Machine tool unit with testing of bearing loads of the spindle during operation

Abstract

The invention relates to a machine tool unit (1) comprising a stator unit (2) and a rotor unit (3) having a material measure (5) for detecting the rotational movement and / or displacement and / or deformation, and comprising a test device (12) for testing bearing loads, which is used to measure the working and process force of an action of force or to determine the displacement, deformation and movement during operation. For more precise machining, an axial sensor (6) and a sensor unit (7) are provided for determining the deformation and / or displacement on the basis of the position of the material measure (5) in the axial or radial direction and the phase relationship between the position of the rotor unit (3) or spindle shaft (4) or the phase relationship given by the force ratio of the acting forces, wherein the axial sensor (6) is arranged in such a way that it measures the deformation and / or displacement on the basis of the position of the material measure (6) in the axial direction.

Description

[0001] Patent application Applicant: Franz Kessler GmbH Status: 13.12.2025 Our reference: K 9438-PC - 1 -

[0002] Machine tool unit with testing of spindle bearing loads during operation

[0003] The invention relates to a motor-driven machine tool unit according to the preamble of claim 1 for testing bearing loads of the spindle during operation and for measuring working and process forces as well as for determining displacements, deformations or the like.

[0004] For example, EP 3 581 328 B1 discloses a machine tool unit in which runout errors are detected by sensors by recording and evaluating a time- or position-related series of distance values ​​from a sensor head mounted on the stator to the end face of the rotating spindle head. Furthermore, DE 10 2020 003 055 A1 discloses a method for determining the static and dynamic load of a drive shaft in the radial and axial directions, respectively.

[0005] The object of the invention is to provide a machine tool unit for its operation which allows for more precise machining and a better planned machining process.

[0006] Starting from a machine tool unit of the type mentioned above, the problem is solved by the characterizing features of claim 1.

[0007] The measures mentioned in the dependent claims enable advantageous embodiments and further developments of the invention. Patent application filed by: Franz Kessler GmbH, dated: December 13, 2025. Our reference: K 9438-PC - 2 -

[0008] The motor-driven machine tool unit according to the invention comprises a stator unit and a rotor unit rotatable about a rotary axis, the rotor unit having a spindle shaft. The spindle shaft, in turn, includes a measuring element with a measuring surface for detecting the rotational movement and / or the displacement and / or deformation and / or the movement of the measuring surface of the rotor unit. In one embodiment of the invention, this measuring element can, for example, be designed as a separate measuring ring mounted on the spindle shaft. This design has the advantage that the measuring ring can be made of a different material or have different surface properties, independent of the properties of the spindle shaft. However, the spindle shaft itself can also form this measuring element, for example, by providing or forming its own measuring surface on the spindle shaft.For example, a suitable, designated surface can be machined to be as flat or even as possible, thus making it suitable as a reference surface for measurements. The measuring surface can rotate together with the rotor unit because it is also attached to the spindle shaft or is part of the spindle shaft.

[0009] If, for example, a feed drive in the form of a ball screw is considered as another possibility for machine-induced displacement, a systematic displacement of the shaft relative to the actual feed can occur. Due to friction in the axis guide elements and the machining force, a certain degree of torsion is introduced into the shaft between the motor and the ball screw nut via the torque. This displacement or phase shift can also be detected by sensors according to the invention. Patent application. Applicant: Franz Kessler GmbH. Date: December 13, 2025. Our reference: K 9438-PC - 3 -

[0010] The forces acting between the tool and the workpiece also stress, displace, or deform the spindle shaft. Additional vibrations can occur. Rapid localized heating can result. Bearing problems often arise, which, unless the machine tool unit itself is damaged, can lead to inaccurate machining. Since the bearings should not be overloaded, it is necessary to enable testing during operation so that machining processes can be adjusted, regulated, optimized, or, if necessary, interrupted. Indications of when maintenance or servicing will be necessary can also improve manufacturing quality. However, it is often not possible to directly measure certain parameters during operation, such as the stiffness of the tool, the system, or the forces acting on the tool, etc.Furthermore, a certain temperature difference will generally be observed between the housing and the shaft. In practice, however, the temperature will only be measured at discrete points, usually only at one point. Therefore, according to the invention, it is advantageous to be able to recognize technical relationships from the measured quantities and to draw conclusions about such quantities that are not directly measured.

[0011] A physical dimension is used as a measuring aid. In this case, it rotates with the spindle shaft and enables the measurement of certain parameters related to the spindle shaft, such as any displacements, vibrations, or the like; in this way, for example, an imbalance can be detected and measured. If, for example, an external force acts on the spindle shaft, such as when a tool is clamped to the spindle shaft and used to machine a workpiece, the spindle shaft can deform or shift. A flat surface, for example, perpendicular to the axis of rotation of the spindle shaft, can tilt. (See the position of the patent application. Applicant: Franz Kessler GmbH. Date: December 13, 2025. Our reference: K 9438-PC - 4 -)

[0012] When a measuring surface rotates at a fixed point, a vibration will be observed at that point when examining the surface. This runout error, or the associated vibration, can be analyzed. It is also conceivable to determine a force from this, which requires knowledge of the system's stiffness. Further deformation or displacement can also be observed on the lateral surface of the shaft or the measuring element and detected by sensors.

[0013] For example, the rotor unit includes a spindle head with a tool holding unit and a tool clamping device that is adjustable in the longitudinal direction of the axis of rotation and can be subjected to a clamping force for clamping and fixing a detachably fixable tool in order to enable a simple and quick tool change.

[0014] Furthermore, in one application, the spindle shaft may be clamped, although a force will still act on the shaft during machining. In this case, displacement or deformation can also occur, even if it is a static case, i.e., even if the shaft is not rotating. At the very least, movement of the measuring surface due to the force can often be observed.

[0015] A wide range of information can be obtained from measuring displacement / deformation during operation or from measuring working / process forces, e.g., how much stress a tool is subjected to during operation, how the bearings of the rotor unit must be designed, which speed should be used for specific machining processes, what the feed rate should be, whether the tool is subject to patent application. Applicant: Franz Kessler GmbH. Status: 13.12.2025. Our reference: K 9438-PC - 5 -

[0016] damage suffered, when the machine tool unit needs to be serviced or repaired, etc.

[0017] According to the invention, a testing device is provided with which the bearing loads of the spindle can be determined and which serves to measure the working and process forces acting on at least a part of the rotor unit and / or the spindle shaft and / or to determine the displacement, deformation, and movement of the measuring surface of the rotor unit during operation. In the event of an irregularity, e.g., due to the application of a force, a change such as a vibration can generally be detected.

[0018] The sensor outputs can be converted back into a response signal. The change, here for example an oscillation, can generally be represented by a term of the form s = A sin( <p) + B oder s = A cos(c - <p) + B beschrieben werden.

[0019] Where: s are the sensor readings (e.g., distance measurements), c is the sensor position as an angular position, and cp is the point of force application as an angular position.

[0020] B an offset in case of axial displacement (or deformation) A the axial or radial component of the deformation

[0021] As a rule, a system of equations with three unknowns must be solved. According to the invention, a specific number of sensors is therefore necessary to perform the corresponding evaluation. Depending on which measured variables are being sensor-acquired, a specific arrangement of the sensors is also required. For this purpose, for example, three series of measurements can be carried out in parallel, e.g., using three different or differently arranged sensors.

[0022] The test device can include different sensor combinations to provide the necessary sensor data for this evaluation:

[0023] According to the invention, an axial sensor is always provided, which measures distances in the axial direction caused by deformations or displacements, but also differences that can arise during rotational movements, for example, due to imbalances. The deformation and thus displacement of the shaft under the influence of an axial force can generally only be measured with an axial sensor. The measurement signal can be observed independently of the positioning of the force sensor.

[0024] With advantageous further training, a learning process can take place for the spindles to be examined, as explained later, using a machine learning process or artificial intelligence, in order to determine quantities such as the stiffness of the tool of the system or the spindle shaft in the system and / or the acting axial and / or radial forces from the measurement data of the sensors.

[0025] 1. Implementation variant for calculating quantities such as axial and radial forces

[0026] In an advantageous embodiment of the invention, the testing device is configured to convert the measured values ​​back to a response signal of the form s = A cos(cp) + B, where A is the radial displacement or radial deformation under the influence of a radial force, B is the axial displacement / deformation, and cp is the angle of force application. Patent application: Franz Kessler GmbH, Status: 13.12.2025, Our reference: K 9438-PC - 7 -

[0027] The force sensor position is determined, and the system of equations with the measured values ​​s and the respective angular positions c of each sensor must be solved. (In a system of equations, different angular positions ci, C2, etc., can be used for each individual sensor; each sensor has its own equation within the system.) A system of equations with three unknowns can be further determined by three series of measurements (e.g., of the respective sensors). Algorithmically, a distinction can be made between the axial component A and the radial component B. With the response signal restored, it is possible to convert the deformation into the acting forces in the axial and radial directions, i.e., their respective magnitude and direction. The measured values ​​s of the respective sensors are usually known from the measurement series, as are the angular positions c of the sensors, so that the measurement equation for each sensor is: s = A cos(c - cp) + B.

[0028] From the three equations resulting for each sensor (more than three sensors are also conceivable), the quantities A, B and cp can be calculated.

[0029] In a configuration with three axial sensors, we have measured values ​​s from the sensors and angular positions c of the sensors, i.e., three equations of the form s = A cos(c - cp) + B, with different measured values ​​s and different sensor positions c for each sensor. The remaining three unknowns can therefore be determined.

[0030] In one embodiment of the invention, the radial force can be calculated using the stiffness function, whereby the radial force can depend on various factors, including deformation based on a radial force, deformation based on an axial force, and the rotational speed. Patent application. Applicant: Franz Kessler GmbH. Date: December 13, 2025. Our reference: K 9438-PC - 8 -

[0031] Furthermore, the calculation of the axial force in one embodiment of the

[0032] The invention, using the stiffness function, also depends on various factors, including deformation based on a radial force, deformation based on an axial force, and rotational speed.

[0033] In one embodiment of the invention, in addition to a

[0034] An axial sensor can be used in conjunction with two radial sensors. In this case, with two sensors (the radial sensors), the axial component B is eliminated, so the equation s = A cos(c - tp) + B simplifies to:

[0035] S = Aradiai COS(C - (p) with the radial component or radial deformation Aradiai.

[0036] Starting from the two equations for the radial sensors, where the

[0037] If the axial component B can be set to 0, the quantities of the radial deformation Aradiai and tp can be obtained by solving accordingly.

[0038] The following still applies to the axial sensor:

[0039] S = Aaxial COS(C - (p) + B.

[0040] For example, the axial deformation Aaxiai (which e.g. results from bending of the

[0041] The deflection of the spindle shaft or the tilting of the dimensioning element) can be calculated using the radial deformation Aradiai. In one embodiment, this can be done, for example, based on a deflection curve model that simulates the bending of the spindle shaft or the tilting of the dimensioning element. (Applicant: Franz Kessler GmbH, Status: 13.12.2025, Our reference: K 9438-PC - 9 -)

[0042] The equation for the axial sensor can then be solved for B using the calculated quantity Aaxiai.

[0043] In one embodiment of the invention, the radial force can again be calculated using the stiffness function, wherein the radial force depends on various factors, including the deformation based on a radial force, the deformation based on an axial force and the rotational speed.

[0044] For example, the axial force can also be calculated using a stiffness function, which depends on various factors, including deformation based on radial force, deformation based on axial force, and rotational speed.

[0045] 2. Implementation variant for calculating quantities such as axial and radial forces

[0046] In this design variant, the starting point is the cross-section of the spindle shaft, or a cross-section through the spindle shaft and the dimensioned representation located therein, whereby the cross-section in the unloaded state runs perpendicular to the axis of rotation. This cross-section can be represented as a circular area, which accordingly has a center point. As a result of radial deflection or deformation, the spindle shaft bends slightly; the circular area in cross-section is viewed laterally. Patent application. Applicant: Franz Kessler GmbH. Status: December 13, 2025. Our reference: K 9438-PC - 10 -

[0047] (also in the radial direction). Its center point also shifts with it. If at least two radial sensors are arranged around this cross-section, they can measure their distance to the circumference at this point. With the radial deflection or deformation of the shaft and the associated displacement of the circle in cross-section, the center point of this circle also shifts. Assuming that the circular area considered in cross-section only shifts but does not fundamentally change its shape, the position of the circumference can be determined by measuring the distances in the radial direction using the radial sensors, and thus the center point or its displacement can be calculated.

[0048] The radial displacement of the center point yields the radial deformon Aradiai.

[0049] Here too, s = Aradiai cos(c - (p) applies for the measurement series of a radial sensor, from which the force application points (p) can be determined, since the measured values ​​s are known, the position of the radial sensor c is known and the radial component Aradiai is known.

[0050] In one embodiment, the axial component Aaxiai can be calculated based on a deflection curve model using the calculated radial component Aradiai.

[0051] The equation for the axial sensor s = Aaxiai cos(c - (p) + B can therefore be solved for B and B can be calculated.

[0052] In one embodiment of the invention, the radial force can again be calculated using the stiffness function, whereby the radial force depends on various factors. Patent application applicant: Franz Kessler GmbH, Status: 13.12.2025, Our reference: K 9438-PC - 11 -

[0053] The factors depend, among other things, on the deformation based on a radial force, the deformation based on an axial force, and the rotational speed.

[0054] For example, the axial force can also be calculated using a stiffness function, which depends on various factors, including deformation based on radial force, deformation based on axial force, and rotational speed.

[0055] Other design variants:

[0056] The axial sensor measures the distance to the scale. If the spindle shaft is tilted or otherwise deformed, or if, for example, an imbalance during rotation leads to forces that are associated with changing positions of the shaft over time, this also affects the position of the scale. The distance to the scale then changes, particularly over time. The axial sensor measures the distance component, or the change in distance, in the axial direction.

[0057] Preferably, the axial sensor provides at least one series of measurements which contributes to solving a system of equations of a motion superimposed on the rotational motion, in particular a superimposed oscillation.

[0058] Furthermore, a sensor unit is provided that can also measure deformation, displacement, or vibration based on the position of the scale. The phase relationship between the position of the rotor unit or spindle shaft and the corresponding sensor, or the phase relationship determined by the force ratio, can also be established. The sensor unit preferably provides at least two measurement series. [Applicant: Franz Kessler GmbH, Date: December 13, 2025, Our Reference: K 9438-PC - 12 -]

[0059] To solve a system of equations of a motion superimposed on a rotational motion, in particular a superimposed oscillation.

[0060] Various design options are conceivable, including which sensor combinations the sensor unit can have:

[0061] One possibility is to provide an additional axial and a radial sensor so that the deformation or displacement can be measured in all three spatial directions. Specifically, any two of the sensors can be oriented at a 90° angle, both relative to each other and relative to the axial sensor. The radial sensor, analogous to the axial sensor, can measure the distance to the measuring scale, but in a radial direction. The radial sensor can be of the same type as the axial sensor, differing only in its arrangement relative to the shaft.

[0062] - Optionally, the sensor unit can also include two axial sensors or instead two radial sensors, which are arranged offset from each other in the area of ​​the scale.

[0063] - It is generally always possible to use a fourth sensor or even more sensors to, for example, calculate the data more precisely based on the overdetermination of the equation system. However, the question arises whether the higher costs associated with additional sensors should be accepted. It is also conceivable to use existing data from the rotary encoder, current data, or patent application. Applicant: Franz Kessler GmbH, Status: 13.12.2025, Our reference: K 9438-PC - 13 -

[0064] To use data from a temperature measurement.

[0065] Furthermore, there is the option of using only distance sensors mounted on the scale or the spindle shaft. However, from a cost perspective, it can be advantageous not to equip the testing device with too many, potentially expensive, distance sensors, but rather to utilize existing sensors if necessary.

[0066] Accordingly, one option is to use an additional distance sensor besides the axial sensor, either axial or radial, and to access other measurement data from the machine tool unit. A rotary encoder is often already provided for determining the speed and, if necessary, also for determining the position. The rotary encoder, in turn, can provide phase information or the axial offset of the spindle shaft. The direction of the force can also be derived from the machine's current data. Depending on the model, the adjusted current values ​​of the spindle drive can behave linearly with respect to the working / process forces. It is also conceivable that the rotating magnetic field of the stator, which can also be derived from the current data, for example, can be used to establish a phase relationship.

[0067] Finally, it is also possible, in a further development of the invention, to manage with a single distance sensor, an axial sensor, and to access all other data from existing components of the machine tool, such as rotary encoders, current data, etc. Patent application Applicant: Franz Kessler GmbH Status: 13.12.2025 Our reference: K 9438-PC - 14 -

[0068] Measurement and evaluation can therefore be performed continuously in real time. As will be shown later, in addition to real-time evaluation, the testing device can also be used with an AI-supported computer system to train an algorithm so that data which can hardly be recorded during operation can be simulated and used.

[0069] Rotary encoder signals or machine current data are also suitable for providing phase information. Since a phase always provides a relative position indication, a starting point is often set for scales, from which the phase is determined. In optical detection, for example, the scale can have an optically perceptible marker. However, in one embodiment of the invention, this starting point as a reference point no longer needs to be an anisotropic change of the scale, because it is possible to define this reference point from the rotary encoder or current data, or other measurement data from the machine control.

[0070] In a particularly preferred embodiment, at least two axial sensors are provided, wherein one, preferably two, of the additional axial sensors (besides the axial sensor already present in the test device) are encompassed by the sensor unit. These can, for example, record two of the measurement series for solving the system of equations for a motion superimposed on the rotational motion, in particular a superimposed vibration. The third measurement series can be recorded by a radial sensor, but can also be calculated by a rotary encoder and / or from the current data of the machine tool or other position data that is already determined. In contrast to conventional machine tool units from the prior art (Intelligence application, Applicant: Franz Kessler GmbH, Date: December 13, 2025, Our reference: K 9438-PC - 15 -), in such an embodiment of the invention, not only radial measurement signals, i.e., signals on a circular circumference, are determined.

[0071] However, it is also conceivable that more than three measurement series are recorded in order to obtain an overdetermination when solving the system of equations and thus obtain more accurate values ​​for the deformation and / or displacement, e.g. two axial sensors, one radial sensor and the acquisition from the current data.

[0072] A typical application is the detection of runout errors. With machine tools, it can happen that tools are not optimally inserted into the tool clamping device during clamping. Sometimes, chips from previous machining processes are responsible, as they have become stuck between the clamping jaws or clamping surfaces and cause the tool to be clamped with a certain deviation, usually at an angle. This generally leads to an imbalance during rotation and a superimposed vibration on the spindle shaft.

[0073] Various types of axial and radial sensors are conceivable, depending on the specific design, such as eddy current / inductive sensors, capacitive sensors, optical sensors, radar sensors, ultrasonic sensors, magnetic field sensors, etc. Particularly with optical sensors, several options are possible. Distances can generally be measured very precisely using an interferometer. In simple cases, phase relationships can also be determined optically by counting markings on the measuring scale. Patent application. Applicant: Franz Kessler GmbH. Date: December 13, 2025. Our reference: K 9438-PC - 16 -

[0074] Especially in, but not exclusively in, capacitive measurement, the measuring instrument can advantageously be made of an electrical conductor to obtain the strongest possible signal. This conductor should be non-magnetic and not made of a ferromagnetic material to avoid generating additional induction. A paramagnetic material, such as aluminum (which is already lightweight), is particularly suitable.

[0075] Axial and radial sensors, as components of the sensor unit or sensors of the sensor unit, and the (at least one) axial sensor already present according to the invention, can be arranged angularly or positionally offset from each other, with the axis of rotation serving as the reference. While the axial sensor is arranged or aligned parallel to the axis of rotation, the radial sensor is aligned perpendicular to the axis of rotation. The axial sensor can be arranged offset from the axis of rotation. Several axial sensors can also be arranged positionally offset from each other, while still oriented parallel to the axis of rotation.

[0076] In one embodiment of the invention, a rotary encoder can be used to determine the rotational speed and / or the angular position of the spindle shaft and / or the acceleration of the spindle shaft. As already described, the sensor unit can be designed as a rotary encoder and / or include a rotary encoder in order to utilize the measurement data from the rotary encoder.

[0077] Optionally, the sensor unit can also be configured to use a signal from the rotary encoder to determine the phase relationship, deformation, and / or displacement. In this respect, the invention can advantageously be used for retrofitting, or a more cost-effective patent application can be filed. Applicant: Franz Kessler GmbH Date: December 13, 2025 Our Reference: K 9438-PC - 17 -

[0078] A machine tool unit can be offered because fewer than three distance sensors are required for the test device, while the measurement data from a rotary encoder already part of the machine tool is used. It is also conceivable that the rotary encoder is integrated into the sensor unit. Instead of or in addition to using the rotary encoder measurement data, current data from the machine tool unit or position data can be used. This data can be read from the machine control system or from other sensors or measuring devices.

[0079] The sensor unit can determine the directional displacement of the spindle shaft, particularly from current data or with the aid of an axial sensor. Temperature can also provide information about the displacement, especially the directional displacement.

[0080] As previously described, the measuring element can be designed as a measuring ring, which is, for example, mounted as a separate aluminum ring on the spindle shaft. The measuring element can then be rotationally symmetrical. If material properties such as magnetization are important for maintaining the sensor signal, a material that is rotationally symmetrical with respect to its material and its properties can also be used, e.g., a uniform magnetic field.

[0081] A force can be calculated from the displacement or deformation, provided the stiffness of the system or tool is also known. This can be estimated, determined experimentally, or calculated using simulations, possibly employing artificial intelligence, machine learning, or other computer-implemented methods. [Applicant: Franz Kessler GmbH, Status: December 13, 2025, Our reference: K 9438-PC - 18 -]

[0082] The algorithm is calculated. Calculating the force allows for a more precise estimation of technical processes, such as the load on the tool, forces acting on the spindle shaft, forces acting on the workpiece, when maintenance is due again, etc.

[0083] Accordingly, the aforementioned advantages for the planning of a machining process and for more precise machining of workpieces can also be used by a method for testing bearing loads of the spindle in operation and for measuring the working and process force of a force acting on at least a part of the rotor unit and / or the spindle shaft and / or for determining the displacement, deformation and movement of the rotor unit in operation in a motor-driven machine tool unit.For this purpose, a machine tool unit according to the invention is also proposed with a storage medium on which a computer program for training a trainable algorithm and for general process optimization, process development and efficiency improvement is stored, wherein the computer program is designed to establish a relationship between the force acting on the spindle shaft or the tool in the system and a set of measurement data which is acquired by the at least one axial sensor and the sensor unit.

[0084] First, a motor-driven machine tool unit is provided, comprising a stator unit and a rotor unit rotatable about a rotary axis. The rotor unit includes a spindle shaft with a measuring surface for detecting the rotational movement and / or displacement and / or deformation and / or movement of the measuring surface of the rotor unit, and which can rotate together with the rotor unit. Patent application. Applicant: Franz Kessler GmbH. Date: December 13, 2025. Our reference: K 9438-PC - 19 -

[0085] The procedure is characterized by the following procedural steps:

[0086] - At least one axial sensor is provided as a distance sensor, with which the deformation and / or displacement on the spindle shaft is measured based on the position of the measuring element in the axial direction.

[0087] Furthermore, a sensor unit is provided, which can itself have sensors, but can also access existing sensors of the machine tool unit and utilize their measurement results. With its help, deformation and / or displacement is determined based on the position of the measuring element in the axial or radial direction and / or the phase relationship in relation to the position of the rotor unit and / or spindle shaft and / or the phase relationship given by the force ratio of the acting forces.

[0088] A corresponding procedure can also be carried out in advance for a machine tool unit so that the parameters from the simulations or the trained algorithms are available later, and thus real-time acquisition can be provided.

[0089] Since not all relevant parameters can be measured directly during operation, the use of simulations is advantageous. Important parameters include the working and process forces, the temperature of the spindle shaft, and the rotational speed of the spindle shaft. Working and process forces, in particular, are not regularly measured directly. In a further development of the invention, a computer-implemented process step can be used, which, for example, relies on evaluation by artificial intelligence. In particular, a trainable algorithm can be used to draw conclusions about the force application. The axial sensor provides one data set, a first subset. A further data set results from, for example, one or two additional distance sensors, i.e., axial or radial sensors, or one axial and one radial sensor.The second subset of measurement data can also contain data on the phase shift between the spindle shaft and other quantities, including temperature measurement data.

[0090] A function of the trainable algorithm is provided. Data from the first and second subsets are input into this function, and the parameters of the trainable algorithm are defined in more detail. The trainable algorithm is trained with respect to the stiffness of the system or tool. The training process can proceed by first running machine learning models.

[0091] Temperature can be used as a correction factor. It leads to strains, which, however, are often undetectable in practice because temperature and expansion would have to be measured precisely at specific points. Therefore, the temperature data can be used to determine how this change must be factored out when the temperature is measured. It is also conceivable that the deformation or displacement of the spindle shaft can be inferred from a temperature measurement. Here, too, a model can be trained if data sets are available on temperature on the one hand, and on distance measurements from axial or radial sensors, phase shift, forces, or force ratios on the other. Patent application Applicant: Franz Kessler GmbH Status: December 13, 2025 Our reference: K 9438-PC - 21 -

[0092] Example implementation:

[0093] An embodiment of the invention is shown in the drawing and is explained in more detail below, including further details and advantages. Specifically, the drawing shows:

[0094] Fig. 1: a schematic representation of the machine tool unit with

[0095] Testing device gladly, the invention.

[0096] Figure 1 shows a schematic representation of a part of a machine tool unit 1 with a stator unit 2 and a rotor unit 3. The rotor unit 3 includes a spindle shaft 4 to which a measuring ring 5 is attached as a dimensional standard. An axial sensor 6 measures the distance to the measuring ring 5 at the end face. A sensor unit 7 is also provided, which includes a radial sensor 8 and access to a rotary encoder 9. Furthermore, a temperature sensor 10 is provided, which supplies temperature values ​​for correction. The outputs of sensors 7, 8, 9, and optionally also of the temperature sensor 10, all lead to the evaluation unit 11 of the test device 12.

[0097] This measuring system can measure displacements, deformations, vibrations, or similar phenomena caused by process forces acting on the spindle shaft 4. Line 13, which coincides with the axis of rotation in the unloaded state in Figure 1, can be considered the deformation line. When the spindle shaft 4 bends due to force, the distance between the measuring ring 5 and the axial sensor 6 will change, as will the associated tilting. [Applicant: Franz Kessler GmbH, Date: December 13, 2025, Our Reference: K 9438-PC - 22 -]

[0098] Change radial sensor 8. The data is supplemented by the output of rotary encoder 9.

[0099] Power data can be read directly from the machine control unit 14. This data connection can also be part of the sensor unit 7.

[0100] In the embodiment shown in Figure 1, the measurement is supplemented by a second radial sensor 15, which is arranged at a 90° angle to the other radial sensor 8. The radial sensor 15 measures the distance perpendicular to the plane of Figure 1 radially to the measuring element (measuring ring) 5 in the direction of the axis of rotation 13. This additional sensor further increases the accuracy because more measurement data is available. For evaluation purposes, it is particularly advantageous if the individual axial and radial sensors 6, 8, 14 are each arranged at a 90° angle to one another, as this simplifies the evaluation compared to other angular distances.

[0101] The test device 12 may be connected to or contain a computer system (PC, mainframe, cloud connection) to perform a computer-implemented evaluation procedure or simulation. This can also be used to train an algorithm by determining parameters such as the stiffness of the system or tool using a training model. The test device 12 can then be used as a component of the machine tool unit 1 to perform real-time control based on the trained algorithm, forward data, and output warning signals, maintenance instructions, or the like to the machine control 14 or directly to a display device. Patent application pending.

[0102] Applicant: Franz Kessler GmbH Date: December 13, 2025 Our reference: K 9438-PC

[0103] - 23 -

[0104] The temporal or position-related signals can be evaluated using a Fourier transformation, at least insofar as the force effects lead to oscillations or vibrations; that is, a spectrum is analyzed and examined for recurring frequencies or peaks at certain frequencies, from which conclusions can be drawn about the bearing load or the runout error.

[0105] The invention advantageously enables a general

[0106] Process optimization, process development and efficiency improvement.

[0107] Patent application

[0108] Applicant: Franz Kessler GmbH Date: December 13, 2025 Our reference: K 9438-PC

[0109] - 24 -

[0110] Reference symbol list:

[0111] 1 machine tool unit

[0112] 2 Stator unit

[0113] 3 Rotor unit

[0114] 4 Spindle shaft

[0115] 5 Measuring ring / standard

[0116] 6 Axial sensor

[0117] 7 Sensor unit

[0118] 8 radial sensor

[0119] 9 rotary encoders

[0120] 10 Temperature sensor

[0121] 11 Evaluation unit

[0122] 12 Test device

[0123] 13 Deformation line

[0124] 14 Machine control

[0125] 15 radial sensor

Claims

Patent application Applicant: Franz Kessler GmbH Status: 13.12.2025 Our reference: K 9438-PC / AA - 1 - Claims:

1. Motor-driven machine tool unit (1) with a stator unit (2) and a rotor unit (3) rotatable about a rotary axis (13), wherein the rotor unit (3) has a spindle shaft (4) which includes a measuring element (5) with a measuring surface for detecting the rotational movement and / or the displacement and / or deformation and / or the movement of the measuring surface of the rotor unit (3) and which can rotate together with the rotor unit (3), wherein a test device (12) is provided for testing bearing loads of the spindle in operation, which serves for measuring the working and process force of a force acting on at least a part of the rotor unit (3) and / or the spindle shaft (4) and / or for determining the displacement, deformation and movement of the measuring surface of the rotor unit (3) in operation, characterized in that the test device (12) comprises: • an axial sensor (6) for measuring deformation and / or displacement on the spindle shaft (4), • wherein the axial sensor (6) is arranged and / or configured to measure the deformation and / or displacement based on the position of the measuring element (6) in the axial direction, and • a sensor unit (7) for determining the deformation and / or displacement based on the position of the scale (5) in the axial or radial direction as well as the phase relationship in relation to the position of the rotor unit (3) and / or spindle shaft (4) and / or the phase relationship given by the force ratio of the acting forces.

2. Machine tool unit (1) according to claim 1 , characterized in that the sensor unit (7) comprises as a further sensor: • at least one radial sensor (8, 15) for measuring deformation on the spindle shaft (4), which is arranged and / or designed to measure the deformation based on the position of the measuring element (5) in the radial direction, and / or • at least one further axial sensor for measuring a deformation on the spindle shaft (4), which is arranged and / or designed in such a way as Patent application Applicant: Franz Kessler GmbH Status: 13.12.2025 Our reference: K 9438-PC / AA - 2 - is that it measures the deformation based on the position of the physical element (5) in the axial direction.

3. Machine tool unit (1) according to one of the preceding claims, characterized in that the test device (12) is designed to perform at least three measurement series in parallel, wherein one of the measurement series is carried out by the axial sensor (6) and at least two of the measurement series are carried out by the sensor unit (7) or the measurement data for at least two of the measurement series are determined by the sensor unit (7) in order to solve a system of equations of a motion superimposed on the rotational motion, in particular a superimposed vibration.

4. Machine tool unit (1) according to one of the preceding claims, characterized in that the testing device (12) comprises, in addition to the axial sensor (6), the sensor unit (7) which: • has two further axial sensors for determining the deformation and / or displacement based on the position of the scale (6) in the axial direction in order to determine the ring tilt of the rotor unit (3) and / or the spindle shaft (4), and / or • has two radial sensors (8, 15) for measuring deformation on the spindle shaft (4), which are arranged and / or designed to measure the deformation based on the position of the measuring element (5) in the radial direction.

5. Machine tool unit (1) according to one of the preceding claims, characterized in that the at least one axial and / or radial sensor (6, 8, 15) is / are designed as: • Eddy current sensor and / or • capacitive sensor and / or • optical sensor, in particular interferometer or for detecting and / or counting markings on the scale and / or • Radar sensor and / or • Ultrasonic sensor and / or • Magnetic field sensor. Patent application Applicant: Franz Kessler GmbH Status: 13.12.2025 Our reference: K 9438-PC / AA - 3 - 6. Machine tool unit (1) according to one of the preceding claims, characterized in that the sensor unit (7) comprises at least one axial and / or radial sensor (8, 15) which is / are arranged angularly offset from each other in relation to the axis of rotation (13), in particular by 90°, and / or positionally offset and / or which is / are arranged angularly offset in relation to the axis of rotation (13), in particular by 90°, and / or positionally offset from the other axial sensor (6).

7. Machine tool unit (1) according to one of the preceding claims, characterized in that a rotary encoder (9) is provided for determining the rotational speed and / or the angular position of the spindle shaft (4) and / or the acceleration of the spindle shaft (4), wherein the sensor unit (12) is designed as a rotary encoder and / or comprises a rotary encoder (9) and / or wherein the sensor unit is designed to use a signal from the rotary encoder (9) to determine the phase relationship, deformation and / or displacement.

8. Machine tool unit (1 ) according to one of the preceding claims, characterized in that the sensor unit (12) is designed as a device for recording current data of the machine tool unit (1 ) and / or position data.

9. Machine tool unit (1 ) according to one of the preceding claims, characterized in that the sensor unit (12) is designed to detect the direction-dependent displacement of the spindle shaft (4) and / or the temperature (10) to determine a displacement or deformation of the spindle shaft (4).

10. Machine tool unit (1 ) according to one of the preceding claims, characterized in that the testing device (12) is designed to: • to convert the measured values ​​of the axial sensor (6) and the sensor unit (7) back to a response signal of the form s = Aaxiai cos(c-cp) + B, where s is the distance measurement value, Aaxiai is the axial deformation amplitude, B is the axial displacement / deformation offset, c is the angular position of the axial sensor, and p is the angular position of the applied force. Patent application Applicant: Franz Kessler GmbH Status: 13.12.2025 Our reference: K 9438-PC / AA - 4 - and / or calculate back to a response signal of the form s = Aradiai cos(c-tp), where s is the distance measurement value, Aradiai is the axial deformation as amplitude, c is the angular position of the axial sensor and tp is the angular position of the applied force, and / or solve the system of equations with the measured values ​​for s and the known angular position c and / or • to determine the center point of the rotating spindle shaft (4) in the loaded and unloaded state using the measured values ​​of the axial sensor (6) and the sensor unit (12).

11. Machine tool unit (1) according to one of the preceding claims, characterized in that the testing device (12) is configured to calculate, starting from a response signal of the form s = Aaxiai cos(c-cp) + B, where s is the distance measurement values, Aaxiai as amplitude is the axial deformation, B as offset is the axial displacement / deformation, c is the angular position of the axial sensor and cp is the angular position of the applied force, and / or to calculate back from a response signal of the form s = Aradiai cos(c-cp), where s is the distance measurement values, Aradiai as amplitude is the axial deformation, c is the angular position of the axial sensor and cp is the angular position of the applied force, the axial deformation Aaxiai based on a deflection curve model to represent the deformation of the spindle shaft from the radial deformation Aradiai and / or vice versa.

12. Machine tool unit (1 ) according to one of the preceding claims, characterized in that the dimensional embodiment (5) is designed as a measuring ring which is geometrically and / or rotationally symmetric with respect to its material.

13. Machine tool unit (1 ) according to one of the preceding claims, characterized in that the testing device (12) is designed to determine the force acting on the spindle shaft (4) and / or the stiffness of the tool based on the stiffness.

14. Machine tool unit (1) according to one of the preceding claims, characterized in that a tool is mounted on the spindle head with a tool holding unit and with a longitudinal axis of rotation. Patent application Applicant: Franz Kessler GmbH Status: 13.12.2025 Our reference: K 9438-PC / AA - 5 - adjustable and subjected to a clamping force tool clamping device is releasably clamped and fixed.

15. Machine tool unit (1) according to one of the preceding claims with a storage medium on which a computer program for training a trainable algorithm and for general process optimization, process development and efficiency improvement is stored, wherein the computer program is configured to establish a relationship between the force acting on the spindle shaft (4) or the tool in the system and a set of measurement data acquired by the at least one axial sensor (6) and the sensor unit (7), wherein the computer program is configured to record the set of measurement data as a first subset by acquiring measurement data from the axial sensor (6), and as a second subset measurement data, in particular measurement data from the sensor unit (7), about the phase shift between the spindle shaft and the eddy current, capacitance or distance measurement data,and / or to record the directional displacement of the spindle shaft (4) and / or temperature measurement data, as well as to determine data on the parameters of the trainable algorithm by inputting data from the first and second subsets into a function of the trainable algorithm, which establishes the relationship between the force acting on the spindle shaft (4) and the measurement data of the first and second subsets, wherein the parameters of the trainable algorithm are set such that they reflect the stiffness of the tool of the system or of the spindle shaft in the system.

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