Method for compensating for a temperature-related change in length of a tool or tool unit on a machine tool, associated control device, machine tool, and computer program product

Abstract

Method for compensating a temperature-induced change in length of a drilling or milling tool (104) or a tool unit comprising the drilling or milling tool, which is interchangeably clamped on a tool spindle (102) of a machine tool (100), comprising: - determining a temperature value by means of a temperature sensor (116) arranged at a temperature measuring position of the tool spindle (102); - determining at least one compensation value depending on the determined temperature value; and - Compensating for the temperature-related change in length of the drilling or milling tool (104) or the tool unit on the basis of the at least one specific compensation value.

Description

[0001] The present invention relates to a method for compensating a temperature-induced change in length of a tool or a tool unit comprising the tool, which is clamped to a tool spindle of a machine tool.

[0002] Furthermore, the present invention relates to a control device for use on a machine tool with a tool spindle, a spindle device for use on a machine tool, a machine tool comprising a spindle device and a control device, and a computer program product. BACKGROUND OF THE INVENTION

[0003] When a workpiece is machined using a tool on a machine tool, a chip cut from the workpiece typically heats up at the point of separation due to internal friction. The tool then typically heats up due to friction, also through heat conduction from the chip and through friction against the workpiece at the cutting edges of the tool. Some of the generated heat can be dissipated in the chip. However, the portion of the generated heat that cannot be dissipated via the chip enters the tool, causing its temperature to rise.

[0004] The temperature change in the tool causes a change in the length of the clamped tool due to thermal expansion. This behavior can lead to deviations in the tool reference point, which is why it is desirable to compensate for temperature-related changes in the length of the tool or the tool unit comprising the tool.

[0005] For example, a targeted influence on the temperature-dependent behavior of the machining process can be achieved through controlled cooling. In this regard, European patent EP 0 855 946 B1 discloses a method for cooling and lubricating a cutting, rotating tool with a geometrically defined cutting edge and, if applicable, the workpiece in the machining area.

[0006] Furthermore, the temperature-dependent behavior of the machining process can be influenced by compensating for tool adjustment depending on specific parameters. In this context, it is known from EP 349 783 B1 that temperatures on the machine bed and on axis slides on machine tools can be determined in order to determine and compensate for temperature-dependent expansion or thermal deformation of the machine tool components. For temperature-dependent expansion, the entire temperature profile across the expanding machine part must be recorded. This is made possible by using a resistor that extends in the direction of expansion of the machine part and that has intensive thermal contact with the machine part. The resistor used has an output signal proportional to the average temperature and thus to the overall expansion.For contacting, appropriate contact elements are provided at both ends of the resistor.

[0007] DE 19155078 A1 relates to a machine with a temperature-compensated work spindle. A sensor is provided that detects the thermal radiation emitted by a work spindle shaft. The machine's control system takes the shaft's temperature change into account when controlling the positioning drives.

[0008] DE 19848642 A1 relates to a method for compensating temperature-related dimensional deviations in machine geometry. A coordination transformation using a mapping matrix is ​​proposed.

[0009] DE 10 2005 012105 A1 relates to a method and a control system for compensating positioning inaccuracies.

[0010] However, in the methods known from the prior art, it is not known how to determine or compensate for a temperature-related change in length of tools or tool units comprising tools (e.g. a tool unit comprising the tool and a tool holder holding the tool). SUMMARY OF THE INVENTION

[0011] In view of the above-described disadvantages of the methods known from the prior art, it is an object of the present invention to avoid the disadvantages of the prior art and to provide a method for compensating temperature-dependent length changes on a machine tool.

[0012] The present invention is achieved according to the invention as described in the independent claims by a method for compensating a temperature-induced change in length of a drilling or milling tool or a tool unit comprising the drilling or milling tool according to claim 1, a control device for use on a machine tool according to claim 17, a spindle device for use on a machine tool according to claim 18, and a computer program product according to claim 19. Features of preferred embodiments of the present invention are described in the dependent claims.

[0013] According to the present invention, a method for compensating for a temperature-dependent change in position on a machine tool, preferably with at least one first linear axis, comprises one or more of the following steps: determining a temperature value by means of a temperature sensor arranged at a temperature measuring position of the tool spindle, determining at least one compensation value as a function of the determined temperature value, and compensating for the temperature-dependent change in length of the drilling or milling tool interchangeably clamped on the spindle or of the tool unit interchangeably clamped on the spindle as a function of or on the basis of the at least one determined compensation value.

[0014] Thus, according to the invention, compensation for temperature-related length changes of the drilling or milling tool or tool unit is carried out as a function of or on the basis of at least one specific compensation value. In contrast to the prior art, the temperature of the clamped drilling or milling tool is included in the calculation of compensation values ​​for compensating for the temperature-related length change of the drilling or milling tool. This has the particular advantage of no longer being dependent on maintenance-intensive length measuring systems, i.e., compensation for temperature-dependent length changes of the drilling or milling tool or tool unit is now possible without having to calibrate length measuring systems in advance or otherwise laboriously adjust them prior to workpiece machining.

[0015] According to the present invention, which further preferably provides the step of transmitting sensor data indicating the determined temperature value from the temperature sensor arranged at the temperature measuring position of the tool spindle to a numerical control of the machine tool, the determination of the compensation value and / or the compensation of the temperature-related change in length of the drilling or milling tool or the tool unit can advantageously be carried out in the numerical control of the machine tool.

[0016] Preferably, the numerical control system can be configured to output respective control signals to drives of the linear and / or rotary axes of the machine tool for controlling a relative movement of the tool spindle relative to a workpiece clamped to the machine tool based on target positions of the linear and / or rotary axes of the machine tool. Compensating for the temperature-induced length change can thereby include adjusting at least one of the target positions of the linear and / or rotary axes of the machine tool. Thus, length changes of the drilling or milling tool due to thermal expansion can be compensated for by correcting or adjusting the target positions of the linear and / or rotary axes of the machine tool depending on the calculated compensation value.

[0017] Furthermore, the numerical control system can be configured to output respective control signals to drives of the linear and / or rotary axes of the machine tool for controlling a relative movement of the tool spindle relative to a workpiece clamped to the machine tool based on the target and actual positions of the linear and / or rotary axes of the machine tool. According to the present invention, it is possible to compensate for a temperature-related change in length of the drilling or milling tool or tool unit clamped to the machine tool by correcting or adjusting the actual positions of the linear and / or rotary axes of the machine tool depending on the calculated compensation value. This allows for improved compensation for a temperature-related change in length.

[0018] Preferably, the compensation for the temperature-related length change of the drilling or milling tool can be carried out in the numerical control of the machine tool in the direction of the spindle axis of the machine tool's tool spindle. This has the advantage that the method can be used on a machine tool in which the drilling or milling tool can be moved linearly in one direction.

[0019] Furthermore, compensating for the temperature-induced length change can involve adjusting at least one actual and / or target position of one or more linear and / or rotary axes of the machine tool in the direction of the spindle axis of the tool spindle of the machine tool. This allows the method to also be used in a machine tool in which the drilling or milling tool can be moved linearly in three directions and pivoted about one or more rotary axes.

[0020] Preferably, in the step of compensating for the temperature-related length change of the drilling or milling tool, a current angular orientation of the spindle axis of the tool spindle is first determined in the coordinate system of the machine tool. Subsequently, several compensation values, each assigned to a coordinate axis in the coordinate system of the machine tool, are determined depending on the determined temperature value and the determined current angular orientation of the spindle axis. The compensation of the temperature-related length change of the drilling or milling tool or the tool unit for the respective coordinate axes in the coordinate system of the machine tool is carried out depending on the compensation value assigned to the respective coordinate axis. This provides the advantage that the thermal expansion and deformation of a drilling or milling tool can be compensated particularly precisely.

[0021] According to the present invention, the steps of determining the temperature value, determining the at least one compensation value, and compensating for the temperature-related length change of the drilling or milling tool or tool unit can be performed repeatedly during the machining of a workpiece on the machine tool. This allows the temperature-related length change of the drilling or milling tool to be determined and compensated for during the machining of the workpiece.

[0022] Preferably, the determination of the at least one compensation value can be carried out on the basis of a temperature compensation calculation model, wherein the temperature compensation calculation model can be used to calculate the temperature-related change in length of the drilling or milling tool depending on the determined temperature value. The calculation of one or more compensation values ​​is thus advantageously carried out with the fastest possible time cycle in a control unit, e.g., the so-called machine NC (NC for "Numerical Control"), or the programmable logic controller (PLC), also called machine LC or machine PLC (PLC for "Programmable Logic Controller"). Temperature-dependent calculated compensation values ​​can then be superimposed by the control unit, the so-called machine NC, on one or more axis setpoints of the linear axes of the machine tool.

[0023] A preferred method is thus proposed in which the temperature-related change in length of a drilling or milling tool or a tool unit can be compensated for, preferably by determining one or more temperatures on the machine tool and by calculating one or more compensation values ​​determined for the specific temperature in the machine control system by superimposing the axis target positions in the machine control system. The calculated compensation value(s) are preferably used to correct the axis target positions of one or more linear axes of the machine tool in order to compensate for the temperature-related change in length of a drilling or milling tool in the direction of the axes.

[0024] Furthermore, the temperature compensation calculation model can be provided tool-specifically. Alternatively, the temperature compensation calculation model can also be provided tool-independently, whereby a tool-specific temperature coefficient and / or a tool-specific reference length of the drilling or milling tool at a reference temperature is incorporated into the temperature compensation calculation model.

[0025] Preferably, when a tool is changed on the machine tool, the tool-specific temperature compensation calculation model used to determine the at least one compensation value is changed on the numerical control of the machine tool in accordance with the replaced drilling or milling tool, or the tool-specific temperature coefficient used in the tool-independent temperature compensation calculation model and / or the tool-specific reference length of the drilling or milling tool used in the tool-independent temperature compensation calculation model is / are changed if the replaced drilling or milling tool is a drilling or milling tool that is different from the drilling or milling tool previously used.

[0026] Furthermore, during a tool change on the machine tool, the tool-specific temperature compensation calculation model applied to determine at least one compensation value can be reused on the numerical control of the machine tool, or the tool-specific temperature coefficient used in the tool-independent temperature compensation calculation model and / or the tool-specific reference length of the drilling or milling tool used in the tool-independent temperature compensation calculation model can be reused if the replaced drilling or milling tool is a sister tool of the same type as the previously used drilling or milling tool. This allows for compensation not only for the temperature-related change in length of the drilling or milling tool clamped in the tool spindle of the machine tool.The process can also compensate for the temperature-related change in length of a drilling or milling tool after any tool change, in particular after a sister tool of the same type as the previously used drilling or milling tool has been replaced.

[0027] Preferably, one or more tool-specific temperature compensation calculation models can be pre-stored on the numerical control of the machine tool. Alternatively, a tool-independent temperature compensation calculation model and one or more tool-specific parameter sets can be pre-stored, each of which includes the tool-specific temperature coefficient and / or the tool-specific reference length of the drilling or milling tool. Pre-storing the temperature compensation calculation models on the numerical control of the machine tool enables particularly rapid determination of the compensation values ​​for compensating for the temperature-related change in length of the drilling or milling tool. Thus, the data storage device of the numerically controlled machine tool is not written with data that slows down the execution of the method.

[0028] According to the present invention, one or more tool-specific compensation data sets can preferably be pre-stored on the control system of the machine tool, wherein each tool-specific compensation data set for a corresponding drilling or milling tool indicates respective associated compensation values ​​for a plurality of temperature values, wherein the determination of the at least one compensation value is carried out on the basis of one of the pre-stored compensation data sets.

[0029] Furthermore, the temperature sensor for determining the temperature value can be integrated into a tool spindle bearing of the tool spindle or arranged adjacent to the tool spindle bearing of the tool spindle. Thus, the method according to the invention does not require any additional measuring components that must be provided on or in the working space of the machine tool. By integrating the temperature sensor into the tool spindle bearing of the tool spindle or, alternatively, by arranging the temperature sensor adjacent to the tool spindle bearing of the tool spindle, a compact design of the tool spindle of the machine tool can be advantageously ensured.

[0030] Preferably, several temperature sensors can also be arranged on the tool spindle and the at least one compensation value can be determined as a function of several determined temperature values.

[0031] Finally, according to the present invention, a control device for use on a machine tool having a tool spindle with a temperature sensor arranged at a temperature measuring position of the tool spindle is provided, wherein the control device has a numerical control which is configured to carry out a method for compensating a temperature-induced change in length of a tool or a tool unit which is clamped in the tool spindle of the machine tool, according to one of the preceding claims, as a function of a temperature value determined by means of the temperature sensor.

[0032] Furthermore, the present invention also comprises the spindle device for use on a machine tool, a tool spindle with a temperature sensor arranged at a temperature measuring position of the tool spindle, and a transmission device for transmitting sensor data indicating the determined temperature value from the temperature sensor arranged at the temperature measuring position of the tool spindle to a numerical control of the machine tool.

[0033] Preferably, according to the present invention, a machine tool is also provided which comprises a spindle device and a control device as described above.

[0034] Finally, according to the present invention, a computer program product is provided with program means stored on a data carrier and adapted to be executed on a control device of a numerically controlled machine tool comprising a tool spindle for receiving a drilling or milling tool, such that a method of the present invention can be carried out on the machine tool. BRIEF DESCRIPTION OF THE CHARACTERS Fig. 1 shows, by way of example, a schematic representation of a machine tool on which the method according to the invention can be carried out in accordance with an embodiment of the invention. Fig. 2 shows an example of a comparison between a drilling or milling tool clamped in a tool spindle of a machine tool, which has experienced a temperature-related change in length, and a newly inserted, cold, identical sister tool. Fig. 3 shows an example schematic representation of a control device. Fig. 4 illustrates an example of a flow chart of a method for compensating a temperature-induced change in length of a drilling or milling tool according to an embodiment of the invention. Fig. 5 shows an example of a flow chart of a method for compensating a temperature-induced change in length of a drilling or milling tool according to a further embodiment of the invention. Fig. 6 shows an example flow chart of the method for compensating for a temperature-induced change in length of a drilling or milling tool when a tool change is carried out. DETAILED DESCRIPTION

[0035] In the following, preferred embodiments of the present invention are described in detail with reference to the accompanying figures. However, the present invention is not limited to the described embodiments. The present invention is defined by the scope of the patent claims. Identical or similar features of the embodiments are designated by the same reference numerals in the figures.

[0036] Fig. 1 shows an example of a schematic representation of a numerically controlled machine tool 100. In this case, the embodiment according to Fig. 1 a machine tool 100 with a tool-carrying spindle 102 according to an embodiment of the invention.

[0037] The illustrated machine tool 100 is used to perform milling and drilling operations on workpieces 106 using drilling or milling tools 104 that are clamped into the tool spindle 102. However, the method according to the invention can also be applied to machine tools designed for other manufacturing processes.

[0038] The machine tool 100 according to Fig. 1 also comprises a longitudinal bed 108, on which a machine table with clamping means 110 is arranged to be movable in the X direction, and a transverse bed 112, on which a spindle carrier 114 is arranged to be movable in the Y direction.

[0039] In addition to the two linear axes in the X and Z directions, further linear axes and rotary axes can be provided (not shown). The clamping means 110 is configured to clamp a workpiece 106. The spindle carrier 114 carries a tool-carrying spindle 102, in which a drilling or milling tool 104 or a tool holder holding the drilling or milling tool 104 is received. The combination of drilling or milling tool and tool holder can also be understood below as a tool unit that can be clamped to the spindle.

[0040] Furthermore, the numerically controlled machine tool 100 comprises a machine control (e.g. PLC and / or CNC control devices) for controlling the linear axes (and possibly rotary axes) of the machine tool 100 (see e.g. control device 200 in Fig. 3).

[0041] To carry out the method according to the invention according to a preferred embodiment of the invention, the tool spindle bearing of the spindle carrier 114 of the tool spindle 102 has a temperature sensor 116. For example, the temperature sensor 116 is configured to determine at least one temperature value (or multiple temperature values).

[0042] For example, the temperature sensor 116 is arranged adjacent to the tool spindle bearing and can preferably be integrated into it. Contaminants, such as chips or coolant residues, which arise particularly during the machining of workpieces, can thus advantageously no longer settle on the temperature sensor and impair its function. This makes it possible to avoid the disadvantages of external temperature sensors.

[0043] Furthermore, it is possible that several temperature sensors can be arranged on or in the spindle structure, e.g. on / in the spindle bearings, on / in a spindle shaft and / or on a spindle housing.

[0044] Fig. 2 shows an example of a comparison between a tool clamped in a tool spindle of a machine tool, which has experienced a temperature-related change in length, and a newly inserted, cold, identical sister tool.

[0045] In the upper image of the Fig. 2 shows a tool holder 118 carrying a schematically indicated drilling or milling tool 104, which is attached in a manner not shown in detail to a holding shaft portion of the tool holder 118. Tool holder 118 and drilling or milling tool 104 form, for example, a tool unit that can be clamped to the spindle.

[0046] A gripper groove 120 is provided on the tool holder 118, for example. At this gripper groove 120, the tool holder 118 is gripped by a gripper of a tool changer and transferred between a magazine position and a position on the machine tool.

[0047] Adjoining the tool holder 118 to the right, for example, is a hollow shank taper known per se (as merely an exemplary embodiment of a tool interface, e.g., hollow shank taper, steep taper, Morse taper, etc.), into whose opening a draw taper of a clamping system engages in order to draw the tool holder 118 with its hollow shank taper into a tool holder of a schematically illustrated spindle 102 and clamp it there. Of course, the present invention is not limited to hollow shank taper holders, so that other tool holders are conceivable.

[0048] Furthermore, a tool spindle bearing 122 is shown, the bearing concept of which will not be explained in detail below. A temperature sensor 116 is integrated into the tool spindle bearing 122. The temperature sensor 116 can be integrated into the tool spindle bearing 122, but is not limited to this. It is also conceivable, for example, that the temperature sensor 116 can be arranged adjacent to the tool spindle bearing 122.

[0049] Such sensors are particularly susceptible to contamination, which can reduce signal quality or function. Furthermore, in extreme cases, contamination (e.g., flying chips or coolant) can even lead to the destruction of the sensor or parts of it. To protect the temperature sensor 116 and to ensure its functionality, the applicants deliberately integrated the temperature sensor into the tool spindle bearing or arranged it adjacent to the tool spindle bearing.

[0050] Temperature sensor 116 is configured to repeatedly measure the current temperature of the clamped drilling or milling tool during machining. The temperature values ​​measured in this way serve as input variables for the temperature compensation calculation model, which will be explained in more detail later in the description.

[0051] The lower image of the Fig. Figure 2 essentially shows the same thing as the upper image. However, in the lower image, a sister tool of the same type as the previously used drilling or milling tool was inserted during machining. The sister tool of the same type was inserted directly from the tool magazine.

[0052] In comparison to the tool that is clamped in the upper image, and which has experienced a temperature-related change in length as a result of friction during workpiece machining, it can be seen that the replaced, cold, identically type sister tool, which is clamped in the lower image, has not yet experienced a temperature-related change in length.

[0053] Fig. 3 shows, by way of example, a schematic representation of a control device 200 for determining at least one compensation value on the machine tool 100 according to an exemplary embodiment of the invention. The control device 200 can be embodied as an external control device that is connected to the machine tool 100. Furthermore, the control device 200 can be integrated into the internal machine control of the machine tool 100 or form the machine control of the machine tool 100.

[0054] The control device 200 for use on a numerically controlled machine tool 100 comprises a tool change control means 202 for controlling a picking up of the drilling or milling tool 104 on the tool spindle 102 of the machine tool 100 and for controlling a changing of a new drilling or milling tool 104 on the tool spindle 102.

[0055] The tool change control means 202 is also configured to insert a sister tool of the same type as the previously used drilling or milling tool. The control device 200 further comprises a measuring means 204 for determining target positions and / or target and actual positions of linear and / or rotary axes of the machine tool in the direction of the spindle axis.

[0056] The control device 200 further comprises a relative movement control means 206 for controlling a relative movement of the tool spindle relative to a workpiece clamped on the machine tool on the basis of target positions of linear and / or rotary axes of the machine tool 100.

[0057] Compensating for the temperature-related change in length also includes adjusting one of the target positions of the linear and / or rotary axes of the machine tool 100.

[0058] The relative movement control means 206 can further be configured to output respective control signals to drives of the linear and / or rotary axes of the machine tool for controlling a relative movement of the tool spindle relative to a workpiece clamped on the machine tool on the basis of desired and actual positions of linear and / or rotary axes of the machine tool 100, wherein the compensation of the temperature-induced change in length comprises the adjustment of one of the actual positions of the linear and / or rotary axes of the machine tool 100.

[0059] Finally, the control device 200 comprises a compensation means 208 for determining at least one compensation value as a function of the determined temperature value.

[0060] The tool change control means 202, the measuring means 204, the relative movement control means 206 and the compensation means 208 are connected to each other via a data connection 210.

[0061] In addition, the control device 200 is connected to the machine tool 100 via the data interface 212 (e.g. directly to actuators and drives of the machine tool 100 for controlling the actuators and drives or indirectly to the machine control of the machine tool 100).

[0062] Fig. 4 shows, by way of example, a flow diagram of a method for compensating a temperature-induced change in length of a drilling or milling tool according to an embodiment of the invention, wherein the method according to the invention is used on a machine tool having a linear axis.

[0063] At the beginning of the machining process, a temperature compensation calculation model stored in the control device 200 is loaded according to step S401, wherein the temperature compensation calculation model can be provided tool-specifically or tool-independently.

[0064] The steps S402 to S406 described below are performed repeatedly during the machining of a workpiece 106 on the machine tool 100, particularly preferably until the machining process is completed. As long as no tool change is performed, preferably no new temperature compensation calculation model is loaded.

[0065] With the start of the workpiece machining, a temperature value is continuously determined in a step S402 by means of a temperature sensor 116 arranged at a temperature measuring position of the tool spindle 102.

[0066] Next, step S403 is carried out, for example, whereby the determined temperature value(s) are converted into sensor data and transmitted to the numerical control device 200 of the machine tool 100.

[0067] The determined temperature value(s) are used to determine the compensation value. This is determined in step S404, for example, based on the temperature compensation calculation model loaded in step S401.

[0068] The temperature compensation calculation model is stored, for example, in the control device 200 and is loaded, for example, before the start of machining the workpiece 106. In the event of a tool change, the control device 200 detects, for example, the newly inserted drilling or milling tool (for example, based on the tool number or the position of the drilling or milling tool in the tool magazine) and preloads a corresponding temperature compensation calculation model simultaneously with the insertion of the drilling or milling tool 104. The exemplary sequence of the method in which a tool change is carried out is described in detail later in the description.

[0069] A tool-specific temperature compensation calculation model can, for example, be provided as a look-up table, whereby the look-up table can be created in advance through experiments.

[0070] The table can be used to pre-store the corresponding temperature-related length change and / or the corresponding compensation value for several specified temperature values. For temperature values ​​lying between specified temperature values, the corresponding temperature-related length changes and / or the corresponding compensation values ​​can be easily determined during processing using interpolation.

[0071] To compensate for the temperature-related length change in step S405, the determined temperature value can be compared with temperature values ​​in the look-up table. If there is a match, the respective compensation value is transferred to the control device 200 so that the temperature-related length change can be compensated. Otherwise (if there is no match), interpolation is performed as described above to determine the corresponding compensation value.

[0072] A tool-independent temperature compensation calculation model can be provided, for example, as a numerical calculation formula.

[0073] In this variant, a tool-specific temperature coefficient and / or a tool-specific reference length of the drilling or milling tool at a reference temperature is included in the temperature compensation calculation model.

[0074] The derivation of the numerical calculation formula will not be discussed in detail below. However, in its simplest form, it can be based on the following formulas. ΔT=ΔTx−ΔTy ΔL=α⋅I0⋅ΔT

[0075] In formula (1), the temperature with the index X always corresponds to the currently determined temperature, whereas the temperature with the index Y corresponds to a temperature that occurred before the temperature T x was determined, e.g. a reference temperature.

[0076] In formula (2), α corresponds to a tool-specific temperature coefficient, I0 to a tool-specific reference length of the clamped drilling or milling tool and ΔT to a temperature change of the clamped tool during machining between two temperature measuring positions.

[0077] The tool-specific reference lengths and the tool-specific temperature coefficients are known for each drilling or milling tool or for each tool unit provided in the tool magazine and can be preloaded by the control device 200, depending on which drilling or milling tool is clamped or being changed.

[0078] In order to compensate for the temperature-related change in length of the drilling or milling tool according to step S405 as a function of the determined temperature value, a compensation value is first determined on the basis of the tool-independent temperature compensation calculation model.

[0079] In both cases (tool-specific and tool-independent), the determined compensation value is converted into sensor data and sent to the relative movement control means 206 of the control device 200 in order to thereby perform a correction of the relative movement of the tool spindle 102 relative to a workpiece 106 clamped on the machine tool 100 on the basis of the target positions.

[0080] In this way, the relative movement control means 206 can compensate the target positions of the tool spindle 102 by adjusting at least one target position of the linear axis of the machine tool 100, e.g., by generating a movement command signal.

[0081] Fig. 5 shows, by way of example, a flow diagram of a method for compensating for a temperature-induced change in length, in the case that the method according to the invention is used on a machine tool which has several linear and / or rotary axes.

[0082] Analogous to the method according to the invention, which is carried out on a machine tool with a linear axis, in the method according to the invention on a machine tool with several linear and / or rotary axes, at the beginning of the machining process, a temperature compensation calculation model stored in the control device 200 is also loaded according to step S501, wherein this temperature compensation calculation model can also be provided in a tool-specific or tool-independent manner.

[0083] In principle, the steps described below can also be performed repeatedly during the machining of a workpiece 106 on the machine tool 100 until the machining process is completed. Steps S502 and S503 are performed, for example, analogously to the method according to the invention, which is used on a machine tool having a linear axis.

[0084] Due to the multiple linear and / or rotary axes, step S504 was provided to compensate for the temperature-related length change, after which a current angular orientation of the spindle axis of the tool spindle 102 in the coordinate system of the machine tool 100 is determined. This step is advantageous because the tool spindle 102 can be moved almost arbitrarily due to the multiple linear and / or rotary axes.

[0085] Subsequently, step S505 is performed, in which several compensation values, each assigned to a coordinate axis in the machine tool's coordinate system, are determined depending on the determined temperature values ​​and the determined current angular orientation of the spindle axis. The temperature compensation calculation model required for this step can be provided in a tool-specific or tool-independent manner, analogous to the embodiment described above.

[0086] Finally, the compensation value determined as a function of the temperature values ​​of the drilling or milling tool and the angular orientation of the spindle axis is also converted into sensor data and sent to the relative movement control means 206 of the control device 200 in order to thereby carry out a correction of the relative movement of the tool spindle 102 relative to a workpiece 106 clamped on the machine tool 100 on the basis of the actual and / or target positions.

[0087] Thus, in step S506, the relative movement control means 206 compensates for a temperature-induced change in length of a drilling or milling tool by adjusting at least one actual and / or target position of the linear and / or rotary axes of the machine tool 100 by generating a movement command signal.

[0088] With the help of the Fig.6, an exemplary method according to the invention of a further embodiment is to be described for the case when a tool change is carried out during the machining of the workpiece on a machine tool with a linear axis.

[0089] In principle, steps S601 to S606 can be carried out analogously to steps S401 to S406.

[0090] Compensation of the temperature-related change in length is carried out repeatedly until either the machining of the workpiece is completed or until a tool change occurs.

[0091] During a tool change in step S607, the control device 200 checks, for example, whether it is a sister tool of the same type or not. If the newly inserted drilling or milling tool is a sister tool of the same type, the exemplary method according to steps S602 to S605 is repeatedly performed until the machining of the workpiece is completed or until another tool change occurs.

[0092] However, if the tool change involves a completely different drilling or milling tool and not a sister tool of the same type, the control system detects this condition. In this case, a new temperature compensation calculation model for the new drilling or milling tool is loaded as an example before determining the temperature value.

[0093] This also allows temperature-related temperature changes to be compensated for when a tool is changed during machining of the workpiece. This is especially true if the newly inserted drilling or milling tool is a different type of sister tool.

[0094] In summary, the present invention makes it possible to provide a method for compensating for a temperature-induced change in length in which simpler, cost-saving means can be used compared to the methods known in the prior art.

[0095] Furthermore, the present invention makes it possible for the method to be more easily integrated into the machine control system of the machine tool and to be controlled fully automatically by the machine control system without the additional use of a connected evaluation computer.

[0096] Finally, the present invention enables the method to be applied efficiently in series production and also to be carried out directly at the machine tool owner's site without the need for the costly travel of specialist personnel from the machine manufacturer.

Claims

[1] Method for compensating a temperature-induced change in length of a drilling or milling tool (104) or a tool unit comprising the drilling or milling tool, which is interchangeably clamped on a tool spindle (102) of a machine tool (100), comprising: - determining a temperature value by means of a temperature sensor (116) arranged at a temperature measuring position of the tool spindle (102); - determining at least one compensation value depending on the determined temperature value; and - Compensating for the temperature-related change in length of the drilling or milling tool (104) or the tool unit on the basis of the at least one specific compensation value. [2] Method according to claim 1, characterized by : - Transmitting sensor data indicating the determined temperature value from the temperature sensor (116) arranged at the temperature measuring position of the tool spindle (102) to a numerical control of the machine tool (100), wherein the determination of the compensation value and / or the compensation of the temperature-related change in length of the drilling or milling tool (104) or of the tool unit is carried out in the numerical control of the machine tool (100). [3] Method according to claim 1 or 2, characterized by , that the numerical control is configured to output respective control signals to drives of the linear and / or rotary axes of the machine tool (100) for controlling a relative movement of the tool spindle (102) relative to a workpiece (106) clamped on the machine tool (100) on the basis of target positions of linear and / or rotary axes of the machine tool (100), wherein the compensation of the temperature-induced change in length comprises the adjustment of at least one of the target positions of the linear and / or rotary axes of the machine tool (100). [4] Method according to claim 1 or 2, characterized by , that the numerical control is configured to output respective control signals to drives of the linear and / or rotary axes of the machine tool (100) for controlling a relative movement of the tool spindle (102) relative to a workpiece (106) clamped on the machine tool (100) on the basis of target and actual positions of linear and / or rotary axes of the machine tool (100), wherein the compensation of the temperature-induced change in length comprises the adjustment of at least one of the actual positions of the linear and / or rotary axes of the machine tool (100). [5] Method according to one of the preceding claims, characterized bythat the compensation of the temperature-related change in length of the drilling or milling tool (104) or of the tool unit is carried out in the numerical control of the machine tool (100) in the direction of the spindle axis of the tool spindle (102) of the machine tool (100). [6] Method according to claim 5, characterized by that the compensation of the temperature-related change in length comprises the adjustment of at least one actual and / or target position of one or more linear and / or rotary axes of the machine tool (100) in the direction of the spindle axis of the tool spindle (102) of the machine tool (100). [7] Method according to claim 5 or 6, characterized by : - determining a current angular orientation of the spindle axis of the tool spindle (102) in the coordinate system of the machine tool (100), and - Determining a plurality of compensation values, each assigned to a coordinate axis in the coordinate system of the machine tool (100), as a function of the determined temperature value and the determined instantaneous angular orientation of the spindle axis, wherein the compensation of the temperature-related change in length of the drilling or milling tool (104) for the respective coordinate axes in the coordinate system of the machine tool (100) is carried out in each case as a function of the compensation value assigned to the respective coordinate axis. [8] Method according to one of the preceding claims, characterized by that the determination of the temperature value, the determination of the at least one compensation value, and the compensation of the temperature-related change in length of the drilling or milling tool (104) are carried out repeatedly during the machining of a workpiece (106) on the machine tool (100). [9] Method according to one of the preceding claims, characterized by that the determination of the at least one compensation value is carried out on the basis of a temperature compensation calculation model for calculating the temperature-related change in length of the drilling or milling tool as a function of the determined temperature value. [10] Method according to claim 9, characterized by , that the temperature compensation calculation model is provided tool-specifically; or the temperature compensation calculation model is provided in a tool-independent manner, wherein a tool-specific temperature coefficient and / or a tool-specific reference length of the drilling or milling tool (104) at a reference temperature is included in the temperature compensation calculation model. [11] Method according to claim 10, characterized bythat when a tool is changed on the machine tool (100), the tool-specific temperature compensation calculation model used to determine the at least one compensation value is changed on the numerical control of the machine tool (100) in accordance with the replaced tool (104), or the tool-specific temperature coefficient used in the tool-independent temperature compensation calculation model and / or the tool-specific reference length of the tool (104) used in the tool-independent temperature compensation calculation model is / are changed if the replaced tool (104) is a tool (104) different from the drilling or milling tool (104) previously used. [12] Method according to claim 10 or 11, characterized bythat when a tool is changed on the machine tool (100), the tool-specific temperature compensation calculation model used to determine the at least one compensation value continues to be used on the numerical control of the machine tool (100), or the tool-specific temperature coefficient used in the tool-independent temperature compensation calculation model and / or the tool-specific reference length of the tool (104) used in the tool-independent temperature compensation calculation model continues to be used if the replaced tool (104) is a sister tool of the same type as the previously used drilling or milling tool (104). [13] Method according to one of claims 9 to 12, characterized by , that one or more tool-specific temperature compensation calculation models are pre-stored on the numerical control of the machine tool (100), and / or a tool-independent temperature compensation calculation model and one or more tool-specific parameter sets, each comprising the tool-specific temperature coefficient and / or the tool-specific reference length of the drilling or milling tool (104) or the tool unit, are pre-stored. [14] Method according to one of claims 1 to 8, characterized by , that one or more tool-specific compensation data sets are pre-stored on the control of the machine tool (100), wherein each tool-specific compensation data set for a corresponding drilling or milling tool (104) specifies respective associated compensation values ​​for a plurality of temperature values, wherein the determination of the at least one compensation value is carried out on the basis of one of the pre-stored compensation data sets. [15] Method according to one of the preceding claims, characterized bythat the temperature sensor (116) for determining the temperature value is integrated in a tool spindle bearing (122) of the tool spindle (102) or is arranged adjacent to the tool spindle bearing (122) of the tool spindle (102). [16] Method according to one of the preceding claims, characterized by that a plurality of temperature sensors (116) are arranged on the tool spindle (102) and the at least one compensation value is determined as a function of the plurality of determined temperature values. [17] Control device (200) for use on a machine tool (100) having a tool spindle (102) with a temperature sensor (116) arranged at a temperature measuring position of the tool spindle (102), wherein the control device (200) has a numerical control which is designed to carry out, as a function of a temperature value determined by means of the temperature sensor (116), a method for compensating for a temperature-induced change in length of a drilling or milling tool (104) or a tool unit which is or is interchangeably clamped in the tool spindle (102) of the machine tool (100), according to one of the preceding claims. [18] A machine tool (100) comprising a spindle device comprising a tool spindle (102) with a temperature sensor (116) arranged at a temperature measuring position of the tool spindle (102), and a transmission device for transmitting sensor data indicating the determined temperature value from the temperature sensor (116) arranged at the temperature measuring position of the tool spindle (102) to a numerical control of the machine tool (100); and a control device (200) according to claim 17. [19] Computer program product with program means which are stored on a data carrier and which are designed to be executed on a control device (200) of a numerically controlled machine tool (100) comprising a tool spindle (102) for interchangeably receiving a drilling or milling tool (104) or a tool unit, such that a method according to one of claims 1 to 16 is carried out on the machine tool (100).

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