MACHINE TOOL FOR MACHINING A WORKPIECE

Description

[0001] The present invention relates to a machine tool for machining a workpiece. BACKGROUND OF THE INVENTION

[0002] One of the most important components of a machine tool, especially one with a tool-carrying work spindle, is the tool-carrying machining unit. It plays a significant role in ensuring the accuracy of the manufactured parts, as it performs the material removal processes directly on the workpiece using the tool carried by the tool-carrying machining unit. Therefore, it is particularly important that the tool-carrying machining unit applies the contour defined by specified parameters to the workpiece as precisely as possible.

[0003] Typically, this is primarily achieved through numerically controlled axes, which offer the appropriate level of accuracy and reproducibility. However, depending on environmental conditions, workpiece weight, etc., the parameters controlling the axes must be adjusted accordingly.

[0004] The design of the machine tool itself can also have a significant influence on the extent of the correction of the control parameters, for example, if masses within the machine tool shift due to the infeed of the numerically controlled axes. This can lead to significant deviations in the actual position of the tool of the machining unit mounted in the work spindle, although these deviations can sometimes be difficult to correct using complex path corrections of the numerically controlled axes.

[0005] From US 2005 / 031429 A1, which forms the basis for the preamble of claim 1, CN 102 528 090 A, CN 104 723 155 A and JP H10 15769 A, machine tools are known which have two drives with a screw drive for moving the work spindle in the vertical direction, wherein the drives and the screw drives change their relative position with respect to the work spindle when the work spindle is moved in the vertical direction.

[0006] From DE 11 12 376 B and JP H05 60748 U, machine tools are known which have a drive with a screw drive for moving the work spindle in the vertical direction, wherein when the work spindle is moved in the vertical direction, the drive changes its relative position to the work spindle.

[0007] In addition, DE 200 19 035 U1 discloses a machine tool which has two racks for moving the work spindle in the vertical direction, wherein the work spindle can also be pivoted about a pivot axis. SUMMARY OF THE INVENTION

[0008] An object of the present invention is therefore to provide a machine tool with which the above problem can be avoided, in particular so that a simplified path correction is possible and at the same time the accuracy of the machining process is improved.

[0009] To achieve this object, the invention proposes a machine tool for machining a workpiece according to claim 1. The dependent claims relate to advantageous embodiments of the machine tool according to the invention.

[0010] The machine tool according to the invention for machining a workpiece is defined in claim 1.

[0011] The inventive design of the machine tool, whereby the center of gravity of the machining unit is positioned so that it lies either within the effective point of the suspension or on a vertically oriented straight line that passes through the effective point, makes it possible for the vertical and horizontal guides of the machining unit to be subjected to either a negligibly small torque, e.g. in the case of the vertical guide, or a constant torque, e.g. in the case of the horizontal guides, which is generated by the mass of the machining unit and the distance from the effective point of the suspension.

[0012] This measure facilitates path correction of the corresponding numerically controllable axes, as the vertical position of the machining unit, which significantly influences the torques occurring in the guides in a conventional machine tool design, needs to be taken into account to a much lesser extent. This is particularly advantageous because this design measure leads to increased geometric accuracy in the infeed of the machining unit and thus to increased accuracy of the machined workpiece, since the influence of the mass of the machining unit on the guides remains constant.

[0013] By optimizing the suspension of the machining unit, a problem in the correction of the paths of the moving parts of a machine tool could be avoided or simplified to essentially constant values, so that in addition to a simpler path correction, increased accuracy in the production of the workpiece could be achieved.

[0014] The drive mechanism is carried along with the machining unit in order to increase the mass of the machining unit. This allows the machining unit to react somewhat more slowly to suddenly occurring forces during the machining process of the workpiece, which in turn can have a positive influence on the result of the machining process.

[0015] For example, in a variant not claimed here, the machine tool can be designed such that the effective point of the suspension in the case of a transmission is arranged in the suspension itself.

[0016] This ensures, as in the case of multiple gearboxes where the point of action of the suspension is located essentially in the middle of individual suspensions that form the suspension in the case of multiple gearboxes, that the center of gravity of the machining unit does not generate any torque or at least a constant torque in the vertical and horizontal guides of the machine tool, regardless of the vertical position of the machining unit.

[0017] A further advantageous development of the machine tool according to the invention is that the machining unit is suspended from the one or more gear sections of the at least two gears of the drive mechanism in such a way that a constant torque acts on the carrier section in the vertical direction during the movement.

[0018] In a non-claimed embodiment of the machine tool with only one gear of the drive mechanism, the machining unit can also be suspended from the one or more gear sections of the one gear in such a way that a constant torque acts on the carrier section during the movement in the vertical direction.

[0019] Furthermore, the machine tool according to the invention can be advantageously further developed in that the machining unit is suspended from the one or more gear sections of the at least two gears of the drive mechanism in such a way that during the movement in the vertical direction, substantially no torque acts on the at least one vertical guide of the carrier section.

[0020] In a non-claimed embodiment of the machine tool with only one gear of the drive mechanism, the machining unit can also be suspended from the one or more gear sections of the one gear in such a way that during the movement in the vertical direction, substantially no torque acts on the at least one vertical guide of the carrier section.

[0021] Both developments enable a smaller degree of correction of the numerically controlled axes due to changing loads and torques, which arise from the displacement of masses within the machine tool, in particular those of the machining unit.

[0022] In a variant not claimed, the drive mechanism of the machine tool can be arranged such that the drive mechanism maintains its relative position to the support section during the movement of the machining unit in the vertical direction and the relative position of the point of action of the suspension to the machining unit remains substantially constant.

[0023] In a further variant of the machine tool not claimed, both the drive mechanism and the point of action of the suspension can be arranged such that they maintain their relative position to the support section during the movement of the machining unit in the vertical direction.

[0024] In a further, unclaimed variant of the machine tool, both the drive mechanism and the point of action of the suspension can be arranged such that they maintain their relative position to the machining unit during the movement of the machining unit in the vertical direction.

[0025] The mentioned design options for the suspension and positioning of the drive mechanism should be understood as exemplary variants that can be used depending on the application and requirements of the machine tool.

[0026] One advantage, for example, may be that the drive of the drive mechanism, which also represents a heat source, remains on the support or support section of the machining unit, while the effective point or a suspension point of the suspension is moved with the machining unit. This advantageously keeps a heat source (drive of the drive mechanism) away from the machining area closer to the workpiece, so that the heating of the drive would only have a minimal impact on the machining process.

[0027] The machine tool according to the invention can be advantageously further developed in that during the movement of the machining unit the effective point of the suspension and / or the center of gravity of the machining unit move along the vertically oriented straight line.

[0028] This ensures that, regardless of the vertical position of the machining unit, the torque ratios acting on the machining unit's guides do not change significantly. Furthermore, the correction effort required for the numerically controlled axes can be significantly reduced.

[0029] In addition, the machine tool according to the invention can be advantageously further developed in that the drive mechanism is designed as a self-locking drive mechanism.

[0030] A self-locking drive mechanism makes it possible to position the machining unit along the vertical axis, whereby no further securing measures or locking devices are necessary in this position, since the drive mechanism does not allow any further adjustment of the position of the machining unit without being moved by the drive.

[0031] The machine tool according to the invention can also be advantageously further developed in that the drive mechanism comprises at least one screw drive, preferably at least one ball screw drive.

[0032] As an implementation of a self-locking drive mechanism, a screw drive is known which, due to a corresponding thread pitch, only allows an adjustment of the vertical position of the machining unit if the thread-bearing element (threaded element, e.g. a threaded rod with a ball screw, trapezoidal thread or another thread form) is driven accordingly by an electric, pneumatic or hydraulic drive.

[0033] An advantageous development of the machine tool according to the invention consists in that, in a gear unit, the at least one vertical guide of the machining unit is arranged such that the center of gravity of the machining unit is displaced substantially concentrically to a threaded rod of the screw drive when the machining unit is moved in the vertical direction, in particular along the vertically oriented straight line.

[0034] Furthermore, the machine tool according to the invention can be advantageously further developed in that the threaded rod is arranged axially with the vertically oriented straight line.

[0035] If, for example, the drive mechanism has a drive and a gear for moving the machining unit along the vertical direction, it can be extremely advantageous to place the center of gravity of the machining unit directly at the suspension point. The reason for this is that the center of gravity would then lie directly in the cross-section of the threaded rod, which would therefore only subject the threaded rod to tensile or compressive stress and at the same time would essentially free the vertical guide of the machining unit from the absorption of torque generated due to the distance between the center of gravity of the machining unit and the guide line of the guides. This can enable significantly more precise guidance of the machining unit in the vertical direction, as the forces acting on the guide are considerably reduced.

[0036] The machine tool according to the invention can be advantageously further developed in that the drive mechanism comprises at least one gear-rack combination, preferably at least one helical gear-rack combination.

[0037] Furthermore, the drive mechanism can be designed in the form of a rack with a corresponding driving gear, whereby this embodiment does not have the self-locking properties of a screw drive.

[0038] Furthermore, the machine tool according to the invention can be advantageously further developed in that, in the case of a gear, the at least one vertical guide of the machining unit is arranged in such a way that the center of gravity of the machining unit is guided essentially at the contact point of the pitch circle of the gear wheel and the pitch line of the rack when the machining unit is moved in the vertical direction.

[0039] At this point the behavior is very similar to the threaded rod, so that it can be extremely advantageous if the drive mechanism, for example, has a drive and a gear for moving the machining unit along the vertical direction, and the center of gravity of the machining unit is placed directly at the suspension point (the suspension point here is the contact point between the pitch circle of the gear and the pitch line of the rack). In this case the rack would be subjected exclusively to tensile or compressive loads and at the same time the vertical guide of the machining unit would be essentially freed from having to absorb any torque that is generated due to the distance between the center of gravity of the machining unit and the guide line of the guides. This can enable significantly more precise guidance of the machining unit in the vertical direction, since the forces acting on the guide are considerably reduced.

[0040] The machine tool according to the invention can be advantageously further developed in that the machining unit comprises a spindle carrier carrying a work spindle.

[0041] In addition, the machine tool according to the invention can be advantageously further developed in that the spindle carrier comprises a pivoting device for pivoting the work spindle about a pivot axis.

[0042] This allows for a wide range of applications for the machining unit's work spindle, as the spindle support allows it to be pivoted through a wide angular range, e.g., from +90° to -90° for vertical alignment of the work spindle. In some cases, the angular range can also be selected to be larger. This may depend, for example, on the bending behavior of the work spindle's supply lines.

[0043] Furthermore, it may be advantageous to further develop the machine tool according to the invention in such a way that the pivot axis is arranged perpendicularly or obliquely, preferably at a 45° angle, to a spindle axis of the work spindle.

[0044] This allows the work spindle, or the tool holder of the work spindle, to be swiveled in an angular range of 0° to 90° (e.g. with a swivel axis set at 45° to the spindle axis).

[0045] A particularly advantageous development of the machine tool according to the invention results from the fact that a pivotable section of the spindle carrier holding the work spindle, with which the work spindle can be pivoted about the pivot axis, is arranged such that a common center of gravity of the pivotable section and the work spindle lies at the intersection point of the pivot axis and the vertically oriented straight line.

[0046] This allows the work spindle or a pivoting section of the spindle carrier to be pivoted particularly advantageously without shifting the center of gravity of the machining unit, since the common center of gravity of the work spindle and the pivoting section remains unchanged despite pivoting. This allows the influence of the torques generated by the moving masses of the machining unit on the guides to be kept constant or negligibly low.

[0047] A further advantageous development of the machine tool according to the invention consists in that the support section is designed as a machine stand arranged on a machine bed.

[0048] This allows the machine carrier to be fixed in its position relative to the machine bed, whereby the work spindle can be fed directly to the machining unit.

[0049] The machine tool according to the invention can be advantageously further developed in that the carrier section comprises a horizontally movable slide section.

[0050] In addition, the machine tool according to the invention can be advantageously further developed in that the slide section is mounted on guides on a horizontally movable portal structure of a gantry machine tool.

[0051] Advantageously, the design of the suspension of the machine tool according to the invention can be applied to a movable portal structure of a gantry machine tool.

[0052] The inventive machine tool for machining a workpiece has simplified the necessary corrections to the paths of the guided elements, as the masses moved during the feed of the machining unit now either generate a constant torque in the guides or, in certain guides, even generate a negligibly small torque, regardless of the vertical position of the machining unit, which otherwise had a significant influence on the acting torques. This can be advantageously used when correcting the paths for the numerically controllable axes, which in turn leads to increased manufacturing accuracy, as the geometric accuracy of the machine tool has been improved.

[0053] Further aspects and their advantages as well as advantages and more specific embodiments of the aspects and features described above are described in the following, but in no way limiting, descriptions and explanations of the attached figures. BRIEF DESCRIPTION OF THE CHARACTERS

[0054] Fig. 1 schematically shows a perspective view of an embodiment of a machine tool according to the invention; Fig. 2 schematically shows a side view of an embodiment of the machine tool according to the invention Fig. 1 ; Fig. 3 shows schematically a front view of an embodiment of the machine tool according to the invention from Fig. 1 ; Fig.4 shows schematically a detailed view of a suspension of the machining unit of the machine tool according to the invention Fig. 1 ; Fig. 5 schematically shows a detailed side view of an embodiment of a machine tool according to the invention with a screw drive as a gear for moving the machining unit; Fig. 6a schematically shows the point of action of the suspension when the drive mechanism has a gear (here screw drives), this embodiment not falling under the valid set of claims; Fig. 6b schematically shows the point of action of the suspension when the drive mechanism has two gears (here screw drives); Fig. 6c schematically shows the point of action of the suspension when the drive mechanism has three gears (here screw drives); Fig. 7a schematically shows an embodiment of the machine tool according to the invention with a modified arrangement of the vertical guide; and Fig. 7b schematically shows an embodiment of the machine tool according to the invention with a modified arrangement of the vertical guide in a side view. DETAILED DESCRIPTION OF THE FIGURES AND PREFERRED EMBODIMENTS OF THE PRESENT INVENTION

[0055] Examples and embodiments of the present invention are described in detail below with reference to the accompanying figures. Identical or similar elements in the figures may be designated by the same reference numerals.

[0056] Fig. 1 shows, by way of example, a schematic perspective view of an embodiment of a machine tool 100 according to the invention. The machine tool 100 is constructed, for example, in a gantry design and has a machine bed 70 which can be set up on adjustable feet and on which, for example, a workpiece clamping table 80 is arranged, on which workpieces can be clamped for machining.

[0057] Fig. 2 shows, by way of example, a schematic side view of an embodiment of the machine tool according to the invention from Fig. 1 . Fig. 3 shows, by way of example, a schematic front view of an embodiment of the machine tool according to the invention from Fig. 1 .

[0058] On the sides of the machine bed 70, horizontal guides 71 are arranged horizontally in an X-direction, for example, on which a gantry column 60 is guided for horizontal movement in the X-direction. To drive the horizontal movement of the gantry column 60, threaded rods 72 are arranged on both sides, parallel to the guides 71, for example, and are driven by drives 73.

[0059] On the front side of the gantry stand 60, horizontal guides 61 are arranged horizontally in a Y-direction, for example, on which a support section 30 is guided for horizontal movement in the Y-direction. To drive the horizontal movement of the support section, a threaded rod 62 is arranged parallel to the guides 61, for example, and is driven by a drive 63, for example.

[0060] On the support section 30, a machining unit 10 is held, for example, so as to be vertically movable in the Z-direction, and on the underside of the machining unit, a spindle support unit 13 is held, for example, on which a tool-carrying work spindle 16 is arranged. The spindle support unit 13 is also configured, for example, to be rotated about the vertical axis and, for example, the spindle support unit 13 furthermore has, for example, a horizontal pivot axis. In an alternative embodiment according to Fig. 5 the swivel axis can also be inclined at an oblique angle (e.g. at 45° to the vertical axis of rotation).

[0061] The rotation axis and the swivel axis provide two rotational degrees of freedom for the relative movement of the tool clamped in the work spindle 16 and the tool on the workpiece clamping table 80, in addition to the three translational degrees of freedom of the aforementioned X, Y, and Z axes. For example, the machine tool 100 is therefore designed as a 5-axis machine tool.

[0062] The machining unit 10 is, for example, vertically movable by means of a vertical guide 18. According to the invention, however, the machining unit 10 is not suspended from the support section 30 via the guide 18, but rather, for example, on suspension sections 50, which are, for example, attached to the support section 30. For example, two threaded rods 22 are arranged vertically on the machining unit 10, which are driven via drives 21 on the top side of the machining unit 10.

[0063] Fig. 4 shows, by way of example, a schematic detailed view of a suspension of the machining unit of the machine tool according to the invention Fig. 1 . For example, the processing unit 10 is suspended at suspension points 11 on the suspension sections 50, for example by suspending the threaded rods 22 at the suspension points 11 on the suspension sections 50.

[0064] Analogous to Fig. 6b The suspension of the processing unit 10 is designed with two suspension points 11 of the two suspension sections 50 lying in a horizontal plane, wherein the effective point 12 of the suspension lies exactly between the suspension points 11 of the two suspension sections 50 (see Fig. 6b ). According to the invention, the machining unit 10 is designed in such a way that the center of gravity 101 of the entire machining unit 10 with spindle carrier unit 13 lies in a horizontal straight line with the effective point 12 of the suspension exactly between the suspension points 11 of the two suspension sections 50 (see also the principle according to Fig. 5 and description).

[0065] Consequently, the entire weight of the machining unit 10 with spindle support unit 13 is always evenly distributed across the two suspension points 11 from which the threaded rods 22 are suspended, regardless of the vertical Z position of the machining unit 10. This has the advantageous effect that when the machining unit 10 is moved in the Z direction, the same weight is always suspended on the suspension sections 50, and thus, regardless of the Z position of the machining unit 10, the same torque always acts on the support section 30 via the suspension sections 50. The vertical guide 18 of the machining unit 10 is always relieved of load at the guide elements 32 of the support section, and essentially no torque occurs on this guide.

[0066] In addition, regardless of the Z position of the machining unit 10, the same torque always acts on the support section 30 via the suspension sections 50, so that the same torques always act on the horizontal guides 61 of the support section 30 on the front of the gantry section 60, regardless of the Z position of the machining unit 10, so that the position accuracy only has to be set once (e.g. by numerical compensation in the CNC machine control), although no Z position-dependent compensations have to be carried out, since the forces and torques acting from the support section 30 on the gantry section 60 are independent of the Z position of the machining unit 10.

[0067] Fig. 5 shows, by way of example, a schematic detailed view of an embodiment of a machine tool 100 according to the invention with a screw drive as a gear 22 for moving the machining unit 10.

[0068] The machining unit 10 is connected to the support section 30, for example, via a suspension 11, which is adjusted in the vertical direction via a rotatably mounted threaded rod (here, for example, as a gear 22) that can be driven by a drive 21, in such a way that the relative position of the machining unit 10 to the support section 30 can be adjusted in the vertical direction by rotating the threaded rod.

[0069] In the embodiment as shown in Fig. 5 , it can be seen that the threaded rod follows the movement of the machining unit 10 in the vertical direction when rotating. This means that the drive 21 and gear 22 of the drive mechanism 20 are firmly connected to the machining unit 10, and the suspension 11 is firmly connected to the support section 30.

[0070] In addition, it can be seen that the center of gravity 101 of the machining unit 10 is located on the threaded rod in a side view, as shown in the side view of the structure of the machine tool 100 in Fig. 5 is illustrated. If the drive mechanism 20 has only one drive 21 and one gear 22 for vertical positioning of the machining unit 10, the center of gravity 101 would essentially be located in one threaded rod, so that the entire weight of the machining unit 10 would load the threaded rod evenly and independently of the Z position in tension / compression, even if no guide 18, 32 were present. If two threaded rods are provided (see Fig. 3 ), the effective point 12 of the suspension is exactly between the suspension points 11 and thus the center of gravity 101 would essentially lie between the threaded rods so that the entire weight of the machining unit 10 applies tension / compression loads to the threaded rods evenly and independently of the Z position, even if no guide 18, 32 were present.

[0071] This has the advantage that the guide 18, 32 is significantly relieved of load, since during vertical movement of the machining unit 10 and in the different positions of the machining unit 10, essentially no torque is generated due to the distance of the suspension 11 (coinciding with an effective point 12 of the suspension 11) from the center of gravity 101. Thus, the guide 18, 32 of the machining unit 10 can be designed for considerably lighter loads and / or ensure greater guidance accuracy of the machining unit 10 over the entire guide length during the vertical positioning of the machining unit 10.

[0072] The inventive design of the machine tool 100 effectively separates load bearing and guide accuracy. In contrast, in a conventional design, the guide accuracy and a large portion of the load bearing are accomplished by the corresponding guide. This can result in deformation of the guide when moving movable masses or loads along the guide if the majority of the loads must be absorbed by the guide. Because a guide can never be designed to be infinitely rigid, a compromise between guide accuracy and load bearing must always be found in a conventional design.

[0073] The machine tool 100 according to the invention makes it possible to largely avoid such a compromise, since the entire load / mass of the machining unit 10 is distributed on the drive mechanism 20 (or on the threaded rod of the gear 22, as shown in Fig. 5 ) in such a way that the center of gravity 101 of the machining unit 10 lies in the threaded rod. This also avoids the generation of a torque due to the distance of the suspension 11 (coinciding with the effective point 12 of the suspension 11) from the center of gravity 101, which would have to be absorbed by the guide 18, 32. As a result, the guide 18, 32 only needs to absorb significantly lower loads for the vertical positioning of the machining unit 10, which leads to a considerable improvement in the guidance accuracy over the entire length of the guide 18, 32.

[0074] In addition to the construction of the drive mechanism 20 with a drive 21 and a gear 22, for example, two or more drives 21 and correspondingly two or more gears 22 may be present for the vertical positioning of the processing unit 10. This would result in the point of action 12 of the suspension 11 being essentially in the middle of the corresponding distribution of the suspensions 11 (see, for example, Fig. 6b und 6c ). The center of gravity 101 of the machining unit 10 would then be positioned such that the center of gravity 101 of the machining unit 10 and the point of action 12 of the suspension 11 have a common vertically oriented straight line 23. The center of gravity 101 of the machining unit 10 can then move along this vertically oriented straight line 23 during the vertical positioning of the machining unit 10, without a significant torque arising due to a distance of the vertically oriented straight line 23 from the center of gravity 101, which torque would have to be absorbed by the guide 18, 32.

[0075] However, the machine tool 100 can also be constructed in such a way that the drive mechanism 20 is attached to the support section 30 with at least one drive 21 and at least one gear 22, so that the suspension 11 is attached to the machining unit 10 and moves with the machining unit 10 when the machining unit 10 is positioned vertically. Such an embodiment does not fall under the valid set of claims.

[0076] In addition to the drive mechanism 20 being designed with a threaded rod, the drive mechanism 20 can also be designed as a combination of a rack and a gear. In this case, a drive 21 (e.g., electric, hydraulic, or pneumatic) would set the gear in rotation and thereby move the rack accordingly in translation.

[0077] A significant difference to the design of the drive mechanism 20 with the threaded rod is that both the drive mechanism 20 and the point of action 12 of the suspension 11, which in this case is the contact point between the pitch circle of the gear and the pitch line of the rack, maintain either their relative position to the support section 30, in which case the drive mechanism 20 is attached to the support section 30, or to the machining unit 10, in which case the drive mechanism 20 is attached to the machining unit 10.

[0078] Furthermore, the machining unit 10 has a spindle carrier 13 on which a work spindle 16 is provided. By advancing the machining unit 10, a clamped workpiece, which is clamped, for example, on a machine table or on or in another device, can be machined according to a program for controlling the numerically controllable axes of the machine tool 100.

[0079] Furthermore, the spindle carrier 13 can have a pivoting device 14, with which a pivotable section 15 of the spindle carrier 13, in which the work spindle 16 is provided, can be pivoted according to a pivot axis 17.

[0080] The pivot axis 17 can enable the pivotable section 15 of the spindle support 13 to be pivoted within an angular range of +90° to -90°. A further embodiment of the pivoting device 14 with a corresponding pivot axis 17 can be such that the pivot axis 17 is aligned at an angle of preferably 45° to the vertically oriented straight line 23 or to the spindle axis of the work spindle 16. This allows the spindle axis of the work spindle 16, which is provided in the pivotable section 15 of the spindle support 13, to be pivoted within an angular range of 0° to 90°.

[0081] Particularly advantageously, the pivot axis 17 can be aligned such that the common center of gravity of the work spindle 16 and the pivotable section 15 of the spindle support 13 is located at the intersection point of the pivot axis 17 with the vertically oriented straight line 23. This allows the work spindle 16 to be pivoted about the pivot axis 17 without shifting the common center of gravity of the work spindle 16 and the pivotable section 15 of the spindle support 13 and thus without shifting the center of gravity (overall center of gravity) of the machining unit 10.

[0082] The processing unit 10 is, as in the embodiment in Fig. 5 As shown, the workpiece is guided by a guide 18, 32 with guide rails 18 of rectangular cross-section. The guide rails 18 are firmly connected to the machining unit 10, so that they follow a vertical positioning of the machining unit 10. Guide carriages 32, which are firmly connected to the support section 30, ensure safe and precise guidance of the machining unit 10 relative to the support section 30.

[0083] The design of the guides 18, 32 can vary greatly. In addition to a rectangular cross-section of the guide rails 18, a round or triangular cross-section for the guide rails 18 can also be advantageous. However, the design possibilities mentioned are not exhaustive; they should be understood merely as examples.

[0084] In addition to the cross-section of the rail 18, which also determines the shape of the guide carriages 32, the type of guide 18, 32 can also vary greatly. In addition to conventional sliding guides, so-called recirculating ball bearing guides can also be used, with the recirculating ball always being located in the guide carriages 32. These have the advantage of being extremely rigid and exhibiting significantly lower friction and resistance values ​​than conventional sliding guides.

[0085] Furthermore, the support section 30 can have a carriage section 31, with which the vertically guided machining unit 10 can be moved along a horizontal direction. The carriage section 31 can also be used as a support structure for the guide rails 18 or as a support structure for the guide carriages 32 and can also have drives 21 and gears 22 both for the vertical positioning of the machining unit 10 and drives and gears for the horizontal positioning of the machining unit 10, wherein the carriage section 31 would be moved during the horizontal positioning.

[0086] Fig. 6a shows schematically the point of action 12 of the suspension 11 when the drive mechanism 20 has a gear 22 (here a screw drive). As a result, the point of action 12 of the suspension 11 is located directly in the screw drive (threaded rod), so that the center of gravity 101 of the machining unit 10 is advantageously placed either directly in the point of action 12, or at least on the vertically oriented straight line 23 (in Fig. 6a not shown, see Fig. 5 ). Due to the vertical positioning of the machining unit 10, the center of gravity 101 of the machining unit 10 is guided along the vertically oriented straight line 23 and thus generates either a constant or a negligibly small torque in the corresponding guides (e.g., guides 18, 32) of the machine tool 100.

[0087] Fig. 6b shows schematically the point of action 12 of the suspension 11 when the drive mechanism 20 has two gears 22 (here two screw drives). As a result, the point of action 12 of the suspension 11 is located essentially in the middle of the two suspensions 11 (with their suspension points being located essentially in the middle of the threaded rod), so that the point of action 12 has essentially the same distance (L1 = L2) to the suspensions 11. Due to this, the center of gravity 101 of the machining unit 10 can advantageously be placed either directly in the point of action 12, or at least on the vertically oriented straight line 23 (in Fig. 6b not shown, see Fig. 5 ). Here, too, due to the vertical positioning of the machining unit 10, the center of gravity 101 of the machining unit 10 can be guided along the vertically oriented straight line 23 and thereby generates either a constant or a negligibly small torque in the corresponding guides (e.g., guides 18, 32) of the machine tool 100.

[0088] Fig. 6c shows schematically the point of action 12 of the suspension 11 when the drive mechanism 20 has three gears 22 (here screw drives). As a result, the point of action 12 of the suspension 11 is located essentially in the center of the spatial distribution of the three suspensions 11 (with their suspension points located essentially in the center of the threaded rod), so that the point of action 12 has essentially the same distance (L1 = L2 = L3) to the suspensions 11. Due to this, the center of gravity 101 of the machining unit 10 can advantageously be placed either directly in the point of action 12, or at least on the vertically oriented straight line 23 (in Fig. 6b not shown, see Fig. 5 ). At this point, the center of gravity 101 of the machining unit 10 can again be guided along the vertically oriented straight line 23 by the vertical positioning of the machining unit 10, and here too, generates either a constant or a negligibly small torque in the corresponding guides (e.g., guides 18, 32) of the machine tool 100.

[0089] The position of the point of action 12 in an embodiment of the drive mechanism 20 with a gear-rack combination would, in view of the Figuren 6a bis 6c shown position of the effective point 12 in a screw drive, comparable. This means that in the case of a rack and a gear, the effective point 12 of the suspension 11 would be located directly at the contact point of the pitch circle of the gear and the pitch line of the rack (compare Fig. 6a and corresponding description) that with two racks and correspondingly two gears, the effective point 12 of the suspension 11 would be essentially in the middle (L1 = L2) of the contact points of the pitch circle of the gears and the pitch line of the racks (compare Fig. 6b and corresponding description), and that with three racks and correspondingly three gears, the effective point 12 of the suspension 11 is essentially in the middle (L1 = L2 = L3) of the spatial distribution of the contact points of the pitch circle of the gears and the pitch line of the racks (compare Fig. 6c and corresponding description) and thus would generate either a constant or a negligible torque in the corresponding guides (e.g. guide 18, 32) of the machine tool 100.

[0090] Fig. 7a shows schematically an embodiment of the machine tool 100 according to the invention with a modified arrangement of the vertical guide 18, 32. Fig. 7a the drive mechanism 20 with a drive 21 and a gear 22 is not shown in order to be able to see the design of the modified, vertical guide 18, 32 somewhat better.

[0091] The guides 18, 32 have been modified such that the guide carriages 32 are now attached to the machining unit 10, so that they move along with the machining unit 10 during vertical positioning. The guide rails 18 are therefore attached to the support section 30 or to the carriage section 31, respectively.

[0092] The advantage of such a design of the guide 18, 32 is that the vertical distance between the work spindle 16 held in the spindle carrier 13 or a tool accommodated by the work spindle 16 and the guide carriages 32 is always constant, so that they function as support points in any position of the machining unit 10. If forces arise on the tool, for example, acting in a horizontal direction, the machining unit 10 behaves like a deforming structure that is firmly connected to the carrier section 30 or the carriage section 31 by the support points (here the guide carriages 32).

[0093] Advantageously, with known forces acting on the tool, for example, and with known structural conditions of the machining unit 10, the rigidity behavior of the machining unit 10 can now be very accurately predicted. Since the support points (guide carriage 32) always have the same position in relation to the machining unit 10, the rigidity behavior of the machining unit 10 is constant in all vertical positions of the machining unit 10 relative to the support section 30 / slide section 31, since there is no change in the distance from the work spindle 10 or the tool mounted in the work spindle 10 to the support points (guide carriage 32). This now enables very precise correction of the numerically controlled axes, regardless of the vertical positioning of the machining unit 10.

[0094] Fig. 7b shows schematically an embodiment of the machine tool 100 according to the invention with a modified arrangement of the vertical guide 18, 32 in a side view. Fig. 7b the drive mechanism 20 with a drive 21 and a gear 22 is not shown in order to be able to see the design of the modified, vertical guide 18, 32 somewhat better.

[0095] In addition, compared to Fig. 7a , in Fig. 7b the processing unit 10 is shown in two different vertical positions, wherein in the left illustration the processing unit 10 is seen in a vertically lower position and in the right illustration the processing unit 10 is seen in a vertically upper position.

[0096] Comparing the two illustrations, one can see how the guide carriages 32 of the machining unit 10 follow their respective vertical positions, thus ensuring that the distance between the work spindle 16 or a tool mounted in the work spindle 16 and the guide carriages 32 is always constant. This leads to the constant stiffness behavior under known forces, as already described above, regardless of the vertical position of the machining unit 10. LIST OF REFERENCE SYMBOLS

[0097] 10 Machining unit 11 Suspension 12 Effective point of the suspension 13 Spindle carrier 14 Swivel device 15 Swiveling section of the spindle carrier 16 Work spindle 17 Swivel axis 18 Guide rail (Z-guides) 20 Drive mechanism 21 Drive (Z-drive) 22 Gearbox (threaded rods) 23 Vertically oriented straight line 30 Support section 31 Slide section 32 Guide slide 50 Suspension section 60 Portal section 61 Guides (Y-guides) 62 Threaded rod 63 Y-drive 70 Machine bed 71 Guides (X-guides) 72 Threaded rods 73 X-drive 80 Workpiece clamping table 100 Machine tool 101 Center of gravity of the machining unit

Claims

1. A machine tool (100) for machining a workpiece, comprising: - a support portion (30) on which at least one vertical guide (18, 32) is disposed, - a machining unit (10) for machining a workpiece on said machine tool (100), said machining unit (10) being guided so as to be vertically movable on the at least one vertical guide (18, 32) of said support portion (30), - a drive mechanism (20) having at least two drives (21) and at least two gearboxes (22), said drive mechanism (20) being configured to drive a movement of said machining unit (10) in the vertical direction along the at least one vertical guide (18, 32) of said support portion (30), wherein said machining unit (10) is suspended from one or a plurality of gearbox portions of the at least two gearboxes (22) of said drive mechanism (20) in such a manner that the center of gravity (101) of said machining unit (10) is disposed in a common vertically oriented straight line (23) together with a working point (12) of said suspension (11) of said machining unit (11) on said drive mechanism (20), said working point (12) being disposed substantially in the center of individual suspensions of said suspension (11), characterized in that said drive mechanism (20) is disposed in such a manner that said drive mechanism (20) maintains the position thereof relative to said machining unit (10) during the movement of said machining unit (10) and the position of the working point (12) of said suspension (11) relative to said support portion (30) remains substantially constant.

2. The machine tool (100) according to claim 1, characterized in that said machining unit (10) is suspended from the one or the plurality of gearbox portions of the at least two gearboxes (22) of said drive mechanism (20) in such a manner that a constant torque acts on said support portion (30) during the movement in the vertical direction.

3. The machine tool (100) according to claim 1 or 2, characterized in that said machining unit (10) is suspended from the one or the plurality of gearbox portions of the at least two gearboxes (22) of said drive mechanism (20) in such a manner that substantially no torque acts on the at least one vertical guide (18, 32) of said support portion (30) during the movement in the vertical direction.

4. The machine tool (100) according to one of the preceding claims, characterized in that the working point (12) of said suspension (11) and / or the center of gravity (101) of said machining unit (10) move along the vertically oriented straight line (23) during the movement of said machining unit (10).

5. The machine tool (100) according to one of the preceding claims, characterized in that said drive mechanism (20) is configured as a self-locking drive mechanism, and said drive mechanism (20) comprises at least one screw jack, preferably at least one ball screw jack, and in a gearbox (22), the at least one vertical guide (18, 32) of said machining unit (10) is disposed in such a manner that the center of gravity (101) of said machining unit (10) is displaced in a manner substantially concentric with a threaded bar of the screw jack, in particular along the vertically oriented straight line (23), during the movement of said machining unit (10), and the threaded bar is disposed so as to be axial to the vertically oriented straight line (23).

6. The machine tool (100) according to claim 4, characterized in that said drive mechanism (20) comprises at least one gear-and-rack combination, preferably at least one helical-cut gear-and-rack combination, and in a gearbox (22), the at least one vertical guide (18, 32) of said machining unit (10) is disposed in such a manner that the center of gravity (101) of the machining unit (10) is guided substantially at the contact point of the pitch circle of the gear wheel and the pitch line of the rack during the movement of said machining unit (10).

7. The machine tool (100) according to one of the preceding claims, characterized in that said machining unit (10) comprises a spindle carrier (13) that supports a work spindle (16), and said spindle carrier (13) comprises a pivot device (14) for pivoting said work spindle (16) about a pivot axis (17), and said pivot axis (17) is disposed so as to be perpendicular or oblique, preferably at an angle of 45°, in relation to a spindle axis of said work spindle (16).

8. The machine tool (100) according to claim 7, characterized in that a pivotable portion (15) of said spindle carrier (13) which holds said work spindle (16) and by way of which said work spindle (16) is pivotable about said pivot axis (17) is disposed in such a manner that a common center of gravity of said pivotable portion (15) and of said work spindle (16) is located at the intersection point of said pivot axis (17) and the vertically oriented straight line (23).

9. The machine tool (100) according to one of the preceding claims, characterized in that said support portion (30) is configured as a machine stand that is disposed on a machine bed (70).

10. The machine tool (100) according to one of the claims 1 to 8, characterized in that said support portion (30) comprises a slide portion (31) that is mounted so as to be horizontally movable, and said slide portion (31) is disposed so as to be mounted on guides on a horizontally movable gantry structure of a gantry machine tool.