Device and method for contactless fracture monitoring and / or wear monitoring

Abstract

To provide a device and method for contactless fracture monitoring and, additionally or alternatively, for contactless wear monitoring in a machine tool.SOLUTION: The device comprises a sensor and at least one magnetic field generator. Using the sensor, the device measures local changes in the magnetic flux density at a defined measuring distance and evaluates a measurement signal via an electronic evaluation unit. The sensor is configured such that the longest dimension of the sensor in one spatial direction is at most 500 μm or less, where the sensor (2) is capable of measuring a magnetic field in at least one spatial direction.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a device and a method for contactless detection of signs of breakage and signs of wear in ferromagnetic tools as claimed in independent claim 1 or independent claim 7. [Background technology]

[0002] When a machine tool is equipped with a tool for machining a workpiece, and the workpiece is machined with respect to its geometric shape, unexpected and unpredictable damage can occur to the tool in the form of a complete break or a small chip of the cutting edge. For example, if the tool breaks completely, this not only causes a sudden load on the machine tool, but also often results in damage to the workpiece. In addition, if such a complete break of the tool remains unnoticed, it usually leads to an inappropriate machining of the workpiece in the subsequent steps of the corresponding machine tool, and thus to an undesirable high scrap rate. Signs of wear in the form of small defects or breaks can also have a negative effect on the processing of the workpiece.

[0003] Therefore, a device for early detection of signs of breakage and signs of wear is one of the most important factors in preventing damage to machine tools and improving their reliability during machining.

[0004] From DE 3608572 A a method is known for monitoring breakage and / or wear of tools, in which the change in position of two adjacent machine parts equipped with weak magnets, at least one of which is subjected to forces by the machining process, is continuously inductively measured and monitored. The deformation of the tool, the tool support or the tool base holder is used as a measure of tool wear, since the forces on the tool increase with increasing wear.

[0005] The disadvantage of this method is that the monitoring of signs of tool breakage and wear by indirect measurement methods is relatively inaccurate, since only larger breaks in the tool can be detected. It is not possible to monitor the local cutting edge geometry with this method. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] German Patent Application Publication No. 3608572 Summary of the Invention [Problem to be solved by the invention]

[0007] The object of the present invention is to provide an apparatus and a method by which ferromagnetic tools can be checked for damage and / or wear reliably and contactlessly, which is insensitive to contamination, is inexpensive to manufacture and at the same time achieves a relatively high measurement accuracy. [Means for solving the problem]

[0008] According to the invention, this object is achieved by the features of claims 1 and 7. Advantageous embodiments and further developments are set out in the respective dependent claims.

[0009] The device according to the invention is suitable for contactless damage monitoring, additionally or alternatively for wear monitoring of ferromagnetic tools in machine tools. The device comprises a sensor and at least one magnetic field generator, which may be configured, for example, as a permanent magnet. In this case, the device measures the local change in magnetic flux density at a defined measuring distance by means of the sensor and electronically evaluates the measurement signal by means of an evaluation unit. The sensor is configured such that the longest dimension of the sensing surface in one spatial direction is at most 500 μm, whereby 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 may be arranged along a straight line extending parallel or perpendicular to the longitudinal axis of the ferromagnetic tool.

[0011] In a further embodiment, the sensor and at least one magnetic field generator are disposed within a housing of the apparatus, wherein the at least one magnetic field generator is disposed within the housing such that a bias magnetic field of the magnetic field generator passes through the at least one sensor and is applied within the ferromagnetic tool.

[0012] Advantageously, the sensor 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 can detect at least one further physical quantity in addition to measuring the magnetic flux density.

[0014] The physical quantities may be state variables, for example pressure, temperature, etc. For example, they may be temperature values ​​measured within the magnetic field sensitivity range of a sensor, such temperature values ​​being particularly relevant for ferromagnetic tools.

[0015] Advantageously, the device is configured for decontaminating the device and additionally or alternatively ferromagnetic tools using compressed air and additionally or alternatively using an alternating magnetic field.

[0016] According to a further aspect, the invention comprises a method for contactless damage and / or wear monitoring of a ferromagnetic tool in a machine tool by means of an apparatus comprising a point-like measuring sensor and at least one magnetic field generator. The method comprises the steps of: - the step of bringing the ferromagnetic tool and the device into close relative proximity; applying a bias magnetic field to the ferromagnetic tool; Measuring, in at least one spatial direction, the magnetic flux density of the magnetic field modulated by the ferromagnetic tool; - correcting and evaluating the measurement signals which determine the geometry of the ferromagnetic tool, Includes.

[0017] In particular, due to the special point-like configuration of the sensor a high resolution of the measurement result can be achieved.

[0018] In a further embodiment, signal correction and signal evaluation are performed electronically within the device.

[0019] Advantageously, the result of the signal evaluation is transmitted to a storage unit after completion and additionally or alternatively to an output unit.

[0020] According to an advantageous further development, the following values ​​are provided: - spatial position of ferromagnetic tools, - Measuring distance to the sensor of ferromagnetic tools, Angular position of ferromagnetic tools, - The rotation speed of ferromagnetic tools, the diameter of the ferromagnetic tool and additionally or alternatively the length of the ferromagnetic tool, -Temperature of ferromagnetic tools, At least one of the following is additionally determined:

[0021] Advantageously, in the case of a stationary arrangement of the device, a relative movement of the ferromagnetic tool in at least one spatial direction takes place during the approaching process and additionally or alternatively during the measuring process. In this case, the ferromagnetic tool can rotate relatively around its own longitudinal axis. In the case of a stationary arrangement of the device, during the approaching process and additionally or alternatively during the measuring process, the device can move relatively around the ferromagnetic tool in at least one spatial direction, with the ferromagnetic tool rotating around its own longitudinal axis. Alternatively or additionally, the movement of the device can also take place on a track around the ferromagnetic tool, with the ferromagnetic tool rotating around its own longitudinal axis.

[0022] In a further embodiment, the evaluation comprises the steps of: - searching for or calculating a target curve of at least one target value of a ferromagnetic tool, - comparing the retrieved or calculated target curve with a measured actual curve of at least one actual value of the ferromagnetic tool, If a deviation is detected, - determining the degree of deviation, and - performing a detailed analysis of the measurement and / or stopping the measurement and / or stopping the processing of the workpiece if a defined threshold is exceeded; Includes.

[0023] Advantageously, the threshold value is the following value: - spatial position of ferromagnetic tools, - Measuring distance to the sensor of ferromagnetic tools, Angular position of ferromagnetic tools, - The rotation speed of ferromagnetic tools, the diameter of the ferromagnetic tool and additionally or alternatively the length of the ferromagnetic tool, -Temperature of ferromagnetic tools, At least one of the following is further considered:

[0024] According to an advantageous further development, the data of the measurements are evaluated in a detailed analysis of the wear form, the wear parameters, the position and state of the cutting edge, the position and state of the chip space, the material composition, the chip adhesion and additionally or alternatively the strength distribution of the ferromagnetic tool.

[0025] The invention is explained in more detail below with respect to further features and advantages on the basis of a description of an embodiment and with reference to the attached schematic drawings. [Brief description of the drawings]

[0026] [Figure 1] 1 shows a highly schematic diagram of an embodiment of a device according to the invention; [Diagram 2] 1 shows a highly schematic diagram of the measurement principle of a device according to the invention; [Diagram 3] 2 shows two measurements of a ferromagnetic tool with exemplary first and second actual curves. [Figure 4] 4 shows a measurement of a ferromagnetic tool having an exemplary third actual curve. [Diagram 5] A schematic diagram of the method according to the invention is shown as a flow chart. [Figure 6] FIG. 6 shows a schematic diagram of the sub-steps included in the “Evaluate” step of FIG. 5 . DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Some particular embodiments of the invention are explained in more detail below with reference to the drawings.

[0028] The device 1 according to the invention is suitable for use in the working area of ​​a machine tool, in which a ferromagnetic tool 4 is to be checked for signs of 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.

[0029] 1 shows a device according to the invention and a ferromagnetic tool 4, which comprises a housing 5, a carrier element 2.1 with a sensor 2 and a magnetic field generator 3. In the embodiment envisaged, 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 far end of the device 1, which is located in the immediate vicinity of the ferromagnetic tool 4, whereby a defined minimum measuring distance d in the form of an air gap exists between the ferromagnetic tool 4 and the device 1.

[0030] 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 perpendicular 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, with the ferromagnetic tool 4, the sensor 2 and the at least one magnetic field generator 3 remaining positioned on a straight line.

[0031] Thus, the line on which the at least one magnetic field generator 3 and the sensor 2 are located may extend 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 are mounted on a line extending parallel to the longitudinal axis of the ferromagnetic tool 4. In this case, the sensor 2 should ideally be positioned closer to the tool support of the ferromagnetic tool 4 than the at least one magnetic field generator 3.

[0032] The measuring distance d defines the distance between the surface of the device 1 and the cutting diameter of the maximum perimeter of the cross section of the ferromagnetic tool 4. In this case, the measuring distance d is selected such that a small air gap, typically between 200 μm and 300 μm, remains between the device 1 and the ferromagnetic tool 4. The measuring distance d may therefore be constant during each test procedure or, alternatively, may vary depending, for example, on the diameter of the ferromagnetic tool 4 or on the current temperature of the ferromagnetic tool 4 or on its ambient temperature.

[0033] The ferromagnetic tool 4 is understood to mean a tool for manufacturing a workpiece, where the machine tool predetermines or influences the relative movement between the device 1 and the ferromagnetic tool 4 in the working space of the machine tool. In particular, this includes single- and multi-edged tools for machining processes involving cutting materials with ferromagnetic properties. In addition to this, drills, milling tools, reamers, broaches, cutting tools or inserts made of tool steel or hard metal are included, for example.

[0034] For example, a ferromagnetic tool 4 can be moved through the machine tool in all three spatial directions x, y, z and can be rotated in a defined manner about its longitudinal axis (φ direction).

[0035] The bias magnetic field of at least one magnetic field generator 3 is applied to 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 with respect to a local magnetic flux density that depends on the local cross-sectional geometry of the ferromagnetic tool 4. For example, this leads to a concentration of magnetic field lines at the cutting edge, thus increasing the magnetic flux density. However, in the chip space of the ferromagnetic tool 4, a relatively low magnetic flux density is present, which allows a distinction between the cutting edge and the chip space.

[0036] The sensor 2 can measure the magnetic flux density in at least one spatial direction x, y, z at a defined measuring distance d. In this case, the measurement is performed point-wise, the resolution of the measurement being provided by the sensing surface of the sensor 2. The sensing surface preferably has a dimension in the spatial direction x, y, z with its longest extension of less than 500 μm, in particular less than 200 μm, preferably less than 100 μm. The dimensions of the sensing surface of the sensor 2 determine the spatial resolution of the sensor 2. The bandwidth of the sensor 2 represents the (analog) measuring frequency and is preferably at least 10 kHz.

[0037] The device 1 measures the magnetic flux density with exactly one sensor in the three spatial directions x, y, z. For this purpose, the sensor 2 can be equipped with, for example, three sensitive surfaces, whereby the sensitive surfaces may consist of three Hall elements arranged perpendicular to one another, which enable the measurement of the magnetic flux density in the three spatial directions x, y, z, or may additionally or alternatively be equipped with a TMR element. However, it is also possible to measure the magnetic flux density in only one or two spatial directions x, y, z. In this case, the selection of the spatial direction or directions x, y, z depends on the situation, i.e., for example, on the relative position of the device 1 with respect to the ferromagnetic tool 4, whereby the spatial direction or directions x, y, z that provide the most reliable measurement signal or signals are always utilized for the measurement or evaluation.

[0038] The Hall element is a Hall effect element, which can be realized for example as a semiconductor component, and in particular is capable of measuring at least one Hall voltage, from which at least one local directional component of a magnetic field can be inferred.

[0039] A TMR element is an element that uses the tunnel magnetoresistance effect to determine at least one local directional component of a magnetic field. The TMR element can also be realized as part of a semiconductor component.

[0040] Advantageously, the device 1 can detect further physical quantities in addition to the magnetic flux density. This physical quantity can in particular be a temperature value. For this purpose, a temperature measuring element can be provided inside the sensor 2 or, alternatively, on the carrier element 2.1. In this case, the temperature can be measured in the area of ​​the sensor 2, for example by a thermistor, or inside the electric field-sensing area of ​​the sensor 2, for example by a microbolometer element or a pyrometer.

[0041] During the approaching process, the ferromagnetic tool 4 is moved to the end of the device 1 where the sensor 2 is located. A measurement of the magnetic flux density of the ferromagnetic tool 4 located at a measuring distance d is then carried out by the sensor 2. The ferromagnetic tool 4 can, for example, be moved in the z direction during the measuring process. Additionally or alternatively, the ferromagnetic tool 4 can also be rotated about its longitudinal axis.

[0042] The magnetic field lines 3.1 of the magnetic field generator 3 are applied to the ferromagnetic tool 4 as soon as the ferromagnetic tool 4 is located in the bias field of the magnetic field generator 3. The applied magnetic field lines 3.1 are then aligned in a defined manner depending on the local cross-sectional shape of the ferromagnetic tool 4, i.e. with a locally characteristic magnetic flux density. By means of the sensor 2, this modulated magnetic field is measured and evaluated with respect to at least one of the three spatial directions x, y, z.

[0043] The magnetic field generator 3 can be formed as a permanent magnet or an electromagnet, whereby the device 1 may comprise several magnetic field generators 3. If several magnetic field generators 3 are provided, these may be identical or different, i.e. the device 1 may comprise, for example, permanent magnets and electromagnets as magnetic field generators 3.

[0044] Such electromagnets comprise an electromagnetic coil with a defined number of turns that forms a magnetic field when a current flows through it. Typically, the electromagnetic coil further comprises at least one (open) core made of a magnetically soft material (e.g. iron) through which the magnetic field is guided and amplified. When a direct current flows through the electromagnetic coil, the magnetized shavings can be easily removed from the device if necessary by interrupting the power supply to the electromagnet and possibly removing the adhering shavings and metal dust manually or automatically (e.g. using compressed air, etc.). Alternatively, an alternating current may flow through the electromagnetic coil. In this case, manual or automated cleaning of the device 1 and additionally or alternatively of the ferromagnetic tool 4 is not necessarily required, since the periodic and repetitive phase changes neutralize on average the magnetization of the shavings and metal dust. To achieve particularly good cleaning results, a combination of compressed air cleaning and cleaning using an alternating magnetic field can also be envisaged.

[0045] According to a second embodiment, not shown in detail in the figures, the device 1 may comprise two magnetic field generators 3, one of which serves to generate a bias magnetic field and the second one serves to demagnetize the device 1 and additionally or alternatively the ferromagnetic tool 4. In this case, the second magnetic field generator can be arranged within the device 1, for example in the form of an electromagnet, or outside the device 1, for example in the form of an electromagnet with gradually decaying magnetization.

[0046] When the device 1 is arranged in a fixed manner in the working space of the machine tool, the relative movement of the ferromagnetic tool 4 takes place in at least one spatial direction x, y, z during the approaching process and additionally or alternatively during the measuring process. In this case, the ferromagnetic tool 4 can be relatively rotated, in particular around its own longitudinal axis. When the device 1 is arranged in a fixed manner in the working space of the machine tool, the device 1 can be relatively moved in at least one spatial direction x, y, z around the ferromagnetic tool 4 during the approaching process and additionally or alternatively during the measuring process, in which case the ferromagnetic tool 4 rotates, in particular around its own longitudinal axis. Alternatively or additionally, this can take place on a trajectory around the ferromagnetic tool 4, in which case the ferromagnetic tool 4 rotates, in particular around its own longitudinal axis. In this case, the device 1 can be attached, for example, to a robot arm of an industrial robot as an end effector, which robot arm can move with several degrees of freedom.

[0047] In this case, the device 1 may be fixedly coupled to a machine tool (e.g. the milling table of a milling machine) and the ferromagnetic tool 4 can be brought close to the fixed device 1 by a linear movement, whereby the ferromagnetic tool 4 can, if necessary, rotate simultaneously with a defined number of revolutions.

[0048] Alternatively, the ferromagnetic tool 4 may be fixedly coupled to the headstock of a machine tool, for example a lathe, and the device 1 can be brought close to the ferromagnetic tool 4 by linear movement, for example on a carriage.

[0049] As shown in Fig. 1, the magnetic field lines 3.1 of the permanent magnet 3 are applied to the ferromagnetic tool 4 through the sensor 2 according to the first embodiment. The influence of the bias field of the permanent magnet 3 is compensated for in the course of the signal evaluation or signal correction, so that when generating the actual course of the magnetic flux density, only the modulated magnetic field of the ferromagnetic tool 4 is taken into account.

[0050] 2 shows in a very schematic diagram the process of applying the magnetic field of the permanent magnets 3 of the device 1 to a ferromagnetic tool 4 rotating about its longitudinal axis. In this case, the application of the bias magnetic field to the ferromagnetic tool 4 strongly depends on the rotation angle φ or the local position of the cutting edge and the chip space in the respective infinitesimal longitudinal or transverse cross section of the ferromagnetic tool 4.

[0051] In the following description of Figures 2a to 2d, for the cross-section of the ferromagnetic tool 4 considered, z is constant and φ varies clockwise.

[0052] In this case, Fig. 2a shows the 1 3 shows a cross-section of a ferromagnetic tool 4 at , where the profile of the ferromagnetic tool 4 is aligned such that the magnetic field lines 3.1 of the permanent magnet 3 couple approximately parallel to the x-axis and apply them through the sensor 2 to the ferromagnetic tool 4.

[0053] Time t in Figure 2b 2 In the figure, the angular position of the illustrated cross-section of the ferromagnetic tool 4 of Fig. 2a has changed by an angle of several degrees, which results in a characteristic deflection of the magnetic field lines 3.1 of the permanent magnet 3. These are now applied more strongly to the part of the cross-section of the ferromagnetic tool 4 which has the smallest measuring distance d, which results in an increase in the magnetic flux density there.

[0054] This effect lasts until time t 3 This is even more noticeable in Fig. 2c which shows the application of the magnetic field lines 3.1 at d = 0. At this point, the ferromagnetic tool 4 has again moved further by an angle of a few degrees and there is now an even smaller sub-area of ​​the ferromagnetic tool 4 with the smallest measurement distance d, which results in an even higher magnetic flux density in this sub-area.

[0055] Finally, the cutting edges of the ferromagnetic tool 4 in FIG. 2d are spaced apart by a maximum measuring distance d such that the tip space is located opposite the sensor 2. The magnetic field lines 3.1 of the permanent magnet 3, when the ferromagnetic tool 4 is in such an angular position, spread out in a unique sector shape and apply it to the ferromagnetic tool 4 over a comparatively large partial area.

[0056] The changes in the magnetic field, in particular the changes 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 measured values ​​obtained can then be used to create an actual course. If necessary, the actual course can be adjusted by a signal correction integrated on the carrier element 2.1 or alternatively integrated downstream in the device 1, so that only the modulated magnetic field of the ferromagnetic tool 4 is examined in the subsequent signal evaluation.

[0057] FIG. 3 shows two exemplary real courses in the form of two function graphs, generated during the measurement process of a ferromagnetic solid carbide drill 4 with a diameter of 3.4 mm. The ferromagnetic drill 4 was measured at a measurement distance d=200 μm in both the axial direction z and the circumferential direction φ. The plotted curves show the magnetic flux density B x Measurements of are shown.

[0058] Figure 3aB x The -z graph shows a measurement in the z direction along the drill 4 at a fixed angular position φ of the drill 4. In the depicted function graph, the area of ​​the cutting edge of the drill 4 stands out clearly in the form of four peaks or extrema. If a part of the drill 4 were to break, for example at dashed line A, this would result in a signal change and no peak of the first cutting edge seen from below at z≈40 mm would result. The dashed line L shows the course of the measurement signal which should be expected in the case of such a tool breakage. In particular, the depicted function graph allows early detection of geometrical dimensions or total tool failure.

[0059] Alternatively, the cutting edge of the drill 4 can be measured in the circumferential direction φ, as seen in the curve shown in FIG. x From the figure, the two cutting edges of the drill 4 stand out clearly in the form of two peaks at certain measurement points relative to z. Using the function graphs shown, the number of cutting edges, the geometric dimensions or defects or breakages of the tool to be measured can be determined particularly well.

[0060] In particular, another diagram is the heat map H (see FIG. 4) which combines the information of the functional graphs of FIG. 3a and FIG. 3b. For example, in that diagram, the measured magnetic flux density B x is described as a function of the circumferential direction φ and the axial direction z of the drill 4. For example, such an evaluation is suitable for detailed analysis of ferromagnetic tools with regard to the geometric dimensions, the number of cutting edges, the material of the drill 4 or the cutting material, early detection of total tool failure, especially the detection of defects or breakage.

[0061] In addition to the described embodiment of the device according to the invention, there are further design possibilities within the scope of the invention.

[0062] It is also possible for the device 1 according to the invention to move 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 is conceivable when measuring the cutting edge of an insert in the working area of ​​a lathe. For example, the device 1 can be located on a carriage and approach the insert mounted in the tool holder. In this case, the measurement signal can also be evaluated using the characteristic curve of the magnetic flux density. However, in this case, the mere presence of extreme values ​​in the actual course would already indicate wear.

[0063] A method for non-contact damage monitoring and additionally or alternatively wear monitoring is shown in Figure 5 as a schematic flow diagram 50. A program sequence for inspecting the ferromagnetic tool 4 can be started or initialized (step 51) by an operator or automatically within a certain time interval via the control system of the machine tool.

[0064] This is followed by a relative approach 52 between the ferromagnetic tool 4 and the device 1 until the measuring distance d is reached. For example, by means of a machine tool, the ferromagnetic tool 4 is moved within the working area of ​​the machine tool to the device 1 which is fixed within the working area. The ferromagnetic tool 4 can be relatively rotated about its longitudinal axis in a defined manner during the entire process.

[0065] In a subsequent step 53, a bias magnetic field, caused by at least one magnetic field generator 3 of the device 1, is applied.

[0066] In a subsequent step 54, the magnetic field modulated by the ferromagnetic tool 4 is measured by the sensor 2 in terms of magnetic flux density, whereby, if necessary, further physical quantities (for example at least one temperature value) can also be determined. This data then forms a database for the actual progression.

[0067] This is followed by an evaluation 55 of the predetermined measurement result from step 54, with signal correction also taking place within this step, in which case the evaluation 55 may be automated and computer-assisted (e.g. by means of an artificial neural network), performed manually by an operator or by a combination of both processing methods.

[0068] In the penultimate step 56, the evaluation result or evaluation results can be transmitted to an output unit 68, 68'. In the output unit 68, 68', the evaluation result is stored in a storage unit and can additionally or alternatively be transmitted to a user. For example, such a transmission can be performed visually via a screen of the machine tool, acoustically via an audio output unit, etc. Finally, the program sequence 50 ends in step 57.

[0069] It should be noted here that during the program sequence 50 the ferromagnetic tool 4 has to remain at the measuring distance d (possibly rotating relatively about its longitudinal axis) only during step 54 ("Measurement"). During the subsequent steps 55-57, further program sequences can be implemented by the machine tool control in parallel to the running program sequence 50, i.e. for example further machining of the workpiece with the ferromagnetic tool 4 can be performed.

[0070] FIG. 6 shows a schematic flow diagram 60 of the sub-steps of the method step evaluation 55 shown in FIG.

[0071] Submodule Evaluation 61 is a subelement of process step Evaluation 55. As soon as submodule 61 is called, substep 62 is executed, which retrieves target state information of the ferromagnetic tool 4 to be measured from the database and subsequently derives a target progression therefrom. In this case, this target state information is already available as a completed target progression or can still be calculated or generated. For example, if target state information from a previous measurement is not available, the calculation of the target state information can be performed based on corresponding unused ferromagnetic tool state information and the usage time of the ferromagnetic tool 4 stored in the storage unit.

[0072] In the next sub-step 63, the actual course of the measurement data determined in step 54 is compared with the target course retrieved or calculated in sub-step 62, i.e. the degree of deviation of the two courses is determined. This can be done, for example, for each, several or all of the actual and target course values. Alternatively, a suitable reference value can be determined as the degree of deviation. This reference value can, for example, comprise the subtraction of the integral of the actual course from the target course. In addition, the target course and the actual course can be standardized in particular with respect to another physical quantity, for example with respect to the local temperature distribution in the ferromagnetic tool 4. It is also conceivable that the determination of the deviation with respect to both courses is carried out only in sections, for example for sections of the ferromagnetic tool 4 that are particularly susceptible to wear or tool breakage.

[0073] 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 absence of deviation is transmitted to the output unit 68. Such minimal deviations may occur, for example, within the measurement accuracy of the sensor 2 for a new, unused ferromagnetic tool 4.

[0074] However, if the degree of deviation is equal to or greater than a threshold value (Yes - path 65), a detailed analysis is performed (substep 67) or, alternatively, the measurement or processing of the workpiece is stopped. In such a detailed analysis, the measurement data, the actual course, the target course and, additionally or alternatively, the deviation of the target course and the actual course are evaluated in more detail. In this case, in particular, the detailed analysis comprises an 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 space, the material composition, chip adhesion or contamination and, additionally or alternatively, further strength distribution of the ferromagnetic tool 4. Such a detailed analysis may be performed algorithmically, in particular by machine learning methods, or manually by an operator. A combination of both methods is also conceivable. Finally, one or more results of substep 67 are transmitted to an output unit 68' (for example in the form of a heat map H) and the submodule 61 is finally terminated (substep 69).

[0075] The output unit 68, 68' may be the display of the machine tool, in which case the results are presented graphically to allow the operator to intuitively understand the current state of the ferromagnetic tool 4 in use.

[0076] If wear or breakage of the ferromagnetic tool 4 is detected by the device 1, further machining of the workpiece can, for example, be stopped and the operator can be informed of the event in the form of a visual output and additionally or alternatively an audio output.

[0077] Furthermore, a storage unit may be provided for storing historical data of the evaluations or detailed analyses in a non-volatile memory. In case of a machine tool with a tool turret, all evaluations or detailed analyses of the device 1 for all ferromagnetic tools in the tool turret can be accessed. Furthermore, the display of the results via the output unit 68, 68' is not limited to the ferromagnetic tool 4 in use.

Claims

1. A device (1) for contactless damage and / or wear monitoring of a ferromagnetic tool (4) in a machine tool, comprising a sensor (2) and at least one magnetic field generator (3), said device (1) being capable of measuring the local variation of the magnetic flux density (B) at a measuring distance (d) by means of a sensor (2) and evaluating it by means of an electronic evaluation unit, The sensor (2) The longest dimension of the sensor in one spatial direction (x, y, z) is at most 500 μm or less, and the magnetic field can be measured in at least one spatial direction (x, y, z) by said sensor (2); The apparatus (1) is configured as follows.

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

3. 3. The apparatus (1) according to claim 1 or 2, further comprising a housing (5), the sensor (2) and at least one magnetic field generator (3) being arranged within the housing (5) such that a bias magnetic field of the magnetic field generator can pass through the sensor (2) and be applied within a ferromagnetic tool (4).

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

6. The device (1) according to any one of claims 1 to 5, wherein the device (1) is configured for decontaminating the device (1) and / or the ferromagnetic tool (4) using compressed air and / or an alternating magnetic field.

7. 1. A method for contactless damage and / or wear monitoring of ferromagnetic tools (4) in machine tools by means of a device (1) comprising a point-wise measuring sensor (2) and at least one magnetic field generator (3), comprising: The method comprises the steps of: - bringing the ferromagnetic tool (4) and the device (1) into relative proximity; - applying a bias magnetic field to the ferromagnetic tool (4); - measuring, in at least one spatial direction (x, y, z), the magnetic flux density of the magnetic field modulated by said ferromagnetic tool (4); a signal correction step and a signal evaluation step for determining the geometry of the ferromagnetic tool (4); A method comprising:

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 following values: the spatial position of the ferromagnetic tool (4), the distance (d) of the ferromagnetic tool (4) to the sensor (2), the angular position (φ) of the ferromagnetic tool (4), the rotational speed of the ferromagnetic tool (4), the diameter and / or length of said ferromagnetic tool (4), the temperature of the ferromagnetic tool (4), At least one of the following is additionally determined: The method according to any one of claims 7 to 9.

11. In the case of a stationary arrangement of the device (1), the ferromagnetic tool (4) moves relatively in one spatial direction (x, y, z) and rotates about its own longitudinal axis during the approaching and / or measuring process; or if the ferromagnetic tool (4) is arranged stationary, the device (1) moves relatively in one spatial direction (x, y, z) and / or in a trajectory around the ferromagnetic tool (4) during the proximity process and / or during the measurement process, the ferromagnetic tool (4) rotating around its own longitudinal axis, The method according to any one of claims 7 to 10.

12. The evaluation comprises the steps of: - searching or calculating a target curve of at least one target value of the ferromagnetic tool (4), a step of comparing the retrieved or calculated target curve with a measured actual curve of at least one actual value of the ferromagnetic tool (4), If a deviation is detected, - determining the degree of deviation, and - performing a detailed analysis of the measurement and / or stopping the measurement and / or stopping the processing of the workpiece if a defined threshold is exceeded; Including, 12. The method according to any one of claims 7 to 11.

13. The threshold value further takes into account at least one of the values ​​according to claim 10. The method of claim 12.

14. In said detailed analysis, the data is evaluated with the aid of a computer with respect to wear morphology, wear parameters, position and condition of the cutting edge, position and condition of the chip space, material composition, chip adhesion, and / or strength distribution of the ferromagnetic tool (4). The method according to any one of claims 7 to 13.

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