DE202012012817U1 - Multi-axis robot for laser machining of workpieces - Google Patents

Abstract

Multi-axis robot (1) for laser processing of workpieces with a first hand axis (12), which has a first axis of rotation (11) and a second hand axis (14) oriented perpendicular thereto, which has a second axis of rotation (13) and one on the second hand axis ( 14) attached laser cutting head (2) rotatable about the second axis of rotation (13) with focusing optics (23) having an optical axis (24) for focusing a laser beam (31) guided through the laser cutting head (2) onto a workpiece (4), characterized in that a distance sensor (22) is provided on the laser cutting head (2) and a linear drive (25) is present which is connected to the distance sensor (22) so that the focusing optics (23) can be displaced along the optical axis (24) is to keep the focal point (34) on the workpiece (4) even when the distance between the laser cutting head (2) and the workpiece (4) changes.

Description

The invention relates to a multi-axis robot for laser machining of workpieces, in particular a multi-axis robot for guiding a tool with which a focused laser beam is directed onto a workpiece.

Since large workpieces can be moved poorly in a two- or three-dimensional machining, it makes sense to realize the relative movement between the workpiece and the tool by a movement of the tool. Due to the size of the workpieces, portal machines or multi-axis robots are often used to carry out this movement.

For programming a tool path and a corresponding orientation of the tool relative to the workpiece, a so-called Tool Center Point (TCP) is defined with respect to the tool, with which the action point of the tool is defined. At this point of action, the tool is guided along the programmed tool path over the workpiece. For example, the tip of a welding electrode, a cutting edge or a point (eg the focal point) in a laser beam can be defined as the point of action. This point of action is also used as a reorientation point around which the tool is aligned in three-dimensional space by a multi-axis robot or by another movement system relative to the workpiece.

5-axis or 6-axis robots are often used for the three-dimensional movement in space, in which the first three axes counted by the positioning base of the robot are referred to as main axes and the two or three axes following in the direction of the workpiece are referred to as manual or secondary axes , To achieve a high mechanical stability, the main axes are usually very stable and thus executed solid. As a result of the large moving masses and the correspondingly dimensioned bearings of the main axes, the movement of the robot arms about these axes produces a large mass moment of inertia and increased frictional resistance, which must be overcome with correspondingly dimensioned drives. For this reason, only a relatively low positioning accuracy can be achieved with a limited machining speed with the main axes.

On workpieces that have a large number of very small contours to be machined, the tool movement is associated with very frequent changes in direction. As a result, the robot performs many accelerated movements, resulting in a significant increase in processing time. In order nevertheless to produce small contours in an economically acceptable machining time with high positioning accuracy, solutions are already known with which these disadvantages can be reduced. For this purpose, methods are proposed in which the number of robot axes required for moving the tool is reduced to a minimum.

In one in the patent US Pat. No. 7,209,802 B2 disclosed methods multi-axis robots are used for guiding cutting tools with which small contours are produced in a flat workpiece. To achieve a higher positioning accuracy of the cutting tool and a dimensional accuracy of the small contours, it is proposed to use only the hand axes closest to the workpiece for guiding the cutting tool and to leave all other robot axes stationary.

By cutting a circular hole it is described that the cutting tool is first positioned by using all the robot axes against the contour of the hole. The cutting tool is aligned as perpendicular as possible to the workpiece surface, just above the center of the hole. To create the hole, all main axes of the robot are fixed in this position. Subsequently, the cutting movement is carried out exclusively with the hand axes. For this purpose, the cutting tool is deflected along the hole radius around the center of the hole, in which case the reorientation point of the cutting tool does not lie, as described above, at the action point (TCP) of the tool, but is displaced onto the hand axes. A correspondingly shifted reorientation point then makes possible a pendulum movement executed via at least two hand axes, which can take place by a deflection of the cutting tool about the reorientation point.

Due to the pendulum movement around the reorientation point, the distance between the point of action of the tool and the workpiece surface changes when the tool is deflected. As the size of a contour increases, so does the distance. Since only circular holes in flat workpieces are produced here, the distance, after the deflection of the tool from the center of the hole to the hole radius, remains constant when cutting along the hole radius. For this reason, it is possible to set the distance already when positioning the tool with the main axes so that the tool has the desired distance from the contour after the deflection to the hole radius.

When editing contours that do not have a circular course, this can Changing the distance can not be easily compensated. Furthermore, it should be noted that the distance can reach particularly high values if instead of flat workpieces uneven workpieces are processed with Höhenuterschieden or if there is a distance between the tool and the other of the two hand axes when recording the tool on one of the at least two hand axes or if the workpiece shape or the design of the multi-axis robot does not allow the tool to be positioned vertically above the center of the contour before machining.

For cutting processes, such. B. in the US Pat. No. 7,209,802 B2 described water jet cutting, this change in distance is tolerable to a certain extent. In a cutting tool with a much more focused working beam, whose cut quality is highly dependent on the focus position, a processing by this method would no longer be possible or only limited to very small structures.

The invention has for its object to provide a multi-axis robot for laser machining of workpieces, with which it is possible, regardless of a workpiece shape and shape of the contour to introduce small contours with high speed and accuracy in a workpiece.

According to the invention the object is achieved by a multi-axis robot for laser machining of workpieces having a first axis of rotation having a first hand axis and a second axis of rotation and oriented perpendicular to the first hand axis second hand axis. On the second hand axis a rotatable about the second axis of rotation laser cutting head is fixed with an optical axis having focusing optics. With the focusing optics, a guided by the laser cutting head laser beam is focused on a workpiece, wherein the focusing optics along the optical axis is displaceable to keep the focal point even with changes in distance of the laser cutting head to the workpiece on the workpiece. For this purpose, a distance sensor is provided on the laser cutting head and a linear drive communicating with the distance sensor is present.

Advantageously, the laser cutting head has a cutting tube movable along the optical axis for receiving the focusing optics in order to keep the laser cutting head at a constant distance from the workpiece.

For this purpose, the movable cutting tube expediently has an indirect connection to the laser cutting head which is produced via the linear drive.

In an advantageous embodiment, the distance sensor is a non-contact distance sensor for capacitive distance measurement.

For this purpose, the distance sensor is preferably arranged directly opposite the workpiece, on the movable cutting tube.

The connection between distance sensor and linear drive is advantageously carried out via a control unit.

For the evaluation of the measured values provided by the distance sensor and for the corresponding control of the linear drive, the control unit particularly advantageously has a data processing speed in real time.

In a special embodiment, the linear drive has a travel of +/- 30 mm about a center position.

The invention will be explained in more detail with reference to embodiments. In the accompanying drawings show:

1 the basic structure of a first embodiment of the multi-axis robot,

2 a second embodiment of the multi-axis robot and

3 Examples of possible changes in distance due to deflection of a cutting head by the multi-axis robot.

According to 1 has the multi-axis robot 1 a first rotatable hand axis 12 with a first axis of rotation 11 and one at right angles oriented and around the first axis of rotation 11 rotatable second hand axis 14 with a second axis of rotation 13 on. About the first hand axis 12 is the connection to the basis of the multi-axis robot 1 produced. At the second hand axis 14 is one around the second axis of rotation 13 rotatable laser cutting head 2 attached. The laser cutting head 2 is thus about the two axes of rotation 11 and 13 rotatable on the multi-axis robot 1 added.

The laser cutting head 2 has a focusing optics 23 with an optical axis 24 on. Along the optical axis 24 becomes a laser beam 31 through the laser cutting head 2 led, with the focusing optics 23 in a focal point 34 on a workpiece 4 is focused.

Furthermore, the laser cutting head 2 a distance sensor 22 and a linear drive 25 on. With the distance sensor 22 is the distance between laser cutting head 2 and the workpiece 4 determined. The linear drive 25 is for moving the focusing optics 23 intended. At one with the distance sensor 22 detected change in distance between laser cutting head 2 and workpiece 4 becomes the focusing optics 23 with the linear drive 25 along the optical axis 24 shifted so that the focus point 34 continue on the workpiece 4 is held.

The focusing optics 23 is in a cutting tube 21 added. The shift of the focusing optics 23 takes place indirectly by a movement of the cutting tube 21 , This is the cutting tube 21 along the optical axis 24 movable in the laser cutting head 2 added. The cutting tube 21 is a hollow cylinder attached to the workpiece 4 pointing end has a conical tip. At this end of the hollow cylinder is, as in 1 shown, the focusing optics 23 inside the cutting tube 21 attached. The tip of the cutting tube 21 has a small opening from which the focused laser beam 31 can escape. The cutting tube 21 is symmetrical to the optical axis 24 and on the optical axis 24 displaceable in the laser cutting head 2 added.

At this point it should be noted that the focusing optics 23 even without the cutting tube 21 displaceable on the laser cutting head 2 can be included. Any suitable optics holder can be used for this purpose.

To move the cutting tube 21 is at a laser exit side of the laser cutting head 2 the linear drive 25 arranged. It is fixed on one side with the laser cutting head 2 connected and carries on the other side of the sliding cutting tube 21 , With the linear drive 25 can the cutting tube 21 together with the focusing optics 23 along the optical axis 24 be moved. For controlling the linear drive 25 becomes a control unit 5 used with which the linear actuator 25 connected is.

The linear drive 25 consists of a linear guide, which is moved and positioned with an electromotive drive. As drive but also piezoelectric, hydraulic, pneumatic or other suitable drives can be used. The adjustment range of the linear drive 25 can be adapted to the intended application and, starting from a center position, should be at least +/- 15 mm and advantageously +/- 30 mm.

The one from a laser beam source 3 outgoing, collimated laser beam 31 becomes coaxial with the optical axis 24 through the laser cutting head 2 on the workpiece 4 directed. For this he is first along the second axis of rotation 13 over one through the second hand axis 14 passing laser beam injection 32 in the laser cutting head 2 coupled. The deflection of the laser beam 31 from the second axis of rotation 13 on the optical axis 24 takes place within the second hand axis 14 with a 90 ° mirror 33 , which is at the intersection between the second axis of rotation 13 and the optical axis 24 is arranged. The laser beam injection 32 can in principle be anywhere, as long as the laser beam 31 ultimately along the optical axis 24 through the laser cutting head 2 on the workpiece 4 can be directed.

The collimated laser beam 31 is using the focusing optics 23 in the focus point 34 focused. For simplicity, this description assumes that the focus point 34 outside the cutting tube 21 , on the surface of the workpiece 4 is arranged horizontally. The focus point 34 but it can also be inside the workpiece 4 or inside the cutting tube 21 be arranged. Based on the focus point 34 can the laser cutting head 2 opposite the workpiece 4 be aligned.

According to the device disclosed in the prior art, the laser cutting head 2 before machining one into the workpiece 4 to be introduced contour 41 opposite the workpiece 4 aligned. By a movement of the laser cutting head 2 The focus point will first be on all robot axes 34 over a focal point 42 the contour 41 positioned, with focus here 42 the geometric center of the contour 41 on the surface of the workpiece 4 is meant. In 1 is the aligned position of the laser cutting head 2 opposite the workpiece 4 shown. The workpiece 4 is uneven in this case, with the contour to be introduced 41 extends over the unevenness.

The movement of the laser cutting head 2 takes place after the alignment mainly around the two axes of rotation 11 and 13 , where the focus point 34 along the contour to be introduced 41 is moved. This is the laser cutting head 2 around a fictitious, from the focal point 34 on the second axis of rotation 13 displaced reorientation point (not shown in the figures) deflected. The shifted reorientation point is at least close to the intersection of the optical axis 24 and second axis of rotation 13 , With appropriate positioning of the shifted reorientation point exactly at the intersection of the first and second axis of rotation 11 and 13 , it is also possible the movement of the laser cutting head 2 exclusively around the two axes of rotation 11 and 13 perform. As already described in the prior art, with the deflection of the laser cutting head 2 The shift in reorientation has seen an increase in Machining speed and a higher positioning accuracy achieved.

The deflection around the reorientation point is any movement of the laser cutting head 2 with a change in distance between the focus point 34 and workpiece 4 connected. In order to achieve the high quality achievable in laser cutting at the cutting edges of the contour 41 To achieve this, it is necessary the location of the focal point 34 to the workpiece 4 to comply exactly. According to the occurring changes in distance to the sliding cutting tube 21 together with the focusing optics 23 by means of the linear drive 25 tracked.

At an in 1 shown arrangement of the first hand axis 12 and the second hand axis 14 the distance changes can be particularly large. The laser cutting head 2 is here with the optical axis 24 offset to the first axis of rotation 11 on the second hand axis 14 mounted so that between the first axis of rotation 11 and the optical axis 24 an axial distance 15 consists. The value of the center distance 15 corresponds to the distance between the intersection of the first axis of rotation 11 with the second axis of rotation 13 and the intersection of the second axis of rotation 13 with the optical axis 24 , During a rotation of the laser cutting head 2 around the first axis of rotation 11 becomes the rotation angle dependent change in distance between laser cutting head 2 and workpiece 4 through the center distance 15 strengthened. The larger the center distance 15 is, the greater are the changes in the distance related to a comparable rotation angle. An additional contribution to the change in distance results from the unevenness of the workpiece 4 ,

Another version of the multi-axis robot 1 is in 2 shown. The picture of the laser cutting head 2 on the second hand axis 14 takes place here without the center distance 15 between the optical axis 24 and the first axis of rotation 11 , The intersection of the first axis of rotation 11 with the second axis of rotation 13 and the intersection of the optical axis 24 with the second axis of rotation 13 coincide in one point. This point is also the reorientation point. For a deflection movement around the reorientation point, the change in distance is between the focus point 34 and workpiece 4 much smaller than in the first embodiment ( 1 ).

To determine the changes in distance between cutting tube 21 and workpiece 4 becomes the distance sensor 22 used. He works on a capacitive measuring principle and is on the workpiece 4 immediately opposite tip of the cutting tube 21 appropriate. The distance sensor 22 misses the distance continuously. Due to the capacitive measuring principle, the distance sensor 22 only when machining capacitively effective workpieces 4 , in particular of metals, of composite materials containing metal or workpieces 4 be used with metallic coating.

In addition to the capacitive distance sensor 22 It is also possible to use sensors with different principles of action, as long as they allow non-contact and fast distance measurement.

For evaluation of the distance measurement is the distance sensor 22 with the control unit 5 connected. The control unit 5 continuously records the measured values of the distance sensor 22 and controls the movement of the linear drive according to the determined measured values 25 , The compensation of distance changes takes place in real time. Will at a deflection of the laser cutting head 2 found an increase in the distance, causes the control unit 5 an adjustment of the cutting tube 21 in the direction of the workpiece 4 , If a reduction of the distance is detected, the adjustment takes place in the opposite direction.

Look at the in 3a to 3d Illustrated, exemplary arrangements, the function of the multi-axis robot 1 be explained in more detail. In the figures, the deflection of the laser cutting head 2 in each case represented by the reorientation point only in one of the deflection directions. The reorientation point is exactly at the intersection of the first axis of rotation 11 with the second axis of rotation 13 where the first axis of rotation 11 oriented perpendicular to the plane of representation. To the contour 41 At the same time, the deflection about the second axis of rotation takes place at the same time 13 , Due to the two-dimensional representation, this movement can be in 3a to 3d but not shown.

The in 3a shown construction corresponds to the structure of the first embodiment ( 1 ). The laser cutting head 2 is here with the center distance 15 between optical axis 24 and first axis of rotation 11 on the second hand axis 14 assembled. In an initial position (solid line representation) is the laser cutting head 2 with the optical axis 24 on the focus 42 the contour 41 and perpendicular to the workpiece 4 aligned. The cutting tube 21 is in this position in the center position, with the focus point 34 to the surface of the workpiece 4 is aligned. The bilateral deflection movement takes place around the on the first axis of rotation 11 and second axis of rotation 13 lying reorientation point. At the deflection of the laser cutting head 2 to the right (dotted line representation), the distance between the laser cutting head is reduced 2 and the workpiece 4 , To the distance between the focus point 34 and surface of the workpiece 4 To keep constant, the cutting tube 21 with the linear drive 25 in the laser cutting head 2 moved into it. The distance becomes continuous with the distance sensor 22 captured and the cutting tube 21 over the linear drive 25 from the control unit 5 readjusted. When deflecting to the left, the distance increases, so that the cutting tube 21 with the linear drive 25 from the laser cutting head 2 is pushed out.

The in 3b shown construction corresponds to the structure of the second embodiment ( 2 ). The laser cutting head 2 is here without the center distance 15 between optical axis 24 and first axis of rotation 11 at the second axis of rotation 14 assembled. In the home position (solid line representation) is the laser cutting head 2 with the optical axis 24 perpendicular to the workpiece 4 on the focus 42 the symmetrical contour in this view 41 aligned. In a deflection movement (dotted line representation) around that on the first axis of rotation 11 and second axis of rotation 13 lying reorientation point decreases the distance between the laser cutting head 2 and the workpiece 4 in both directions too. To maintain the distance between the focus point 34 and surface of the workpiece 4 becomes the cutting tube 21 with the linear drive 25 from the laser cutting head 2 pushed out.

In the in 3c The example shown is the same structure as in 3b used. At the in 3c illustrated shape of the workpiece 4 it is not possible to use the laser cutting head 2 with the optical axis 24 perpendicular to the surface of the workpiece 4 and on the center of gravity 42 the contour 41 align. In the home position (solid line representation) is the laser cutting head 2 to the surface of the workpiece 4 with the contour 41 bent. When deflected to the right, the cutting tube becomes 21 in the laser cutting head 2 into it and with a deflection to the left from the cutting head 2 pushed out. This example makes it clear that with the over the cutting tube 21 adjustable focusing optics 23 not mandatory, the optical axis 24 perpendicular to the workpiece 4 align.

Based on the example in 3d it is shown that also workpieces 4 edit that does not have a surface in one plane. With the arrangement described above becomes a contour 41 edited, which is about a height difference in the workpiece 4 extends. To compensate, the cutting tube 21 when passing the height difference also in a deflection to the right in the laser cutting head 2 in and to the left from the cutting head 2 moved out.

LIST OF REFERENCE NUMBERS

1

multi-axis robot

11

first axis of rotation

12

first hand axis

13

second axis of rotation

14

second hand axis

15

Wheelbase

2

Laser cutting head

21

cutting tube

22

distance sensor

23

focusing optics

24

optical axis

25

linear actuator

3

laser beam source

31

laser beam

32

Laserstrahleinkopplung

33

deflecting

34

focus point

4

workpiece

41

contour

42

Center of gravity of the contour

5

control unit

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 7209802 B2 [0006, 0010]

Claims (8)

Multi-axis robot ( 1 ) for the laser machining of workpieces with a first hand axis ( 12 ), which has a first axis of rotation ( 11 ) and a perpendicular thereto oriented second hand axis ( 14 ), which has a second axis of rotation ( 13 ) and one on the second hand axis ( 14 ) to the second axis of rotation ( 13 ) rotatable laser cutting head ( 2 ) with an optical axis ( 24 ) having focusing optics ( 23 ) for focusing one through the laser cutting head ( 2 ) guided laser beam ( 31 ) on a workpiece ( 4 ), characterized in that at the laser cutting head ( 2 ) a distance sensor ( 22 ) is provided and a linear drive ( 25 ), which is connected to the distance sensor ( 22 ) so that the focusing optics ( 23 ) along the optical axis ( 24 ) is displaceable to the focal point ( 34 ) even with changes in the distance of the laser cutting head ( 2 ) to the workpiece ( 4 ) on the workpiece ( 4 ) to keep. Multi-axis robot ( 1 ) for the laser machining of workpieces according to claim 1, characterized in that the laser cutting head ( 2 ) one along the optical axis ( 24 ) movable cutting tube ( 21 ) for receiving the focusing optics ( 23 ) to the laser cutting head ( 2 ) at a constant distance to the workpiece ( 4 ) to keep. Multi-axis robot ( 1 ) for the laser machining of workpieces according to claim 2, characterized in that the movable cutting tube ( 21 ) above the linear drive ( 25 ) an indirect connection to the laser cutting head ( 2 ) having. Multi-axis robot ( 1 ) for the laser machining of workpieces according to claim 1, characterized in that the distance sensor ( 22 ) is a non-contact distance sensor for capacitive distance measurement. Multi-axis robot ( 1 ) for the laser machining of workpieces according to claim 2, characterized in that the distance sensor ( 22 ) directly to the workpiece ( 4 ) opposite to the movable cutting tube ( 21 ) is arranged. Multi-axis robot ( 1 ) for the laser machining of workpieces according to one of the preceding claims, characterized in that the connection between the distance sensor ( 22 ) and linear drive ( 25 ) via a control unit ( 5 ) he follows. Multi-axis robot ( 1 ) for the laser machining of workpieces according to claim 6, characterized in that the control unit ( 5 ) for the evaluation of the distance sensor ( 22 ) and for the corresponding activation of the linear drive ( 25 ) has a data processing speed in real time. Multi-axis robot ( 1 ) for the laser machining of workpieces according to claim 1, characterized in that the linear drive ( 25 ) has a travel of +/- 30 mm about a center position.

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