Machine tool for machining a workpiece, hydraulic device, hydraulic system and method for machining a workpiece

Abstract

The invention relates to a machine tool (1000) for machining workpieces using a machining fluid. The machine tool (1000) comprises a working space (1) in which the workpiece machining takes place, at least one fluid consumer (2) via which a machining fluid for the workpiece machining can be supplied to the working space (1), a hydraulic device (3) which is configured to supply the at least one fluid consumer (2) with the machining fluid, and a control device (4) for controlling the machine tool. The hydraulic device (3) comprises a pump (32) for conveying the machining fluid, an inlet (35), via which the machining fluid conveyed by the pump (32) is fed to the at least one fluid consumer (2), and a flow measuring unit (351), which is associated with the inlet and which comprises at least a first measuring unit (351a) and a second measuring unit (351b), which are each configured to detect a flow rate of the machining fluid in the inlet (35). The control device (4) is set up to control the machine tool (1000) as a function of a first actual value detected by the first measuring unit (351a) and / or of a second actual value detected by the second measuring unit (351b) of the flow rate of the machining fluid in the inlet (35).

Description

Machine tool for machining workpieces, hydraulic device, hydraulic system and method for machining a workpiece DESCRIPTION Technical area

[0001] The present invention relates to a machine tool for machining workpieces, a hydraulic device for use on such a machine tool, a hydraulic system and a method for machining a workpiece. Background of the invention

[0002] Machining fluids, particularly cooling lubricants (CL), are commonly used in the field of machining workpieces. These fluids are intended to improve workpiece machining in terms of tool wear and machining quality. These fluids are typically oil-water emulsions that are applied to a machining zone, i.e., the area in which a tool removes material from a workpiece.

[0003] The use of the machining fluid reduces the friction between the workpiece and the tool and removes the heat that inevitably arises during workpiece machining from the machining area.

[0004] The machining fluid thus serves to cool the tool or workpiece and reduce tool wear. Furthermore, the machining fluid can be used in some machining processes to remove the generated chips by flushing them from the machining area. Furthermore, the machining fluid can have corrosion-inhibiting properties, thereby protecting the workpiece and / or the workpiece from corrosion during or after machining.

[0005] The above effects improve the machining quality and thus the dimensional accuracy of the workpiece, for example the surface quality, which leads to manufactured workpieces of high quality

[0006] In the current state of the art, it is common practice to supply the machining fluid to the machine tool using a speed-controlled pump. Since no risk can be taken with the supply during workpiece machining, the pump provides the fluid at a constant, predefined and comparatively high supply pressure of approximately 40 to 100 bar, in order to prevent any undersupply of the machining area during To prevent workpiece processing which, for example, renders the tool used unusable.

[0007] The blanket provision of a constant supply pressure throughout the entire workpiece machining process in such a high pressure range inevitably results in high energy consumption by the pump. Depending on the design of the component supplying the machining fluid, particularly its fluid mechanics properties, this can lead to high power losses, as the pump provides a higher supply pressure than actually required.

[0008] This reduces the service life of the pump and other hydraulic components used to supply the machining fluid, increasing maintenance effort and costs. Furthermore, the energy consumption for supplying the machining fluid is sometimes unnecessarily high, which in turn leads to high energy costs, which are particularly significant in mass production. Summary

[0009] The present invention is therefore based on the object of overcoming the problems known in the prior art and of providing a possibility for machining workpieces using a machining fluid which is improved compared to the prior art and which in particular reduces energy consumption during workpiece machining and stress on hydraulic components.

[0010] To achieve this object, a machine tool for machining workpieces according to claim 1, a hydraulic device according to claim 20, a hydraulic system according to claim 21 and a method for machining a workpiece according to claim 22 are provided.

[0011] The respective dependent claims relate to preferred embodiments, which can be provided individually or in combination.

[0012] According to a first aspect of the invention, a machine tool for machining workpieces using a machining fluid, in particular a cooling lubricant, is provided. The machine tool comprises a work space in which the workpiece machining takes place, at least one fluid consumer via which a machining fluid for machining the workpiece can be supplied to the work space, a hydraulic device configured to supply the at least one fluid consumer with the machining fluid, and a control device for controlling the machine tool. The hydraulic device comprises a pump for conveying the machining fluid, an inlet via which conveyed machining fluid is directed to the at least one fluid consumer, and a flow measuring device assigned to the inlet, which comprises at least a first measuring unit and a second measuring unit, each of which is configured to detect a flow rate of the machining fluid in the inlet, in particular a volume flow of the machining fluid. The control device is configured to control the machine tool, in particular the hydraulic device as part of the machine tool, as a function of a first actual value detected by the first measuring unit and / or a second actual value of the flow rate, in particular the volume flow of the machining fluid in the inlet, detected by the second measuring unit.

[0013] During workpiece machining, the machining fluid flows through the fluid consumer into the working area of ​​the machine tool and is fed into the machining area to support the workpiece machining as described above.

[0014] A fluid consumer can be understood as any component of the machine tool through which the machining fluid for workpiece machining can be supplied to the work area. The fluid can be supplied to the work area directly or via nozzles, nebulizers, or other components attached to the fluid consumer that allow the machining fluid to flow through and thus act as supply points.

[0015] A flow rate is any quantity that indicates the amount of processing fluid flowing through a particular component, e.g., the inlet or the fluid consumer, over a specific period of time. This can be, but is not limited to, a volume flow, a mass flow, or even a flow velocity, from which, given knowledge of the density and flow cross-section, the mass or volume flow can be calculated. It is understood that any reference to a flow rate in this description can be replaced by a reference to one of the above quantities.

[0016] Preferably, a tool with internal fluid channels is attached to the fluid consumer, through which the machining fluid is discharged into the work area. This not only supplies the machining fluid directly to the machining area via the tool, but also cools the tool by the machining fluid flowing inside it. This implements the concept of internal coolant supply, which is well known in the prior art.

[0017] For workpiece processing, the amount of supplied material is ultimately machining fluid is crucial and not the supply pressure applied to the fluid consumer.

[0018] Depending on the fluid mechanical properties of a feed point on the Fluid consumers, e.g. the geometric dimensions of an opening or a channel through which the machining fluid enters the working space, the supply pressure has a certain This value has no significant or only a minor impact on the flow rate or volume flow, so that an increase in the supply pressure primarily only increases the power loss of the hydraulic device without significantly increasing the supply of processing fluid. This would place unnecessary strain on the components of the hydraulic device and also cause unnecessarily high energy costs.

[0019] This is the case in the prior art, in which, with the aid of pressure measuring units of the hydraulic device, the supply pressure applied to the fluid consumer is kept at a flat rate of the 40 to 100 bar mentioned at the beginning, which corresponds to a pressure control. In particular, in view of the large number of supply points that can be used and their respective different fluid-mechanical properties, the associated disadvantages can vary in severity.

[0020] The present invention now breaks with this disadvantageous concept of pressure control during the supply of the machining fluid and, in particular, provides the necessary hardware on the machine tool side to implement reliable flow rate control or, if the flow rate to be controlled is a volume flow, volume flow control (instead of the usual pressure control). This enables, in particular, the use of a multitude of different fluid-mechanically different supply points while constantly maintaining optimal operating conditions of the hydraulic device.

[0021] To implement flow rate control, the flow rate of the processing fluid in the inlet must be determined reliably and as accurately as possible. This is difficult due to the large number of possible supply points and the resulting widely varying flow rates and volume flows in the inlet, thus requiring a comparatively large range of values ​​to be covered.

[0022] The hydraulic device can be configured to provide flow rates in the inlet, specified as volume flows, in a range from 0.001 liters per minute (1 / min) to 80 1 / min or in a range from 0.01 to 501 / min, which in particular correspond to the said value range to be covered, during workpiece machining.

[0023] The inventors have now discovered that the accuracy required to implement robust flow rate control over the aforementioned wide range of values ​​can be achieved by using the previously described flow measuring device, which comprises at least two independent measuring units. The two measuring units complement each other to cover the aforementioned wide range of values ​​and provide the measurement accuracy required for flow rate control for both small and large flow rates.

[0024] This makes it possible, for example, to reliably and accurately measure flow rates specified as volume flows in a range from a few hundred milliliters per minute up to over 30 1 / min.

[0025] The former is the case, for example, with internal coolant supply via drills with a diameter of a few millimeters, whereas the latter is a common value for internal coolant supply via milling heads in large-area workpiece machining

[0026] The two independent measurements therefore always allow a reliable statement to be made about the current flow rate in the inlet, across the entire range of possible flow rates in the inlet path, which is large in the context of the invention, and which forms the basis for reliable flow rate control.

[0027] The described design of the machine tool or hydraulic device therefore allows for reliable flow rate or volume flow control when supplying the fluid consumer, regardless of the fluid mechanical properties of the actual supply point. This ensures that an optimal flow rate or volume flow can always be provided.

[0028] Thus, the present invention enables a flow rate control or volume flow control, with which disadvantageous operating conditions with "too high" pressure for a variety of fluid-mechanically different supply points can be successfully avoided. This can significantly reduce the stress on the hydraulic device and the power loss occurring within it, which in turn reduces the energy costs during operation of the machine tool and increases the service life of the hydraulic device itself.

[0029] Particularly with regard to the concept of the internal coolant supply, the machine tool according to the invention or its hydraulic device for flow rate control creates the possibility of always setting the optimal flow rate for the respective tool with internal fluid channels in order to achieve optimal cooling and lubrication with the lowest possible power loss of the hydraulic device.

[0030] Conventional pressure control is very inaccurate in comparison, and the optimal pressure for a specific process is either impossible or difficult to determine. Furthermore, such values ​​cannot be transferred to other machine tools, even for the same tool or the same process, because the pressure applied to the fluid consumer varies due to different piping and the like.

[0031] In contrast, the invention offers the advantage that it is largely independent of the specific properties of individual machine tools, so that optimal values ​​for the flow rate of individual tools determined on a machine tool with internal coolant supply can be easily transferred to other machine tools and essentially lead to the same results.

[0032] A further negative effect of conventional pressure control with "too high" pressure is the high atomization of the processing fluid when it is introduced into the work area. Especially when using the mist extraction system commonly used in this area to remove the atomized processing fluid, the high atomization results in high consumption of the processing fluid and high energy costs for operating the mist extraction system.

[0033] In contrast, the possibility according to the invention offers the advantage that a controlled amount of processing fluid is introduced, i.e., not "too much," so that an oversupply, which, among other things, leads to unnecessarily high atomization, can be successfully avoided. Preferably, the control device is configured to control the hydraulic device and in particular its pump depending on the detected first and / or the detected second actual value, preferably by adjusting an operating parameter of the pump that determines the delivery rate.

[0034] The machine tool is preferably a numerically controlled machine tool, wherein the control device is configured to control various actuators of the machine tool. Said actuators can include, in addition to drives of a machining device, e.g. a work spindle, also drives of a workpiece holder, e.g. a machine table.

[0035] Optionally, the machine tool can also comprise two control devices: one for the hydraulic device and one for other actuators that are not part of the hydraulic device. These two control devices are preferably coupled to each other.

[0036] Preferably, the flow measuring device may comprise further measuring units for the flow rate in order to further increase the measuring accuracy in the value range to be covered.

[0037] The flow measuring device preferably comprises an evaluation unit configured to select a reference value from the two detected actual values, which is used to control the machine tool. Alternatively, the evaluation unit can be configured to determine a resulting flow rate value from the two detected actual values, for example, by weighted averaging of the detected actual values, wherein the weighting factors themselves preferably depend on one or both detected actual values. Said resulting flow rate value can then be used to control the machine tool.

[0038] This allows differences between the two measuring units, particularly with regard to their measuring ranges and measurement deviations, to be better taken into account in order to further improve the accuracy of the control.

[0039] In a preferred embodiment, the flow measuring device is a volume flow measuring device, so that at least the flow rate in the inlet is indicated by a volume flow

[0040] In a preferred embodiment, the first measuring unit and the second measuring unit are arranged in series with respect to a flow direction of the processing fluid in the inlet.

[0041] This means that the actual values ​​are recorded one after the other, so that the recorded actual values ​​refer to the same fluid flow.

[0042] In a preferred embodiment, a measuring range of the first measuring unit differs from a measuring range of the second measuring unit, in particular neither of the two measuring ranges is a subset of the other measuring range.

[0043] The two measuring units complement each other to cover the wide range of possible flow rates as completely as possible.

[0044] The measuring ranges of the measuring units can be a nominal or a technical measuring range in which accurate and therefore usable measured values ​​of the flow rate to be controlled can be recorded.

[0045] The measuring range describes a value range of the variable to be measured, here the flow rate, for example via the volume flow, in which the measurement deviations remain within specified limits. Preferably, with reference to a volume flow, the absolute value of the maximum measurement deviation of the first measuring unit in its measuring range is less than or equal to 3 l / min, more preferably less than or equal to 1.5 l / min, more preferably less than or equal to 0.75 l / min and particularly preferably less than or equal to 0.1 l / min. More preferably, the absolute value of the maximum measurement deviation of the second measuring unit in its measuring range is less than or equal to 8 l / min, more preferably less than or equal to 5 l / min, more preferably less than or equal to 2.5 l / min and particularly preferably less than or equal to 1 l / min.

[0046] In a preferred embodiment, the measuring range of the first measuring unit and the measuring range of the second measuring unit overlap in an overlap region.

[0047] This allows the two measuring ranges to be combined particularly well without having to accept excessive measurement deviations in the area of ​​the transition from one measuring range to the other.

[0048] In a preferred embodiment, the measuring range of the first measuring unit is a range from 0 to 30 1 / min, preferably a range from 0.01 to 15 1 / min, and / or the The measuring range of the second measuring unit is a range from 1 to 801 / min, preferably a range from 1 to 50 1 / min.

[0049] In a preferred embodiment, the measuring ranges of the first and second measuring units as well as a minimum volume flow of the pump are adapted to each other in such a way that the minimum volume flow lies in the overlap area

[0050] The minimum flow rate refers to the lowest flow rate the pump can deliver during proper operation. Attempting to set a lower flow rate typically results in unfavorable operating conditions, such as undesirable overheating or resonance vibrations of the mechanical components, which are not consistent with proper operation.

[0051] In a preferred embodiment, a volume flow operating range of the pump is a subset of a union of the measuring ranges of the first and the second measuring unit

[0052] As a result, the entire range of volume flows that can be implemented by the pump lies within the resulting measuring range spanned by the two measuring units.

[0053] The flow rate operating range describes the possible flow rates that the pump can deliver, based on its factory specifications. The lower limit of the flow rate operating range typically corresponds to the minimum flow rate; however, this is not necessarily the case.

[0054] In a preferred embodiment, the volume flow operating range of the pump is a range from 0.1 to 801 / min, preferably from 1 to 501 / min and particularly preferably from 5 to 401 / min.

[0055] Preferably, the pump can build up a pressure in the inlet of up to 100 bar, preferably up to 80 bar and particularly preferably up to 50 bar.

[0056] Thanks to the volume flow control, it is no longer necessary to provide the highest possible supply pressure in order to achieve a certain minimum volume flow, so that the pump itself can be dimensioned smaller.

[0057] In a special embodiment, in which the flow measurement or volume flow measurement has proven to be particularly accurate, the volume flow operating range of the pump extends from 5 to 361 / min, the first measuring range ranges from 0.01 to 15 1 / min with a maximum measurement deviation of 0.75 1 / min and the second measuring range ranges from 1 to 501 / min with a maximum measurement deviation of 2.5 1 / min.

[0058] In a preferred embodiment, the machine tool further comprises a setpoint generator, via which a setpoint of a flow rate applied to the at least one fluid consumer, in particular a volume flow of the machining fluid, is provided.

[0059] Preferably, the control device is configured to control the hydraulic device as a function of the setpoint value provided by the setpoint generator and the detected first actual value and / or the detected second actual value, or as a function of the determined resulting flow rate value, in particular to control the flow rate applied to the at least one fluid consumer.

[0060] The setpoint generator can be implemented as a separate component of the machine tool or as part of the control device. Alternatively, the setpoint generator can also be provided externally, for example, in an external data management system connected to the machine tool via a data interface.

[0061] This allows the hydraulic device to be individually adapted to any tool by reading the associated tool parameters and using them for control purposes. This makes it particularly advantageous to use an optimal flow rate, especially an optimal volume flow, determined and stored for a specific tool in advance for control purposes.

[0062] In a preferred embodiment, the control device is configured to adjust an operating parameter of the pump of the hydraulic device, which determines the delivery capacity, in particular a delivery rate or a speed of the pump, as a function of the provided setpoint value and the detected first actual value and / or the detected second actual value, or as a function of the determined resulting flow rate value.

[0063] In a preferred embodiment, the hydraulic device further comprises a bypass device arranged between the inlet and the pump.

[0064] This allows partial amounts of the processing fluid pumped by the pump to be diverted before entering the inlet (backflow), thus providing flow rates or volume flows in the inlet that are below the pump's minimum volume flow. The return flow flowing through the bypass device then flows back into a fluid tank for the processing fluid, for example.

[0065] In a preferred embodiment, the bypass device comprises at least one flow regulating means via which a flow of a return flow of the processing fluid flowing through the bypass device can be regulated.

[0066] Such regulating means can regulate the flow, for example, by changing a flow resistance through the bypass device, e.g. in the form of a throttling means controllable by the control device or a controllable bypass valve.

[0067] Instead of a controllable bypass valve, a bypass pump can be used alternatively or additionally, which can be controlled by the control device, in particular by setting an operating parameter of the bypass pump that determines the delivery rate.

[0068] Preferably, the control device is configured to adjust an operating parameter of the flow regulating means that determines the backflow as a function of the detected first and / or the detected second actual value, or as a function of the determined resulting flow rate value, and / or the provided setpoint value, in particular in order to control the flow rate applied to the at least one fluid consumer.

[0069] In this way, the control system is supplemented by an additional adjusting screw, which also enables controllable flow rates or volume flows in the inlet below the minimum volume flow. Controlling the bypass valve preferably involves adjusting the degree of opening of the bypass valve or adjusting the flow resistance of the bypass valve.

[0070] In a preferred embodiment, the bypass device comprises a third measuring unit which is designed to detect a flow rate, in particular a volume flow of the return flow of the processing fluid flowing through the bypass device

[0071] Preferably, the control device is configured to control the hydraulic device in additional dependence on an actual value of the flow rate of the return flow detected by the third measuring unit.

[0072] In particular, the control device is designed to adjust an operating parameter of the pump that determines the delivery rate and / or an operating parameter of the flow regulating means of the bypass device that determines the return flow in additional dependence on the detected actual value of the flow rate of the return flow.

[0073] In this way, the control system also has information about the return flow in the bypass device, which can be taken into account during control.

[0074] Preferably, the measuring range of the third measuring unit is a range from 0 to 30 1 / min, preferably a range from 0.01 to 15 1 / min, and particularly preferably 0.01 to 10 1 / min. Preferably, the absolute maximum measurement deviation of the third measuring unit in its measuring range is less than or equal to 3 1 / min, more preferably less than or equal to 1.5 1 / min, more preferably less than or equal to 0.75 1 / min, and particularly preferably less than or equal to 0.1 1 / min.

[0075] In a preferred embodiment, the at least one fluid consumer is a tool interface for receiving a tool having at least one internal fluid channel The tool interface is configured to introduce the machining fluid directed thereto into the tool accommodated in the tool interface or into its at least one fluid channel, and to supply the machining fluid to the work space via this channel. This corresponds to the previously described concept of internal coolant supply, through which the machining fluid is dispensed particularly close to the machining area and additionally cools the tool from the inside.

[0076] The tool interface can be designed to accommodate or hold one or more different tool types, for example milling and / or drilling tools, turning tools or grinding tools with internal coolant supply.

[0077] Alternatively, the at least one fluid consumer can also be a tool holder interface for receiving a tool holder, into which a tool can be received. The tool holder comprises at least one internal fluid channel, wherein the tool holder interface is configured to introduce the machining fluid directed thereto into the tool holder or into its at least one fluid channel and to supply the machining fluid to the work space via said fluid channel. In this way, the supply takes place via the tool holder if a tool is used for machining that does not have any fluid channels of its own.

[0078] In a preferred embodiment, the tool interface is designed as a work spindle, via which a mounted tool can be driven in rotation.

[0079] In a preferred embodiment, the setpoint generator is configured to set or determine the setpoint for the flow rate applied to the fluid consumer or the tool interface depending on the tool accommodated therein, in particular depending on a tool parameter. This tool parameter is preferably taken from a tool database and can correspond to a nominal, tool-specific setpoint flow rate or a setpoint volume flow. This tool parameter is preferably taken from a pump characteristic curve of the accommodated tool stored in the tool database.

[0080] This allows control based on the flow rate or volume flow determined in advance as optimal for a specific tool. Optimal can be defined as an operating state with minimal power loss at the tool while maintaining a minimum amount of supplied machining fluid. This minimum amount can also be tool-specific and predetermined.

[0081] In a preferred embodiment, the setpoint generator is configured to determine the setpoint additionally or alternatively as a function of at least one machining parameter of the workpiece machining present at the control device.

[0082] This allows a flow rate control to be implemented that is adapted to a specific processing step, in which the amount of processing fluid supplied is oriented towards the processing in order to prevent under- as well as oversupply.

[0083] Preferably, the machining parameter is a cutting speed of the tool, a feed rate of the tool or a penetration depth of the tool into the workpiece to be machined.

[0084] In a preferred embodiment, the control device is further designed for process monitoring of a workpiece machining in the work space and, in this context, is configured to adapt at least one machining parameter of the workpiece machining as a function of the detected first and / or the detected second actual value, or as a function of the determined resulting flow rate value.

[0085] Preferably, the adjustable machining parameters are a machining speed of the tool and / or of the workpiece to be machined, which may be, for example, a cutting speed of the tool relative to the workpiece or a feed speed of the tool relative to the workpiece or a cutting or contact force between the workpiece and the tool.

[0086] The actual values ​​recorded by the measuring units provide information about the amount of machining fluid supplied during workpiece machining, which can be used as a starting point for detecting an unfavorable or even abnormal operating condition. For example, the actual values ​​can provide information about excessively fast feed rates or insufficient cutting speeds. Abnormal conditions can include, among other things, tool damage (as this can impede the supply of machining fluid) or insufficient removal of material chips (as these can block the supply of machining fluid), both of which lead to a machining quality that is poorer than "normal."

[0087] In a preferred embodiment, the control device is further configured, during the process monitoring, to instruct a machine stop of the machine tool if the detected first actual value lies outside a predetermined first target range and / or the detected second actual value lies outside a second predetermined target range.

[0088] This can prevent potentially costly damage to the tool and / or workpiece before it occurs.

[0089] Preferably, the target ranges are determined depending on the specified target value, in particular based on a maximum permissible relative deviation, for example, ±75%, ±50%, or ±25%. Alternatively, the target ranges can also be defined by explicit limit values.

[0090] Preferably, an effective value can also be determined from the two actual values, which is used in the course of the process monitoring described above.

[0091] Preferably, the hydraulic device comprises a temperature measuring unit associated with the inlet for detecting a temperature of the machining fluid and / or a pressure measuring unit associated with the inlet for detecting a pressure of the machining fluid. These are coupled to the control device, wherein the control of the machine tool optionally takes place in addition depending on the values ​​detected by said measuring units, thus further improving the control of the flow rate or improving process monitoring, in particular the detection of abnormal operating conditions.

[0092] According to a second aspect of the invention, a hydraulic device of a machine tool according to the first aspect or a preferred embodiment of the machine tool is provided

[0093] In this way, an existing machine tool can be supplemented with the hydraulic device in order to obtain the machine tool according to the invention without having to provide a completely new machine tool.

[0094] According to a third aspect of the invention, a hydraulic system for use on a machine tool is provided, which comprises a hydraulic device which is configured to supply at least one fluid consumer of the machine tool with a machining fluid for machining a workpiece, and a control device. The hydraulic device in turn comprises a pump for conveying the machining fluid, an inlet via which machining fluid conveyed by the pump is guided to the at least one fluid consumer, and a flow measuring device assigned to the inlet, which comprises at least a first measuring unit and a second measuring unit, which are each configured to detect a flow rate of the machining fluid in the inlet.The control device is at least configured to control the hydraulic device as a function of a first actual value detected by the first measuring unit and / or a second actual value of the flow rate of the processing fluid detected by the second measuring unit, in particular by setting an operating parameter of the pump that determines a delivery rate.

[0095] This provides the possibility of retrofitting existing machine tools with a hydraulic device including its own control device.

[0096] In contrast to the provision of the hydraulic device according to the second aspect, an independent hydraulic system with its own control device is thus provided in the event that an existing control device of the machine tool, for example, should not or cannot be used to control the hydraulic device (e.g. due to incompatibilities in data exchange or the like).

[0097] The hydraulic device of the hydraulic system can be designed according to any hydraulic device described in the above-described embodiments of the machine tool, so that a repeated description is omitted here.

[0098] The control device of the hydraulic system can have the same functionalities as the control device of the machine tool described above with regard to the hydraulic device of the machine tool.

[0099] Preferably, the control device of the hydraulic system corresponds to a control device of a machine tool, so that the hydraulic system according to the third aspect basically corresponds to a combination of the hydraulic device and the control device of the machine tool according to the first aspect of the invention.

[0100] Alternatively to the above embodiment, the control device of the hydraulic system can also be provided separately and in particular coupled to a control device of a machine tool for data and signal transmission, so that the control devices can access each other's data for the purpose of control.

[0101] Preferably, the hydraulic system comprises a setpoint generator via which a setpoint of a flow rate or volume flow of the processing fluid applied to the at least one fluid consumer is provided. Preferably, this setpoint generator is designed as part of the control device of the hydraulic system.

[0102] Preferably, the control device of the hydraulic system is designed to To control the hydraulic device as a function of the setpoint provided by the setpoint generator and the detected first actual value and / or the detected second actual value, in particular to control the flow rate applied to at least one fluid consumer.

[0103] Preferably, the control device of the hydraulic system is arranged to To set the operating parameters of the pump of the hydraulic device which determine the delivery rate, in particular a delivery rate or a speed of the pump, as a function of the provided setpoint value and the detected first actual value and / or the detected second actual value.

[0104] In the event that the hydraulic device comprises a bypass device, the control device of the hydraulic system is preferably designed to control the bypass device, in particular to adjust one of the operating parameters of a flow regulating means of the bypass device that determines the return flow through the bypass device.

[0105] According to a fourth aspect of the invention, a method for machining a workpiece by means of a machine tool is provided, in particular by means of a machine tool according to the first aspect or a preferred embodiment in this regard. The method comprises at least supplying the machining fluid into a Working space of the machine tool via at least one fluid consumer of the machine tool, in turn comprising operating a pump for conveying the machining fluid via an inlet to the at least one fluid consumer, detecting a first actual value of the flow rate, in particular the volume flow of the machining fluid at a first point of the inlet, detecting a second actual value of the flow rate, in particular the volume flow of the machining fluid at a second point of the inlet and controlling the machine tool for machining the workpiece as a function of the detected first actual value and / or the detected second actual value, wherein the above steps are each carried out at least before and / or during a machining operation of a workpiece placed in the working space by a tool of the machine tool.

[0106] This provides a method for machining a workpiece that is also characterized by the advantages in machining workpieces already described above in connection with the machine tool according to the invention, which will not be repeated here. The same applies to the preferred embodiments of the method described below, which correspond to the respective preferred embodiments of the machine tool.

[0107] The machine tool can be configured to drive the tool and / or the workpiece during machining.

[0108] Preferably, the first point and the second point of the inlet are arranged in series with respect to a flow direction of the processing fluid.

[0109] Preferably, the first actual value is recorded using a first measuring unit, and the second actual value is recorded using a second measuring unit, whose respective measuring ranges differ from one another. The statements regarding the measuring ranges and measurement deviations made with regard to the machine tool also apply here.

[0110] Preferably, the pump is operated in a volume flow operating range of the pump, which is preferably a range from 1 to 501 / min, and preferably from 5 to 40 1 / min.

[0111] In a preferred embodiment, the method comprises providing a setpoint value for a flow rate of the machining fluid applied to the at least one fluid consumer during workpiece machining, wherein the control of the machine tool takes place in additional dependence on the provided setpoint value.

[0112] Preferably, the method further comprises selecting one of the two detected actual values ​​as the reference value, wherein the control of the machine tool takes place as a function of the selected reference value.

[0113] Alternatively, the method may comprise determining a resulting flow rate value based on the detected first and second actual values. Preferably, the determination is performed by weighted averaging of the two detected actual values, with the weighting factors used to weight the actual values ​​during the averaging process themselves preferably being dependent on one or both of the detected actual values.

[0114] Preferably, the fluid consumer is a tool interface for receiving a tool with an internal fluid channel, as described above.

[0115] Providing the setpoint preferably comprises setting the setpoint as a function of the tool accommodated therein, in particular as a function of a tool parameter. Providing the setpoint preferably comprises reading a tool parameter from a tool database, in particular a nominal setpoint flow rate or a setpoint volume flow of the accommodated tool.

[0116] Preferably, the reading of the tool parameter comprises reading from a pump characteristic curve of the recorded tool stored in the tool database.

[0117] Preferably, providing the setpoint additionally or alternatively comprises setting the setpoint as a function of at least one machining parameter of the workpiece machining. For this purpose, providing the setpoint preferably comprises reading one or more machining parameters of the workpiece machining from a control device of the machine tool, in particular a cutting speed of the tool, a feed rate of the tool, or a penetration depth of the tool into the workpiece to be machined.

[0118] Preferably, controlling the machine tool further comprises adjusting at least one machining parameter of the workpiece machining on a control device of the machine tool as a function of the detected first and / or the detected second actual value. Preferably, the at least one machining parameter to be adjusted is a machining speed of the tool and / or of the workpiece to be machined, in particular a cutting speed of the tool relative to the workpiece or a feed rate of the tool relative to the workpiece or a cutting or contact force between the tool and the workpiece.

[0119] In a preferred embodiment, the control of the machine tool further comprises controlling the flow rate applied to the at least one fluid consumer, in particular the volume flow of the machining fluid, as a function of the provided setpoint value and the detected first actual value and / or the detected second actual value, preferably again comprising setting an operating parameter of the pump that determines the delivery rate as a function of the provided setpoint value and the detected first actual value and / or the detected second actual value.

[0120] Further aspects and their advantages as well as more specific embodiments of the aforementioned aspects and embodiments are described below with the aid of the drawings shown in the attached figures.

[0121] Fig. 1 shows a schematic view of a first embodiment of the machine tool according to the invention.

[0122] Fig. 2 shows a schematic view of a second embodiment of the machine tool according to the invention.

[0123] Fig. 3 shows a schematic view of a third embodiment of the machine tool according to the invention in two alternatives according to Fig. 3A and Fig. 3B.

[0124] Fig. 4 shows a schematic flow diagram of an embodiment of the method according to the invention for machining a workpiece.

[0125] Fig. 5 shows pump characteristics and operating points for various tools for use in the machine tool according to the invention with internal coolant supply.

[0126] Fig. 6 shows measurement results of hydraulic quantities when using the invention during workpiece machining using an internal coolant supply through the hydraulic device.

[0127] Fig. 7 shows measurement results for tool wear when using the invention for workpiece machining using an internal coolant supply through the hydraulic device.

[0128] Fig. 8 shows a table with machining results when using the invention during workpiece machining using an internal coolant supply through the hydraulic device.

[0129] It is emphasized that the present invention is in no way limited to the exemplary embodiments described below and their embodiment features. The invention further comprises modifications of the aforementioned exemplary embodiments, in particular those which result from modifications and / or combinations of individual or multiple features of the described exemplary embodiments within the scope of protection of the independent claims. Detailed character description

[0130] Fig. 1 shows a schematic view of a first embodiment of the machine tool 1000 according to the invention.

[0131] The machine tool 1000 comprises a work space 1 in which the machining of a workpiece 1002 takes place, a work spindle 2 as a fluid consumer in which a tool 1001 can be accommodated and driven in rotation, a hydraulic device 3 which is configured to supply the work spindle 2 with a cooling lubricant (KSS), and a control device 4 which is configured to control the machine tool 1000.

[0132] Cooling lubricant for workpiece machining can be supplied to the work chamber 1 via the fluid consumer embodied as the work spindle 2. The work spindle 2 corresponds to a tool interface via which a tool 1001 accommodated therein, having at least one internal fluid channel, can be supplied with cooling lubricant in such a way that the cooling lubricant is supplied to the work chamber 1 via the at least one fluid channel of the tool 1001, thus implementing the concept of internal cooling lubricant supply.

[0133] The work spindle 2 is supplied with coolant for the internal coolant supply via the hydraulic device 3, which comprises a tank 11 in which the coolant is provided, a pump 32 for conveying the coolant, and an inlet 35 through which the coolant is fed from the pump 32 to the work spindle 2. A pressure relief valve 33 protects the hydraulic device 3 from damage if the pump 32 is delivering and a volume flow through the inlet 35 is blocked.

[0134] The coolant supplied to the machine tool 1000 is collected and fed back to the tank 31 through an outlet 36 of the hydraulic device, which includes an outlet filter 361.

[0135] The hydraulic device may further comprise a pressure sensor 352 and / or a temperature sensor 353 at the inlet 35, as shown in Fig. 1, thereby enabling a comprehensive description of the state of the cooling lubricant in the inlet 35 in the way of and for use in the control.

[0136] Furthermore, the hydraulic device 3 comprises a volume flow measuring device 351 assigned to the inlet, which comprises a first volume flow sensor 351a and a second volume flow sensor 351b, which are arranged in series with respect to the flow direction of the cooling lubricant in the inlet 35 and are each configured to detect a volume flow of the cooling lubricant in the inlet 35.

[0137] Preferably, the two volume flow sensors 351a and 351b have different measuring ranges, each of which is not a subset of the other, so that the measuring ranges complement each other to enable reliable detection of a volume flow in the inlet 35 with the smallest possible measurement deviation, at least over the entire volume flow operating range of the pump 32. Preferred values ​​of the measuring ranges can be found in the above summary.

[0138] The control device 4 is coupled to the hydraulic device 3 and is coupled to at least the two volume flow sensors 351a, 351b

[0139] Furthermore, the control device 4 in the present embodiment is configured to control the hydraulic device 3 or to control a coolant flow rate applied to the work spindle 2 during the machining of the workpiece 1002. For this purpose, the control device 4 comprises a setpoint generator 41, via which a setpoint value of the coolant flow rate applied to the work spindle 2 is provided.

[0140] Optionally or additionally, the control device 4 can also be connected to other actuators of the machine tool, for example to a drive of the work spindle 2.

[0141] The setpoint can be set manually by a machine operator on the setpoint generator 41. Alternatively or additionally, the setpoint generator 41 can be configured to access a tool parameter of the tool 1001 stored in a memory device 43 of the control device and to determine the setpoint on the basis of this parameter. Alternatively or additionally, the setpoint generator 41 can be configured to access a tool database via a data interface 42 of the control device 4 and read out a tool parameter of the tool 1001 there and to determine the setpoint on the basis of this parameter. Alternatively or additionally, the setpoint can be transmitted to the setpoint generator 41 via the data interface 42.

[0142] The control device 4 is coupled to the pump 32 of the hydraulic device 3 for the purpose of implementing a volume flow control and is designed to control an operating parameter of the pump 32, in particular a speed, which determines the delivery rate, as a function of the setpoint value provided by the setpoint generator 41, a first actual value detected by the first volume flow sensor 351a and / or a second actual value of the volume flow of the cooling lubricant in the inlet 35 detected by the second volume flow sensor 351b.

[0143] The described design of the machine tool 1000 or the hydraulic device 3 thus allows for reliable volume flow control when supplying the work spindle 2 with coolant during machining, regardless of the fluid mechanics properties of a tool 1001 accommodated therein. This volume flow control, which is possible for a large number of tools, successfully avoids the disadvantageous operating conditions with "excessively high" pressure that occur in the prior art during pressure control. This allows for significantly reducing the stress on the hydraulic device 3 and the power loss occurring within it, which in turn reduces the energy costs during operation of the machine tool 1000 and increases the service life of the hydraulic device 3 itself.

[0144] A combination of hydraulic device 3 and control device 4 of the machine tool 1000 in Fig. 1 also corresponds to an embodiment of the hydraulic system according to the invention, since the control device 4 of the machine tool 1000 there is configured at least to control the hydraulic device 3.

[0145] As an alternative to the structure shown in Fig. 1, a separate control device for the hydraulic device can also be provided (not shown), which in turn can be coupled to a control device of the machine tool, which is designed to control other actuators of the machine tool

[0146] Fig. 2 shows a schematic view of a second embodiment of the machine tool 1000 according to the invention.

[0147] The second embodiment largely corresponds to the first embodiment and differs from it by a bypass 34 arranged between inlet 35 and pump 32, through which at least a portion of the coolant pumped by pump 32 can be directed as a return flow to tank 31. This also allows volume flows to be provided in inlet 35 that are below a minimum volume flow of pump 32.

[0148] In this case, the bypass 34 comprises a flow regulating means designed as a controllable throttle valve 342, via which a flow through the bypass can be regulated, e.g., by adjusting a degree of opening of the throttle valve to adjust a flow resistance in the bypass 34.

[0149] Furthermore, the bypass comprises its own third volume flow sensor 341, which is designed to detect the volume flow of the return flow in the bypass 34

[0150] The volume flow provided by the pump 32 results from the sum of the volume flows in the inlet 35 and in the bypass 34, which can be detected by the respective sensors 341, 351a, 351b.

[0151] Preferably, the control device is configured to control an operating parameter of the flow regulating means that determines the backflow as a function of the detected first and / or the detected second actual value, or as a function of the determined resulting volume flow value, and / or the provided setpoint value, in particular to control the volume flow applied to the at least one fluid consumer.

[0152] Both the throttle valve 342 and the third volume flow sensor 341 are coupled to the control device 4. For the purpose of volume flow control in the inlet 35, the control device 4 is configured to control the hydraulic device 3 as a function of a detected first actual value of the first volume flow sensor 351a and / or a detected second actual value of the second volume flow sensor 351b and / or a detected third actual value of the third volume flow sensor 341 and the setpoint provided by the setpoint generator 41.

[0153] For this purpose, the control device 4 is set up to determine an operating parameter of the pump 32 which determines the delivery rate and / or an operating parameter of the throttle valve 342 in the bypass 34 which determines the return flow in the above-described dependency in particular to control the volume flow applied to the work spindle 2 during workpiece machining.

[0154] Fig. 3 shows a schematic view of a third embodiment of the machine tool 1000 according to the invention in two alternatives according to Figs. 3A and 3B.

[0155] The two alternatives of the third embodiment largely correspond to the second embodiment. For the sake of simplicity, the left-hand section, which is identical to that of Fig. 2, has been omitted in Figs. 3A and 3B.

[0156] The alternatives of the third embodiment differ from the second embodiment by the use of an inlet filter 354 in the inlet 35, which in Fig. 3A is arranged downstream of the volume flow measuring device 351 in the flow direction and in Fig. 3B upstream of the volume flow measuring device 351 in the flow direction. Furthermore, the machine tool 1000 is not equipped with the optional pressure and temperature sensors in the inlet 35. The inlet filter 354 can optionally comprise the check valve shown in Figs. 3A and 3B.

[0157] The inlet filter 354 can be used to remove impurities in the coolant before it is fed in, which could, for example, have a negative effect on the machining or, under certain circumstances, even clog the fluid channels of the tool 1001.

[0158] The inventors have discovered that, in particular, the arrangement of the volume flow measuring device 351 downstream of the inlet filter 354 according to Fig. 3B achieves the best results for volume flow control on the work spindle 2, since, among other things, no further components, such as the aforementioned inlet filter 354, which could affect the already measured coolant flow, are arranged between the measuring point and the control point on the fluid consumer or the work spindle 2. This is particularly advantageous if the inlet filter 354, as shown in Figs. 3A and 3B, is designed with a check valve, through which a portion of the already measured coolant flow is diverted under certain circumstances before being fed to the work spindle 2.

[0159] Furthermore, the inlet filter 354 can also be arranged between the pump and the branch shown in Fig. 2 into the bypass 34, which further improves the measurement results of the backflow in the bypass 34.

[0160] Said inlet filter 354 can, of course, also be used analogously in the embodiment without bypass 34 from Fig. 1 in the embodiments according to Fig. 3A and 3B.

[0161] Fig. 4 shows a schematic flow diagram of an embodiment of the method according to the invention for machining a workpiece on a machine tool using a machining fluid, in particular a cooling lubricant.

[0162] In step SI, a setpoint value is provided for a flow rate, for example a volume flow, of the machining fluid applied to a fluid consumer during workpiece machining.

[0163] In step S2, the machining fluid is supplied into a working space of the machine tool via the fluid consumer, comprising the sub-step S2.1 of operating a pump for conveying the machining fluid via an inlet to the fluid consumer.

[0164] In step S3, a first actual value of the flow rate of the processing fluid is recorded at a first point of the inlet.

[0165] In step S4, a second actual value of the flow rate of the processing fluid is recorded at a second point of the inlet.

[0166] In step S5, the machine tool for machining the workpiece is controlled as a function of the setpoint value provided from step S1, the detected first actual value from step S3 and / or the detected second actual value from step S4, comprising the sub-step S5.1 of setting an operating parameter of the pump that determines a delivery rate, in particular the speed, as a function of the setpoint value provided and the detected first actual value and / or the detected second actual value.

[0167] All of the above steps are carried out at least before and / or during machining of a workpiece placed in the work area by a tool held by the machine tool.

[0168] Fig. 5 shows exemplary pump characteristics and operating points for various tools W1 to W6 for use in the machine tool according to the invention with internal coolant supply.

[0169] The pump characteristics here correspond to tool-specific performance curves of a pump of a hydraulic device designed for the internal coolant supply as a function of the volume flow of the coolant provided by the pump without the use of a bypass.

[0170] Data for the corresponding tools W1 to W6 can be found in the following table.

[0171] The performance curves all show an essentially exponential dependence of performance on the volume flow rate. A slight change in the volume flow rate thus leads to a significant change in performance and thus also to a significant change in the energy costs incurred during operation.

[0172] As an example, the applied pressures are also indicated at designated points on the pump characteristic curve for W5. For example, at a flow rate of 29 l / min, a pressure of 80 bar is present, at a flow rate of 20.6 l / min, a pressure of 40 bar is present, and at a flow rate of 13.5 l / min, a pressure of 17 bar is present. Starting from the top data point, it can be seen that halving the pressure only leads to a decrease of approximately 29% in the flow rate, but already to a decrease of approximately 64% in the power. A flow rate of 20.6 l / min for the W5 tool is already more than sufficient for workpiece machining, which also results in significantly lower pressure and thus significantly lower load on the hydraulic device.

[0173] The pump characteristics of tools W1 to W6 illustrate the problem of pure pressure control, where a high pressure is set at the pump on suspicion to avoid the risk of a cooling lubricant undersupply. This strategy typically leads to unnecessary energy costs and overloading of the hydraulic device, even though operation with a significantly lower pressure and thus lower pump performance already results in a sufficient cooling lubricant supply for a specific tool.

[0174] The move away from the pressure control known in the prior art to a volume flow control is made possible by the present invention

[0175] Said pump characteristic curves can be provided to the control device of the machine tool, for example in a storage device and / or via an interface in an external tool management database.

[0176] Fig. 6 shows measurement results of hydraulic quantities when using the invention during workpiece machining using an internal coolant supply through the hydraulic device.

[0177] Fig. 6 shows a comparison of hydraulic parameters of a conventional pressure control (upper diagram) and the inventive flow control (lower diagram) when drilling a hole in a workpiece with a tool according to W2 (drill). Other parameters of the workpiece machining were: Workpiece material: AISI 316 (austenitic chromium-nickel-molybdenum steel) Cutting speed: 50 m / min Feed per tooth: 0.1 mm Depth of hole: 180 mm

[0178] The penetration depth into the workpiece is proportional to the time, since a constant feed rate was selected.

[0179] Both diagrams show the temporal progression of the pressure p applied to the drill during workpiece machining and the flow rate Q of the coolant. For pressure control, a setpoint pressure of 50 bar is specified, whereas for flow control, a setpoint flow rate of 2 l / min is specified.

[0180] As can be seen from the diagram above, the pressure p can be kept almost constant at 50 bar, whereby the resulting volume flow Q is subject to strong fluctuations with a comparatively high frequency. It fluctuates around an average value Q*~2.1 1 / min in a range from a minimum of Qmin«0.5 1 / min to a maximum of Q ma x~3.8 rpm by approximately 3.3 rpm. The volume flow Q at the drill, implemented by the pressure control, is highly volatile and affects the machining quality of the workpiece, which therefore also fluctuates and leads to uneven machining results.

[0181] In contrast, the lower diagram shows an extremely stable flow rate Q with smaller fluctuations. It fluctuates around an average value Q*~2.0 1 / min within a range from a minimum of Qmin~1.0 1 / min to a maximum of Qmax~3.0 1 / min by approximately 2.0 1 / min. The pressure curve shows that, to maintain the setpoint flow rate Q of 2.0 1 / min, the pressure p increases almost linearly with increasing penetration depth from approximately 35 bar to 45 bar.

[0182] Thus, flow control provides a coolant supply with virtually the same average flow rate and lower fluctuations than pressure control. At the same time, the pressure is consistently lower, resulting in lower energy costs and lower stress on the hydraulic components, thus increasing their service life compared to pressure control.

[0183] The measurement results discussed above demonstrate the advantages of volume flow control in machining workpieces, which can only be reliably implemented by the inventive design of the machine tool or the hydraulic device with two measuring units.

[0184] Fig. 7 shows measurement results for tool wear when using the invention for workpiece machining using an internal coolant supply through the hydraulic device.

[0185] The diagram in Fig. 7 shows a comparison of the temporal progression of tool wear for conventional pressure control and the inventive flow control when milling a flank, each with a W5 tool (milling cutter). Other workpiece machining parameters were: Workpiece material: T1A16V4 Cutting speed: 75 m / min Feed per tooth: 0.12 mm Width and depth of removal: 10 mm and 5 mm

[0186] The diagram shows the tool wear over the lifetime of the milling cutters in minutes, with the workpiece machining being carried out in one case with conventional pressure control with a setpoint pressure p of 80 bar and in the other case with the inventive volume flow control with a setpoint volume flow Q of 13.4 1 / min. The degree of tool wear is determined by specifying the width of the worn area of ​​the tool's flank in pm.

[0187] As can be seen from the diagram, tool wear initially increases approximately equally for the pressure and flow rate control cases. However, tool wear in the pressure control case experiences a significant increase over time, and toward the end, it clearly differs from the tool wear in the flow rate control case.

[0188] The volume flow control according to the invention therefore also has a positive effect on tool wear, so that tools can be used longer and need to be replaced less often, which in turn leads to lower operating costs.

[0189] Furthermore, the diagram also shows the average performance values ​​of the pump for supplying the tool with coolant for the two cases, which differ by approximately a factor of 10, so that the volume flow control according to the invention also leads to significant energy savings compared to conventional pressure control.

[0190] Furthermore, the inventors have found that the use of volume flow control also leads to better machining results compared to conventional volume flow control, as can be seen from the table shown in Fig. 8.

[0191] The table in Fig. 8 shows a comparison of the average surface roughness Ra achieved on the workpiece after machining with a drill according to W4 and a milling cutter according to W5 with the respective machining parameters specified, in each case using the conventional pressure control and the volume flow control according to the invention.

[0192] For both tools, lower surface roughness was achieved in the case of volume flow control with otherwise identical machining parameters, thus a better surface quality of the workpiece could also be achieved by using volume flow control.

[0193] Thus, the volume flow control according to the invention also offers advantages in terms of processing quality.

[0194] Embodiments of the present invention and their advantages have been described in detail above with reference to the accompanying figures.

[0195] It is emphasized again that the present invention is in no way limited to the embodiments and their features described above.

[0196] The invention further includes modifications of the above-mentioned Embodiments, in particular those resulting from modifications and / or combinations of the features of the described embodiments within the scope of protection of the independent claims. List of reference symbols 1 workroom 2 Work spindle as tool interface (fluid consumer) 3 Hydraulic device 4 Control device of the machine tool 31 tanks 32 Pump 33 Pressure relief valve 34 Bypass 35 inlet 36 Process 341 third volume flow sensor (bypass) 342 controllable throttle valve 351 Volume flow measuring device 351a, 351b first, second volume flow sensor (volume flow measuring device) 352 pressure sensor 353 Temperature sensor 354 inlet filter 361 drain filter 41 setpoint transmitter 42 Data interface 43 Storage device 1000 machine tools 1001 tools 1002 workpiece

Claims

CLAIMS 1. A machine tool (1000) for machining workpieces, comprising: a work chamber (1); at least one fluid consumer (2), via which a machining fluid for machining the workpiece, in particular a cooling lubricant, can be supplied to the work chamber (1); a hydraulic device (3) configured to supply the at least one fluid consumer (2) with the machining fluid, again comprising: - a pump (32) for conveying the machining fluid; - an inlet (35) via which the processing fluid delivered by the pump (32) is fed to the at least one fluid consumer (2); and - a flow measuring device (351) associated with the inlet (35), which comprises at least a first measuring unit and a second measuring unit, each configured to detect a flow rate of the machining fluid in the inlet (35); and a control device (4) for controlling the machine tool (1000), which is configured to control the machine tool (1000), in particular the hydraulic device (3), as a function of a first actual value detected by the first measuring unit (351a) and / or a second actual value detected by the second measuring unit (351b), of the flow rate of the machining fluid in the inlet (35).

2. Machine tool (1000) according to claim 1, wherein the flow measuring device is a volume flow measuring device (351), so that the flow rate in the inlet (35) is indicated by a volume flow.

3. Machine tool (1000) according to claim 1 or 2, wherein the first measuring unit (351a) and the second measuring unit (351b) are arranged in series with respect to a flow direction of the machining fluid in the inlet (35).

4. Machine tool (1000) according to at least one of the preceding claims, wherein a measuring range of the first measuring unit (351a) differs from a measuring range of the second measuring unit (351b), in particular neither of the two measuring ranges is a subset of the respective other measuring range.

5. Machine tool (1000) at least according to claim 4, wherein the measuring range of the first measuring unit (351a) and the measuring range of the second measuring unit (351b) overlap in an overlap region.

6. Machine tool (1000) according to at least claim 2 and claim 5, wherein the measuring range of the first measuring unit (351a) is a range from 0 to 30 rpm, preferably a range from 0.01 to 15 rpm; and the measuring range of the second measuring unit (351b) is a range from 1 to 80 rpm, preferably a range from 1 to 50 rpm.

7. Machine tool (1000) at least according to claim 2 and claim 5, wherein the measuring ranges of the first and the second measuring unit (351a, 351b) and a minimum volume flow of the pump (32) are adapted to one another in such a way that the minimum volume flow lies in the overlap range 8. Machine tool (1000) at least according to claim 2 and one of claims 3 to 7, wherein a volume flow operating range of the pump (32) is a subset of a union of the measuring ranges of the first and the second measuring unit (351a, 351b) 9. Machine tool (1000) at least according to claim 8, wherein the volume flow operating range of the pump (32) is a range from 0.1 to 80 1 / min, preferably from 5 to 40 1 / min.

10. Machine tool (1000) according to at least one of the preceding claims, wherein the machine tool (1000) further comprises a setpoint generator (41) via which a setpoint of a flow rate of the machining fluid present at the at least one fluid consumer (2) is provided, wherein the control device (4) is configured to control the hydraulic device (3) as a function of the provided setpoint and the detected first actual value and / or the detected second actual value, in particular in order to control the flow rate present at the at least one fluid consumer (2).

11. Machine tool (1000) at least according to claim 10, wherein the control device (4) is configured to determine an operating parameter of the pump (32) of the hydraulic device (3) which determines the delivery rate, in particular a To set a flow rate or a speed of the pump (32) as a function of the provided setpoint and the detected first actual value and / or the detected second actual value.

12. Machine tool (1000) according to at least one of the preceding claims, wherein the hydraulic device (3) further comprises a bypass device (34) arranged between the inlet (35) and the pump (32).

13. Machine tool (1000) at least according to claim 12, wherein the bypass device (34) comprises at least one flow regulating means (342) via which a flow of a return flow of the machining fluid flowing through the bypass device (34) can be regulated, in particular a controllable bypass valve (342) or a controllable bypass pump.

14. Machine tool (1000) at least according to claim 10 and claim 13, wherein the bypass device (34) comprises a third measuring unit (341) which is configured to detect a flow rate of the return flow of the machining fluid flowing through the bypass device (34), and wherein the control device (4) is configured to control the hydraulic device (3) in additional dependence on an actual value of the flow rate of the return flow detected by the third measuring unit (341).

15. Machine tool (1000) according to at least one of the preceding claims, wherein the at least one fluid consumer is a tool interface (2) for receiving a tool (1001) with at least one internal fluid channel, wherein the tool interface (2) is configured to supply the machining fluid directed thereto to the working space (1) via the at least one fluid channel of the tool (1001) received in the tool interface (2).

16. Machine tool (1000) at least according to claim 15, wherein the tool interface is designed as a work spindle (2) for receiving and rotating a tool (1001).

17. Machine tool (1000) according to at least one of claims 15 or 16, wherein the setpoint generator (41) is configured to determine the setpoint as a function of a tool parameter of a tool (1001) accommodated in the tool interface (2) and / or as a function of at least one of the control devices (4) Machining parameter of the workpiece machining, which is in particular a cutting speed of the tool (1001), a feed speed of the tool (1001) or a penetration depth of the tool (1001) into the workpiece (1002) to be machined.

18. Machine tool (1000) according to at least one of the preceding claims, wherein the control device (4) is further designed for process monitoring of a workpiece machining in the work space (1) and in this context is set up to adapt at least one machining parameter of the workpiece machining as a function of the detected first and / or the detected second actual value, in particular a machining speed of the tool (1001) and / or of the workpiece (1002) to be machined.

19. Machine tool (1000) according to claim 18, wherein the control device (4) is further configured to instruct a machine stop of the machine tool (1000) if the detected first actual value is outside a predetermined first target range and / or the detected second actual value is outside a second predetermined target range 20. Hydraulic device (3) of a machine tool (1000) according to one of claims 1 to 19.

21. Hydraulic system for use on a machine tool (1000), comprising: a hydraulic device (3) which is configured to supply at least one fluid consumer (2) of the machine tool (1000) with a machining fluid for machining a workpiece, in turn comprising: - a pump (32) for conveying the machining fluid; - an inlet (35) via which the processing fluid delivered by the pump (32) is fed to the at least one fluid consumer (2); and - a flow measuring device (351) associated with the inlet (35), which comprises at least a first measuring unit (351a) and a second measuring unit (351b), each configured to detect a flow rate of the processing fluid in the inlet (35); and a control device (4) configured at least to control the hydraulic device (3) as a function of a first actual value detected by the first measuring unit (351a) and / or a second actual value of the flow rate of the processing fluid detected by the second measuring unit (351b), in particular by setting an operating parameter of the pump (32) which determines a delivery rate.

22. A method for machining a workpiece by means of a machine tool (1000), in particular by means of a machine tool according to at least one of claims 1 to 19, comprising the steps: Supplying the machining fluid into a working space (1) of the machine tool (1000) via at least one fluid consumer (2), again comprising: - operating a pump (32) for conveying the processing fluid via an inlet (35) to the at least one fluid consumer (2); Detecting a first actual value of the flow rate of the processing fluid at a first point of the inlet (35); Detecting a second actual value of the flow rate of the processing fluid at a second point of the inlet (35); and Controlling the machine tool (1000) for workpiece machining as a function of the detected first actual value and / or the detected second actual value; wherein the above steps are carried out at least before and / or during a machining operation of a workpiece (1002) placed in the work space (1) by a tool (1001) held by the machine tool (1000) 23. The method of claim 22, further comprising the step: Providing a setpoint value for a flow rate of the machining fluid applied to the at least one fluid consumer (2) during workpiece machining; wherein the control of the machine tool (1000) takes place in additional dependence on the provided setpoint value 24. The method of claim 23, wherein controlling the machine tool (1000) further comprises: Setting an operating parameter of the pump (32) which determines a delivery rate as a function of the provided setpoint value and the detected first actual value and / or the detected second actual value.

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