MACHINE TOOL

Abstract

The invention relates to a machine tool (10) with (a) a tool head frame (16), (b) a tool head (18), (c) an axis unit (20) that is fixed to the tool head frame (16) and by means of which the tool head (18) can be positioned in a predefinable position, and (d) a movement device (28) for moving the tool head frame (16). The invention proposes that the movement device (28) comprises (e) a machine frame (12) and (f) a multipod drive (14) which (i) has at least three drive elements (24), (ii) is arranged in the flux of force between the machine frame (12) and the machine tool frame (16), and (iii) has at least two supporting elements (26), which can be brought into a locked state, (iv) wherein the multipod drive(14) is mechanically overdetermined by the supporting elements (26) and the drive elements (24).

Claims

1. A machine tool, comprising: (a) a tool head frame, (b) a tool head, (c) an axis unit fixed to the tool head frame configured for positioning the tool head in a predefinable position, and (d) a movement device for moving the tool head frame (16), wherein the movement device comprises (e) a machine frame, and (f) a multipod drive which (i) has at least three drive elements, (ii) is arranged in a flux of force between the machine frame and the tool head frame, and (iii) comprises at least two supporting elements, which are selectively lockable in a locked state, (iv) wherein the multipod drive is mechanically overdetermined by the at least two supporting elements and the at least three drive elements.

2. The machine tool according to claim 1, wherein (a) the movement device is designed to move the tool head frame, (b) the multipod drive is at least doubly mechanically overdetermined by the at least two supporting elements and the at least three drive elements, and (c) the multipod drive is designed to move the tool head frame in exactly three, exactly four, exactly five or exactly six degrees of freedom.

3. The machine tool according to claim 1, wherein (a) the multipod drive has at least four, supporting elements, and (b) the tool head frame is configured such that it cannot be moved relative to the machine frame when the at least four supporting elements are in a locked state.

4. The machine tool according to claim 1, further comprising (a) a drive element locking device for locking the at least three drive elements relative to the machine frame, and/or (b) a supporting element locking device for locking the at least two supporting elements relative to the machine frame, (c) wherein the tool head frame cannot be moved by movement device when either or both the drive element locking device or the supporting element locking device are locked.

5. The machine tool according to claim 4 wherein (a) the at least three drive elements each feature a drive element drive for moving the respective drive element, and/or (b) the at least two supporting elements each feature a supporting element drive for moving the respective supporting element.

6. The machine tool according to claim 1, wherein (ix) the movement device comprises a first rail, a first slide which is guided on the first rail, and at least a second slide which is guided on the first rail, (x) a first drive element of the at least three drive elements has a base point fixed to the first slide, (xi) a second drive element of the at least three drive elements has a base point fixed to the second slide, (xii) the first drive element has a drive designed to move the first slide along the first rail, and (xiii) the second drive element has a drive designed to move the second slide along the first rail.

7. The machine tool according to claim 6, wherein (xiv) the multipod drive comprises a first auxiliary slide which is linearly guided on the first slide, and (xv) a first supporting element of the at least two supporting elements has a base point fixed to the auxiliary first slide.

8. The machine tool according to claim 7, further comprising (xvi) a supporting element locking device configured to fix the first auxiliary slide relative to a first auxiliary rail.

9. The machine tool according to claim 5 further comprising a control system that is designed to automatically carry out a method comprising: (i) driving the drive element drive of each of the at least three drive elements so that the tool head moves along a predefined low precision trajectory, (ii) driving the tool head or a first tool that is fixed to the tool head, so that it machines a workpiece without moving the axis unit, (iii) driving the drive element locking device and the support element locking device so that they lock the at least three drive elements and the at least two supporting elements, and (iv) driving the axis unit so that the tool head or the first tool or a second tool which is fixed to the tool head, is moved along a predefined high precision trajectory.

10. The machine tool according to claim 9, wherein the control system is configured to automatically carry out a method comprising: after driving the drive element locking device and the support element locking so that they lock the at least three drive elements and the at least two supporting elements, driving at least a part or all of the at least three drive element drives so that the at least three drive elements are braced against the at least two supporting elements.

11. The machine tool according to claim 9, further comprising: (a) a measuring device which is designed to automatically set out a metrological frame, and wherein the metrological frame is configured to determine a position of the tool head relative to the measuring device, (b) wherein the control system is configured to automatically carry out a method comprising: (α) after step (iii), measuring a position of the machine frame relative to the measuring device, (β) calculating a high precision trajectory in a machine coordinate system from a predetermined target trajectory in measuring frame coordinates of the measurement device, and (χ) moving the tool head or the tool along the high precision trajectory by the axis unit so that the workpiece is machined.

12. The machine tool according to claim 11, wherein the measuring device comprises a laser tracker.

13. A machining assembly, comprising: a machine tool according to claim 6, and a workpiece, wherein the workpiece is fixed relative to the first rail.

14. A method for machining a workpiece comprising the (i) fixing a machine tool according to claim 1 and a workpiece relative to each other, (ii) bracing the multipod drive with the at least two supporting elements, thereby increasing a rigidity of the tool head relative to the workpiece, and (iii) machining the workpiece 40 by moving the tool head of the axis unit.

15. A method for machining a workpiece according to claim 14, comprising: (i) after machining the workpiece, relaxing the multipod drive , (ii) moving the tool head frame relative to the workpiece by of the movement device, (iii) bracing the multipod drive with the at least two supporting elements, thereby increasing a rigidity of the tool head relative to the workpiece, and (iv) machining the workpiece by moving the tool head with the axis unit.

Description

[0062] FIG. 1 depicts a machine tool 10 according to the invention which comprises a machine frame 12, a multipod drive 14 and a tool head frame 16. A tool head 18 is fixed to the tool head frame 16 by means of an axis unit 20. The axis unit 20 is schematically shown as a partial image.

[0063] In the present case, the axis unit 20 comprises three drive axes 22.1, 22.2, 22.3, by means of which the tool head 18 can be positioned in three spatial directions. In the present case, the tool head has a milling head that holds a schematically depicted tool 19 in the form of a milling tool.

[0064] The multipod drive 14 features four drive elements 24.1, 24.2, 24.3, 24.4, by means of which the tool head frame 16 can be positioned in the three spatial directions. The multipod drive 14 also features four supporting elements 26.1, 26.2, 26.3, 26.4. Since there are four drive elements, the multipod drive 14 is mechanically overdetermined several times by the four supporting elements. In other words, all four supporting elements 26 would have to be removed for the multipod drive 14 to no longer be mechanically overdetermined.

[0065] The multipod drive 14, together with the machine frame 12, forms part of a movement device 28. The movement device 28 has a first rail 30a and a second rail 30b. The movement device 28 also comprises four slides 32.i (i=1, 2, 3, 4). A first slide 32.1 and a second slide 32.2 are guided on the first rail 30a. A third slide 32.3 and a fourth slide 32.4 are guided on the second rail 30b. A drive element base point 34.1 of each of the drive elements 24.i is fixed to each slide 32.i, in the present case by means of a ball joint in each case. Each slide 32.i can be moved by means of a drive element drive 36.i. In the present case, the drive elements 36.i are ball screw drives, each of which comprises a threaded rod on which the respective slide 32.i moves.

[0066] The multipod drive 14 features auxiliary slides 38.i, which are fixed to the respective slide 32.i in a linearly guided manner. A supporting element base point 40.i is fixed to each auxiliary rail 38.i. This can be seen particularly clearly in the segment at the bottom left.

[0067] Each auxiliary rail 38 features a supporting element locking device by means of which a movement of the respective auxiliary slide 38.i relative to the corresponding slide 32.i can be prevented. It is possible, but generally not essential, that the auxiliary slides 38.i can be moved by means of a supporting element drive 36.

[0068] The machine tool 10 comprises a schematically depicted control system 42 that is connected to all drives for driving purposes.

[0069] FIG. 2 depicts the machine tool 10, the slides 32.i of which have changed their position. This has caused the tool head frame 16 to be displaced relative to a workpiece 44.

[0070] FIG. 2 also shows that the machine tool 10 comprises a measuring device 46, which in the present case features three laser trackers 48.1, 48.2, 48.3. The laser trackers 48.j (j=1, 2, 3) aim a respective laser beam 50.j at a retroreflector 52 attached to the tool head 18. As a result, the position of the tool head 18 is known at any time with a high degree of accuracy with respect to a machine coordinate system K.

[0071] For the purposes of machining with a lower degree of precision, the control system 42 drives the drive element drives 36.i in such a way that the tool head 18 moves on a predefined low precision trajectory T.sub.M. This may relate, for example, to a build-up welding process, in which case the tool head 18 is a build-up welding head. If the tool head 18 is to be moved with a high degree of positioning accuracy or a higher degree of rigidity is required, the tool head frame 16 is pre-positioned by driving the drive element drives 36.i accordingly. The supporting elements 26.i are then locked by means of a supporting element locking device 54 (FIG. 3).

[0072] For example, this is a clamping device, which can be designed to clamp hydraulically, pneumatically or mechanically. FIG. 3 shows that the supporting element locking device 54 can be designed as a screw, by means of which the respective auxiliary slide 38.i is fixed relative to the respective slide 32.i. The supporting element locking device 54 can, as in the case of the screw, be locked by hand. Alternatively, the supporting element locking device 54 can also be driven by a motor 56, depicted here schematically in dashed lines.

[0073] Subsequently, at least one drive element drive 36, and in particular all drive element drives 36.i, are moved so as to apply a tension to the supporting elements 26.i. The drive elements 24.i are then locked by means of a drive element locking device 58. This drive element locking device 58 is formed, for example, by the drive element drives 36 or a part thereof. For example, the drive element drives 36 are self-locking drives, such as ball screw drives.

[0074] FIG. 3b an example of an alternative drive element locking device 58 in the form of a screw by means of which the slide 32.1 is braced against the rail 30a. The drive element locking device 58 can, as in the case of the screw, be locked by hand.

[0075] Alternatively, the drive element locking device 58 can also be driven by a motor 60, depicted here schematically in dashed lines. Further embodiment options for the supporting element locking device 54 and the drive element locking device 58 are described above.

[0076] This increases rigidity, as the tool head frame 16 is arranged relative to the machine frame 12. In other words, a predefined force acting on the tool head 18 causes a lower deflection than when the supporting elements are not locked and braced.

[0077] The position of the tool head 18 is then determined with a high degree of accuracy by means of the measuring device 46. Subsequently, a high-precision trajectory T.sub.H, along which the tool head is to move and which is specified in the coordinate system K of the tool, is converted to a machine coordinate system. Based on the trajectory obtained in this way, the axis unit 20 is controlled so that the tool head 18 moves along the specified trajectory.

REFERENCE LIST

[0078] 10 machine tool

[0079] 12 machine frame

[0080] 14 multipod drive

[0081] 16 tool head frame

[0082] 18 tool head

[0083] 19 tool

[0084] 20 drive unit

[0085] 22 drive axis

[0086] 24 drive element

[0087] 26 supporting element

[0088] 28 movement device

[0089] 30 rail

[0090] 32 slide

[0091] 34 drive element base point

[0092] 36 drive element drive

[0093] 38 auxiliary slide

[0094] 40 supporting element base point

[0095] 42 control system

[0096] 44 workpiece

[0097] 46 measuring device

[0098] 48 laser tracker

[0099] 50 laser beam

[0100] 52 retroreflector

[0101] 54 supporting element locking device

[0102] 56 motor

[0103] 58 drive element locking device

[0104] i running index

[0105] j running index

[0106] T.sub.M low precision trajectory

[0107] T.sub.H high precision trajectory