MOBILE MACHINE TOOL

Abstract

A mobile machine tool includes a main body, a machine bed head, and an end effector. The main body permits the machine tool to stand on the ground. The machine bed head is cantilevered relative to the main body. The end effector is guided on the machine bed head by a positioning system. The machine bed head is attached to the main body by a mechanically overdetermined frame.

Claims

1. A mobile machine tool, comprising: (a) a main body with which the machine tool stands on a ground surface, (b) a machine bed head cantilevered relative to the main body, and (c) an end effector guidable on the machine bed head by a positioning system, (d) wherein the machine bed head is attached to the main body by a mechanically overdetermined frame.

2. The mobile machine tool according to claim 1, wherein the mechanically overdetermined frame comprises at least two struts which differ in their natural frequencies by at least 7%.

3. The mobile machine tool according to claim 1, wherein the mechanically overdetermined frame is at least doubly mechanically overdetermined.

4. The mobile machine tool according to claim 1, wherein the mechanically overdetermined frame comprises at least one strut which comprises a pre-loading device by which the at least one strut is braceable against the other struts.

5. The mobile machine tool according to claim 1 wherein the mechanically overdetermined frame comprises at least four struts articulated on the main body by ball joints.

6. The mobile machine tool according claim 1 wherein the positioning system comprises at least three axles.

7. The mobile machine tool according to claim 1 further comprising a rotation device for mounting the machine bed head such that the machine bed head can be rotated relative to the main body.

8. The mobile machine tool according to claim 7 wherein the machine bed head is rotatable by at least 170°.

9. The mobile machine tool according to claim 1, further comprising a rolling chassis configured for moving the machine tool.

10. The mobile machine tool according to claim 9 wherein the rolling chassis has at least one Mecanum wheel and/or one omni wheel.

11. The mobile machine tool according to claim 9 further comprising a control unit that is designed to automatically carry out a method comprising the steps: (i) detection of a target trajectory of the end effector in space, (ii) driving of a rolling chassis so that the machine tool moves along a chassis trajectory in space, and (iii) driving of the positioning system so that the end effector moves along an end effector curve relative to the machine bed head such that the end effector moves along the target trajectory in space.

12. The mobile machine tool according to claim 11, further comprising a position measurement device designed to determine an end effector position in space relative to a workpiece.

13. The mobile machine tool according to claim 12 wherein the position measurement device is a tracking interferometer.

14. The machine tool according to claim 13 further comprising a control unit configured to automatically execute a method comprising the steps: (i) continuous detection of an end effector position of the end effector in space by the tracking interferometer, and (ii) control of the end effector position to an end effector target position according to the target trajectory by the positioning system.

15. The machine tool according to claim 9 further comprising a control unit configured to automatically execute a method comprising the steps: (i) driving of the rolling chassis so that the machine tool moves relative to the ground, (ii) driving of the rolling chassis so that the main body is placed on the ground, (iii) determination of an end effector position of the end effector relative to a workpiece, and (iv) processing of the work piece by the end effector.

16. The machine tool of claim 15 wherein processing of the work piece of the end effector comprising machining.

17. The mobile machine tool according to claim 1 further comprising at least one weighting element which is attachable to and detachable from the main body, wherein the at least one weighting element has a density of at least 1.5 g/cm.sup.3, and/or a mass of at least 300 kg.

18. The mobile machine tool according to claim 17 wherein the density is at least 7.5 g/cm.sup.3 and/or the mass is at least 500 kg.

19. A method for processing a workpiece, comprising the steps: (i) movement of a mobile machine tool according to claim 1towards the workpiece, and (ii) movement of the end effector by the positioning system for milling of the workpiece by the end effector.

20. The method according to claim 19, further comprising: (i) changing of a length of at least one strut such that a position of the positioning system changes, and/or (ii) bracing of the mechanically overdetermined frame.

Description

DESCRIPTION OF THE DRAWINGS

[0056] In the following, the invention will be explained in more detail by way of the attached figure. It shows

[0057] FIG. 1 a machine tool according to the invention and

[0058] FIG. 2 a detailed view of a strut and

[0059] FIG. 3 the machine tool according to the invention according to FIG. 1 during the processing of a workpiece.

DETAILED DESCRIPTION

[0060] FIG. 1 depicts a machine tool 10 according to the invention which comprises a main body 12, a machine bed head 14 and an end effector 16. The end effector 16 can be positioned by means of a positioning system 18. In the present case, the positioning system is formed by a linear axle 20.1 and a second linear axle 20.2 so that the end effector 16 can be positioned in two translation degrees of freedom. The positioning system 18 may also feature a rotation unit 22 by means of which the end effector can be moved in a rotational degree of freedom.

[0061] The main body 12 has a frame 24 by means of which the machine bed head 14 is connected to the main body 12. The frame 24 comprises several struts 26.i (i=1, 2, . . . , N). The struts 26.i form a mechanically overdetermined hexapod structure. Irrespective of the other properties, according to a preferred embodiment, the machine tool 10 may have a third linear axle 20.3 by means of which the height of the frame 24 can be adjusted.

[0062] Each strut 26.i has a base point 28.i by means of which it is attached to the main body. In the present case, the machine tool 12 features a slide 30 to which the struts 26.i are attached by their respective base points 28.i. The slide 30 is attached to the main body 12 such that it can be displaced in the vertical direction. To move the slide 30, the machine tool 10 has a drive, which is not depicted in FIG. 1.

[0063] The machine tool 10 comprises a rolling chassis 32. In the present case, the rolling chassis 4 has Mecanum wheels 34.j (j=1, 2, 3, 4). Each Mecanum wheel 34.j is driven individually by means of an electric motor 36.j so that the machine tool 10 can be moved in two translation degrees of freedom as well as one rotational degree of freedom.

[0064] The machine tool 10 features a control unit 38 by means of which the electric motors 36.i and the positioning system are driven.

[0065] A rotation device 40 is arranged in the kinematic chain between the machine bed head and the main body 12. The struts 26.1, 26.2, 26.3 are attached on the machine bed head side of the rotation device 40. The struts 26.4 . . . , 26.8 are attached to a main body side part 42. The machine bed head 14 can be rotated by means of the rotation device 40 about a rotational axis which forms an angle of at most 20° with the horizontal.

[0066] The rolling chassis 32 features a lifting device 44 which comprises a first lifting carriage 46.1 and a second lifting carriage 46.2. These lifting carriages 46.1, 46.2 can be used to set the main body on the ground 48. Once the upper body 12 has been lifted, the machine tool 10 can be moved using the rolling chassis 32.

[0067] FIG. 2 depicts a view of a strut 26, using strut 26.1 as an example. It can be seen that the floor 28.1 is attached to the slide 30. A head point 50.1 of the strut 26.1 is attached to the machine bed head 14.

[0068] FIG. 2 shows that the strut 26.1 is attached to the main body 12, namely by means of the slide 30, via a ball joint 52. The strut 26.1 is also attached to the machine bed head 14 via a second ball joint 54.1.

[0069] The strut 26.1 has a pre-loading device 56.1, which is a screw drive 68 in the present case. An outer thread 60 of a first rod element 62 meshes with an inner thread 64 configured on a second rod element 66. In the present case, the inner thread 64 is configured on a sleeve 68. If the sleeve 68 is rotated relative to the first rod element 62, a length L.sub.26.1 changes. This causes the struts 26.i of the frame 24 to brace (cf. FIG. 1).

[0070] FIG. 3 shows a schematic view of the machine tool 10 according to the invention for explaining a method according to the invention. The rolling chassis 32 is first driven in such a way that the machine tool 10 moves relative to the ground along a chassis trajectory T.sub.F. In addition, the positioning system 18 is driven in such a way that the end effector 16 moves along an end effector curve T.sub.E. The end effector curve T.sub.E is measured in terms of a coordinate system which is stationary relative to the machine bed head 14. The chassis trajectory T.sub.F, on the other hand, is measured relative to a stationary coordinated system whose coordinates carry the index R. This results in a target trajectory T.sub.Z, which is stored in a digital memory of the control unit 38.

[0071] The mobile machine tool comprises a position measurement device 70, in the present case in the form of a tracking interferometer 70, which can feature one, two or three laser units 72.1, 72.2 or 72.3. Each laser unit emits a laser beam 74.1, 74.2 and 74.3 respectively onto a retroreflector 75. In this way, an end effector position P.sub.ist is measured. The control unit 38 detects the end effector position P.sub.ist and compares this with an end effector target position P.sub.Soll resulting from the target trajectory T.sub.Z. If this end effector target position deviates from the end effector position P.sub.ist, the control unit 38 changes the end effector curve T.sub.E such that the end effector position P.sub.ist approaches the end effector target position P.sub.Soll. It should be noted that the tracking interferometer 70 is only practical if the requirements concerning accuracy with which the end effector 16 is to process a workpiece 76 are particularly high. For lower accuracy requirements, for example with build-up welding, a tracking interferometer 70 is unnecessary. The workpiece 76 is, for example, a forming tool, such as a die.

[0072] To process the workpiece 76 with a high degree of accuracy, the rolling chassis 32 is driven in such a way that it sinks and moves into a set-down position. This set-down position sets the main body on a set-down surface 78 on the ground 48. The end effector position P.sub.ist of the end effector 16 relative to the workpiece 76 is then determined, in particular by means of the tracking interferometer 70. The workpiece 76 is subsequently processed by means of the end effector 16. It is convenient, but not essential, if the tracking interferometer follows the movement of the end effector and its end effector position P.sub.ist is constantly controlled to its respective end effector set position P.sub.Soll.

REFERENCE LIST

[0073] 10 machine tool
12 main body
14 machine bed head
16 end effector
18 positioning system
20 linear axle
22 rotation unit
24 frame
26 strut
28 base point
30 slide
32 rolling chassis
34 Mecanum wheel
36 electric motor
38 control unit
40 rotation device
42 part
44 lifting device
46 lifting carriage
48 ground
50 head point
52 ball joint
54 second ball joint
54 pre-loading device
58 screw drive
60 outer thread
62 rod element
64 inner thread
66 second rod element
68 sleeve
70 tracking interferometer
72 laser unit
74 laser beam
75 retroreflector
76 workpiece
78 set-down surface
i, j running index
L.sub.26 length of a strut
N number of struts
P.sub.Soll end effector target position
P.sub.ist end effector position
T.sub.F rolling chassis trajectory
T.sub.E end effector curve
T.sub.Z target trajectory