Methods for aligning a spindle, methods for aligning a twin spindle, machine tool, and the use of a set of adjusting discs

Abstract

Method for aligning a tool spindle (42) designed as a spindle (40; 70, 72) of a machine tool (10), wherein relative movements can be generated between a workpiece holder (26; 88) for holding at least one workpiece and the spindle (40; 70, 72), wherein the method comprises the following steps: - Trial assembly of the spindle (40; 70, 72) on a spindle housing (38; 68), comprising indirect or direct fastening of a contact surface (118) of the spindle (40; 70, 72) to a receiving surface (110) of the spindle housing (38; 68), - Determining the actual deviation of the spindle (40; 70, 72), - Selection of an adjusting disc (128; 164, 186, 188) depending on the determined actual deviation, wherein the adjusting disc (128; 164, 186, 188) is wedge-shaped, and - Arranging the adjusting disk (128; 164, 186, 188) between the contact surface (118) of the spindle (40; 70, 72) and the receiving surface (110) of the spindle housing (38; 68) in a rotational orientation that at least partially corrects the actual deviation.

Description

[0001] The present disclosure relates to a method for aligning a spindle, for example a motor spindle or a spindle coupled to a motor, of a machine tool, in particular for aligning a tool spindle. Furthermore, the present disclosure relates to a method for aligning spindles of a twin-spindle arrangement of a machine tool. In addition, the present disclosure relates to a corresponding machine tool and uses of a set of adjusting disks for aligning a motor spindle.

[0002] From DE 198 59 360 A1, a machine tool is known that has a twin spindle. Piezo actuators are provided for position correction of the twin spindles. This is intended to enable automatic and adaptive alignment of the spindles. However, it has been shown that such approaches present various challenges in practical implementation, for example, regarding rigidity. This, in turn, has a negative impact on the achievable accuracy.From DE 20 2008 014 645 U1 a machine tool with a machining unit is known, comprising a hollow cylindrical spindle housing, a spindle bushing held in the spindle housing via a front and a rear bearing arrangement, and an electric motor as a direct drive for a work spindle, the radially outer stator of which is attached to the inner wall of the spindle bushing and the rotor of which is attached to the circumferential surface of the work spindle, wherein one of the bearing arrangements holding the spindle bushing in the spindle housing is adjustable and has adjusting means for adjusting the axis alignment of the spindle bushing in the bearing housing.

[0003] German patent DE 1 221 078 A discloses a device for compensating for thermal expansion in a machine tool spindle. The objective is to compensate for temperature changes occurring in the machine parts and milling tools during operation of the machine tool. German patent DE 42 14 935 A1 deals with linear guides and measures for compensating for misalignments, such as parallelism errors. German patent CH 687 782 A5 discloses a method for adjusting a brake disc lathe.

[0004] The alignment of spindles, such as motor spindles or spindles with motors, especially machining spindles (also called main spindles), is of paramount importance for the accuracy achievable with the machine tool. Often, the perpendicularity between the spindle and the workpiece clamping surface is a crucial parameter for accuracy. This is even more true in configurations where two spindles with motors, particularly two tool spindles, are arranged side by side. Such an arrangement is also known as a twin-spindle configuration. The two spindles can be housed in a common casing or in separate casings.

[0005] Twin-spindle arrangements can be used to increase productivity by machining two workpieces in parallel. However, they are also used to perform different machining operations on a single workpiece, for example, with different tools. For many applications, it is essential to ensure that the two spindles are aligned parallel to each other. Only minimal deviations from this parallelism are acceptable.

[0006] Even in setups with only one tool spindle, high accuracy requirements exist for the alignment of the tool spindle relative to a workpiece support, such as a table or cradle. Often, the goal is to align the spindle as perpendicular as possible to a workpiece table or cradle (at least in its neutral position).

[0007] Tool spindles are typically designed as motor spindles. These spindles are often cartridge-type and usually feature integrated drives. They are mounted on a spindle housing. The spindle housing can be a fixed, stationary unit. However, spindle housings are more commonly mounted on movable slides or directly on guideways to allow movement of the spindle and any tool mounted on it relative to the workpiece. Precise alignment of the contact surfaces between the spindle and spindle housing is crucial in this configuration. It is also possible to use spindles that do not have an integrated motor (rotor shaft with tool holder) but are instead coupled to, or capable of being coupled to, a motor. Such spindles can be referred to as spindles with motors.

[0008] For example, a spindle has an axial contact surface and a cylindrical mating surface used for assembly. A mating surface (receiving surface) is provided on the spindle housing. The spindles or spindle bodies are attached directly or indirectly (via intermediate elements) to the spindle housing. For example, a so-called mounting plate (also called a motor plate) is provided, which is positioned between the spindle and the spindle housing.

[0009] The contact surfaces involved in mounting the spindles must be manufactured with high precision. Nevertheless, in practice, (minor) positional and / or geometric deviations can be observed due to manufacturing and assembly processes, which can ultimately lead to incorrect spindle alignment. These are frequently tilting errors of the spindles.

[0010] Therefore, precise spindle alignment is regularly required during assembly. This often involves time-consuming manual tasks. For example, manual alignment includes mounting a measuring mandrel in the tool holder and checking the longitudinal axis of the motor spindle parallel to the travel axis of the spindle housing (e.g., in the Z-direction) using suitable measuring instruments that engage the measuring mandrel. The reference point for the measuring instrument can be, for example, the workpiece support. In this way, any tilting error of the spindle can be determined.

[0011] One way to compensate for this is to (minimally) machine contact surfaces on the spindle housing depending on the determined tilting error, for example by scraping. This is a time-consuming iterative process that places high demands on the qualifications and experience of the operators.

[0012] Against this background, the present disclosure aims to provide a method for aligning a spindle of a machine tool that enables fast yet highly accurate alignment of the spindle, particularly with respect to its longitudinal axis. Preferably, the method allows alignment without additional post-processing / fine machining of the spindle or the spindle housing. Furthermore, the method should be reproducible and, where possible, eliminate the need for additional iteration steps. In particular, the method should be suitable for aligning two spindles of a twin-spindle arrangement. In addition, the present disclosure specifies a machine tool with a highly accurately aligned tool spindle.

[0013] The problem is solved by a method with the features of claim 1. The problem is further solved by a method with the features of claim 11 and by a machine tool with the features of claim 13.

[0014] According to one aspect, the present disclosure relates to a method for aligning a tool spindle designed as a spindle of a machine tool, wherein relative movements can be generated between a workpiece holder for receiving at least one workpiece and the spindle, wherein the method comprises the following steps: - Trial assembly of the spindle on a spindle housing, comprising indirect or direct fastening of a contact surface of the spindle to a receiving surface of the spindle housing, - Determining the actual deviation of the spindle, in particular the actual tilt (inclination error) of a longitudinal axis of the spindle, - Selection of an adjustment disc depending on the determined actual deviation, wherein the adjustment disc is wedge-shaped, and - Arranging the adjusting disc between the contact surface of the spindle and the receiving surface of the spindle housing in a rotational orientation that at least partially corrects the actual deviation.

[0015] According to the invention, the adjusting washers allow for highly accurate alignment and positioning of the spindle without manual rework at the spindle seat on / in the spindle housing. This significantly reduces the effort required for spindle alignment. Highly accurate alignment can nevertheless be achieved by selecting a suitable adjusting washer.

[0016] The rotational orientation of the adjusting disc is preferably chosen such that the “error” introduced by the adjusting disc due to its circular design counteracts the actual deviation.

[0017] Following the positioning of the adjusting washer between the spindle's mounting surface and the spindle housing's receiving surface, the spindle can be finally mounted and secured. The term "between" should not be interpreted restrictively to mean that the adjusting washer must be positioned precisely and directly between the spindle's mounting surface and the spindle housing's receiving surface. Rather, the term "between" is not strictly structural but functional in nature.

[0018] The adjusting disc is wedge-shaped. It comprises opposing end faces that are not parallel to each other. In other words, the wedge shape is evident in a side view or a cross-section of the adjusting disc. This means the adjusting disc is not necessarily eccentric. Instead, for example, the end faces may be slightly inclined relative to each other in the longitudinal direction (of the spindle), creating a tilt between the spindle and the spindle housing that counteracts the actual deviation. Other designs are conceivable.

[0019] The actual tilt can be determined with respect to a workpiece fixture (workpiece support, clamping surface, etc.). In other words, the actual deviation can describe a deviation (of the position and orientation of the spindle axis) from the desired ideal perpendicularity between the spindle and the clamping surface. Furthermore, the actual deviation can also describe a parallelism error (tilt error) between two spindles. The actual tilt can also be determined with respect to a travel axis of a relative movement between the spindle housing and the workpiece fixture (e.g., in the Z-direction).

[0020] Generally, the adjusting disc has only a minimal wedge shape. Deviations of less than 100 µm (micrometers) are typical, for example, based on an outer diameter of the adjusting disc between 200 mm and 300 mm (millimeters). The ratio between the wedge thickness and the diameter of the adjusting disc corresponds to a wedge angle. Wedge thicknesses for other diameters can be determined based on this wedge angle. The wedge angles are very small. The adjusting discs can be manufactured with high precision using suitable fine or ultra-fine machining processes. The adjusting disc introduces a deliberate error into the system, which at least partially compensates for the actual deviation.

[0021] The spindle housing can also be referred to as the spindle casing. The spindle housing forms an outer casing that accommodates, for example, a cartridge-style spindle. The spindle itself comprises a spindle body with a housing. Accordingly, drives, bearings, output shafts, tool holders, etc., can be arranged within the spindle body.

[0022] The actual deviation can be attributed to manufacturing tolerances and / or assembly tolerances. Such defects can occur in both the spindle housing and the spindle itself.

[0023] The spindle can be mounted indirectly to the spindle housing, for example via a so-called motor plate / mounting plate. Direct mounting is also conceivable.

[0024] The adjusting disc has (minimally) inclined end faces. Macroscopically, the end faces can appear almost parallel. Nevertheless, the adjusting discs exhibit a minimal wedge shape. The direction of the wedge is indicated, for example, by an indicator element. The adjusting disc can be designed as a (thin) ring that is positioned between the spindle housing and the motor plate.

[0025] The longitudinal axis of the spindle is ideally parallel to a Z-axis (e.g., a travel axis extending in Z), provided there is no tilting error. Accordingly, one alignment goal is to align the spindle as perpendicular as possible to a plane defined by an X-axis and a Y-axis.

[0026] The actual deviation (of the spindle's longitudinal axis) can be determined, for example, by using a dial gauge or similar device coupled to a measuring mandrel that is mounted on the spindle. The dial gauge is appropriately coupled to a reference element (workpiece clamping surface, adjacent spindle, etc.).

[0027] For example, the dial gauge can be arranged and aligned to detect deviations in the Y-direction. These deviations can be detected by generating a Z-movement between the spindle and a workpiece support. The dial gauge then determines deviations in the Y-direction during this relative movement (in Z).

[0028] Furthermore, the dial gauge can be arranged and aligned in such a way that deviations in the X-direction are detected. These X-direction deviations can be detected by generating a Z-movement between the spindle and a workpiece support. The dial gauge then determines deviations in the X-direction during this relative movement (in Z).

[0029] From the deviations in the Y-direction and the deviations in the X-direction, a vector can ultimately be derived that describes the tilt. Due to their slight wedge shape, the adjusting shims exhibit defined deviations which, depending on the shim's rotational position, at least partially compensate for the spindle's tilt. The wedge shape also defines a vector representing the "tilt" of the adjusting shim. These two vectors can be aligned relative to each other during shim mounting to achieve the most complete compensation possible.

[0030] Therefore, an algorithm or suitable set of tables is proposed to simplify the selection of adjusting shims and their rotational orientation. The goal of selection is often to minimize residual deviation after mounting the adjusting shim. Complete elimination of the error is generally neither possible nor necessary. Residual errors are caused, for example, by the limited number of rotational positions of the adjusting shim or by the varying thicknesses of the wedges.

[0031] According to an exemplary design, the procedure further comprises the following steps: - Provision of a set with a plurality of adjusting washers with different wedge thicknesses, - Selection of the adjusting disc for the correction whose wedge thickness corresponds at least approximately to the determined actual deviation.

[0032] In this way, by providing a manageable number of adjusting washers with different wedge thicknesses, a suitable adjusting washer can be provided for a considerable range of possible deviations to correct the spindle orientation. It goes without saying that in cases of larger deviations, it is also possible to install multiple adjusting washers whose wedge shapes are cumulative.

[0033] According to another exemplary embodiment, the method further comprises providing a set of at least three adjusting washers with different wedge thicknesses. It is understood that sets with four, five, or even more adjusting washers with different wedge thicknesses are also conceivable. If a machine tool with a twin-spindle arrangement is involved, twice the number of adjusting washers of the respective types can also be provided. The adjusting washers in the set can be adapted to expected manufacturing / assembly tolerances.

[0034] Preferably, a table or a software-implemented algorithm is provided, based on which the respective adjusting disc, including the proposed rotational orientation, can be easily selected from the set of adjusting discs. The input for the selection is the previously determined actual deviation. The actual deviation embodies, in a sense, the actual vector or the actual tilt of the spindle's longitudinal axis. It is understood that the actual deviation can also be described by ΔX (Delta X) and ΔY (Delta Y) values, which describe deviations of a defined point (with a defined Z-position) on the longitudinal axis from an imaginary ideal longitudinal axis. The actual vector can also be described in this way.

[0035] According to another exemplary embodiment of the method, the wedge thicknesses of the adjusting discs of the set, based on an outer diameter of the adjusting discs, are each stepped from one another by a value of approximately 5 µm to 20 µm. The increment is therefore, for example, 5 µm to 20 µm. In this way, there are fine gradations between the adjusting discs.

[0036] In this way, minor residual deviations can be compensated for. The wedge thickness is the difference in height (thickness) of the disc at two opposite ends, one with the minimum thickness and the other with the maximum thickness. A typical outer diameter for adjusting shims is approximately 200-300 mm, for example, around 250 mm.

[0037] There is only a small increment between two successive adjustment discs in a set. This allows for high accuracy, as the error caused by the step size can be minimized.

[0038] According to another exemplary embodiment of the method, the wedge thickness of an adjusting disk, relative to an outer diameter of the adjusting disks, lies in a range between 5 µm and 100 µm compared to a plane-parallel disk. In this way, considerable deviations can be compensated for, and even relatively small deviations can be further reduced.

[0039] According to the definition above, a plane-parallel disk has a wedge thickness of 0 µm. However, as soon as the opposite end faces of the adjusting disk are slightly inclined towards each other, the wedge thickness becomes greater than 0 µm. Preferably, one of the two end faces is aligned exactly perpendicular to the central axis through the adjusting disk. Accordingly, the other end face is slightly tilted or inclined relative to it.

[0040] According to another exemplary embodiment, a plurality of defined rotational positions are provided for the adjusting disk between the contact surface of the spindle and the receiving surface of the spindle housing. These positions can be, for example, a corresponding number of recesses (through holes) for fastening elements. For example, a rotational increment of 30° or 15° is provided. This corresponds to 12 or 24 recesses.

[0041] Similar to a clock, the rotational orientation of the adjusting disc can then be specified. The orientation and locking of the rotational position can be achieved using pins, screws, bolts, and corresponding counter-elements.

[0042] Given a specific deviation from the actual value, the algorithm or table recommends an adjusting washer of a certain wedge thickness, to be installed in a specific rotational position (for example, the "9 o'clock position"). This significantly simplifies the alignment and adjustment process. The optimization task aims to minimize the residual error after the adjusting washer is installed.

[0043] According to another exemplary embodiment of the method, the wedge disk is mounted such that the error attributable to the wedge shape of the adjusting disk is opposite to the actual deviation of the spindle. This preferably applies at least within the increments defined by the gradation of the wedge thicknesses and the defined number of rotational positions (angular position).

[0044] According to another exemplary embodiment of the method, determining the actual deviation involves measuring, at least approximately, the deviation of a reference point in two spatial directions in a plane spaced apart from the spindle's contact surface and the spindle housing's receiving surface, and oriented perpendicular to the spindle's longitudinal axis. In this way, the deviation's "vector" can be determined. The deviations in X and Y can be determined, for example, using a dial gauge or similar measuring instrument that engages a measuring mandrel or similar element while the latter is moved in a defined manner by the spindle. If the Z-position of the reference point is fixed or even predefined, the actual deviation can be determined based on just two values ​​(ΔX and ΔY), with the result being the selection of the adjusting shim and its installation position.

[0045] According to another exemplary embodiment of the method, determining the actual deviation includes recording the actual angular deviation and the actual rotational position of the spindle's angular deviation. The actual deviation (tilt error) can also be determined in this way. According to this approach, the actual vector (tilt of the spindle's longitudinal axis) is measured directly. The information about the actual deviation therefore includes an angle (tilt angle relative to an ideal orientation of the longitudinal axis) as well as a rotational position ("clockwise") in which the tilt is clearly evident.

[0046] According to another exemplary embodiment of the method, the spindle is attached to the spindle housing via a mounting plate, the mounting plate being connected to the receiving surface of the spindle housing and the contact surface of the spindle. Accordingly, the spindle is not directly connected to the spindle housing via its spindle body but indirectly via a (possibly separate) mounting plate.

[0047] According to a further exemplary embodiment of the method, a suitable tuning ring is selected to adjust / align the position in the Z-direction depending on a measured Z-deviation. The tuning ring is interposed between the spindle and the spindle housing. Accordingly, the spindle is mounted using both the adjusting disk and the tuning ring. The adjusting disk compensates for the tilting error of the longitudinal axis. The tuning ring compensates for any deviations in the Z-direction. The tuning ring is therefore designed to be plane-parallel.

[0048] According to an exemplary embodiment, the spindle is therefore coupled to the spindle housing via the adjusting disc, the mounting plate and the tuning ring.

[0049] According to one exemplary embodiment, the spindle is mounted such that the tuning ring and the adjusting disc are arranged concentrically (one inside the other), with both the tuning ring and the adjusting disc being connected to the mounting plate at their end faces. The tuning ring contacts the spindle's contact surface with its opposite end face, and the adjusting disc contacts the receiving surface of the spindle housing with its opposite end face. The connection between the spindle housing and the spindle is thus made via the adjusting disc, the mounting plate, and the tuning ring. In this embodiment, the tuning ring is arranged inside the adjusting disc. However, the reverse is also conceivable. Accordingly, the inner ring can have a wedge shape, and the outer ring can be designed to be plane-parallel.

[0050] According to another exemplary embodiment, the tuning ring and the adjusting disc form an axial unit. However, it is also conceivable to compensate for both tilting errors and positional errors in the Z-direction via the adjusting disc. Accordingly, the tuning ring and adjusting disc would be combined into a single component.

[0051] According to another exemplary embodiment, the spindle is alternatively or additionally aligned in a plane perpendicular to its longitudinal axis by at least one adjusting element. This allows for adjustment of the X-position or the Y-position. The adjusting element can be, for example, an eccentric or the like. Typically, only small strokes / travel distances are required to achieve the desired alignment. For example, such an adjusting element is arranged circumferentially, such as on / near the mounting plate. A bearing element (such as a pin or the like) is provided on an opposite circumferential section. Movement of the adjusting element (such as the eccentric) causes a slight pivoting of the spindle about the bearing element. In this way, minimal adjustments to the X-position or the Y-position can be made.

[0052] Particularly in a design with a twin spindle, it is conceivable to provide one spindle with an adjusting element for X-direction adjustments and the other spindle with an adjusting element for Y-direction adjustments. Accordingly, the adjusting elements on their respective spindles are positioned approximately 90° apart circumferentially compared to the other spindle. The adjustability in the X- and Y-directions allows for precise positioning of the longitudinal axes of both spindles. Therefore, in a twin spindle design, the parallelism, as well as the Z-alignment and the alignment in the X and Y directions of both spindles, can be optimized.

[0053] According to another aspect, the present disclosure relates to a method for aligning a twin spindle of a machine tool, which has a first spindle and a second spindle arranged in a common spindle housing, comprising the following steps: - Alignment of the first spindle according to the method of one of the embodiments described herein, wherein the alignment is carried out relative to the workpiece holder or a traversing axis, and - Alignment of the second spindle according to the method of one of the embodiments described herein, wherein the alignment is carried out relative to the first spindle in order to achieve a desired parallelism between the two spindles.

[0054] In this way, two adjacent spindles can be aligned with high precision. According to a further exemplary embodiment, the method also includes a step for alignment in the Z-direction. According to a further exemplary embodiment, the method also includes a step for alignment in the Z-direction as well as the X-direction and / or the Y-direction.

[0055] According to another exemplary embodiment, the method further comprises the following step: - Alignment of the first spindle and the second spindle in a plane perpendicular to the spindle axis, wherein a first adjusting element, in particular a first eccentric, is associated with the first spindle and the spindle housing, wherein a second adjusting element, in particular a second eccentric, is assigned to the second spindle and the spindle housing, wherein the first actuating element is designed to displace the first spindle relative to the spindle housing in a first direction, wherein the second actuating element is designed to displace the second spindle relative to the spindle housing in a second direction, and wherein the first direction and the second direction are oriented obliquely to each other, preferably perpendicular to each other.

[0056] In this way, positioning can be achieved in a plane parallel to the X-axis and the Y-axis. This allows for the setting of a desired relative position or orientation between the two spindles.

[0057] Furthermore, the present disclosure relates to a machine tool, in particular a multi-axis milling machine, which has the following features: - a frame, - a workpiece holder for holding at least one workpiece, and - a spindle housing that carries at least one tool spindle designed as a spindle for receiving at least one tool, which can be driven about its longitudinal axis, wherein relative movements can be generated between the workpiece holder and the at least one tool spindle, and wherein the tool spindle is coupled via an adjusting disk to a receiving surface of the spindle housing, which is wedge-shaped and arranged in a rotational orientation between the contact surface of the tool spindle and the receiving surface of the spindle housing, so that a deviation of the tool spindle, in particular an actual tilting of a longitudinal axis of the spindle, with respect to the workpiece holding is at least partially compensated.

[0058] According to an exemplary embodiment, the machine tool has a first spindle and a second spindle which are mounted on a common spindle housing and aligned parallel to each other, wherein at least the first spindle or the second spindle is coupled to a receiving surface of the spindle housing via an adjusting disk.

[0059] Such a twin-spindle arrangement is suitable for the parallel machining of two workpieces. Furthermore, different machining operations can be carried out in this way, requiring different parameters (speed, etc.) and / or different tools.

[0060] Furthermore, the present disclosure relates to the use of a set of adjusting washers for aligning a spindle of a machine tool. In particular, the set of adjusting washers is used in at least one embodiment of the disclosed method.

[0061] It is understood that the features mentioned above and those to be explained below can be used not only in the combinations specified, but also in other combinations or on their own, without leaving the scope of the present invention.

[0062] Further features and advantages of the invention will become apparent from the following description and explanation of several exemplary embodiments with reference to the drawings. These show: Fig. 1 a perspective view of an exemplary embodiment of a machine tool designed as a milling machine; Fig. 2 a schematic partial view of an embodiment of a machine tool, comprising a spindle unit designed as a double spindle and a cradle as a tool support; Fig. 3 a perspective partial view of a spindle unit of a machine tool in a partially exploded state; Fig. 4 an enlarged partial sectional view of the arrangement according to Fig. 3; Fig. 5 a simplified schematic sectional view of an embodiment of a spindle unit with a defective spindle alignment; Fig. 6 a simplified front view of the in Fig. 5 illustrated spindles; Fig. 7 a schematic sectional view of a partially assembled spindle unit based on the in Fig. 5 illustrated embodiment to demonstrate a set of adjusting washers; Fig. 8 another schematic sectional view based on the one in Fig. 5 illustrated embodiment to demonstrate an aligned / adjusted state of the spindle; Fig. 9 a simplified front view of the in Fig. 8 illustrated spindles; Fig. 10 a perspective partial sectional view of an embodiment of a spindle unit with a twin spindle arrangement; Fig. 11 a schematic front view of another embodiment of a spindle unit with a double spindle arrangement Fig. 12 a schematic block diagram to illustrate an exemplary embodiment of a method for aligning a spindle; and Fig. 13 A schematic block diagram illustrating an exemplary embodiment of a method for aligning a twin spindle of a machine tool.

[0063] Fig. Figure 1 illustrates an exemplary embodiment of a machine tool designated 10, using a perspective view. For example, the machine tool 10 is configured as a milling machine or milling center. More generally, the machine tool 10 can be configured as a combined lathe / milling machine. The machine tool 10 is designed for multi-axis machining.

[0064] The machine tool 10 is shown only as representative of a large number of possible designs of machine tools.

[0065] The machine tool 10 comprises a frame 12, which can also be referred to as a bed or foundation. Furthermore, an enclosure designated 14 is provided. A process chamber 18 of the machine tool 10 can be accessed via a protective door 16. The machine tool 10 also comprises a workpiece holder 26, which can also be referred to as a workpiece support. The workpiece holder 26 includes, for example, a table 28. In the illustrated embodiment, the workpiece holder 26 supports a workpiece clamping device 30, which can also be referred to as a clamping fixture.

[0066] The machine tool 10 comprises a spindle unit 36. The spindle unit 36 ​​has a spindle housing 38, which can also be referred to as a spindle case. The spindle housing 38 carries a motor spindle 40, which is designed as a workpiece spindle 42. The spindle can also be referred to as the main spindle. A tool 44, for example a tool for milling operations, is mounted on the workpiece spindle 42. Furthermore, the machine tool 10 has, for example, at least one interchangeable tool 46 and corresponding devices for changing the tools 44, 46. It is understood that the machine tool 10 may include further handling devices for workpiece changing, tool changing, measuring tasks, and the like. The motor spindle 40 can also generally be referred to as a spindle. Spindles within the meaning of this disclosure include at least motor spindles and rotary spindles that can be coupled to a motor.

[0067] Various design principles for machine tools are known. For example, machine tool 10 can be designed as a so-called traveling column machine. Furthermore, a portal design is also conceivable. Gantry designs are also known. Other designs are imaginable.

[0068] The in Fig. 1. The machine tool 10, illustrated only as an example, is designed and equipped with suitable guides and drives to enable movement of the spindle unit 36 ​​with the motor spindle 40 and the tool 44 in at least 3 axes (spatial directions) X, Y, Z relative to a workpiece that is held in the workpiece holder 30, compare the figure in Fig. The coordinate system shown is XYZ. It is understood that other machining axes (especially swivel axes) are also conceivable.

[0069] The machine tool 10 also has a control unit designated 52. The control unit 52 includes, for example, operating elements 54 and a display 56. Furthermore, a signal unit designated 58 is provided.

[0070] The present disclosure relates in particular to the alignment of motor spindles or workpiece spindles with respect to the respective spindle housing of the spindle unit. Highly precise alignment is necessary for a good machining result, especially for high accuracy and dimensional stability of the machining.

[0071] This is especially true for machine tools with so-called twin-spindle arrangements. Fig. Figure 2 illustrates, using a schematic diagram, the design of a spindle unit 66, which is configured as a double spindle. The spindle unit 66 has a spindle housing 68, which can also be referred to as a spindle case. The spindle housing 68 carries 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.

[0072] The two motor spindles 70, 72, or rather their longitudinal axes 74, 76, are preferably aligned parallel to each other. In other words, a state is sought in which the longitudinal axes 74, 76 are arranged as precisely as possible parallel to the Z-axis. In principle, the motor spindles 70, 72 should be aligned as perpendicular as possible to the workpiece support / workpiece holder 88. This applies at least to a neutral state (zero position) of the workpiece holder 88.

[0073] In the Fig. In the illustrated embodiment 2, the workpiece holder 88 is designed as a cradle 90. The cradle 90 has a (driven) swivel axis 92. The swivel axis 92 is, for example, parallel to the X-axis. The cradle 90 has a table 94 on which workpiece holders 96, 98 are arranged. By way of example, each of the workpiece holders 96, 98 carries a workpiece 100, 102, which can be machined by one of the two spindles 70, 72.

[0074] With reference to the Fig. Sections 3-11 illustrate and explain in more detail various approaches to the high-precision positioning and alignment of motor spindles for machine tools.

[0075] It is understood that the actual deviations, especially the actual tilts, shown in at least some of the figures, are significantly exaggerated for illustrative purposes. In practice, the deviations are often less than 0.05° (degrees) – down to less than 0.005°. This is evident from the wedge thicknesses and increments of the adjustment shims. For example, an adjustment shim has a wedge thickness of 10 µm, 20 µm, or 50 µm (micrometers), based on a diameter of 250 mm (millimeters). This illustrates that the depicted shape deviations are greatly exaggerated for illustrative purposes.

[0076] Fig. 3 and Fig. Figure 4 illustrates, using partial diagrams, the assembly / fastening of a motor spindle 40 to a spindle housing 38 of a spindle unit 36. 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 enclosed in the spindle housing 38. For this purpose, a receiving surface 110 is formed on the spindle housing 38, which is designed as an end face by way of example. The motor spindle 40 has a spindle body 114. Furthermore, the motor spindle 40 has a longitudinal axis 116.

[0077] The alignment of the motor spindle 40 is regularly carried out with the aim of deliberately aligning this longitudinal axis 116 perpendicular to a workpiece support and / or parallel to another axis. A shoulder is also formed on the spindle body 114, on which a contact surface 118 is formed. The contact surface 118 is designed as an end face. In the embodiment according to the Fig. 3 and Fig. Figure 4 shows that the contact surface 118 and the receiving surface 110 point in the same direction. Accordingly, there is no direct contact between the contact surface 118 and the receiving surface 110 when the motor spindle 40 is attached to the spindle housing 38. Instead, in this embodiment, an indirect attachment takes place.

[0078] The mounting surface 118 defines a Z-position of the motor spindle 40. Adjacent to the mounting surface 118 is a mating surface with a mating diameter 120. The mating diameter 120 defines a concentric orientation (e.g., in an XY plane) of the motor spindle 40. In the exemplary embodiment, an adjustment ring 124 is provided for mounting the motor spindle 40. The adjustment ring 124 can be deliberately selected to change the Z-position of the motor spindle 40 relative to the spindle housing 38.

[0079] Furthermore, an adjusting disc 128 is provided for mounting the motor spindle 40. In the exemplary embodiment according to the Fig. 3 and Fig. In section 4, the tuning ring 124 and the adjusting disc 128 are designed and aligned concentrically. Accordingly, the adjusting disc 128 forms an outer ring, while the tuning ring 124 forms an inner ring. A reverse arrangement is also conceivable.

[0080] The adjusting disc 128 has end faces 130 and 132. End face 130 faces the spindle housing 38. End face 132 faces away from the spindle housing 38. Furthermore, the adjusting disc 128 has a graduation 134 around its circumference in the form of a defined number of holes / recesses. In this way, a defined rotational orientation of the adjusting disc 128 relative to the spindle housing 38 can be achieved.

[0081] In the exemplary embodiment, the adjusting disc 128 contacts, on the one hand, the receiving surface 110 of the spindle housing 38. On the other hand, the adjusting disc 128 contacts a mounting plate 142. In the exemplary embodiment, the mounting plate 142 is also ring-shaped. The mounting plate 142 can also be referred to as the motor plate. The mounting plate 142 has an end face 144 and an end face 146. In the assembled state, the end face 144 faces the receiving surface 110 of the spindle housing 38 or the contact surface 118 of the motor spindle 40. The end face 146 faces away from this. Furthermore, the motor spindle 40 has a mating seat 150 on its inner diameter, which is adapted to the mating diameter 120 of the spindle body 114. Accordingly, the mounting plate 142 can be slipped onto the spindle body 114.

[0082] The mounting plate 142 further features recesses 154 and 156 for fastening and connecting the spindle housing 38, motor spindle 40, adjusting disc 128, tuning ring 124, and the mounting plate 142. Recesses 154 are assigned to the adjusting disc 128, where corresponding mating elements (pitch 134) are provided. Recesses 156 are assigned to the tuning ring 124, where corresponding mating elements are provided. Fastening elements (screws, bolts, pins) are provided in Fig. 3 and Fig. 4 not shown.

[0083] In the assembled state, the adjusting disc 128 contacts the mounting plate 142 with its end face 132. The adjusting disc 128 contacts the receiving surface 110 of the spindle housing 38 with its end face 130. Furthermore, in the assembled state, the tuning ring 124 is provided between the contact surface 118 of the spindle body 114 and the end face 144 of the mounting plate 142. If no tuning option in the Z-direction is required, the tuning ring 124 can be omitted. In such a state, the end face 144 of the mounting plate 142 could contact the contact surface 118 directly.

[0084] It is also conceivable to design the mounting plate 142 integrally with the spindle body 114. In such a case, embodiments are conceivable in which the adjusting disk 128 is arranged directly between the motor spindle 40 and the spindle housing 38. Accordingly, in such a case, the contact surface 118 would face the receiving surface 110.

[0085] Fig. Figure 4 illustrates a (not fully) assembled state of the spindle unit 36. The wedge shape of the adjusting disk 128 is illustrated in cross-section by the edge thicknesses h1, h2. Furthermore, the "gap" Δh illustrates the wedge thickness. Δh = h1 - h2. Therefore, if the mounting plate 142 and consequently the adjusting disk 128 were rigidly connected to the spindle housing 38, a tilting motion would occur between the motor spindle 40 (or its longitudinal axis 116) and the spindle housing 38. This tilting motion is used to align the motor spindle 40 as desired in the event of positional deviations.

[0086] Such an alignment process is described using the schematic, simplified representations of the Fig. 5-9 illustrated. Fig. Figure 5 illustrates a partially cutaway side view of a spindle unit 36 ​​with a motor spindle 40 mounted on a spindle housing 38. Due to manufacturing defects, assembly errors, and / or other fault influences, the spindle 40 is tilted with its longitudinal axis 116 relative to a target orientation (longitudinal axis 162, illustrating an ideal orientation). The ideal longitudinal axis 162 can, for example, describe the longitudinal direction of a Z-guide for the motor spindle 40 or for a workpiece holder. In this respect, this ideal longitudinal axis 162 can provide the reference for the orientation of the motor spindle 40.

[0087] In Fig. In section 5, the motor spindle 40 is coupled to an end face of the spindle housing 38 via a mounting plate 142 and an intermediate parallel ring 166 (plane-parallel ring). It is proposed to replace the parallel ring 166 with a suitable adjusting disk, which is to be mounted in a suitable rotational 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 desired longitudinal axis 162 (for example, the longitudinal direction of a Z-axis guide).

[0088] Fig. Figure 5 further illustrates a position locking mechanism for the motor spindle 40 on the spindle housing 38. This is achieved, for example, by means of position locking elements 170 that engage in recesses 172. The recesses 172 are provided on the spindle body 114 as an example. Accordingly, the position locking elements 170 are accommodated on the spindle housing 38. However, this type of position locking mechanism does not primarily serve to align the motor spindle relative to the spindle housing.

[0089] To select a suitable adjusting disc, it is first necessary to determine the actual deviation (actual deviation). This can be done, 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, in a defined Z-position (ΔZ), during the relative movement of the motor spindle 40 to the measuring device, to record positional deviations of a reference point 176 (on the circumference of the measuring mandrel 174) with suitable measuring instruments 194. Fig. 5 and Fig. Figure 8 indicates a relative movement between the measuring mandrel 174 and the measuring instrument 194 in the Z direction.

[0090] This can, for example, include a measurement in X and Y, whereby the spindle 40 is moved relative to the measuring device (in the Z direction) in each case to capture the total error. Then, for position ΔZ, a deviation of the reference point 176 in the X direction (ΔX) and the Y direction (ΔY) can be determined; see [reference]. Fig. 6.

[0091] The measurement aims to capture a vector of tilt or positional deviation, whereby the positional deviation is preferably describable by a few easily understandable values, such as deviations in the X-direction (ΔX) and the Y-direction (ΔY). If the Z-position (ΔY) at which the measurement of the reference point is performed is defined and known, this information is sufficient.

[0092] Fig. Figure 6 illustrates the projected partial deviations in X and Y in this context. The scale of the representation in Fig. 6 deviates from the scale of the representation in Fig. 5 from. In Fig. Figure 6 also indicates a circle, labeled 178, which can also be called the tolerance circle. The tolerance circle 178 represents, in a sense, the error that a specific adjusting disk can compensate for when rotated accordingly. Ideally, the adjusting disk is selected such that the actual error of the reference point 176 (actual error) lies on or near the tolerance circle 178. Furthermore, in Fig. The number 6 with 180 indicates a marker / indicator for the rotational position. The 180 indicator is important for the correct rotational orientation of the selected adjusting disc. If the adjusting disc is rotated by 180°, i.e., mounted exactly the wrong way around, the error could potentially even double.

[0093] Fig. Figure 7 illustrates the condition according to Fig. 5, wherein the mounting plate 142 and also the parallel ring 166 are detached from the motor spindle 40 and the spindle housing 38, respectively. Knowing the actual error of the reference point 176, a suitable specimen can now be selected from a set 182 of adjusting washers 184, 186, 188 to compensate for the actual error.

[0094] The adjusting washers 184, 186, 188 of set 182 are stepped and provided with different wedge thicknesses (Δh = h2 - h1). The selected adjusting washer can then be mounted between the receiving surface 110 of the spindle housing 38 and the mounting plate 142. Furthermore, the mounting plate 142 can be mounted with its end face 144 next to the selected adjusting washer in the embodiment according to the Fig. 5-9 also contact the contact surface 118 of the spindle body 114. The mounting plate 142 sits next to it via its locating fit 150 on the locating diameter 120 of the spindle body 114.

[0095] A state after selecting an adjusting disc 184 and mounting the adjusting disc 184 between the spindle housing 38 and the mounting plate 142 for receiving the spindle 40 on the spindle housing 38 is described in the Fig. 8 and Fig. Figure 9 illustrates this. The adjusting disk 184 was mounted in a suitable rotational orientation so that the desired target position for the longitudinal axis 116 of the motor spindle 40 is achieved. The longitudinal axis 116 coincides with the (ideal) longitudinal axis 162, although minimal residual deviations may exist.

[0096] The reference point 176 is now located 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 to Fig. 6, that with suitable selection and orientation of the adjusting disk 184, the motor spindle 40 or its spindle body 114 can be aligned such that the reference point 176 is now located close to the center. From the rather large tolerance circle 178 in Fig. 6. By mounting the adjusting disc 184, a significantly smaller (acceptable) tolerance circle 192 was achieved. Fig. 9. A significant improvement in positioning accuracy was achieved. Fig. 9 and Fig. For illustrative purposes, adjustment washers or parallel rings are not shown separately. Fig. Figure 9 further shows that the adjusting disk 184 was mounted in a specific rotational position (compare indicator 180), namely opposite to, or diametrically opposed to, the direction of reference point 176 (actual error). In this way, the adjusting disk 184 can counteract the error.

[0097] Additionally illustrated Fig. 8. A radial retaining element 190 for the motor spindle 40 or its spindle body 114 is provided by an element designated 190 on or in the spindle housing 38. The radial retaining element 190 stiffens the spindle in its nominal position and orientation. The radial retaining element 190 is preferably located a considerable distance from the table-side end of the motor spindle 40. In this area, the motor spindle 40 is already fixed to the spindle housing 38 by the mounting plate 142 and the adjusting washer 184.

[0098] Fig. Figure 10 illustrates a perspective, partially cutaway view of a spindle unit 66, which is designed as a double spindle (see also Fig. 2) The spindle unit 66 has a spindle housing 68, which provides mounts for two motor spindles 70, 72, each rotatable about its longitudinal axes 74, 76. One design objective for the alignment of the longitudinal axes 74, 76 is perpendicularity to a workpiece support or table. However, parallelism between the two longitudinal axes 74, 76 can also be a design objective. Furthermore, parallelism between each of the two longitudinal axes 74, 76 and the Z-direction – i.e., for example, a travel axis for the Z-direction – can also be a design objective.

[0099] The spindle 70 is also mounted on the spindle housing 68 via a mounting plate 142. Between the mounting plate 142, the spindle housing 68, and a contact surface of the spindle 70, an adjusting washer 128 and, optionally (at least in exemplary embodiments), a tuning ring 124 are arranged in the manner already described above. The other spindle 72 is mounted on the spindle housing 68 in a similar manner.

[0100] In addition, it is noted that Fig. 11 Reference is made to a simplified schematic frontal view of a spindle unit 66 with twin spindles (motor spindles 70, 72), see also Figure 11. Fig. 2 and Fig. 10. The spindles 70, 72 are mounted on a spindle housing 68. The spindle unit 66 is mounted on a Z-guide 196 via its spindle housing 68 so as to be movable.

[0101] Fig. Figure 11 illustrates adjustment options for the X and Y positions of the motor spindles 70 and 72. Motor spindle 70 has a swivel bearing 198. Motor spindle 72 has a swivel bearing 200. The swivel bearings 198 and 200 are each located in the circumferential area of ​​the motor spindles 70 and 72 and are fixedly mounted on the spindle housing 68. Furthermore, each motor spindle 70 and 72 is assigned an actuating element 202 or 204. Motor spindle 70 has an actuating element 202, which is located opposite the swivel bearing 198. Motor spindle 72 has an actuating element 204, which is located opposite the swivel bearing 200.

[0102] The arrangement of the swivel bearing 198 and the actuating 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, see double arrow 206. The arrangement of the swivel bearing 200 and the actuating 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, see double arrow 208.

[0103] The adjusting elements 202, 204 can be equipped with eccentrics arranged in corresponding guides (e.g., elongated holes) to trigger small adjustment movements during a rotary motion due to the eccentricity. After adjustment, the adjusting elements 202, 204 (or the spindle bodies of the motor spindles 70, 72) can be fixed to secure the actual position of the motor spindles 70, 72.

[0104] It is understood that an arrangement with a single motor spindle can also be similarly equipped with at least one actuating element to enable adjustment movements in at least the X-direction and / or the Y-direction. The alignment of two motor spindles 70, 72 is of great importance in spindle units 66 designed as a twin-spindle arrangement. This type of alignment can relate to a defined distance (in the X-direction) between the two motor spindles 70, 72. Furthermore, an objective of the alignment can be the positioning of both motor spindles 70, 72 in the same Y-position.

[0105] With reference to Fig. 12 uses a simplified schematic block diagram to illustrate and explain in more detail an embodiment of a method for aligning a motor spindle of a machine tool.

[0106] The method comprises a step S10, which involves pre-assembling or trial-fitting a motor spindle to a spindle housing designed to receive the motor spindle. For this purpose, the motor spindle is attached, at least temporarily, either directly or indirectly to a receiving surface of the spindle housing. The pre-assembly may include the insertion of spacers (parallel rings).

[0107] Step S12 follows, which involves detecting / determining any deviation of the motor spindle. Specifically, this involves determining any tilting of a longitudinal axis of the motor spindle relative to an ideal target position. The target position could be a desired perpendicularity to a table for holding workpieces. Furthermore, the target position could be a desired parallelism with respect to another longitudinal axis (such as another spindle). It could also be a desired parallelism with respect to a guide of the machine tool, such as a Z-axis guide. For example, a measuring mandrel or similar device could be attached to the motor spindle. The motor spindle is then moved relative to the measuring device along an axis, such as the Z-axis. The tilting of the spindle can be detected using suitable measuring instruments.The measuring point can be spaced away from the mounting of the measuring mandrel in the Z direction, so that any positional errors are more clearly perceptible.

[0108] It is conceivable to measure the deflections of the measuring mandrel in different spatial directions (X-direction, Y-direction). In this way, knowing the Z-position, a total deviation can be determined that describes a given vector of the longitudinal axis of the motor spindle (relative to the nominal position). Ideally, the determination of the actual deviation yields two easily manageable values ​​(for example, the deviation of a reference point in the X-direction and in the Y-direction).

[0109] The method comprises a further step S14, which involves providing a set of adjusting washers. The set comprises a plurality of adjusting washers. The adjusting washers have a wedge shape. Preferably, at least some of the adjusting washers in the set differ in their wedge thickness. By way of example, the wedge thickness of the adjusting washers can be in the range of 5 µm to 100 µm, based on an outer diameter of approximately 200 mm to 300 mm. The wedge thickness increment can be approximately 5 µm to 20 µm. It is understood that adjusting washers with different absolute dimensions are also possible, whereby corresponding wedge angles can be derived based on the above pairs of values, which are reflected in appropriately adjusted wedge thicknesses.

[0110] In other words, the wedge shape can have a wedge ratio (diameter to wedge thickness) that is approximately in the range of 2,000:1 to 100,000:1. Alternatively, the wedge shape can have a wedge ratio (diameter to wedge thickness) that is approximately in the range of 10,000:1 to 60,000:1. Alternatively, the wedge shape can have a wedge ratio (diameter to wedge thickness) that is approximately in the range of 20,000:1 to 30,000:1. Alternatively, the wedge shape can have a wedge ratio (diameter to wedge thickness) that is approximately 25,000:1. The wedge shape defined in this way corresponds to a wedge angle, which can also be specified via the ratio. By combining several adjusting shims, other ranges can be covered. The increment / gradation between the thicknesses of several adjusting shims can also be in similar ranges.

[0111] Step S16 follows, which involves selecting a suitable adjusting disc from the set of adjusting discs. Based on the actual deviation determined in step S12, the most suitable adjusting disc and its rotational position can be easily determined using an algorithm or a diagram / chart. The rotational position is important so that the wedge-shaped adjusting disc is positioned in a way that optimally counteracts the actual deviation.

[0112] After selecting the appropriate adjusting disc, it is mounted in a further step (S18) in the defined rotational position, either directly or indirectly, between the motor spindle and the spindle housing. This significantly reduces the actual deviation. For example, the adjusting disc can be coupled directly or indirectly to a contact surface of the motor spindle and a receiving surface of the spindle housing. The adjusting disc induces a deliberate error that partially compensates for the error that previously caused the actual deviation.

[0113] Step S18 is followed by step S20, which involves the final assembly of the motor spindle onto the spindle housing. This may include securing the motor spindle in the desired orientation to ensure it is firmly and permanently connected to the spindle housing. Step S20 may also include further adjustments or calibrations, such as aligning the motor spindle in directions perpendicular to the longitudinal axis (X-direction and / or Y-direction) and / or aligning the motor spindle along the longitudinal axis (Z-direction).

[0114] With reference to Fig. 13 uses a simplified schematic block diagram to illustrate and explain in more detail an embodiment of a method for aligning a machine tool with a twin-spindle arrangement.

[0115] The method comprises a first step S50, which includes providing a spindle assembly designed as a twin spindle. Accordingly, the spindle assembly has a spindle housing or spindle head in which mountings for two motor spindles are provided. Step S50 also includes providing two such motor spindles. These can be the same type of motor spindle. However, the motor spindles can also be of different designs. Identical motor spindles are typically used for parallel machining operations when the goal is to increase the machine tool's performance. Different motor spindles can be used, for example, when a machine tool is to be provided that enables different machining operations (e.g., with different speed levels for different tools).

[0116] In a further step S52, one of the two motor spindles is aligned. The alignment can include aligning the longitudinal axis of the motor spindle with respect to a table or a workpiece clamping / workpiece support. Preferably, the alignment uses at least some of steps S10 to S20 of the process described above. Fig. 12 illustrated procedures.

[0117] A further step, S54, follows, which includes aligning the second of the two motor spindles. The alignment can include aligning the longitudinal axis of the second motor spindle with respect to the longitudinal axis of the first motor spindle. Preferably, the alignment utilizes at least some of steps S10 to S20 of the process described above. Fig. 12 illustrated procedures.

Claims

[1] Method for aligning a tool spindle (42) designed as a spindle (40; 70, 72) of a machine tool (10), wherein relative movements can be generated between a workpiece holder (26; 88) for holding at least one workpiece and the spindle (40; 70, 72), the method comprising the following steps: - Trial assembly of the spindle (40; 70, 72) on a spindle housing (38; 68), comprising indirect or direct fastening of a contact surface (118) of the spindle (40; 70, 72) to a receiving surface (110) of the spindle housing (38; 68), - Determining the actual deviation of the spindle (40; 70, 72), - Selection of an adjusting disc (128; 164, 186, 188) depending on the determined actual deviation, wherein the adjusting disc (128; 164, 186, 188) is wedge-shaped, and - Arranging the adjusting disk (128; 164, 186, 188) between the contact surface (118) of the spindle (40; 70, 72) and the receiving surface (110) of the spindle housing (38; 68) in a rotational orientation that at least partially corrects the actual deviation. [2] The method of claim 1, further comprising the following steps: - Provision of a set (182) with a plurality of adjusting washers (128; 164, 186, 188) with different wedge thicknesses, - Selection of the adjusting disc (128; 164, 186, 188) for the correction whose wedge thickness corresponds at least approximately to the determined actual deviation. [3] Method according to claim 2, comprising providing a set (182) with at least three adjusting discs (128; 164, 186, 188) with different wedge thicknesses. [4] Method according to claim 3, wherein the wedge thicknesses of the adjusting discs (128; 164, 186, 188) of the set (182), based on an outer diameter of the adjusting discs (128; 164, 186, 188), are graduated from each other by a value of 5 µm to 20 µm. [5] Method according to any one of claims 2 to 4, wherein the wedge thickness of an adjusting disk (128; 164, 186, 188), based on an outer diameter of the adjusting disks (128; 164, 186, 188), is in a range between 5 µm and 100 µm compared to a plane-parallel disk (166). [6] Method according to any one of claims 1 to 5, wherein a plurality of defined rotational positions for the adjusting disk (128; 164, 186, 188) is provided between the contact surface (118) of the spindle (40; 70, 72) and the receiving surface (110) of the spindle housing (38; 68). [7] Method according to any one of claims 1 to 6, wherein the wedge disk is mounted such that the error attributable to the wedge shape of the adjusting disk (128; 164, 186, 188) is opposite to the actual deviation of the spindle (40; 70, 72). [8] Method according to any one of claims 1 to 7, wherein the determination of the actual deviation comprises a detection of a deviation of a reference point (176) in two spatial directions in a plane spaced apart from the mounting surface (118) of the spindle (40; 70, 72) and the receiving surface (110) of the spindle housing (38; 68), which is oriented perpendicular to the longitudinal axis (74, 76; 116) of the spindle (40; 70, 72). [9] Method according to any one of claims 1 to 7, wherein the determination of the actual deviation comprises recording an actual angular deviation and an actual rotational position of the actual angular deviation of the spindle (40; 70, 72). [10] Method according to any one of claims 1 to 9, wherein the spindle (40; 70, 72) is attached to the spindle housing (38; 68) via a mounting plate (142), wherein the mounting plate (142) is connected to the receiving surface (110) of the spindle housing (38; 68) and the contact surface (118) of the spindle (40; 70, 72). [11] Method for aligning a twin spindle (66) of a machine tool (10) comprising a first spindle (70) and a second spindle (72) arranged in a common spindle housing (38; 68), comprising the following steps: - Alignment of the first spindle (70) according to the method of one of claims 1 to 10, wherein the alignment is relative to the workpiece holder (26; 88) or a traversing axis (Z), and - Alignment of the second spindle (72) according to the method of one of claims 1 to 10, wherein the alignment is carried out relative to the first spindle (70) in order to achieve a desired parallelism between the two spindles (70, 72). [12] The method of claim 11, further comprising the following step: - Alignment of the first spindle (70) and the second spindle (72) in a plane perpendicular to the spindle axis (74, 76), wherein a first actuating element (202) is assigned to the first spindle (70) and the spindle housing (38; 68), wherein a second actuating element (204) is assigned to the second spindle (72) and the spindle housing (38; 68), wherein the first actuating element (202) is designed to displace the first spindle (70) relative to the spindle housing (38; 68) in a first direction, wherein the second actuating element (204) is designed to displace the second spindle (72) relative to the spindle housing (38; 68) in a second direction, and where the first direction and the second direction are oriented obliquely to each other. [13] Machine tool (10) comprising the following: - a rack (12), - a workpiece holder (26; 88) for holding at least one workpiece, and - a spindle housing (38; 68) which carries at least one tool spindle (42) designed as a spindle (40; 70, 72) for receiving at least one tool (44), which can be driven about its longitudinal axis (74, 76; 116), wherein relative movements can be generated between the workpiece holder (26; 88) and the at least one spindle (40; 70, 72), and wherein the spindle (40; 70, 72) is coupled via an adjusting disk (128; 164, 186, 188) to a receiving surface (110) of the spindle housing (38; 68), which is wedge-shaped and arranged in a rotational orientation between the contact surface (118) of the spindle (40; 70, 72) and the receiving surface (110) of the spindle housing (38; 68), so that a deviation of the spindle (40; 70, 72) from the workpiece holder (26; 88) is at least partially compensated. [14] Machine tool (10) according to claim 13, comprising a first spindle (70) and a second spindle (72) which are mounted on a common spindle housing (38; 68) and aligned parallel to each other, wherein at least the first spindle (70) or the second spindle (72) is coupled to a receiving surface (110) of the spindle housing (38; 68) via an adjusting disk (128; 164, 186, 188). [15] Use of a set (182) of adjusting discs (128; 164, 186, 188) for aligning a spindle (40; 70, 72) of a machine tool (10) according to the method of any one of claims 1 to 12.

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