Method for monitoring a change in a compressed air flow due to leaks on a machine tool

Abstract

The present invention relates to a method for monitoring a change in the compressed air flow due to leaks on a machine tool (200) and a method for teaching a machine-specific limit value pattern for monitoring the change in the compressed air flow. The invention further relates to a computing unit (200) and a computer program for carrying out the method, as well as to a machine tool (200).

Description

[0001] Method for monitoring a change in compressed air flow due to leaks on a machine tool

[0002] The present invention relates to a method for monitoring a change in compressed air flow due to leaks in a machine tool and a method for learning a machine-specific limit value pattern for monitoring the change in compressed air flow. Furthermore, the invention relates to a computing unit and a computer program for implementing the method, as well as to a machine tool.

[0003] Background of the invention

[0004] Machine tools of various types require a compressed air supply to perform all the functions required within their manufacturing processes. For example, a modern turning-milling machine contains more than fifty components that must be supplied with compressed air. This includes both components that require continuous compressed air, such as sealing a cavity with so-called "sealing air," and components that are permanently integrated into the compressed air supply but are only temporarily operated by compressed air, such as actuators for tool changes, which can include pneumatic switching valves and air cylinders. Compressed air can also be used to clean tools and machine surfaces, and to cool tools during the machining process.

[0005] To provide the compressed air supply, production halls in which machine tools are operated can be equipped with a compressed air network comprising one or more compressors and compressed air storage units. Providing compressed air in such a compressed air network using compressors involves considerable energy consumption and thus corresponding costs. Therefore, it is desirable to prevent leaks in the compressed air network and at the machine tools supplied by it. To ensure this, it is necessary to monitor changes in the compressed air flow to the machine tools due to leaks.

[0006] Currently, machine tool operators have very limited options for monitoring compressed air leaks, such as acoustic testing using a stethoscope when the machine is switched off. Therefore, efforts are being made to use artificial intelligence (AI) to detect compressed air leaks on machine tools. However, this requires the behavior of a machine tool to be trained over a long period of time (possibly several days), which incurs considerable costs for the machine tool operator due to downtime. In addition, if a component on the machine tool is replaced, the entire training process must be repeated. Furthermore, the accuracy achievable using AI is limited because it lacks any technical information about the machine tool, meaning that even minor changes in the boundary conditions under which the machine tool is operated can lead to a falsified result.

[0007] An object of the present invention is to (continuously) monitor changes in a compressed air flow due to leaks in a machine tool and, for example, to reliably detect any leaks in pneumatic elements in the machine tool in all operating states of the machine.

[0008] To solve these problems, the features of the independent claims are proposed. Advantageous embodiments can be found in the dependent claims.

[0009] A method is proposed for monitoring a change in compressed air flow due to leaks on a machine tool that includes a controller and a sensor. The machine tool can be a lathe, a milling machine, a turning-milling machine, a cutting or grinding machine, a machining center, or any other type of machine tool that includes elements supplied with compressed air (actuators, seals, purge and cooling air, etc.).

[0010] The sensor can, in particular, be a flow sensor. This can, for example, be a calorimetric / thermal flow sensor that determines a compressed air mass flow based on the cooling of a heated element by passing compressed air, and determines a compressed air volume flow by additionally recording its pressure and temperature. The flow sensor can, in particular, measure the compressed air volume flow in accordance with the ISO standards ISO 6358 / ISO 8778.

[0011] Determine the flow rate in "standard liters" and convert a currently determined compressed air volume flow to the reference values ​​specified in this standard (air pressure = 1 bar, air temperature = 20 °C, and air humidity = 65%). For this purpose, the flow sensor can also contain means for measuring air humidity. When using a thermal flow sensor, it should also be noted that its measurement accuracy is affected by particles as well as water and oil droplets in the compressed air. To account for these influences, a reference measurement can be performed, for example, with a predetermined compressed air quality.

[0012] The sensor can be connected to the machine tool controller using the industrial communication standard IO-Link, for example. Any other communication connection between the sensor and the machine tool controller is also possible.

[0013] In the method, a plurality of predetermined operating states are set on the machine tool. This can be done, in particular, by the machine tool's control system, which can set the predetermined operating states according to a predefined program. In each of these operating states, a compressed air flow of the machine tool can be measured / learned and stored, for example, as a reference state ("fingerprint") of the machine tool. This can be done, for example, upon delivery of a machine tool by a manufacturer and / or upon commissioning of the machine tool by an operator, as explained in more detail below.

[0014] According to one embodiment, a number of the plurality of predetermined operating states can be dependent on a type and / or equipment of the machine tool. In other words, the number of operating states to be set depends on the combinations of compressed air consumers depending on the type and / or equipment of the machine tool. Thus, the operating states can be individually adapted for each machine tool, which allows the time for measuring the individual operating states to be optimized. For example, the number of operating states can be between ten and twenty.

[0015] The sensor measures a compressed air flow through the machine tool in "standard liters" according to ISO 6358 / ISO 8778 in each of the plurality of predetermined operating states. According to one embodiment, each of the plurality of predetermined operating states can comprise a predetermined combination of activated compressed air consumers of the machine tool. The predetermined combination of activated compressed air consumers can vary, in particular, depending on the type and design / equipment of the machine tool. In other words, depending on the machine tool's equipment with pneumatic elements, different combinations of compressed air consumers can occur, so that both different operating states and different predetermined combinations of active compressed air consumers in the individual operating states can be defined for different machine tools.

[0016] Each predetermined combination of active compressed air consumers can, for example, be assigned to a process step in a manufacturing process of the machine tool. For this purpose, all relevant manufacturing process steps of the machine can be identified in advance, and the compressed air consumers involved in the individual process steps can be determined. A process step with the compressed air consumers involved can therefore represent an operating state. The process steps can, for example, include measuring the tools, in which compressed air can be used to clean the tools in order to, for example, precisely determine the surface contours of the tools using a laser (operating state “measure tool”). In addition, a tool and / or pallet change in the machine tool, in which one or more pneumatically operated actuators can be used, can represent a process step orrepresent an operating state (operating state “tool change” or “pallet change”).

[0017] It is clear that a manufacturing process can involve a multitude of process steps. By knowing the combination of compressed air consumers occurring in the individual process steps in the machine tool, all relevant operating states can be captured, and combinations of compressed air consumers that do not occur or only occur very rarely during a manufacturing process can be neglected. In other words, the multitude of predetermined operating states can, in particular, include process steps that occur frequently in different manufacturing processes (e.g., tool / pallet changes, tool measurement, etc.), and the combinations of compressed air consumers used in these process steps can be defined as operating states for each process step.A switched-off state and / or a stand-by mode of the machine tool can also represent an operating state in which a compressed air flow through the machine tool is detected by the sensor.

[0018] Based on the recorded compressed air flow for each of the multitude of predetermined operating states, at least one limit value for the compressed air flow, e.g. for the compressed air volume flow in standard liters according to ISO 6358 / ISO 8778, is then defined. For example, in the “tool change” operating state, in which, for example, one or more actuators can be pneumatically operated in order to, for example, open and / or close access to a tool magazine, the compressed air flow (compressed air volume flow) through the machine tool can be continuously measured and, for example, a maximum value of the recorded flow curve during the tool change can be defined as a limit value. Alternatively or additionally, a value greater than the maximum value of the recorded flow curve can be defined as the limit value. In this case, for example, a predetermined value can be added to the recorded maximum value in order to, for example, take measurement tolerances of the sensor into account.It is also possible to define multiple limits for the compressed air flow. For example, a maximum value of the recorded flow curve in an operating state can be defined as the first limit, and a value greater than the recorded maximum value can be defined as the second limit.

[0019] According to one embodiment, the at least one limit value for each of the plurality of predetermined operating states can be stored in the control system of the machine tool. In this way, a typical compressed air flow rate can be recorded for each operating state of the machine tool as a so-called "fingerprint" of the machine, and a resulting limit value can be stored.

[0020] Once a limit value has been defined for each of the numerous operating states as described above, it is monitored during operation of the machine tool, and limit violations are detected. In particular, measures can be initiated whenever a limit violation is detected, which are described in more detail below in connection with embodiments of the invention. In this context, it is also possible, for example, to specifically select operating states in which limit violations or anomalies occurred and to perform comparisons with the recorded "fingerprint" only in these operating states. This offers the advantage of enabling rapid diagnosis of the entire machine.

[0021] The predetermined operating states arise during the operation of the machine tool from the process steps required to produce a specific workpiece. In other words, the operation of the machine tool comprises several predetermined operating states, for each of which a limit value for the compressed air flow has been defined, which can then be monitored during operation.

[0022] According to one embodiment, a period of a switching process from a first operating state to a second operating state can be disregarded when determining the at least one limit value. In other words, the operating states of the machine tool can, in particular, be constant phases in the operation of the machine tool. This can prevent short-term peaks in the compressed air flow, which can occur during a switch from one operating state to another, from leading to a limit value being exceeded.

[0023] According to one embodiment, the monitoring of the at least one limit value in each of the plurality of predetermined operating states can occur by comparing an actual compressed air flow with the at least one stored limit value. For this purpose, values ​​of the actual compressed air flow can be detected by the sensor and then filtered. The detection of the actual compressed air flow can occur in a predetermined time frame, e.g., with a measurement frequency of 4 Hz. Filtering the measured values ​​can, in particular, serve to suppress peaks in the actual compressed air flow during a switching process from one operating state to another. For this purpose, an average filter, a median filter, or a Gaussian filter can be used, for example.

[0024] When recording the actual compressed air flow, the pressure, temperature, and humidity of the actual compressed air flow can also be measured. This allows the actual compressed air flow to be converted to a flow rate in standard liters according to ISO 6358 / ISO 8778 before being compared with the stored limit value.

[0025] According to one embodiment, a warning can be issued if the at least one specified limit value is exceeded in at least one of the plurality of predetermined operating states. Each warning can also be saved in a log. The log can contain information regarding the time of the warning, an operating state at the time of the warning, a value of the actual compressed air flow that led to the warning, etc. Based on the log, for example, it is possible to deduce the cause of the warning and detect a leak in an affected compressed air consumer. If, for example, a warning occurs during the “tool change” operating state, it can be deduced from this that there is a leak in the pneumatics in the area of ​​the tool changer. Based on the actual compressed air flow measured at the time of the warning, it is possible toA pneumatic element responsible for the leak can be further narrowed down. Additionally or alternatively, a direct (e.g., automatic) control of the machine tool can be implemented to control the compressed air circuit, in particular to reduce or shut off the compressed air.

[0026] According to one embodiment, at least one loss value can be determined based on a difference between the actual compressed air flow and the at least one limit value if the actual compressed air flow exceeds the at least one limit value. For example, the loss value can be a compressed air volume caused by leakage, which is determined by integrating the difference between the actual compressed air flow and the limit value over time if this assumes a positive value. A drive energy consumed for the lost compressed air volume and / or costs for providing this drive energy can be determined as a further loss value. According to one embodiment, the actual compressed air flow, the at least one limit value and the at least one loss value can be displayed on a display unit of the controller.For example, the actual compressed air flow can be displayed as a continuous curve over time compared to at least one operating-state-dependent limit value. The loss values ​​in the form of compressed air volume, drive energy, and / or costs can be presented as numerical values, e.g., in tabular form and / or as bar chart(s).

[0027] The display can, in particular, be located directly on the machine tool. Alternatively or additionally, the display unit can be located remotely from the machine tool. For example, display units for displaying the above-mentioned values ​​for a plurality of machine tools can be mounted at a central location in a production facility in order to simultaneously monitor changes in the compressed air flow due to leaks in the plurality of machine tools. Furthermore, the control system of one or more machine tools can be accessed, for example, using an external processing unit outside of production, and the above-mentioned values ​​can be displayed on a display unit of this processing unit.

[0028] According to one embodiment, the plurality of predetermined operating states can be set in a predetermined sequence, and a profile of the detected compressed air flow according to the predetermined sequence can be stored in the controller as a compressed air flow characteristic of the machine tool. This means that, in addition to the at least one limit value for each of the plurality of predetermined operating states, the "fingerprint" of the machine at a specific time is also stored.

[0029] The setting of the predetermined operating states in the predetermined sequence can, in turn, be carried out by the machine tool's control system, for example, according to a pre-created program. This program, and thus the recording of the compressed air flow characteristics as a "fingerprint," can be run, for example, before commissioning a new machine tool in order to document its compressed air flow in its new state.

[0030] In addition, a so-called "health check" can be carried out by the manufacturer before delivery of a machine tool. This involves setting predetermined operating conditions and comparing the determined compressed air flow characteristics with one or more compressed air flow characteristics of known machine tools of the same type and equipment. For this purpose, for example, a large number of compressed air flow characteristics can be stored in a manufacturer's database. In this way, any leaks, e.g. due to missing components, can be detected before delivery of the machine tool, thereby improving its quality. A compressed air flow characteristic determined in this way upon delivery of the machine tool can be stored in the manufacturer's database as a so-called "factory fingerprint".

[0031] When the machine tool is commissioned by the operator, the program can be used to reset the numerous predefined operating states in a predefined sequence to capture the compressed air flow characteristics of the machine in its new state under its actual operating conditions. This then represents a valid "fingerprint" against which a measured compressed air flow during operation is compared to detect leaks in the machine tool.

[0032] After the machine tool has been commissioned, the program can be run again, for example during maintenance, to determine whether the machine's compressed air flow characteristics have changed during operation. In particular, operating states in which abnormalities occurred, for example, can be specifically selected and only these can be compared with the most recently recorded "fingerprint." This offers the advantage of enabling rapid diagnosis of the entire machine. This allows for regular, targeted diagnosis of the machine tool's compressed air consumers by comparing their compressed air flow characteristics at the current time with those when new or in a previous state.

[0033] In particular, the compressed air flow characteristics can be re-recorded after certain events during machine tool operation. For example, replacing a pneumatically operated switching valve or an air cylinder may require a re-recording of the compressed air flow characteristics, as the new component may have a higher or lower compressed air requirement than the old one. In such a case, the limit values ​​in the affected operating states can also be adjusted.

[0034] Furthermore, a method for learning a machine-specific limit value pattern for monitoring compressed air consumption on a machine tool control system in a learning cycle is proposed.

[0035] In the method, a machine-specific limit value pattern is learned using learning information, with the learning information comprising operating state data of the machine tool and sensor data of a compressed air system at a specific point in time. The learning information encompasses a variety of operating states of the machine tool.

[0036] An operating state can comprise a predetermined combination of activated compressed air consumers of the machine tool. The predetermined combination of activated compressed air consumers can vary, in particular, depending on the type and design of the machine tool. In other words, depending on the machine tool's equipment with pneumatic elements, different combinations of compressed air consumers can occur, so that different predetermined combinations can be defined for different machine tools in the individual operating states. Each predetermined combination can, for example, be assigned to a process step in a manufacturing process of the machine tool. For this purpose, all relevant manufacturing process steps of the machine can be identified in advance, and the compressed air consumers involved in the individual process steps can be determined.A process step with the compressed air consumers involved can therefore represent an operating state. The process steps can, for example, include measuring the tools, in which compressed air is used to clean the tools in order to be able to precisely determine the surface contours of the tools using a laser (operating state “measure tool”). In addition, a tool and / or pallet change in the machine tool, in which one or more pneumatically operated actuators are used, can represent a process step or an operating state (operating state “tool change” or “pallet change”). A switched-off state and / or standby mode of the machine tool can also represent an operating state in which a compressed air flow through the machine tool is detected by the sensor.

[0037] The sensor data of the compressed air system can, in particular, be an actual compressed air flow through the machine tool. For training purposes, a link is created between the measured sensor data and the operating state data, so that the measured sensor data is assigned to a specific operating state, and based on this, one or more specific limit values ​​are defined for the specific operating state. In other words, a specific combination of activated compressed air consumers of the machine tool in a specific operating state can result in a specific actual compressed air flow. This can be measured using the sensor, and a specific limit value can be defined for this operating state based on the measured actual compressed air flow.

[0038] The specific limit value can be defined either for a single machine tool or for a specific machine tool type. In the latter case, a link can be created between measured sensor data and operating state data for a large number of machine tools of the same type to learn the specific limit value for each operating state.

[0039] A computing unit according to the invention is configured, in particular in terms of programming, to carry out a method according to the invention. The computing unit can in particular be a controller of a machine tool or be contained in the controller of the machine tool. For this purpose, a method according to the invention can also be implemented in the form of a computer program or computer program product in a controller of a machine tool. Suitable data carriers for providing the computer program are in particular magnetic, optical and electrical memories, such as hard disks, flash memories, EEPROMs, DVDs, etc. Downloading a program via computer networks (Internet, intranet, etc.) is also possible.

[0040] Short description of the characters

[0041] Figure 1 shows schematically an example of a machine tool according to an embodiment of the invention.

[0042] Figure 2 shows a schematic enlarged view of a display unit of the machine tool shown in Figure 1.

[0043] Figure 3 shows schematically and exemplarily a user interface that can be included, for example, in the display unit shown in Figure 2.

[0044] Figure 4 shows a flowchart comprising method steps according to an embodiment of the invention.

[0045] Figure 5 shows a further flowchart comprising method steps according to a further embodiment of the invention.

[0046] Detailed description of preferred embodiments

[0047] In the following, exemplary embodiments of the present invention are described in detail using exemplary figures. The features of the exemplary embodiments can be combined in whole or in part, and the present invention is not limited to the described exemplary embodiments. In the figures, identical elements are provided with identical reference numerals, so that a repeated description of the elements is omitted unless necessary.

[0048] Figure 1 schematically shows an example of a machine tool 200 according to an embodiment of the invention. The machine tool 200 is connected to a compressed air network (not shown) via a line (not shown in more detail). A flow sensor 201 is attached to the line and measures the compressed air flow through the machine tool 200. The flow sensor 201 can additionally be configured to measure the pressure and temperature of the compressed air, as well as its humidity. For example, the flow sensor 201 can be a calorimetric / thermal flow sensor 201 that determines a compressed air mass flow based on the cooling of a heated element by passing compressed air, and determines a compressed air volume flow by additionally detecting its pressure and temperature.In particular, the flow sensor 201 can determine the compressed air flow in accordance with the ISO standards ISO 6358 / ISO 8778 in "standard liters" and convert a currently determined compressed air volume flow to the reference values ​​specified in this standard (air pressure = 1 bar, air temperature = 20 °C and air humidity = 65%). For this purpose, the flow sensor can additionally contain means for detecting the air humidity. When using a thermal flow sensor, it must also be noted that its measurement accuracy is affected by particles as well as water and oil droplets in the compressed air. To account for these influences, for example, a reference measurement can be carried out with a predetermined compressed air quality. If only a digital pressure value is available, it is advantageous to only monitor the reference to the recorded volume flow at a constant pressure.

[0049] The machine tool 200 shown in Figure 1 further comprises a controller 202 for setting a plurality of predetermined operating states B1, B2, B3 (see Figure 2) of the machine tool 200. The controller 202 can be configured to send signals to a plurality of pneumatic elements (air cylinders, pneumatically operated switching valves, sealing air nozzles, etc., not shown) of the machine tool 200 in order to initiate or stop their actuation, and to receive signals from sensors, in particular from the flow sensor 201. For this purpose, the controller 202 can be connected, for example, by means of the industrial communication standard IO-Link to the plurality of pneumatic elements and the sensors, in particular the flow sensor 201, of the machine tool 200 (indicated by the dashed double arrow between the controller 202 and the flow sensor 201). Any other communication connection is also possible.

[0050] To set the plurality of predetermined operating states B1, B2, B3, the controller 202 can activate a predetermined combination of compressed air consumers of the machine tool 200 in each operating state B1, B2, B3, for example, according to a predefined program 300 (indicated by the double arrow between the program 300 and the controller 202). In the program 300, the predetermined operating states B1, B2, B3 can be defined, for example, according to a predetermined sequence, i.e., the predetermined combinations of compressed air consumers of the machine tool 200 can be activated one after the other in a predetermined sequence.

[0051] Each predetermined combination of compressed air consumers can, for example, be assigned to a process step in a manufacturing process of machine tool 200. For this purpose, all relevant manufacturing process steps of machine 200 can be identified in advance, and the compressed air consumers involved in the individual process steps can be determined. A process step with the involved compressed air consumers can thus represent an operating state and be included in program 300.

[0052] The process steps can, for example, be a measurement of the tools, in which compressed air is used to clean the tools, for example to be able to precisely determine the surface contours of the tools using a laser (operating state "measure tool"). Furthermore, a tool and / or a pallet change in the machine tool 200, in which one or more pneumatically operated actuators are used, can represent a process step or an operating state (operating state "tool change" or "pallet change"). A switched-off state and / or a standby mode of the machine tool 200 can also represent an operating state B1, B2, B3.

[0053] During execution of program 300, an actual compressed air flow Qi (see Figure 2) through machine tool 200 is detected by flow sensor 201 in each of the plurality of predetermined operating states B1, B2, B3. The actual compressed air flow Qi can be detected at a predetermined time interval, e.g., with a measurement frequency of 4 Hz. The detected measured values ​​can be filtered to suppress peaks in the actual compressed air flow Qi during a switching process from one operating state B1, B2, B3 to another operating state B1, B2, B3. For this purpose, a mean filter, a median filter, or a Gaussian filter can be used, for example.A compressed air flow profile of the machine tool 200 recorded in this way can represent its compressed air flow characteristic 400 at the time of recording and can be stored as a so-called fingerprint 400 in the controller 202 (indicated by the one-way arrow from the program 300 to the fingerprint 400). A time for recording the compressed air flow characteristic 400 can, for example, be before the machine tool 200 is put into operation in order to determine its compressed air flow in its new state.

[0054] At the same time, at least one limit value Gl, G2 (see Figure 2) for the compressed air flow rate can be determined for each of the predetermined operating states Bl, B2, B3 on the basis of the determined compressed air flow rate characteristic and stored in the controller 202 of the machine tool 200. For example, in the “tool change” operating state, in which, for example, one or more actuators can be pneumatically actuated in order to, for example, open and / or close access to a tool magazine, the compressed air flow rate (compressed air volume flow) through the machine tool can be continuously measured and, for example, a maximum value of the recorded flow rate profile during the tool change can be defined as the limit value Gl, G2. Alternatively or additionally, a value greater than the maximum value of the recorded flow rate profile can be defined as the limit value Gl, G2. In this case, for example, a predetermined value can be added to the recorded maximum value in this operating state Bl, B2, B3 in order to, for example,B. Measurement tolerances of the flow sensor 201 must be taken into account. It is also possible to define multiple limit values ​​Gl, G2 for the compressed air flow. For example, a maximum value of the detected flow curve in an operating state Bl, B2, B3 can be defined as the first limit value Gl, and a value greater than the detected maximum value can be defined as the second limit value G2.

[0055] These limit values ​​G1, G2 are monitored during operation of the machine tool by means of a display unit 202a of the controller 200 (indicated by the one-way arrow from the machine tool 200 to the display unit 202a) in order to be able to determine if the compressed air consumption required for the operation of the machine tool 200 is exceeded due to leaks. In order to be able to carry out a targeted diagnosis of the compressed air consumption, the program 300 can be run again, for example during maintenance, to determine whether the compressed air flow characteristics 400 of the machine have changed. In this context, a new fingerprint 400 can be created, which can be compared with the previous one (indicated by the double arrow between the two fingerprints 400). If, for example, a pneumatic component was replaced during maintenance, the new fingerprint 400 can be stored in the controller 202.In this context, at least one limit value Gl, G2 in operating states Bl, B2, B3, which are affected by the replacement of the pneumatic component, can also be checked and, if necessary, adapted to the values ​​of the new fingerprint 400.

[0056] If, during operation of the machine tool 200, at least one limit value Gl, G2 is exceeded in one of the predetermined operating states Bl, B2, B3, a warning can be issued and stored in a log 500. The log 500 can contain information regarding a time of the warning, an operating state at the time of the warning, a value of the actual compressed air flow Qi that led to the warning, etc. Based on the log 500, for example, a cause of the warning can be deduced and a leak at an affected compressed air consumer can be detected. If, for example, a warning occurs during the "tool change" operating state, a leak in the pneumatics in the area of ​​the tool changer can be deduced. Based on the measured actual compressed air flow Qi at the time of the warning, a pneumatic element responsible for the leak can be further narrowed down if necessary.

[0057] Using the described functions of the machine tool 200 shown, it is possible to continuously monitor its compressed air flow and reliably detect any leaks in pneumatic elements in the machine tool in all operating states B1, B2, and B3 of the machine. Furthermore, the functionality of all compressed air-supplied elements can be ensured, and if a leak is detected, the source can be identified or at least localized.

[0058] Figure 2 schematically shows an enlarged view of the display unit 202a of the machine tool shown in Figure 1. The display unit 202a comprises a diagram 20 in which a measurement of a current actual compressed air flow Qi through the machine tool shown in Figure 1 is plotted against a first and second limit value G1, G2 over time tauf. The second limit value G2, shown as a solid line, is greater than the first limit value G1, shown as a dashed line.

[0059] Furthermore, the display unit 202a contains a circular display 21, which displays a last recorded actual compressed air flow Qi numerically and in the form of a ring-shaped pointer, and another display 22, in which loss values ​​VI, V2 of the compressed air consumption of the machine tool are listed in a table. In the ring-shaped pointer of the circular display 21, the limit values ​​Gl and G2 are also shown as dashed and solid lines, respectively, and the last recorded actual compressed air flow Qi is shown as a hatched area 21a. In the tabular display 22, a loss value VI, which results from exceeding the first limit value Gl, and a loss value V2, which results from exceeding the second limit value G2, are each shown as a compressed air volume (m 3) and as costs (€). In addition, a sum of the two loss values ​​VI, V2 is displayed. Furthermore, the display unit 202a contains a further field 23 with a date and time of the current measurement and a button 24 for starting and stopping the measurement. The data in field 23 can be accessed, for example, if a warning is issued and logged when the second limit value G2 is exceeded. In this case, the date and time of the warning can be included in the log 500.

[0060] During the present measurement, three operating states B1, B2, and B3 of machine tool 200 were set (see Diagram 20). In these operating states B1, B2, and B3, the limit values ​​G1 and G2 each have a constant, different value. The limit values ​​can be determined as explained above.

[0061] A transition of the limit values ​​Gl, G2 between a first and a second operating state Bl, B2 is ramp-shaped in the present case, while a further transition between the second and a third operating state B2, B3 has a peak due to a strong widening of the limit values ​​Gl, G2. This is due to a possible increase in the compressed air demand when setting the third operating state B3, for example by actuating an air cylinder, which could otherwise be falsely detected as a loss of compressed air. In this way, a period of a switching process from a first operating state Bl, B2, B3 to a second operating state Bl, B2, B3 can be disregarded when determining the at least one limit value Gl, G2.

[0062] In the present case, the recorded actual compressed air flow Qi remains below the limit values ​​Gl, G2 throughout the entire measurement, so that no loss values ​​VI, V2 are entered in the tabular display 22. However, it can be seen that shortly after the switchover from the first to the second operating state Bl, B2, a peak in the actual compressed air flow Qi is detectable, the maximum value of which lies just below the first limit value Gl. Such behavior can be analyzed more precisely, for example, by re-recording the compressed air flow characteristic 400, or at least parts thereof.

[0063] Figure 3 shows a schematic and exemplary user interface 30, which can be contained, for example, in the display unit 202a shown in Figure 2. Using this user interface 30, leakage monitoring of a machine tool 200 can be configured, i.e., compressed air consumers contained in the machine tool 200 can be defined, depending on which the plurality of operating points for recording a "fingerprint" of the machine tool is then determined. The leakage monitoring configuration saved via the user interface 30 can be saved under a number 30h assigned to the machine tool 200 by means of a "Save table" button 30f, for example in a database (not shown) of a manufacturer and / or in an operator's database.

[0064] The user interface 30 comprises a table comprising four columns 30a-30d. Columns 30a-30c identify systems and subsystems of the machine tool 200, and column 30d indicates whether the corresponding system is contained in the machine tool. A subsystem 1 shown in column 30b is contained in a corresponding system in column 30a, and a subsystem 2 shown in column 30c is contained in a corresponding subsystem 1 in column 30b. Subsystems 1 and 2 can not only contain further components / parts of the systems named in column 30a, but can also, in particular, include actions / operations of the system(s).

[0065] In this case, the systems "base machine," "tool changer," "laser," "pallet changer," and "spindle" are listed in column 30a. The "base machine" includes a "main valve" and a "coolant valve" (coolant lubricant) as the first subsystems, and the "tool changer" includes a "chain magazine" and a "tool change" as the first subsystems. For the laser and the pallet changer, "tool measurement" and a "pallet change" are listed as the first subsystems in column 30b, respectively. For the "spindle," the first subsystem listed in column 30b is identical to the system listed in column 30a.

[0066] As already mentioned, further components and / or actions are assigned to the first subsystems, each of which is listed as second subsystems in column 30c. In this case, a "sealing air measuring system" is assigned to the "main valve" as the second subsystem, and the "cooling lubricant valve" operates a "booth flushing system," a "roof flushing system," and a "flushing gun." Column 30d indicates that the present machine tool 200 only has one "booth flushing system." With regard to the "chain magazine" listed as the first subsystem, a "tool transfer station (chain_tool_transfer station)" is mentioned as an example, and the first subsystem "tool change" includes an action "tool flap moved (tool_flap_moved)," which is also used in the present machine tool, as shown in column 30d.

[0067] Likewise, for the first subsystem "tool measurement," an action "laser moved (WZV_Laser_moved)" is shown, and for the pallet change, a query "pallet present (PW_Palette_present)" is shown. The latter is answered positively in the present machine tool 200 by the index 1 in column 30d. In this example, the "spindle" is assigned an action "cone blowout" as a second subsystem. The systems and subsystems are not limited to the examples shown, but can include a multitude of other components and actions / activations (indicated by three dots in individual cells and rows of the table).

[0068] Based on the configuration of the compressed air consumers defined and saved via the user interface 30, the operating states for recording the "fingerprint" of the machine tool 200 can be determined. In other words, the operating states to be set can be individually defined depending on the type and / or configuration of the machine tool 200. This allows, for example, a number of operating states to be determined machine-specifically and a time for measuring the "fingerprint" to be optimized.

[0069] In addition, the input interface 30 includes two further buttons, "Delete Table" 30e and "Load Table" 30g, which can be used to delete an existing configuration or load a saved configuration. The latter is particularly helpful for locating the cause of a leak. If, in the present case, for example, an exceedance of the first and / or second limit value Gl, G2 was detected in the area of ​​the first subsystem "cooling fluid valve", it can be identified from the configuration shown that on the present machine tool 200 the "cooling fluid valve" only directs compressed air to the "cabinet flushing", so that a leak must be sought precisely in this second subsystem. In this way, the leak monitoring configuration can also provide valuable services in the search for the cause of a leak.

[0070] Figure 4 shows a flowchart comprising method steps according to one embodiment of the invention. The method shown serves to monitor a change in a compressed air flow due to leaks in a machine tool 200, as shown, for example, in Figure 1. In particular, leaks in a compressed air system of the machine tool 200 can be detected and quantified using the method.

[0071] For this purpose, after the start of the method, in a method step S100, a plurality of predetermined operating states B1, B2, B3, each with a predetermined combination of activated compressed air consumers, are first set on the machine tool 200. This can be done, for example, using a predefined program, as described in connection with Figure 1. In each of the plurality of predetermined operating states B1, B2, B3, an actual compressed air flow Qi through the machine tool 200 is detected by means of a sensor, for example by means of a flow sensor 201, as shown in Figure 1 (S110). Based on the detected actual compressed air flow Qi, in a further method step S120, at least one limit value G1, G2 for the compressed air flow is defined for each of the plurality of operating states B1, B2, B3.This can, for example, be a maximum value of an actual compressed air flow curve measured during an operating state B1, B2, B3. Alternatively or additionally, a value greater than this maximum value can also be specified as the limit value G1, G2, for example, to take into account tolerances of the flow sensor 201. In the present case, a first limit value G1, which can, for example, be a measured maximum value of an actual compressed air flow Qi, and a second limit value G2, which can be higher than the first limit value, are specified for each of the plurality of predetermined operating states B1, B2, B3.

[0072] The defined limit values ​​Gl, G2 can be stored and monitored in a subsequent process step S130 during operation of the machine tool 200. If one or both of the limit values ​​Gl, G2 are exceeded, this exceedance is recorded.

[0073] If the actual compressed air flow rate Qi exceeds the first limit value (Qi > Gl), in the present case a first loss value VI is determined in method step S140 based on a difference between the actual compressed air flow rate Qi and the first limit value Gl. For example, the first loss value VI, as shown in Figure 2, can be a compressed air volume caused by a first leak, which is determined by integrating the difference between the actual compressed air flow rate Qi and the first limit value Gl over time if this assumes a positive value. As a further loss value VI, costs for providing the drive energy for the compressed air volume lost due to the first leak can be determined according to Figure 2. If the detected actual compressed air flow rate Qi is below the first limit value Gl, the method returns to step S130 to continue monitoring the actual compressed air flow rate Qi.

[0074] If the actual compressed air flow Qi exceeds the second limit value (Qi > G2), a warning is issued in process step S150; otherwise, the process returns to process step S130. In process step S150, the issued warning can also be saved in a log. The log 500 can contain information regarding the time of the warning, an operating state B1, B2, B3 at the time of the warning, a value of the actual compressed air flow Qi that led to the warning, etc. Based on the log 500, for example, a cause of the warning can be determined and a leak can be detected at an affected compressed air consumer.

[0075] In addition, if the second limit value G2 is exceeded, method step S140 is also performed, in which a second loss value V2 is determined based on a difference between the actual compressed air flow rate Qi and the second limit value G2. As shown in Figure 2, this can in turn be a compressed air volume caused by a second leak, which is determined by integrating the difference between the actual compressed air flow rate Qi and the second limit value G2 over time if this assumes a positive value. As a further loss value V2, the costs for providing the drive energy for the compressed air volume lost due to the second leak can be determined according to Figure 2.

[0076] After the warning is output in method step S150, the method is terminated in this case, e.g., in order to eliminate a cause of a leak before the machine tool 200 is operated further.

[0077] Figure 5 shows a further flowchart comprising method steps according to a further embodiment of the invention. The method shown serves to teach a machine-specific limit value pattern for monitoring compressed air consumption on a machine tool control 202 in a learning cycle using teaching information. The taught machine-specific limit pattern can, for example, be part of the program 300 shown in Figure 1 for setting the plurality of predetermined

[0078] operating states Bl, B2, B3. The learning information includes, on the one hand, operating state data that is recorded after the start of the method in method step S200, and, on the other hand, sensor data that includes an actual compressed air flow Qi of the machine tool 200 and is recorded in method step S205. The operating state data can be recorded, for example, based on process steps of a manufacturing process that is carried out by the machine tool 200. A specific combination of compressed air consumers can be assigned to each process step, from which an operating state Bl, B2, B3 with a typical compressed air flow can result. This compressed air flow can be measured, for example, using a flow sensor 201, as shown in Figure 1. In this way, in method step S210, a recorded operating state Bl, B2, B3 can be linked to a measured actual compressed air flow Qi.In method step S220, at least one specific limit value for the compressed air flow through the machine tool 200 can be defined for the detected operating state B1, B2, B3. This can be done, for example, in the same way as in method step S120 in Figure 3. The specific limit value can be defined both for an individual machine tool 200 and for a specific machine tool type. In the latter case, a link between measured sensor data and operating state data for a plurality of machine tools 200 of the same type and equipment can be created to learn the specific limit value for each operating state B1, B2, B3.

[0079] Steps S210 and S220 can be repeated until at least one specific limit value has been defined for each detected operating state B1, B2, B3. From the multitude of detected operating states B1, B2, B3 and their associated limit values, a limit value pattern can then be created in step S230, which can be used, for example, in the program shown in Figure 1.

[0080] In this way, for example, when creating an initial compressed air flow characteristic 400 prior to commissioning a machine tool 200, it can be determined whether the machine tool 200 does not exceed a typical compressed air flow rate for the respective machine tool type. Thus, the functionality of the compressed air system of the machine tool 200 can be tested while it is new, thus improving its quality.

Claims

CLAIMS 1. A method for monitoring a change in compressed air flow due to leaks on a machine tool (200) containing a controller (202) and a sensor (201), comprising the steps of: - setting a plurality of predetermined operating states (B1, B2, B3) on the machine tool (200) (S100); - detecting a compressed air flow (Qi) through the machine tool (200) in one or more, preferably each, of the plurality of predetermined operating states (B1, B2, B3) by means of the sensor (201) (S110); - setting at least one limit value (Gl, G2) for the compressed air flow (Qi) based on the detected compressed air flow for one or more, preferably each, of the plurality of predetermined operating states (Bl, B2, B3) (S120); - monitoring the at least one defined limit value (Gl, G2) in one or more, preferably each, of the plurality of predetermined operating states (Bl, B2, B3) during operation of the machine tool (200) (S130) to detect a Compressed air flow change due to leaks.

2. The method according to claim 1, wherein each of the plurality of predetermined operating states (B1, B2, B3) comprises a predetermined or predeterminable combination of activated compressed air consumers of the machine tool (200).

3. The method according to claim 1 or 2, wherein a number of the plurality of predetermined operating states is dependent on a type of machine tool and / or an equipment of the machine tool.

4. Method according to at least one of the preceding claims, wherein the at least one defined limit value (G1, G2) for each of the plurality of predetermined operating states (B1, B2, B3) in the control (202) of the machine tool (201) is stored.

5. Method according to at least one of the preceding claims, further comprising the step: Issuing a warning if the at least one specified limit value (Gl, G2) is exceeded in at least one of the plurality of predetermined operating states (Bl, B2, B3) (S150).

6. Method according to at least one of the preceding claims, wherein a period of a switching process from a first operating state (Bl, B2, B3) to a second operating state (Bl, B2, B3) is not taken into account when determining the at least one limit value (Gl, G2), and in particular the operating states (Bl, B2, B3) of the machine tool are constant phases of the operation of the machine tool.

7. The method according to at least one of claims 3 to 5, wherein the monitoring of the at least one limit value (Gl, G2) in each of the plurality of predetermined operating states (Bl, B2, B3) is carried out by comparing an actual compressed air flow (Qi) with the at least one stored limit value (Gl, G2).

8. The method according to claim 7, wherein for the comparison, values ​​of the actual compressed air flow (Qi) are detected by means of the sensor (201) and subsequently filtered.

9. The method according to claim 7 or 8, wherein if the actual compressed air flow (Qi) exceeds the at least one limit value (Gl, G2), at least one loss value (VI, V2) is determined based on a difference between the actual compressed air flow (Qi) and the at least one limit value (Gl, G2) (S140).

10. The method according to claim 9, wherein the actual compressed air flow (Qi) at least one limit value (Gl, G2) and the at least one loss value (VI, V2) are displayed on a display unit (202a) of the controller (202), wherein the display is made in particular directly on the machine tool.

11. The method according to at least one of the preceding claims, wherein each warning is stored in a log (500).

12. Method according to at least one of the preceding claims, wherein the plurality of predetermined operating states (B1, B2, B3) are set in a predetermined sequence, and a profile of the detected compressed air flow according to the predetermined sequence is stored as a compressed air flow characteristic (400) of the machine tool (200) in the controller (202).

13. The method according to claim 12, wherein the compressed air flow characteristic (400) is recorded again after certain events in the operation of the machine tool (200).

14. Method for learning a machine-specific limit value pattern for a compressed air flow change due to leaks in a machine tool control (202) in a learning cycle, wherein a machine-specific limit value pattern of a machine tool (200) is learned by means of learning information, wherein the learning information comprises operating state data of the machine tool (200) and sensor data of a compressed air system, in particular an actual compressed air flow (Qi) through the machine tool (200), at a specific point in time, wherein for the learning process a link is created between measured sensor data and operating state data, so that the measured sensor data are assigned to a specific operating state (Bl, B2, B3) and based thereon one or more specific limit values ​​are defined for the specific operating state (Bl, B2, B3), and wherein the learning information comprises a plurality of operating states (Bl, B2, B3) of the Machine tool (200) to learn the machine-specific limit pattern of the machine tool (200).

15. A method for monitoring a change in a compressed air flow due to leaks on a machine tool (200) which includes a controller (202) and a sensor (201), comprising the steps of: - Setting at least one limit value (Gl, G2) for a compressed air flow (Qi) for one or more predetermined operating states (Bl, B2, B3) (S120) of the machine tool; - Monitoring the at least one defined limit value (Gl, G2) in one or more, preferably each, of the plurality of operating states (Bl, B2, B3) during operation of the machine tool (200) (S130) to detect a change in the compressed air flow rate due to leaks.

16. A computing unit (202) comprising a processor configured to execute the method according to at least one of the preceding claims.

17. Machine tool (200) comprising a sensor (201) and the computing unit (202) according to claim 16.

18. A computer program comprising instructions which, when executed by a computer, cause the computer to carry out the method according to claims 1 to 15.

19. A computer-readable data carrier on which the computer program according to claim 18 is stored.

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