area.

[0082] The change in the magnetic field, in particular in terms of strength and direction, is measured as a function of the relative angular position φ between the ferromagnetic tool 4 and the sensor 2. The measured values ​​that occur here can be used to create the actual change process. If necessary, the actual change process can be adapted by a signal correction integrated on the carrier element 2.1 or alternatively downstream in the device 1, so that only the modulated magnetic field of the ferromagnetic tool 4 is examined in the subsequent signal evaluation.

[0083] Figure 3 By way of example, two actual curves are shown in the form of two function graphs which were produced during a measurement process of a ferromagnetic solid carbide drill 4 with a diameter of 3.4 mm. The ferromagnetic drill 4 was measured both in the axial direction z and in the circumferential direction φ at a measuring distance d=200 μm. In the curves shown, the magnetic flux density B in the radial direction x of the drill 4 is shown.x measurement.

[0084] Figure 3 The Bx-z diagram in a shows the measurement along the drill bit 4 in the z direction at a fixed angular position φ of the drill bit 4. In the depicted function graph, the area of ​​the cutting edge of the drill bit 4 is clearly shown in the form of four peaks or extreme values. If a part of the drill bit 4 were to break, for example at the break line A, this would result in a signal change and the peak of the first cutting edge seen from below would not appear at z≈40 mm. The dotted line L shows the expected course of the measured signal in the case of such a tool break. In particular, the function graph shown can be used to identify geometrical or total tool breakage at an early stage.

[0085] Alternatively, the cutting edge of the drill bit 4 can also be measured in the circumferential direction φ, such as Figure 3 It can be seen from the change process shown in b. x In the diagram, the two cutting edges of the drill 4 are clearly visible as two peaks at the measuring point constant relative to z. For example, the number, geometry or defects or fractures of the cutting edges of the tool to be measured can be detected particularly well based on the function diagram shown.

[0086] In particular, a heat map H is also suitable as a further representation, which represents the heat map H in a combined manner from Figure 3 a and Figure 3 b function graph information. For example, the measured magnetic flux density B x is expressed as a function of the circumferential direction φ and the axial direction z of the drill 4. Such an evaluation is suitable, for example, for a detailed analysis of the ferromagnetic tool with regard to the geometry, the number of cutting edges, the material of the drill 4 or the cut material, for early detection of total tool breakage and in particular for detecting defects or cracks.

[0087] In addition to the explained exemplary embodiments of the device according to the invention, further design possibilities exist within the scope of the invention.

[0088] It is thus also possible to move the device 1 according to the invention in only one spatial direction x, y, z. Such an arrangement of a ferromagnetic tool 4 and the device 1 according to the invention is conceivable, for example, when measuring the cutting edge of an indexable insert in the working area of ​​a lathe. The device 1 can be located on a slide, for example, and the device 1 can be moved toward the indexable insert clamped in the tool holder. In this case, the measurement signal can also be evaluated by the characteristic course of the magnetic flux density. However, in this case, the mere presence of extreme values ​​in the actual course of the change would already indicate wear.

[0089] Method for contactless fracture monitoring and additionally or alternatively wear monitoring Figure 5 50. The program sequence for testing the ferromagnetic tool 4 is started or initialized (step 51) by the control of the machine tool, either by an operator or automatically at time intervals.

[0090] Thus, the ferromagnetic tool 4 and the device 1 are brought relatively close 52 until the measuring distance d is reached. For example, the machine tool moves the ferromagnetic tool 4 in the working space of the machine tool toward the device 1 fixedly arranged in the working space. The ferromagnetic tool 4 can be relatively rotated around its longitudinal axis in a defined manner during the entire process.

[0091] In a subsequent step 53 , a magnetic bias field caused by at least one magnetic field generator 3 of the device 1 is coupled in.

[0092] In the subsequent step 54 of measurement, the magnetic field modulated by the ferromagnetic tool 4 is measured by the sensor 2 with respect to the magnetic flux density, wherein other physical variables (eg at least one temperature value) can also be detected if necessary. These data then form a database of the actual course of events.

[0093] The previously determined measurement results from step 54 are then evaluated 55, wherein a signal correction is also performed in this step. Evaluation 55 can be performed automatically and computer-assisted (eg by an artificial neural network), manually by an operator or by a combination of both processing methods.

[0094] In the penultimate step 56, the evaluation result or the evaluation results can be submitted to an output unit 68, 68'. In the output unit 68, 68', the evaluation results can be stored in a storage unit and transmitted to a user in addition or alternatively. Such transmission can be performed visually via a screen of the machine tool, acoustically via an audio output unit, etc. Finally, in step 57, the program flow 50 ends.

[0095] In this context, it should be noted that the ferromagnetic tool 4 only has to stay at the measuring distance d during step 54 ("measure"), if necessary rotated relative to its longitudinal axis, during the program sequence 50. During the subsequent steps 55 to 57, the machine tool can already execute another program sequence in parallel with the program sequence 50 being executed, i.e., for example, the workpiece can continue to be machined using the ferromagnetic tool 4.

[0096] Figure 6 Shown in Figure 5 A schematic flow chart 60 of sub-steps of the method step evaluation 55 is shown in FIG.

[0097] Submodule evaluation 61 is a subelement of method step evaluation 55. Once submodule 61 is called, substep 62 is executed, which calls the desired state information of the ferromagnetic tool 4 to be measured from the database in order to subsequently derive the desired change process therefrom. Here, these desired state information can already exist as completed desired change processes, or can still be calculated or generated. The calculation of the desired state information can be performed, for example, based on the state information of the corresponding, unused ferromagnetic tool and the usage time of the ferromagnetic tool 4 stored in the storage unit, should there be no desired state information of the measurement that has already occurred before.

[0098] The subsequent sub-step 63 now compares the actual course of change of the measured data determined in step 54 with the rated course of change called or calculated in sub-step 62, i.e. determines the degree of deviation of the two courses of change. This can be done, for example, for a single, multiple or all actual and rated course of change values. Alternatively, a suitable reference value can be determined as the degree of deviation. For example, the reference value can include the subtraction of the integral of the actual and rated course of change. In addition, in particular with respect to other physical variables, such as the local temperature distribution in the ferromagnetic tool 4, the rated and actual course of change can be normalized here. It is also conceivable that the deviation of the two courses of change is determined only section by section, for example for subsections of the ferromagnetic tool 4 that are particularly susceptible to wear phenomena or tool breakage.

[0099] If the extent of the deviation does not exceed a defined threshold value (No path 66), no further analysis of the measured value is performed and the output unit 68 is informed that there is no deviation. For a new and unused ferromagnetic tool 4, such a minimum deviation can be obtained, for example, within the measurement accuracy of the sensor 2.

[0100] If the degree of deviation is higher than or equal to the threshold value (path 65), a depth analysis (sub-step 67) is performed, or alternatively, the measurement or workpiece processing is terminated. In the case of such a depth analysis, the measurement data, the actual change process, the rated change process, and the deviation of the rated change process from the actual change process in addition or alternatively are evaluated more accurately. In particular, the depth analysis includes the evaluation of the presence and classification of wear forms, wear parameters, the position and state of the cutting edge, the position and state of the chip groove, the material composition, chip adhesion or contamination, and the further intensity distribution of the ferromagnetic tool 4 in addition or alternatively. Such a depth analysis can be performed either algorithmically, especially by machine learning methods, or manually by the operator. A combination of the two methods is also conceivable. One or more results of sub-step 67 are finally transmitted to the output unit 68', for example in the form of a heat map H, and the sub-module 61 (sub-step 69) is finally terminated.

[0101] The output unit 68, 68' can be a screen of the machine tool. The result is then processed in a graphical manner so that the operator can intuitively understand what the current status of the ferromagnetic tool 4 in use is.

[0102] If wear or breakage of the ferromagnetic tool 4 is detected by the device 1 , for example, a stop of the further processing of the workpiece can occur and the operator can be informed of this event in the form of a visual output and, additionally or alternatively, an audio output.

[0103] In addition, a storage unit can be provided which stores historical data of the evaluation or in-depth analysis in a non-volatile memory. In the case of a machine tool with a tool turret, all evaluations or in-depth analyses of the device 1 are thus accessible for all ferromagnetic tools located in the tool turret. The display of the results via the output unit 68, 68' is then not limited to the ferromagnetic tool 4 in use.

Claims

1. A device (1) for contactless monitoring of fracture and / or wear of ferromagnetic tools (4) in machine tools, comprising a sensor (2) and at least one magnetic field generator (3), wherein the device (1) is capable of measuring local changes in the magnetic flux density (B) at a measuring distance (d) by means of a sensor (2) and of evaluating them by means of an electronic evaluation unit, The sensor (2) is constructed such that: The longest extension of the sensor in the spatial directions (x, y, z) is at most 500 μm, and The sensor (2) can measure a magnetic field in at least one spatial direction (x, y, z).

2. The device (1) according to claim 1, wherein the at least one magnetic field generator (3) and the sensor (2) are arranged along a straight line, which extends parallel to or orthogonally to the longitudinal axis of the ferromagnetic tool (4).

3. A device (1) according to any of the preceding claims, wherein the device (1) additionally comprises a housing (5), wherein the sensor (2) and the at least one magnetic field generator (3) are arranged in the housing (5) so that their magnetic bias field passes through the sensor (2) and can be coupled into the ferromagnetic tool (4).

4. The device (1) according to any of the preceding claims, wherein the sensor (2) comprises at least one Hall element (2.1) and / or at least one TMR element (2.1').

5. The device (1) according to any of the preceding claims, wherein, in addition to measuring the magnetic flux density (B), the sensor (2) is also capable of detecting at least one other physical variable.

6. The device (1) according to any of the preceding claims, wherein the device (1) is designed to remove contaminants at the device (1) and / or at the ferromagnetic tool (4) by means of compressed air and / or an alternating magnetic field.

7. A method for contactless monitoring of the fracture and / or wear of a ferromagnetic tool (4) in a machine tool by means of a device (1), the device comprising a sensor (2) for point-wise measurement and at least one magnetic field generator (3), the method comprising the following steps: Bring the ferromagnetic tool (4) and the device (1) relatively close; · coupling a magnetic bias field into the ferromagnetic tool (4); Measuring the magnetic flux density of the magnetic field modulated by the ferromagnetic tool (4) in at least one spatial direction (x, y, z); Signal correction and signal evaluation are performed for determining the geometry of the ferromagnetic tool (4).

8. The method according to claim 7, wherein the signal correction and the signal evaluation are performed electronically within the device (1).

9. The method according to claim 7 or 8, wherein the result of the signal evaluation is transmitted to a storage unit and / or an output unit.

10. The method according to claim 7 , wherein at least one of the following variables is additionally determined: The spatial position of the ferromagnetic tool (4); The distance (d) between the ferromagnetic tool (4) and the sensor (2); · angular position (φ) of the ferromagnetic tool (4); The rotation speed of the ferromagnetic tool (4); The diameter and / or length of the ferromagnetic tool (4); The temperature of the ferromagnetic tool (4).

11. The method according to any one of claims 7 to 10, wherein In the case of a stationary arrangement of the device (1), the ferromagnetic tool (4) is moved relatively in a spatial direction (x, y, z) during the approach process and / or the measuring process and in the process rotates about its longitudinal axis, or When the ferromagnetic tool (4) is arranged in a fixed manner, the device (1) is moved relatively in a spatial direction (x, y, z) and / or on a trajectory around the ferromagnetic tool (4) during the approach process and / or the measuring process, The ferromagnetic tool (4) rotates around its own longitudinal axis.

12. The method according to any one of claims 7 to 11, wherein the evaluating comprises the following steps: · calling up or calculating a desired course of at least one desired variable of the ferromagnetic tool (4), comparing the called or calculated setpoint profile with the measured actual profile of at least one actual variable of the ferromagnetic tool (4), When determining deviations: – determine the extent of the deviation, and – If a defined threshold is exceeded: perform in-depth analysis of the measurement and / or abort the measurement and / or abort the workpiece machining. 13 . The method according to claim 12 , wherein the threshold value additionally takes into account at least one of the variables from claim 10 .

14. A method according to any one of the preceding claims 7 to 13, wherein data are evaluated in a computer-aided manner during in-depth analysis regarding wear form, wear parameters, position and condition of the cutting edge, position and condition of the chip groove, material composition, chip adhesion and / or strength distribution of the ferromagnetic tool (4).

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