Machine tool and method for controlling machine tool

Abstract

To provide a machine tool capable of improving safety of data communication compared to conventional technology by forming connection between a machine control unit and a clamping device.SOLUTION: The problem is solved by that a clamping device control unit is associated with a clamping device, and the clamping device control unit includes two redundant microprocessors which evaluate received process data sets independently of one another and, in the event of an error, transfer the clamping device into a safe state.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The invention relates to a machine tool having a stationary machine control and a rotating clamping device, the machine control being in communication with a clamping device control which rotates together with the clamping device via a coupling unit which provides a contactless data connection to the machine control to the clamping device control, the clamping device control having a control unit for driving and controlling a propulsion means for actuating the clamping means of the clamping device, the control unit being associated with at least two redundant microprocessors, by means of which process data sets received from the machine control via the control unit can be checked independently of one another and / or process data received from process sensors can be used independently of one another for the process data sets and can be transmitted via the control unit to the machine control, the invention also relates to a method for controlling such a machine tool.

[0002] Such a machine tool is already known from EP 4015144 A1. For further prior art, reference is first made to EP 3620248 A1, in which a coupling device for a machine tool is provided, by means of which an electrical connection with an induction-actuated chuck can be achieved as easily as possible, independently of a customer-specific assembly of the machine tool, and which ensures monitoring of the function of the chuck and of the chuck jaws attached thereto.

[0003] This is achieved by arranging the programmable interface such that a coupling is intermediately connected to the chuck such that the interface is drivable by a control unit of the machine control.

[0004] However, the problem arises from this: it is not possible to ensure that control signals, in particular safety-critical signals, such as STO signals (Safe-Torque-Off-Signal), are correctly transmitted and correspondingly received by the inductive coupler.

[0005] This stop function is the most common safety function, which means that the drive is no longer supplied with energy that would cause it to rotate or move. The drive coasts to a stop without torque. Unintentional restarts are also prevented by this stop function.

[0006] Although the conventional technology does have redundant checks, the transmission path via the inductive coupler is the same for the two redundant controls, so that when a data packet is lost in the first control, there is a high risk that the corresponding data packet will also be lost in the redundant second control.

[0007] Additionally, see US Patent Application Publication No. 2006 / 176823 for further prior art.

[0008] Against this background, the problem underlying the present invention is to create a machine tool in which a connection between the machine control and the clamping device is formed such that the security of data communication is improved over the prior art.

[0009] This is achieved by a machine tool according to the characterizing features of independent claim 1 and by a method for controlling such a machine tool according to the characterizing features of parallel claim 6. Advantageous embodiments of such a machine tool and the corresponding method for controlling it can be taken from the respective dependent claims which follow these.

[0010] According to the invention, a machine tool is provided with a stationary machine control and a rotating clamping device, the machine control communicating with a clamping device control rotating together with the clamping device via a coupling unit, characterized in that the machine control is data-connected to the clamping device control in a contactless manner by the coupling unit, the clamping device control having a control unit for driving and controlling a drive means for actuating the clamping means of the clamping device, the control unit being associated with at least two redundant microprocessors, by means of which process data sets received from the machine control via the control unit can be checked independently of one another and / or process data received from process sensors can be used independently of one another for the process data sets and can be transmitted to the machine control via the control unit.

[0011] This results in a machine control on the machine tool side and a clamping device control on the clamping device side, which communicate with each other via an intermediate coupling unit. The drive means, which enable the drive of the clamping means with respect to each other, can be controlled by the controller. With this drive, with clamping means opposite each other, these clamping means enclose the workpiece from opposite sides if the number of clamping means is even. In the case of a clamping device with three clamping means, an offset of 120° is selected instead of the corresponding side, with five clamping means an offset of 72° is selected, etc. As a result, the workpiece is centered between the clamping means.

[0012] To provide improved data security, the process data sets received from the control unit of the clamping device control and thus representing the output signals of the machine control are evaluated by two microprocessors of the same type, which are provided redundantly with respect to one another. The received process data sets contain, among other things, the STO signal, whereas all process data contain the calculated signature and a consecutive identification number. If the microprocessor determines that the value of the STO signal indicates a safe operating mode, it transmits this to the controller of the clamping means, which is respectively assigned to them, and thus opens the clamping means and thus the propulsion means or the servo motor cannot operate until the safe mode is deactivated again by the STO signal. In particular, a value of 1 for the STO signal indicates a safe operating state, and a value of 0 for the STO signal allows the safe operating state to be deactivated. This allows coding in short messages as a whole, which can be transmitted by a very simple infrastructure.

[0013] If an invalid signature is received, which includes an erroneous CRC code, a Huffman code, an incorrect check digit or the like, this indicates a malfunction and communication is no longer safe. The microprocessor therefore forwards this to the control unit of the fastening device control, which safely stops the machine. The same is done if the received identification number does not match the expected sequential identification number, since communication may be looping or totally blocked.

[0014] Microprocessor redundancy allows for increased security in that errors are detected and identified. It is possible to use more than two microprocessors, but operation is always possible with just two microprocessors.

[0015] Even if the process data sets are collected and transmitted as input signals for the machine control, microprocessor redundancy is advantageous: all safety-critical sensors, in particular force sensors or tension signal generators, which, for example, inform the zero-point tensioning system of the tensioning state, each communicate with one microprocessor, which in turn can communicate with several different sensors.

[0016] Within the scope of communication, different signals of these microprocessors can be handled, whereby each microprocessor transmits its own signal to the control unit, which in turn generates a signal for the machine control, or a circular process data set is generated, into which the microprocessors insert the signals processed by these microprocessors and in this respect supplement the process data set.

[0017] With some advantages, the drive means of the clamping means can be a servomotor controlled by a servocontroller, which moves the clamping means in the clamping device in the direction of the workpiece to be centered until the workpiece is held with a preset force and the drive is terminated. In this case, a friction-coupled brake ensures that the position once taken is not retracted until an opening signal is received. A mechanical self-locking is also provided via a gearbox.

[0018] In a first embodiment, the tightening means can furthermore each be associated with at least one force sensor or tightening signal generator, whereby each force sensor or tightening signal generator is data-connected to only one microprocessor. In this case, a number of microprocessors, the same number as the tightening means, are used. The use and cooperation of a large number of microprocessors is costly and cumbersome, so this embodiment is not preferred.

[0019] Preferred is an embodiment in which at least one force sensor or tightening signal generator is associated with each of the tightening means and the force sensors or tightening signal generators of several tightening means are associated with a microprocessor, the force sensors or tightening signal generators of opposing tightening means being associated with different microprocessors. Here, the opposing tightening means of a pair are each monitored by a different microprocessor, and the coupling is such that the monitoring of each pair is carried out by two microprocessors. This means that in this embodiment, two microprocessors are always required, regardless of how many tightening means are ultimately used.

[0020] In another variant, the clamping means can each be associated with at least one force sensor or clamping signal generator, and at the same time the microprocessor can be associated with the force sensors or clamping signal generators of several clamping means, the force sensors or clamping signal generators of clamping means having oppositely acting force components being associated with different microprocessors. Thus, in particular, if the chuck is provided with three chuck jaws, two of them can be monitored by one microprocessor and the third chuck jaw by another microprocessor.

[0021] Furthermore, a displacement sensor, which is data-connected to the control unit, can be configured to be associated with the clamping means. Here, this is not a safety-relevant measured value, since critical states cannot be calculated from the mere position of the clamping means. These measured values ​​are therefore not transmitted to the microprocessor, but only to the control unit of the clamping device control.

[0022] In a specific embodiment, the coupling device can form an inductively coupled data connection between the machine control and the clamping device control. Inductive coupling is advantageous, since it allows both energy coupling and signal coupling. However, in the present invention, it is also possible, for example, to provide a hydraulic coupling, while the signal coupling can be performed inductively. A contactless coupling is necessary in the first place due to the situation that signal and energy transmission must be achieved from a stationary machine tool to a rotating clamping device.

[0023] One advantage is that the fastening device control communicates with the machine control based on the Ethernet protocol, which is a fast and robust protocol that also allows wireless communication. A PROFINET connection can be used here, for example, whereas bus systems, such as CANBUS, can also be used in the fastening device control and / or in the machine control.

[0024] The present invention will be described in more detail below with reference to examples. [Brief description of the drawings]

[0025] [Figure 1] 1 is a schematic diagram of a machine tool having a clamping device and a machine control connected via a coupler to a clamping device control associated with the clamping device; [Diagram 2] FIG. 2 is a more detailed schematic diagram of the machine tool showing details of the clamping device control and the machine control.

[0026] 1 shows a schematic diagram of a clamping device 1 with two pairs of clamping means 2, 3, around which a workpiece 4 is held, each offset by 90°. A clamping device control 20 of the clamping device 1 communicates via an inductive coupler 7 with a machine control 10 of a machine tool, which in this example has a control unit 11, a safety control unit 12 and a power supply 5 shown separately. The control units 11 and 12, as well as the control unit 21 of the clamping device control 20, can in particular be embodied as a memory programmable control (SPS: Speicherprogrammierbare Steuerung).

[0027] The control unit 11 outputs control signals to the clamping device control 20, for example by the running program or by user settings at an interface not shown in the figure, whereas the safety control unit 12 is mainly or exclusively used for the communication of safety-relevant signals. This includes in particular the transmission of force signals which indicate the force with which the clamping means 2, 3 grip the workpiece. In order to improve the security of the data transmission via the inductive coupler 7, the invention provides for redundant monitoring of the signals transmitted to the control unit 21 of the clamping device control 20 by means of the redundantly implemented microprocessors 22, 23 in the clamping device control 20. The transmission via the inductive coupler 7 is a normal simple communication channel and is initially unprotected. The evaluation of the signals passing through the inductive coupler 7 by two independent microprocessors 22, 23 is therefore effective for improving the security of the data transmission.

[0028] As a complement to the broad division of Figure 1, this situation is depicted in more detail in Figure 2, but with individual sub-aspects omitted.

[0029] It is shown by way of example of two clamping means 2, 3 by means of which the workpiece 4 can be centered. For this purpose, the clamping means 2, 3 can be displaced by means of servo motors 26, 27, which are monitored by displacement sensors 32, 33. This is controlled by means of a control unit 21 of the clamping device control 20 via a CAN bus, via which the servo controllers 29, 30 are data-connected to the control unit 21. The control setpoints are obtained from the machine control 10, in particular from the control unit 11 in the machine control 10, whereas a direct drive control of the servo controllers 29, 30 is performed, via which the drive control of the servo motors 26, 27 is performed in the clamping device control 20. The clamping device control 20 and the machine control 10 are data-connected via an inductive coupler 7, as already shown in FIG. 1.

[0030] In particular, the control command is first transmitted by corresponding programming to the control unit 11 of the machine control 10. The control unit 11 itself transmits the control command via the inductive coupler 7 to the control unit 21 of the clamping device control 20. In accordance with this, the control unit 21 causes, for example, the clamping means 2, 3 to close, i.e. to move towards the workpiece 4. A corresponding control signal 28 is transmitted to two servo controllers 29, 30, which themselves correspondingly drive the servo motors 26, 27. Displacement sensors 32, 33 monitor the positions of the respectively assigned clamping means 2, 3 and feed these positions back to the control unit 21.

[0031] At the same time, however, the forces acting on the tightening means 2, 3 are also detected. For this purpose, a force sensor 35, 36 is assigned to each tightening means 2, 3, which communicates with the microprocessor 22, 23 and transmits a status signal 31 to it. In order to achieve a sufficient redundancy in the data acquisition, a first force sensor 35 associated with a first tightening means 2 communicates with the first microprocessor 22, whereas a further force sensor 36 associated with a further tightening means 3 communicates with the second microprocessor 23. The microprocessor 22, 23 receives the force signal and writes it into a process data set, which is filled in a cyclical manner by the microprocessor 22, 23 and then transmitted by the control unit 21 to the machine control 10. In the machine control 10, in particular by the safety control unit 12, the signals of the force sensor are received and processed. If an error occurs in this case, i.e. in particular if the force weakens, the machine control 10 can react to this and control the machine in a safer state. Two criteria must always be met: the clamping means must not loosen and the workpiece must remain clamped with the desired clamping force.

[0032] For sufficient redundancy, it is sufficient if several microprocessors 22, 23 are involved in the control at each force balance, so that even in the case of a larger number of fastening means 2, 3, more than two microprocessors 22, 23 do not necessarily have to be involved. However, this can nevertheless be done as follows: even in the case of an odd number of fastening means, one fastening means can be controlled, for example, by one microprocessor and two other fastening means by another microprocessor, since at least two microprocessors are involved in the control of the sum of the forces at each fastening means.

[0033] If during operation the microprocessor 22, 23 detects an incorrect force, in particular an excessive force in one of the force sensors 35, 36, or in the event of another critical error, i.e. an error in the signature or identification number of the process data set which is redundantly checked by the microprocessor 22, 23, the microprocessor 22, 23 informs the safety control unit 12 of the machine control 10 of this, which in turn controls the machine to a safer state, in particular by means of a stop signal which stops the machine, thereby avoiding injuries or damage from a workpiece which rotates at high speed but which may become loose in unfavourable conditions.

[0034] Thus, what has been described above is a machine tool in which a connection between the machine and the workpiece is formed such that the security of data communication is improved with respect to the prior art. [Explanation of symbols]

[0035] 1 Fastening device 2 First fastening means 3 Alternative fastening means 4 Workpiece 5 Power supply section 6. Supervision Signals 7 Inductive coupler 10 Machine control section 11 Control unit 12 Safety Control Unit 20 Fastening device control section 21 Control unit 22 First microprocessor 23 Second microprocessor 24 First stop signal 25 Second stop signal 26 First servo motor 27 Another servo motor 28 Control Signals 29 First Servo Controller 30 Different Servo Controllers 29 Status Signals 32 First Displacement Sensor 33 Another Displacement Sensor 34 Displacement Signal 35 First Force Sensor 36 Another Force Sensor

Claims

1. A machine tool having a fixed machine control unit (10) and a rotating fastening device (1), In a machine tool, the machine control unit (10) communicates with a fastening device control unit (20) which rotates with the fastening device (1) via an intermediate connection of a coupling unit (7), the coupling unit (7) enables the machine control unit (10) to connect to the fastening device control unit (20) via data non-contact, the fastening device control unit (20) has a control unit (21) for driving and controlling propulsion means for operating the fastening means (2, 3) of the fastening device (1), the control unit (21) is associated with at least two redundant microprocessors (22, 23), the microprocessors (22, 23) enable independent inspection of process data sets received from the machine control unit (10) via the control unit (21), and / or process data received from process sensors can be used in the process data sets independently and can be transmitted to the machine control unit (10) via the control unit (21), A machine tool characterized in that each of the tightening means (2, 3) is associated with at least one force sensor (35, 36) or tightening signal generator, each of the force sensors (35, 36) or tightening signal generators is data-connected to only one of the microprocessors (22, 23), or a microprocessor (22, 23) is associated with the force sensors (35, 36) or tightening signal generators of multiple tightening means (2, 3), and the force sensors (35, 36) or tightening signal generators of opposing tightening means (2, 3) are associated with different microprocessors (22, 23).

2. The machine tool according to claim 1, characterized in that the propulsion means of the tightening means (2, 3) is a servo motor (26, 27) controlled by a servo controller (29, 30).

3. The machine tool according to claim 1 or 2, characterized in that each of the tightening means (2, 3) is associated with at least one force sensor (35, 36) or tightening signal generator, the force sensors (35, 36) or tightening signal generators of the multiple tightening means (2, 3) are associated with the microprocessors (22, 23), and the force sensors (35, 36) or tightening signal generators of the tightening means (2, 3) having force components acting in opposite directions are associated with different microprocessors (22, 23).

4. The machine tool according to claim 1 or 2, characterized in that the tightening means (2, 3) are associated with displacement sensors (32, 33) that are data-connected to the control unit (21).

5. The machine tool according to claim 1 or 2, characterized in that the coupling device (7) forms an inductive coupling data connection between the machine control unit (10) and the tightening device control unit (20).

6. A method for controlling a machine tool having a fixed machine control unit (10) and a rotating fastening device (1), wherein the machine control unit (10) communicates with a fastening device control unit (20) which rotates with the fastening device (1) via an intermediate connection of a coupling unit (7), the coupling unit (7) enables the machine control unit (10) to data-connect to the fastening device control unit (20) non-contact, the fastening device control unit (20) has a control unit (21) for driving and controlling propulsion means for operating the fastening means (2, 3) of the fastening device (1), and a process dataset transmitted from the machine control unit (10) to the fastening device control unit (20) is independently inspected by two redundant microprocessors (22, 23) and / or the microprocessors (22, 23) use process data received from process sensors in the process dataset independently of each other and transmit it to the machine control unit (10) via the control unit (21), A method characterized in that each of the fastening means (2, 3) is associated with at least one force sensor (35, 36) or fastening signal generator, and process data sets transmitted from the force sensors (35, 36) or fastening signal generators are inspected by only one of the microprocessors (22, 23), or the microprocessors (22, 23) are associated with different microprocessors (22, 23) in order to inspect the process data sets transmitted by the force sensors (35, 36) or fastening signal generators of multiple fastening means (2, 3), and by the force sensors (35, 36) or fastening signal generators of opposing fastening means (2, 3).

7. The method according to claim 6, characterized in that the process dataset has a calculated signature and / or a sequential identification number.

8. The method according to claim 6 or 7, characterized in that the process dataset for each propulsion means output by the machine control unit (10) includes an STO signal (Safe-Torque-Off-Signal), and the motion of the corresponding propulsion means is enabled only when the signal corresponds to an enable signal.

9. The method according to claim 7, characterized in that when an STO signal is received, or in the event of an error in the signature or in the event of a discrepancy with the expected identification number, the microprocessors (22, 23) independently output a stop signal to the tightening means (2, 3).

10. The method according to claim 6 or 7, characterized in that sensor data is transmitted from force sensors (35, 36) or tightening signal generators to the microprocessors (22, 23), and the sensor data is used in a process dataset to be transmitted to the machine control unit (10).

11. The method according to claim 10, characterized in that each microprocessor (22, 23) creates its own process dataset and transmits it to the machine control unit (10) via the control unit (21).

12. The method according to claim 10, characterized in that each microprocessor (22, 23) writes the process data received by the microprocessors (22, 23) into a cyclic process dataset, and the control unit (21) transmits the cyclic process dataset to the machine control unit (10).

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