Laser processing method and apparatus

Abstract

A method and apparatus for laser machining a defined cut portion in a workpiece includes: generating a laser beam propagating through a scanning unit along a scanning axis; arranging a workpiece supported and held in the bracket; defining a machining volume of the workpiece having a surface area and a depth; determining a first relative position between the machining volume and the scan axis; directing a laser beam into the surface region on the machining volume, causing a relative movement between the workpiece and the laser beam; removing the first machining volume such that the first cut portion has a first sidewall; defining a second processing volume including the first sidewall and partially bounded by a second sidewall having a predetermined feature; determining a second relative position between the second machining volume and the scan axis; and orienting the scan axis relative to the workpiece at a predetermined tilt angle, directing the laser beam onto the second machining volume, scanning the laser beam along a second cutting path, and removing at least a portion of the second machining volume to form a second sidewall.

Description

Technical Field

[0001] The present invention relates to a laser processing method and apparatus, in particular for forming zero-taper and / or predetermined-taper machining cuts, cutouts and / or holes in a workpiece. Background Art

[0002] It is well known that machining workpieces of hard and / or brittle materials, such as metals (such as stainless steel), light metals (such as titanium, magnesium and aluminum), or ceramics, cermets, tungsten carbide, PCD diamond, CVD diamond, PCBN, etc., with or without coatings is difficult. For example, drilling holes in indexable inserts made of superhard materials, such insert hole arrangements including holes with or without one or two counterbores to allow the insert to be fixed to the tool holder, is a challenge. Although it is generally known to use laser machining methods and equipment to machine these workpieces, methods for drilling zero-taper holes in indexable inserts using scanning units are not widely known.

[0003] It is known to use drilling or cutting lasers to drill holes in these workpieces, including high-precision drilling or cutting. Laser drilling or cutting has the advantages of high speed and high flexibility, and can drill through holes and holes with complex shapes or can perform high-precision cutting. Compared with traditional drilling methods using twist drills, laser drilling or cutting is cheaper in the case of hard materials and / or small holes to be processed due to the non-contact processing and avoidance of wear on the processing tool.

[0004] In laser machining, a laser beam generating device is used in combination with an optical system to direct the laser beam onto the workpiece to be machined. The laser beam impinging on the workpiece locally melts, evaporates and / or ablates the workpiece material to produce or extend a hole or cutout in the workpiece. The position of the impingement point on the workpiece is controlled by moving one or both of the laser beam and the workpiece relative to each other, thereby controlling the geometry of the hole or cutout. It is well known that laser machining of holes produces a tapered hole whose entrance diameter is larger than the ground diameter of the hole, or even larger than the exit diameter in the case of a through hole.

[0005] High-precision and deep laser drilling can be performed by means of trench drilling or spiral drilling. Trench drilling or spiral drilling uses a special optic that allows the incident angle of the laser beam to be changed and the laser beam to be moved at high speed along a rotating path. The workpiece remains stationary. Both processes require a complex optical setup to control the taper angle of the hole. Therefore, laser processing of holes without taper angles by these methods involves specific and complex equipment and methods that can only be used for drilling and not for other laser processing processes. These well-known methods are usually implemented on dedicated equipment and cannot be implemented on conventional laser processing equipment using scanning units.

[0006] Another method to avoid undefined or unselected tapered edges is to physically move the workpiece, in particular to move the holding or clamping device that supports the workpiece, while keeping the laser beam at the same angle of incidence. This method requires high-precision translation and / or rotational movement of the workpiece by the laser processing equipment around typically 4 or even 5 axes and complex control software to achieve zero taper or defined tapered edges. Furthermore, additionally or alternatively, the laser system (in particular the scanning unit) can be moved relative to the workpiece.

[0007] It is known from document US2014263212 that laser systems and methods are used for machining features in workpieces. Specifically, beam coordination is described to control the taper of the cut or slit formed in the workpiece. In order to produce the desired conical features on the side walls of the slit by a focused laser beam propagating along the beam axis, the incident angle and azimuth of the beam axis can be moved relative to the workpiece. During the cutting process, when the laser beam actively processes the workpiece, especially when the workpiece is irradiated along the cutting path, both the workpiece and the beam axis move relative to each other. According to the document, two linear axes are used to deviate the machining point from the center, thereby forming a defined angle of incidence of the beam on the machining surface. Since the speed of these axes is slower than that of the optical axis, and in order to obtain the desired angle of incidence, the workpiece to be machined needs to be moved over a long distance, the machining speed is slow.

[0008] From the document US20120132629, it is known that a method and apparatus for reducing the taper in the slit produced by a laser process or scribing. The method is based on strategic laser positioning for reducing the taper of the scribing or cut. Therefore, the method includes aiming the laser beam onto the substrate surface along a first cutting direction and tilting the laser beam at an inclination angle, further aiming the laser beam onto the substrate surface along a second direction perpendicular to the first cutting direction, and tilting the laser beam at an inclination angle. The cut is formed by applying the laser beam to the surface of the substrate while aiming the laser beam and cutting in the first cutting direction, and applying the laser beam to the surface of the substrate while aiming the laser beam in the second direction and cutting in one of the first cutting direction and the second cutting direction opposite to the first cutting direction. The method requires special equipment for tilting the beam, which means a loss of flexibility and a reduction in processing speed.

[0009] Therefore, one object of the present invention is to provide a laser processing method and apparatus, by means of which a defined cutting portion, a large and deep hole and / or a cutout can be produced in a high-quality component at a zero cone angle and / or a predetermined cone angle (particularly a negative cone angle). The laser processing apparatus can use a scanning unit, so that the processing capacity and output become high. Another object is to provide a laser processing method and apparatus, which eliminates post-processing and cleaning operations, improves repeatability, reliability, speed and precision, thereby reducing manufacturing costs. In addition, this laser processing method provides process flexibility, high cutting rate and non-contact operation. Summary of the invention

[0010] According to one aspect of the present invention, there is provided a method for laser machining a defined cutting portion in a workpiece, comprising:

[0011] - generating a laser beam propagating through a scanning unit along a scanning axis,

[0012] - providing a workpiece, which is supported and held in a holder and can be positioned relative to the scanning axis,

[0013] The method further comprises the steps of:

[0014] a) define the machining volume of the workpiece with surface area and depth,

[0015] b) determining a first relative position between the machining volume and the scanning axis, wherein the scanning axis is oriented substantially perpendicular to the surface area of ​​the machining volume, and positioning the workpiece and / or the scanning axis in the first relative position,

[0016] c) directing a laser beam onto a processing volume, causing a relative movement between the workpiece and the laser beam in the surface area thereof, and causing the laser beam to scan along a first cutting path,

[0017] d) removing at least a portion of the machined volume to form a first cut portion having a first sidewall having a first tapered feature,

[0018] e) defining a second processing volume including the first sidewall and defined by a second sidewall having a predetermined characteristic,

[0019] f) determining a second relative position between the second machining volume and the scanning axis and positioning the workpiece and / or the scanning axis in said second relative position, and

[0020] g) orienting the scan axis at a predetermined tilt angle β relative to the workpiece, directing the laser beam onto a second processing volume, scanning the laser beam along a second cutting path, and removing at least a portion of the second processing volume to form a second sidewall.

[0021] According to the invention, the method uses a combination of at least two different machining strategies. With a first machining strategy, the laser beam is irradiated at an angle of incidence close to 0°, i.e. normal to the surface of the workpiece to be machined, i.e. normal to the top surface defining the machining volume, resulting in a high material removal rate, but producing tapered features. In a second strategy, the laser beam is irradiated at a larger angle of incidence, typically greater than 80°. With this high angle of incidence, the material removal rate is lower than with the first strategy. However, a high surface quality can be achieved and the undesired taper angle caused by the first strategy can be removed.

[0022] In addition, the method solves the problem of taper angle generated by laser processing using a scanning unit and the problem of reducing the specific material removal rate by forming a deep cut portion. By using multiple steps in the depth direction, the method allows the scanning cut portion feature to be controlled by repeated scanning or repeated passes of the laser beam for complete removal of material.

[0023] The cone angle of the cut side that can be obtained using the scanning unit is typically >5°. This is because the laser intensity decreases when projecting onto the inclined ablation side, with the result that ablation stops at the critical angle. Unlike conventional laser drilling methods using scanning units, the method described herein enables the formation of cut parts with predetermined cone angles and quality parameters such as inlet geometry, ground or outlet geometry, contour accuracy and surface features. Using the proposed laser processing method, holes with a positive cone (i.e. a positive cone), a cylindrical shape, and a negative cone (i.e. a negative cone) as well as holes in the shape of a hole funnel, an hour-shaped hole or a Laval nozzle can be produced.

[0024] The laser machining method is preferably configured for laser machining workpieces made of hard, superhard and / or brittle materials, for example for indexable inserts or workpieces comprising a multilayer substrate comprising a plurality of layers of different materials and / or different heights.

[0025] According to one embodiment, the machined cut portion or structure in the workpiece is a blind hole, a through hole, a through hole with a countersink or chamfer at one or both ends of the through hole, or a cut portion of constant or varying cross section. An example of such a cut portion is a through hole with or without a countersink as an insert hole arrangement allowing an insert to be fixed to a tool holder.

[0026] The laser beam used for laser processing is generated by a laser system having a scanning unit as an optical system under laser process parameters. The scanning unit can be configured as a movable unit. The laser beam is shaped by passing through a set of optical devices before reaching the scanning unit. The laser beam can extend through the scanning unit along the 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 focus of the laser beam in one plane, in particular in 2D, or preferably in 3D and / or across the entire desired area of ​​the workpiece for scanning. In this case, the laser beam is refracted, diffracted and / or reflected by the optical components of the scanning unit to achieve its movement on the surface of the workpiece. The scanning unit can be configured to provide the irradiation point and / or focus of the laser beam to the workpiece, and thus provide a largely free three-dimensional orientation on the processing space.

[0027] Furthermore, the method comprises that the workpiece is supported and held in a support and can be positioned relative to the scanning axis. Additionally or alternatively, in addition to the controlled movement of the laser beam by means of the scanning unit, the support can be configured to move the supported workpiece relative to the scanning axis in a controlled manner around at least one rotation axis and / or along at least one translation axis. The laser beam is focused on a point, so that a relative movement between the laser beam and the workpiece to be processed is required to process the workpiece. The position of the laser beam focus on the workpiece can be controlled by moving one or both of the laser beam and the workpiece relative to each other. Since the laser beam moves faster through the movable scanning unit than the support moves through the device axis, the relative movement during the removal of material is preferably performed by controlled movement of the laser beam via the scanning unit.

[0028] Between processing steps, the workpiece can be moved to a newly defined relative position by movement of the drive of the laser processing device in translation and / or rotation. Alternatively, a hybrid motion can be used with a laser beam scanning across the workpiece while moving the workpiece sequentially.

[0029] According to one embodiment, the workpiece is moved in a controlled manner to a determined relative position around multiple axes of the laser machining device, such as rotational A and B axes and translational Z axis. The scanning unit preferably comprises three optical axes, X axis, Y axis and Z axis.

[0030] The laser processing method comprises the step a) of defining a processing volume of the workpiece. The processing volume can be determined by one or more characteristics, such as the surface area, in particular the inlet perimeter, the bottom or ground or the outlet perimeter and the depth or height, or by the side surface from the inlet perimeter to the bottom or outlet perimeter. In the following, the surface area characterizes the surface portion of the workpiece to be processed which is defined by a perimeter having a circular, oval, elliptical, rectangular or polygonal shape or any other closed form. The processing volume can have a cylindrical or conical shape or any other suitable three-dimensional shape. In particular, the perimeter value and / or shape of the processing volume over the entire depth can vary. The surface area can be regarded as the surface portion to be at least partially processed.

[0031] According to the invention, a first relative position between the machining volume and the scanning axis is determined. Preferably, the scanning axis in step b) is oriented substantially vertically, i.e. orthogonally to the surface of the machining 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 activation of the device axis.

[0032] In step c) of the laser processing method, a laser beam is guided into the surface region of the workpiece along a scanning axis that is substantially perpendicular to the surface region. One or both of the laser beam and the workpiece are moved relative to each other so that the laser beam moves along a first cutting path. In other words, the laser beam scans along a first cutting path in the surface region. The first cutting path can be configured so that the laser beam can pass through the surface portion to be processed in different ways by appropriate control of relative motion. For example, the laser beam can scan along a spiral curve or along a path of regularly spaced parallel lines. Alternatively, the laser beam can scan along a curve or a series of parallel curves or a series of concentric circles with a specific offset between adjacent paths. Typically, when processing a hole, the surface region is limited by the circumference of a closed curve, and in the case of processing a cylindrical hole, this circumference curve is circular. According to the present invention, in the case of a freely formed circumference, the shape of the curve may also include an irregular shape. Other scanning or cutting paths may also be used for such removal. Depending on the defined cutting portion and the processing strategy, the central portion of the surface region may remain unprocessed.

[0033] The first cutting path and / or the second cutting path may be defined by its shape, starting and ending points, and the direction in which the laser beam is scanned across the surface portion. Changing the cutting path may optimize a specific material removal rate and ensure high-speed machining.

[0034] In order to process the processing volume and to process additional volumes, the laser beam may be scanned multiple times across the surface area of ​​the entire cut portion using various scanning motions so that the processing volume and any other removable processing volume can be removed in layers. Each subsequent scan of the laser beam may typically have an axial offset of 0.1 μm to 25 μm between multiple scans, depending on the material removal. Each subsequent scan of the laser beam may have an additional lateral offset. In other words, the portion of the surface to be scanned by the subsequent scan is smaller than the previous scan. The lateral offset depends on the geometric characteristics of the structure to be processed. By controlling the scanning speed, laser power and other parameters, such as the starting and / or end point of the cutting path, the depth of material removal in any one scan can be controlled.

[0035] The result of step d) is that the cut portion in the machining volume has a first tapered characteristic. The first tapered characteristic is influenced by the material properties, the machining parameters and the machining volume and is generally greater than 5°. This can be determined experimentally. When defining the machining volume, the so-called first machining volume, it is beneficial to take into account this determinable tapered characteristic for the entire machining duration.

[0036] The laser processing method according to the present invention further comprises the step e) defining a second processing volume, the second processing volume comprising a first side wall having a first tapered feature and extending to a second side wall having a predetermined feature. In the case where the first cutting portion is a hole, the second processing volume may have an approximately annular shape. The predetermined feature may include positive, zero and negative tapered features. Therefore, the entrance diameter of the defined cutting portion to be processed (configured as a hole) may be greater than, equal to or less than the grounding diameter in the case of a through hole or even less than the exit diameter.

[0037] The defined 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 can be directed to the second processing volume at a predetermined inclination angle and irradiated while the laser beam is scanned across the second processing volume. Thus, the laser beam is focused on a surface portion of the second material volume with laser process parameters to remove at least a portion of the second material volume, thereby forming a defined cut portion with predetermined characteristics. The processing of the second processing volume can be performed by multiple scans of the laser beam with an axial offset and / or a radial offset between the multiple scans to continuously remove material layers.

[0038] By repeatedly removing a machining volume with a laser beam extending in a first direction perpendicular to the workpiece surface and then removing a second material volume with a laser beam oriented in another direction than the first direction (particularly at a predetermined inclination angle), the overall machining speed can be optimized and predetermined features of the side walls defining the cut portion can be ensured.

[0039] Preferably, the predetermined tilt angle is greater than the radial laser beam divergence angle of the focused laser beam. The tilt angle depends on process parameters and material properties and can be determined experimentally. Typically, the tilt angle is between 3° and 15°, preferably between 5° and 10°.

[0040] According to one embodiment, the laser processing method comprises, in step e), dividing the second processing volume into m sections, and m≥1. Preferably, m is between 1 and 4. In step f), the relative position between one of the m sections and the scanning axis is determined, and the section and / or the scanning axis is positioned in the relative position, and in step g), the scanning axis is directed to the section at a predetermined beam inclination angle, the section is irradiated by scanning the laser beam along the second cutting path, and material is removed from the section to form the second side wall of the section. Thus, before processing the next section, each of the sections is processed until the predetermined features of the section are obtained. In this strategy, the relative position between the scanning axis and the selected section is maintained at the previously determined relative position until the second side wall of the section becomes a predetermined shape. The relative position is then re-determined, and another of the m sections is positioned at the newly determined relative position to be processed by the relative movement of the workpiece and / or the scanning axis. This process is repeated until each of the m sections is processed and a defined cutting portion with predetermined features is completed.

[0041] Dividing the second machining volume into m segments enables each of the m segments to be machined separately until the second machining volume is removed, which can further optimize machining speed and quality.By selecting a suitable number of segments, each segment can be machined at a suitable tilt angle.

[0042] A selected and positioned segment of the m segments is 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 include multiple laser lines with lateral offsets between the laser lines and / or may include a second cutting pattern. Preferably, the second cutting path or pattern may be generated by multiple offsets of a perimeter curve or a portion of a perimeter curve, wherein each curve has a fixed offset between the surfaces of the machined volume to be removed being scanned. Typically, when machining a hole, such a path consists of a segment of the perimeter of the hole, repeated, offset in a concentric manner.

[0043] According to another embodiment of the laser machining method, the machining volume defined in step a) is subdivided into n layers, each layer having a surface area, i.e. a separate surface area defined by a separate perimeter and a thickness, and n≥1. Each of the n layers defines a separate machining volume to be removed by the two-step machining strategy. The value of n (the number of subdivided layers) depends on the depth or height of the machining volume to be removed. Preferably, n is between 2 and 10. Subdividing and subsequently machining n layers is advantageous in terms of material removal rate, and therefore also in terms of machining time and sidewall characteristics of the cut portion.

[0044] Each defined first processing volume is processed successively so that the laser processing parameters can be adjusted individually for each of the n layers. Alternatively, each of the n layers can be processed with the same laser processing parameters. The adjustable process parameters for each of the n layers can ensure optimal processing of each of the n layers (especially in the case of multilayer materials). The material of the first processing volume can be removed downward from the top surface of the workpiece in a subsequent processing step.

[0045] The thickness of each of the n layers to be machined may be selected to overcome limitations in material removal rate, which decreases with 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 geometrical properties defining the cut portion.

[0046] In the case where the workpiece is a multilayer substrate, the thickness of at least one or each of the n layers may correspond to the thickness of at least one or each individual material layer. Alternatively, the thickness of at least one of the n layers may be determined by changing the material being processed. In this case, the thickness of the layer is determined by detecting changes in the material to be processed, for example by an external online or offline process control system. By selecting a suitable thickness for each of the n layers and / or adjusting the laser processing parameters according to the detectable material changes, a maximum material removal rate can be maintained throughout the entire processing process by optimizing the process parameters for processing each material.

[0047] Using the laser machining method, the laser machining process is optimized in terms of cycle time, output, flexibility and higher machining quality. In particular, a laser beam is scanned in a first direction substantially perpendicular or orthogonal to the surface area while traversing the workpiece along a first cutting path, and a specific high removal rate can be achieved. However, an undesirable cone angle may result, which can be adjusted by machining a second machining volume. Preferably, a first machining volume of a defined n layers is machined and a second machining volume of each of the n layers is removed before machining another layer of the n layers, keeping the material removal rate substantially constant and at a high level. By removing the tapered material, it does not contribute to the absorption of the laser energy during the machining of deeper structures. Therefore, a reduction in the material removal rate due to further downward scanning in the same direction is avoided. In addition, using this method, thermal effects can be reduced and the quality and repeatability of the machined cut parts can be improved.

[0048] In one embodiment, multiple cuts are joined together from both sides to form a single through cut, from the top side of the defined cut and subsequently from the bottom side. This strategy of machining from both sides enables the formation of cuts of curved, tapered, rounded or free-formed wall structures. In this way, the machining speed can be optimized due to a further reduction in the overall depth and / or by adapting the first cutting path for each of the n layers.

[0049] At the end of machining the defined cut portion, a further step can be performed for finishing the second side wall of the cut portion by laser machining. This finishing step improves the overall quality of the machined surface over the entire depth of the cut portion. According to one embodiment of the laser machining method, the finishing step comprises subdividing the surface to be machined into a plurality of sectors and performing the laser machining with a scanning axis oriented at a defined second inclination angle. Alternatively, the laser machining can be performed with the scanning axis oriented at another definable inclination angle.

[0050] Furthermore, the invention relates to a laser processing device for laser processing a defined cutting portion in a workpiece using the method according to the invention, the laser processing device comprising a laser system having a scanning unit for moving a laser beam in at least two coordinate directions and configured to generate a laser beam along a scanning axis and to direct the laser beam onto the workpiece substantially perpendicularly to the surface area and to direct the laser beam onto the workpiece along a second cutting direction, a support for supporting and holding the workpiece and movable about at least one rotation axis and / or along at least one translation axis by a drive unit of the laser processing device, and at least one controller configured to scan the laser beam along a first cutting path and a second cutting path and to control the drive unit to move the workpiece to process the defined cutting portion and to determine n layers to be processed continuously by scanning the laser beam along the first cutting path and m segments to be processed by scanning the laser beam along the second cutting path. The controller may comprise a suitable processing unit, a device for controlling system hardware and processes, software and / or a memory for operating the laser processing device to perform the laser processing method.

[0051] The laser processing device may include a controller for controlling the movement of a mechanical axis associated with the workpiece and an optical axis associated with the scanning unit. Optionally, the laser processing device may include: a controller configured to move the workpiece around the mechanical axis; and another controller provided to move the optical axis of the scanning unit so that the laser beam is directed toward the workpiece and scans the entire surface of the workpiece. In addition, the scanning unit of the laser processing device may be configured to move along and / or around the mechanical axis while the workpiece remains positioned during processing. Optionally, the scanning unit may remain positioned while the workpiece moves along and / or around the mechanical axis. Even more, according to the method of the present invention, a mechanical axis of the laser processing device may be provided to move the workpiece and a scanning unit for laser processing the workpiece. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] For a more complete understanding of the present invention and its advantages, exemplary embodiments of the present invention are explained in more detail below with reference to the accompanying drawings, wherein like reference numerals represent like components, and wherein:

[0053] Figure 1 is a schematic diagram of an embodiment of a laser processing device for implementing the laser processing method according to the present invention;

[0054] Figure 2 is a schematic diagram of a first processing stage for producing a first intermediate geometry of a workpiece, showing the relative position between a laser beam and the workpiece;

[0055] Figure 3a is a schematic diagram showing a workpiece subdivided into layers in a first intermediate state;

[0056] Figure 3b is a schematic diagram of the machining volume removed from the workpiece in the first machining stage;

[0057] Figure 4a is a schematic diagram of a workpiece processed in a second processing stage, showing the relative position between the laser beam and the workpiece;

[0058] Figure 4b is a schematic diagram of a workpiece having a second intermediate geometry;

[0059] Figure 5 is a schematic top view of a second processing volume, showing m segments into which the second processing volume is divided;

[0060] Figure 6 is a schematic diagram of the workpiece in another intermediate state;

[0061] Figure 7a is a schematic top view showing a first cutting path of a first type;

[0062] Figure 7b is a schematic top view showing a first cutting path of a second type;

[0063] Figure 7c is a schematic top view showing a first cutting path of a third type;

[0064] Figure 8 FIG. 1 is a schematic diagram of an embodiment of a laser processing method according to the present invention. DETAILED DESCRIPTION

[0065] Figure 1 A laser processing device 1 is shown, which can be used to implement the method according to the invention and is described in detail in FIG. 7 . The laser processing device 1 has a laser 2, which can be of any suitable type, depending on the application. The laser 2 emits a laser beam 20 processed by an optical system 3, which can include optical components such as lenses, filters, beam expanders and / or even complex components with temporal and spatial beam sharpening optics, depending on the determined laser parameters. The laser beam 20 is then directed by a scanning unit 4 through a focusing optical device 5 onto a workpiece 10. The workpiece 10 is supported and held on a support 11 or chuck attached to a moving stage 12. In this embodiment, the moving stage 12 is controlled by a controller 6 and can be moved along a mechanical axis, such as a translation axis and / or a rotation axis.

[0066] According to one embodiment, the motion table 12 is configured to move the workpiece. The motion table 12 associated with the support 11 or the chuck can be provided with a rotation axis known as the A axis and / or the B axis, and / or can include a linear axis to move the workpiece to a predetermined position and / or to move the workpiece during laser processing. Many known designs can be used for the motion table 12 to include translation and / or rotational motion in the laser processing device 1.

[0067] Apart from Figure 1 In addition to the arrangement described in , the scanning unit 4 and / or the focusing optical device 5 can be configured as a movable unit attached to the second motion stage 13, so that it can be moved along the translation axis (e.g., the X-axis and the Y-axis) and optionally the Z-axis and / or the rotation axis. Therefore, the scanning unit 4 and / or the focusing optical device 5 and the support 11 can all be moved in the translation direction and / or around the rotation axis.

[0068] Alternatively, the support 11 is mounted on a fixed base and the scanning unit 4 and / or the focusing optics 5 can be moved by a corresponding motion stage 13 (not shown) controlled by the controller 6 .

[0069] according to Figure 1 , a controller 6 and a central processing unit (CPU) 8 are provided to control the movement of the workpiece through the motion stage 12, and to control the scanning unit 4 and the laser 2 and / or the optical system 3. The controller 6 and any other controllers 7 (not shown) may generally include a CPU 8, a memory, and supporting circuits. The CPU may be any type of computer processor used in a laser processing device to control the device hardware and processes. The memory may be connected to the CPU 8 and may be one or more readily available memories, such as a random access memory (RAM), a read-only memory (ROM), and other forms of digital memory (local or remote). Software instructions and data may be encoded and stored in the memory for instructing the CPU 8. Command signals are typically output based on the programmed instructions stored in the memory, and the functions of each programmed instruction are executed by the logic of the CPU 8. Various elements of the laser processing device may include dedicated controllers that send data to and from the main controller along a communication path.

[0070] Preferably, the controller 6 is adapted to control the motion stage 12 and / or the further motion stage 13 so as to provide a relative motion between the scanning unit 4 and the workpiece 10, and to control the motion of the axis of the scanning unit 4 so as to control the motion of the laser beam. According to another embodiment, the control of the relative positioning of the scanning unit 4 and the workpiece 10 and the control of the motion of the axis of the scanning unit 4 are separate: a further controller 7 may be provided to control the axis of the scanning unit 4 so as to control the motion of the laser beam, while the controller 6 controls only the motion stage 12 and / or the motion stage 13.

[0071] Figure 2 is a schematic diagram of a workpiece 10. The workpiece 10 has a depth d extending from a surface 21, for example, 5 mm. Figure 2 An exemplary workpiece 10 is shown, and material is removed to form a blind hole or a first cut portion 25 by directing and scanning a laser beam 20 along a first cutting path 29 (not shown). The laser beam 20 is directed to a scan surface 21 by a scanning unit 4 and a focusing lens 5, wherein a scan axis 34 is orthogonal or nearly orthogonal to the surface 21. The machining volume is removed by scanning the laser beam 20 in a spiral shape, or a series of parallel lines, or along another scanning path, thereby removing the material volume in layers. The scanning path can have an axial offset and a lateral offset between each scan.

[0072] like Figure 2 As shown, the first cut portion 25 or in this case the blind hole has a first tapered feature 23 with a taper angle α, which corresponds to the angle between the inner wall of the first cut portion 25 and a perpendicular to the surface 21. The taper angle α resulting from such machining using the scanning unit 4 is typically between 5° and 20°.

[0073] according to Figure 3a In the example shown, the depth d of the workpiece 10 is subdivided into n layers, where the number of n layers depends on the depth d and the laser processing constraints. Figure 3a In the example, n is 4. Each layer n 1 、n 2 、n 3 、n 4 It may have an individual thickness t ranging from 0.1 mm to 2 mm, typically about 1 mm. 1 The processing volume is 22 ( Figure 3b After the first cutting portion 25 is cut, the first cutting portion 25 has a first tapered feature 23, including a straight, concave or convex structured sidewall 24. The first tapered feature 23 may vary depending on material properties, process parameters and / or processing volume 22. Figure 3a The second processing volume 26 represented by the shaded variation in FIG. 1 includes the first side wall 24 and the second side wall 27, and is Figure 4a The subsequent processing shown is processed.

[0074] In the case of machining a through hole in the workpiece 10, in order to have a faster machining process, the laser beam 20 does not have to scan the entire surface 21 of the machining volume to be removed. A central portion can remain, which will be removed by shedding when the through hole is completed.

[0075] Figure 3b 1 is a diagram showing a first layer n removed from an exemplary workpiece 10 during a first machining stage. 1Schematic diagram of the removed material volume 22.

[0076] Figure 4a 1 is a schematic diagram of a workpiece 10, showing a machining step for removing a defined second machining volume 26 (not shown). The second machining volume 26 may be defined by a first sidewall 24 having a first tapered feature 23, or may include the first sidewall 24 and a predetermined second sidewall 27 having a predetermined feature 28, such as Figure 4b Preferably, the predetermined feature 28 has a zero taper angle such that the second side wall 27 (not shown) extends perpendicularly from the surface 21 of the workpiece 10 .

[0077] The second processing volume 26 can be removed by relatively positioning the laser beam 20 and / or the workpiece 10 at a predetermined second relative position. The scanning axis 34 can be oriented at a predetermined tilt angle β to process the second processing volume 26, and the second processing volume 26 can be irradiated while the laser beam 20 is scanned across the second processing volume 26. 1 After that, a blind hole with zero taper is generated, such as Figure 4b shown.

[0078] Figure 5 A second processing volume 26 to be removed is shown in a schematic top view. The illustrated second processing volume 26 is in this case limited by or includes a first side wall 24 with a first tapered feature 23 and a second side wall 27 with a predetermined feature 28, and extends beyond the processing volume 22 or beyond the thickness t of the layer to be processed. The second processing volume 26 is subdivided into m segments. Depending on the shape and / or size of the second processing volume 26, the number m can vary between 1 and 6, preferably about 4. Each of the m segments is laser processed by positioning one of the m segments and the scanning axis 34 relative to each other in a predetermined relative position so that the segment is irradiated by scanning the laser beam 20 along a second cutting path 36. In this embodiment, the second cutting path 36 includes parallel straight lines, but may also have other structures. Each of the m segments can be processed until the second feature 28 of the segment is obtained before the workpiece 10 and / or the scanning unit 4 are rearranged to process another segment of the m segments. Alternatively, the laser beam 20 is scanned across all m segments to layer-wise remove the second processing volume 26. The second cutting path 36 may vary in scanning direction and scanning configuration.

[0079] Figure 6 is a schematic diagram of a workpiece 10 having another intermediate geometry, showing the first layer n being machined. 1 After that and in performing the processing of the second layer n 2 After the first step, the workpiece 10, wherein the second layer n 2The processing volume 22 is removed. Therefore, the second layer n 2 The second layer n includes a first sidewall 24 having a first tapered feature 23. 2 The first tapered feature 23 may be different from the first layer n 1 The first tapered feature 23 is formed to form another tapered angle α.

[0080] Figure 7a , Figure 7b and Figure 7c Each shows a top view of a workpiece 10 , in particular a first cutting path 29 , along which the laser beam 20 scans across the surface 21 to be machined. Figure 7a The cutout portion 25 shown in FIG. 1 is a hole having a circular surface area 30 defined by a perimeter 31. Figure 7a The laser beam 20 is scanned in a spiral path across the surface portion to be processed, with a specific distance between adjacent loops. The first cutting path 29 can vary from scan to scan in terms of scanning speed, laser power and / or other parameters (such as the position of the start and / or end point and the scanning direction). Figure 7a As shown, the central portion remains unprocessed after processing.

[0081] Figure 7b Another structure of the first cutting path 29 is shown, which is in the shape of a spiral path, and the starting point and / or end point of each scan is located at the center 32 or the perimeter 31. Figure 7b As shown, no central portion remains unprocessed after processing.

[0082] Figure 7c Another first cutting path 29 is shown which is 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 well machined.

[0083] Figure 8An example of a laser processing method 100 is shown for forming a defined cut portion in a workpiece 10 according to at least one embodiment. The example method includes relative positioning 102 of the workpiece 10 held in a support 11 and a laser beam 20 propagated through a scanning unit 4 and a focusing optical device 5. The laser processing method 100 also includes, in an operation 104, defining a processing volume of the workpiece, the processing volume including a surface area 30 defined by a perimeter 31 and a depth d, and according to one embodiment, subdividing the processing volume into n layers. Each layer is defined by a separate surface area 30 and a predetermined thickness t and defines a processing volume 22. In one embodiment, depending on the depth d of the processing volume, n can be 1, so that the processing volume 22 corresponds to the processing volume of the layer. In addition, one or more characteristics defining the cut portion 25 can be determined, such as a top perimeter 31 corresponding to the cut portion opening, a bottom perimeter, a first tapered feature 23, etc. The example method 100 also includes an operation 106 of determining a layer of the n layers to be processed (hereinafter referred to as layer n) by controlling the movement of the workpiece 10 by means of the motion stage 12 and / or the scanning unit 4 and the focusing optical device 5. 1 ) and the scanning axis 34. In this relative position, the scanning axis 34 is oriented substantially perpendicular to the layer n. 1 In operation 108, a laser beam 20 emitted from the laser 2 is focused on the surface 21 according to the laser process parameters. The operation 108 includes the laser beam 20 being focused on the surface 21 by the layer n. 1 The laser beam 20 is scanned along the first cutting path 29 within the surface area 30 defined by the perimeter 31. This operation can remove the processing volume 22 of the layer by scanning the laser beam 20 across the surface area 30 multiple times, wherein each scan removes a material layer in the range of 0.1 μm to 25 μm.

[0084] The method 100 further comprises an operation 110 for defining a second machining volume 26 between the first side wall 24 formed in operation 108 and a predetermined second side wall 27, the second side wall 27 corresponding at least partially to the defined side wall of the cut portion to be machined. This operation 110 may comprise virtually subdividing the second machining volume 26 into m segments that can be subsequently machined.

[0085] Operation 112 includes determining a second relative position between the second processing volume 26 and the scan axis 34 and repositioning the workpiece 10 and / or the scan axis 34 at the second relative position. In operation 112, the laser beam 20 is directed at the second processing volume at a predetermined tilt angle β, and laser process parameters may be adjusted based on one or more characteristics of the method 100. In some embodiments, the laser process parameters may include laser power, focused beam diameter, focus height, spot size, an offset of the laser beam 20 relative to a previous scan, and / or a combination thereof.

[0086] The method 100 includes an operation 114 in which at least a portion of the second processing volume 26 is removed with the adjusted laser process parameters. According to the method 100, each of the m segments of the second processing volume 26 is processed, including rearranging the workpiece 10 and the scanning axis 34, so that optimal laser processing conditions are achieved for processing each segment. 1 After the second machining volume 26 is removed, the method 100 includes repeating operations 106 to 114 until the cut portion of the workpiece 10 has reached a defined shape. In one embodiment, the method 100 also includes another operation 116 to complete the shaped sidewall of the cut portion.

[0087] The invention is not limited to the embodiments described but may be varied in construction and details.

Claims

1. A method (100) for laser machining a defined cut portion in a workpiece (10), comprising: - generating a laser beam (20) which propagates along a scanning axis (34) through a scanning unit (4), - providing a workpiece (10) which is supported and held in a support (11) and can be positioned relative to the scanning axis (34), Wherein, the method (100) further comprises: a) defining a machining volume (22) of a workpiece (10) having a surface area (30) and a depth (d), b) determining a first relative position between the machining volume (22) and the scanning axis (34), in which the scanning axis (34) is oriented substantially perpendicular to a surface (21) of the machining volume (22), and positioning the workpiece (10) and / or the scanning axis (34) in the first relative position, c) directing the laser beam (20) onto the processing volume (22), causing a relative movement between the workpiece (10) and the laser beam (20) within the surface area (30), and causing the laser beam (20) to scan along a first cutting path (29), d) removing at least a portion of the machining volume (22) to form a first cutting portion (25) having a first sidewall (24) having a first tapered feature (23), e) defining a second processing volume (26) comprising the first side wall (24) and being defined in part by a second side wall (27) having a predetermined feature (28), f) determining a second relative position between the second machining volume (26) and the scanning axis (34) and positioning the workpiece (10) and / or the scanning axis (34) in the second relative position, and g) the scanning axis (34) is tilted relative to the workpiece (10) at a predetermined inclination angle (β) The laser beam (20) is oriented and directed onto the second processing volume (26), the laser beam (20) is scanned along a second cutting path (36), and at least a portion of the second processing volume (26) is removed to form the second sidewall (27).

2. The method (100) according to claim 1, wherein in step e), the second processing volume (26) is divided into m segments, wherein m ≥ 1, preferably 1 to 4, wherein In step f), the relative position between one of the m segments and the scanning axis (34) is determined, and the segment and / or the scanning axis (34) is positioned in the relative position, and in step g), the scanning axis (34) is oriented on the segment at the predetermined inclination angle (β), the segment is irradiated by scanning the laser beam (20) along the second cutting path (36), and material is removed from the segment to form a second side wall (27) of the segment, and steps e) to g) are repeated until material of the second processing volume (26) is removed.

3. The method (100) according to claim 1 or 2, wherein: The machining volume (22) of the workpiece (10) defined in step a) is subdivided into n layers, each layer being determined by a surface area (30) defined by a thickness (t) and a perimeter (31), wherein n>1, wherein each of the n layers defines a separate machining volume (22) of the layer machined according to steps b) to d), and the method comprises repeating steps b) to g) until the cut portion of the workpiece (10) reaches a defined shape.

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

5. The method (100) according to any one of the preceding claims, wherein: The defined cut portion in the workpiece (10) is a blind hole, a through hole, a through hole with a countersunk hole at one or both ends of the through hole, or a cut portion with a constant or varying cross section.

6. The method (100) according to any one of the preceding claims, wherein: The predetermined characteristics (28) include positive, zero and negative taper characteristics.

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

8. The method (100) according to any one of claims 3 to 7, wherein: Material of each of the n layers is removed by repeated scans of the laser beam (20), the laser beam (20) having an axial offset of 0.1 μm to 25 μm in the direction of the scan axis (34) between the scans.

9. The method (100) according to any one of the preceding claims, wherein: The first cutting path (29) is in the form of a spiral running from the perimeter (31) of the surface area (30) towards the center (32) of the surface area (30) or in the opposite direction, or the first cutting path (29) is a series of deviating curves of at least a portion of the perimeter (31).

10. The method (100) according to any one of claims 1 to 8, wherein: The first cutting path (29) is a pattern comprising a plurality of lines and / or intersecting lines with lateral offsets therebetween.

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

12. The method (100) according to any one of claims 1, 3 to 11, wherein: The second processing volume (26) is processed layer by layer by multiple scans of the laser beam (20) with an axial offset until the predetermined feature (28) is achieved.

13. The method (100) according to any one of claims 2 to 11, wherein: Each of the m segments of the second processing volume (26) is processed until a predetermined characteristic (28) of the segment is achieved, and then the next segment of the m segments is processed.

14. A method (100) according to any one of the preceding claims, wherein the processing of the defined cutting portion starts from the top side of the defined cutting portion and then proceeds from the bottom side of the defined cutting portion, and a plurality of the cutting portions are combined together to form a single through-cutting portion.

15. A laser processing apparatus (1) for laser processing a defined cutting portion in a workpiece (10) using a method according to any one of claims 1 to 14, comprising: - a laser system having a scanning unit (4) comprising at least one optical axis and at least one mechanical axis, configured to generate a laser beam (20) along a scanning axis (34), to direct the laser beam (20) onto the workpiece (10) in a first cutting direction substantially perpendicular to a surface (21) of the workpiece, and to direct the laser beam (20) onto the workpiece (10) in a second cutting direction, a support (11) for supporting and holding the workpiece (10), the support being movable about at least one rotation axis and / or along at least one translation axis by a drive unit of the laser processing device (1), The workpiece (10) is moved along the second cutting path (36) and / or at least one mechanical axis of the laser processing device (1) is controlled to process the defined cutting portion.

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