Abstract
A beam-forming and deflecting optical system for a laser machining device includes at least two optical elements, which are arranged one behind the other in the direction of the laser beam and which are formed by wedges with respective wedge angles, wherein at least one optical element is connected to a drive for the rotation of the optical element about the optical axis, whereby an optical wedge can be rotated relative to the at least one other optical wedge. Also a method for machining a workpiece uses a collimated laser beam. In order to achieve different shapes of the laser beam on the workpiece, each of the optical wedges, which are arranged one behind the other, in each case cover only a part of the laser beam.
Claims
1. A laser machining device for machining a workpiece using a collimated laser beam, the laser machining device comprising: a laser generating device adapted to generate a laser beam; a collimating lens adapted to collimate the laser beam to provide a collimated laser beam; a focusing lens adapted to focus the collimated laser beam on the workpiece to be machined; and a beam-forming and deflecting optical system arranged between the collimating lens and the focusing lens, the beam-forming and deflecting optical system comprising: a first optical element comprising a first optical wedge having a first wedge angle; a second optical element comprising a second optical wedge having a second wedge angle, the second optical element disposed behind the first optical element in a direction of the collimated laser beam; wherein at least one of the first optical element and the second optical element is connected to a drive adapted to rotate the at least one of the first optical element and the second optical element about an optical axis and to rotate at least one of the first optical wedge and the second optical wedge relative to the other of the first optical wedge and the second optical wedge; and wherein each of the first optical wedge and the second optical wedge cover only a part of the laser beam.
2. The laser machining device as claimed in claim 1 wherein the first wedge angle and the second wedge angle are quantitatively equal.
3. The laser machining device as claimed in claim 1, wherein each of the first optical wedge and the second optical wedge cover between 25% and 50% of the laser beam.
4. The laser machining device as claimed in claim 1, wherein the first optical wedge and the second optical wedge are formed in the shape of a sector of a circle or in the shape of a segment of a circle.
5. The laser machining device as claimed in claim 1 wherein the first optical wedge and the second optical wedge are each arranged in a respective hollow shaft.
6. The laser machining device as claimed in claim 5, further comprising at least one actual value sensor adapted to determine a position of at least one of the first optical wedge, the second optical wedge or the respective hollow shaft.
7. The laser machining device as claimed in claim 5, wherein each of the first optical wedge and the second optical wedge or the respective hollow shaft is connected to a respective drive adapted to independently rotate the respective first optical wedge and the second optical wedge about the optical axis.
8. The laser machining device as claimed in claim 5, further comprising a drive adapted to jointly rotate the first optical wedge and the second optical wedge or the respective hollow shaft.
9. The laser machining device as claimed in claim 1, wherein the first wedge angle and the second wedge angle are at least 1 millirad.
10. The laser machining device as claimed in claim 1, wherein the first optical wedge and the second optical wedge are made of quartz glass, borosilicate-crown glass, zinc selenide, or zinc sulfide.
11. The laser machining device as claimed in claim 1, wherein the drive is connected to a motor control.
12. A method for machining a workpiece using a collimated laser beam, the method comprising the steps of: providing a collimating lens; providing a focusing lens; providing a beam-forming and deflecting optical system arranged between the collimating lens and the focusing lens, comprising at least two optical elements arranged one behind the other, wherein the at least two optical elements comprise at least two optical wedges, each having a respective wedge angle; rotating at least one of the at least two optical wedges about an optical axis relative to another of the at least two optical wedges; providing a laser beam to pass through the collimating lens to form the collimated laser beam; running the collimated laser beam through the beam-forming and deflecting optical system; and irradiating a surface of the workpiece by running the collimated laser beam through the focusing lens; wherein the at least two optical wedges only partially cover the laser beam.
13. The method as claimed in claim 12, wherein the laser beam runs through the at least two optical wedges and the respective wedge angle of the at least two optical wedges is quantitatively equal.
14. The method as claimed in claim 12, further comprising the step of rotating the at least two optical wedges at a rotational speed of between 100 and 10000 U/min.
15. The method as claimed in claim 12, further comprising the step of detecting a position and rotation of the at least two optical wedges using at least one actual value sensor.
Description
(1) The present invention is described in more detail on the basis of the enclosed drawings, in which:
(2) FIG. 1 shows a block diagram of a device for machining a workpiece using a laser beam according to the prior art;
(3) FIG. 2 shows an embodiment alternative of a beam-forming and deflecting optical system according to the invention in cut side view;
(4) FIG. 3 shows a top view onto the beam-forming and deflecting optical system according to FIG. 2;
(5) FIG. 4A to 4D show various positions of two semi-circular optical wedges of a beam-forming and deflecting optical system with respect to one another for attaining various shapes of laser beams on the workpiece;
(6) FIG. 5 shows an embodiment of a beam-forming and deflecting optical system comprising drives for the movement of the optical wedges in partially cut form;
(7) FIG. 6 shows various beam shapes at various angular positions between two optical wedges to one another (static spots);
(8) FIG. 7A shows various spot shapes in response to additional rotation;
(9) FIG. 7B shows the corresponding power densities of the spot shapes according to FIG. 7A; and
(10) FIG. 8 shows the spot shape in response to a joint pendulum movement of the optical wedges.
(11) FIG. 1 shows a block diagram of a device 10 for machining a workpiece W using a laser beam L according to the prior art. The machining device 10 includes a laser generating device 12 and an optical fiber 13, via which the laser beam L is transported to the corresponding machining head. The laser beam L is collimated, for example, using a collimating lens 14 and is focused on the surface of the workpiece W to be machined via a focusing lens 15. The laser beam L can be influenced via a beam-forming and deflecting optical system 1 arranged between the collimating lens 14 and the focusing lens 15 in such a way that the spot shape S on the surface of the workpiece W to be machined can be changed. For this purpose, at least two optical elements 2, 3 are arranged one behind the other in the beam path of the laser beam L in the beam-forming and deflecting optical system 1, which optical elements 2, 3 influence the collimated laser beam L accordingly, so that the spot shape S on the surface of the workpiece W to be machined changes. By means of a change of the orientation of an optical element 2 with respect to the other optical element 3, a change of the spot shape S of the laser beam L can also take place during the machining of the workpiece W. For this purpose, an optical element 2 is connected to a corresponding drive 4. In the case of a laser-hybrid welding apparatus, the laser beam L is combined with at least one electric arc (not illustrated).
(12) FIG. 2 shows an embodiment alternative of a beam-forming and deflecting optical system 1 according to the invention in cut side view. The at least two optical elements 2, 3 of the beam-forming and deflecting optical system 1 are formed by means of optical wedges 5, 6 with a respective wedge angle α.sub.1, α.sub.2. Optical wedges 5, 6 or prisms of this type, respectively, deflect the collimated laser beam L according to the wedge angle α.sub.1, α.sub.2, whereby the point of impingement of the laser beam L on the surface of the workpiece W to be machined and thus the spot shape S changes. Due to the fact that the two optical wedges 5, 6 in each case only cover a part of the laser beam L, the number of the points of impingement of the laser beam on the surface of the workpiece W can be changed. In the illustrated exemplary embodiment, the two optical wedges 5, 6 in each case cover essentially 50% of the laser beam L. Downstream from the beam-forming and deflecting optical system 1, viewed in the direction z of the laser beam L, a focusing lens 15 is arranged, via which the deflected laser beam L is focused accordingly on the surface of the workpiece W to be machined. By means of rotation of at least one optical wedge 5, 6 about the optical axis c, a change of the spot shape S on the surface of the workpiece W can be attained. By means of a rotation of the entire beam-forming and deflecting optical system 1 about the optical axis c, a dynamic beam formation or rotation, respectively, of the spot shape S about the optical axis c can be attained. The second optical wedge 6 with the wedge angle α.sub.2 can also be arranged in a mirror-inverted manner to the optical wedge 6 according to FIG. 2, whereby other beam and spot shapes S can be generated. When, for example, the wedge angles α.sub.1, α.sub.2 of the optical wedges 5, 6 are quantitatively equal, a cancellation of the deflection of the collimated laser beam L can take place by means of the optical wedges 5, 6 in the case of a corresponding opposite orientation of the two optical wedges 5, 6 to one another, whereby the collimated laser beam L is not influenced significantly by means of the beam-forming and deflecting optical system 1, and a spot shape S results on the surface of the workpiece W, which corresponds to a spot shape S without beam-forming and deflecting optical system 1. This means that in the case of a corresponding oppositely oriented positioning of the optical wedges 5, 6 with quantitatively equal wedge angles α.sub.1=α.sub.2, the beam formation and deflection of the laser beam L can be switched into a neutral position.
(13) FIG. 3 shows a top view onto the beam-forming and deflecting optical system 1 according to FIG. 2. In the top view, the optical wedges 5, 6 are preferably formed in the shape of a sector of a circle or in the shape of a segment of a circle, and have a radius R in the range of 10 mm to 40 mm, whereby the size of the beam-forming and deflecting optical system 1 can be kept small, and the overall size of the machining head of the laser machining device 10 can be reduced.
(14) Various positions of two semi-circular optical wedges 5, 6 of a beam-forming and deflecting optical system 1 with respect to one another for attaining various shapes of laser beams L on the workpiece W are illustrated in FIG. 4A to 4D. In the illustrated exemplary embodiment, the two optical wedges 5, 6 have opposite and equal angles α.sub.1=−α.sub.2. In the case of a position of the two optical wedges 5, 6 to one another with an angle Δβ=180° according to FIG. 4A, the laser beam L is deflected by the optical wedge 5 and optical wedge 6 in the same direction, whereby a spot shape S results at the workpiece W, which is deflected accordingly from the zero point N or center, respectively, of the optical axis c. In the case of the position of the optical wedges 5, 6 to one another with an angle Δβ=135° between two optical wedges 5, 6 illustrated in FIG. 4B, a spot shape S results on the surface of the workpiece W, which has four points of impingement of the laser beam L at various points around the optical axis c according to the wedge angles α.sub.1 and α.sub.2 of the optical wedges 5, 6, the deflecting effects of which add up accordingly in the overlap region. In the case of the arrangement according to FIG. 4C with an angle Δβ=90° between the optical wedges 5, 6, the spot shape S, which is illustrated accordingly, results on the workpiece W. In the case of the position of the optical wedges 5, 6 to one another according to FIG. 4D (angle Δβ=0°), the effects of the optical wedges 5, 6 with wedge angle α.sub.1=−α.sub.2 compensate, whereby a spot shape S results on the workpiece W, which is arranged in the center of the optical axis c or the zero point N, respectively, and which corresponds to a spot shape S of the laser beam L without beam-forming and deflecting optical system 1.
(15) By changing the orientation of the two optical wedges 5, 6 to one another or by means of the change of the angle Δβ between the optical wedges 5, 6, respectively, a change of the spot shape S can thus be attained on the surface of the workpiece W. By increasing the number of the optical wedges, for example to three or more optical wedges, the number of the spots in the spot shape S can be increased, and the variation of the attainable spot shapes S can be changed even further.
(16) FIG. 5 shows an embodiment of a beam-forming and deflecting optical system 1 comprising drives for the movement of the optical wedges 5, 6 in partially cut form. The optical wedges 5, 6 of the beam-forming and deflecting optical system 1 are in each case arranged in hollow shafts 7, 8, which can be rotated about the optical axis c via corresponding drives 9. The drives 9 can be formed, for example, by means of hollow shaft motors or torque motors. In addition to the drives 9 for the rotation of the optical wedges 5, 6 or hollow shafts 7, 8, a further drive 9 for the rotation of the entire beam-forming and deflecting optical system 1 about the optical axis c can be provided (not illustrated). Via corresponding actual value sensors 16, the positions of the optical wedges 5, 6 or hollow shafts 7, 8, respectively, can be detected. Corresponding motor controls 11 control the corresponding drives 9 according to the settings of an operating unit 17 or on the basis of other specifications, such as, for example, on the basis of the position and movement of the machining head of the laser machining device 10 with respect to the workpiece W or on the basis of parameters in the case of laser-hybrid applications, such as, for example, on the basis of welding parameters (welding current, welding voltage, feed speed of a welding wire, polarity of the welding current, process phases, etc.). The beam-forming and deflecting optical system 1 of the type at hand is characterized by a relatively small overall size and compact embodiment. For example, diameters d.sub.H of the hollow shafts 7, 8 in the range of between 25 mm and 90 mm are attained, whereby a small interference contour results. Cooling ducts for guiding a cooling fluid (not illustrated) can optionally be arranged in the housing of the beam-forming and deflecting optical system 1.
(17) Various spot shapes S are reproduced in FIG. 6 at various angles Δβ between the optical wedges 5, 6 to one another. Using the example of two optical wedges 5, 6 with opposite and equal wedge angles α.sub.1=−α.sub.2, various spot shapes S are illustrated here, wherein the angular position Δβ of the two optical wedges 5, 6 to one another is varied in 30° steps. The resulting spot shapes S on the surface of the workpiece W to be machined are illustrated therebelow. By means of various spot shapes S, the heat input or the weld pool, respectively, as well as the cooling rate can be optimally adapted for various machining tasks. For example, a higher gap bridgeability can be attained by means of a wider spot shape S (sixth image from the left with an angle) Δβ=150°. In the case of the angular position Δβ=180°, a spot shape S results, which is offset, at best, about the zero point N or the optical axis c, respectively, but which is unchanged.
(18) FIG. 7A shows various spot shapes S in response to additional rotation of the optical wedges 5, 6 with the same speed in the same direction about the zero point N or the optical axis c, respectively. The angle Δβ between the optical wedges 5, 6 is maintained thereby. Spot shapes S, which may be ring-shaped (image on the far right according to FIG. 7A with an angle Δβ=180°), can be attained thereby. Rotational movements with continuously changeable angular position Δβ can likewise be realized.
(19) The power density P.sub.L of the laser beam L is illustrated in FIG. 7B as a function of the radial position x.sub.r at the different angular positions Δβ according to FIG. 7A. By means of the corresponding rotation of the spot shapes S, different energy inputs can be attained on the surface of the workpiece W to be machined. In the case of various positions or movements of the laser beam L with respect to the workpiece W, certain spot shapes S can be advantageous, which is why they can also be selected as a function of the position and movement. In the case of combined laser-hybrid applications, the spot shape S of the laser beam can also be selected as a function of parameters of the electric arc or of the process phases.
(20) Lastly, FIG. 8 shows the spot shape S in the case of a joint pendulum movement of the optical wedges 5, 6 about a specified angular range. In the illustrated exemplary embodiment, a constant angular position of the optical wedges 5, 6 to one another of Δβ=135° is assumed, wherein the optical wedges 5, 6 are jointly moved back and forth about the specified angular range Δχ=90°. By means of such a pendulum movement, the specified angular range Δχ can be passed over about the optical axis c, and a corresponding heat distribution on the surface or in the workpiece W, respectively, can be attained. Pendulum movements with continuously changeable angular position Δβ can likewise be realized.
(21) The present invention is characterized by a simple and adaptive formation of the laser beam L with small interference contour.
