MACHINE TOOL AND METHOD FOR THE ROLLING MACHINING OF ROTATIONAL PARTS WITH SLOT-SHAPED PROFILES

Description

TECHNICAL FIELD

[0001] The present invention relates to a machine tool specifically designed for generating groove-shaped profiles on rotating parts, and in particular for generating with gear-shaped tools. The term "generating" refers here to all processes in which the tool and workpiece roll against each other, including all processes occasionally referred to in the technical literature as "helical generating processes." The groove-shaped profiles can, in particular, form a toothing. The machine tool can, in particular, be designed to perform a power skiving process. The present invention also relates to a method for operating such a machine tool. STATE OF THE ART

[0002] In modern manufacturing technology, gear skiving is becoming increasingly important for machining rotary parts with groove-shaped profiles. Gear skiving has been known as a gear cutting process since at least 1910. An early description of the process can be found in DE 243514 C. Gear skiving is a continuous machining process for producing axisymmetric periodic structures using gear-shaped tools. The teeth of these tools have cutting edges on their end faces. The tool and workpiece are mounted on rotating spindles. The axes of rotation of the tool and workpiece are arranged skewed to each other. The typical rolling motion of the process is realized by coupling the rotational movements of the tool and workpiece around the axes of rotation.This rolling motion and a feed movement of the tool or workpiece along the workpiece axis create a cutting motion during gear skiving. This machining process can be used to machine both external and internal gears.

[0003] A skiving machine often has six driven, numerically controlled axes to generate the rotational movements of the workpiece and tool, as well as to position and align the workpiece and tool relative to each other. The designations of these axes vary depending on the convention used. The following convention is used in this document: Swivel axis for the relative alignment of the tool and workpiece spindles: A-axis: rotation axis of the skiving tool on the tool spindle: tool axis or B-axis; rotation axis of the workpiece on the workpiece spindle: workpiece axis or C-axis; and three linearly independent, but not necessarily perpendicular, linear displacement axes for the relative positioning of the tool spindle and the workpiece spindle: X-, Y- and Z-axis.

[0004] A wide variety of options for the design and arrangement of these axes are known from the state of the art. These options differ primarily in terms of the spatial orientation of the workpiece and tool axes. For example, the workpiece axis can have a fixed spatial orientation or be pivotable. If the workpiece axis has a fixed spatial orientation, it can be aligned horizontally or vertically in space. Depending on whether the workpiece axis is pivotable or not, the tool axis can have a fixed spatial orientation or be pivotable. If the tool axis has a fixed orientation, this axis can also be arranged vertically or horizontally. These different options for aligning the workpiece and tool axes lead, among other things, to different operating concepts for loading and unloading and to different requirements for chip removal.For each of these variants, there are a multitude of possibilities regarding the arrangement of the various axes relative to the machine bed and relative to each other and regarding the implementation of the axes.

[0005] An example of a gear skiving machine with horizontal arrangements of the workpiece and tool spindle is the GS300H machine from JTEKT Corporation, Nagoya, Japan (see brochure "Gear Skiving Centers / Machining Centers Line Up", catalog no. M2027-7E, printing note 170325U). On the tool carrier, the tool spindle is radially advanced using a vertical slide, and the entire tool carrier can be moved horizontally. The tool spindle is positioned horizontally in space and has a fixed orientation. The workpiece carrier with its horizontal slide realizes the axial advance. The workpiece spindle is also positioned horizontally in space and can be pivoted about a vertical pivot axis in a horizontal pivot plane.

[0006] A machine according to the preamble of claim 1 with a similarly constructed tool carrier is also known from US20150043985A1. However, in this machine, the workpiece spindle can be pivoted about a horizontal axis in a vertical pivot plane.

[0007] The vast majority of gear skiving machines, however, feature a vertically aligned workpiece axis and a pivoting tool axis. For example, on the LK 300 and LK 500 gear skiving machines from Liebherr Verzahntechnik GmbH, Kempten, Germany, the workpiece spindle is vertically aligned and fixed to the machine bed, while the tool spindle is positioned above the workpiece spindle and can be moved relative to the machine bed along all three linear axes X, Y, and Z and pivoted about an A-axis (see brochure "Gear Skiving Machines LK 300 / 500", Liebherr-Verzahntechnik GmbH, printing note BK LVT-LK300 / 500-1.0.-07.18_en).

[0008] The 400PS machine from Gleason Corporation, Rochester, USA, also has a vertically aligned workpiece spindle, fixed to the machine bed. A similar arrangement is also known from US2017072485A1, Fig. 11. The MSS300 machine from Mitsubishi Heavy Industries Machine Tool Co., Ltd., Shiga, Japan, also has a fixed, vertical workpiece spindle. A similar arrangement is also known from US2019076943A1, Fig. 1 known.

[0009] On the S-250 machine from Profilator GmbH & Co. KG, Wuppertal, Germany, the tool spindle is mounted on a carriage that can pivot around the A-axis. This carriage, in turn, can be moved relative to the machine bed along a linear displacement axis that is inclined to the machine bed. The workpiece spindle can be moved above the tool spindle along two linear displacement axes. On the S-500 machine from Profilator GmbH & Co. KG, the workpiece spindle can also be moved above the tool spindle along two linear displacement axes (see presentation materials by Dr. Claus Kobialka, "State of the Art in Skiving (SCUDDING)," GETPRO Congress, March 25 / 26, 2015, Würzburg, Germany).

[0010] A pivoting tool spindle is also featured on the "SynchroSkiver" machine from Präwema Antriebstechnik GmbH, Eschwege, Germany. Here, too, the workpiece spindle can be moved along two axes above the tool spindle (see "SynchroSkiver" brochure, Präwema Antriebstechnik GmbH, printing reference PRW-2015-09-V1-HDM).

[0011] The KPS20 machine from Kashifuji KK also features a pivoting tool spindle, above which the workpiece spindle can be moved along two axes. An arrangement with a pivoting tool spindle located below and a movable workpiece spindle above is also known from JP2014151382A2. Fig. 1 known.

[0012] Another concept with a pivoting tool spindle arranged below and a crosswise movable workpiece spindle arranged above is also known from US2012328384A1 (Fig. 18).

[0013] On the GMS450 machine from Nachi-Fujikoshi Corp., Toyama, Japan, the workpiece spindle is vertically aligned and can be moved horizontally in one direction relative to the machine bed. On a machine stand that is firmly connected to the machine bed, a carriage is mounted above the workpiece spindle, vertically movable horizontally. A vertically movable carriage is attached to this carriage. The tool spindle is mounted on this carriage so that it can pivot about an A-axis. The A-axis runs parallel to the axis along which the workpiece spindle can be moved on the machine bed. Reference is made to the document "GMS450" from Nachi-Fujikoshi Corp., Catalog No. M6202E, Printing Notice 2016.9.X.MD-SANWA.

[0014] The PV315 machine from Pittler T & S GmbH, Dietzenbach, Germany, also features a vertically aligned workpiece spindle that can be moved in one direction relative to the machine bed. A machine column on the machine bed can also be moved horizontally in a direction perpendicular to the spindle. The machine column supports a vertically movable carriage on which the tool spindle is pivotably mounted in a pivoting plane parallel to the horizontal displacement direction. Reference is made to the document "Power Skiving in Complete Machining" from PITTLER T&S GmbH, printing note PIT-2017.04-DE-HDM.

[0015] EP 1 338 376 A1 discloses a milling and drilling machine for milling and turning bar stock into individual workpieces. It comprises a vertical spindle head mounted on a column, which is motor-driven and movable along a first coordinate axis. The spindle head is designed to selectively accommodate milling tools and turning tools. It also comprises a clamping device arranged laterally next to the work area, which comprises a workpiece clamp with a clamping axis extending along a horizontal coordinate axis and a rotary drive for the workpiece clamp. The spindle head is pivotable about an axis extending in the Y direction on the front side of a headstock movable along the Y coordinate axis.The headstock is arranged on a carriage which is motor-driven and movable in an X-coordinate axis parallel to the workpiece clamping axis on the stationary column, and the clamping device is arranged on an inclined console arranged on the front side of the column and which is motor-driven and movable in guides in the Z-coordinate axis.

[0016] DE 202 04 365 U1 discloses a spindle head for a universal milling machine with a housing rotatably mounted on a machine part and a directly driven work spindle arranged axially parallel within the housing. A second spindle unit adjustable around two axes is arranged at the rear of the housing.

[0017] Due to the special kinematics of power skiving, strongly fluctuating machining forces arise along the cutting edge contact. This applies particularly to the hard fine machining of pre-toothed workpieces. In particular, high and strongly fluctuating axial forces arise along the tool and workpiece axes; on the other hand, high and strongly fluctuating radial forces also arise, which lead to large bending moments on the tool and workpiece. Overall, these process characteristics have a negative impact on the achievable manufacturing accuracies, especially when the respective NC axes are moved during machining due to the process. Key factors for achieving high manufacturing accuracy are, in particular, static and dynamic rigidity, the damping properties of the machine, and high thermal symmetry. However, these requirements are not yet optimally met by existing arrangements. PRESENTATION OF THE INVENTION

[0018] It is an object of the present invention to provide a machine tool which is suitable for the generating machining, in particular the skiving, of rotary parts with groove-shaped profiles, in particular gear teeth, and in particular for their hard fine machining and which has improved static and dynamic rigidity with high thermal stability.

[0019] This object is achieved by a machine tool having the features of claim 1. Further embodiments are specified in the dependent claims.

[0020] A machine tool is therefore specified for the rolling machining of rotating parts with groove-shaped profiles. This machine tool features: a machine bed; a Y-carriage that is linearly displaceable along a Y-direction relative to the machine bed; a workpiece spindle that is arranged on the Y-carriage and that is designed to clamp a workpiece thereon and to drive it for rotation about a workpiece axis (C-axis), wherein the workpiece axis runs transversely, preferably perpendicularly, to the first direction; a Z-carriage that is arranged on the machine bed and is linearly displaceable along a Z-direction relative to the machine bed, wherein the Z-direction runs parallel to a center plane spanned by the Y-direction and the workpiece axis, and wherein the Z-direction runs at an angle of less than 45°, preferably parallel, to the workpiece axis; an X-carriage that is arranged on the Z-carriage and is linearly displaceable along an X-direction relative to the Z-carriage, wherein the X-direction runs perpendicular to the center plane;a tool spindle designed to clamp a rolling machining tool, in particular a gear-shaped rolling machining tool, and to drive it to rotate about a tool axis (B-axis), wherein the tool spindle is arranged on the X-slide and is pivotable relative to the X-slide about a first pivot axis (A-axis), and a controller designed to establish a positive coupling between the rotation of the rolling machining tool and the rotation of the workpiece.

[0021] In this document, an arrangement of two axes "transverse" to each other is understood to mean an arrangement in which the two axes run at an angle of more than 45° and less than 135° to each other, in particular at an angle of more than 60° and less than 120°.

[0022] Since the entire X-slide, including the tool spindle and its swivel mechanism, is mounted on the Z-slide, the inertial mass on the Z-slide is relatively large. This is particularly advantageous because machining forces acting along the main cutting direction are primarily applied in the Z-direction, and therefore particularly large and highly fluctuating machining forces and tilting loads occur along this direction. The large inertial mass on the Z-slide achieves particularly advantageous dynamic behavior along the particularly heavily stressed Z-direction. The design with a central center plane, along which the axes are aligned, also enables a particularly rigid and thermally stable construction.The relatively light, low-mass Y-slide, which is guided independently on the machine bed, ultimately enables the workpiece spindle to be moved quickly and precisely along the Y-axis between a workpiece change position and a machining position.

[0023] In advantageous embodiments, the first pivot axis (A-axis), about which the tool spindle can be pivoted relative to the X-carriage, runs perpendicular to the center plane, and the tool axis runs perpendicular to the first pivot axis. In this case, the pivoting movement of the tool axis occurs in a pivot plane that runs parallel to the center plane and thus reflects the symmetry of the rest of the machine structure. Preferably, the tool axis also intersects the first pivot axis, so that torques about the A-axis are minimized.

[0024] This arrangement of the pivot plane parallel to the center plane is particularly advantageous for generating processes in which gear-shaped tools are used, such as gear skiving or gear shaving. However, an arrangement of the first pivot axis (A-axis) parallel to the center plane and in particular perpendicular to the X and Z axes is also conceivable, in which case the tool axis also advantageously runs perpendicular to the first pivot axis (A-axis) and in particular intersects the first pivot axis. Such an arrangement can be particularly advantageous for generating processes with worm-shaped tools, such as generating grinding or hobbing.

[0025] In advantageous embodiments, the tool spindle is pivotably mounted on the X-slide as follows: The machine tool has two first pivot bearings for supporting the tool spindle on the X-slide about the first pivot axis. These two first pivot bearings are arranged on either side of the tool spindle with respect to the pivot plane and are preferably equidistant from the pivot plane.

[0026] The machine tool can have an adjustment mechanism for adjusting the orientation of the tool spindle relative to the X-carriage. This adjustment mechanism can be pivotally connected to the X-carriage about a second pivot axis, wherein the second pivot axis runs parallel to and at a distance from the first pivot axis. It can also be pivotally connected to the tool spindle about a third pivot axis, wherein the third pivot axis runs parallel to and at a distance from the first pivot axis and the second pivot axis. In this case, there are therefore a total of three pivot axes via which the X-carriage, the tool spindle, and the adjustment mechanism are connected to one another.

[0027] The adjustment mechanism can also advantageously be mounted on both sides of the pivot plane. For this purpose, the machine tool can comprise two second pivot bearings for supporting the adjustment mechanism on the X-carriage about the second pivot axis, wherein the two second pivot bearings are arranged on both sides and preferably equidistant from the pivot plane, and / or it can comprise two third pivot bearings for supporting the adjustment mechanism on the tool spindle about the third pivot axis, wherein the two third pivot bearings are also arranged on both sides and preferably equidistant from the pivot plane.

[0028] The adjustment mechanism can be constructed, in particular, as follows: It can comprise an A-drive motor that can be pivoted relative to the X-slide and drives a threaded spindle to rotate about a threaded spindle axis running perpendicular to the first pivot axis, wherein the threaded spindle axis runs in the pivot plane. It can also comprise a spindle nut that can be pivoted relative to the X-slide and engages the threaded spindle. The threaded spindle and the spindle nut can be designed, in particular, as a ball screw drive. Due to its high transmission ratio, such a mechanism enables particularly safe, rigid, precise, and smooth adjustment of the orientation of the tool spindle about the first pivot axis (A-axis). The adjustment can even take place during machining of a workpiece; clamping for stationary operation can be omitted.

[0029] Preferably, the A-drive motor is mounted on the X-carriage so that it can pivot about the second pivot axis, and the spindle nut is preferably connected to the tool spindle so that it can pivot about the third pivot axis. However, a reverse arrangement is also conceivable, in which the A-drive motor is connected to the tool spindle so that it can pivot about the third pivot axis, and the spindle nut is connected to the X-carriage so that it can pivot about the second pivot axis.

[0030] In order to precisely determine the swivel position of the workpiece spindle, the machine tool can have: a first angle measuring device configured to determine a rotation angle of the A drive motor or the threaded spindle about the threaded spindle axis; and / or at least one second angle measuring device configured to directly determine a pivot angle of the tool spindle about the A axis relative to the X-slide.

[0031] A particularly advantageous arrangement of the adjustment mechanism is as follows: The tool spindle has a tool-side end and a tool-remote (drive-side) end. A generating tool is clamped on the tool spindle at the tool-side end, defining a tool reference plane perpendicular to the tool axis. In the case of a gear skiving tool, the tool reference plane can, in particular, be a plane that runs through the cutting edges of the tool on the distal end face of the tool ("cutting edge plane"). In the case of other types of generating tools (e.g., gear hobbing tools or gear grinding tools), any effective plane that runs perpendicular to the tool axis and in which the tool interacts with the workpiece during machining can generally be used as the tool reference plane.There can be a whole family of such planes on the tool, but the area along the tool axis in which these planes intersect the tool axis is usually small compared to the length of the entire tool spindle, so that the specific position of the tool reference plane is not important for the following considerations. For example, a plane through the center of the tool area intended for machining along the B axis can be assumed to be the tool reference plane. The first swivel axis (A axis) intersects the tool axis (B axis) between the end of the tool spindle facing away from the tool. The connection between the tool spindle and the adjustment mechanism is made in the area of ​​the end of the tool spindle facing away from the tool, i.e. the third swivel axis runs in the area of ​​this end facing away from the tool.The first pivot axis (A-axis) and the tool reference plane are spaced apart at a first distance, and the A-axis and the third pivot axis are spaced apart at a second distance. It is advantageous if the second distance and the first distance are in a ratio greater than 1, preferably in a ratio of 1.5 to 3.

[0032] In this arrangement, the A-axis intersects the tool axis near the tool-side spindle end. This results in very short lever arms for the forces acting on the tool in the X, Y, and Z directions, which can have a pulsating characteristic due to the process. These forces therefore act on the machine structure with relatively low bending moments and thus generate relatively low vibration energy that can act on the tool carrier. The large mass of the entire tool carrier also ensures effective broadband damping. Furthermore, the movement of the tool in the Y and Z directions caused by the pivoting movement around the A-axis is small due to the minimized distance between the tool reference plane and the pivot axis.

[0033] To adjust the orientation of the tool spindle around the A-axis, other adjustment mechanisms can be used instead of the adjustment mechanism with a screw drive discussed above, in particular a direct drive with a torque motor. While this is advantageous in terms of simple construction, it is located in the machining area and takes up a lot of space. This results in additional collision restrictions between the tool and workpiece. In addition, the large space requirement of a direct drive can mean that, on the one hand, the X-carriage must be made wider, ultimately making the machine wider overall, and, on the other hand, that the A-axis must be located a greater distance from the X and Z guides, so that the forces on the tool described above act on the machine structure via larger lever arms, with correspondingly negative consequences for the tendency to vibration.The screw drive design discussed above avoids these disadvantages.

[0034] In order to additionally dampen vibrations of the tool spindle about the A-axis, the machine tool can have at least one vibration damper, preferably two vibration dampers arranged on both sides and preferably equidistant from the pivoting plane, wherein the vibration damper(s) act between the tool spindle and the X-slide.

[0035] The swivel range of the tool spindle about the first swivel axis (A-axis) is preferably asymmetrical, i.e. the tool spindle can preferably be swiveled about the A-axis relative to the X-slide in such a way that an axis crossing angle between the tool axis (B-axis) and the workpiece axis (C-axis) takes on either negative or positive values, whereby the maximum positive value of the axis crossing angle is greater than the absolute value of the smallest negative value. The absolute value of the smallest negative value is preferably not greater than 10°, while the maximum positive value is preferably at least 30°. The axis crossing angle is defined as positive when the tool is inclined towards the X-slide and as negative when the tool is inclined away from the X-slide. Due to the asymmetric swivel range, less space is required, and the workpiece spindle orThe A-axis can therefore be positioned closer to the linear guides of the Z- and X-slides in order to keep the effective lever arm with regard to torsions around these linear guides low. In addition, with a positive axis crossing angle, the tool center is positioned even closer to the linear guides of the Z- and X-slides than the A-axis, which has an additional positive effect on machining precision. Due to the symmetrical design of the machine with regard to the center plane, an asymmetrical swivel range does not represent a restriction for generating machining. Depending on the direction of the helix angle of the gear to be machined, the tool can be brought into engagement with the gear to be machined by moving the X-slide either to the left or right of the center plane during generating machining. The symmetry of the arrangement of the linear axes with regard to the swivel plane remains unaffected by the asymmetrical swivel range.

[0036] In some embodiments, the workpiece axis (C-axis) runs vertically in space. This enables easy workpiece changing and efficient chip removal. Furthermore, with a vertical arrangement of the C-axis, the Z-axis preferably also runs vertically in space. In such an arrangement, the weight of the Z-carriage, together with the X-carriage mounted on it and the tool spindle, acts along the Z-direction, thus further reducing the tendency to vibration along the Z-direction. However, it is also possible for the C-axis to run along a different spatial direction, particularly horizontally.

[0037] The machine tool preferably has two mutually parallel Z-linear guides, which extend parallel to the Z-direction, arranged on both sides and preferably equidistant from the aforementioned center plane, and on which the Z-slide is guided along the Z-direction relative to the machine bed. Each of the linear guides can then be assigned a separate Z-drive to move the Z-slide along the Z-direction relative to the machine bed. Each of these Z-drives can, in particular, comprise a drive motor, a threaded spindle, and an associated spindle nut. The threaded spindle and spindle nut are preferably designed as a ball screw drive. Such a double Z-drive contributes to high dynamic rigidity and maintains the symmetry of the machine tool's structure with respect to the center plane.

[0038] To precisely determine the Z position of the workpiece spindle, the machine tool can comprise one, preferably two, Z-linear measuring systems, each of which has a measuring head mounted on the Z-carriage and a linear scale mounted on the machine bed. The measuring head of each of the Z-linear measuring systems is then preferably arranged such that it performs a position measurement in an A-reference plane that runs perpendicular to the Z direction and contains the A-axis. This allows the measurement to be performed at a defined location that is highly suitable for characterizing the position of the workpiece spindle.

[0039] To guide the X-slide along the Z-slide, the machine tool preferably has two parallel X-linear guides that extend parallel to the X-direction and on which the X-slide is guided along the X-direction relative to the Z-slide. A single X-drive can be provided for the X-axis, which can in particular comprise a drive motor, a threaded spindle, and an associated spindle nut. The threaded spindle and spindle nut are preferably designed as a ball screw drive. However, a dual drive, as described above for the Z-direction, is also conceivable here.

[0040] The Y-slide can be guided on the machine bed in a very similar way to the Z-slide. In particular, the machine tool can have two parallel Y-linear guides that extend parallel to the Y-direction, are arranged on both sides, preferably equidistant from the central plane, and on which the Y-slide is guided along the Y-direction relative to the machine bed. The machine tool can in turn have two Y-drives to move the Y-slide along the Y-direction relative to the machine bed, with one of the Y-drives being assigned to one of the Y-linear guides. Each of the Y-drives can comprise a drive motor, a threaded spindle, and an associated spindle nut. The threaded spindle and spindle nut are preferably again designed as a ball screw drive.

[0041] Similar to the Z-axis, the machine tool can comprise one, preferably two, Y-linear measuring systems, each of which has a measuring head mounted on the Y-carriage and a linear scale mounted on the machine bed. Each of the measuring heads of the Y-linear measuring systems is preferably arranged such that it performs a position measurement in a C-reference plane that runs perpendicular to the Y-direction and contains the workpiece axis (C-axis). This allows the measurement to be performed at a location that particularly accurately characterizes the position of the workpiece center relative to the Y-direction.

[0042] Due to the paired drives in the Y and Z axes, the rigidity is improved both against axial movements along the respective direction and against tilting movements around the Y or Z direction.

[0043] The machine tool may have at least one of the following additional components: a centering device for determining the position of tooth gaps on the workpiece; an optical measuring bridge for measuring the tool and / or the workpiece; and a tool changing device for changing the tool.

[0044] For each of the additional components, two alternative fastening structures can be provided, arranged on either side of the central center plane. In particular, two alternative fastening structures for the centering probe can be formed on either side of the central center plane on the X-carriage. Two alternative fastening structures for the measuring bridge can be formed on either side of the central center plane on the Y-carriage. Two alternative fastening structures for the tool changing device can be formed on either side of the central center plane on the machine bed. In this way, depending on the customer's requirements, a workpiece loader can be arranged in one of several possible locations, and the additional components can then be fastened to the machine in such a way that they do not collide with the workpiece loader. In the simplest case, each of the fastening structures can, for example, comprise a fastening surface in which suitable holes are drilled.In more complex designs, however, a fastening structure can also comprise a three-dimensional structure that is specifically designed for the attachment of the respective additional component.

[0045] The machine tool can have a chip conveyor arranged in the central plane beneath the machine bed. The machine bed can have a central recess to allow chips from a chip-cutting zone to be discharged onto the chip conveyor. The chip conveyor can preferably be arranged to convey chips from a front machining area of ​​the machine to a rear area of ​​the machine. Alternatively, conveying the chips forward is also conceivable.

[0046] The machine tool is designed for the rolling machining of rotating parts with groove-shaped profiles, in particular gears.

[0047] For this purpose, the machine tool has a control system designed to establish a positive coupling between the rotation of the generating tool and the rotation of the workpiece. The machine can be used for soft machining, but preferably for hard finishing of pre-toothed workpieces. The machine tool is particularly suitable for gear skiving, but can also be used for other gear machining processes, in particular gear shaving, gear honing, gear grinding, or gear hobbing.

[0048] A method for machining a workpiece with a machine tool of the aforementioned type comprises: Bringing a rolling machining tool clamped on the tool spindle into engagement with the workpiece while the workpiece is clamped on the workpiece spindle, wherein the engagement preferably occurs in a relative arrangement of the rolling machining tool to the workpiece in which the tool axis is offset from the central center plane of the machine tool; and performing a rolling machining operation on the workpiece with the machine tool. The rolling machining tool can, in particular, be a gear-shaped rolling machining tool, e.g., a skiving tool. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Preferred embodiments of the invention are described below with reference to the drawings, which are for illustrative purposes only and are not to be construed as limiting. In the drawings: Fig. 1 a perspective view of a machine tool according to a first embodiment; Fig. 2 an enlarged detailed view in the area A1 of the Fig. 1 ; Fig. 3 a sectional view of the machine tool in Fig. 1 in the central plane E1; Fig. 4 an enlarged detailed view in area A2 of the Fig. 3 ; Fig. 5a perspective view of the machine tool in Fig. 1 , , omitting parts in the area of ​​the X-slide; and Fig. 6 shows a perspective view of a machine tool according to a second embodiment. DESCRIPTION OF PREFERRED EMBODIMENTS First embodiment: Vertical workpiece axis

[0050] The Figures 1 to 4 show various views of a machine tool according to a first embodiment. In the Figure 5 For the sake of clarity, parts of the machine were not shown, in particular the front part of the Z-slide and the entire X-slide with the tool spindle mounted on it.

[0051] The machine tool shown is particularly well-suited for the power skiving process. However, it is also possible to perform other machining operations with such a machine, particularly other gear skiving processes.

[0052] The machine has a machine bed 100. How best to Fig. 3 As can be seen, the machine bed 100 is approximately L-shaped in side view, with a horizontal section 110 and a vertical section 120. The vertical section of the machine bed 120 separates a front machining area 130 from a rear area 140 of the machine.

[0053] A Y-slide 200 is arranged on the horizontal section 110 of the machine bed 100. This Y-slide is displaceable along a Y-direction relative to the machine bed 100. The Y-direction runs horizontally in space. The Y-slide 200 carries a workpiece spindle 210, on which a pre-toothed workpiece 220 is clamped. In this respect, the Y-slide 200 serves as a workpiece carrier. The workpiece 220 is driven on the workpiece spindle 210 for rotation about a workpiece axis (C-axis). The C-axis runs vertically in space, i.e., along the direction of gravity. The C-axis and the Y-direction together define a central center plane E1 of the machine. The center plane E1 contains the C-axis, regardless of the position of the Y-slide 200 along the Y-direction.

[0054] A Z-slide 300 is arranged on the vertical section 120 of the machine bed 100. This slide is displaceable along a Z-direction relative to the machine bed 100. The Z-direction runs parallel to the center plane E1. In the present example, the Z-direction runs vertically in space, parallel to the C-axis and perpendicular to the Y-direction. An X-slide 310 is arranged on the Z-slide 300, which carries a tool spindle 320 and thus forms a tool carrier. The X-slide 310 is displaceable along an X-direction relative to the Z-slide 300. The X-direction runs horizontally in space, perpendicular to the Z-direction and the Y-direction, and thus perpendicular to the center plane E1. Together, the Z-slide 300 and the X-slide 310 form a cross-slide that enables displacement of the tool spindle 320 mounted thereon along the mutually perpendicular Z and X directions.

[0055] The tool spindle 320 drives a rolling machining tool clamped on it, here a skiving tool 330 ("skiving wheel", see Fig. 3 and 4 ), to a rotation around a tool axis (B-axis, see Fig. 4 ). The tool spindle 320 is pivotable relative to the X-slide 310 about a first pivot axis (A-axis, see Fig. 2 ) pivotable. The A-axis runs perpendicular to the B-axis and perpendicular to the center plane E1. The A-axis intersects the B-axis. The plane in which the B-axis pivots is called the pivot plane E2. This pivot plane E2 runs perpendicular to the A-axis (i.e., it is a normal plane to the A-axis) and contains the B-axis, regardless of its pivot position around the A-axis. It runs parallel to the center plane E1.

[0056] A chip conveyor 500 is arranged below and behind the machine bed 100 in such a way that it conveys chips from an area below the Y-carriage 200 to the rear area 140 of the machine. For this purpose, the chip conveyor 500 has a drive 510. A recess for discharging the accumulating chips is arranged in the machine bed 100 below the Y-carriage 200. Alternatively, the chip conveyor 500 can be arranged so that it conveys the chips forward instead of to the rear area.

[0057] A machine control system with control panel 600 is used to control and operate the machine. Setting the orientation of the tool spindle around the A-axis

[0058] For generating machining processes, it is important that the orientation of the tool spindle 320 around the A-axis can be precisely adjusted. The machine is equipped with a corresponding adjustment mechanism for this purpose.

[0059] In the Figures 2 and 4The pivotally mounted tool spindle 320 and the adjustment mechanism for adjusting the orientation of the tool spindle 320 around the A-axis are particularly clearly visible. The X-slide 310 has a side wall ("cheek") 313 on each side of the pivot plane E2, which extends forward parallel to the pivot plane E2 and opposite to the Y-direction. A sufficiently large recess for the tool spindle 320 is provided between the two cheeks 313. The tool spindle 320 is arranged between the cheeks 313 in the pivot plane E2 and is mounted in the corresponding cheek 313 via a pivot bearing 314 in the form of a play-free roller bearing. The two pivot bearings 314 enable a pivoting movement of the tool spindle 320 relative to the X-slide 310 around the first pivot axis (A-axis).

[0060] In an upper end area of ​​the X-slide 310, an A-drive motor 340 is arranged centrally between the cheeks 313. This motor is mounted on the X-slide 310 on both sides of the pivot plane E2 in two backlash-free roller bearings 315, pivotable about a second pivot axis A'. The second pivot axis A' runs parallel to the A-axis. The A-drive motor 340 drives a threaded spindle 342 to rotate about a threaded spindle axis 343. The threaded spindle 342 cooperates with a spindle nut 344. The threaded spindle 342 and the spindle nut 344 are designed as a backlash-free ball screw drive.

[0061] The spindle nut 344 is connected on both sides of the pivot plane E2 to an upper end region of the tool spindle 320. The spindle nut 344 can be pivoted about a third pivot axis A" relative to the tool spindle 320 via two play-free roller bearings 325. The third pivot axis A" again runs parallel to the A-axis.

[0062] By actuating the A drive motor 340, the threaded spindle 342 is driven to rotate about the threaded spindle axis 343. This changes the position of the spindle nut 344 along the threaded spindle axis 343. This causes the tool spindle 320 to pivot about the A axis. Due to the large transmission ratio, a relatively small motor torque of the A drive motor 340 is converted into a relatively large displacement force or a relatively large pivoting torque of the tool spindle 320. Overall, the pivoting movement of the tool spindle 320 can thus be carried out very smoothly and precisely. Even during machining, the orientation of the tool spindle 320 can be changed. Clamping for stationary operation can be omitted.

[0063] The prevailing geometric conditions are determined by the Fig. 4 explained in more detail. The A-axis (see Fig. 2) intersects the B-axis in an area lying between the tool-side end and the tool-remote end of the tool spindle 320. The tool 330 has a plurality of cutting edges at its free end, which together define a cutting plane 331. This cutting plane 331 represents a reference plane on the tool. The cutting plane 331 runs perpendicular to the B-axis. The distance of the cutting plane 331 from the A-axis defines a lever arm H. The distance between the A-axis and the third pivot axis A", about which the spindle nut 344 can pivot, defines a pivot radius R.

[0064] The radial cutting forces acting between the workpiece and the tool during workpiece machining result in corresponding torques about the A-axis. The torque about the A-axis for a given radial cutting force in the swivel plane E2 is proportional to the length of the lever arm H. This torque, in turn, results in a corresponding axial force on the spindle nut 344 along the spindle axis 343. This force is smaller the larger the swivel radius R. In this case, the swivel radius R is significantly larger than the lever arm H. Preferably, the ratio R / H is greater than 1 and is in particular between 1.5 and 3. The A-drive motor 340 therefore only needs to absorb correspondingly reduced forces. This is advantageous for the rigidity of the machine with regard to vibrations about the A-axis.

[0065] To dampen vibrations around the A-axis, two additional vibration dampers 346 are arranged between the tool spindle 320 and the X-slide 310. These run on both sides of the pivot plane E2 between the upper end area of ​​the tool spindle 320 and the upper end area of ​​the X-slide 310, adjacent to the threaded spindle 342.

[0066] For precise machining of the workpiece in a generating process such as the skiving process, precise knowledge of the orientation of the tool spindle 320 around the A-axis, ie the angle α between the B-axis and the C-axis (see Fig. 4 ), important. The angle αis also referred to in this document as the axis intersection angle. To determine this angle precisely, the machine preferably has two independent angle measuring devices. One of the angle measuring devices measures the angle of rotation of the threaded spindle 342; from this, the position of the spindle nut 344 along the threaded spindle 342 and thus the swivel angle of the tool spindle 320 can be determined indirectly. This first angle measuring device is integrated in the A drive motor 340 and in the Figure 2 indicated by the reference number 347. At least one further angle measuring device directly measures the swivel angle of the tool spindle 320 around the A-axis and thus the axis crossing angle α This additional angle measuring device is integrated in one of the two pivot bearings 314 and is indicated by the reference numeral 323 (see Fig. 2 ).

[0067] As in the Fig. 4 As illustrated, the axis cross angle αcan take both positive and negative values. The axis crossing angle α defined as positive when the tool 330 is tilted towards the X-slide 310, and as negative when the tool 330 is tilted away from the X-slide 310. The swivel range of the tool spindle 320 is asymmetrical: The axis cross angle α can assume significantly larger positive than negative values. Specifically, the swivel range can extend from -5° to +35°, for example, but other swivel ranges are also possible. Due to the machine's virtually mirror-symmetrical design with respect to the center plane E1, this does not limit generating machining to a single helix direction of the gear to be machined. Depending on the helix direction, tool 330 can be brought into engagement with the gear to be machined either to the left or right of the center plane E1 during generating machining. Positioning of the tool carrier in Z and X directions

[0068] As already explained, the machine is designed so that the position of the tool spindle 320 can be adjusted both along the Z direction and along the X direction. The axial feed is achieved with the Z infeed, and the radial feed during generating machining is achieved with the X infeed or a combination of X and Y infeed. Since machining forces fluctuate particularly strongly along the Z direction, adjustment along the Z direction is achieved with a Z slide 300, which is guided directly on the machine bed 100; the X slide 310 is mounted on this Z slide as a tool carrier. As a result, a significantly larger inertial mass must be moved along the Z direction than along the X direction. This helps to keep the amplitude of vibrations along the Z direction, which could be excited by the fluctuating machining forces, small.

[0069] To guide the Z-slide 300 relative to the machine bed 100, two parallel Z-linear guides 301 are provided on the vertical section 120 of the machine bed. These guides extend parallel to the Z-direction and are arranged symmetrically on both sides to the center plane E1. The Z-slide 300 is guided on these linear guides 301 along the Z-direction relative to the machine bed 100. Each of the linear guides 301 is assigned a Z-drive motor 302. Each of these Z-drive motors 302 interacts with the Z-slide 300 via a backlash-free ball screw drive 303 to drive the Z-slide 300 along the Z-direction (see Fig. 5The Z linear guides 301, Z drive motors 302, and ball screws 303 are constructed in pairs with almost identical dimensions and are arranged symmetrically with respect to the central plane E1. The two Z drive motors are either separately position-controlled ("Double Drive") or work together in master-slave mode.

[0070] To dampen vibrations along the Z-direction, each Z-linear guide 301 is optionally assigned a vibration damper (not shown in the drawing). This vibration damper can be designed, in particular, according to Swiss patent application 1023 / 18 dated August 24, 2018. The vibration dampers are also identical in pairs and arranged symmetrically.

[0071] Each of the two Z-linear guides 301 is also assigned a Z-linear measuring system 350 in order to determine the position of the Z-slide 300 on the machine bed 100 as precisely as possible (see Fig. 3). The two Z-linear measuring systems 350 are also identically constructed and arranged symmetrically with respect to the center plane E1. Each of these Z-linear measuring systems has a measuring head 351 which is attached to an outer surface of the Z-carriage 300. In addition, each Z-linear measuring system has a linear scale 352 attached to the machine bed 100. The measuring head 351 is mounted in such a way that it carries out a position measurement in a plane E4 which runs perpendicular to the Z-direction (i.e. is a normal plane to the Z-direction) and contains the A-axis. This plane E4 is particularly well suited for characterizing the position of the A-axis relative to the machine bed 100 with respect to the Z-direction and is therefore also referred to as the A-reference plane.

[0072] To guide the X-carriage 310 on the Z-carriage 300, two parallel X-linear guides 311 are provided on the Z-carriage 300. These guides extend parallel to the X-direction and guide the X-carriage 310 along the X-direction relative to the Z-carriage. An X-drive motor 312 is used to adjust the position of the X-carriage 310 along the X-direction. Positioning of the workpiece carrier in the Y direction

[0073] The guidance and adjustment of the Y-slide 200 (i.e., the workpiece carrier) relative to the machine bed 100 along the Y-direction is very similar to the guidance and adjustment of the Z-slide 300 along the Z-direction. On the horizontal section of the machine bed 100, two parallel Y-linear guides 201 are arranged symmetrically to the central plane E1. The Y-slide 200 runs on these linear guides 201. To drive the Y-slide 200, each of the two linear guides 201 is assigned a Y-drive motor 202 (see Fig. 3Each of the Y-drive motors 202 interacts with the Y-carriage 200 via a backlash-free ball screw drive 203. The Y-drive motors 202 can be separately position-controlled or operated in master-slave mode. To dampen vibrations along the Y-direction, each linear guide 201 can optionally be assigned a vibration damper (not shown in the drawing), which can be designed according to Swiss patent application 1023 / 18 of August 24, 2018.

[0074] Each of the two linear guides 201 is also assigned a Y-linear measuring system 230. Each of these Y-linear measuring systems has a measuring head 231 mounted on the outside of the Y-carriage 200 and a linear scale 232 mounted on the machine bed 100. The measuring head 231 performs its position measurement in a plane E3, which is perpendicular to the Y-direction (i.e., a normal plane to the Y-axis) and contains the C-axis. This plane E3 is particularly well suited for characterizing the position of the C-axis relative to the machine bed 100 with respect to the Y-direction and is therefore also referred to as the C-reference plane.

[0075] As with the Z-axis, all relevant components of the Y-axis are constructed identically in pairs and arranged symmetrically to the central center plane E1, in particular the Y-linear guides 201, the Y-drive motors 202, the ball screws 203, the vibration dampers and the Y-linear measuring systems 230. Centering device

[0076] For the hard fine machining of pre-toothed workpieces, a centering device 410 is arranged on the X-slide 310. This centering device is designed to determine the angular position of the tooth gaps of the workpiece 220 with respect to the C-axis without contact, so that the tool 330 can be brought into collision-free engagement with a pre-toothed workpiece 220. For this purpose, the centering device 410 has a centering probe 411 arranged at its lower end, which measures the tooth gaps in a conventional manner. The centering device 410 can be optionally attached to one of the two cheeks 313 of the X-slide 310. For this purpose, the two cheeks have fastening surfaces 412 with corresponding bores on their front sides (see Fig. 2 ). measuring bridge

[0077] In the Fig. 3An optical measuring bridge 420 can be clearly seen. This is mounted on the Y-slide 200 and serves to measure the tool 330. In particular, it can be a laser measuring bridge with a laser and photodetector. The measuring bridge 420 can be arranged either to the left or right of the center plane E1 on the workpiece carrier 200. For this purpose, corresponding mounting surfaces 421 with corresponding holes are provided on the Y-slide 200 to the left and right of the center plane E1 (see Fig. 4 ). The measurement of the tool can be carried out in particular according to WO 2019 / 115332 A1. tool changer

[0078] In the Fig. 5 A changing device 430 for automatically changing the tool is shown schematically. This is attached to the machine bed 100 and can also be arranged either to the left or right of the center plane E1. For this purpose, corresponding mounting surfaces 431 and holes are provided on the machine bed 100. Workpiece loader

[0079] As from the Fig. 5 As can be seen, the machine optionally features a workpiece loader 440. This can remove a finished workpiece 220 from the workpiece spindle 210 and replace it with a blank to be machined, or replace the workpiece clamping device. Depending on the customer's requirements, the workpiece loader 440 can be arranged to the left or right of the center plane E1.

[0080] To prevent collisions with the centering device 410, the measuring bridge 420, or the tool changing device 430 during workpiece changes, these additional components are arranged either to the left or right of the center plane E1, depending on the position of the workpiece loader 440. This is determined during machine design, depending on the customer's requirements.

[0081] Alternatively, the workpiece loader can also be arranged at the front end of the machining area 130 in the center plane E1, as is also shown in Fig. 5 is indicated. If necessary, it is also possible to arrange the workpiece loader in the rear area of ​​the machine, so that the loading and unloading process takes place through a recess in the vertical section 120 of the machine bed. For this purpose, the chip conveyor 500 is rotated by 180° relative to the arrangement of the Figures 1 to 6 arranged so that its rising area with the drive is located at the front end of the machining area 130. Due to the limited accessibility, this arrangement of the workpiece loader is only useful in exceptional cases. Second embodiment: horizontal workpiece axis

[0082] While the machine of the first embodiment has a vertically aligned workpiece axis C, it is also conceivable to align the workpiece axis C horizontally without deviating from the principles set out above. This is shown in the Fig. 6 Illustrated. Parts with the same function are identified by the same reference numerals as in the Figures 1 to 5 provided.

[0083] The machine bed 100 again has a horizontal section 110 and a vertical section 120. Unlike in the first embodiment, the Y-slide 200 serving as a workpiece carrier is now vertically displaceable on the vertical section 120, i.e. the Y-direction now runs vertically. Accordingly, the C-axis now runs horizontally. As in the first embodiment, the C-axis runs in a central center plane E1, and the Y-slide 200 is guided on the machine bed 100 symmetrically to the center plane by two linear guides. The Z-slide 300 is now horizontally displaceable on the horizontal section 110 of the machine bed 100 parallel to the C-axis, i.e. the Z-direction now runs horizontally. The Z-slide is again guided symmetrically to the center plane by two linear guides. The X-slide 310 serving as a tool carrier is arranged on the Z-slide 300 as in the first embodiment.It is constructed in the same way as the first version. Operating procedures

[0084] An operating method for a machine according to the first embodiment ( Figures 1 to 5 ) discussed.

[0085] To machine a raw part, the Y-slide 200 is first brought into a workpiece change position opposite to the Y-direction, as shown in the Figures 1 to 3 is illustrated. In this position, the last finished workpiece 220 is removed from the workpiece spindle 210 with the aid of the workpiece loader 440 and the blank to be machined is placed and clamped on the workpiece spindle 210. The Y-slide 200 is then moved along the Y-direction into a machining position as shown in the Fig. 5 is illustrated.

[0086] In the case of hard finishing, the Z-slide 300 and the X-slide 310 are now positioned so that the centering device can measure the tooth gaps of the blank. This determines the angular position of the tooth gaps of the blank.

[0087] The Z-slide 300 and the X-slide 310 are then brought into a position in which the tool 330 comes into engagement with the blank, as shown in Fig. 5 The B-axis runs either offset to the left or right of the machine tool's center plane, depending on the inclination of the workpiece and the tool. The workpiece is then machined in the usual way. The tool 330 and the workpiece 220 rotate at a fixed speed ratio. This forced coupling is achieved electronically by the machine's control system.

[0088] The tool is measured as needed using the measuring bridge 420. For a skiving tool, this can be done, for example, in a manner as described in WO 2019 / 115332 A1. Such a measurement can be performed, for example, after each tool change and periodically after a certain number of machining operations.

[0089] If the tool needs to be changed, this is preferably done using the changing device 430. Modifications

[0090] It is understood that the invention is not limited to the embodiments described above, but that various modifications are possible without departing from the scope of the invention.

[0091] For example, in the first embodiment, the Y-direction can also run at an angle to the horizontal, but still parallel to the center plane E1. This can be advantageous for design reasons or for loading and unloading the workpiece spindle. The Z-direction does not necessarily have to run parallel to the C-axis, as long as this direction also remains parallel to the center plane E1. The symmetry of the machine is not destroyed by such modifications.

[0092] A variety of further modifications are possible. In particular, the machine can also be used for other gear-cutting processes besides power skiving. The tools typical for each process, preferably gear-shaped, are used. Combinations of two or more machining processes can also be performed sequentially on the same machine. For example, it is conceivable for a workpiece to be first gear-skived and then gear-honed.

[0093] In addition to hard fine machining, this machine can also be used for soft machining, whereby only the centering probe needs to be deactivated and otherwise process-typical tools for soft machining are used. LIST OF REFERENCE SYMBOLS

[0094] 100 Machine bed 340 A-drive motor 110 Horizontal section 342 Leadscrew 120 Vertical section 343 Leadscrew axis 130 Machining area 344 Spindle nut 140 Rear area 346 Vibration damper 200 Y-slide / workpiece carrier 347 Angle measuring device 201 Y-linear guide 350 Z-linear measuring system 202 Y-drive motor 351 Measuring head 203 Ball screw 352 Linear scale 210 Workpiece spindle 410 Centering device 220 Toothed workpiece 411 Centering probe 230 Y-linear measuring system 412 Mounting surface 231 Measuring head 420 Measuring bridge 232 Linear scale 421 Mounting surface 300 Z-slide / tool ​​carrier 430 Tool changer 301 Z-linear guide 431 Mounting surface 302 Z-drive motor 440 Workpiece loader 303 Ball screw drive 500 Chip conveyor 310 X-slide / tool ​​carrier 501 Conveyor drive 311 X-linear guide 600 Control panel 312 X-drive motor A first swivel axis 313 Beam A' second swivel axis 314 first swivel bearing A" third swivel axis 315 second swivel bearing X, Y,Z Linear axes 320 Tool spindleE1 Center plane 323 Angle measuring deviceE2 Swivel plane 325 Third swivel bearingE3 C-reference plane 330 ToolE4 A-reference plane 331 Cutting planeα Axis cross angle,

Claims

1. A machine tool for the machining of rotary parts with groove-shaped profiles, in particular gears, by a generating method, comprising: a machine bed (100); a Y-slide (200), which is linearly displaceable along a Y direction relative to the machine bed (100); a workpiece spindle (210) which is arranged on the Y slide (200) and which is configured to clamp a workpiece (220) thereon and to drive it to rotate about a workpiece axis (C), the workpiece axis (C) extending transversely, preferably perpendicularly, to the Y direction; and a tool spindle (320) which is configured to clamp a generating machining tool (330), in particular a gear-shaped generating machining tool, on it and to drive it to rotate about a tool axis (B); and a controller which is configured to establish a positive coupling between the rotation of the generating machining tool (330) and the rotation of the workpiece (220), characterized in that the machine tool further comprises: a Z slide (300) which is arranged on the machine bed (100) and is linearly displaceable along a Z direction relative to the machine bed (100), the Z direction running parallel to a center plane (E1) defined by the Y direction and the workpiece axis (C), and the Z direction extending at an angle of less than 45°, preferably parallel, to the workpiece axis (C); and an X slide (310) arranged on the Z slide (300) and linearly displaceable along an X direction relative to the Z slide (300), the X direction being perpendicular to the center plane (E1); and in that the tool spindle (320) is arranged on the X slide (310) and is pivotable relative to the X slide (310) about a first swivel axis (A).

2. The machine tool according to claim 1, wherein the first swivel axis (A) is perpendicular to the center plane (E1), wherein the tool axis (B) extends perpendicular to the first swivel axis (A) and is pivotable about the first swivel axis (A) in a swivel plane (E2) that extends parallel to the center plane (E1), and wherein preferably the first swivel axis (A) intersects the tool axis (B).

3. The machine tool according to claim 2, wherein the machine tool comprises two first swivel bearings (314) for pivotably supporting the tool spindle (320) on the X slide (310) about the first swivel axis (A), wherein the two first swivel bearings (314) are arranged on both sides of the tool spindle (320) with respect to the swivel plane (E2) and preferably equidistantly from the swivel plane (E2).

4. The machine tool according to claim 2 or 3, comprising an adjustment mechanism (340, 342, 344) for adjusting the orientation of the tool spindle (320) relative to the X slide (310), wherein the adjustment mechanism (340, 342, 344) is connected to the X slide (310) so as to be pivotable about a second swivel axis (A'), the second swivel axis (A') extending parallel to and spaced apart from the first swivel axis (A), and wherein the adjustment mechanism (340, 342, 344) is connected to the tool spindle (320) so as to be pivotable about a third swivel axis (A"), the third swivel axis (A") extending parallel to and spaced apart from the first swivel axis (A) and the second swivel axis (A').

5. The machine tool according to claim 4, wherein the machine tool comprises two second swivel bearings (315) for pivotably supporting the adjustment mechanism (340, 342, 344) on the X slide (310) about the second swivel axis (A'), wherein the two second swivel bearings (315) are arranged on both sides and preferably equidistantly from the swivel plane (E2), and / or wherein the machine tool comprises two third swivel bearings (325) for pivotably mounting the adjustment mechanism (340, 342, 344) on the tool spindle (320) about the third swivel axis (A"), wherein the two third swivel bearings (325) are arranged on both sides and preferably equidistantly from the swivel plane (E2).

6. The machine tool according to claim 4 or 5, wherein the adjustment mechanism (340, 342, 344) comprises: an A drive motor (340), which is preferably mounted on the X slide (310) so as to be pivotable about the second swivel axis (A') a threaded spindle (342) drivable by the A drive motor (340) to rotate about a threaded spindle axis (343) extending perpendicular to the first swivel axis (A), the threaded spindle axis (343) extending in the swivel plane (E2); and a spindle nut (344) which is in engagement with the threaded spindle (342) and is preferably connected to the tool spindle (320) so as to be pivotable about the third swivel axis (A"), and wherein the machine tool optionally further comprises: a first angle measuring device (347) which is configured to determine a rotation angle of the threaded spindle (342) about the threaded spindle axis (343); and / or at least one second angle measuring device (323) which is configured to directly determine a swivel angle of the tool spindle (320) about the first swivel axis (A) relative to the X slide (310).

7. The machine tool according to any one of claims 4 to 6, wherein the tool spindle (320) has an end that faces the tool and an end that faces away from the tool, wherein a generating machining tool (330) is clamped on the tool spindle (320) at the end that faces the tool, the generating machining tool (330) defining a tool reference plane (331), in particular a cutting edge plane, which extends perpendicularly to the tool axis (B), wherein the first swivel axis (A) intersects the tool axis (B) between the end of the tool spindle (320) that faces the tool and the end that faces away from the tool, wherein the first swivel axis (A) and the tool reference plane (331) extend at a first distance (H) from each other, wherein the first swivel axis (A) and the third swivel axis (A") extend at a second distance (R) from each other, and wherein the second distance (R) and the first distance (H) have a ratio greater than 1, preferably a ratio of 1.5 to 3.

8. The machine tool according to any one of claims 2 to 7, comprising: at least one vibration damper (346), preferably two vibration dampers (346) arranged on both sides and preferably equidistantly from the swivel plane (E2), the vibration damper or dampers (346) acting between the tool spindle (320) and the X slide (310) in order to damp vibrations of the tool spindle (320) about the first swivel axis (A).

9. The machine tool according to any one of the preceding claims, wherein the tool spindle (320) is pivotable relative to the X slide (310) about the first swivel axis (A) in such a manner that an axis crossing angle (α) between the tool axis (B) and the workpiece axis (C) takes on either negative or positive values, the maximum positive value of the axis crossing angle (α) being greater than the magnitude of the smallest negative value.

10. The machine tool according to any one of the preceding claims, wherein the workpiece axis (C) runs vertically in space.

11. The machine tool according to any one of the preceding claims, wherein the machine tool comprises two mutually parallel Z linear guides (301) which extend parallel to the Z direction, are arranged on both sides and preferably equidistantly from the center plane (E1) and on which the Z slide (300) is guided along the Z direction relative to the machine bed (310), wherein the machine tool comprises two Z drives (302, 303) for moving the Z slide (300) along the Z direction relative to the machine bed (100), and wherein in each case one of the Z-drives (302, 303) is assigned to each of the Z linear guides (301), and wherein the machine tool optionally comprises at least one, preferably two Z linear measuring systems (350), each of the Z linear measuring systems (350) comprising a measuring head (351) mounted on the Z slide (300) and a linear scale (352) mounted on the machine bed (100), and wherein the measuring heads (350) of the Z linear measuring systems (350) are arranged such that they carry out a position measurement in an A reference plane (E4) which is perpendicular to the Z direction and contains the first swivel axis (A).

12. The machine tool according to any one of the preceding claims, wherein the machine tool comprises two parallel Y linear guides (201) which extend parallel to the Y direction, are arranged on both sides and preferably equidistantly from the center plane (E1) and on which the Y slide (200) is guided along the Y direction relative to the machine bed (100), wherein the machine tool comprises two Y drives (202, 203) for moving the Y slide (200) along the Y direction relative to the machine bed (100), and wherein in each case one of the Y drives (202, 203) is assigned to each of the Y linear guides (201), and wherein the machine tool optionally comprises at least one, preferably two Y linear measuring systems (230), each of the Y linear measuring systems comprising a measuring head (231) mounted on the Y slide (200) and a linear scale (232) mounted on the machine bed (100), and wherein the measuring heads (231) of the Y linear measuring systems (230) are arranged in such a way that they carry out a position measurement in a C reference plane (E3) which is perpendicular to the Y direction and contains the workpiece axis (C).

13. The machine tool according to any one of the preceding claims, wherein the machine tool comprises at least one of the following additional components: a meshing device (410) for determining a position of tooth gaps of the workpiece (220); an optical measuring bridge (420) for measuring the workpiece (220) and / or the tool (330); and a tool changing device (430) for changing the tool (330), and wherein the machine tool has two alternative fastening structures for each of the additional components, the alternative fastening structures being arranged on both sides of the center plane (E1).

14. The machine tool according to any one of the preceding claims, wherein the machine tool comprises a chip conveyor (500), which is preferably arranged in the center plane (E1), and wherein the machine bed (100) has a central opening to allow the discharge of chips onto the chip conveyor (500).

15. A method of machining a workpiece (220) with a machine tool according to any one of the preceding claims, the method comprising: bringing a generating machining tool (330) clamped on the tool spindle (320) into engagement with the workpiece (220) while the workpiece (220) is clamped on the workpiece spindle (210), wherein the engagement takes place in an arrangement of the generating machining tool (330) relative to the workpiece (220) in which the tool axis (B) extends at an offset to the center plane (E1) of the machine tool; and carrying out a generating machining operation on the workpiece with the machine tool, wherein the generating machining tool is preferably gear-shaped and is in particular a gear skiving tool.