Method for controlling a chuck

Abstract

The invention relates to a method for controlling a chuck, in particular a precision chuck for measuring devices, wherein clamping elements, in particular clamping jaws, are driven by way of an electrical actuating element, in particular at least one electric motor, wherein the current (11) received by the electrical actuating element is measured by sensors and a clamping force during closing is determined on the basis of a maximum current (11). In a first step of said method, the current (11) of the actuating element is adjusted by a control device in such a way that the clamping elements are moved in the closing direction at a predetermined speed (12) detected by speed sensors; in a second step, the decrease in speed (12) when the clamping jaws make contact is detected; and in a third step, the current (11) of the actuating element is adjusted to a specified value (18) by the control device and the clamping elements are clamped.

Description

[0001] P20337- 24.03.2026 - Ws

[0002] 1

[0003] Description

[0004] Method for controlling a chuck

[0005] The invention relates to a method for controlling a chuck, in particular a precision chuck for measuring devices, according to the preamble of claim 1.

[0006] Chucks are known in the prior art and are used in machine tools, especially lathes but also milling machines and machining centers, to fix and hold a workpiece during machining.

[0007] The chuck can be mounted on a rotatable bearing to allow for workpiece positioning via a rotary motion, for example in a machining center or milling machine. In lathes, the chucks are connected to and mounted on the rotating axis.

[0008] It is further known in the prior art that, in order to achieve automated manufacturing or generally to enable faster processing, the chuck has a clamping device operated by drives, in particular electric motors.

[0009] From DE 1 287904 B, an electrically operated chuck for lathes or the like for clamping workpieces is known.

[0010] Chucks with the same basic or similar construction, but manufactured with much greater precision and designed for lower clamping forces, are used as precision chucks in measuring devices. For example, a manufactured bevel gear for a differential can be clamped in such a precision chuck on the measuring table of a measuring device and checked for compliance with dimensional specifications. For this purpose, after clamping, the precision chuck, which is rotatably mounted, is rotated into a defined measuring position and measured with probes. P20337- 24.03.2026 - Ws

[0011] 2

[0012] DE 31 01 301 A1 discloses a method for determining clamping force via current. The clamping force of clamping jaws on the workpiece is limited and regulated by electrical or mechanical devices until the desired clamping force value is reached. An electrical comparator circuit is used, the voltage of which can be preselected for operation and whose value can be changed by known means, so that it is possible to directly read the clamping force of the clamping jaws on the workpiece by transferring the voltage value to a display instrument.

[0013] However, DE 31 01 301 A1 does not offer a solution for clamping a large number of workpieces, especially test pieces, in a measuring device with a defined force and / or releasing them from the clamping device in the shortest possible optimized time.

[0014] The present invention is therefore based on the objective of providing a method for controlling the clamping force of a chuck, in particular a precision chuck for measuring devices, which avoids these disadvantages and enables quick clamping and release of workpieces or test pieces.

[0015] This problem is solved by a method comprising the features of independent claim 1 and independent claim 5. Advantageous embodiments of the invention are specified in the dependent claims.

[0016] According to a particular feature of the invention, a method for controlling a chuck is described, which is particularly suitable for precision chucks in measuring devices. The clamping elements, such as jaws, are driven by an electric actuator, preferably an electric motor. The current drawn by this actuator is measured by sensors, and the clamping force when closing the jaws is determined based on a maximum current. In a first step, the current of the actuator is regulated by a control device so that the clamping elements are moved in the closing direction at a predetermined speed, which is detected by speed sensors. As soon as the jaws come into contact, the decrease in speed is detected in the second step. In the third step, the P20337- 24.03.2026 - Ws

[0017] 3

[0018] The current of the actuator is regulated to a preset value, and the clamping elements are tensioned. The speed sensors can also be configured so that, for example, the rotational speed of an electric motor is detected as an actuator, possibly by calculation.

[0019] One advantage of the described method lies in the precise control of the clamping force, achieved by measuring and regulating the current of the electrical actuator. This enables the fast and efficient clamping and releasing of workpieces, especially test pieces, in measuring fixtures. A further advantage is the ability to precisely control the speed of the clamping jaw movement, resulting in optimized and safe handling of the workpieces. In particular, excessive clamping, which could potentially compromise the precision of a measurement, is avoided.

[0020] According to one embodiment, the target value for the current is determined by clamping a test specimen with sensor devices for measuring the clamping force for a desired clamping force.

[0021] These sensors on the test specimen are capable of precisely measuring the clamping force and transmitting the data to the control device. Using a test specimen with sensors offers the advantage that the clamping force is not only calculated theoretically, but also measured and verified practically in a calibration measurement for adjusting the clamping device. Such a measurement can also be repeated at regular intervals or after a specific number of operating cycles for readjustment.

[0022] This is particularly advantageous in automated manufacturing processes where a large number of workpieces need to be clamped and released quickly. Precise measurement and control of the clamping force also minimizes the risk of workpiece damage and increases measurement accuracy, as the clamping force is always optimally and consistently set.

[0023] According to one embodiment of the method for controlling a chuck, a method for determining the clamping force of a chuck is described, in which values ​​for several test specimens, in particular for a test specimen with minimum P20337- 24.03.2026 - Ws

[0024] 4

[0025] The diameter and a test specimen with a maximum diameter are determined. These minimum or maximum diameters can be close to or at the values ​​that allow the maximum dimensions of the chuck geometry. From these values, a characteristic curve of the clamping element's path is calculated, either as an average value or as a reference value, and used as a target value. The position of the clamping elements, and thus their position along the path, can be determined, for example, by integrating time at a specific speed of movement, starting from the end positions.

[0026] Integrating the sensors and control device into the chuck can enable automated and user-friendly operation, thus relieving the operator and increasing productivity.

[0027] According to an independent embodiment of the invention, a further method for controlling a chuck is described, which is particularly suitable for precision chucks in measuring devices. The clamping elements, such as jaws, are driven by an electric actuator, preferably an electric motor. Sensors measure the current drawn by the actuator. The method is characterized in that, to open the clamped chuck, the current of the actuator is regulated by a control device to generate a force in the opening direction of the clamping elements. The current is continuously increased until speed sensors detect an opening movement. Upon exceeding a threshold value, the current is regulated to a travel value.The current corresponding to the travel value is maintained by the control device until the clamping elements have reached the desired position, in particular a desired distance to the workpiece.

[0028] One advantage of the method lies in the precise control, which enables fast and efficient workpiece release. Another advantage is the continuous monitoring and adjustment of the current, which ensures a controlled opening movement of the clamping elements. This results in optimized clamping and releasing times for workpieces, which is particularly important for measuring devices, as it improves the efficiency and accuracy of the measurement processes. A defined distance from the test piece or workpiece can also be achieved, enabling safe and fast handling. P20337- 24.03.2026 - Ws

[0029] 5

[0030] Removal, for example by robots, is made possible if their specifications for safety distances are strictly adhered to.

[0031] Advantageously, the two previously described independent methods can be combined into one method.

[0032] In another embodiment, the actuator and / or a gear ratio between the actuator and the clamping elements can maintain the clamping force without current through self-locking. This means that after clamping, the current is set to zero, creating an energy-efficient solution that minimizes power consumption once the desired clamping force is reached. The self-locking of the actuator or gear ratio ensures that the clamping force is maintained even without a continuous power supply. This is particularly advantageous because it reduces operating costs and extends the service life of the electrical components, as they do not need to be constantly energized. Self-locking can be achieved through various mechanical principles, such as self-locking gears, which, due to their design, only allow movement under specific conditions and thus maintain a stable clamping force.

[0033] The clamping elements can be radially movable clamping jaws and can be clamped by a rotatable spiral groove disc, wherein the spiral groove disc is connected to a hollow gear and the adjusting element is a motor unit that can be used as a unit and is arranged in a fixed position in the chuck with a drive gear oriented radially outside parallel to an axis of the hollow gear, so that the drive gear engages in the hollow gear and can rotate it.

[0034] One advantage is the compact design of the motor unit, which can be used as a single unit and is fixed in position within the chuck. This design allows for easy installation and maintenance of the motor unit, as it is conceived as a compact unit that can be easily integrated into the chuck. This contributes to reduced downtime and increased efficiency in chuck operation. P20337- 24.03.2026 - Ws

[0035] 6

[0036] Further advantages and details of the invention are explained in more detail with reference to the exemplary embodiment shown in the schematic figures. Here,

[0037] Fig. 1 shows a section of a precision chuck in which the method according to the invention is carried out.

[0038] Fig. 2 shows the precision chuck of Fig. 1 in perspective view,

[0039] Fig. 3 schematically shows the inventive method for clamping the precision chuck and

[0040] Fig. 4 schematically shows the inventive method for opening the precision chuck,

[0041] Fig. 1 shows a cross-section of a chuck 1 as a precision chuck in which the method according to the invention is carried out. The chuck 1 comprises several essential components that are used to generate and control the clamping force.

[0042] The figure shows a housing 2 of the chuck, which contains the various mechanical and electrical components and is mounted on a flange plate 10. Clamping elements, in particular clamping jaws 4, are arranged inside the housing 2. These jaws are radially movable and can be clamped by a rotatable spiral groove disc 5. The spiral groove disc 5 is connected to a hollow gear 6, which is driven by an electrical actuator, in particular an electric motor 7.

[0043] The electric motor 7 is designed as a motor unit and is arranged in a fixed position in the chuck 1. A drive gear 8 of the electric motor 7 is oriented parallel to the axis of the hollow gear 6 and arranged radially outwards, so that the drive gear 8 engages with the hollow gear 6 and can rotate it. The rotational movement of the hollow gear 6 moves the spiral groove disc 5, which in turn moves the clamping jaws 4 radially, thus clamping or releasing the workpiece. P20337- 24.03.2026 - Ws

[0044] 7

[0045] Furthermore, sensors for measuring the current consumed by the electric actuator are integrated. These sensors detect the current consumption of the electric motor 7 and enable precise control of the clamping force. Control is achieved by a control device that regulates the current of the actuator and thus controls the movement of the clamping jaws 4.

[0046] The figure also shows the mechanical connection between the electric motor 7 and the clamping jaws 4, including the gear ratio, which, through self-locking, can maintain the clamping force without current. This makes it possible to set the current to zero after the workpiece has been clamped, thus saving energy while still maintaining the clamping force.

[0047] Additionally, speed sensors are provided to detect the movement of the clamping jaws. These sensors play a crucial role in controlling the clamping process by monitoring the speed of the clamping jaws 4 and detecting a drop in speed as the clamping jaws 4 come into contact. Based on this information, the current of the actuator is regulated to a preset value to achieve the desired clamping force.

[0048] Fig. 2 shows the chuck 1 of Fig. 1 in a perspective view. The chuck 1 consists of the housing 2, which has a cylindrical shape and a flange plate 10 at its base for mounting on a work surface or measuring table. The chuck is equipped with several radially movable clamping jaws 4 or clamping elements 3, which serve to securely fix a workpiece. The clamping jaws 4 are arranged evenly around the central axis of the chuck 1 and can be adjusted by the rotatable spiral groove disc 5 in Fig.

[0049] 1. This spiral grooved disc 5 is connected to the hollow gear 6 in Fig. 1, which is driven by an electric actuating element, in particular the electric motor.

[0050] Fig. 3 schematically shows the inventive method for clamping the chuck 1. The temporal behavior of current 11 and velocity 12 during the clamping process of the chuck 1 is shown. [Reference: P20337- 24.03.2026 - Ws]

[0051] 8

[0052] shows the different phases 13 of the clamping process, starting with the readiness phase 14, the application 15, the closing 16, the clamping 17 and the renewed readiness phase 14 .

[0053] In the first phase, the readiness phase 14, both the current 11 and the velocity 12 are at a low level, indicating that the chuck 1 is in an inactive state. As soon as the clamping process is initiated, the current 11 increases, shown as a dashed line (green line), to set the clamping elements 3 in motion. Simultaneously, the velocity 12 increases, shown as a solid line (red line), representing the movement of the clamping elements 3 in the closing direction.

[0054] During the clamping phase 15, the velocity 12 remains constant, while the current 11 continues to remain at an elevated level. This indicates that the clamping elements 3 are coming into contact with the workpiece and beginning to clamp onto it. Once the clamping elements are fully closed, the velocity 12 drops at the contact point 23. However, the current 11 remains at an elevated level to maintain the clamping force.

[0055] During the clamping phase 17, the current is regulated to a setpoint value 18. The speed 12 effectively drops to zero, as the clamping elements 3 firmly grip the workpiece. The setpoint value 18 for the current 11 is determined through prior measurements and calibrations in a verification measurement to achieve the desired clamping force. The verification measurement can be performed only once or repeated after a certain number of operating cycles.

[0056] After the clamping process is completed, the system returns to the standby phase 14, whereby both the current 11 and the speed 12 drop to zero and the closed state of the chuck is maintained by the self-locking mechanism.

[0057] Figure 4 schematically shows the inventive method for opening the chuck. The x-axis of the diagram represents different phases of the clamping or opening process on a time axis, starting with (also here P20337- 24.03.2026 - Ws)

[0058] 9

[0059] a readiness phase 14, followed by starting up 19, opening 20 with position control.

[0060] The y-axis represents the values ​​for current 11 and velocity 12. The dashed (green) line in the diagram represents the current 1, which is absorbed by the electrical actuator, while the solid (red) line represents the velocity 12 of the movement of the clamping elements or the actuator connected to them.

[0061] In the ready phase 14, the current and speed are zero, as there is no movement of the clamping elements and the chuck is held closed by its own locking mechanism.

[0062] During the start-up phase 19, the current for one opening direction is initially increased to set the clamping elements in motion. From a breakaway torque 21 onwards, this leads to an increase in the velocity 12 in the opening direction; therefore, in contrast to the values ​​in Fig. 3, these are negative values, as is the case with the current 11.

[0063] In the opening phase 20, the current is regulated to a travel value to further open the clamping elements. This phase simultaneously serves as position control, in which the current 11 is maintained at the constant travel value to move the clamping elements into a desired position. The speed remains constant in this phase until the desired position is reached, corresponding to a defined, but as small as possible, safe distance when using a measuring device. To decelerate, a positive braking current is applied until the speed is zero. Afterwards, the process returns to the standby phase 14.P20337- 24.03.2026 - Ws

[0064] 10

[0065] List of reference signs

[0066] 1 chuck

[0067] 2 cases

[0068] 3 clamping element

[0069] 4 clamping jaws

[0070] 5 spiral groove disc

[0071] 6 Hollow gear

[0072] 7 Electric motor

[0073] 8 Drive gear

[0074] 9 Control device

[0075] 10 Flange plate

[0076] 11 Electricity

[0077] 12 Speed

[0078] 13 phases

[0079] 14 Standby phase

[0080] 15. Create

[0081] 16 Close

[0082] 17 spans

[0083] 18 Default value

[0084] 19 Starting

[0085] 20 Open

[0086] 21 Breakaway torque

[0087] 22 Travel value

[0088] 23 Landing point

Claims

P20337- 24.03.2026 - Ws 11 Patent claims 1. Method for controlling a chuck, in particular a precision chuck for measuring devices, wherein clamping elements, in particular clamping jaws, are driven by an electrical actuating element, in particular at least one electric motor, wherein the current (11) received by the electrical actuating element is measured by sensors and a clamping force is determined on the basis of a maximum current (11) when closing, characterized by that in a first step the current (11) of the actuating element is regulated by a control device so that the clamping elements are moved in the closing direction at a predetermined speed (12) detected by speed sensors and In a second step, the decrease in speed (12) is recorded when the clamping jaws come into contact, and in a third step the current (11) of the actuating element is regulated to a preset value (18) by the control device and the clamping elements are clamped.

2. Method according to claim 1 , characterized by that the target value (18) for the current (11) is determined by clamping a test specimen with sensor devices for measuring the clamping force for a desired clamping force.

3. Method according to claim 2, characterized by that values ​​for several test specimens, in particular one with minimum diameter and one with maximum diameter that can be clamped, are determined and the target value (18) is formed as a characteristic curve of the path or as an average value.

4. Method for controlling a chuck, in particular a precision chuck for measuring devices, wherein clamping elements, P20337- 24.03.2026 - Ws 12 in particular clamping jaws, are driven via an electric actuating element, in particular at least one electric motor, wherein the current (11) absorbed by the electric actuating element is measured by sensors, characterized in that that, in order to open the clamped chuck, in a first step the current (11) of the actuating element is regulated by a control device such that a force in the opening direction of the clamping elements is generated and the current (11) is continuously increased In a second step, an opening movement is detected by speed sensors and, if a threshold value is exceeded, the current (11) is regulated to a travel value (22), and in a third step the current (11) is maintained by the control device at the level of the travel value (22) until a desired position of the clamping elements is reached, in particular a desired distance to the workpiece.

5. Method combining one of the methods according to claims 1 to 3 in combination with a method according to claim 4.

6. Method according to claim 5, characterized by that the actuating element and / or a gear ratio between the actuating element and the clamping elements can maintain the clamping force without current (11) by means of self-locking and that after clamping (17) in a fourth step or in the clamped state the current (11) is set to zero.

7. Method according to one of claims 5 or 6, characterized by that the clamping elements are radially movable clamping jaws and can be clamped by a rotatable spiral groove disc, wherein the spiral groove disc is connected to a hollow gear and the adjusting element is a motor unit that can be used as a unit and is arranged in a fixed position in the chuck with a drive gear oriented radially outside parallel to an axis of the hollow gear, so that the drive gear engages in the hollow gear and can rotate it.

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