WO2009037165A1 - Method for determining a thermally induced change in position of a machine tool section of a machine tool - Google Patents

Method for determining a thermally induced change in position of a machine tool section of a machine tool

Info

Publication number
WO2009037165A1
WO2009037165A1 PCT/EP2008/062006 EP2008062006W WO2009037165A1 WO 2009037165 A1 WO2009037165 A1 WO 2009037165A1 EP 2008062006 W EP2008062006 W EP 2008062006W WO 2009037165 A1 WO2009037165 A1 WO 2009037165A1
Authority
WO
Grant status
Application
Patent type
Prior art keywords
machine
tool
position
section
model
Prior art date
Application number
PCT/EP2008/062006
Other languages
German (de)
French (fr)
Inventor
Moshe Israel Meidar
Wolfgang Horn
Thomas Bayha
Ralph Davis
Karl-Heinz Scharschmidt
Original Assignee
Ex-Cell-O Gmbh
Gottfried Wilhelm Leibniz Universität Hannover
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date

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Classifications

    • GPHYSICS
    • G05CONTROLLING; REGULATING
    • G05BCONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B19/00Programme-control systems
    • G05B19/02Programme-control systems electric
    • G05B19/18Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form
    • G05B19/404Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of programme data in numerical form characterised by control arrangements for compensation, e.g. for backlash, overshoot, tool offset, tool wear, temperature, machine construction errors, load, inertia
    • GPHYSICS
    • G05CONTROLLING; REGULATING
    • G05BCONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B2219/00Program-control systems
    • G05B2219/30Nc systems
    • G05B2219/49Nc machine tool, till multiple
    • G05B2219/49206Compensation temperature, thermal displacement, use measured temperature
    • GPHYSICS
    • G05CONTROLLING; REGULATING
    • G05BCONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B2219/00Program-control systems
    • G05B2219/30Nc systems
    • G05B2219/49Nc machine tool, till multiple
    • G05B2219/49207Compensate thermal displacement using measured distance
    • GPHYSICS
    • G05CONTROLLING; REGULATING
    • G05BCONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B2219/00Program-control systems
    • G05B2219/30Nc systems
    • G05B2219/49Nc machine tool, till multiple
    • G05B2219/49219Compensation temperature, thermal displacement

Abstract

In order improve methods for determining a thermally induced change in position of a machine tool section of a machine tool, wherein the machine tool section can be moved along a machine tool axis, such that the change in position of the machine tool section can be determined in a manner that is as easy as possible, the invention provides that a deformation model of the machine tool is created, which indicates a relationship between the change in position to be determined and at least one input variable, relative to the machine tool axis, wherein the at least one input variable has at least one temperature value, and the at least one input variable is detected for determining the thermally induced change in position and is input into the deformation model.

Description

Method for determining a thermally induced

Change in position of a machine tool portion of a machine tool

The invention relates to a method for determining a thermally induced change in position of a machine tool portion of a machine tool, the machine tool section along a tool machine axis is movable.

From DE 103 12 025 Al a method for compensation of errors of a position control of a reference point of a controllable in at least one axis machine is known, wherein the position control comprises a path control, a device for position detection and control means. the following method steps are provided: detecting the current position of all the axes, calculating the current position of the reference point from the current positions of the axes involved in the path control, calculating the deformation of the engine in response to sizes of a deformation of the machine involved in the path control may result, and sen the current positions of Ach involved in the path control, and correcting the calculated current position of the reference point as a function of the current distortion of the machine.

From DE 198 48 642 Al discloses a process for compensating for temperature-conditioned dimensional deviations in machine geometry, in particular a machine tool or a robot, are performed at the user input in a first coordinate system and is carried out, a conversion into a second coordinate system to control signals for the to determine final drives are known. The compensation of temperature-conditioned dimensional deviations is effected before the conversion of the coordinates from the first to the second coordinate system. From US 6,167,634 Bl, a measuring system and communication system for thermal errors in a machine tool is known. It is a module is provided which serves to compensate for thermal errors of the machine tool. The module comprises an operating part, a database, an analog-to-digital converter, a counter and a digital input / output. The operational part determines all the coefficients of a model equation for the thermal error, which specifies the relationship between temperature and thermal errors in different operating conditions.

From US 6,269,284 Bl a machine tool is known which is controlled by a process which comprises the steps of measuring geometric and thermal faults, creating a global differentiated essential tool machine position model and use of this model to control the real-time compensation of the machine tool operation. A controller modifies the position feedback signals which are used by the machine to compensate for geometrical and thermal error given by the model.

From EP 1300738 A2 an offset apparatus for an NC machine tool is known.

The thermally induced changes in position of a machine tool portion of a machine tool have a significant impact on the machining accuracy that can be achieved with the help of the machine tool.

To achieve a high machining accuracy, it is possible to minimize thermally induced change in position of the machine tool section. For example, the tool can be operated under constant ambient conditions. However, this requires a complicated air-conditioning an environment of the machine tool. To improve the machining accuracy, the machine tool can also be operated exclusively in a warmed-up state. During such a warm-up phase, however, the machine tool can not be used productively.

However, there is also the possibility of a control-side compensating a thermally induced change in position of the machine tool portion. If the amount and direction of a thermally induced change in position of a machine tool section are known, the position change can be taken into account in the control of movement of the machine tool section, to compensate for the change in position.

On this basis, the present invention has for its object to provide a method of the type mentioned at the outset, with which the change in position of the machine tool section can be as simple as possible determined.

This object is achieved in a method of the type mentioned in that a deformation model of the machine tool is created which on the machine tool axis indicates relative a relationship between the position to be determined change and at least one input variable, wherein the at least one input variable comprises at least one temperature value, and the determining the thermally induced change in position of the at least detects an input variable and entered into the deformation model.

With the inventive method particularly simple comparison can be specified deformation model. This refers to a machine tool axis along which the machine tool section is movable. This enables the provision of a relatively simple deformation model. The deformation model is only created once and allows a function of a varying input variable determining a thermally induced change in position of Werkzeugmaschinenab- section. The input includes at least one temperature value, as it has on the thermally induced change in position of the machine tool section a significant influence.

Preferably, the relationship between the change tion to be determined and positioning at least one input variable of the distortion model is recognized linear. This allows the specification of a proportional allocation rule between a variable input and a to be determined on the basis of a detected input position change of the machine tool section.

Preferably, the deformation model is created independently of an operating state of the machine tool. This can provided a particularly simple deformation model, which has for all operating states of the machine tool, in particular for different temperature conditions of the machine tool, validity.

Specifically, an input is detected at least during operation of the machine tool and entered into the deformation model. This allows for timely and easy determination of a thermally induced change in position of the machine tool section.

An advantageous embodiment of the invention provides that the machine tool section comprises at least one workpiece carrier or is formed by a workpiece carrier. By detecting a thermally induced change in position of the workpiece carrier, it is possible so to drive the workpiece carrier and / or a tool carrier of the machine tool, that the thermally induced change in position can be compensated.

According to a further advantageous embodiment of the invention it is provided that the machine tool section is a tool carrier detected or by a tool carrier. By determining a thermally induced deviation of such a tool carrier this can be compensated, for example by an appropriate control of the tool carrier, but also by a corresponding control of a workpiece support of the machine tool.

A further embodiment of the invention provides that the machine tool section comprises at least one carriage or is formed by such a carriage. Such a carriage can be used for example for the arrangement of a displaceably mounted on the slide tool carrier and / or the workpiece carrier.

Preferably, the at least one input variable of the distortion model comprises an ambient temperature of the machine tool. The ambient temperature of the machine tool has a particularly large impact on changes in position of the machine tool section. This is because the ambient temperature of the entire machine tool moves up shapes.

Further, it is advantageous if the at least one input variable of the distortion model comprises a sensed on the machine tool reference temperature. In a thermally steady state, this reference corresponds to the temperature of the ambient temperature. In a transient state of the machine tool, the reference temperature of the ambient temperature differs, so that a more accurate determination of a positional change of the machine tool section is possible on the basis of the reference temperature.

Preferably, the reference temperature is detected on or in a field of machine tools, which is unaffected by heat sources of machine tool, at least substantially. In this way, the entire machine tool can be detected in an unbiased of machine-internal heat source heating or cooling. This heating or cooling causes corresponding changes in length of all parts of the machine tool.

Preferably, the machine tool comprises the machine part at least one tool, which is kinematically coupled directly or indirectly to the machine tool section. This allows the determination of a change in length of a tool machine part. This change in length influenced at least in part the change in position of the machine tool section.

It is advantageous if the at least one machine tool part is fixed is. This allows the determination of a change in length, which is independent of other machine tool parts.

Advantageously, this is a least one machine tool section

Machine bed and / or a machine frame or formed by a machine bed and / or a machine frame. These machine tools parts experienced a particularly large length change with a change in ambient temperature and / or the reference temperature of the machine tool. They therefore have a major impact on the change in position of the machine tool section. It is further preferred if the at least one machine tool section summarizes a position measuring device for detecting the relative position of the machine tool section and a stationary machine tool section around or is formed by such a position measuring device. A ER- summed relative position can for example be used as a control variable for controlling a drive means for driving the machine tool section.

It is particularly advantageous if the at least one Eingansgröße the deformation model comprises the relative position of the machine tool section and a stationary machine tool part. This allows the determination of a change in position of the machine tool section is not only a function of a temperature value, but also a function of the relative position of the machine tool portion and the stationary tool machine part.

Preferably, the deformation model includes a tool machine section associated with model element. With the aid of such a model element a change in length of the machine tool portion can be determined in particular.

Advantageously, the model element indicates a relationship between an ambient temperature of the machine tool and / or a detected on the machine tool reference temperature on the one hand and one related to the machine tool axis length change of the machine tool portion on the other. Using such a model member thermally induced reductions or extensions of the machine tool section can be determined. Preferably, the above-mentioned connection is recognized linear. A linear relationship is determined for example by a coefficient of expansion of the material of the machine tool section and by the length of the machine tool portion in a tool machine axis to the parallel direction and at a reference temperature.

In a corresponding manner, it is advantageous if the deformation model includes a model element is associated with a machine tool part which is kinematically coupled directly or indirectly to the machine tool section. This allows a separate determination of a change in length of the tool machine part.

It is preferred if the assigned to the machine tool section model element indicating a relationship between an ambient temperature of the machine tool and / or a detected on the machine tool reference temperature on the one hand and one related to the machine tool axis change in length of the tool machine part on the other hand.

Here, too, it is preferable to find a linear input to the next inlet connexion, in particular a coefficient of expansion of the machine tool part and the length of the tool machine part at a reference temperature, for example at 20 0 C.

It is particularly preferred if changes in length determined with the aid of different model elements are superimposed on one another is. This allows a particularly accurate determination of the position change of the machine tools segment.

Further, it is preferable that the machine tool comprises a work space and if the at least one input variable of the deformation model includes a working position in space of the machine tool section. This enables a particularly simple spatial assignment of different length changes of the machine tool portion and at least one machine tool part.

Preferably, the at least one input variable of the distortion model comprises a temperature value which is detected at least one heat source of the machine tool. In this way not only global heat influences that are imposed by the ambient temperature of the machine tool, are recorded, but also by machine-internal

Heat sources related local temperature effects are taken into account. A local effect of temperature can cause deformation of the machine tool, which causes a displacement of the machine tool section. Such a shift has at least partially influence the to be determined end position change of the machine tools segment.

According to one embodiment of the invention the at least one heat source acts directly on the machine tool section. In such a heat source may, for example, be a coupling device by means of which the machine tool section is coupled to a drive means for driving the machine tool section. This may for example be the rotor of a linear drive or the spindle nut of a ball screw drive. From the perspective of Machine Tools section provides such a coupling device, a heat source of which at least deforms the Machine Tools section and thus contributes to a change in position of this machine tool section.

According to a further embodiment of the invention the at least one heat source acts directly on a machine tool part which is kinematically coupled directly or indirectly to the machine tool section. With such a heat source is in particular about a drive means for driving the machine tool section. A consideration of such a heat source is particularly advantageous in driving devices which are highly efficient and therefore can become hot during operation of the machine tool.

In a corresponding manner, it is advantageous if the deformation model contains at least one model element, which indicates a relationship between a temperature difference and a to the tool machine axis loading early displacement of the machine tool section, whereby the temperature difference is determined by the difference of a detected at the at least one heat source temperature value to an ambient temperature of the machine tool and / or a detected on the machine tool reference temperature. Using such a model element, it is possible to determine the influence of the machine-internal heat sources to a strain isolated from the influence of the ambient temperature or the Referentemperatur on changes in length of the entire machine tool.

Preferably raturdifferenz and related to the machine tool axis displacement of the machine tool section by a linearly for the next connection in the connection between the temperature range. This allows particularly easy determination of a displacement of the machine tool section, which at least in part, the position change of the machine tool portion having determined.

To determine a coefficient characterizing the linear relationship, it is advantageous to perform a finite element simulation. In this simulation, is first based on a predetermined characteristic of a heat source a voltage applied to the machine tool temperature distribution and a displacement of the machine tool section is calculated on the basis of this temperature distribution. The coefficient may then be determined by the calculated displacement by the predetermined temperature difference is divided. The characteristic size of the heat source can be specified as a particular heat output, heat flow and / or temperature difference.

Preferably, the temperature distribution is stationary. This allows the neglect of dynamic temperature influences, thus simplifying the deformation model.

It is preferable if the deformation model various heat sources of machine tool includes separately associated model elements. This enables the provision of a deformation model with which even at different temperatures of different heat sources, a position change of the machine tool section can be determined accurately.

Preferably determined using various model elements of the deformation model displacements of the machine tool section are superposed on each other in order to further increase the accuracy of determining the position change of the machine tool section.

Furthermore, it is preferable that the deformation model, a contains the machine tool portion associated with model element and / or a model element is associated with a machine tool part which is kinematically coupled directly or indirectly to the machine tool section, and / or a model element of a heat source of the machine tool is assigned to that the deformation model contains at least two different model elements and that certain changes in length and / or displacements of the machine tool section and / or the machine tool portion are superposed on each other by means of these different model elements. This allows a particularly accurate and comprehensive provision which composing of individual length changes and / or shifts position change of the machine tools segment.

The invention further relates to a method for compensating a thermally induced change in position of a machine tool portion of a machine tool.

The invention has the further object of the invention to provide a method which enables easy and accurate compensation of a thermally induced change in position of a machine tool portion of a machine tool.

This object is achieved in that a thermally induced change in position of a machine tool portion of a machine tool is determined with a method described above and that the thermally induced change of position determined in this way is used as control variable for the control of a position changing means of the machine tool section. The position changing means is formed for example by a drive device or an adjusting device.

A particularly simple compensation is obtained when a direction opposite to the specific thermally induced change in position of the target position change is superimposed for driving a desired position of the machine tool section of the target position. In this way, a particularly good match between the target position and an actual position of the machine tool section can be ensured. Other features and advantages of the invention are subject of the following description and the drawings illustrating one preferred embodiment.

In the drawings:

1 shows a perspective view of an embodiment of a machine tool;

Figure 2 is a side view of the machine tool of Figure 1;

Figure 3 is a symbolic representation of a deformation model for use in the machine tool of Figure 1;

Figure 4 is a schematic side view of the machine tool

Figure 1 with a present across the machine tool temperature distribution;

Figure 5 is a schematic side view of the machine tool of Figure 1 in a result of the temperature distribution as shown in FIG

4 deformed state;

Figure 6 is a representation of the detected during operation of the machine tool of Figure 1 temperature values;

Figure 7 is a representation of a time course of a change in position of a machine tool section of the machine tool of Figure 1 using the temperature values ​​shown in Figure 6 and by using the deformation model of Figure 3; 8 shows a diagram in which with the aid of the deformation model from

3 shows certain changes in position real position changes are compared.

1 shows an embodiment of a machine tool 10 is shown in perspective.

The machine tool 10 comprises a machine bed 12, with which the machine tool can be placed on a backing 10th Further, the machine tool 10 comprises a substantially perpendicularly to the machine bed extending machine frame 14, which is fixedly connected to the machine bed 12th

The machine tool 10 comprises a workpiece holder 16 which is movable relative to the machine bed 12th

The machine tool 10 also has a tool carrier 18 in the form of a spindle. Alternatively, the tool carrier 18 may be formed by a quill.

The tool carrier 18 is arranged on a first carriage 20th The first carriage 20 in turn is mounted on a second carriage 22nd The second carriage 22 is movably mounted on the machine frame fourteenth The carriages 20 and 22 form a cross-slide unit.

The workpiece carrier 16 is movable along a tool machine axis 24th This machine tool axis is in the illustrated embodiment in the drawing, the z-axis of the machine tool 10. The second carriage 22 is movable relative to the machine frame 14 along an x-axis of the machine tool 10th For this purpose the carriage 20 perpendicular to the tool carrier 18 along a y-axis can be moved relative to the second carriage 22nd

The machine tool 10 comprises a drive device 26 for driving the workpiece support 16 along the tool machine axis 24th The drive means 26 includes a fixed to the machine bed 12 drive motor 28th

The drive motor 28 acts via a, not shown in Figure 1 for reasons of clarity spindle to a coupling device 30 of the workpiece carrier 16. The coupling device 30 is formed in the form of a spindle nut 32nd

The machine tool 10 further comprises a position measuring device 34 in the form of a linear scale 36. The linear scale 36 is fixedly connected at the level of a relatively central to the extension of the linear scale 36 position at a coupling point 38 to the machine bed 12th Starting from the coupling point 38, a front portion 40 of the linear scale 36 in a positive (z-) direction along the axis machine tool 24 to expand. A rear portion 42 of the linear scale 36 may extend from the coupling point 38 along the axis machine tool 24 in the negative (z) direction.

The workpiece support 16 and the tool holder 18 are movable within a working space 44th In order to process an attachable on the workpiece carrier the workpiece 16 with high precision, both the working area positions of the workpiece carrier 16 and the work space position of the tool carrier 18 must be coordinated. The working space position of the workpiece carrier 16 may be changed by a corresponding control of the driving means 26th Since the machine tool is, however, subjected to 10 thermal influences, for example, an increase in the ambient temperature, the machine tool is subject to thermally induced changes in length 10 and relocations.

For the following description it is assumed that the workpiece carrier 16 has a machine tool section 48 forms, the thermally induced change of position is to be determined relative to the machine tool axis 24 (z-axis).

The position measuring device 34 forms a directly kinematically coupled with the machine tool section 48 machine part 50th

The machine bed 12 forms an indirect (with the interposition of the position measuring device 34) kinematically connected to the machine tool section 48 coupled machine tool part 52. The machine tool section 52 may alternatively comprise the machine bed 12 in combination with the machine frame fourteenth

During operation of the machine tool 10, that is, during the movement of the machine tool section 48 along axis 24 of the machine tool, the drive motor 28, which forms a heat source 54 heats. The heat source 54 acts directly on the machine tool section 52 in the form of the machine bed 12th

The coupling device 30 of the machine tool section 48 in the form of the workpiece holder 16 also heats up and is considered for the following considerations as the heat source 56th The heat source 56 acts un- indirectly on the machine tool portion 48. The tool 10 is equipped with a plurality of temperature sensors. A first temperature sensor 58 is disposed at the level of the coupling point 38 at the position measuring device 34th With the aid of the temperature sensor 58 is a reference temperature of the machine tool can be determined 10th

Further, the machine tool 10 includes a temperature sensor 60. This is arranged on the heat source 54 in the form of the drive motor 28th Another temperature sensor 62 is means to the heat source 56 in the form of the coupling 30.

For determining a thermally induced change in position of the machine tool section 48 is a symbolically illustrated in Figure 3 deformation model 64 is used. With the aid of the deformation model 64 is a thermally induced change in position 68 of the machine tool portion 48 can be determined based on the detected during operation of the machine tool 10 input variables 66th

The deformation model 64 includes a plurality of model elements. Here- in a model element 70 is assigned to the machine tool section 48th Another model element 72 is assigned to the machine tool section 50th Another model element 74 is assigned to the machine tool section 52nd Another model element 76 of the heat source 54 is assigned. Another model element 78 of the heat source 56 is assigned.

The model element 70 includes an equation of the form:

Elongation = alpha * * reference length (T fe r Re enz - T Be train) -

The alpha factor is determined by the material from which the machine tool portion is made 48th The reference length is the initial length of the machine tool section 48 in train to the machine tool axis 24 parallel direction at a reference temperature T Be, for example at 20 0 C. The reference temperature T Re fe r enz (reference numeral 80, Figure 3) is detected by the temperature sensor 58th In this way, a change in length can be determined 82 by means of the model element 70th

The model element 72 includes an equation of the form:

Elongation = alpha * * reference length (T fe r Re enz - T Be train) -

The coefficient of the model element 72 is determined by the product of "alpha" and a reference length. The alpha factor is determined by the material of the tool machine part 50th

From Figure 2 it is clear that the particular with the aid of the model element 72 change in length 84 of the tool machine part in dependence of the position of the machine tool section 48 can lead 18 to an increase or a decrease of a distance 93 between the workpiece support 16 and the tool carrier 50th the workpiece carrier 16 is in the position shown in Figure 2 position, ie, starting from the coupling point 38 in the region of the front portion 40 of the machine tool part 50, causing the change in length 84 of the machine tool part 50 increasing the distance 93, the workpiece carrier 16 is, however, in the range of the rear portion 42 of the machine tool part 50, performs a

Change in length 84 of the machine tool part 50 starting to a shortening of the distance 93. Of this is supplied to the model element 72 of the shaping model 64, a further input variable 66 in the form of a relative position of the 100th The relative position 100 indicates the position of the machine tool nenabschnitts 48 relative to the stationary machine tool section 52nd Alternatively or additionally, the work space position of the machine tool section 48 could be used as further input variable 66th

The reference length may thus by difference from the relative position 100 and half the length of the tool machine part 50 in parallel to the machine tool axis 24 direction at a reference temperature T Be train (for example, at 20 0 C) are determined. In this manner, with the aid of the model element 72 is a linear relationship between the reference temperature 80 (T fe r Re enz) can be specified and a thermally induced change in length 84 of the tool machine part 50th

In the model element 74 of the coefficient of a linear relationship between a change in length of the machine tool part 52 and the reference temperature 80 through the material of the machine bed 12 and by a reference length of the machine bed is determined at a reference temperature. In this way, a thermally induced change in length of the tool 86 the machine part 52 can be determined.

With the aid of the temperature sensor 60, a temperature value can be detected in 88 of the heat source 54th With the aid of the temperature sensor 62, a temperature value 90, the heat source 56 can be detected.

The model element 76 includes an equation of the form:

Shift = C * (Twarmequelle - T Re fe r enz) -

This means that for determining a displacement 92 of the machine tool section 48 both of the reference temperature 80 and the temperature value 88 of the heat source is taken into account 54th To determine the constant "c" of the model element 76 is carried out as follows: On the basis of a finite element simulation of a temperature distribution symbolically illustrated in Figure 4 is calculated, which results distributed over the machine tool 10 when a machine's internal heat source, for example the heat source 54, the machine tool 10 is heated locally.

On the basis of a calculated temperature distribution resulting deformation of the machine tool can be calculated therefrom 10 (see Figure 5). The machine bed 12 flexes or bends due to the influence of the heat source 54, so that the machine frame 14 and thus the tool holder 18 relative to the machine tool axis 24 (z-axis) in the negative direction shift. This leads to an increase in the distance 93 shown in Figure 2 between the tool carrier 18 and the workpiece carrier sixteenth

A determined in this way increasing the distance 93 is equal to the above-mentioned coefficient "c" is multiplied with a temperature difference that can be assumed for the calculation of the temperature distribution shown in Figure 4 or at a heat output or a default

Heat flow results. The temperature difference is determined, for example, by the difference between an assumed for the heat source 54 temperature and a reference temperature, for example 20 0 C. The above coefficient "c" is now as simple division of the calculated using the finite element simulation enlargement of the distance 93 and said temperature difference.

During operation of the machine tool 10, a shift can then having regard to the coefficients "c" are calculated 92, on basis of the detected during operation of the machine tool temperature values ​​80 (reference temperature) and 88 (temperature of the heat source 54). The model element 78, which is associated with the heat source 76 corresponds in its construction to the model element 76. In order to determine a coefficient of the model element 78 may advertising performed as described above, the wherein not here an introduction of heat by the heat source 54, but by a heat introduction is understood by the heat source 56th During operation of the machine tool 10, a shift 94 on the basis of temperature values ​​80 (reference temperature) and 90 (temperature of the heat source 56) can then be determined with the aid of the model element 78th

To further improve the accuracy of the model elements 76 and 78 can be determined and stored in the model elements also each have a plurality of different coefficients "c". the carriage 20 and / or 22 can be determined in the x-direction and / or y-direction, these different coefficients coeffi- particular on the basis of different positions. In the use of the model elements 76 and 78 for detecting a displacement of the carriage 92 or 94 can then be grasped back to a corresponding coefficient 20 and / or 22 depending on the current position.

The above certain length changes 82, 84, 86 as well as the displacements 92 and 94 are superposed by means of a linking unit 98 to each other. Here, the kinematic structure of the machine tool 10 is taken into account, so that the said length changes and shifts can be correctly signed added.

In Figure 6 are exemplary time profiles of the temperature values ​​80, illustrated 88, 90, which have been acquired in each case with the aid of the temperature sensors 58, 60 and 62 during operation of the machine tool 10th On the basis of these temperature gradients, and by using the deformation models 64 changes in the length 82 shown in Figure 7 in its course over time 84, 86 and deflection 92 may be determined 94, and are linked to a thermally induced change in position 68 of the machine tool section 48th

The displacement 82 due to the change in length of the machine tool section 48 is assumed in the negative z-direction since the coupling point with respect to the z-axis 30 in the positive z direction is arranged offset to the center of the machine tool section 48th Thereby causing longitudinal expansion of the machine tool section 48 is a shortening of the distance 93 between the workpiece support 16 and the tool carrier eighteenth

Also, the heat input by the heat source 56 related displacement 94 is assumed in the negative z-direction as the displacement 94 results in a shortening of the distance 93 between the workpiece support 16 and the tool carrier eighteenth

The change in length 84 of the machine tool part 50 in the form of the position measuring device 34 is assumed in the positive z direction. Also, the change in length 86 of the machine tool part 52 and the displacement 92 due to the heat source 54 are assumed in the positive direction.

From Figure 7 it can be seen that the changes in length of 82, 84 and 86, which are calculated in dependence of the reference temperature 80 have a dominant alternating influence and that the displacements 92 and 94 are relatively small due to the heat input by the heat sources 54 and 56th For this reason, it is possible in an alternative embodiment of a deformation model 64, only the changes in length of 82, 84 and 86 to overlay each other. The changes in length of 82, 84, 86 and the deflection 92 and 94 can now be added to each other, so that a thermally induced change in position 68 of the machine tool portion 48 can be determined.

In Figure 8, the thus determined change in position of the machine tool portion 48 is shown in a time course. In Figure 8, also a detected during operation of the machine tool 10 real change in position 102 is shown. The actual change in position 102 of the machine tool portion 48 can be measured, for example, interferometers with the aid of a laser.

In Figure 8, also a curve 104 is shown which indicates the difference between the measured respectively at any given time the real change in position 102 and the calculated for this time with the aid of the deformation modeis 64 position change 68th

From Figure 8 it can be seen that the real change in position 102 of the machine tool section 48 can reach values ​​of more than 50 microns. The calculated changes in position 68 differ by only a maximum of less than 10 microns from the real position changes 102nd

Knowing the calculated change in position 68, the drive means 26 of the machine tool section 48 are controlled in consideration of this inverted position change. Thus, a thermally induced change in position of the machine tool section 48 may be compensated at least substantially.

The deviation between the calculated change in position 68 and the actual change in position 102 results from the fact that for the individual model elements 70 to 78 of the deformation Models 64 stationary states will be accepted. Here, a temperature value is correlated linearly with a change in length and / or a displacement. In reality, such a change in length and / or displacement occurs, however, a time lag to a change of a temperature value on, so that the real changes in length and / or displacements are initially smaller than the using the model elements computed changes in length and / or displacements. From Figure 8 it is seen that the calculated changes in position 68 and the real position 102 changes closer to an identical value in a steady-state thermal condition of the machine tool 10 to one another.

The determination and compensation of the change in position 68 has been explained in the form of the workpiece holder 16 using the example of the movable along the z-axis of the machine tool 10 tool machine section 48th A corresponding determination and compensation of changes in position may be alternatively or additionally carried out for the movable along the x-axis and / or the y-axis of the machine tool machine tool sections in the form of the tool carrier 18, the carriage 20 and / or the carriage 22nd

Claims

claims
1. A method for determining a thermally induced change in position (68) of a machine tool section (48) of a machine tool (10), wherein the machine tool section (48) along a tool machine axis (24) is movable, characterized in that a deformation model (64) of the machine tool ( 10) is created, which is based on the machine tool axis (24) a connection between the (to be determined change in position 68) and at least one input variable (66) indicating said at least one input variable (66) at least one temperature value (80, 88, 90) includes fully, and that detects the at least one input variable (66) to determine the thermally induced change in position (68) and in the deformation model (64) is entered.
2. The method according to claim 1, characterized in that the correlation is recognized linear.
3. The method according to claim 1 or 2, characterized in that the deformation model (64) is created independently of an operating state of the machine tool (10).
4. The method according to any one of the preceding claims, characterized in that the at least one input variable (66) is detected during operation of the machine tool (10) and in the deformation model (64) is entered.
5. The method according to any one of the preceding claims, characterized in that the machine tool section (48) comprises at least one workpiece carrier (16) or a workpiece carrier (16) is formed.
6. The method according to any one of the preceding claims, characterized in that the machine tool section (48) comprises at least one tool carrier (18) or by a tool carrier (18) is formed.
7. The method according to any one of the preceding claims, characterized in that the machine tool section (48) at least one carriage (20, 22) or through such a carriage (20, 22) is formed.
8. The method according to any one of the preceding claims, characterized in that the at least one input variable (66) of the deformation model (64) comprises an ambient temperature of the machine tool (10).
includes 9. The method according to any one of the preceding claims, characterized in that the at least one input variable (66) of the deformation model (64) on the machine tool (10) detected reference temperature (80).
10. The method according to claim 9, characterized in that the reference temperature (80) is detected on or in a field of machine tools, which heat sources (54, 56) of the machine tool (10) at least substantially unaffected.
11. The method according to any one of the preceding claims, characterized in that the machine tool (10) comprises at least one machine tool section (50, 52) which is directly or indirectly coupled kinematically with the machine tool section (48).
12. The method according to claim 11, characterized in that the at least one machine tool section (52) is stationary.
formed 13. The method of claim 11 or 12, characterized in that the at least one machine tool section (52) comprises a machine bed (12) and / or a machine frame (14) or by a machine bed (12) and / or a machine frame (14) is.
14. A method according to any one of claims 11 to 13, characterized in that the at least one machine tool (50) comprises a position measuring device (34) for detecting the machine tool section (48) a relative position (100) and a stationary machine tool part (52) or by a such a position measuring device (34) is formed.
15. The method according to claim 14, characterized in that the at least one input variable (66) of the deformation model (64) the relative position (100).
16. The method according to any one of the preceding claims, characterized in that the deformation model (64) contains a the machine tool section (48) associated with model element (70).
17. The method according to claim 16, characterized in that the model element (70) detected a relationship between an ambient temperature of the machine tool (10) and / or on the machine tool (10) the reference temperature (80) on one side and one on the machine tool axis (24) -related change in length (82) of the machine tool section (48) indicating the other.
18. The method according to claim 17, characterized in that the correlation is recognized linear.
19. A method according to any one of the preceding claims, characterized in that the deformation model (64) contains a model element (72, 74) which is associated with a machine tool section (50, 52) which directly or indirectly coupled kinematically with the machine tool section (48) is.
20. The method according to claim 18, characterized in that the model element (72, 74) detected a relationship between an ambient temperature of the machine tool (10) and / or on the machine tool (10) the reference temperature (80) on one side and one (on the machine tool axis 24) related change in length (84, 86) of the machine tool part (50, 52) on the other hand indicates.
21. The method according to claim 20, characterized in that the correlation is recognized linear.
22. The method according to any one of claims 16 to 21, characterized in that by means of different model elements (70, 72, 74) changes in length determined (82, 84, 86) to each other are overlaid.
23. The method according to any one of the preceding claims, characterized in that the machine tool (10) comprises a working chamber (44) and the at least one input variable (66) of the deformation model (64) comprises a working position in space of the machine tool section (48).
24. The method according to any one of the preceding claims, characterized in that the at least one input variable (66) of the deformation model (64) a temperature value (88, 90), which at least one heat source (54, 56) of the machine tool (10) it - sums is.
25. The method according to claim 24, characterized in that the at least one heat source (56) acts directly on the machine tool section (48).
26. The method of claim 24 or 25, characterized in that the at least one heat source (56) is a coupling device (30) by means of which the machine tool section (48) having a drive means (26) for driving the machine tool section (48) is coupled.
27. The method according to any one of claims 24 to 26, characterized in that the at least one heat source (54) directly to a machine tool section (50, 52) acts, which is directly or indirectly coupled kinematically with the machine tool section (48).
28. The method according to any one of claims 24 to 27, characterized in that the at least one heat source (54) is a drive means (26) for driving the machine tool section (48).
29. The method according to any one of claims 24 to 28, characterized in that the deformation model (64) contains at least one model element (76, 78) defining a relationship between a temperature difference and one on the machine tool axis (24) related displacement of the machine tool section (48 ) indicates the temperature difference is determined by the difference of a detected at the at least one heat source (54, 56) temperature value (88, 90) to an ambient temperature of the machine tool (10) and / or (on the machine tool 10) detected reference temperature ( 80).
30. The method according to claim 29, characterized in that the correlation is recognized linear.
31. The method according to claim 30, characterized in that for determining a characterizing the linear relationship coefficients a finite element simulation is performed in which first based on a predetermined characteristic of the heat source (54, 56) one above the machine tool (10) applied temperature distribution and a displacement of the machine tool section (48) is calculated on the basis of this temperature distribution.
32. The method according to claim 31, characterized in that the temperature distribution is stationary.
33. The method according to any one of the preceding claims, characterized in that the deformation model (64), various heat sources (54, 56) of the machine tool (10) in each case separately associated model elements (76, 78).
Shifts determined 34. The method of claim 33, characterized in that with the help of different model elements (76, 78) of the deformation model (64) (92, 94) of the machine tool section (48) are superimposed.
35. A method according to any one of the preceding claims, characterized in that the deformation model (64) contains a the machine tool section (48) associated with model element (70) and / or a model element (72, 74) corresponding to a machine tool section (50, 52) associated with is which is directly or indirectly coupled kinematically with the machine tool section (48), and / or a model element (76, 78) that is associated with a heat source (54, 56) of the machine tool (10), that the deformation model (64) at least two different model elements (70, 72, 74, 76, 78) and that by means of these different model elements (70, 72, 74, 76, 78) certain changes in length (82, 84, 86) and / or displacements (92, 94 ) of the machine tool section (48) and / or the machine tool part (50, 52) to each other are overlaid.
36. A method for compensating a thermally induced change in position (68) of a machine tool section (48) of a machine tool (10), characterized in that a thermally induced change in position (68) of a machine tool section (48) of a machine tool (10) by a method according to any one of preceding claims is determined and that the thermally induced change of position determined in this way (68) is used as control variable for the control of a position changing means of the machine tool section (48).
7. The method according to claim 36, characterized in that for controlling the target position of a target position of the machine tool section (48) a to the specific thermally induced change in position (68) opposite the target position change is superimposed.
PCT/EP2008/062006 2007-09-14 2008-09-10 Method for determining a thermally induced change in position of a machine tool section of a machine tool WO2009037165A1 (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2711126A4 (en) * 2011-05-17 2016-11-30 Jtekt Corp Thermal displacement correction device and thermal displacement correction method

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102009054631A1 (en) 2009-12-14 2011-06-16 Deckel Maho Pfronten Gmbh Method for determining thermally induced change in spatial position of machine tool section, involves comparing values of two spatial positions of machine tool sections, and determining thermally induced change in positions from comparison
DE102010003303A1 (en) * 2010-03-25 2011-09-29 Deckel Maho Seebach Gmbh Method and apparatus for compensating a temperature-dependent change in position on a machine tool

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5623857A (en) 1994-06-16 1997-04-29 Hitachi Seiki Co., Ltd. Method and apparatus for compensating for thermal distortion for a machine tool
WO1997043703A1 (en) * 1996-05-10 1997-11-20 Automated Precision, Inc. Real time machine tool error correction using global differential wet modeling
US6167634B1 (en) 1998-03-28 2001-01-02 Snu Precision Co., Ltd. Measurement and compensation system for thermal errors in machine tools
US6269284B1 (en) 1997-05-09 2001-07-31 Kam C. Lau Real time machine tool error correction using global differential wet modeling
EP1300738A2 (en) 2001-10-02 2003-04-09 Intelligent Manufacturing Systems International Offset apparatus for NC machine tool
DE10312025A1 (en) * 2003-03-18 2004-10-07 Delta-X GmbH Ingenieurgesellschaft Gesellschaft für Strukturanalyse Position control error compensation method for machine, involves compensation mechanism for deformations of processing machines with continuously measuring circuit utilized on basis of finite element method computation

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19848642A1 (en) * 1998-10-22 2000-04-27 Heidenhain Gmbh Dr Johannes Temperature-dependent variation compensation method for machine tool or robot geometry corrects user input commands before conversion from input coordinate system into machine coordinate system

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5623857A (en) 1994-06-16 1997-04-29 Hitachi Seiki Co., Ltd. Method and apparatus for compensating for thermal distortion for a machine tool
WO1997043703A1 (en) * 1996-05-10 1997-11-20 Automated Precision, Inc. Real time machine tool error correction using global differential wet modeling
US6269284B1 (en) 1997-05-09 2001-07-31 Kam C. Lau Real time machine tool error correction using global differential wet modeling
US6167634B1 (en) 1998-03-28 2001-01-02 Snu Precision Co., Ltd. Measurement and compensation system for thermal errors in machine tools
EP1300738A2 (en) 2001-10-02 2003-04-09 Intelligent Manufacturing Systems International Offset apparatus for NC machine tool
DE10312025A1 (en) * 2003-03-18 2004-10-07 Delta-X GmbH Ingenieurgesellschaft Gesellschaft für Strukturanalyse Position control error compensation method for machine, involves compensation mechanism for deformations of processing machines with continuously measuring circuit utilized on basis of finite element method computation

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2711126A4 (en) * 2011-05-17 2016-11-30 Jtekt Corp Thermal displacement correction device and thermal displacement correction method

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