SPINDLE ALIGNMENT AND MACHINE TOOL

Abstract

There is provided a method for aligning a spindle of a machine tool, the spindle having a longitudinal axis and being rotatable about the longitudinal axis. A trial mounting of the spindle is performed, comprising mediately or directly attaching a bearing surface of the spindle to a support surface of the spindle housing. An actual deviation of the spindle is detected. A wedge-shaped adjustment disc is selected, depending on the detected actual deviation. The adjustment disc is arranged between the bearing surface of the spindle and the support surface of the spindle housing in a defined rotation orientation so that the adjustment disc at least partially corrects the actual deviation.

Claims

1. A method for aligning a spindle of a machine tool, the spindle having a longitudinal axis and being rotatable about the longitudinal axis, the method comprising the following steps: performing a trial mounting of the spindle to a spindle housing, comprising mediately or directly attaching a bearing surface of the spindle to a support surface of the spindle housing, detecting an actual deviation of the spindle, selecting a wedge-shaped adjustment disc depending on the detected actual deviation, and arranging the adjustment disc between the bearing surface of the spindle and the support surface of the spindle housing in a defined rotation orientation so that the adjustment disc at least partially corrects the actual deviation.

2. The method of claim 1, wherein the step of detecting an actual deviation of the spindle comprises detecting an actual tilting of the longitudinal axis of the spindle.

3. The method of claim 1, further comprising the following steps: providing a set comprising a plurality of adjustment discs having different wedge thicknesses, and selecting as the adjustment disc for the correction of the actual deviation an adjustment disc of the set whose wedge thickness at least approximately corresponds to the detected actual deviation, or two or more adjustment discs of the set whose combined wedge thickness at least approximately corresponds to the detected actual deviation.

4. The method of claim 3, wherein the step of providing a set comprises providing a set comprising at least three adjustment discs having different wedge thicknesses.

5. The method of claim 4, wherein the wedge thicknesses of the adjustment discs of the set are graduated with respect to each other by a value in the range of between 5 m and 20 m, in relation to an outer diameter of the adjustment discs.

6. The method of claim 1, wherein the adjustment disc has a wedge thickness, measured at an outer diameter of the adjustment disc in a range of between 5 m and 100 m, compared to a plane-parallel disc.

7. The method of claim 1, wherein the adjustment disc has a wedge ratio in the range of 2,000:1 to 100,000:1.

8. The method of claim 1, wherein a plurality of indexed rotation positions for the adjustment disc is provided for the mounting of the adjustment disc between the contact surface of the spindle and the support surface of the spindle housing, and wherein the step of detecting an actual deviation of the spindle also delivers a setting for the rotation position in which the adjustment disc is mounted in the defined rotation orientation.

9. The method of claim 1, wherein the wedge-shaped adjustment disc is mounted in such a way that the error caused by the wedge shape of the adjustment disc counteracts the actual deviation of the spindle.

10. The method of claim 9, wherein the adjustment disc is provided with frontal faces which are minimally inclined with respect to one another, which inclination causes a tilting between the spindle and the spindle housing when the adjustment disc is mounted therebetween in the defined rotary orientation, which tilting counteracts the actual deviation detected in the step of detecting the actual deviation.

11. The method of claim 1, wherein the step of detecting the actual deviation comprises: detecting a deviation of a reference point in two spatial directions in a plane, which is spaced away from the contact surface of the spindle and the support surface of the spindle housing, and which is oriented perpendicular to the longitudinal axis of the spindle.

12. The method of claim 1, wherein the detection of the actual deviation comprises a detection of an actual angular deviation and a detection of an actual rotation position of the actual angular deviation of the spindle.

13. The method of claim 1, wherein the spindle is arranged to be attached to the spindle housing via a mounting plate, wherein the mounting plate is arranged to be interposed between the support surface of the spindle housing and the bearing surface of the spindle.

14. A method for aligning a double spindle of a machine tool comprising a first spindle and a second spindle that are disposed in a common spindle housing, the method comprising the steps of: aligning the first spindle in accordance with the method of claim 1, the alignment being performed with respect to a workpiece support or a traversing axis, and aligning the second spindle in accordance with the method of claim 1, the alignment being performed with respect to the first spindle in order to achieve a desired parallelism between the two spindles.

15. The method of claim 14, further comprising the following step: alignment of the first spindle and the second spindle in a plane that is perpendicular to the longitudinal axis of at least one of the first spindle and the second spindle, wherein a first adjusting element is coupled to the first spindle and the spindle housing, wherein a second adjusting element is coupled to the second spindle and the spindle housing, wherein the first adjusting element is configured to displace the first spindle relative to the spindle housing in a first direction, wherein the second adjusting element is configured to displace the second spindle relative to the spindle housing in a second direction, and wherein the first direction and the second direction are inclined to each other.

16. The method of claim 15, wherein the first adjusting element is a first eccentric, wherein the second adjusting element is a second eccentric, wherein the first eccentric radially engages the first spindle, wherein the second eccentric radially engages the second spindle, and wherein the first direction and the second direction are perpendicular to each other.

17. A use of a set of adjustment discs for aligning a spindle of a machine tool in accordance with the method of claim 1, wherein the set comprises at least three adjustment discs being wedge-shaped and having different wedge thicknesses.

18. A machine tool, comprising: a workpiece support for holding at least one workpiece, and a spindle housing that supports at least one tool spindle which is configured as a spindle for receiving at least one tool and which is rotatable about its longitudinal axis, wherein relative traverse movement can be generated between the workpiece support and the at least one spindle, and wherein the spindle is coupled to a support surface of the spindle housing via an adjustment disc, which is wedge-shaped and which is arranged between the bearing surface of the spindle and the support surface of the spindle housing in a defined rotation orientation so that a deviation of the spindle with respect to the workpiece support is at least partially compensated.

19. The machine tool of claim 18, wherein the adjustment disc comprises a plurality of indexed rotation positions, and wherein the defined rotation orientation of the adjustment disc corresponds to one of the plurality of indexed rotation positions.

20. The machine tool of claim 18, comprising a first spindle and a second spindle which are accommodated at a common spindle housing and aligned parallel to one another, wherein at least one of the first spindle and the second spindle is coupled to a support surface of the spindle housing via the adjustment disc.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0093] Further features and advantages of the disclosure are disclosed by the following description of a plurality of exemplary embodiments, with reference to the drawings, wherein:

[0094] FIG. 1 is a perspective view of an exemplary embodiment of a machine tool, which is designed as a milling machine;

[0095] FIG. 2 is schematic partial view of an embodiment of a machine tool, comprising a spindle unit arranged as a double spindle and a cradle as a tool support;

[0096] FIG. 3 is a perspective partial view of a spindle unit of a machine tool in a partially exploded state;

[0097] FIG. 4 is an enlarged partial section view of the arrangement according to FIG. 3;

[0098] FIG. 5 is a simplified schematic sectional view of an embodiment of a spindle unit having a faulty spindle alignment;

[0099] FIG. 6 is a simplified frontal view of the spindle illustrated in FIG. 5;

[0100] FIG. 7 is a schematic cross-sectional view of a partially assembled spindle unit based on the embodiment illustrated in FIG. 5 to elucidate a set of adjustment discs;

[0101] FIG. 8 is a further schematic sectional view based on the embodiment illustrated in FIG. 5 to illustrate an aligned/adjusted state of the spindle;

[0102] FIG. 9 is a simplified frontal view of the spindle illustrated in FIG. 8;

[0103] FIG. 10 is a perspective partial sectional view of an embodiment of a spindle unit having a double spindle arrangement;

[0104] FIG. 11 is a schematic frontal view of a further embodiment of a spindle unit having a double spindle arrangement

[0105] FIG. 12 is a schematic block diagram illustrating an exemplary embodiment of a method for aligning a spindle; and

[0106] FIG. 13 is a schematic block diagram illustrating an exemplary embodiment of a method for aligning a double spindle of a machine tool.

EMBODIMENTS

[0107] FIG. 1 illustrates, with reference to a perspective view, an exemplary embodiment of a machine tool that is designated in its entirety by 10. By way of example, the machine tool 10 is arranged as a milling machine or milling center. Generally, the machine tool 10 may be designed as a combined lathe/milling machine. The machine tool 10 is arranged for multi-axis machining.

[0108] The machine tool 10 is only shown as a representative of a large number of possible embodiments of machine tools.

[0109] The machine tool 10 comprises a frame 12, which may also be referred to as a bed or base. Furthermore, a housing designated by 14 is provided. Via a safety door 16, a process space 18 of the machine tool 10 can be made accessible. The machine tool 10 also includes a workpiece support 26, which may also be referred to as a workpiece table. The workpiece support 26 comprises, for example, a table 28. In the exemplary embodiment illustrated, the workpiece support 26 supports a workpiece holder 30, which may also be referred to as a fixture.

[0110] The machine tool 10 comprises a spindle unit 36. The spindle unit 36 comprises a spindle housing 38, which can also be referred to as a headstock. The spindle housing 38 carries a motor spindle 40, which is arranged as a workpiece spindle 42. The spindle may also be referred to as main spindle. A tool 44 is mounted to the workpiece spindle 42, for example a tool for milling operations. In addition, the machine tool 10 comprises, by way of example, at least one interchangeable tool 46 and corresponding equipment for changing the tools 44, 46. It goes without saying that the machine tool 10 may include additional handling devices for workpiece change, tool change, measuring tasks and the like. The motor spindle 40 may generally also be referred to as a spindle. Spindles within the meaning of the present disclosure involve at least motor spindles and spindles which can be coupled to a motor and which can be rotatingly driven.

[0111] Various design principles are known for machine tools. By way of example, the machine tool 10 may be arranged as a so-called travelling column machine. Furthermore, a portal design is also conceivable. A gantry design is also known. Further arrangements are conceivable.

[0112] The machine tool 10 merely exemplarily illustrated in FIG. 1 is arranged for and provided with suitable guides and drives to provide movement of the spindle unit 36 provided with the motor spindle 40 and of the tool 44 in at least three axes (spatial directions) X, Y, Z relative to a workpiece supported at the workpiece holder 30, confer the coordinate system X-Y-Z shown in FIG. 1. It goes without saying that further machining axes (for instance swivel axes) are also conceivable.

[0113] The machine tool 10 further comprises a control unit designated by 52. The control unit 52 includes controls 54 and a display 56, by way of example. Further, a signal unit designated by 58 is provided.

[0114] In certain embodiments, the present disclosure is concerned with the alignment of motor spindles and/or workpiece spindles in relation to the respective spindle housing of the spindle unit. A high-precision alignment is necessary for a good machining result, for instance for a high accuracy and dimensional accuracy of the machining operation.

[0115] This applies all the more to machine tools with so-called double spindle arrangements. FIG. 2 elucidates, with reference to a schematic representation, a spindle unit 66 that is arranged as a double spindle. The spindle unit 66 comprises a spindle housing 68, which can also be referred to as a headstock. The spindle housing 68 accommodates a first motor spindle 70 and a second motor spindle 72, each of which can be driven about its longitudinal axis 74, 76 to drive tools 78, 80.

[0116] In certain embodiments, the two motor spindles 70, 72 and/or their longitudinal axes 74, 76 are aligned parallel to each other. In other words, the goal is to achieve a state in which the longitudinal axes 74, 76 are arranged as precisely as possible parallel to the Z axis. Basically, the motor spindles 70, 72 should be aligned as perpendicular as possible with respect to the workpiece support 88. This applies at least to a neutral state (zero position) of the workpiece support 88.

[0117] In the embodiment illustrated in FIG. 2, the workpiece support 88 is arranged as a cradle 90. The cradle 90 has a (driven) swivel axis 92. The swivel axis 92 is parallel to the X axis, by way of example. The cradle 90 comprises a table 94 on which workpiece holders 96, 98 are arranged. For example, each of the workpiece holders 96, 98 supports a workpiece 100, 102, which can be machined by one of the two spindles 70, 72.

[0118] With reference to FIGS. 3-11, various approaches to high-precision positioning and alignment of motor spindles for machine tools are illustrated and explained in more detail.

[0119] It goes without saying that the actual deviations, especially the actual tilts, which are shown in at least some of the figures, are clearly exaggerated for illustrative purposes. In practice, the deviations are often less than 0.05 (angular degree)-down to less than 0.005. This is reflected by the wedge thicknesses and gradations of the adjustment discs. By way of example, an adjustment disc has a wedge thickness of 10 m, 20 m, or 50 m (micrometer), based on a diameter of 250 mm (millimeter). It is thus clear that the shape deviations shown are greatly exaggerated for illustrative purposes.

[0120] FIG. 3 and FIG. 4 illustrate the mounting/attachment of a motor spindle 40 to a spindle housing 38 of a spindle unit 36, with reference to partial representations. The motor spindle 40 and the spindle housing 38 form a component of the spindle unit 36. The motor spindle 40 is at least partially accommodated in the spindle housing 38. For this purpose, the spindle housing 38 is provided with a mounting surface 110, which is exemplarily arranged as a frontal surface. The motor spindle 40 comprises a spindle body 114. In addition, the motor spindle 40 comprises a longitudinal axis of 116.

[0121] Regularly, the motor spindle 40 is aligned with the goal of deliberately aligning this longitudinal axis 116 at right angles to a workpiece support and/or parallel to another axis. Further, a shoulder is formed on the spindle body 114, on which a bearing surface 118 is formed. The bearing surface 118 is arranged as a frontal face. In the exemplary embodiment illustrated in FIGS. 3 and 4, the bearing surface 118 and the support surface 110 point in the same direction. Accordingly, there is no direct contact between the bearing surface 118 and the support surface 110 when the motor spindle 40 is attached to the spindle housing 38. Instead, an indirect attachment is used in this exemplary embodiment.

[0122] The bearing surface 118 defines a Z position of the motor spindle 40. The bearing surface 118 is adjacent to a fitting surface that has a fitting diameter 120. The fitting diameter 120 defines a concentric alignment (e.g. in an X-Y plane) of the motor spindle 40. A tuning ring 124 is provided in the exemplary embodiment for mounting the motor spindle 40. The tuning ring 124 can be deliberately selected to change the Z position of the motor spindle 40 in relation to the spindle housing 38.

[0123] Further, an adjustment disc 128 is provided for mounting the motor spindle 40. In the exemplary embodiment illustrated in FIGS. 3 and 4, the tuning ring 124 and the adjustment disc 128 are concentrically arranged and aligned. Accordingly, by way of example, the adjustment disc 128 forms an outer ring, while the tuning ring 124 forms an inner ring. An opposite allocation is basically also conceivable.

[0124] The adjustment disc 128 comprises frontal faces 130, 132. The frontal face 130 faces the spindle housing 38. The frontal face 132 faces away from the spindle housing 38. Furthermore, the adjustment disc 128 comprises a pitch 134 over its circumference in the form of a defined number of holes/recesses. In this way, a defined rotation orientation of the adjustment disc 128 with respect to the spindle housing 38 can be achieved.

[0125] In the exemplary embodiment, the adjustment disc 128 contacts the mounting surface 110 of the spindle housing 38. Further, the adjustment disc 128 contacts a mounting plate 142. In the exemplary embodiment, also the mounting plate 142 is arranged as a ring. The mounting plate 142 may also be referred to as a motor plate. The mounting plate 142 has a frontal face 144 and a frontal face 146. When mounted, the frontal face 144 faces the mounting surface 110 of the spindle housing 38 and/or the bearing surface 118 of the motor spindle 40. The frontal face 146 faces away from this. Furthermore, the motor spindle 40 comprises a fitting seat 150 on its inside diameter, which is adapted to the fit diameter 120 of the spindle body 114. Accordingly, the mounting plate 142 can be mounted on the spindle body 114.

[0126] The mounting plate 142 further comprises recesses 154, 156 for mounting and connecting spindle housing 38, motor spindle 40, adjustment disc 128, tuning ring 124 and mounting plate 142. Recesses 154 are assigned to the adjustment disc 128, where corresponding counter elements (pitch 134) are provided. Recesses 156 are assigned to the tuning ring 124, where corresponding counter elements are provided. Fastening elements (screws, bolts, pins) are not shown in FIG. 3 and FIG. 4.

[0127] In the mounted state, the adjustment disc 128 contacts the mounting plate 142 with its frontal face 132. The adjustment disc 128 contacts the mounting surface 110 of the spindle housing 38 with its frontal face 130. Furthermore, in the mounted state, the tuning ring 124 is provided between the bearing surface 118 of the spindle body 114 and the frontal face 144 of the mounting plate 142. In case no adjustability in the Z direction is desired, the tuning ring 124 may be dispensed with. In such a state, the frontal face 144 of the mounting plate 142 may directly contact the bearing surface 118.

[0128] It is also possible to form the mounting plate 142 integrally with the spindle body 114. In such a case, embodiments are conceivable in which the adjustment disc 128 is arranged directly between the motor spindle 40 and the spindle housing 38. Accordingly, in such a case the bearing surface 118 would face the support surface 110.

[0129] FIG. 4 illustrates a (not completely) assembled state of the spindle unit 36. The wedge shape of the adjustment disc 128 is illustrated in cross-section by edge thicknesses h1, h2. Furthermore, the gap h illustrates the wedge thickness. The following applies: h=h1h2. Hence, when the mounting plate 142 and therefore the adjustment disc 128 are firmly connected to the spindle housing 38, a tilting would occur between the motor spindle 40 (and/or its longitudinal axis 116) and the spindle housing 38. This tilting is now used to align the motor spindle 40 in the desired fashion, in case of position deviations.

[0130] Such an alignment procedure is illustrated with reference to the schematic, simplified representations of FIGS. 5-9. FIG. 5 elucidates a partial cross-sectional side view of a spindle unit 36, which comprises a motor spindle 40 and which is mounted to a spindle housing 38. Due to manufacturing errors, assembly errors and/or other error influences, the spindle 40 with its longitudinal axis 116 is tilted with respect to a nominal alignment (longitudinal axis 162, which illustrates an ideal alignment). The ideal longitudinal axis 162 may, for example, describe the longitudinal direction of a Z guide for the motor spindle 40 or for a workpiece support. In this respect, this ideal longitudinal axis 162 can provide the reference for the alignment of the motor spindle 40.

[0131] In FIG. 5 the motor spindle 40 is coupled via a mounting plate 142 with the interposition of a parallel ring 166 (plane-parallel ring) to a frontal face of the spindle housing 38. It is proposed to replace the parallel ring 166 by a suitable adjustment disc, which is to be mounted in a suitable rotation orientation. In this way, tilting can be counteracted so that the longitudinal axis 116 of the motor spindle 40 coincides as completely as possible with the nominal longitudinal axis 162 (e.g. longitudinal direction of a Z guide).

[0132] FIG. 5 also illustrates a position securing unit for the motor spindle 40 at the spindle housing 38. This is achieved, for example, by position securing elements 170, which engage in recesses 172. By way of example, the recesses 172 are provided on the spindle body 114. Accordingly, the position securing elements 170 are accommodated at the spindle housing 38. However, this type of position securing does not primarily serve to align the motor spindle with respect to the spindle housing.

[0133] To select a suitable adjustment disc, it is first necessary to detect the actual deviation (actual deviation). This can be achieved, for example, by determining the position of a reference point 176. For this purpose, it is conceivable to mount a measuring mandrel 174 or a similar aid on the tool holder of the motor spindle 40, and to detect, in a defined Z position (AZ), position deviations of a reference point 176 (on the circumference of the measuring mandrel 174) with suitable measuring instruments 194 during the relative movement of the motor spindle 40 to the measuring device. In FIG. 5 and FIG. 8, a relative movement between the measuring mandrel 174 and the measuring instrument 194 in the Z-direction is indicated.

[0134] This may involve, for example, a measurement in X and Y, wherein the spindle 40 is respectively moved relative to the measuring device (in the Z direction) to detect the total error. Then, a deviation of the reference point 176 in the X-direction (X) and the Y-direction (Y) can be determined for the position AZ, confer FIG. 6.

[0135] The measurement is based on the goal of detecting a vector of tilting and/or position deviation. In certain embodiments, the position deviation can be described by few and easily understandable values, such as deviations in the X-direction (X) and the Y-direction (Y). Provided that it is defined and known in which Z-position (Y) the reference point is measured, this information is sufficient.

[0136] FIG. 6 illustrates in this connection the projected partial deviations in X and Y. The scale of the representation in FIG. 6 deviates from the scale of the representation in FIG. 5. In FIG. 6, there is also indicated a circle by a line designated by 178, which may also be referred to as a tolerance circle. The tolerance circle 178 is, so to say, the error that a certain adjustment disc having an appropriate rotation orientation may compensate for. Ideally, the adjustment disc is selected so that the actual error of the reference point 176 (actual error) is on or close to the tolerance circle 178. Furthermore, a marker/indicator for the rotation position is indicated in FIG. 6 by 180. The indicator 180 is important for the correct rotation orientation of the selected adjustment disc. If, for example, the adjustment disc was rotated by 180, i.e. mounted exactly the wrong way round, the error, as the case may be, could even double.

[0137] FIG. 7 illustrates the state according to FIG. 5, wherein the mounting plate 142 and also the parallel ring 166 are detached from the motor spindle 40 and/or from the spindle housing 38. Having knowledge of the actual error of the reference point 176, a suitable instance can now be selected from a set 182 of adjustment discs 184, 186, 188 to compensate for the actual error.

[0138] The adjustment discs 184, 186, 188 of set 182 are graduated and provided with different wedge thicknesses (h=h2h1). The respectively selected adjustment disc can then be mounted between the mounting surface 110 of the spindle housing 38 and the mounting plate 142. In addition, the 142 mounting plate may contact the bearing surface 118 of the spindle body 114 with its frontal face 144, in addition to the selected adjustment disc in the version shown in FIGS. 5-9. In addition, the mounting plate 142 is located via its fitting seat 150 on the fit diameter 120 of the spindle body 114.

[0139] A state after the selection of an adjustment disc 184 and the mounting of the adjustment disc 184 between the spindle housing 38 and the mounting plate 142 for mounting the spindle 40 to the spindle housing 38 is illustrated in FIGS. 8 and 9. The adjustment disc 184 was mounted in a suitable rotation orientation so that the desired nominal position for the longitudinal axis 116 of the motor spindle 40 is achieved. The longitudinal axis 116 coincides with the (ideal) longitudinal axis 162, wherein minimal residual deviations can be present.

[0140] The reference point 176 is now just as close to or even on the ideal longitudinal axis 162. Consequently, the tilting error (for example between the longitudinal axis 116 of the motor spindle and a longitudinal direction of the Z guide) has been significantly reduced. FIG. 9 shows, in comparison with FIG. 6, that with a suitable selection and orientation of the adjustment disc 184, the motor spindle 40 and/or its spindle body 114 can be aligned in such a way that the reference point 176 is now close to the center. The quite large tolerance circle 178 in FIG. 6 has been transformed into a considerably smaller (acceptable) tolerance circle 192 in FIG. 9, due on the mounting of the adjustment disc 184. A significant improvement of the positioning accuracy could be achieved. In FIG. 9 and FIG. 6, adjustment discs and/or parallel rings are not shown separately, for illustrative purposes. FIG. 9 further illustrates that the adjustment disc 184 has been mounted in a certain rotation position (confer indicator 180), i.e. opposite to and/or diametrically with respect to the direction of reference point 176 (actual error). In this way, the adjustment disc 184 can counteract the error.

[0141] In addition, FIG. 8 illustrates, by means of an element designated by 190, a radial prevention device 190 for the motor spindle 40 and/or its spindle body 114 at and/or in the spindle housing 38. The radial prevention device 190 stiffens the spindle in its nominal position and nominal orientation. In certain embodiments, the radial prevention device 190 is considerably spaced away from the end of the motor spindle 40 on the side of the table. In this region, the motor spindle 40 is already fixed to the spindle housing 38 by the mounting plate 142 and the adjustment disc 184.

[0142] FIG. 10 illustrates a perspective partially cross-sectional partial representation of a spindle unit 66, which is arranged as a double spindle (see also FIG. 2). The spindle unit 66 comprises a spindle housing 68, which provides receptacles for two motor spindles 70, 72, which can be rotated around their longitudinal axes 74, 76, respectively. A design goal for the alignment of the longitudinal axes 74, 76 is, on the one hand, the perpendicularity to a workpiece support and/or a table. However, parallelism between the two longitudinal axes 74 and 76 may also be a design goal. However, parallelism between each of the two longitudinal axes 74, 76 and the Z-directioni.e. a traversing axis for the Z-directionmay also be a design goal.

[0143] The spindle 70 is also mounted via a mounting plate 142 at the spindle housing 68. Between mounting plate 142, spindle housing 68 and a contact surface of spindle 70, an adjustment disc 128 is arranged in the manner already described herein before, and, optionally (at least in exemplary embodiments), also a tuning ring 124. The other spindle 72 is mounted in a similar way to the spindle housing 68.

[0144] In addition, reference is made to FIG. 11, which is a simplified schematic front view of a spindle unit 66 having a double spindle (motor spindles 70, 72), see also FIG. 2 and FIG. 10. The spindles 70, 72 are mounted on a spindle housing 68. The spindle unit 66 is movably mounted via its spindle housing 68 on a Z-guide 196.

[0145] FIG. 11 elucidates adjustment options for the X-position and the Y-position of the motor spindles 70, 72. The motor spindle 70 comprises a swivel bearing 198. The motor spindle 72 has a swivel bearing 200. The swivel bearings 198, 200 are each arranged in the circumferential region of the motor spindles 70, 72, and fixedly mounted to the spindle housing 68. Furthermore, an adjusting element 202, 204 is assigned to the respective motor spindle 70, 72. The motor spindle 70 is equipped with an adjusting element 202 which is located opposite the swivel bearing 198. The motor spindle 72 is equipped with an adjusting element 204 which is located opposite the swivel bearing 200.

[0146] The arrangement of the swivel bearing 198 and the adjusting element 202 allows minimal swivel movements of the motor spindle 70 around the swivel bearing 198. In this way, small adjustment movements in the X direction are possible, confer the double arrow 206. The arrangement of the swivel bearing 200 and the adjusting element 204 allows minimal swivel movements of the motor spindle 72 around the swivel bearing 200. In this way, small adjustment movements in the Y direction are possible, confer the double arrow 208.

[0147] The adjusting elements 202, 204 can be equipped with eccentrics which are arranged in corresponding guides (e.g. slotted holes) in order to be able to induce small adjustment movements during a rotary movement, due to the eccentricity. Having concluded the adjustment, the adjusting elements 202, 204 (or spindle bodies of the motor spindles 70, 72) may be fixed to secure the actual position of the motor spindles 70, 72.

[0148] It is to be understood that also an arrangement with a single motor spindle may be similarly provided with at least one adjusting element to allow adjustment movements in at least the X-direction and/or the Y-direction. A synchronous alignment of two motor spindles 70, 72 is of great importance for spindle units 66, which are arranged as a double spindle arrangement. This type of alignment may apply to a defined distance (in X direction) between the two motor spindles 70, 72. Furthermore, a goal of alignment can relate to the positioning of both motor spindles 70, 72 in the same Y-position.

[0149] With reference to FIG. 12, a simplified schematic block diagram is used to illustrate and explain in more detail an exemplary embodiment of a method for aligning a motor spindle of a machine tool.

[0150] The method comprises a step S10, which involves a pre-assembly or trial mounting of a motor spindle to a spindle housing that is adapted to accommodate the motor spindle. For this purpose, the motor spindle is attached directly or mediately to a mounting surface of the spindle housing, at least temporarily. Pre-assembly may include the interposition of spacers (parallel rings).

[0151] This is followed by a step S12, which includes the detection/determination of an actual deviation of the motor spindle. For instance, this involves a determination of a tilting of a longitudinal axis of the motor spindle relative to an ideal nominal position. The nominal position may be a desired perpendicularity with respect to a table for holding workpieces. Furthermore, the nominal position may be a desired parallelism with respect to another longitudinal axis (such as another spindle). Furthermore, the nominal position may be a desired parallelism in relation to a guide of the machine tool, for example in relation to a Z-guide. By way of example, it is conceivable to take up an aid in the form of a measuring mandrel or the like on the motor spindle. The motor spindle is then moved along an axis, such as the Z-axis, relative to the measuring device. The tilting of the spindle can be detected using suitable measuring instruments. In the Z-direction, the measuring point can be distanced from the mounting of the measuring mandrel, so that potential positional errors are more clearly detectable.

[0152] It is conceivable to detect deflections of the measuring mandrel in different spatial directions (X-direction, Y-direction). In this way, having knowledge of the Z position, a total deviation can be determined which describes a present vector of the longitudinal axis of the motor spindle (in relation to the nominal position). Ideally, the determination of the actual deviation results in two easily manageable values (for example, deviation of a reference point in the X direction and in the Y direction).

[0153] The method involves a further step S14, which includes the provision of a set of adjustment discs. The set includes a plurality of adjustment discs. The adjustment discs have a wedge shape. In certain embodiments, at least some of the adjustment discs of the set differ in their wedge thickness. For example, the wedge thickness of the adjustment discs can be in a range from 5 m to 100 m, based on an outer diameter of about 200 mm to 300 mm. A gradation (increment) of the wedge thickness can be at about 5 m to 20 m. It goes without saying that adjustment discs with deviating absolute dimensions are also possible, wherein respective wedge angles can be derived on the basis of the above value pairs, which are reflected in correspondingly adapted wedge thicknesses.

[0154] In other words, the wedge shape may have a wedge ratio (diameter to wedge thickness) that is approximately in the range of between 2,000:1 and 100,000:1. Alternatively, the wedge shape can have a wedge ratio (diameter to wedge thickness) in the range of about 10,000:1 to 60,000:1. Alternatively, the wedge shape can have a wedge ratio (diameter to wedge thickness) in the range of 20,000:1 to 30,000:1. Alternatively, the wedge shape can have a wedge ratio (diameter to wedge thickness) of about 25,000:1. The wedge shape defined in this way corresponds to a certain wedge angle, which can also be specified by the ratio. By combining several adjustment discs, other ranges may be covered. The gradation/increment between the thicknesses of several adjustment discs may also be in similar ranges.

[0155] A step S16 follows, which involves the selection of a suitable adjustment disc from the set of adjustment discs. On the basis of the actual deviation determined in step S12, the most suitable adjustment disc and its rotation position can be easily determined, computationally, on the basis of an algorithm or by means of a diagram. The rotation position is significant so that the wedge-shaped adjustment disc is positioned in a rotation position in which it optimally counteracts the actual deviation.

[0156] After selecting the suitable adjustment disc, the same is mounted in a further step S18 in the defined rotation position directly or mediately between the motor spindle and the spindle housing. In this way, the actual deviation can be significantly reduced. By way of example, the adjustment disc can be coupled directly or mediately with a contact surface of the motor spindle and a mounting surface of the spindle housing. The adjustment disc induces a deliberate error that partially compensates for the error that earlier caused the actual deviation.

[0157] Step S18 is followed by step S20, which comprises the final assembly of the motor spindle on the spindle housing. This may include a position securing for the motor spindle in order to connect it securely and permanently to the spindle housing in the desired orientation. The step S20 may also include other adjustment or alignment operations, such as alignment of the motor spindle in directions transverse to the longitudinal axis (X-direction and/or Y-direction) and/or an alignment of the motor spindle along the longitudinal axis (Z-direction).

[0158] With reference to FIG. 13, a simplified schematic block diagram is used to illustrate and explain in more detail an exemplary embodiment of a method for aligning a machine tool having a double spindle arrangement.

[0159] The method comprises a first step S50 involving the provision of a spindle assembly that is configured as a double spindle. Accordingly, the spindle arrangement comprises a spindle housing and/or a headstock in which receptacles for two motor spindles are provided. Step S50 further involves the provision of two motor spindles of that kind. This may involve motor spindles of the same type. However, the motor spindles in can also be arranged differently. Similar motor spindles are typically used for parallel machining to increase the performance of the machine tool. Different motor spindles can be used, for example, if a machine tool is to be provided that is operable to enable different operations (for example, with different speed levels for different tools).

[0160] In a further step S52, the first one of the two motor spindles is aligned. Alignment may include an alignment of the longitudinal axis of the motor spindle relative to a table and/or workpiece fixture/support. Preferably, the alignment uses at least some of the steps S10 to S20 of the method illustrated with reference to FIG. 12.

[0161] This is followed by another step, S54, which involves aligning the second one of the two motor spindles. Alignment may involve an alignment of the longitudinal axis of the second motor spindle with respect to the longitudinal axis of the first motor spindle. In certain embodiments, the alignment uses at least some of the steps S10 to S20 of the method illustrated with reference to FIG. 12.