MACHINE TOOL AND METHOD FOR CONTROLLING A MACHINE TOOL

Abstract

It is already know from the prior art to provide machine tools with a clamping device, in which a portion of the control is transferred to the clamping device. This simplifies the connection to the available machine control and allows a simplified coupling of the clamping device to the machine tool. However, in spite of the inductive coupling between the machine control and the clamping device control, it is not ensured that process data sets reach their intended destination.

This situation is addressed by the present invention in that a clamping device control is allocated to the clamping device, two redundant microprocessors are included, which analyze received process data sets independently of each other and, in the case of an error, transfer the clamping device into a safe state.

Claims

1. A machine tool with a stationary machine control (10) and a rotating clamping device (1), wherein the machine control (10) communicates with a clamping device control (20) that is rotating with the clamping device (1) with the intermediate connection of a coupling unit (7), wherein the coupling unit (7) provides a contactless data connection from the machine control (10) to the clamping device control (20), wherein the clamping device control (20) comprises a control unit (21) for actuating advancement means for activating clamping means (2, 3) of the clamping device (1) and at least two redundant microprocessors (22, 23) are allocated to the control unit (21), via which process data sets received by the machine control (10) via the control unit (21) can be verified independently of each other and/or process data received by process sensors can be used independently of each other in process data sets and can be transmitted via the control unit (21) to the machine control (10), characterized in that respectively at least one force sensor (35, 36) or clamping signal transmitter is allocated either to the clamping means (2, 3) and they are respectively data-connected solely with one of the microprocessors (22, 23), or the force sensors (35, 36) or clamping signal transmitters of several clamping means (2, 3) are allocated to the microprocessors (22, 23), and the force sensors (35, 36) or clamping signal transmitters of opposing clamping means (2, 3) are allocated to different microprocessors (22, 23).

2. The machine tool according to claim 1, characterized in that the advancement means of the clamping means (2, 3) are servomotors (26, 27), which are controlled with the aid of servocontrollers (29, 30).

3. The machine tool according to claim 1, characterized in that respectively at least one force sensor (35, 36) or clamping signal transmitter is allocated to the clamping means (2, 3) and the force sensors (35, 36) or clamping signal transmitters of several clamping means (2, 3) are allocated to the microprocessors (22, 23), wherein the force sensors (35, 36) or clamping signal transmitters of clamping means (2, 3) are allocated to different microprocessors (22, 23) with oppositely acting force components.

4. The machine tool according to claim 1, characterized in that path sensors (32, 33) are allocated to the clamping means (2, 3), which sensors are data-connected to control unit (21).

5. The machine tool according to claim 1, characterized in that an inductively coupled data connection is established between the machine control (10) and the clamping device control (20) via the coupling device (7).

6. A method for controlling a machine tool with a stationary machine control (10) and a rotating clamping device (1), wherein the machine control (10) communicates with a clamping device control (20) that is rotating with the clamping device (1) with the intermediate connection of a coupling unit (7), wherein the coupling unit (7) provides a contactless data connection from the machine control (10) to the clamping device control (20), and the clamping device control (20) comprises a control unit (21) for actuating advancement means for activating clamping means (2, 3) of the clamping device (1), and process data sets sent by the machine control (10) to the clamping device control (20) are independently checked by two redundant microprocessors (22, 23) and/or the microprocessors (22, 23) use process data received from process sensors independently of each other in process data sets and transmit to the machine control (10) via the control unit (21), characterized in that that respectively at least one force sensor (35, 36) or clamping signal transmitter is allocated either to the clamping means (2, 3), and process data sets sent therefrom are respectively checked solely by one of the microprocessors (22, 23), or the force sensors (35, 36) or clamping signal transmitters of several clamping means (2, 3) are allocated to the microprocessors (22, 23) and the force sensors (35, 36) or clamping signal transmitters of opposing clamping means (2, 3) are allocated to different microprocessors (22, 23) for checking the process data sets that are sent.

7. The method according to claim 6, characterized in that process data sets comprise a calculated signature and/or a sequential identification number.

8. The method according to claim 6, characterized in that process data sets output by the machine control (10) for each advancement means includes a STO signal (safe torque off signal), wherein a movement of the relevant advancement means is released only if the signal corresponds to a release signal.

9. The method according to claim 7, characterized in that, in the event of the receipt of a STO signal or in the case of an error in a signature or a deviation from an anticipated identification number, the microprocessors (22, 23) output independently of one other a stop signal to the clamping means (2, 3).

10. The method according to claim 6, characterized in that sensor data from force sensors (35, 36) or clamping signal transmitters is transmitted to the microprocessors (22, 23) and said sensor data is used in process data sets for dispatch to the machine control (10).

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

12. The method according to claim 10, characterized in that each microprocessor (22, 23) enters the process data that it receives in a circulating process data set and the control unit (21) transmits the circulating process data set to the machine control (10).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The invention described in the foregoing will be explained in greater detail in the following on basis of an exemplary embodiment, which shows:

[0026] FIG. 1 A schematic representation of a machine tool with a clamping device and a machine control, which is connected via a coupler to a clamping device control allocated to the clamping device, as well as

[0027] FIG. 2 A more detailed schematic representation of the machine tool with the details of the clamping device control and the machine control.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] In a schematic representation, FIG. 1 shows a clamping device 1, which comprises two pairs of clamping means 2, 3, by means of which a workpiece 4 is held all around offset by 90 in each case. Via an inductive coupler 7, a clamping device control 20 of the clamping device 1 communicates with a machine control 10 of the machine tool, for which a control unit 11, a safety control unit 12, and a power supply 5 are shown in detail in this case. Control units 11 and 12, as well as a control unit 21 of the clamping device control 20, can be designed in particular as a programmable logic controller (PLC).

[0029] Whereas on the part of the control unit 11, adjustment signals, for example based on a running program or based on user settings on an interface that is not shown here, are output to the clamping device control 20, the safety control unit 12 is available mainly or exclusively for the communication of safety-relevant signals. A part of this is in particular the transmission of a force signal that indicates the force which with the clamping means 2, 3 grip a workpiece. To improve the reliability of the data transmission via the inductive coupler 7, the invention provides that a redundant monitoring of the signals, which are transmitted to the control unit 21 of the clamping device control 20, takes place with the aid of redundantly designed microprocessors 22, 23 in the clamping device control 20. A transfer via the inductive coupler 7 constitutes a normal, simple communication channel and is not secure to begin with. The analysis of the signals that pass through the inductive coupler 7 by two independent microprocessors 22, 23 therefore helps to improve the reliability of the data transmission.

[0030] As a supplement to the simple representation in FIG. 1, this situation is reflected with a greater degree of detail in FIG. 2, wherein individual subordinate aspects have been dispensed with.

[0031] Using the example of two clamping means 2, 3, it is evident that a workpiece 4 can be centered by said clamping means. To this end, the clamping means 2, 3 can be moved with the aid of servomotors 26, 27, which are monitored with the aid of path sensors 32, 33. The control takes place with the aid of a control unit 21 of the clamping device control 20 using a CAN bus. This provides a data connection of the servocontrollers 29, 30 to the control unit 21. While the control instructions come from the machine control 10, and in this case in detail from a control unit 11, the direct actuation of the servocontrollers 29, 30 and, via this, the actuation of the servomotors 26, 27 run within the clamping device control 20. As already depicted FIG. 1, the clamping device control 20 and machine control 10 are data-connected via an inductive coupler 7.

[0032] Concretely, adjustment commands based on corresponding programming are transferred first of all to a control unit 11 of machine control 10. Said control unit for its part sends adjustment commands via the inductive coupler 7 to the control unit 21 of the clamping device control 20. The control unit 21 thereupon causes the clamping means 2, 3 to close for example, in other words, to move towards the workpiece 4. Corresponding control signals 28 are transmitted to the two servocontrollers 29, 30, which for their part correspondingly actuate the servomotors 26, 27 in turn. The path sensors 32, 33 monitor the situation of the respectively allocated clamping means 2, 3 and report their positions back to the control unit 21.

[0033] At the same time, however, the force acting on the clamping means 2, 3 is recorded. For this purpose, a force sensor 35, 36 is allocated to each clamping means 2, 3, which force sensor communicates with a microprocessor 22, 23 and transmits status signals 31 to it. In order to achieve an adequate level of redundancy in data collection, a first force sensor 35 allocated to a first clamping means 2 communicates with a first microprocessor 22, while an additional force sensor 36 that is allocated to an additional clamping means 3 communicates with a second microprocessor 23. The microprocessors 22, 23 receive the force signals and enter them into a process data set, which is filled by the microprocessors 22, 23 in a circulating procedure and then transmitted by the control unit 21 to the machine control 10. There in particular the safety control unit 12 receives and processes the signals from the force sensors. If an error occurs in the process, i.e., in particular a force that is decreasing, the machine control 10 is able to react to this and regulate the machine into a safe state. Two criteria must always be satisfied, that the clamping means may not loosen and the workpiece remains clamped with the target clamping force.

[0034] For an adequate level of redundancy, it suffices if several microprocessors 22, 23 are involved in control in the case of every force equilibrium so that, even if there is a greater number of clamping means 2, 3, more than two microprocessors 22, 23 do not necessarily need to be involved. However, this can be implemented in this way nevertheless. Even in the case of an uneven number of clamping means, it is possible for instance to control one clamping means from one microprocessor, and the other two clamping means from the other microprocessor, since at least two microprocessors are involved in controlling the force total at every clamping means.

[0035] During operation, if a microprocessor 22, 23 detects an incorrect force, in particular too high a force, at a force sensor 35, 36, or if other critical malfunctions occur, namely an error in a signature or an identification number of a process data set, which are redundantly checked by the microprocessors 22, 23, then the microprocessor 22, 23 report this to the safety control unit 12 of the machine control 10, which regulates the machine into a safe state, in particular using a stop signal, which stops the machine in order to prevent injury or damage based on the rapidly rotating workpiece, which in the most unfavorable case is now loosened.

[0036] Therefore, the foregoing describes a machine tool in which a coupling between the machine and tool is designed in such a way that the reliability of data communication is improved with respect to the prior art.

LIST OF REFERENCE NUMBERS

[0037] 1 Clamping device [0038] 2 First clamping means [0039] 3 Additional clamping means [0040] 4 Workpiece [0041] 5 Power supply [0042] 6 Monitoring signal [0043] 7 Inductive coupler [0044] 10 Machine control [0045] 11 Control unit [0046] 12 Safety control unit [0047] 20 Clamping device control [0048] 21 Control unit [0049] 22 First microprocessor [0050] 23 Second microprocessor [0051] 24 First stop signal [0052] 25 Second stop signal [0053] 26 First servomotor [0054] 27 Additional servomotor [0055] 28 Control signal [0056] 29 First servocontroller [0057] 30 Additional servocontroller [0058] 31 Status signal [0059] 32 First path sensor [0060] 33 Additional path sensor [0061] 34 Displacement signal [0062] 35 First force sensor [0063] 36 Additional force sensor