Device and method for non-contact fracture and / or wear monitoring

Abstract

The invention relates to a device and a method for non-contact fracture monitoring and, additionally or alternatively, for non-contact wear monitoring in a machine tool. The device comprises a sensor and at least one magnetic field generator. Using the sensor, the device measures local changes in magnetic flux density at a defined measuring distance and electronically evaluates the measurement signal by means of an electronic evaluation unit. The sensor is designed such that its longest dimension in any spatial direction is at most 500 µm, and a magnetic field can be measured by the sensor in at least one spatial direction.

Description

AREA OF TECHNOLOGY

[0001] The invention relates to a device and a method for the non-contact detection of breakage and wear phenomena on ferromagnetic tools according to independent claim 1 and independent claim 7, respectively.

[0002] When a machine tool is equipped with a tool for machining a workpiece, and the workpiece is being machined according to its geometric shape, unexpected and unforeseen damage can occur to the tool, such as total breakage or minor chipping of the cutting edges. For example, a total tool breakage not only results in a sudden stress on the machine tool but also frequently damages the workpiece. If such a total tool breakage goes unnoticed, it generally leads to defective machining of the workpieces in subsequent steps of the corresponding machine tool, which in turn results in an undesirably high scrap rate. Even wear and tear in the form of small defects or chipping can negatively affect workpiece machining.

[0003] Therefore, a device for the early detection of breakage and / or wear is one of the most important factors in preventing damage to a machine tool and improving reliability during machining. STATE OF THE ART

[0004] Patent application DE 36 08 572 A discloses a method for the non-contact monitoring of tool breakage and wear, in which the change in position of two adjacent machine parts equipped with weak magnets, at least one of which is subjected to forces during machining, is continuously measured and monitored inductively. The deformation of a tool, a tool holder, or the tool base is used as a measure of tool wear, since the force on the tool increases with increasing wear.

[0005] A disadvantage of this method is that monitoring breakage and wear on the tool using the indirect measurement method is relatively inaccurate, as only larger chips or cracks can be detected. Monitoring the local cutting geometry is not possible with this method. SUMMARY OF THE INVENTION

[0006] The invention is based on the objective of providing a device and a method by which a ferromagnetic tool can be reliably and non-contact checked for breakage and / or wear. The device is insensitive to contamination, cost-effective to manufacture, and simultaneously achieves a relatively high level of measurement accuracy.

[0007] This problem is solved according to the invention by the features of claims 1 and 7. Advantageous embodiments and further developments are specified in the respective dependent claims.

[0008] The device according to the invention is suitable for non-contact fracture monitoring and, additionally or alternatively, for wear monitoring of ferromagnetic tools in a machine tool. The device comprises a sensor and at least one magnetic field generator, which can, for example, be designed as a permanent magnet. The device uses the sensor to measure local changes in magnetic flux density at a defined measuring distance and electronically evaluates the measurement signal by means of an evaluation unit. The sensor is designed such that the longest extent of the sensitive area in any spatial direction is at most 500 µm, and a magnetic field can be measured by the sensor in at least one spatial direction.

[0009] According to an advantageous embodiment of the invention, the at least one magnetic field generator and the sensor can be arranged along a straight line which runs parallel or orthogonal to the longitudinal axis of the ferromagnetic tool.

[0010] In a further 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 in such a way that its magnetic bias field passes through the at least one sensor and is coupled into the ferromagnetic tool.

[0011] The sensor should ideally include at least one Hall element and, additionally or alternatively, at least one TMR element.

[0012] According to an advantageous embodiment of the invention, the sensor is able to detect at least one other physical quantity in addition to measuring the magnetic flux density.

[0013] The physical quantity can be, for example, a state variable such as pressure, temperature, etc. For instance, it could be temperature values ​​measured within the sensor's field-sensitive range, particularly those related to the ferromagnetic tool.

[0014] Advantageously, the device is designed to remove contaminants from the device and, additionally or alternatively, from the ferromagnetic tool using compressed air and, additionally or alternatively, using an alternating magnetic field.

[0015] According to a further aspect, the invention comprises a method for non-contact fracture monitoring and, additionally or alternatively, for wear monitoring of a ferromagnetic tool in a machine tool by means of a device. The device comprises a point-measuring sensor and at least one magnetic field generator. The method comprises the following steps: • Relative approach of ferromagnetic tool and device; • Coupling a magnetic bias field into the ferromagnetic tool; • Measuring the magnetic flux density of the magnetic field modulated by the ferromagnetic tool in at least one spatial direction; • Correcting and evaluating the measurement signal to determine the geometry of the ferromagnetic tool.

[0016] In particular, the special point-like design of the sensor allows for a high resolution of the measurement results.

[0017] In a further development, signal correction and signal evaluation are carried out electronically within the device.

[0018] Advantageously, the result of the signal evaluation is transmitted to a storage unit after completion and additionally or alternatively to an output unit.

[0019] According to a beneficial further training, at least one of the following quantities will also be determined: • Spatial position of the ferromagnetic tool; • Measuring distance of the ferromagnetic tool to the sensor; • Angular position of the ferromagnetic tool; • Rotational speed of the ferromagnetic tool; • Diameter and, additionally or alternatively, length of the ferromagnetic tool; • Temperature of the ferromagnetic tool.

[0020] Advantageously, in a stationary arrangement of the device, the ferromagnetic tool moves relatively in at least one spatial direction during an approach process and, additionally or alternatively, during a measurement process. The ferromagnetic tool can rotate relatively about its own longitudinal axis. Alternatively, in the case of a stationary arrangement of the ferromagnetic tool, the device can move relatively in at least one spatial direction around the ferromagnetic tool during an approach process and, additionally or alternatively, during a measurement process, with the ferromagnetic tool rotating about its own longitudinal axis. Alternatively or additionally, the movement of the device can also occur along a path around the ferromagnetic tool, with the ferromagnetic tool rotating about its own longitudinal axis.

[0021] In further detail, the evaluation includes the following steps: • Retrieving or calculating a target curve for at least one target parameter of the ferromagnetic tool; • Comparing the retrieved or calculated target curve with a measured actual curve of at least one actual parameter of the ferromagnetic tool; • If a deviation is detected: - Determination of the degree of deviation and - If a defined threshold is exceeded: Perform a depth analysis of the measurement and, additionally or alternatively, terminate the measurement and, additionally or alternatively, terminate the workpiece processing.

[0022] The threshold value should ideally also take into account at least one of the following factors: • Spatial position of the ferromagnetic tool; • Measuring distance of the ferromagnetic tool to the sensor; • Angular position of the ferromagnetic tool; • Rotational speed of the ferromagnetic tool; • Diameter and, additionally or alternatively, length of the ferromagnetic tool; • Temperature of the ferromagnetic tool.

[0023] According to an advantageous further development, the measurement data are evaluated during the depth analysis with regard to wear patterns, wear parameters, position and condition of the cutting edges, position and condition of the chip spaces, the material composition, the chip adhesion and additionally or alternatively an intensity distribution of the ferromagnetic tool.

[0024] The invention is further explained below with regard to other features and advantages by means of a description of exemplary embodiments and with reference to the accompanying schematic drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] They show: Fig. 1 a highly schematic representation of an embodiment of the device according to the invention; Fig. 2 a highly schematic representation of the measuring principle of the device according to the invention in a sectional view; Fig. 3 two measurements of a ferromagnetic tool with an exemplary first and second actual curve; Fig. 4 a measurement of a ferromagnetic tool with an exemplary third actual curve; Fig. 5 a schematic representation of the method according to the invention as a flowchart; Fig. 6 a schematic representation of the in Fig. The 5 steps in the "Evaluate" section comprised sub-steps. DESCRIPTION OF THE EXECUTION FORMS

[0026] Some specific embodiments of the present invention are described in more detail below with reference to the drawings.

[0027] The device 1 according to the invention is suitable for use in the working area of ​​machine tools where a ferromagnetic tool 4 is to be checked for breakage and, additionally or alternatively, for 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.

[0028] In the Fig. Figure 1 shows the ferromagnetic tool 4 and the device 1 according to the invention, which comprises a housing 5, a support element 2.1 with sensor 2, and a magnetic field generator 3. In the presented embodiment, 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 the distal end of the device 1 that is in the immediate vicinity of the ferromagnetic tool 4, with a defined minimum measuring distance d in the form of an air gap between the ferromagnetic tool 4 and the device 1.

[0029] 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 which is 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 still lie on a straight line.

[0030] The straight line – along which the at least one magnetic field generator 3 and the sensor 2 are located – can therefore also run parallel to the longitudinal direction of the ferromagnetic tool 4, in which case only the sensor 2 and the at least one magnetic field generator 3 lie on the straight line parallel to the longitudinal axis of the ferromagnetic tool 4. Ideally, the sensor 2 should be positioned closer to the tool holder of the ferromagnetic tool 4 than the at least one magnetic field generator 3.

[0031] The measuring distance d defines the distance between the surface of the device 1 and the arc of the maximum peripheral parts of a cross-section of the ferromagnetic tool 4. The measuring distance d is generally chosen such 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 remain constant during each test procedure or alternatively be varied, for example, depending on the diameter of the ferromagnetic tool 4 or its current temperature or ambient temperature.

[0032] A ferromagnetic tool 4 is understood to be a tool for manufacturing workpieces where a machine tool defines or influences the relative movement(s) between the device 1 and the ferromagnetic tool 4 within the machine tool's working area. In particular, this includes single- and multi-edged tools for machining processes that possess cutting materials with ferromagnetic properties. Examples include drills, milling tools, reamers, broaching tools, turning tools, and indexable inserts made of tool steel or carbide.

[0033] The ferromagnetic tool 4 can, for example, be moved by the machine tool in all three spatial directions x, y, z and rotated in a defined manner around its longitudinal axis (Φ-direction).

[0034] A magnetic bias field from at least one magnetic field generator 3 is coupled into the ferromagnetic tool 4, generating the magnetic field modulated by the ferromagnetic tool 4. The magnetic field modulated by the ferromagnetic tool 4 is characterized by a local magnetic flux density that depends on the local cross-sectional geometry of the ferromagnetic tool 4. This results in a concentration of magnetic field lines at the cutting edges and thus an increased magnetic flux density. In contrast, a comparatively low magnetic flux density prevails in the chip spaces of the ferromagnetic tool 4, allowing for a differentiation between cutting edges and chip spaces.

[0035] Sensor 2 is capable of measuring the magnetic flux density at a defined measuring distance d in at least one spatial direction x, y, z. The measurement is performed at a point, with the resolution being determined by the sensitive area of ​​sensor 2. Advantageously, the sensitive area has a dimension of less than 500 µm, particularly less than 200 µm, and advantageously less than 100 µm, in the spatial direction x, y, z at its longest extent. The dimensions of the sensitive area of ​​sensor 2 are crucial for the spatial resolution of sensor 2. The bandwidth of sensor 2 describes the (analog) measurement frequency and is advantageously at least 10 kHz.

[0036] Device 1 measures the magnetic flux density with exactly one sensor in three spatial directions x, y, z. Sensor 2 can, for example, comprise three sensitive surfaces, which can consist of three mutually orthogonally arranged Hall elements or, additionally or alternatively, TMR elements, enabling measurement of the magnetic flux density in the three spatial directions x, y, z. However, it is also possible to perform a measurement of the magnetic flux density in only one or two spatial directions x, y, z. The choice of the spatial direction(s) x, y, z is situation-dependent, i.e., depends, for example, on the relative position of Device 1 to the ferromagnetic tool 4, whereby the spatial direction(s) x, y, z that provides the most reliable measurement signal(s) is / are always included in the measurement or evaluation.

[0037] A Hall element is a Hall effect element, which can be implemented, for example, as a semiconductor device. The Hall element is particularly capable of measuring at least one Hall voltage, which can be used to determine at least one local directional component of a magnetic field.

[0038] A TMR element is an element that utilizes the tunnel magnetoresistance effect to determine at least one local directional component of a magnetic field. Furthermore, the TMR element can be implemented as part of a semiconductor device.

[0039] The device 1 can advantageously detect an additional physical quantity besides the magnetic flux density. This physical quantity can, in particular, be a temperature value. For this purpose, a temperature measuring element can either be provided within the sensor 2 or, alternatively, a temperature measuring element can be provided on the support element 2.1. The temperature can be measured either in the area of ​​the sensor 2, e.g., by a thermistor, or within the field-sensitive area of ​​the sensor 2, e.g., by a microbolometer element or pyrometer.

[0040] During an approach process, the ferromagnetic tool 4 is moved to the end of the device 1 where the sensor 2 is located. The sensor 2 then measures the magnetic flux density of the ferromagnetic tool 4 at a measuring distance d. The ferromagnetic tool 4 can be moved during the measurement process, for example, in the z-direction. Alternatively, or additionally, the ferromagnetic tool 4 can also be rotated about its longitudinal axis.

[0041] The magnetic field lines 3.1 of the magnetic field generator 3 couple into the ferromagnetic tool 4 as soon as it is located within the magnetic bias field of the magnetic field generator 3. The coupled field lines 3.1 then align themselves in a defined manner depending on the local cross-sectional geometry of the ferromagnetic tool 4, i.e., with a locally characteristic magnetic flux density. This 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.

[0042] The magnetic field generator 3 can be configured as a permanent magnet or as an electromagnet, and the device 1 can include more than one magnetic field generator 3. If more than one magnetic field generator 3 is provided, these can be identical or different, i.e., the device 1 can, for example, include a permanent magnet and an electromagnet as magnetic field generators 3.

[0043] Such an electromagnet comprises an electromagnetic coil with a defined number of windings, in which a magnetic field is generated when current flows. Typically, the electromagnetic coil also includes at least one (open) core made of a magnetically soft material (e.g., iron), which guides and amplifies the magnetic field. If a direct current flows through the electromagnetic coil, the device can be easily cleaned of magnetic chips, if necessary, by interrupting the power supply to the electromagnet and removing any adhering chips and metal dust manually or automatically (e.g., with compressed air). Alternatively, an alternating current can flow through the electromagnetic coil.Manual or automated cleaning of the device 1 and, additionally or alternatively, of the ferromagnetic tool 4 is not strictly necessary in this case, since the periodic and repeated phase change neutralizes the magnetization of the chips and metal dust on average. To achieve a particularly good cleaning result, a combination of compressed air cleaning and cleaning using an alternating magnetic field can also be used.

[0044] According to a second embodiment, which is not shown in 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 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 – e.g., in the form of an electromagnet – or outside the device 1 – e.g., in the form of an electromagnet with a stepwise decaying magnetization.

[0045] When the device 1 is stationary in the workspace of a machine tool, the ferromagnetic tool 4 is moved relative to the device 1 in at least one spatial direction x, y, z during an approach process and, additionally or alternatively, during a measuring process. The ferromagnetic tool 4 can, in particular, rotate relative to the device 1 about its own longitudinal axis. Alternatively, this movement can occur along a path around the ferromagnetic tool 4, with the tool rotating around its own longitudinal axis.In this case, the device 1 can, for example, be attached to a robot arm of an industrial robot as an end effector, which can be moved in several degrees of freedom.

[0046] The device 1 can be stationary and coupled to a machine tool - for example, to a milling table of a milling machine - and the ferromagnetic tool 4 can be moved towards the stationary device 1 by a linear process, whereby the ferromagnetic tool 4 can rotate at a defined speed if required.

[0047] Alternatively, the ferromagnetic tool 4 can be stationary and coupled to a machine tool - for example, to a headstock of a lathe - and the device 1 can be moved to the ferromagnetic tool 4 by a linear process - for example, on a slide.

[0048] As in Fig. Figure 1 shows that the magnetic field lines 3.1 of a permanent magnet 3 are coupled into the ferromagnetic tool 4 through the sensor 2 according to a first embodiment. The influence of the magnetic bias field of the permanent magnet 3 is compensated during signal evaluation or signal correction, so that only the modulated magnetic field of the ferromagnetic tool 4 is taken into account when generating an actual curve of the magnetic flux density.

[0049] Fig. Figure 2 shows, in a highly schematic representation, 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 depends strongly on the rotation angle ϕ or the local position of the cutting edges and the chip spaces in each infinitesimally wide longitudinal or cross-section of the ferromagnetic tool 4.

[0050] In the following explanation of the Fig. For the cross-section of the ferromagnetic tool 4 considered in 2a to 2d, z is constant and ϕ is varied clockwise.

[0051] Fig. Figure 2a shows a cross-section through the ferromagnetic tool 4 at time t1, wherein the profile of the ferromagnetic tool 4 is oriented such that the magnetic field lines 3.1 of the permanent magnet 3 couple approximately parallel to the x-axis and through the sensor 2 into the ferromagnetic tool 4.

[0052] At time t2 in Fig. 2b the angular position of the depicted cross-section of the ferromagnetic tool 4 from Fig. 2a changed by a few degrees, resulting in a characteristic deflection of the magnetic field lines 3.1 of the permanent magnet 3. These now couple more strongly into that part of the cross-section of the ferromagnetic tool 4 which has the smallest measuring distance d, leading to an increase in the magnetic flux density there.

[0053] This effect is even more pronounced in Fig. 2c is pronounced, which shows the coupling of the magnetic field lines 3.1 at time t3. At this time, the ferromagnetic tool 4 has moved a few degrees further and now an even smaller section of the ferromagnetic tool 4 with a minimum measuring distance d is present, which leads to an even higher magnetic flux density in this section.

[0054] Finally, the cutting edges of the ferromagnetic tool are 4 in Fig. 2d at a maximum measuring distance d such that a chip space lies opposite the sensor 2. The magnetic field lines 3.1 of the permanent magnet 3 fan out characteristically at such an angular position of the ferromagnetic tool 4 and couple into the ferromagnetic tool 4 over a comparatively large area.

[0055] Changes in the magnetic field, particularly in strength and direction, are measured as a function of the relative angular position ϕ between the ferromagnetic tool 4 and the sensor 2. The resulting measured values ​​can be used to generate a current trend. If necessary, the current trend can be adjusted by a signal correction integrated on the carrier element 2.1 or, alternatively, downstream within the device 1, so that only the modulated magnetic field of the ferromagnetic tool 4 is examined in the subsequent signal evaluation.

[0056] Fig. Figure 3 shows two exemplary actual curves in the form of two function graphs, which were generated during a measurement process of a ferromagnetic solid carbide drill bit 4 with a diameter of 3.4 mm. The ferromagnetic drill bit 4 was measured both axially z and circumferentially ϕ at a measuring distance d = 200 µm. In the curves shown, the measurement of the magnetic flux density B is shown in each case. x shown in the radial direction x of the drill bit 4.

[0057] The B x -z-diagram in Fig. Figure 3a shows the measurement in the z-direction along the drill bit 4 at a fixed angular position ϕ of the drill bit 4. In the depicted function graph, the cutting edge regions of the drill bit 4 clearly stand out as four peaks or extrema. If part of the drill bit 4 were to break off, for example at the fracture line A, this would lead to a change in the signal, and the peak of the first cutting edge (viewed from below) at z ≈ 40 mm would not appear. The dashed line L indicates the expected course of the measurement signal in the event of such a tool breakage. The depicted function graph allows for the early detection of geometric dimensions or a total tool breakage.

[0058] Alternatively, the cutting edges of the drill bit 4 can also be measured in the circumferential direction ϕ, as in the Fig. The course shown in 3b can be seen. From the ϕ-B xIn the diagram, the two cutting edges of drill bit 4 clearly stand out as two peaks at a measurement point constant with respect to z. The function graph shown is particularly useful for determining, for example, the number of cutting edges, geometric dimensions, or defects or chipping of the tool being measured.

[0059] Another suitable representation is a heatmap H, which displays the information from the function graphs. Fig. 3a and Fig. 3b combined represents (see Fig. 4) This includes, for example, the measured magnetic flux density B xThe value is represented 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 detailed analyses of a ferromagnetic tool with regard to the geometric dimensions, the number of cutting edges, the material of the drill 4 or the cutting materials, the early detection of total tool breakage, and in particular for the detection of defects or chipping.

[0060] In addition to the described embodiment of the device according to the invention, there are further possible embodiments within the scope of the present invention.

[0061] It is also possible to move the device 1 according to the invention only in one spatial direction x, y, z. For example, such an arrangement of a ferromagnetic tool 4 and the device 1 according to the invention would be conceivable when measuring the cutting edges of an indexable insert in the working area of ​​a lathe. The device 1 could, for example, be located on a slide and moved towards the indexable insert clamped in a tool holder. In this case, the measurement signal could also be evaluated via characteristic curves of the magnetic flux density. However, in this case, the mere presence of extrema in the actual curve would already indicate wear.

[0062] A method for non-contact fracture and, additionally or alternatively, wear monitoring is described in Fig. 5 is shown as a schematic flowchart 50. A program sequence for checking the ferromagnetic tool 4 can be started or initialized (step 51) via the control of the machine tool, either by an operator or automatically within a time interval.

[0063] Subsequently, the ferromagnetic tool 4 and the device 1 are moved relatively close together until the measuring distance d is reached. This can be achieved, for example, by the machine tool moving the ferromagnetic tool 4 within the machine tool's workspace towards the device 1, which is stationary within the workspace. The ferromagnetic tool 4 can rotate in a defined manner about its longitudinal axis throughout the entire process.

[0064] In a subsequent step 53, a magnetic bias field is coupled in, generated by at least one magnetic field generator 3 of the device 1.

[0065] In the subsequent step 54, the magnetic field modulated by the ferromagnetic tool 4 is measured by sensor 2 with respect to the magnetic flux density. If necessary, an additional physical quantity can also be recorded (e.g., at least a temperature value). This data then forms the basis for a record of the actual trend.

[0066] The following step (55) involves the evaluation of the previously determined measurement results from step 54, during which a signal correction is also performed. This evaluation (55) can be automated and computer-assisted (e.g., by an artificial neural network), performed manually by an operator, or using a combination of both processing methods.

[0067] In the penultimate step 56, the evaluation result or multiple evaluation results can be transferred to an output unit 68, 68'. Within the output unit 68, 68', the evaluation result can be stored in a memory unit and additionally or alternatively transmitted to a user. Such transmission can be visual, for example, via a screen on the machine tool, audible via an audio output unit, etc. Finally, in step 57, the program sequence 50 is terminated.

[0068] It should be noted that the ferromagnetic tool 4 only needs to remain at the measuring distance d – possibly rotating relative to its longitudinal axis – during program sequence 50 during step 54 ("Measuring"). During subsequent steps 55 to 57, another program sequence can be executed by the machine tool control in parallel with program sequence 50, i.e., for example, the machining of a workpiece with the ferromagnetic tool 4 can continue.

[0069] Fig. Figure 6 shows a schematic flowchart of 60 of the sub-steps of the process. Fig. Evaluate the 5th step of the procedure shown.

[0070] The sub-module Evaluation 61 is a component of the process step Evaluation 55. Once sub-module 61 is called, sub-step 62 is executed, which retrieves target state information for the ferromagnetic tool 4 to be measured from a database in order to derive a target profile from it. This target state information may already be available as a complete target profile or may need to be calculated or generated. The calculation of the target state information can, for example, be based on the state information of a corresponding, unused ferromagnetic tool and the operating time of the ferromagnetic tool 4 stored in the memory unit, should no target state information from a previous measurement be available.

[0071] The subsequent sub-step 63 now compares the actual trend of the measurement data determined in step 54 with the target trend retrieved or calculated in sub-step 62; that is, the degree of deviation between the two trends is determined. This can be done, for example, for individual, several, or all actual and target trend values. Alternatively, a suitable reference value can be determined as the degree of deviation. This reference value could, for example, be the subtraction of the integrals of the actual and target trends. Additionally, the target and actual trends can be normalized, particularly with respect to another physical quantity, such as the local temperature distribution in the ferromagnetic tool 4.It is also conceivable that the determination of the deviation with respect to both curves is carried out only section by section, for example for subsections of the ferromagnetic tool 4 that are particularly susceptible to wear or tool breakage.

[0072] If the degree of deviation does not exceed a defined threshold (No path 66), no further analysis of the measured values ​​is performed, and the output unit 68 is informed that no deviation exists. Such a minimal deviation can occur, for example, within the measurement accuracy of sensor 2 for a new and unused ferromagnetic tool 4.

[0073] If, however, the degree of deviation is higher than or equal to the threshold value (Yes path 65), a depth analysis (sub-step 67) is performed, or alternatively, the measurement or workpiece machining is aborted. In such a depth analysis, the measurement data, actual path, target path, and, additionally or alternatively, the deviation between the target and actual paths are evaluated in more detail. In particular, the depth analysis includes an evaluation regarding the presence and classification of wear patterns, wear parameters, position and condition of the cutting edges, position and condition of the chip spaces, the material composition, chip adhesion or contamination, and, additionally or alternatively, a further intensity distribution of the ferromagnetic tool 4. Such a depth analysis can be performed either algorithmically, especially using machine learning methods, or manually by an operator. A combination of both methods is also conceivable.The result(s) of sub-step 67 are finally transmitted to the output unit 68' - e.g. in the form of a heatmap H - and sub-module 61 is completed (sub-step 69).

[0074] The output unit 68, 68' can be a screen on a machine tool. The results are then presented graphically so that an operator can intuitively understand the current status of the ferromagnetic tool 4 currently in use.

[0075] If wear or breakage of the ferromagnetic tool 4 is detected by the device 1, the further processing of the workpiece can be stopped, for example, and an operator can be notified of the event by means of a visual output and, additionally or alternatively, an audio output.

[0076] Additionally, a storage unit can be provided that saves historical evaluation or in-depth analysis data in non-volatile memory. In the case of a machine tool with a tool turret, this allows access to all evaluations or in-depth analyses of device 1 for all ferromagnetic tools located in the tool turret. The display of the results via output unit 68, 68' is then not limited to the ferromagnetic tool 4 currently in use. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

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[0004]

Claims

[1] Device (1) for contactless breakage and / or wear monitoring of ferromagnetic tools (4) in a machine tool, comprising a sensor (2) and at least one magnetic field generator (3), wherein the device (1) can measure local changes in the magnetic flux density (B) at a measuring distance (d) by means of the sensor (2) and evaluate them by means of an electronic evaluation unit, wherein the sensor (2) is designed such that • its longest dimension in one spatial direction (x, y, z) is not more than 500 µm, and • a magnetic field can be measured in at least one spatial direction (x, y, z) by the sensor (2). [2] 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 runs parallel or orthogonal to the longitudinal axis of the ferromagnetic tool (4). [3] Device (1) according to one 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) in such a way that its magnetic bias field can be coupled through the sensor (2) and into the ferromagnetic tool (4). [4] Device (1) according to one 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] Device (1) according to one of the preceding claims, wherein the sensor (2) can detect at least one further physical quantity in addition to measuring the magnetic flux density (B). [6] Device (1) according to one of the preceding claims, wherein the device (1) is designed to remove contamination on the device (1) and / or on the ferromagnetic tool (4) by means of compressed air and / or alternating magnetic field. [7] Method for contactless breakage and / or wear monitoring of a ferromagnetic tool (4) in a machine tool by means of a device (1) comprising a point-measuring sensor (2) and at least one magnetic field generator (3), with the following steps: • relative approach of the ferromagnetic tool (4) and the device (1); • Coupling of 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, yz); • Signal correction and signal evaluation to determine the geometry of the ferromagnetic tool (4). [8] Method according to claim 7, wherein the signal correction and the signal evaluation are carried out electronically within the device (1). [9] 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] Method according to one of claims 7 to 9, wherein additionally at least one of the following variables is determined: • Spatial position of the ferromagnetic tool (4), • Distance (d) of the ferromagnetic tool (4) to the sensor (2), • Angular position (ϕ) of the ferromagnetic tool (4), • Rotation speed of the ferromagnetic tool (4), • Diameter and / or length of the ferromagnetic tool (4), • Temperature of the ferromagnetic tool (4). [11] Method according to one of claims 7 to 10, wherein • when the device (1) is arranged stationary, the ferromagnetic tool (4) moves relatively in a spatial direction (x, y, z) during the approach process and / or the measuring process and rotates around its own longitudinal axis, or • when the ferromagnetic tool (4) is arranged stationary, the device (1) is moved relatively in a spatial direction (x, y, z) and / or on a trajectory curve around the ferromagnetic tool (4) during the approach process and / or the measuring process, wherein the ferromagnetic tool (4) rotates about its own longitudinal axis. [12] Method according to one of claims 7 to 11, wherein the evaluation comprises the following steps: • Retrieving or calculating a target curve of at least one target size of the ferromagnetic tool (4), • Comparing the retrieved or calculated target curve with a measured actual curve of at least one actual size of the ferromagnetic tool (4), • If a deviation is detected: - Determination of the degree of deviation and - if a defined threshold value is exceeded: carrying out a depth analysis of the measurement and / or aborting the measurement and / or aborting the workpiece processing. [13] Method according to claim 12, wherein the threshold value additionally takes into account at least one of the variables from claim 10. [14] Method according to one of the preceding claims 7 to 13, wherein the data in the depth analysis are evaluated with computer support with regard to wear forms, wear parameters, position and condition of the cutting edges, position and condition of the chip spaces, the material composition, the chip adhesion and / or an intensity distribution of the ferromagnetic tool (4).

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