METHOD FOR MONITORING AT LEAST ONE MACHINE TOOL AND PRODUCTION SYSTEM

Abstract

A method for monitoring at least one machine tool (12) featuring the steps (a) real-time detection of time-dependent measurement data (M.sub.i) characterising a production process running on the machine tool (12), (b) provision of the measurement data (M.sub.i) with a time stamp which encodes a time (t.sub.j) at which a respective measurement data (Mi) was detected, such that measurement results (M.sub.i(t.sub.j)) are obtained, (c) transmission of the measurement results (M.sub.i(t.sub.j)) via a non-real-time-capable data bus (26) to an evaluation unit (28), (d) calculation of at least one command (B) from the measurement results by means of the evaluation unit, (e) transmission of the at least one command (B) via the data bus (26) and (f) monitoring of the production process in real-time by means of a programme that contains the command (B).

Claims

1. A method for monitoring at least one machine tool, comprising: (a) detecting in real-time time-dependent measurement data characterizing a production process running on the machine tool, (b) providing the time-dependent measurement data with a time stamp which encodes a time at which a respective measurement data was detected, (c) transmitting the time stamped. time-dependent measurement data as measurement results by a non-real-time-capable data bus to an evaluation unit, (d) calculating, using the evaluation unit, at least one command from the measurement results, (e) transmitting the at least one command via the data bus to a machine controller; and (f) monitoring or adjusting the production process in real-time by executing a program on said machine controller that implements the at least one command.

2. The method according to claim 1, further comprising: determining a reaction time of the data bus, and if the reaction time exceeds a pre-set reaction time threshold value, limiting a processing speed value that encodes a speed at which the program is executed on the machine tool to a maximum processing speed value.

3. The method according to claim 1 wherein the program that implements the at least one command is used for monitoring the production process during which the measurement data was detected and from which the at least one command was calculated.

4. The method according to claim 1 wherein a maximum response time between transmission of the measurement results to the evaluation unit and a receipt of the at last one command transmitted via the data bus is no more than 1 second.

5. The method according to claim 1 wherein a processing time between detecting the measurement data and receipt of the at least one command transmitted via the data bus, wherein this at least one command was calculated using the measurement data, is a maximum of 60 seconds.

6. The method according to claim I wherein the at least one command is a condition command which encodes when and/or to what extent a processing speed value is to be adjusted, wherein the processing speed value encodes a speed at which a machine tool is operated, and wherein the at least one command encodes at least one parameter which describes a dependency of one adjustment of the processing speed value of a machine parameter.

7. The method according to claim 1 wherein the at least one command is a condition command and encodes production process stops if a process parameter, which describes a process force, exceeds a process parameter maximum value encoded in the at least one command.

8. The method according to claim 1 wherein the at least one command is a condition command and encodes production process stops if a spindle parameter, which describes a spindle torque of a spindle of the machine tool, exceeds a maximum value encoded in the command.

9. The method according to claim 1 wherein the at least one command is a condition command and encodes production process stops if the spindle parameter does not reach a minimum value encoded in the command for a pre-determined period.

10. The method according to claim 1, wherein at least two machine tool monitoring devices are connected to the evaluation unit via the data bus, wherein each machine tool monitoring device detects time-dependent measurement data of a machine tool, and wherein the evaluation unit calculates commands for each of the at least two machine tool monitoring devices from the respective measurement results (M.sub.i(t.sub.j)).

11. A production system, comprising: (i) a first machine tool which comprises a first real-time-capable machine controller, (ii) at least a second machine tool which comprises a second real-time-capable machine controller, (iii) an evaluation unit, (iv) a non-real-time-capable data bus which connects the first machine tool and the at least one second machine tool to the evaluation unit, (v) wherein the first machine tool and the at least a second machine tool are installed to automatically (a) detect time-dependent measurement data characterizing a production process, (b) provide the measurement data with a time stamp which encodes a time at which a respective measurement data was detected, such that measurement results are obtained, and (c) transmit the measurement results via the data bus to the evaluation unit, (vi) wherein the evaluation unit is configured to automatically (a) calculate at least one command for one or more of the first machine tool and the at least a second machine tool from the respective measurement results and (b) transmit the at least one command via the data bus to one or more of the first machine tool and the at least a second machine tool, (vii) wherein the first machine tool and the at least a second machine tool are configured to automatically (a) receive the at least one command from the evaluation unit, (b) monitor the production process using a program that contains the at least one command, and (viii) wherein the first machine tool and the at least one second machine tool are configured to automatically (c) determine a reaction time of the data bus, and (d) if the reaction time () exceeds a pre-set reaction time threshold value (.sub.S), limit a processing speed value to a maximum processing speed value.

12. The production device according to claim 11, further comprising (i) a first non-real-time-capable machine tool monitoring device that is connected to a first machine controller (18.1), a second non-real-time-capable machine tool monitoring device that is connected to a second machine controller (18.2), (iii) wherein the first and second non-real-time-capable machine tool monitoring devices are each is configured to automatically (a) detect measurement results from measurement data and time stamps from the first machine controller, (b) transmit the measurement results to the evaluation unit, (c) receive the at least one command from the evaluation unit, and (d) transmit the at least one command to the machine controller.

13. The production system according to claim 11 wherein (i) the first machine controller is configured to automatically (a) identify measurement results from measurement data and time stamps, (b) transmit the measurement results to the evaluation unit, (c) receive the at least one command from the evaluation unit, and (d) monitor the production process of a first machine tool using a program which executes the at least one command, and/or (ii) the first machine controller is configured to automatically (a) identify measurement results from measurement data and time stamps, (b) transmit the measurement results to the evaluation unit, (c) receive the at least one second command from the evaluation unit, and (d) monitor the production process of the at least a second machine tool using a program which executes the second command.

14. A machine tool monitoring device, comprising: (a) a first interface for connecting to a real-time-capable machine controller of a machine tool, (b) a second interface for a non-real-time-capable data bus for connecting to an evaluation unit, (c) wherein the machine tool monitoring device is configured to automatically execute the following steps: (i) detection of time-dependent measurement data from the machine controller, the measurement data characterising a production process running on the machine tool, (ii) provision of the measurement data with a time stamp which encodes a time at which a respective measurement data was detected, such that measurement results are obtained, and (iii) transmission of the measurement results via the data bus to the evaluation unit, (iv) receipt of the at least one command from the evaluation unit, (v) monitoring of the production process using a program that contains the at least one command, (vi) determination of a reaction time of the data bus, and (vii) if the reaction time exceeds a pre-set reaction threshold value, limitation of a processing speed value to a maximum processing speed value.

15. The method of claim 6 wherein the at least one parameter is or includes machine torque.

16. The method of claim 10 wherein the at least two machine tool monitoring devices includes at least four machine tool monitoring devices.

Description

[0040] In the following, the invention will be explained in more detail by way of the attached drawings. They show

[0041] FIG. 1 a schematic view of a production system according to the invention for conducting a method according to the invention and

[0042] FIG. 2 a diagram depicting the operational sequence of a method according to the invention,

[0043] FIG. 3 a schematic view of a second embodiment of a production system according to the invention for conducting a method according to the invention.

[0044] FIG. 1 shows a production system 10 according to the invention with a first machine tool 12.1 and at least a second machine tool 12.2 as well as a first machine tool monitoring device 14.1 in the form of a first operating panel computer and a second machine tool monitoring device 14.2 in the form of a second operating panel computer. The two machine tool monitoring devices 14 are connected to a respective machine controller 18.1 or 18.2 via respective data connections 16.1, 16.2, for instance by means of cables and/or plug connections.

[0045] The machine controller 18.i (i=1, . . . N; N: number of machine tools in the production system) controls the respective machine tool 12.i such that it executes a pre-set production programme. The operating panel computers 14.i are not real-time-capable. In particular, an editor for a production programme runs on these computers. Upon provision of the production programme it is transmitted to the respective machine controller 18.1 or 18.2 and carried out in real-time.

[0046] The machine controllers 18.i record measurement data at regular intervals t.sub.j and combine these with a time stamp, thereby producing measurement results M.sub.j(t.sub.j) (j=1, 2, . . . ). The machine tool monitoring devices 14.i communicate with the respective machine controllers 18.i in such a way that they read measurement results M.sub.j(t.sub.j) (j=1, 2, . . . ) from the machine controller 18.9 at regular intervals t.sub.j. The measurement values M.sub.j may refer to outputs L.sub.s of one or several drive motors, the torques M.sub.A,j produced by the motors or the correlating values, such as the armature currents I.sub.j.

[0047] The first machine tool 12.1 preferably has at least one sensor 20.1, such as an acceleration sensor, which is arranged on a tool housing 22.1. In the present illustrative case, the machine tool 12.1 refers to a milling machine and a cutter 24.1 is fixed to the tool housing 22.1.

[0048] To ensure that all machine tools 12.i have the same machining time, it is advantageous if the machine tool monitoring devices 14.i detect a network time at regular intervals, this network time being transmitted by the data bus 26 for example, and transmit the network time to the machine controllers 18.i. However, it is also possible that the machining times of the machine tools 12.i vary from one another. Alternativelyalthough technically more complexthe machine tool monitoring device 14 has a clock that measures the absolute time t.sub.a,j.

[0049] The machine tool monitoring devices 14.i are connected to an evaluation unit 28 by means of a data bus 26. A distance between the evaluation unit 28 and the machine tools 12.i is preferably at least 10 metres, in particular the evaluation unit 28 is arranged in a different control cabinet to the controller(s) of the machine tools 12.1. It is possible and represents a preferred embodiment that the evaluation unit 28 is connected to the internet via an interface 30. In other words, the evaluation unit 28 is configured to communicate in an HTML or XML format.

[0050] The evaluation unit 28 detects the measurement data M.sub.i,j=M.sub.i,j(t.sub.Mi,j), which are provided with the respective time stamps t.sub.Mi,j, namely the respective j-th machining time M.sub.i of the i-th machine tool.

[0051] For each machine tool 12.i, an individual evaluation of the measurement data M.sub.i,j runs on the evaluation unit 28; in particular, an individual programme runs which evaluates the measurement data M.sub.i,j. In particular, the evaluation unit 28 is designed to calculate threshold values M.sub.S or target values M.sub.Soll for the recorded measurement data M. For instance, if a drive torque M.sub.A of a feed axis is detected, a threshold value M.sub.S in the form of a threshold drive torque M.sub.S,Arm is calculated. This threshold value M.sub.S is then sent back to the machine tool monitoring device 14.1 via the data bus 26.

[0052] The threshold value M.sub.S refers to a parameter which is completed with a pre-set raw command in the machine tool monitoring device 14.1 or the machine controller 18.1 to become the command which triggers an action when this threshold value M.sub.S is exceeded. For example, an override value A, which may also be referred to as a processing speed value, is reduced by ax % points if the threshold value M.sub.S is exceeded by x %. The parameter a is a gain factor.

[0053] Alternatively or additionally, the evaluation unit 28 calculates a target value, such as a target motor torque M.sub.Soll and the gain factor a. The machine tool monitoring device 14 or the machine controller 18 enters the two parameters in the monitoring programme and calculates the value for the processing speed as A=100%+a(M.sub.SM.sub.j(t))/M.sub.S.

[0054] The machine tool monitoring device 14 sends a test message at regular intervals, for instance once per second, to the evaluation unit 28; the evaluation unit 28 then sends control information back to it. The machine tool monitoring device 14.1 then identifies a reaction time and if the reaction time is above a pre-set threshold value .sub.s once or several times, the machine tool monitoring device 14 reduces the processing speed value A to a pre-set maximum processing speed value A.sub.max, for example to 100%. In other words, it is then possible that this processing speed value A is smaller than A.sub.max, but it cannot exceed A.sub.max. This ensures that the machine tool monitoring device 14.1 does not bring the machine tool into a state which could compromise it.

[0055] According to a preferred embodiment, the machine controller 18.i is programmed in such a way that if the threshold value .sub.s is exceeded, the production programme is run in a safety mode. It is possible for an operator to set and/or determine an override value in this safety mode such that the execution of the current monitoring programme continues. Alternatively or additionally, the machine tool can be shut down, meaning that production is interrupted.

[0056] FIG. 2 schematically shows that the evaluation unit 28 is not connected to the machine controller 18.i via the data bus 26 that is not real-time-capable or not operated in real-time. Of course, it is possible for all or only one part of the machine tools 12 of a production system 10 to be connected to the evaluation unit 28. The machine tool monitoring devices 14.i are dispensable if the respective machine controller 18.i comprises a data bus interface. The evaluation unit 28 is preferably physically separate from the machine controllers 18.i

[0057] The data bus 26 may be, for example, a fieldbus in accordance with IEC 61158 or a non-real-time-capable ethernet bus.

[0058] FIG. 3 schematically depicts a machine tool monitoring device 14 according to the invention which is designed to be separate from the operating panel computer and with a first interface 32 that is connected to the machine controller 18. The machine toll monitoring device 14 reads the measurement data M from the machine controller 18 via the first interface 32, provides them with a time stamp and continuously sends them to the evaluation unit 28.

[0059] The machine tool monitoring device 14 also has a second interface 34, by means of which it is connected to the evaluation unit 28. A monitoring programme runs on the machine tool monitoring device 14 that is capable of giving commands to the machine controller 18. Commands from the evaluation unit 28 are entered into the monitoring programme and executed. For instance, the evaluation unit 28 continuously calculates a maximum value and a minimum value for a spindle parameter in the form of a spindle torque which acts on a spindle 36. If the measurement value M identified exceeds the maximum value, the machine tool monitoring device 14 controls the machine controller in such a way that it decreases the processing speed at which the production programme is conducted. The spindle torque reduces as a result. The reduction in the processing speed may go down to zero, thereby stopping the processing.

[0060] It is also possible but not necessary for the command, which is sent by the evaluation unit 28, to encode a maximum force that acts on one of the machine axis of the machine tool 12. This may be determined by way of the armature current of the drive motor, for instance.

[0061] As shown in FIG. 3, since the production system 10 may comprise two or more machine tools 12 but only requires one evaluation unit 28, the capital expenditure required to monitor the machine tools decreases.

REFERENCE LIST

[0062] 10 production system [0063] 12 machine tool [0064] 14 machine tool monitoring device, operating panel computer [0065] 16 data connection [0066] 18 machine controller [0067] 20 sensor [0068] 22 tool housing [0069] 24 cutter [0070] 26 data bus [0071] 28 evaluation unit [0072] 30 interface [0073] 32 first interface [0074] 34 second interface [0075] 36 spindle [0076] A processing speed value (=override value) [0077] a gain factor [0078] i running index (machine tool number) [0079] j running index (time number) [0080] M measurement data [0081] M.sub.A drive torque [0082] M.sub.S threshold value [0083] N number of machine tools [0084] t.sub.M machining time [0085] t.sub.a absolute time [0086] reaction time