Laser processing method and device

Abstract

To provide a laser processing method and a laser processing device which can manufacture either or both of a large deep hole and cutout, at a zero or a predetermined taper angle, in a high-quality component.SOLUTION: The laser processing method comprises steps of: positioning at least either of a work-piece (10) and a scanning axis line (34) at a first relative position; emitting a laser beam (20) to processed cubic contents in a surface area; causing relative motion between the work-piece and the laser beam (20); and scanning the laser beam (20) along a first cutting path, the method further comprising steps of: removing the first processed cubic contents and emitting the laser beam (20) to second processed cubic contents; scanning the laser beam (20) along a second cutting path; and removing at least some of the second processed cubic contents in order to form a second side wall.SELECTED DRAWING: Figure 4a

Description

[Technical field]

[0001] The present invention relates to a laser processing method and apparatus, and more particularly to a laser processing method and apparatus for forming zeros and / or predetermined taper cuts and forming cutouts and / or holes in a workpiece. [Background technology]

[0002] It is known that machining workpieces of hard and / or brittle materials such as metals, such as stainless steel, light metals, such as titanium, magnesium, aluminum, or ceramics, cermets, tungsten carbide, polycrystalline diamond (PCD), CVD diamond, polycrystalline cubic boron nitride (PCBN), with or without coating, is difficult. For example, drilling insert hole configurations, with or without one or two countersinks to secure the insert to a tool holder, in indexable inserts made of ultra-hard materials is difficult. Laser processing methods and devices are generally known for machining such workpieces, but drilling zero taper holes in indexable inserts using a scanning unit is less known.

[0003] It is known to use drilling or cutting lasers to perform drilling or cutting, including high-precision bore holes, in such workpieces. Laser drilling or cutting is advantageous because it is fast, flexible, and allows drilling of complex shapes as well as bore holes or high-precision cutting. In comparison with conventional drilling methods with twist drills, laser drilling or cutting is cheaper in hard materials and / or when the diameter of the holes to be drilled is small, due to the non-contact process, which avoids wear and cracks on the processing tools.

[0004] In laser machining, a laser beam generator is used in combination with an optical system to direct a laser beam at a workpiece to be machined. The impact of the laser beam on the workpiece locally melts, vaporizes and / or ablates material of the workpiece, forming or extending a hole or cut in the workpiece. The location of the impact point on the workpiece can be controlled by moving either or both of the laser beam and the workpiece relative to one another, thereby controlling the shape of the hole or cut. In laser machining of holes, it is known to produce tapered holes, where the entrance diameter is larger than the diameter of the hole cutout or, in the case of a through hole, the exit diameter.

[0005] High precision and deep laser drilling can be performed by trepanning or helical drilling. Trepanning or helical drilling uses special optics that can change the angle of incidence of the laser beam and rotate the laser beam at high speed. The workpiece remains stationary. Both of these processes require complex optical setups to control the taper angle of the hole. Therefore, laser drilling without taper angle by these methods involves special and complex equipment and methods that can only be used for drilling holes but not for other laser processes. These known methods are generally performed with dedicated equipment and cannot be performed with conventional laser processing equipment that uses a scanning unit.

[0006] Another approach to avoid undetermined or unselected taper edges is to physically move the workpiece, particularly the holding or clamping device supporting the workpiece, while maintaining the same angle of incidence of the laser beam. This method requires high precision in translational and / or rotational movement of the workpiece by the laser processing machine, usually in four or five axes, and requires sophisticated control software to achieve zero taper edges or a determined taper edge. Additionally or alternatively, the laser machine, particularly the scanning unit, may be moved relative to the workpiece.

[0007] From the document DE 10 200 03 133 A1 a laser system and method for machining features of a workpiece are known. In particular a beam adjustment is described which controls the taper of the kerf or cut made in the workpiece. In order to generate a desired taper characteristic in the sidewall of the kerf by means of a focused laser beam propagating along the optical axis, the incidence angle and the azimuth angle of the optical axis are moved relative to the workpiece. During the cutting process, the workpiece and the beam axis are both in relative motion while the laser beam is actively machining the workpiece, in particular while it is irradiating the workpiece along the cutting path. According to this document, the machining spot is moved off-centre using two linear axes, which defines the angle of incidence of the beam on the machining surface. The machining speed is slow due to the slow speed of these axes compared to the speed of the optical axis and the need to move the workpiece a long distance to achieve the desired angle of incidence.

[0008] From US Pat. No. 5,399,513 a method and device are known for reducing the taper of the kerf produced by laser machining or scribing. The method is based on a strategic laser positioning which reduces the taper of the scribe or cut. The method thus comprises directing a laser beam to the surface of the substrate in a first cutting direction and tilting the laser beam at a beam tilt angle, and further directing the laser beam to the surface of the substrate in a second direction perpendicular to the first cutting direction and tilting the laser beam at a tilt angle. The cuts are made by aiming the laser beam to cut in the first cutting direction while applying the laser beam to the surface of the substrate, and aiming the laser beam in the second direction to cut in one of the first cutting direction and the second cutting direction opposite to the first cutting direction while applying the laser beam to the surface of the substrate. The described method requires a specific device for tilting the beam, which reduces flexibility and reduces the processing speed. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] US Patent Application Publication No. 2014 / 263212 [Patent Document 2] US Patent Application Publication No. 2012 / 132629 Summary of the Invention [Problem to be solved by the invention]

[0010] Therefore, it is an object of the present invention to provide a laser processing method and apparatus capable of producing well-defined cutouts, large and deep holes and / or cutouts in high quality parts with zero taper angle and / or predefined taper angle, especially negative taper angle. The laser processing apparatus can use a scanning unit, so that the processing capacity and throughput are high. Another object is to provide a laser processing method and apparatus, which eliminates post-processing and cleaning operations, improves repeatability, reliability, speed and accuracy, and thereby reduces manufacturing costs. Moreover, such a laser processing method provides process flexibility, high cutting speed and non-contact operation. [Means for solving the problem]

[0011] In one aspect of the invention, there is provided a method for laser machining a defined cut-out into a workpiece, comprising the steps of: - generating a laser beam propagating within a scanning unit along a scanning axis; - providing a workpiece supported and held by a holder and positionable relative to a scanning axis; The method includes the steps of: a) determining a machining volume of a workpiece having a surface area and a depth; b) determining a first relative position between the processing volume and the scan axis, in which the scan axis is oriented substantially perpendicular to a surface of the processing volume, and positioning one or both of the workpiece and the scan axis at the first relative position; c) directing a laser beam at a machining volume within the surface area and causing relative motion between the workpiece and the laser beam to scan the laser beam along a first cutting path; d) removing at least a portion of the processing volume to form a first cutout having a first sidewall with a first tapered characteristic; e) determining a second processing volume including the first sidewall and partially bounded by a second sidewall having a predetermined characteristic; f) determining a second relative position between a second machining volume and the scan axis and positioning one or both of the workpiece and the scan axis at said second relative position; g) directing the laser beam at a second machining volume with the scanning axis orientated at a predetermined tilt angle β relative to the workpiece and scanning the laser beam along a second cutting path to remove at least a portion of the second machining volume to form a second sidewall; Equipped with.

[0012] According to the invention, the method uses a combination of at least two different processing strategies. In the first processing strategy, the laser beam is applied with an incidence angle close to 0°, i.e. perpendicular to the surface of the workpiece to be processed, i.e. the top surface of the defined processing volume, resulting in a high material removal rate, but with a tapered character. In the second method, the laser beam is applied with a large incidence angle (usually more than 80°). At this high incidence angle, the material removal rate is lower than with the first strategy. However, a high surface quality can be achieved and the undesired tapered angle resulting from the first strategy can be eliminated.

[0013] Furthermore, this method addresses the problem of taper angle caused by laser processing with a scanning unit and the problem of low specific material removal rate by forming deep cutouts. By using multiple steps in depth, this method allows the characteristics of the scanned cutout to be controlled for complete material removal by repeating the scan or repeating the path of the laser beam.

[0014] The achievable taper angle of the cut surface using a scanning unit is typically more than 5°. This is due to the decrease in laser intensity when projected onto the inclined ablation surface, so that the ablation stops at a critical angle. Unlike conventional laser drilling methods using a scanning unit, the method described herein can produce cutouts with a given taper angle and quality variables such as entry, polished or exit shapes, contour accuracy and surface properties. With the proposed laser processing method, it is possible to produce positive cone-shaped, i.e. positively tapered cylindrical and negative cone-shaped, i.e. negatively tapered holes, as well as funnel-shaped bores, hour-shaped holes or Laval nozzle-shaped holes.

[0015] The laser processing method is preferably configured for laser processing workpieces comprising at least one of hard, ultra-hard, and brittle materials (e.g., for use in indexable inserts), or workpieces including multi-layer substrates having multiple layers of different materials and / or different heights.

[0016] In one embodiment, the cutout or formation in the workpiece is a blind hole, a pocket, a through hole, a through hole with a counterbore or chamfer at one or both ends, or a cutout of constant or varying cross section. One example of such a cutout is a through hole with or without a counterbore as an insert hole arrangement that secures the insert to the tool holder.

[0017] The laser beam used in laser processing is generated under laser processing variables by a laser system having a scanning unit as an optical system. The scanning unit may be configured as a movable unit. The laser beam may pass through a set of optical systems to shape it before reaching the scanning unit. The laser beam may extend in the scanning unit along a scanning axis. The laser beam is usually focused on the surface of the workpiece by a focusing lens arranged between the scanning unit and the workpiece. The scanning unit is configured to move the focal point of the laser beam, in particular in a plane in two or preferably three dimensions, and / or to perform a scanning movement over a desired area of ​​the workpiece, where the laser beam is refracted, diffracted and / or reflected by optical means of the scanning unit in order to achieve the movement over the surface of the workpiece. The scanning unit may be configured to provide an almost free three-dimensional orientation of the impact point of the laser beam and / or the focal point of the laser beam on the workpiece and thus on the processing space.

[0018] The method further includes the workpiece being supported and held by a holder and positionable relative to the scan axis. In addition to or in the alternative to controlled movement of the laser beam by the scanning unit, the holder may be configured to effect relative movement of the supported workpiece about at least one rotational axis and / or along at least one translational axis in a controlled manner relative to the scan axis. Because the laser beam is focused to a spot, relative motion between the laser beam and the workpiece is required to process the workpiece. The focal position of the laser beam on the workpiece may be controlled by moving one or both of the laser beam and the workpiece relative to one another. Since the movement of the laser beam by the movable scanning unit is faster than the movement of the holder by the machine axis, the relative motion during material removal is preferably achieved by controlled movement of the laser beam via the scanning unit.

[0019] Between the processing steps, the workpiece can be moved to a newly determined relative position by driving the laser processing device with translational and / or rotational motion. Alternatively, a combination of different motions (hybrid motions) can be used in which the workpiece is moved sequentially while the laser beam is scanned over it.

[0020] In one embodiment, the workpiece is moved in a controlled manner to determined relative positions about multiple axes (such as rotational A-axis, B-axis, and translational Z-axis) of the laser processing device. The scanning unit preferably includes three optical axes: X-axis, Y-axis, and Z-axis.

[0021] The laser processing method comprises a step a) of defining a processing volume of the workpiece. The processing volume may be determined by one or more characteristics such as a surface area, in particular an inlet perimeter, a bottom or ground or an outlet perimeter, and a depth or height, or by a lateral surface from the inlet perimeter to the bottom or outlet perimeter. In the following, a surface area characterizes a surface portion of the workpiece to be processed that is limited by a perimeter having a circle, an ellipse, an oval, a rectangle or a polygon, or any other closed shape. The processing volume may have a cylindrical or conical shape or any other suitable three-dimensional shape. In particular, the processing volume may have one or both of a perimeter value and a shape that vary over the depth. The surface area can be considered as the surface portion that is at least partially processed.

[0022] In the present invention, a first relative position between the processing volume and the scanning axis is determined. Preferably, the scanning axis in this step b) is arranged substantially perpendicular, i.e. normal, to the surface of the processing volume. By relative movement, the workpiece and / or the scanning axis are brought into the determined first relative position. Preferably, the workpiece is moved into the first relative position by controlled actuation of the machine axis.

[0023] In step c) of the laser processing method, the laser beam is applied to the workpiece in the surface area along a scanning axis, approximately perpendicular to the surface area. One or both of the laser beam and the workpiece are moved relative to each other, such that the laser beam moves along a first cutting path. In other words, the laser beam is scanned along the first cutting path in the surface area. The first cutting path can be configured such that, by suitable control of the relative motion, the surface portion to be processed can be traversed by the laser beam in different ways. For example, the laser beam can be scanned along a helical curve or in a path along regularly spaced parallel lines. Alternatively, the laser beam may be scanned along a curve or a series of parallel curves or a series of concentric circles with a certain offset between adjacent paths. Usually, in case of hole machining, the surface area is limited by a perimeter which is a closed curve, and in case of machining cylindrical holes, such perimeter curve is circular. In the present invention, the shape of this curve may include irregular shapes in case of a freely formed perimeter. Other scanning or cutting paths are also possible for this removal. Depending on the determined kerf and the machining strategy, it will be intended that a central part of the surface area remains unmachined.

[0024] The first and / or second cutting path may be determined by its shape, start and end points, and the direction in which the laser beam scans the surface portion. By varying the cutting path, a particular material removal rate can be optimized to ensure high speed processing.

[0025] The laser beam can be scanned several times across the surface area of ​​the cutout using various scanning motions to remove the processed volume and further removable processed volume in layers. Each subsequent scan of the laser beam may have an axial offset between scans, typically between 0.1 μm and 25 μm, depending on the material removed. Each subsequent scan of the laser beam may additionally have a lateral offset. In other words, the portion of the surface traversed by each subsequent scan is smaller than the previous scan. The lateral offset depends on the geometric characteristics of the feature being machined. By controlling other variables such as the scanning speed, the laser power, and either or both of the start and end points of the cutting path, the depth of material removal in any one scan can be controlled.

[0026] As a result of step d), the cutout in the machining volume has a first taper characteristic, which is influenced by the material properties, the processing variables and the machining volume and is typically greater than 5° and is determined experimentally. Taking this determined taper characteristic into account when determining the machining volume, here the first machining volume, is beneficial for the overall machining time.

[0027] The laser processing method according to the invention further comprises step e) determining a second processing volume with a first sidewall having a first taper characteristic and extending to a second sidewall having a predetermined characteristic. If the first cutout is a hole, the second processing volume will have approximately the shape of a ring. The predetermined characteristic may include a positive taper characteristic, a zero taper characteristic and a negative taper characteristic. Thus, the entrance diameter of the determined cutout to be processed configured as a hole can be larger, equal or smaller than the cutting diameter or the exit diameter in case of a through hole.

[0028] The determined second material volume is removed by relative positioning of the laser beam and / or the workpiece at a determined second relative position. Thus, the laser beam is directed onto the second processing volume under a predetermined tilt angle to irradiate the second processing volume while scanning the laser beam therethrough. Thus, the laser beam is focused under the laser processing variables on a surface portion of the second material volume to remove at least a portion of the second material volume to form a determined cutout having predetermined characteristics. Processing of the second processing volume may be performed by removing successive layers of material with multiple scans of the laser beam with axial and / or radial offsets between scans.

[0029] By repeatedly removing a machining volume with a laser beam extending in a first direction perpendicular to the surface of the workpiece and then removing a second volume of material with a laser beam oriented in a direction other than the first direction, in particular with a predetermined inclination angle, the overall machining speed can be optimized and predetermined characteristics of the side walls of the defined cutouts can be ensured.

[0030] Preferably, the predetermined tilt angle is greater than the divergence angle of the focused laser beam in the radial direction. The tilt angle depends on process variables and material properties and is determined by experiment. Typically, the tilt angle is between 3° and 15°, preferably between 5° and 10°.

[0031] In one embodiment, the laser processing method comprises, in step e), dividing the second processing volume into m sections, where m≧1. Preferably, m is between 1 and 4. In step f), a relative position between one of the m sections and a scanning axis is determined, and one or both of the section and the scanning axis are positioned at this relative position. In step g), the scanning axis is oriented on the section under a predetermined beam tilt angle, and a laser beam is scanned along a second cutting path to irradiate the section and remove material from the section to form a second sidewall of the section. Thus, each of these sections is machined until the predefined characteristics of that section are achieved before machining the next section. In this strategy, the relative position between the scan axis and the selected section remains at the previously determined relative position until the second side wall of that section has the predefined shape. Then, a new relative position is determined and, by relative movement of the workpiece and / or the scan axis, another section of the m sections is positioned at the newly determined relative position and machined. This procedure is repeated until each of the m sections has been machined to complete a defined cutout with predefined characteristics.

[0032] By dividing the second machining volume into m sections, each of the m sections can be machined separately until the second machining volume is removed, so that the machining speed and machining quality may be further optimized. By selecting an appropriate number of sections, each section can be machined at an appropriate tilt angle.

[0033] The selected and positioned sections of the m sections are machined by scanning the laser beam along a second cutting path in one or more scans with a second specific offset. The second cutting path may comprise one or both of a number of lines of the laser with a lateral offset between the lines and a second cutting pattern. Preferably, the second cutting path or pattern may be generated by offsetting a perimeter curve or a portion of a perimeter curve multiple times with a certain offset between each curve, where the surface of the machining volume to be removed is scanned. Typically, in case of hole machining, such a path is made on a portion of the perimeter of the hole, repeated and offset concentrically.

[0034] In another embodiment of the laser processing method, the processing volume determined in step a) is subdivided into n layers, each layer having a surface area, i.e. an individual circumference and thickness, limited by n≧1. Each of the n layers determines an individual processing volume that is removed by the described two-stage processing strategy. The value of n, the number of subdivided layers, depends on the depth or height of the processing volume to be removed. Preferably, n is between 2 and 10. Subdivision in n layers, which are subsequently processed, is advantageous with regard to the material removal rate, and thus the processing time, and the properties of the side walls of the cutout.

[0035] Each of the defined first processing volumes is processed in succession such that the laser processing variables can be adjusted individually for each of the n layers. Alternatively, each of the n layers may be processed under the same laser processing variables. Adjustable processing variables for each of the n layers ensure optimized processing through each of the n layers, especially for multi-layer materials. Material of the first processing volume can be removed in a series of processing steps (multiple) from the top surface of the workpiece downwards.

[0036] The thickness of each of the n layers processed may be selected to overcome the limitations of the material removal rate, which decreases as a function of depth into the workpiece. The thickness of each of the n layers may typically be between 0.1 mm and 2 mm, depending on the material properties and / or the geometric characteristics of the cutout as determined.

[0037] If the workpiece is a multi-layer substrate, the thickness of the at least one layer or each of the n layers may correspond to the thickness of the at least one layer or individual material layers. Alternatively, the thickness of at least one of the n layers is determined by the change in the processed material. In this case, the thickness of the layer is determined by detecting the change in the processed material, for example, by an external in-line or offline process control system. By selecting an appropriate thickness for each of the n layers and / or adjusting the laser processing variables in response to the detectable material changes, the material removal rate can be maximized during processing by optimizing the processing variables for processing each material.

[0038] The laser machining method (of the present application) allows the optimization of the laser machining process in terms of cycle time, throughput, flexibility and higher machining quality. In particular, a first direction of the laser beam, which is nearly perpendicular or perpendicular to the surface area while scanning the laser beam across the workpiece along the first cutting path, provides a certain high removal rate. However, potentially undesirable taper angles are generated, which can be adjusted by machining the second machining volume. Preferably, a first processing volume of a given n-layer is processed and a second processing volume of each of the n-layers is removed before processing another layer of the n-layer, thereby keeping the material removal rate at a nearly constant and high level. Removing material at the taper does not lead to absorption of laser energy when processing deeper structures, thus avoiding a decrease in material removal rate by scanning further down in the same direction. Furthermore, using this method, thermal effects can be reduced, improving the quality and reproducibility of the (laser) processing.

[0039] In one embodiment, the machining of the defined cutout is performed from the top side of the defined cutout and then from the bottom side of the defined cutout, with the cutouts from both sides joining to form a single through cutout. This method of machining from both sides allows the creation of cutouts with curved and tapered, circular or freely formed wall structures. This allows the machining speed to be optimized by further reducing the overall depth or by adapting the first cutting path to each layer of the n layers.

[0040] At the end of the determined cutout processing, a further step may be performed to finish the second sidewall of the cutout by laser processing. This finishing step improves the overall quality of the processed surface throughout the entire cutout depth. In one embodiment of the laser processing method, this finishing step comprises subdividing the surface to be processed into a plurality of sections and performing the laser processing with the scanning axis oriented at the determined second tilt angle. Alternatively, the laser processing may be performed with the scanning axis oriented at another determinable tilt angle.

[0041] Furthermore, the invention relates to a laser processing apparatus for laser processing defined cut-outs in a workpiece using the method according to the invention, which laser processing apparatus comprises: a laser system having a scanning unit used to move a laser beam in at least two coordinate directions, the laser system being configured to generate a laser beam along a scanning axis, direct the laser beam onto the workpiece substantially perpendicular to a surface area, and direct the laser beam onto the workpiece in a second cutting direction; A holding unit that supports and holds a workpiece and is movable around at least one rotation axis and / or along at least one translation axis by a drive unit of the laser processing apparatus; at least one control unit configured to scan the laser beam along the first cut-out path and the second cut-out path, determine n layers to be successively machined by scanning the laser beam along the first cut-out path and m sections to be machined by scanning the laser beam along the second cut-out path, and control the drive unit to move the workpiece to machine the determined cut-outs; Equipped with. The control unit may include any one of an appropriate processing device for settings that control the hardware and processing of the system, software for operating the laser processing device that executes the laser processing method, and a memory unit.

[0042] The laser processing machine may comprise one control for controlling the movement of the mechanical axis relative to the workpiece and the optical axis relative to the scanning unit. Alternatively, the laser processing machine may comprise one control configured to move the workpiece with respect to the mechanical axis and another control arranged to move the optical axis of the scanning unit so that the laser beam is directed towards the workpiece and scanned over the surface of the workpiece. Furthermore, the scanning unit of the laser processing machine may be configured to move the workpiece along and / or about the mechanical axis while keeping the workpiece positioned during processing. Alternatively, the scanning unit may remain positioned while the workpiece moves along and / or about the mechanical axis. Furthermore, the mechanical axis of the laser processing machine may be arranged to move the workpiece as well as the scanning unit for laser processing the workpiece according to the method of the invention. Effect of the Invention

[0043] For a more complete understanding of the present invention and its advantages, exemplary embodiments of the invention will be described in more detail in the following description with reference to the accompanying drawings, in which like reference characters indicate like parts and in which like reference characters indicate like parts: [Brief description of the drawings]

[0044] [Figure 1] FIG. 1 is a schematic diagram of an embodiment of a laser processing apparatus for carrying out a laser processing method according to the present invention. [Diagram 2] FIG. 2 is a schematic diagram of a first processing stage producing a first intermediate shape of the workpiece showing the relative positions between the laser beam and the workpiece. [Figure 3a] FIG. 3a is a schematic diagram showing a workpiece subdivided into layers in a first intermediate state. [Figure 3b] FIG. 3b is a schematic diagram showing the machining volume removed from the workpiece in a first machining stage. [Figure 4a] FIG. 4a is a schematic diagram of the workpiece processed in the second processing stage, showing the relative positions between the laser beam and the workpiece. [Figure 4b] FIG. 4b is a schematic diagram of a workpiece having a second intermediate shape. [Diagram 5] FIG. 5 is a schematic top view of the second processed volume, showing m sections into which the second processed volume is divided. [Figure 6] FIG. 6 is a schematic diagram of a workpiece in another intermediate state. [Figure 7a] FIG. 7a is a schematic top view showing a first cutting path of a first type. [Figure 7b] FIG. 7b is a schematic top view showing a second type of first cutting path. [Figure 7c] FIG. 7c is a schematic top view showing a third type of the first cutting path. [Figure 8] FIG. 8 is a schematic diagram showing an embodiment of the laser processing method according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0045] FIG. 1 shows a laser processing device 1 that may be used to implement the method according to the invention and that has been described in detail in FIG. 7. The laser processing device 1 has a laser 2, which may be of any suitable type depending on the application. The laser 2 emits a laser beam 20 that is processed by an optical system 3 depending on the determined laser parameters. The optical system 3 has optical components with lenses, filters and beam expanders. The optical system 3 may also have optical components with even complex assemblies with temporal and spatial beam sharpening optics. The laser beam 20 is then irradiated by a scanning unit 4 through focusing optics 5 onto a workpiece 10. The workpiece 10 is supported and held on a holder 11 or chuck that is attached to a motion stage 12. In this embodiment, the motion stage 12 is controlled by a control unit 6 and is movable along mechanical axes, such as one or both of a translation axis and a rotation axis.

[0046] In one embodiment, the motion stage 12 is configured to move the workpiece. The motion stage 12 in relation to the holder 11 or chuck includes: may be provided with an axis of rotation known as the A-axis and / or the B-axis; and May have linear axes for moving the workpiece into position and / or for moving the workpiece during laser processing Either or both of the above may be used. Any number of known designs may be used for the motion stage 12 to provide translational and / or rotational motion to the laser processing apparatus 1.

[0047] 1, the scanning unit 4 and / or the focusing optics 5 could be configured as movable units mounted on the second motion stage 13 such that they are movable along translational axes, such as the X-axis and the Y-axis, and optionally along one or both of the Z-axis and the rotational axis, such that the scanning unit 4 and / or the focusing optics 5 and the holder 11 are movable in one or both of the translational directions and around the rotational axes, respectively.

[0048] Another option is for the holder 11 to be mounted on a fixed base and for one or both of the scanning unit 4 and the focusing optics 5 to be movable by a corresponding motion stage 13 (not shown) controlled by the controller 6.

[0049] In FIG. 1, one controller 6 and central processing unit 8 (CPU8) are provided to control the movement of the workpiece by the motion stage 12, and also to control the scanning unit 4, and one or both of the laser 2 and the optical system 3. The controller 6 and optional further controller 7 (not shown) may generally comprise a CPU 8, a memory, and support circuitry. The CPU may be any type of computer processor used in laser processing machines for control of the machine hardware and processing. The memory may be connected to the CPU 8 and may be one or more of readily available memory such as random access memory (RAM), read only memory (ROM), and other forms of local or remote digital storage. Software instructions and data may be coded for the instruction of the CPU 8 and stored in the memory. Command signals are generally output based on programming instructions stored in the memory, and the function of each programming instruction is carried out by the logic of the CPU 8. Various elements of the laser processing machine may include their own controllers that transmit data to and from the main controller along communication paths.

[0050] Preferably, the control unit 6 is adapted to control one or both of the motion stages 12 and the further motion stage 13 to provide a relative movement between the scanning unit 4 and the workpiece 10, and to control the axial movement of the scanning unit 4 to control the movement of the laser beam. In another embodiment, the control for the relative positioning of the scanning unit 4 and the workpiece 10 and the control of the axial movement of the scanning unit 4 are separate. A further control unit 7 may be provided to control the axis of the scanning unit 4 to control the movement of the laser beam, while the control unit 6 controls only one of the motion stages 12, additionally or alternatively the motion stage 13.

[0051] FIG. 2 is a schematic diagram of a workpiece 10. The workpiece 10 has a depth d (e.g., 5 mm) extending from a surface 21. FIG. 2 shows an exemplary workpiece 10 after material has been removed by orienting and scanning a laser beam 20 along a first cutting path 29 (not shown) to form a blind hole or first cutout 25. The laser beam 20 is directed by a scanning unit 4 and a focusing lens 5 to a scanned surface 21 with a scanning axis 34 normal or close to normal to the surface 21. A machining volume is removed by scanning the laser beam 20 in a spiral, or in a series of parallel lines, or along another scanning path such that the material volume is removed in layers. The scanning paths could have axial and lateral offsets between each scan.

[0052] 2, the first cutout 25, or blind hole in this case, has a first taper feature 23 including a taper angle α corresponding to the angle between the inner wall of the first cutout 25 and the normal to the surface 21. The taper angle α resulting from such machining using the scanning unit 4 is typically between 5° and 20°.

[0053] In one example shown in FIG. 3a, the depth d of the workpiece 10 is subdivided into n layers, the number of n layers depending on the depth d and the constraints of the laser processing. In the example of FIG. 3a, n is 4. Each layer n1, n2, n3, n4 may have an individual thickness t ranging from 0.1 mm to 2 mm, typically about 1 mm. After processing the processing volume 22 (shown in FIG. 3b) of the first layer n1, the first cutout 25 has a first taper characteristic 23 including a structure sidewall 24 that is linear, concave or convex. The first taper characteristic 23 may vary depending on at least one of the material properties, the process variables and the processing volume 22. The second processing volume 26, shown in FIG. 3a by hatching changes, has a first sidewall 24 and a second sidewall 27 and is processed in the next processing step shown in FIG. 4a.

[0054] When machining a through hole in the workpiece 10, the laser beam 20 does not need to be scanned over the entire surface 21 of the machining volume to be removed, in order to have a faster machining process. A central portion may be left behind which is removed by dropping off when the through hole is completed.

[0055] FIG. 3b is a schematic diagram illustrating a removed material volume 22 of a first layer n1 removed from an exemplary workpiece 10 in a first processing stage.

[0056] Figure 4a is a schematic diagram of the workpiece 10 illustrating a machining step to remove a defined second machining volume 26 (not shown). The second machining volume 26 can be defined by a first sidewall 24 having a first taper characteristic 23, or a defined second sidewall 27 including the first sidewall 24 and having a predetermined characteristic 28, as shown in Figure 4b. Preferably, the predetermined characteristic 28 has a zero taper angle such that the second sidewall 27 (not shown) extends perpendicularly from the surface 21 of the workpiece 10.

[0057] The second machining volume 26 can be removed by relative positioning of one or both of the laser beam 20 and the workpiece 10 at a second predetermined relative position. The scanning axis 34 is oriented under a predetermined tilt angle β to machine the second machining volume 26, and the laser beam 20 is scanned therethrough to irradiate the second machining volume 26. After machining the first layer n1, a blind hole with zero taper is produced, as shown in FIG. 4b.

[0058] FIG. 5 shows in a schematic top view the second processing volume 26 to be removed. This illustrated second processing volume 26 is in this case limited by or includes a first sidewall 24 with a first tapered characteristic 23 and a second sidewall 27 with a predetermined characteristic 28, and extends into the processing volume 22 or the thickness t of the layer to be processed. The second processing volume 26 is subdivided into m sections. Depending on the shape and / or dimensions of the second processing volume 26, the number "m" may vary between 1 and 6, and is preferably approximately 4. Each of the m sections is laser processed by relative positioning one of the m sections and the scanning axis 34 in a predetermined relative position and scanning the laser beam 20 along the second cutting path 36 to irradiate the section. In this embodiment, the second cutting path 36 has parallel straight lines, but can have other configurations. Each of the m sections may be processed until the second characteristic 28 of this section is achieved before repositioning the workpiece 10 and / or the scanning unit 4 to process another section of the m sections. Alternatively, the laser beam 20 is scanned over all m sections to remove the second processing volume 26 layer by layer. The scanning direction and scanning geometry of the second cutting path 36 may be changed.

[0059] 6 is a schematic illustration of a workpiece 10 with another intermediate shape, showing the workpiece 10 after machining a first layer n1 and after carrying out a first step of machining a second layer n2, in which a machining volume 22 of this second layer n2 is removed, whereby the second layer n2 comprises a first sidewall 24 with a first taper characteristic 23. The first taper characteristic 23 of the second layer n2 may differ from the first taper characteristic 23 of the first layer n1, such that another taper angle α is formed.

[0060] 7a, 7b and 7c each show a top view of the workpiece 10, in particular showing a first cutting path 29, in which the laser beam 20 is scanned over the surface 21 to be machined. The cutout 25 depicted in FIG. 7a is a hole with a circular surface area 30 limited by a perimeter 31. In FIG. 7a, the laser beam 20 is scanned across the surface portion to be machined in a spiral path with a specific distance between adjacent loops. The first cutting path 29 may vary from scan to scan in terms of scanning speed, laser power and other variables, such as the start and / or end point positions and other variables such as the scanning direction. As shown in FIG. 7a, the central portion remains unmachined after machining.

[0061] Figure 7b shows an alternative configuration for the first cutting path 29 formed as a spiral path with each scan beginning and / or ending at the centre 32 or periphery 31. As shown in Figure 7b, no central portion remains unmachined after machining.

[0062] 7c shows another first cutting path 29 configured as a repetition of parallel straight lines. The first cutting path 29 may be designed to optimize the material removal rate. In this embodiment, the central portion is also machined in the same way.

[0063] 8 illustrates an exemplary laser processing method 100 for forming a defined cutout in a workpiece 10, according to at least one embodiment. The exemplary method includes relative positioning 102 of the workpiece 10 held in a holder 11 and a laser beam 20 propagating through a scanning unit 4 and collection optics 5. The laser processing method 100 further includes, in operation 104, determining a processing volume of the workpiece comprising a surface area 30 bounded by a perimeter 31 and a depth d, and subdividing the processing volume into n layers according to one embodiment. Each layer is defined by an individual surface area 30 and a predetermined thickness t, which defines the machining volume 22. Depending on the depth d of the machining volume in one embodiment, n may be 1 such that the machining volume 22 corresponds to the machining volume of the layer. Additionally, one or more characteristics of the defined cutout 25 may be determined, such as the top perimeter 31, the bottom perimeter, the first taper characteristic 23, etc., corresponding to the cutout opening. The exemplary method 100 further includes an operation 106 of determining a first relative position between one of the n layers to be processed (hereinafter referred to as "layer n1") and the scanning axis 34 by controlled movement of the workpiece 10 by one or both of the motion stage 12 and the scanning unit 4 and the focusing optics 5. In this relative position, the scanning axis 34 is oriented approximately perpendicular to the surface 21 of the layer n1. In an operation 108, the laser beam 20 emitted from the laser 2 under the laser processing parameters is focused on the surface 21. This operation 108 includes scanning the laser beam 20 along a first cutting path 29 within a surface area 30 limited by the outer periphery 31 of the layer n1. This operation allows removing the processing volume 22 of this layer by multiple scanning of the laser beam 20 across the surface area 30. In each scan, a material layer in the range of 0.1 μm to 25 μm is removed.

[0064] The method 100 further includes an operation 110 of determining a second machining volume 26 between the first sidewall 24 formed in the operation section 108 and a predetermined second sidewall 27 that at least partially corresponds to a sidewall of the determined cutout to be machined. This operation 110 may include that the second machining volume 26 is virtually subdivided into m sections that can then be machined.

[0065] Operation 112 includes determining a second relative position between the second processing volume 26 and the scan axis 34 and repositioning one or both of the workpiece 10 and the scan axis 34 to the second relative position. In operation 112, the laser beam 20 is directed onto the second processing volume under a predetermined tilt angle β, and laser processing variables can be adjusted based on one or more characteristics of the method 100. In some embodiments, the laser processing variables can include laser power, focal beam diameter, focal height, beam spot size, offset of the laser beam 20 from a previous scan, and / or combinations thereof.

[0066] The method 100 includes an operation 114 in which at least a portion of the second processing volume 26 is removed under the adjusted laser processing variables. According to the method 100, each of the m sections of the second processing volume 26 is processed, including repositioning the workpiece 10 and the scanning axis 34, so that optimal laser processing conditions are achieved for processing each section. After the second processing volume 26 of the layer n1 is removed, the method 100 includes repeating operations 106 to 114 until the cutout in the workpiece 10 reaches a determined shape. In one embodiment, the method 100 further includes another operation 116 of finishing the formed sidewall of the cutout.

[0067] The invention is not limited to the described embodiments, which may be modified in construction and detail.

Claims

1. - generating a laser beam (20) propagating in the scanning unit (4) along a scanning axis (34); providing a workpiece (10) supported and held in a holding part (11) and positionable relative to said scanning axis (34); A method (100) for laser machining a defined cut-out into a workpiece (10), comprising: a) determining a machining volume (22) of said workpiece (10) having a surface area (30) and a depth (d); b) determining a first relative position between the processing volume (22) and the scanning axis (34), in which the scanning axis (34) is oriented substantially perpendicular to the surface (21) of the processing volume (22); and positioning one or both of the workpiece (10) and the scanning axis (34) at the first relative position; c) directing the laser beam (20) at the machining volume (22) within the surface area (30) and causing a relative motion between the workpiece (10) and the laser beam (20) to scan the laser beam (20) along a first cutting path (29); d) removing at least a portion of said processed volume (22) to form a first cutout (25) having a first sidewall (24) with a first tapered characteristic (23); e) determining a second machining volume (26) including said first sidewall (24) and partially bounded by a second sidewall (27) having a predetermined characteristic (28); f) determining a second relative position between the second machining volume (26) and the scan axis (34) and positioning one or both of the workpiece (10) and the scan axis (34) at the second relative position; g) orienting the scanning axis (34) relative to the workpiece (10) at a predetermined inclination angle (β), applying the laser beam (20) to the second machining volume (26), scanning the laser beam (20) along a second cutting path (36) and removing at least a portion of the second machining volume (26) to form a second sidewall (27); The method (100) of laser machining a defined cut-out into a workpiece (10) further comprises:

2. In step e), said second processed volume (26) is divided into m sections, m≧1, preferably between 1 and 4; In step f), a relative position between one of the m segments and the scanning axis (34) is determined, and one or both of the segment and the scanning axis are positioned at this relative position; In step g), the scanning axis (34) is oriented under a predetermined inclination angle (β) on the section, and the laser beam (20) is scanned along the second cutting path (36) to irradiate the section and remove material from the section to form the second side wall (27) of the section; repeating steps e) to g) until the material of the second processing volume (26) is removed.

2. The method of claim 1 (100).

3. The machining volume (22) of the workpiece (10) determined in step a) is subdivided into n layers, Each layer is determined by a surface area (30) limited by a perimeter (31) and a thickness (t), where n>1; Each of the n layers determines an individual processing volume (22) of the layer to be processed according to steps b) to d); The method comprises repeating steps b) to g) until the cutout in the workpiece (10) reaches a determined configuration.

3. The method (100) of claim 1 or 2.

4. The method (100) of claim 3, wherein the thickness (t) of at least one of the n layers is determined by a detected change in material.

5. 5. The method (100) according to any one of claims 1 to 4, wherein the determined cut-out in the workpiece (10) is one of a blind hole, a through hole, a through hole with a counterbore at one or both ends of the through hole, and a cut-out with a constant or different cross-section.

6. The method (100) of any one of claims 1 to 5, wherein the predetermined characteristics (28) include a positive taper characteristic, a zero taper characteristic, and a negative taper characteristic.

7. 7. The method (100) of any one of claims 3 to 6, wherein a thickness (t) of each of the n layers is between 0.5 mm and 2 mm.

8. 8. The method (100) of any one of claims 3 to 7, wherein material from each of the n layers is removed by repeating a scan of the laser beam (20) with an axial offset in the direction of the scanning axis (34) between scans of between 0.1 μm and 25 μm.

9. the first cutting path (29) has a spiral shape extending in opposite directions from the outer periphery (31) of the surface area (30) to the center (32) of the surface area (30); or The method (100) according to any one of the preceding claims, wherein the first cutting path (29) is a series of offset curves around at least a portion of the periphery (31).

10. The method (100) of any one of claims 1 to 8, wherein the first cutting path (29) is a pattern of one or both of a plurality of lines and a plurality of intersecting lines with lateral offset between the intersecting lines.

11. 11. The method (100) according to any one of claims 1 to 10, wherein the predetermined tilt angle (β) is greater than the divergence angle of the laser beam and is typically in the range of 3° and 15°.

12. 12. The method (100) according to claim 1 or claims 3 to 11, wherein the second machining volume (26) is machined layer-by-layer by multiple scans of the laser beam (20) with axial offset until the predetermined characteristic (28) is achieved.

13. 12. The method (100) according to any one of claims 2 to 11, wherein each of the m sections of the second processing volume (26) is processed until a predetermined characteristic (28) of the section is achieved before a next section of the m sections is processed.

14. the machining of the determined cutout is performed from the top of the determined cutout; 14. The method (100) according to any one of claims 1 to 13, and then from a bottom of the determined cutout, a plurality of said cutouts are joined to form a single cutout.

15. A laser processing device (1) for laser processing a defined cut-out into a workpiece (10) using the method according to any one of claims 1 to 14, comprising: a laser system having a scanning unit (4) with at least one optical axis and at least one mechanical axis configured to generate a laser beam (20) along a scanning axis (34), to orient the laser beam (20) on the workpiece (10) in a first cutting direction substantially perpendicular to a surface (21) of the workpiece, and to orient the laser beam (20) on the workpiece (10) in a second cutting direction; a holding part (11) for supporting and holding the workpiece (10), which is movable around at least one rotation axis and / or along at least one translation axis by a drive unit of the laser processing device (1); In a laser processing apparatus (1), moving the workpiece (10) along a second cutting path (36) and / or controlling the laser processing device (1) along at least one machine axis to process the defined cutout; Laser processing equipment (1).

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