Mobile machine tool

Abstract

The invention relates to a mobile machine tool (10) having: (a) a main body (12) by which the machine tool (10) stands on the ground (48); (b) a machine head (14) cantilevered relative to the main body (12); and (c) an end effector (16) guided on the machine head (14) by a positioning system (18). The invention proposes that the machine head (14) is attached to the main body (12) by a mechanically defined frame (24).

Description

Technical Field

[0001] This invention relates to a mobile machine tool comprising: (a) a main body through which the machine tool stands on the ground; (b) a machine head that is cantilevered relative to the main body; and (c) an end effector guided on the machine head by a positioning system. This type of machine tool is known from EP 0 109 201 A2 and can be used, for example, to process the outer hull of a ship. However, such a machine is unsuitable for being driven to large tools such as molds and for rapidly and precisely processing molds on-site due to its insufficient rigidity.

[0002] The present invention also relates to a method for processing workpieces, particularly molds. Background Technology

[0003] To accomplish such a task, while not strictly necessary, it is advantageous for the machine head to have the largest possible working range relative to the body. The working range is the set of all points that the end effector can reach for processing. It is also desirable that the natural frequency of the end effector's vibration be as high as possible, and that the end effector's stiffness relative to the workpiece in terms of deflection be as high as possible.

[0004] However, these ideal properties are in conflict: greater stiffness leads to a higher natural frequency and a smaller workspace. Furthermore, high stiffness and a high natural frequency typically result in complex and therefore expensive machine tools.

[0005] US 2003 / 0 120 377 A1 describes a moving machine tool with an end effector whose position is determined by means of a laser measurement system. This allows for more precise measurement of the end effector's position. A disadvantage of this system is that it exhibits relatively low rigidity, making it unsuitable for applications such as mold processing.

[0006] EP 0 256 853 A1 describes a rigid fixing device having six rods forming a tetrahedral structure. A tool can be attached to the fixing device. The tool is movable, but the fixing device is fixed to increase its rigidity.

[0007] DE 100 44 859 A1 describes a positioning device with four joints arranged in pairs opposite each other on a support. The positioning device is mechanically prestressed only to generate electronic preload. A disadvantage of this system is that it can only move in three degrees of freedom.

[0008] WO O2 / 34461 A2 describes a cantilever machine tool with a six-leg drive. The disadvantage of this machine tool is that it is either rigid or fast, but cannot be both. Summary of the Invention

[0009] The present invention aims to provide an improved mobile machine tool.

[0010] The advantage of this machine tool is that the machine head can be rigidly mounted to the main body.

[0011] If, according to the preferred embodiment, the frame is designed such that the position of the machine head relative to the body can be changed by extending at least one of the rods, the machine head can be adjusted to a predetermined position via the frame. This increases the working range of the machine head.

[0012] By using a mechanically fixed frame, essentially only tensile and / or compressive forces act on its struts, with little or no bending force. This typically produces high stiffness with a small mass. Furthermore, modular and therefore simpler structures are often achievable.

[0013] Within the scope of this specification, "body" should be understood to mean, in particular, the part of the machine tool that stands on the ground.

[0014] The machine head should be understood as a component of the machine tool, relative to which the end effector is guided by a positioning system. The positioning system is part of the machine head. The machine head is mounted on the main body via a frame. Preferably, the distance between the machine head and the main body is at least 50 cm, particularly at least 100 cm, and preferably at least 150 cm.

[0015] The cantilevered design of the machine head relative to the main body should be understood specifically as meaning that the machine head is attached to the main body, so that the main body can be driven to the workpiece, such as the lower tool of a mold, where the end effector can process the surface of the mold block. Advantageously, but not necessarily, no other components of the machine tool are arranged below the machine head.

[0016] A frame that is mechanically determined should be understood in particular to mean that the extension of one strut generates a constraint force on at least one other strut, and especially on at least two other struts. A mechanically determined frame can also be described as a statically uncertain frame. In particular, the uncertainty n is at least n = 2.

[0017] An end effector is referred to as the final link in a kinematic chain. End effectors are preferably units used in welding, printing, milling, polishing, tapping, hardening, or laser processing.

[0018] It is advantageous if the frame forms a hexagonal structure. Specifically, the frame comprises at least six links forming a parallel motion system, meaning that at least one imaginary extension of one of the links generates movement of the machine head in at least one degree of freedom. It should be noted that at least a portion of the length of the frame's struts is extendable; this is advantageous, but not mandatory.

[0019] According to a preferred embodiment, these struts have natural frequencies that differ by at least 3%, particularly at least 5%, and especially preferably at least 10%. This results in sufficiently high damping for the entire frame at all excitation frequencies applied to the end effector.

[0020] Preferably, there are at least three struts, particularly at least four struts, whose pairs of natural frequencies differ by at least 5%, particularly at least 7%, and especially preferably at least 10%. This feature should be understood to mean that for each natural frequency, the following applies: each other natural frequency of the other strut differs from that natural frequency by at least a specified percentage, for example, 5%. This percentage is calculated by dividing the larger natural frequency by the smaller natural frequency.

[0021] It is particularly convenient if the natural frequencies of all pairs of struts differ by at least 3%, especially at least 5%, and particularly preferably at least 7%.

[0022] Preferably, the frame is at least double overset, and in particular at most four times. At least double overset results in exceptionally high rigidity. More than four times mechanical overset results in a relatively complex frame.

[0023] The natural frequency should be understood specifically to refer to the natural frequency with the minimum frequency. This natural frequency can also be called the reference natural frequency.

[0024] According to a preferred embodiment, the strut is designed and arranged such that the stiffness of the end effector relative to the movement in the vertical direction is at least 1.3 times, particularly at least 1.5 times, and especially preferably at least 2 times, the stiffness of the end effector relative to the movement in the lateral direction perpendicular to the aforementioned direction.

[0025] It is particularly advantageous that the stiffness of the end effector relative to the movement in the second lateral direction extending perpendicular to both the vertical and the first lateral direction is at least 1.3 times, especially at least 1.5 times, and particularly preferably at least 2 times, the stiffness of the end effector relative to the movement in the first lateral direction.

[0026] It is advantageous if the end effector has a stiffness of at least 0.5 Newtons per micrometer, particularly at least 1.5 Newtons per micrometer, in all directions. Preferably, the stiffness is at least 3 Newtons per micrometer in at least one direction. Typically, the stiffness is at most 100 Newtons per micrometer, particularly at most 50 Newtons per micrometer, in at least two spatial directions, particularly in all spatial directions.

[0027] Advantageously, at least one of the struts includes a preloading device that allows the strut to be supported on the other struts. If the frame has N struts, it is advantageous for at least (N-6) struts to have preloading devices. In particular, it is feasible and preferred that all struts include preloading devices, or that all but one strut include preloading devices.

[0028] A preloading device should be understood as a device by which the length of each strut can be changed. The strut can thus be supported on other struts. The preloading device can have, for example, a helical actuator. For example, by rotating a component of the preloading device having, for example, internal threads, that component can move relative to another component, which in this example is chosen to have external threads. In particular, such a preloading device has a simple structure. However, for example, the preloading device can also have a cylinder, particularly a hydraulic cylinder.

[0029] Preferably, all struts have a base point and a head point, with the base point attaching them to the body and the head point attaching them to the machine head.

[0030] Advantageously, at least four of the struts are hinged to the body. Preferably, the joints used to hinge each strut to the body have at least two degrees of freedom. This means that the strut can move relative to the body with two degrees of freedom, preferably rotational degrees of freedom. It is particularly advantageous if the joint is a spherical joint. A spherical joint allows for three degrees of freedom of movement: two degrees of freedom relative to rotation and one degree of freedom about the axis of rotation of the spherical joint.

[0031] It is advantageous if the positioning system has at least three axes. In particular, the end effector can move with at least three degrees of freedom relative to the machine head via the positioning system. Preferably, these degrees of freedom are three translational degrees of freedom. In this case, the end effector can move with three degrees of freedom relative to the machine head.

[0032] The positioning system and the frame are preferably redundant with each other. In particular, the end effector is preferably movable either by means of the positioning system or by extending the length of the frame's struts along a predetermined trajectory. This is particularly advantageous if the frame forms a hexagonal drive; however, it is not necessary.

[0033] The mobile machine tool preferably includes a rotating device through which the machine head is mounted, allowing it to rotate relative to the main body, particularly by at least 170°, preferably at least 180°. When processing molds, it is advantageous that both the upper and lower tools can be processed using the same mobile machine tool. For this purpose, it is advantageous that the machine head can be rotated by means of the rotating device, allowing it to process the upper tool after processing the lower tool, while the machine tool's position remains unchanged.

[0034] A particular advantage is that the rotary mechanism is located in the kinematic chain between the machine head and the frame.

[0035] The mobile machine tool preferably has a preloading device, one end of which is attached to the machine head and the other end to the main body, which can support the frame and the rotating device.

[0036] For example, the rotary mechanism may include rolling or sliding bearings, through which the headstock side portion is connected to the body side portion, with a support device passing through the bearings. The tensioned support device does not generate tension between the machine head and the body, meaning that the headstock side portion and the body side portion of the rotary mechanism can support each other.

[0037] The present invention also solves the problem with a mobile machine tool having: (a) a main body on which the machine tool stands upright; (b) a machine head that is cantilevered relative to the main body; and (c) an end effector guided on the machine head by a positioning system, wherein the mobile machine tool includes a rolling base by which the machine tool can be moved. In this case, it is advantageous, but not necessary, to attach the machine head to the main body by a mechanically fixed frame. All the preferred embodiments specified above are also applicable to this invention. All embodiments described below are also applicable to the above-described invention.

[0038] The advantages of this machine tool are that the end effector can handle a fairly large range of workpiece operations. Furthermore, the machine tool can move relative to the ground via a rolling base.

[0039] Machine tools are typically fixed in place to ensure they have the highest possible natural frequency and / or the highest possible rigidity. However, rolling bases have proven advantageous, especially if excessive static and dynamic forces are not generated during workpiece handling and / or the positioning accuracy requirements for the end effector are sufficiently low and / or the acceleration required for the end effector's movement relative to the workpiece is small.

[0040] Within the scope of this specification, the term "rolling base" should be understood as a means by which the movement of a machine tool can be stopped.

[0041] In other words, the motion of the end effector in space, that is, the motion relative to a fixed coordinate system, includes the motion of the machine head caused by the rolling base and the motion of the end effector relative to the machine head caused by the drive positioning system. Here, the concepts of curve and trajectory are equivalent in content; the concept of a curve is used to describe motion in the machine head coordinate system, which involves a coordinate system fixed relative to the machine head. The rolling base allows the machine to move a large distance, meaning the end effector has a large operating range relative to space.

[0042] The method preferably includes step (v): processing the workpiece, particularly by overlay welding, while the end effector moves along the end effector curve.

[0043] Preferably, the machine tool has a control unit configured to automatically execute a method comprising the steps of: (i) detecting a target trajectory of an end effector in space; (ii) driving a rolling base such that the machine tool moves along a rolling base trajectory in space; and driving a positioning system such that the end effector moves relative to the machine head along an end effector curve, thereby causing the end effector to move along the target trajectory in space.

[0044] This is particularly advantageous if the end effector is a weld overlay head. Welding is a process of attaching material to a workpiece. In weld overlay, the positioning accuracy requirements for the end effector are typically only moderate. Therefore, any positioning uncertainty caused by the movement of the machine tool via the rolling base is tolerable.

[0045] According to a preferred embodiment, the rolling base has at least one Mecanum wheel and / or one omnidirectional wheel. This allows the machine tool to move in any desired direction and rotate about a normally vertical axis of rotation.

[0046] A particular advantage is that the rolling base can be positioned in the lowered position, in which at least 80% of the machine tool's weight is transferred to the ground not through the rolling base, but through the lowered surface, after which the main body stands upright on the ground via the lowered surface. The rolling base can also be positioned in the drive position, in which the machine tool can be moved using the rolling base.

[0047] It is particularly advantageous if the machine tool has a tracking interferometer designed to determine the position of the end effector. This end effector position is preferably a position in space, i.e., a position relative to a stationary coordinate system. The end effector position can also be determined in a coordinate system fixed relative to the workpiece. Since the workpiece is fixed, the end effector position is also fixed relative to a coordinate system fixed relative to the workpiece.

[0048] The advantage of a tracking interferometer is that it can more accurately determine the position of the end effector in space and therefore relative to the workpiece. The deviation between the actual position of the end effector and the target position of the end effector specified by the target trajectory can then be compensated for by a positioning system.

[0049] Advantageously, the control unit is configured to automatically execute a method having the steps of: (i) continuously detecting the end effector position in space by means of a tracking interferometer, and (ii) controlling the end effector to the end effector target position according to the target trajectory by means of a positioning system.

[0050] For example, conveniently, there are two control loops in the control unit. The first control loop detects the relative position of the end effector in the machine head coordinate system and controls the axis drive of the positioning unit to move the end effector along the end effector trajectory specified in the machine head coordinate system. This control loop can also be described as a basic control loop.

[0051] If the control unit detects a deviation in the actual position of the end effector based on measurements from the tracking interferometer, the control unit modifies the basic control loop to reduce the deviation between the actual position and the target position described by the target trajectory. For example, this can be done by adjusting the end effector trajectory or adding an offset value to the end effector trajectory.

[0052] The control unit is preferably configured to automatically execute a method having the following steps: (i) driving a rolling base to move the machine tool relative to the ground, (ii) driving the rolling base to place the body on the ground, (iii) determining the end effector position relative to the workpiece, in particular by means of a tracking interferometer, and (iv) processing the workpiece by means of the end effector, in particular by machining.

[0053] Preferably, the workpiece is first processed by overlay welding, while the rolling base moves the machine tool and the motion system also preferably moves the end effector; as described above, the rolling base is then placed in the lowered position and the workpiece is machined, for example, milled and / or polished, especially in the area of ​​overlay welding.

[0054] To increase the inherent frequency of the mobile machine tool while maintaining a sufficiently low weight for easy transport over longer distances, such as over one kilometer, it is advantageous for the machine tool to have a counterweight attached to the main body that can be detached. The counterweight preferably has a weight of at least 300 kg, particularly at least 500 g. Preferably, the counterweight is made primarily of a material with a density exceeding 1 g / cm³, particularly 7.5 g / cm³, and preferably exceeding 10 g / cm³.

[0055] The present invention also includes a method for processing a workpiece using a machine tool according to the invention. This method is preferably designed to include the steps of the method described above. Attached Figure Description

[0056] The invention will be explained in more detail below with reference to the accompanying drawings. The drawings show... Figure 1 Machine tools according to the present invention, and Figure 2 Detailed view of the strut, and Figure 3 According to the present invention Figure 1 Machine tools during workpiece processing. Detailed Implementation

[0057] Figure 1 A machine tool 10 according to the invention is shown, comprising a body 12, a machine 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 axis 20.1 and a second linear axis 20.2 so that the end effector 16 can be positioned in two translational degrees of freedom. The positioning system 18 may also have a rotational unit 22 by means of which the end effector can be moved in rotational degrees of freedom.

[0058] The main body 12 has a frame 24 through which the machine head 14 is connected to the main body 12. The frame 24 includes a plurality of struts 26.i (i = 1, 2, ..., N). The struts 26.i form a mechanically fixed hexagonal structure. According to a preferred embodiment, regardless of other features, the machine tool 10 may have a third linear axis 20.3 through which the height of the frame 24 can be adjusted.

[0059] Each strut 26.i has a base point 28.i, through which the strut is connected to the body. In the present case, the machine tool 12 has a slider 30, to which the struts 26.i are attached via their respective base points 28.i. The slider 30 is attached to the body 12 so that it can move in the vertical direction. To move the slider 30, the machine tool 10 has a driver, which... Figure 1 Not shown in the image.

[0060] Machine tool 10 includes a rolling base 32. In the present case, the rolling base 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, enabling machine tool 10 to move in two translational degrees of freedom and one rotational degree of freedom.

[0061] The machine tool 10 has a control unit 38, which drives the motor 36.i and the positioning system.

[0062] The rotating device 40 is arranged in the kinematic chain between the machine head and the main body 12. Support rods 26.1, 26.2, and 26.3 are attached to the rotating device 40 side of the machine head. Support rods 26.4...26.8 are attached to the main body side portion 42. The machine head 14 can rotate about a rotation axis by means of the rotating device 40, which forms a maximum angle of 20° with the horizontal direction.

[0063] The rolling base 32 has a lifting device 44, which includes a first lifting carriage 46.1 and a second lifting carriage 46.2. These lifting carriages 46.1 and 46.2 can be used to place the main body on the ground 48. Once the upper body 12 is lifted, the machine tool 10 can be moved using the rolling base 32.

[0064] Figure 2 A view of strut 26 is shown, with strut 26.1 as an example. It can be seen that the base plate 28.1 is attached to the slider 30. The head point 50.1 of strut 26.1 is attached to the machine head 14.

[0065] Figure 2 The strut 26.1 is shown attached to the body 12 via a ball joint 52, i.e., by means of a slider 30. The strut 26.1 is also attached to the machine head 14 via a second ball joint 54.1.

[0066] The strut 26.1 has a preloading device 56.1, which in this case is a helical actuator 68. The external thread 60 of the first rod element 62 engages with the internal thread 64 disposed on the second rod element 66. In this case, the internal thread 64 is disposed on the sleeve 68. If the sleeve 68 rotates relative to the first rod element 62, the length L... 26.1 This change causes the strut 26.i of frame 24 to be supported (see...). Figure 1 ).

[0067] Figure 3 A schematic diagram of a machine tool 10 according to the present invention is shown to explain the method according to the invention. First, the rolling base 32 is driven, causing the machine tool 10 to move along the base trajectory T. F Relative to ground motion. Furthermore, the drive positioning system 18 causes the end effector 16 to move along the end effector curve T. E Movement. End effector curve T E It is measured based on a coordinate system fixed relative to the machine head 14. On the other hand, the base carriage trajectory T... F It is measured relative to a fixed coordinate system with a marker R. This produces the target trajectory T. Z Target trajectory TZ It is stored in the digital memory of the control unit 38.

[0068] The mobile machine tool includes a position measuring device 70, currently in the form of a tracking interferometer 70, which may have one, two, or three laser units 72.1, 72.2, or 72.3. Each laser unit emits laser beams 74.1, 74.2, and 74.3 onto a rear reflector 75, respectively. In this way, the end effector position P is measured. ist The control unit 38 detects the position P of the end effector. ist and compare it with the target trajectory T Z The obtained end effector target position P Soll A comparison is made. If the target position of the end effector is from the end effector position P... ist Deviation ， Control unit 38 changes end effector curve T E， Make the end effector position P sit Approaching the target position P of the end effector Soll It should be noted that the tracking interferometer 70 is only practical when the accuracy requirements for machining the workpiece 76 by the end effector 16 are particularly high. For lower accuracy requirements, such as for welding, the tracking interferometer 70 is not necessary. The workpiece 76 is, for example, a forming tool, such as a mold.

[0069] To handle workpiece 76 with high precision, the rolling base 32 is driven, causing it to descend and move to a lowering position. This lowering position places the main body on the lowering surface 78 on the ground 48. Then, the end effector 16 is positioned at end effector position P relative to workpiece 76. ist The determination is made, particularly by means of a tracking interferometer 70. The workpiece 76 is then processed by means of an end effector 16. If the tracking interferometer follows the movement of the end effector and positions the end effector P... ist Constantly controlled to their respective end effector set positions P Soll It is convenient, but not necessary.

[0070] List of reference numerals 10 machine tools 12 main body 14 Machine head 16 End effector 18. Positioning System 20 linear axes 22 Rotating Units 24 Frames 26 struts 28 basis points 30 Slider 32 Rolling base 34. Mecanum Wheel 36 Electric motors 38 Control Unit 40 Rotating device 42 parts 44 Lifting device 46 Lifting Carriage 48 Ground 50 head nods 52 Ball Joint 54 Second ball joint 54 Preloading device 58 Screw Drive 60 external thread 62-bar component 64 Internal Thread 66 Second rod element 68 sleeve 70 Tracking Interferometer 72 laser units 74 laser beams 75 Back reflector 76 workpieces 78 Lowering Surface i, j running flags L 26 Strut length N Number of struts P Soll End effector target position P ist End effector position T F Rolling base track T E End effector curve T Z Target trajectory

Claims

1. A mobile machine tool (10), comprising: (a) The main body (12), the machine tool (10) stands on the ground (48) using it, (b) The machine head (14), which is cantilevered relative to the main body (12), and (c) An end effector (16) guided on the machine head (14) by means of a positioning system (18), Its features are, (d) The machine head (14) is attached to the body (12) by a mechanically fixed frame (24), wherein the frame (24) includes a plurality of struts (26), and the frame (24) is mechanically fixed in that the extension of one strut generates a constraint force on at least another strut, and, (e) The end effector is capable of moving relative to the machine head with at least three degrees of freedom via a positioning system.

2. The mobile machine tool (10) according to claim 1, characterized in that, The natural frequencies of at least two struts (26) differ by at least 7%.

3. The mobile machine tool (10) according to claim 1, characterized in that, The frame (24) is at least mechanically double-fixed.

4. The mobile machine tool (10) according to claim 1, characterized in that, At least one of the struts (26) includes a preloading device (56), and at least one strut (26) is supported on the other struts (26) by the preloading device (56).

5. The mobile machine tool (10) according to claim 4, characterized in that, At least four struts (26) are hinged to the main body (12).

6. The mobile machine tool (10) according to claim 4, characterized in that, At least four struts (26) are hinged to the body (12) by means of ball joints (52).

7. The mobile machine tool (10) according to claim 1, characterized in that, The positioning system (18) includes at least three axes.

8. The mobile machine tool (10) according to claim 1, characterized in that, A rotating device (40) is used to mount the machine head (14) so ​​that it can rotate relative to the main body (12).

9. The mobile machine tool (10) according to claim 1, characterized in that, A rotating device (40) is used to mount the machine head (14) so ​​that it can rotate at least 170° relative to the main body (12).

10. The mobile machine tool (10) according to claim 1, characterized in that, (a) A rolling base (32) through which the machine tool (10) can be moved, and in that, (b) The rolling base (32) has at least one Mecanum wheel (34) and / or one omnidirectional wheel.

11. The mobile machine tool (10) according to claim 10, characterized in that, Control unit (38), which is designed to automatically execute a method having the following steps: (i) Detect the target trajectory (T) of the end effector (16) in space. Z ), (ii) Drive the rolling base (32) so that the machine tool (10) follows the base trajectory (T) in space. F ) movement, and (iii) Drive the positioning system (18) so that the end effector (16) moves relative to the machine head (14) along the end effector curve (T). E The end effector (16) moves along the target trajectory (T) in space, causing the end effector (16) to move. Z )move.

12. The mobile machine tool (10) according to claim 10 or 11, characterized in that, A position measuring device, designed to determine the position (P) of the end effector in space relative to the workpiece (76). ist ) 。 13. The mobile machine tool (10) according to claim 12, characterized in that, The position measuring device is a tracking interferometer (70).

14. The machine tool (10) according to claim 13, characterized in that, The control unit (38) is configured to automatically execute a method having the following steps: (i) The position (P) of the end effector (16) in space is continuously detected by means of a tracking interferometer (70). ist ),as well as (ii) Using a positioning system (18), the position of the end effector (P) is determined. ist Controlled to the target trajectory (T) Z The end effector target position (P) Soll ).

15. The machine tool (10) according to claim 12, characterized in that, The control unit (38) is configured to automatically execute a method having the following steps: (i) Drive the rolling base (32) to move the machine tool (10) relative to the ground (48). (ii) Drive the rolling base (32) to place the main body (12) on the ground (48). (iii) Determine the end effector position (P) of the end effector (16) relative to the workpiece (76). ist ),as well as (iv) The workpiece (76) is processed by means of an end effector (16).

16. The mobile machine tool (10) according to claim 1, characterized in that, (a) At least one counterweight element attached to the body (12) such that it can be detached. (b) wherein the at least one counterweight element has a weight of at least 1.5 g / cm³. 3 The density and / or a mass of at least 300 kg.

17. A method for processing a workpiece (76), comprising the following steps: (i) moving the mobile machine tool according to any one of the preceding claims toward the workpiece (76), and (ii) The end effector (16) moves relative to the machine head by means of the positioning system (18), and thus processes the workpiece (76) by means of the end effector (16).

18. The method according to claim 17, characterized by the following steps: (i) Change the length of at least one strut (26) such that the position of the positioning system (18) changes, and / or (ii) Supporting framework.

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