DE102010032781B4 - Method for separating workpieces with laser beams - Google Patents

Abstract

Method for the separating machining of workpieces with laser beams, in which at least two cw-mode operated laser beams (1, 2) having mutually different wavelengths, by a relative movement of the laser beams (1, 2) and the workpiece (5) along a cutting contour (6) deflected and focused with an optical element (9, 10) are directed to the surface to be processed and the laser beams (1, 2) are simultaneously directed to the workpiece surface to be machined so that cover the focal spots at least for the most part ; wherein with the optical element (9) the position of the focal plane is tracked according to the material removal carried out and the machining of workpieces (5), which are formed as a composite with at least two different materials with layers A and B, is carried out so that a layer A in a first separation cut and then a layer B is removed in a second section.

Description

The invention relates to a method for separating processing with laser beams. It can be worked in so-called remote technique. It can be used advantageously in the machining of composite workpieces.

In composite workpieces, these can be formed of several layers, which in turn are formed of different materials. However, materials show a different absorption behavior for radiation with different wavelengths. This may increase the time required for processing or the quality of the cut edges leaves something to be desired.

The invention relates to a method for separating processing with laser beams. It can be worked in so-called remote technique. It can be used advantageously in the machining of composite workpieces.

In composite workpieces, these can be formed of several layers, which in turn are formed of different materials. However, materials show a different absorption behavior for radiation with different wavelengths. This may increase the time required for processing or the quality of the cut edges leaves something to be desired.

In JP 2005 238 246 A there is disclosed a cutting apparatus in which two of two laser sources emitted are directed onto a workpiece on an optical axis.

At the US 2003/0052104 A1 known device to a laser beam from different directions are directed to a workpiece. The laser source should be moved.

In DE 10 2008 027 130 A1 For example, there is known a laser beam cutting method in which a focused laser beam of predetermined power density is focused on a workpiece at a minimum feed speed to form a kerf.

The DE 20 2007 018 689 U1 relates to a system for actively adjusting the focus position for laser beams.

A laser processing with two laser beams of a YAG laser and a CO ₂ laser, which are to be directed to a point of a workpiece surface, is out GB 2 175 737 A known.

The EP 0 426 600 A2 relates to a device and a method for the exact and rapid processing of workpieces. Two laser beams with different energies are used.

A method and a device for punctiform machining of a workpiece by means of laser radiation are known in DE 102 37 893 B3 disclosed. In this case, at least two laser beams are each guided over a separate deflection unit and brought together via a rotating chopper disc in one direction for processing different target points.

It is therefore an object of the invention to increase the productivity and quality of the cutting processing with laser beams.

According to the invention, this object is achieved by a method having the features of claim 1. Advantageous embodiments can be achieved with features contained in the subordinate claims.

In the method according to the invention, at least two laser beams operated in cw mode, which have wavelengths deviating from one another, are deflected along a cutting contour with a beam deflecting system and focused with an optical element on the surface to be machined. In this case, the two laser beams and the workpiece are moved relative to each other. In this case, for a preferably two-dimensional deflection, a beam deflecting system (scanner) can be used with two reflecting elements (s) pivotable about one axis each or one about two axes. This deflection can be superimposed on another feed motion, so that a large-scale processing can be carried out in a shorter time.

It is possible to direct two or more laser beams simultaneously on the surface of a workpiece and thus to remove material. The laser beams can be directed alternately with changed power to the surface. It can therefore be directed at the same time a laser beam of a wavelength with higher power than a respective other laser beam for processing on the workpiece. The increase and decrease in power can also be done alternately. However, a laser beam which is not required for processing at a time can also be directed to a beam trap.

For the beam guidance and shaping of the laser beams, the same elements can be used, so that the system complexity is low.

In the invention, it is advantageous that it is possible to dispense with a cutting gas and the ablation of the material can be achieved, whereby the operating costs can be kept small.

It is advantageous with the optical element for beam shaping to track the position of the focal plane corresponding to the removal of material so that a high energy density can be utilized in the focal spot and the kerf is not increased by a divergence of the radiation. As the optical element, a reflective element suitable for focusing can be preferably used. During processing, the laser beams should be directed to the workpiece surface at which a material removal should take place so that the size of the surface of the focal spot is the same, at least approximately the same size. This allows them to cover themselves while irradiating the workpiece. This can be achieved by suitable beam shaping. Since the level of machining also changes as a result of the removal of material, and consequently the path which lengthens the laser beams to the surface to be machined, this should also be taken into account in the focusing and in the deflection of the laser radiation, since this requires a different guide Burning spots in the different levels requires consideration. This should also be taken into account for the formation of a kerf of the same width across the thickness of the workpiece. Both focal spots should have in each plane during machining an extension perpendicular to the feed axis direction, which is ≤ the formed kerf.

With increasing focal spot area, the power of the laser beam emitting laser beam sources should be increased according to the reduced energy density in the focal spot.

It should laser beams whose wavelength is greater than 800 nm, are used. Wavelengths in the infrared range between 1 and 15 μm are preferred. It can be fiber or disk laser for a laser beam with a smaller wavelength (λ about 1 micron), z. B. for a metal removal and a CO ₂ laser for a removal of plastic with a wavelength of 10 microns are used.

As a result, the absorption behavior of the different materials can be taken into account and short interaction times, which lead to a reduced heat input into and a lower distortion of the workpiece, can be achieved.

If two laser beams are simultaneously directed onto the workpiece surface, the focal spots should at least largely overlap. As a result, an equal kerf width can be achieved across the thickness of the workpiece to be machined.

As already stated, melted material can be expelled without the supply of cutting gas due to the influence of the laser radiation and this can be achieved by vapor pressure or sublimation / vaporization / oxidation.

However, it is possible to supply a protective gas in the processing area. It can also be a suction or a so-called cross-jet for the removal of formed vapors are provided.

Since the transmission and reflectivity for the laser beams having the different wavelengths are different for the optical elements used for the beam guidance and shaping, this can also be taken into account advantageously in the selection of such optical elements. Thus, coatings can be formed on these optical elements, each of which achieves a high transmission or reflectivity for the radiation having the different at least two wavelengths.

In the separating processing, at least one laser beam may be directed to the surface to be processed with a reflective element or from a reflective surface of an element. There are several alternative options. Thus, the laser beams can be directed from different directions onto a point of a reflective surface of an element and be reflected so that they impinge with the same optical axis on the surface to be machined of the workpiece. The corresponding element can be arranged statically and the angle of incidence of the laser beams can be selected taking into account the respective wavelength.

In other alternatives, a movable element may be used in which the different laser beams impinge on the same as a result of the movement of the element at different positions of the element. This may be a rotating or a translational movement between two reversal points traversing element.

Such movable elements may have at least one reflecting surface on which one of the laser beams impinges in a position of the element and is directed by this reflecting surface onto the surface of the workpiece to be machined. At least one opening / recess may then be present on the element, by means of which, in another position of the element after its movement, a different laser beam is directed in the direction of the surface of the workpiece to be machined. The laser beams are from opposite directions directed to the movable element. A laser beam directed through an aperture on the workpiece may, in a position of the element where another laser beam is directed from a reflecting surface onto the workpiece, be directed to a likewise reflecting surface on the element opposite the other reflecting surface of the element directed to the element and directed from there to a beam trap.

With the invention composite components of glass fiber reinforced aluminum (glare), Ti-CFK composite, TiGr composite, other composite panels (for facades, gypsum fiber / Fermacell, one with a metal foil, such as aluminum, on a plastic or plastic foam board In addition, electrical sheets which are coated on at least one surface with a lacquer, other foil-laminated components or composite components, which are formed of metal / ceramic / plastic, can be processed separately.

The invention will be explained in more detail by way of example in the following.

Showing:

1 in schematic form, a structure with which the method according to the invention can be carried out;

2 a separation in four steps of a workpiece made of two materials;

3 an example of a cutting contour that can be processed in the invention;

4 an arrangement which does not fall under the invention;

5 another example of an arrangement for carrying out the method according to the invention;

6 an arrangement in which two laser beams are deflected with the same optical axis in the direction of the workpiece, which does not fall under the invention;

7 a movable element, with which laser beams can be directed to the workpiece for processing, which does not fall under the invention and

8th a movable element, with which laser beams can be directed to the workpiece for machining, which does not fall under the invention.

1 shows a structure for carrying out the method according to the invention suitable structure. There are two laser beams 1 and 2 with different wavelength on a wavelength-selective transparent window 7 directed. The laser beam 1 hits an area of the window 7 up and step through it. The laser beam 2 is on the opposite side of the window 7 directed and reflected there. Both laser beams 1 and 2 become on a common optical axis to one the laser beams 1 and 2 focusing optical element 4 and from there to a beam deflection system 3 directed. With the beam deflection system 3 and optionally in addition to a drive system, not shown, a cutting contour 6 An example of this is in 3 shown with the focal spots of the two laser beams 1 and 2 traversed while material to be removed.

The workpiece 5 is made of several layers of different materials.

In unillustrated form, it is possible to use a further third laser beam, which then also at least partially on the same optical axis, as the two laser beams 1 and 2 on the workpiece 5 can be directed. The third laser beam can then again have a different wavelength.

With 2 should a separation into four sections be clarified. The feed movement takes place along the trainee cutting contour 6 , which should be completely driven at least once every cut. The workpiece made of several layers A and B. 5 is then processed so that the individual layers A and B are successively removed from the surface. In the first separation cut, the removal of the uppermost layer with the material A is to be achieved. This is one of the two laser beams 1 or 2 one and the other laser beam 1 or 2 switched off or it is operated at reduced power. For this is a laser beam 1 or 2 selected, which has a better absorption behavior for the material A.

After removal of this uppermost layer A, the underlying layer and formed from the material B layer is removed in the second section, for which essentially, as described in advance to the top layer, but the corresponding other laser beam 1 or 2 thereby exploited.

With the optical element 4 the focus can be made so that the focal plane depending on the removed material A and B deeper into the workpiece 5 can be tracked into it. It should in the invention in any case, so with other suitable Arrangements, which will be discussed in the following examples, be assured that, as in the relatively schematic representation in 2 recognizable, the kerf has a constant width over the entire depth. The kerf can also be formed so that it is slightly tapered starting from the surface.

If the workpiece to be machined is a composite material which is referred to as "glare" and which has been produced from a multi-layer composite with glass fiber reinforced plastic and aluminum arranged alternately, a material removal of the aluminum layers with a laser beam at a wavelength of 1 μm and can be achieved with glass fiber reinforced plastic layers with a laser beam of a wavelength of 10 microns.

The 4 shows an arrangement in which the two laser beams 1 and 2 from two different directions on a beam deflection system 3 directed. With at least one reflective element 3.1 the deflection of the laser beams takes place 1 and 2 for separating machining along the cutting contour 6 , In the beam path of the laser beams 1 and 2 is each a focusing element 9 and 10 arranged, with the adjustment of the position of the focal plane can be achieved. This is indicated by the double arrows. The laser beam 1 will also work with the optical element 11 collimated and so on the focusing element 9 directed.

At the beam deflecting system 3 are windows in the example shown 3.2 and 3.3 through which the laser beams 1 and 2 on the reflective element 3.1 and another window 3.4 through which they touch the workpiece 5 be addressed. The window 3.2 . 3.3 and 3.4 should from a for the different radiations optically transparent material, such. As ZnSe, CaF ₂ , ZnS or MgF ₂ , and thereby have an absorption of less than 10%. Advantageous are the windows 3.2 . 3.3 and 3.4 with an anti-reflective coating and the reflective element 3.1 with a reflective coating, e.g. As gold coated.

In the beam deflecting system 3 is also an optical element or an array of multiple optical elements 3.5 available. This can be a further beam shaping of the laser beams 1 and 2 be achieved. For this purpose, a plan field optics or a telecentric lens can be used. Again, highly transparent materials and an anti-reflective coating should be provided.

At the in 5 shown arrangement, the laser beams 1 and 2 perpendicular to each other after pre-focusing on an optical coupling element 12 directed. This coupling element 12 is for the laser beam 2 transparent and the laser beam 2 is changed by reflection by 90 ° in its direction. From there, both laser beams hit 1 and 2 on the reflective element 3.1 of the beam deflecting system.

The of the reflective element 3.1 deflected laser beams 1 and 2 become analog again, as with the in 4 shown optical arrangement 3.5 , shaped and then onto the workpiece 5 directed.

In the examples according to the 4 and 5 but can also be at least one of the laser beams 1 and 2 transmissive elements, namely the windows 3.2 . 3.3 and or 3.4 as well as the arrangement of one or more optical elements 3.5 be waived. This can cause losses to the surfaces caused by reflection, diffraction and scattering on these optical elements 3.2 . 3.3 . 3.4 and 3.5 can be avoided. There is no consideration of the different wavelengths of the two laser beams 1 and 2 required if no such transmissive optical element 3.2 . 3.3 . 3.4 and 3.5 in the beam path of the two laser beams 1 and 2 in which both optical axes of the two laser beams 1 and 2 lie on the same axis, there is more. The beam guidance and / or focusing then takes place in this part of the beam path exclusively with at least one reflective element. In the examples according to the 4 and 5 this is the reflective element 3.1 ,

The 6 shows an arrangement in which two laser beams are deflected with the same optical axis in the direction of the workpiece. The two laser beams 1 and 2 are from the same side but from different directions on a reflective surface of an element 13 directed. They meet the one point 13.1 on and are reflected according to their angle of incidence. The reflection takes place in such a way that both laser beams 1 and 2 on the same optical axis A in the direction of the workpiece, not shown here 5 be reflected, what with the arrows on the laser beams 1 and 2 should be clarified.

They can through the aperture 14 on a reflective element 15 impinge, with which they on the workpiece, not shown here 5 can be reflected.

In 6 is also a polygon wheel 13.2 shown, whose radially outer surfaces on the front sides reflective for the laser beams 1 and 2 are formed. The laser beams can be directed to these reflective surfaces during the rotation of the polygon wheel and reflected from there to the component. It is favorable to use a polygon wheel with many corners and correspondingly many reflective surfaces. The laser beams 1 and 2 can impinge on the reflective surfaces at different angles in unillustrated form. Because the polygon wheel 13.2 Both laser beams can rotate 1 and 2 from a reflective surface to a common or juxtaposed position on the workpiece surface to be machined along the machining contour 6 be directed. This also allows them to impinge with the same optical axis A on the surface to be machined of the workpiece.

The 7 shows a movable element 8th as is the case for the beam guidance of the two laser beams 1 and 2 to the workpiece 5 can be used. This is a disc-shaped element 8th which can be moved by rotation. On a surface of a page are reflective surfaces 8.1 educated. With the sectional view along the line BB can be seen that on one of these reflective surfaces 8.1 incident laser beam, here the laser beam 2 , there in the direction of the workpiece 5 is reflected when the element 8th has reached a suitable angular position as a suitable position during rotation. The respective times with the one irradiation with the two laser beams 1 or 2 can be done by means of the speed of the element 8th and / or the respective length of the reflective surfaces 8.1 and the openings 8.2 along the circular path on which the two laser beams 1 and 2 through the element 8th or on the reflective surfaces 8.1 to be influenced.

The other laser beam, in this case the laser beam 1 can with appropriate angular position of the element 8th through one of the two openings 8.2 towards the workpiece 5 be blasted. This is illustrated by the sectional view along the line AA. The laser beams 1 and 2 are doing so from two opposite sides on the element 8th directed.

In a version of a likewise rotating element 8th as it is in 8th are shown are again reflective surfaces 8.1 and breakthroughs 8.2 available. The reflective surfaces 8.1 perforations 8.2 are equidistant to each other and arranged alternately. Again, the laser beam 1 during rotation in suitable angular positions of the element 8th through the element 8th and the breakthroughs 8.2 be directed to the workpiece surface to be machined. In other angular positions the laser beam hits 2 on reflective surfaces 8.1 on the outer edge of the element 8th formed and at an angle of 45 ° with respect to the axis of rotation of the element 8th are aligned. The laser beam 2 becomes perpendicular to the laser beam 1 and perpendicular to the axis of rotation of the element 8th on the reflective surfaces 8.1 directed, as with the right representation of the 8th is recognizable.

With the length of the reflective surfaces 8.1 and the openings 8.2 on the radius on which they are arranged and by varying the speed of the element 8th In addition, an influence can be exerted on the removal of material, since this can be used to determine the time interval length in which a material removal takes place with one of the two laser beams 1 or 2 can be done. This also applies to the example according to 7 to.

The reflective surfaces 8.1 can at the in the 7 and 8th represented elements 7 and 8th be designed as a planar planar but also as concave surfaces. Concave reflecting surfaces 8.1 may cause additional focusing, thereby reducing the area of the focal spot of the laser beam 2 can be downsized. Here, the laser radiation of the laser beam should 2 a larger wavelength than the laser radiation of the laser beam 1 have, so that an additional adaptation of the sizes of the surfaces of the focal spots of the two laser beams 1 and 2 is reachable.

Claims (8)

Method for separating workpieces with laser beams, in which at least two laser beams operated in cw-mode ( 1 . 2 ) having mutually different wavelengths, by a relative movement of the laser beams ( 1 . 2 ) and the workpiece ( 5 ) along a cutting contour ( 6 ) and with an optical element ( 9 . 10 ) focused on the surface to be processed and the laser beams ( 1 . 2 ) are simultaneously directed to the workpiece surface to be machined so that cover the focal spots at least for the most part; wherein with the optical element ( 9 ) the position of the focal plane is tracked according to the material removal carried out and the machining of workpieces ( 5 ), which are formed as a composite with at least two different materials with layers A and B, is performed so that a layer A is removed in a first separation section and then a layer B in a second section. Method according to claim 1, characterized in that the laser beams ( 1 . 2 ) are operated alternately with modified power. A method according to claim 1 or 2, characterized in that the separation is carried out waiving a cutting gas. Method according to one of the preceding claims, characterized in that the two laser beams ( 1 . 2 ) with a beam deflection system ( 3 ) are deflected two-dimensionally. Method according to one of the preceding claims, characterized in that laser beams ( 1 . 2 ) whose wavelength is greater than 800 nm, are used. Method according to one of the preceding claims, characterized in that the laser beams ( 1 and 2 ) are so directed to the workpiece surface to be machined, that the surfaces of the focal spots are at least approximately equal and / or both focal points in each plane during processing have an extension perpendicular to the feed axis direction, which is ≤ the formed kerf. Method according to one of the preceding claims, characterized in that at least one laser beam ( 1 . 2 ) with a reflective element ( 3.1 . 13 ) or of a reflective surface ( 8.1 ) of an element ( 8th ) on the surface of the workpiece to be machined ( 5 ). Method according to one of the preceding claims, characterized in that the two laser beams ( 1 . 2 ), at least in the beam path in which both optical axes lie in the same axial direction, exclusively with at least one reflecting and / or focusing optical element ( 3.1 ) are deflected and / or shaped.

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