Powder nozzle for a laser processing machine

Abstract

Powder nozzle (15) for a machine (1) for machining workpieces and / or for producing shaped bodies by locally solidifying material powder into coherent regions by means of a laser beam, comprising: a base body with an axial through-opening for the laser beam; Fastening means (16) for releasably fastening the powder nozzle (15) to a laser processing head (2) of the machine (1); Means for cooling the powder nozzle (15), characterized in that the fastening means (16) comprise at least two clamping bolts.

Description

[0001] The present invention relates to a powder nozzle for a machine for machining workpieces and / or for producing molded bodies by locally solidifying material powder into coherent regions using a laser beam. The invention particularly relates to a powder nozzle for a machine for manufacturing molded bodies using the principle of selective laser melting, selective laser sintering, or laser cladding. The term "laser machine tool" or simply "machine" is used below to summarize the various types of machines for machining / finishing / manufacturing a workpiece or a molded body using a laser beam. background

[0002] Using selective laser melting, laser sintering, or laser cladding, molded bodies such as machine parts, tools, prostheses, jewelry, etc. can be manufactured or processed according to the geometric description data of the corresponding molded bodies, for example by layering them from a metallic or ceramic material powder or a plastic powder. During the manufacturing process, the material powder is heated by a focused laser beam in a predetermined area corresponding to a selected cross-sectional area of ​​the model of the molded body, so that the material powder is remelted into coherently solidified sections in the irradiated areas. A protective gas can prevent oxidation during the build-up process. After cooling, a material layer is created that can be machined.

[0003] US Patent No. 5,961,862 A discloses a machining head for a laser machine tool with a powder nozzle having an axial through-opening for a laser beam. The powder nozzle can be attached to an optics module via a flange using fastening means. The powder nozzle also has cooling channels.

[0004] Regarding the state of the art in the field of selective laser melting, reference is made, for example, to DE 10 2015 222 689 A1. Furthermore, a laser machine tool of the type mentioned above is known, for example, from EP 2 052 845 A2. A machine tool for build-up welding is described, for example, in published patent application DE 10 2013 224 649 A1. German published patent application DE 196 30 147 A1 describes a connection head for machining a workpiece using a laser beam, which head has an automatic focusing lens changing mechanism designed as a revolver.

[0005] The article "Laser unit enables deposition welding on machining centers" by Nowotny et al. in "MM Das Industriemagazin," issue 17 / 2009, page 42 ff., describes a laser processing optics system that is inserted into the milling spindle of a CNC machine via a steep taper. Weld material (material powder) is fed into the laser focal point through a powder nozzle. The workpiece can be milled in the same machine.

[0006] Patent application US 2017 / 0136578 A1 describes a machine for the layer-by-layer construction of a three-dimensional molded body by melting a material powder with a generic powder nozzle. The material powder is guided to a working point by means of the powder nozzle attached to a laser processing head, where it is melted by a laser beam guided through the powder nozzle. The machine has a powder nozzle exchange unit that can replace the powder nozzle attached to the laser processing head.

[0007] European patent application EP 2 062 679 A1 discloses a processing head for a laser processing machine. The processing head has a stationary part in the form of a laterally open housing that encloses a space for an interchangeable module that can be separated as a whole from the stationary part of the processing head without having to disassemble the stationary part into individual parts. The interchangeable module comprises a focusing optics system that can be moved coaxially to the laser beam and a measuring device for determining the position of the focusing optics system.

[0008] A laser machine tool is typically operated with a laser that provides a laser beam with an output power of several hundred to several thousand watts, usually in continuous wave (CW) mode. The energy transfer from the laser beam to the material powder can be particularly crucial for the machining process. This is influenced on the one hand by the absorption capacity of the material powder and on the other hand by the intensity of the laser beam. In addition to the absolute laser power, the beam diameter therefore determines the melting process. The beam diameter of the laser beam is usually determined by the focal length of a focusing optics and by the beam diameter of the collimated laser beam upstream of the focusing optics. The beam diameter of the collimated laser beam can be determined in particular by the focal length of a collimation optics.Thus, the beam diameter of the focused laser beam, or the waist of a Gaussian laser beam, can be adjusted by appropriate choice of the collimation optics without changing the focal length of the focusing optics.

[0009] According to the prior art, essentially two types of machines are known for processing workpieces and / or for producing shaped bodies by locally solidifying material powder into coherent regions using a laser beam, in particular by selective laser melting or selective laser sintering. The machine types differ, among other things, in the manner in which the material powder is provided. In a first machine type, a powder bed is built up layer by layer. In a second machine type, the material powder is provided at the processing location using a powder nozzle. The present invention relates in particular to machines in which the laser beam is provided by means of a laser processing head.The mechanical setup for moving the laser processing head and / or the workpiece can be similar to that of a conventional five-axis machining center, for example, but with the laser processing head instead of a mechanical tool. For several years now, machine tools have also been available on the market that allow both laser processing and machining, for example, with a milling tool. In such hybrid machining centers, the laser processing head can be attached to the tool spindle mount.

[0010] The laser processing head can include a variety of optical components for manipulating the laser beam, such as for collimating, focusing, deflecting, monitoring, switching, and / or modulating the laser beam's power. It has proven advantageous to combine as many components as possible into a replaceable pre-assembled optical module that can be removably attached to the machine using suitable means. This simplifies and accelerates the maintenance of a laser machine tool, allowing the machine to be used more efficiently by reducing machine idle time. The powder nozzle is typically attached to the laser processing head. Summary

[0011] The present invention is based on the object of providing a powder nozzle that can be replaced quickly and easily. Furthermore, the powder nozzle should be able to generate the most homogeneous powder flow possible for laser cladding. Furthermore, a powder nozzle should be provided that can also be used at very high laser beam powers.

[0012] The problem is solved by a powder nozzle having the features of claim 1.

[0013] When processing a workpiece with a laser beam, scattered or reflected laser light can hit the powder nozzle. This can cause the powder nozzle to heat up. Especially at high laser beam powers of several thousand watts, there is a risk that the powder nozzle can become very hot. To dissipate the heat transferred from the laser beam to the powder nozzle, the powder nozzle can be cooled. For this purpose, the powder nozzle has a circuit for a fluid coolant such as water.

[0014] In particular, the powder nozzle can be changed automatically during a machining process, so that, for example, if the diameter of the laser beam at the working point changes during the machining process, a suitable powder nozzle can be automatically attached to the laser machining head.

[0015] The laser processing head can have a detachably attachable optics module in or on which the optical components for collimating and focusing the laser beam are arranged. The powder nozzle according to the invention can in particular be attached directly to such an optics module. A collimating lens arranged in the optics module serves to collimate a laser beam that is divergently coupled into the optics module. For example, the laser beam can be coupled into the optics module by means of an optical fiber. The optics module can therefore have means for connecting an optical fiber, in particular a fiber coupler. Since an optical fiber can transport laser light over many meters, it is possible to place the laser in a protected location away from the process chamber. The collimated laser beam can be focused onto a focal point by a focusing lens attached to the optics module.The laser beam thus leaves the optics module as a focused beam.

[0016] Optical components of laser machine tools can, on the one hand, be subject to increased wear due to the relatively high laser power. On the other hand, particularly in hybrid machines that can perform both laser processing and machining, contamination of optical components, for example from coolant, dust, chips, and other particles, can occur. Furthermore, the material powder can contribute to contamination of optical components. Dirt particles deposited on an optical component can, particularly at high laser powers, lead to significant heat exposure to the optical component and thus to its damage. It is therefore desirable for optical components to be able to be replaced quickly and easily in the event of damage or contamination. This is achieved, on the one hand, by the fact that the entire optical module can be detachably attached to an adjustment axis as a pre-assembled unit, making it easy to replace.On the other hand, interchangeable optical components enable quick replacement without disassembling the entire optical module. For example, a collimation optics changer located in the optical module can enable quick, automatic replacement of the collimation optics without requiring replacement of the entire collimation changer or the optical module.

[0017] The optical components arranged in the optical module can each be detachably mounted in or on the housing of the optical module. This allows, on the one hand, automatic replacement of the optical components during machine operation. On the other hand, an optical module requiring maintenance can be restored to operational condition by replacing individual optical components. For example, the collimation changer can be arranged as a detachable module in the housing of the optical module and thus be replaced during maintenance of the optical module.

[0018] Advantageous training and further education, which can be used individually or in combination with each other, are the subject of the dependent claims.

[0019] The optics module preferably has means for attaching an automatically exchangeable focusing module. The focusing module can be connected to the optics module, for example, via at least two clamping bolts. The optics module can have corresponding receptacles for the clamping bolts. The receptacles can be designed, in particular, as electromagnetically, hydraulically, or pneumatically actuated or spring-loaded clamping mechanisms. The optics module can further have means for monitoring the temperature of the focusing optics or a protective glass of the focusing optics. By providing means for attaching an automatically exchangeable focusing module, the focusing optics can be automatically changed. These can then be exchanged fully automatically during the manufacturing or machining process, similar to a tool in a machining center.The automated switching of focusing optics and collimation optics allows the beam diameter of the laser beam at the focus to be adjusted within a wide range depending on requirements. The clamping bolts allow for quick and secure attachment of the focusing module to the optics module. Furthermore, the clamping bolts ensure that the focusing module can be attached to the optics module with high positioning accuracy.

[0020] A focusing module preferably comprises a substantially cylindrical carrier with a circular cross-section, which is made, for example, from a metal or a metal alloy. A focusing optic is arranged in the carrier. The focusing optic can preferably be detachably fastened in the carrier of the focusing module, so that the focusing optic can be replaced. The focal length of the focusing optic can be, for example, several hundred millimeters. The focusing optic can be a conventional converging lens or a combination of several lenses. The focusing module preferably has means for measuring the temperature of the focusing optic. It is further preferred that the focusing module has means for cooling the focusing optic.

[0021] The focusing module can have at least one protective glass to protect the focusing optics from contamination. The protective glass can also protect the focusing optics from mechanical influences. The protective glass is preferably detachably attached to the carrier of the focusing module. If it becomes contamination, the protective glass can be replaced. A protective glass is preferably arranged on both sides of the focusing optics in the axial direction in the carrier of the focusing module, so that the focusing optics are protected from contamination on both sides. The focusing module can also have means for measuring the temperature of the at least one protective glass. Thus, contamination of a protective glass can be detected, for example, by a temperature increase.

[0022] The optics module can further comprise means for attaching an automatically replaceable powder nozzle. The powder nozzle can, for example, comprise at least two clamping bolts. The optics module can have corresponding receptacles for attaching the clamping bolts. The receptacles can have a clamping mechanism, which can be designed, in particular, as a hydraulically or pneumatically actuated mechanism or as a spring-loaded mechanism. The clamping bolts allow for quick and secure attachment of the powder nozzle to the optics module. Furthermore, the clamping bolts ensure that the powder nozzle can be attached to the optics module with high positioning accuracy.

[0023] The powder nozzle can be constructed in one piece or in multiple parts. In a multi-part construction, the powder nozzle can comprise a powder nozzle flange on which the means for attaching the powder nozzle to the optics module, for example, at least two clamping bolts, are arranged. Interfaces for supplying protective gas, carrier gas, coolant, and / or material powder can also be arranged on the powder nozzle flange. The powder nozzle flange can preferably be arranged on a central section, which is designed as a support for a powder nozzle tip. The powder nozzle tip can be detachably attachable to the central section of the powder nozzle, thus allowing the powder nozzle tip to be replaced.

[0024] The powder nozzle has, in particular in the central section, at least one channel for material powder in order to transport the material powder to the focal point of the laser. The powder nozzle preferably has at least two or three or four or more material powder channels, which can also be branched in order to guide the material powder as evenly as possible to the laser focal point. The branching of the material powder channels or the coaxial guidance of the material powder takes place in particular in a tip of the powder nozzle. For this purpose, the powder nozzle tip can have an annular gap which ensures an even distribution of the material powder along an annular opening formed coaxially to the laser beam. The material powder is preferably guided from the material powder channels into the annular gap via a plurality of openings in order to guide the material powder into the annular gap with as even a distribution as possible.

[0025] The channels for the material powder can also be used to supply a protective or carrier gas. The protective gas serves to prevent the heated material powder from reacting with atmospheric oxygen. Furthermore, the protective gas can act as a carrier gas to transport the material powder. The material powder is then carried along by the flow of the carrier gas and through the material powder channels to the operating point at the focal point of the laser beam. Inert gases such as argon are particularly suitable as protective or carrier gases. The more material powder channels there are in the powder nozzle, the higher the flow rate of the material powder can be. In order to guide the material powder as evenly as possible to the focal point of the laser beam, a configuration with at least three or four material powder channels has proven advantageous.Optionally, the powder nozzle can have a variety of different material powder channels with different diameters for different powder grain sizes.

[0026] The optics module can comprise a plurality of interfaces for guiding material powder from material powder lines arranged on the optics module into the material powder channels of the powder nozzle. The interfaces can be configured, for example, as inlet openings on a flange for attaching the powder nozzle. The inlet openings can comprise sealing means for gas-tight sealing when attaching the powder nozzle to the optics module. The inlet openings can have means for aligning the inlet openings with the lines on the optics module.

[0027] The powder nozzle can have cooling channels for a fluid coolant to cool the powder nozzle. The optics module can have corresponding lines to supply the coolant to the powder nozzle. The optics module preferably has at least one coolant supply line and one coolant return line. The powder nozzle preferably has at least two couplings as detachable interfaces between the coolant supply line and the coolant return line of the optics module and the coolant channels of the powder nozzle. The couplings can be designed, for example, as quick-release couplings that can be connected to corresponding counterparts on the optics module.

[0028] By providing means for detachably attaching an automatically replaceable powder nozzle, the powder nozzle can be changed automatically. This can then be replaced fully automatically during the manufacturing or machining process, like a tool in a machining center.

[0029] The beam path through the optics module is preferably sealed gas-tight so that a barrier gas atmosphere can be maintained. Inert gases such as nitrogen or argon can be used as the barrier gas. It is particularly important that the barrier gas is free of particles that could contaminate the optics components. The entire housing of the optics module is preferably sealed gas-tight. To create the barrier gas atmosphere in the housing of the optics module, the optics module preferably has corresponding gas supply lines and / or means for connecting feeds. Instead of sealing the housing gas-tight, the housing can also be constructed in such a way that it is possible to build up a slight overpressure in the housing by supplying the barrier gas, thus preventing dust or material powder particles from entering the interior of the optics module. Short description of the characters

[0030] Further advantageous embodiments are described in more detail below with reference to an embodiment shown in the drawings, to which the invention is not limited, however.

[0031] They show schematically: Fig. 1: a machine tool with an optical module for manufacturing or machining a shaped body or workpiece using laser radiation. Fig. 2: a perspective sectional view of an embodiment of an optical module. Fig. 3: another perspective sectional view of the Fig. 2 shown embodiment of the optical module. Fig. 4: a perspective view of an embodiment of a machine tool for producing or machining a shaped body or workpiece by means of laser radiation. Fig.5: a perspective view of a tool changer for a machine tool for producing or machining a shaped body or workpiece by means of laser radiation. Fig. 6: (A) a partially cutaway perspective view and (B) a perspective view of a replaceable powder nozzle according to the invention. Fig. 7 an illustration of the principle of laser cladding. Fig. 8 (A) a perspective view of an interchangeable focusing module, (B) and (C) each show sectional views of the interchangeable focusing module with different focal lengths of the focusing optics. Detailed description of the invention using an embodiment

[0032] In the following description of a preferred embodiment of the present invention, like reference numerals designate like or comparable components.

[0033] Fig.1 shows a schematic representation of a machine 1 for machining a workpiece 30 and / or for producing a molded body 30 by spatially solidifying material powder into coherent regions using laser radiation. The machine 1 has a machine frame 21, to which a workpiece table 20 and an optics module 2 are attached indirectly via intermediate adjustment axes 18, 19. The adjustment axes 18, 19 can each have several translational (X, Y, Z) or rotational (φ, λ, θ) axes, which can be adjusted according to a machine control system.

[0034] The design can, for example, be such that the optics module 2 is attached to the machine frame 21 via one, two, or three translational adjustment axes 18 (X and / or Y and / or Z), while the workpiece table 20 is attached to the machine frame 21 via one, two, or three rotational adjustment axes 19. Such a laser machine tool 1 generally has a closed cabin (not shown) in which, for example, a protective gas atmosphere can be created and which shields the work area from contamination.

[0035] A workpiece 30 can be releasably mounted on the workpiece table 20 for machining. Alternatively, a molded body 30 can be built up layer by layer by site-selective solidification of material powder.

[0036] Machine 1 can, for example, be a five-axis laser machine tool for producing molded bodies by selectively solidifying powdered material into coherent regions using laser radiation. The optics module 2 is detachably attached to the adjustment axes 18 so that it can be quickly and easily replaced if necessary, for example, for maintenance. In such a five-axis laser machine tool, the optics module 2 is attached to the machine frame 21 via three translational adjustment axes 18 (X, Y, and Z), and the workpiece table 20 is arranged on the machine frame via two rotary axes.

[0037] An exemplary representation of a five-axis laser machine tool 1 for producing molded bodies by locally solidifying material powder into coherent areas by means of laser radiation is shown in Fig. 4. The illustrated embodiment essentially corresponds to the one shown in Fig.1 schematically depicts machine 1. The workpiece table 20 and the positioning axes 18 of the optics module 2 are arranged in a process chamber 22 that is essentially closed by a process chamber door 23. A display 24 arranged outside the process chamber 22 serves as an interface between the user and the machine control system. This display 24 can, for example, display measured values ​​and / or warning messages and / or control applications.

[0038] The machine tool 1 comprises a tool changer 25, which can be moved laterally into the process chamber 22 by means of adjusting axes 25a, 25b. A detailed view of the tool changer 25 is shown in Fig. 5. A plurality of focusing modules 13 and a plurality of powder nozzles 15 can be arranged on the tool changer 25. The Fig. The tool changer 25 shown in Figure 5 has three storage positions for powder nozzles 15 with different axial lengths.

[0039] The tool changer 25 further includes a storage area for at least two focusing modules 13 with focusing optics 14 of different focal lengths. Using two adjustment axes 25a, 25b, the focusing modules 13 or the powder nozzles 15 can be moved into the process chamber 22 so that they can be attached to the optics module 2. A method for changing the powder nozzles 15 or the focusing modules 13 is described further below.

[0040] The tool changer 25 can be moved by means of the adjustment axes 25a, 25b into a tool chamber that can be separated from the process chamber 22 by a movable partition wall. In the tool chamber, the focusing modules 13 and the powder nozzles 15 are protected from contamination, for example by material powder or welding fumes, when the workpiece is being machined in the process chamber 22.

[0041] In Fig.2 shows an embodiment of an optics module 2 that is detachably mounted on an adjustment axis 18. The adjustment axis 18 is, for example, a translation axis that can be moved in the Z direction and can be arranged on two further translation axes that can be moved in the X and Y directions, so that the optics module 2 can be moved in all three spatial directions. The optics module 2 is mounted on the adjustment axis 18 in such a way that the laser beam exits the optics module 2 vertically downwards (parallel to the direction of gravity or in the Z direction). By moving the adjustment axes 18, a focus of the focused laser beam can thus be moved in three dimensions in space in order to machine a workpiece or to build up a molded body layer by layer. Thus, a molded body can be built up layer by layer, as with a 3D printer, by fusing material powder.

[0042] The optics module 2 has a housing 8 in which a plurality of optical components are arranged. The housing 8 serves both as a mechanical platform for arranging the optical components and for protecting them from mechanical influences. A protective gas atmosphere can be created in the housing 8. Overpressure can prevent, for example, particles and dirt from penetrating the housing.

[0043] A fiber coupler 10 is arranged at an upper portion of the housing 8, through which a laser beam from an optical fiber can be coupled. Using an optical fiber, laser light from a laser beam source can be reliably guided to the optics module 2. The flexible optical fiber enables the optics module 2, and thus the laser beam, to be moved without having to move the laser beam source itself. Furthermore, an optical fiber can deliver a laser beam with a particularly uniform beam profile.

[0044] A high-power solid-state laser can be used as a laser beam source. These include, for example, doped YAG lasers. In particular, an ytterbium-doped YAG disk laser with a wavelength of 1030 nm can serve as a laser beam source. Alternatively, a fiber-guided diode laser with a wavelength of 1020 nm can be used as a beam source. Diode lasers can provide laser beams with a power output of several watts up to several thousand watts. This allows sufficient laser power to be provided for various machining and manufacturing processes.

[0045] Directly below the fiber coupler 10, a collimating optics changer 3 is arranged in the housing 8 of the optics module 2. A collimating optics 4 with a first focal length of, for example, 80 mm is arranged in the collimating optics changer 3 such that the laser beam emerging from the fiber is collimated to a diameter of approximately 36 mm. The collimating optics changer 3 can have further collimating optics 4 with focal lengths of, for example, 50 mm, 60 mm and / or 100 mm or more. This can provide collimated laser beams with diameters between approximately 10 mm and 100 mm. Suitable types of converging lenses, for example, can be used as collimating optics 4. A collimating optics 4 can consist of a single lens or comprise a plurality of lenses. The material, coating, and other lens properties can be selected depending on the laser wavelength and laser power used.

[0046] The collimated laser beam is directed by two deflecting mirrors 6, 7 arranged in the optics module 2 onto a focusing optics 14, which focuses the laser beam. The position or orientation of the deflecting mirrors 6, 7 is preferably adjustable in each case, so that the beam path of the laser beam can be adjusted automatically or manually. The correct adjustment of the laser beam can be monitored, for example, by the camera 9. In particular, the deflecting mirrors 6, 7 can be adjustable under the control of the machine control system. For this purpose, the deflecting mirrors 6, 7 can each be arranged on adjustable holders that can be controlled by means of control signals via the machine control system. The optics module 2 can have suitable interfaces for detachably connecting signal lines for the machine control system.

[0047] The focal length of the focusing optics 14 can, for example, be between 50 mm and 500 mm. The focusing optics 14 is preferably arranged in an automatically interchangeable focusing module 13, which can be attached to the optics module 2 via a fastening mechanism 11, 16. Thus, by changing the focusing module 13, the focal length of the focusing optics 14 can also be changed fully automatically.

[0048] Seven exemplary combinations of focal lengths of the collimation optics 4 and the focusing optics 14 are shown in Table 1 below. Table 1 also lists exemplary resulting values ​​of the diameters of the collimated laser beam and the focused laser beam for a fiber core diameter of 600 µm.

[0049] The smaller the beam diameter, the higher the laser intensity. In particular, a smaller beam diameter at the focal point of the laser beam allows for smaller structures to be produced. A smaller beam diameter at the focal point can be achieved with the same focal length of the focusing optics by using a larger beam diameter of the collimated laser beam in front of the focusing optics. A larger beam diameter of the collimated laser beam has the advantage that the optical elements in the optics module 2 are exposed to a lower laser intensity. This reduces the likelihood of damage to the optical elements, for example, because they are heated less. Table 1: Seven exemplary combinations of collimating optics focal length and focusing optics focal length: Size Unit Example 1 Example 2 Example 3 Example 4 Example 5 Example 8 Example 7 Performance W 4000 4000 4000 4000 4000 4000 4000 Focal length of the collimation optics mm 50 60 80 100 60 80 100 Diameter of the collimated beam mm 22 27 36 45 27 36 45 Focal length of the focusing optics mm 300 300 300 300 200 200 200 Diameter of the focused beam mm 3,6 3 2,3 1,8 2 1,5 1,2

[0050] An exemplary embodiment of the focusing module 13 is shown in Fig. 8A to C. Fig.Figure 8A shows a perspective view of a focusing module 13 with a substantially cylindrical support housing, which is preferably made of a metal with the smallest possible thermal expansion coefficient. According to the examples in Table 1, Fig. 8B a focusing module 13 with a focusing optics 14 having a focal length of 200 mm, and Fig. 8C shows a focusing module 13 with focusing optics 14 having a focal length of 300 mm. The focusing optics 14 of the different focal lengths are arranged in the various focusing modules 13 such that the resulting focal point of the laser is always at the same location.

[0051] Fasteners 16, for example, two clamping bolts, are arranged on an upper edge of the focusing module 13. The fastening means 16 also serve to ensure the highest possible positioning accuracy of less than 1 mm. This is particularly important for the precise guidance of the laser beam through the powder nozzle and to the correct operating point. Should deviations nevertheless occur, they can be detected by the camera 9 and corrected by the deflection mirrors 6, 7. The focusing module 13 has at least one protective glass 14a to protect the focusing optics 14 from contamination or damage. Preferably, as shown in the sectional drawings of the Fig. As shown in Figures 8B and C, a protective glass 14a is arranged on both sides of the focusing optics 14 in the focusing module 13 in order to protect the focusing optics 14 from contamination or mechanical influences on both sides.

[0052] The temperature of the at least one protective glass 14a can be monitored by a sensor 13a. Fig. 8B and C, only the temperature of the upper protective glass 14a, which is first hit by the laser beam, is shown monitored by a sensor 13a. A temperature-dependent resistor (NTC resistor) or a thermocouple can be used as a sensor, for example. The thermocouple can, in particular, be a wire made of a platinum alloy. Similarly, the temperature of other optical components in the optical module 2, in particular the collimation optics 4, the protective glasses of the collimation optics 4, the deflection mirrors 6, 7, and / or the focusing optics 14, can also be monitored.

[0053] An analog measurement signal generated by the temperature sensor 14a is forwarded via interfaces 13b on the focusing module 13 to signal lines in the optics module 2. From there, the measurement signal is output to a machine control system and converted into a temperature value so that the temperature of an optical component of the optics module 2 can be output in degrees Celsius. The measured temperature values ​​can be shown, for example, on the display 24. A temperature threshold value can be stored for each optical component in the machine control system. If the measured temperature of an optical component exceeds the stored threshold value, a warning signal can be generated. The warning signal can, for example, be output as a warning to a user. The warning can, for example, be visually displayed on the display 24 or by means of a warning light.Additionally or alternatively, the laser can be switched off to avoid damage to the optical component.

[0054] The interfaces 13b can also be used to signal the machine control system that a focusing module 13 has been successfully attached. Accordingly, the machine control system can detect that the focusing module 13 has been successfully released and deposited if a signal transmitted via the interfaces 13b is interrupted.

[0055] The replaceable powder nozzle 15 according to the invention can be attached under the focusing module 13, which can be attached to the optics module 2. An exemplary embodiment of the powder nozzle 15 is shown in Fig. 6A and Fig.6B. The powder nozzle 15, like the focusing module 13, has fastening means 16 that can be attached to the optics module 2 by means of corresponding receptacles 12. For example, a plurality of clamping bolts can be arranged on the powder nozzle 15 as fastening means 16. Such clamping bolts are also used in a similar manner for fastening tools in conventional machine tools. The receptacles 12 on the optics module 2 can clamp these clamping bolts to fasten the powder nozzle 15 via a hydraulic, pneumatic, electromagnetic, or spring-loaded mechanism, so that the powder nozzle 15 is detachably fastened to the optics module 2, whereby the same position of the powder nozzle 15 can always be achieved within a specified tolerance.

[0056] The Fig. 2 and Fig.The powder nozzle 15 shown in Figure 6 has a flange 15a at the upper end facing the optics module 2, on which the fastening means 16, for example two clamping bolts, are arranged. A substantially cylindrical central section of the powder nozzle 15 is arranged on the flange 15a. A substantially conical powder nozzle tip 15b is arranged at the lower end of the central section. The central section of the powder nozzle 15, together with the flange 15a, can advantageously serve as a carrier with feeds for coolant and material powder, to which the powder nozzle tip 15b can be detachably fastened. This enables the powder nozzle tip 15b to be changed.

[0057] Connections 15f, 15g or interfaces for supplying a coolant or a material powder are arranged on the flange 15a of the powder nozzle 15. The connections 15f for the coolant can be designed, for example, as quick-release couplings, which automatically connect to corresponding lines on the optics module 2 when the powder nozzle 15 is attached to the optics module 2. The inlets 15g for the material powder can be designed as simple openings that have a sealing ring. When the powder nozzle 15 is attached to the optics module 2, the inlets are pressed with the sealing rings against the corresponding outlets on the optics module in such a way that a gas-tight connection is created.

[0058] The inlets 15g for material powder are each in flow connection with channels 15d for the material powder, which run through the powder nozzle 15 to the tip 15b of the powder nozzle 15. An annular gap 15c is formed in the tip 15b of the powder nozzle 15, the gap width of which can taper in the flow direction in order to achieve a nozzle effect. The transition between the material powder channels 15d and the annular gap 15c is shaped in such a way that a circumferentially uniform distribution of the material powder is achieved. For example, a plurality of holes can be provided in a transition from the material powder channels 15d to the annular gap 15c. The holes can bring about a uniform distribution of the material powder P in the annular gap 15c. The flow of the material powder P can have the shape of a cone aligned coaxially with the focal point of the laser beam, as shown in the illustration of the Fig. 7 indicated.

[0059] The powder nozzle tip 15b can be detachably attached to the powder nozzle 15 so that it can be replaced, for example, if it becomes damaged or deformed due to heat. If the powder nozzle 15 is constructed from several parts, the powder nozzle tip 15b can also be made of a different, more heat-resistant and / or harder material than the rest of the powder nozzle 15. Differently dimensioned powder nozzle tips 15b can be used, for example, for different laser beam diameters. Furthermore, differently dimensioned annular gaps 15c with different opening widths can be formed in replaceable powder nozzle tips 15b. Accordingly, different powder nozzles 15 with differently dimensioned powder nozzle tips 15b can be kept in the machine 1 so that the entire powder nozzle 15 can be replaced if necessary.The diameter of the lower opening of the powder nozzle tip 15b facing the workpiece can be, for example, 1 mm, 2 mm, 3 mm, 4 mm, or 5 to 8 mm. The powder nozzle tips 15b are preferably replaced manually, while the entire powder nozzle 15 can be replaced fully automatically, as described below.

[0060] The powder nozzle 15 has at least two couplings 15f for coolant, which are preferably designed as quick-action couplings. One coupling 15f serves as a connection for the coolant flow from the optics module 2, the other coupling 15f serves as a connection for the coolant return to the optics module 2. The coolant connections 15f are in flow connection with coolant channels 15e in the powder nozzle 15, which are shown in the partially sectioned view of the Fig.6A. The coolant channels 15e can, for example, be arranged in a ring-shaped, spiral-shaped, or helical manner around the laser beam opening to ensure uniform cooling of the powder nozzle 15.

[0061] A substantially cylindrical recess for the focusing module 13 is formed inside the flange 15a. When the focusing module 13 and the powder nozzle 15 are attached to the optics module 2, the lower end of the focusing module 13 is located within the recess in the powder nozzle 15. The focusing module 13 and the powder nozzle 15 are arranged coaxially to each other and to the laser beam on the optics module 2.

[0062] The powder nozzle 15 has a very complex shape due to the large number of channels for coolant 15e and channels for material powder 15d, as well as its axial opening tapering in the axial direction towards the laser focal point. Such a complex shape can be produced, for example, by a laser deposition welding process in a machine 1 according to the invention. In order to be able to carry out the production process of the powder nozzle 15 by laser deposition welding in the shortest possible time and with the greatest possible savings in material, the essentially cylindrical central section of the powder nozzle 15 can, for example, be constructed with the thinnest possible wall thickness. To increase the mechanical strength of the powder nozzle 15, the wall can be reinforced by lamellae 15l. Similarly, the transition between the flange 15a and the central section of the powder nozzle 15 can be manufactured in a material-saving manner, for example by using a Fig.6B, which offers high mechanical strength with low material consumption.

[0063] The flange 15a and the central section of the powder nozzle 15 can be made of aluminum or steel, for example. The diameter of the flange 15a can be approximately 150 mm to 170 mm, preferably 160 mm. The entire length of the powder nozzle 15 can be approximately 125 mm to 145 mm, preferably 135 mm. When using focusing optics 14 with shorter focal lengths, correspondingly shorter powder nozzles with a length of less than 125 mm, for example 100 mm to 90 mm, can also be used. If focusing optics 14 with longer focal lengths are used, correspondingly longer powder nozzles with a length of more than 145 mm, for example 150 mm to 200 mm or even 300 mm, can also be used. The diameter of the central section of the powder nozzle can be approximately 60 mm to 70 mm, preferably 65 to 67 mm. Preferably, the powder nozzle 15 can also be designed to be even more compact in order to reduce the risk of collisions with the workpiece 30.

[0064] The powder nozzle 15 can be replaced, for example, as described below. The partition wall between the process chamber 22 and the tool chamber arranged laterally therefrom is pushed open. By means of the adjusting axis 25b, the lower part of the tool changer 25 with the powder nozzles 15 is moved into the process chamber 22. The adjusting axes 18 move the optics module 2 to the position where the tool changer 25 with the plurality of powder nozzles 15 is located. To deposit a powder nozzle 15 attached to the optics module 2, unlike in Fig. 4 and Fig. 5, a storage position of the tool changer 25 must be free. By opening the receptacles 12 on the optics module 2, the fastening means 16 of the powder nozzle 15 are released, so that the powder nozzle 15 is detached from the optics module 2 and can be stored in a free storage position of the tool changer 25.

[0065] The optics module 2 is then moved to another position on the tool changer 25, where another powder nozzle 15, which has a larger or smaller dimension in the axial direction, is located. The optics module 2 is then moved by means of the adjustment axes 18 so that the fastening means 16 of the additional powder nozzle 15 engage the receptacles 12 on the optics module 2. By closing the receptacles 12, the powder nozzle 15 can be attached to the optics module 2 and removed from the tool changer 25.

[0066] The automatic changing of the powder nozzle 15 can occur particularly when the focal length of the laser beam is changed by changing the focusing optics 14. Since the powder nozzle 15 is intended to direct the material powder to the location of the focal point of the laser beam, the axial length of the powder nozzle 15 must be selected according to the focal length of the laser beam. As listed in Table 1, the focal length of the focusing optics 14 can be, for example, 200 mm or 300 mm. Accordingly, corresponding powder nozzles 15 can be provided in the tool changer 25 of the machine 1, which direct the material powder to a focal point, for example, 200 mm or 300 mm away from the focusing optics 14.

[0067] A material powder can be provided at the working point of the machine 1, i.e., in the immediate vicinity of the focal point of the laser beam, via the powder nozzle 15. For this purpose, the powder nozzle 15 has one or more channels through which the material powder is guided. When the powder nozzle 15 is attached to the optics module 2, a connection is established between the channels for the material powder and corresponding lines in the optics module 2. The powder nozzle 15 and the optics module 2 each have suitable interfaces for connecting the channels and the lines. Furthermore, the powder nozzle 15 has one or more cooling channels in which a fluid coolant, in particular water, can circulate to cool the powder nozzle 15. The optics module 2 has corresponding lines for supplying and discharging the coolant, as well as interfaces for connecting the lines to the cooling channels of the powder nozzle 15.

[0068] Furthermore, the powder nozzle 15 can direct a shielding gas to the operating point of the machine 1, so that unwanted reactions can be largely suppressed when the material powder is melted at the focal point of the laser beam. The shielding gas serves, in particular, to displace oxygen from the air. Inert gases such as argon can be used as the shielding gas. The optics module 2 has corresponding lines for supplying the shielding gas. The shielding gas can also be supplied together with the material powder as a carrier gas. The shielding gas thus serves, on the one hand, to prevent a reaction with atmospheric oxygen and, on the other hand, to convey the material powder.

[0069] During automatic replacement of the powder nozzle 15, the cooling lines of the optics module 2 are automatically connected or disconnected with the cooling channels of the powder nozzle 15 via the corresponding interfaces. Accordingly, the lines for material powder in the optics module 2 are also automatically connected or disconnected with the material powder channels in the powder nozzle 15 via the corresponding interfaces. The corresponding interfaces for the lines and channels can be detachable and controlled, for example, via hydraulics or pneumatics.

[0070] An automatic change of the focusing module 13 can be performed in a similar manner to the automatic change of the powder nozzle 15. In this case, the upper part of the tool changer 25 with the focusing modules 13 is also moved into the process chamber 22 by means of the adjustment axis 25a. However, to change the focusing module 13, a powder nozzle 15 attached to the optics module 2 must first be released. This is done as described above by placing the powder nozzle 15 in a free storage position on the tool changer 25. The adjustment axes 18 then move the optics module 2 to a position where the tool changer 25 with the plurality of focusing modules 13 is located. The focusing module 13 attached to the optics module 2 can be released by opening the receptacles 11 on the optics module 2, so that the focusing module 13 can be detached from the optics module 2 and placed in a free storage position of the tool changer 25.Subsequently, another focusing module 13 can be attached to the optics module 2. For this purpose, the optics module 2 is moved such that the fastening means 16 of the focusing module 13 engage the receptacles 11 on the optics module 2. The receptacles 11 on the optics module 2 can now clamp the fastening means 16, for example, via a hydraulic, pneumatic, or spring-loaded mechanism, in order to attach the focusing module 13 to the optics module 2. The tool changer 25 can then be moved back into the detachable tool chamber, and machining of the workpiece can be started or continued.

[0071] The required travel paths of the adjustment axes 18, 25a, 25b can be stored in a memory of the machine control system, so that the changing of the focusing module 13 or the powder nozzle 15 can be carried out fully automatically. The changing of the focusing module 13 or the powder nozzle 15 can thus also be integrated into a machining process. Depending on the desired size of the structures to be manufactured on the workpiece 30 or the molded body 30, a suitable diameter of the laser beam at the focal point is selected. The smaller the diameter of the laser beam at the focal point, the smaller the structures that can be manufactured. The diameter of the laser beam is determined by the focal length of the focusing optics 14 and the collimation optics 3, as shown in Table 1. A suitable combination of collimation optics 4 and focusing optics 14 can thus be selected for each machining process.Depending on the selected collimation optics 4 and focusing optics 14, a suitable powder nozzle 15 is selected and attached to the optics module 2. On the one hand, the opening of the powder nozzle tip 15b must be large enough to allow the laser beam L to pass through unhindered. On the other hand, the opening of the powder nozzle tip 15b should be small enough to ensure a favorable and uniform flow of the material powder P through the annular gap 15c to the focal point of the laser beam L. Depending on the selected structure size, a suitable collimation optics 4 is adjusted on the collimation optics changer 3, and a suitable focusing module 13 and a corresponding powder nozzle 15 are attached to the optics module 2.

[0072] The first deflecting mirror 6 has means for cooling and monitoring the temperature of the mirror 6. The second deflecting mirror 7 is a dichroic mirror, which also has means for cooling and monitoring the temperature of the mirror 7. The dichroic mirror 7 is reflective for the wavelength of the laser beam, which lies, for example, in the infrared spectral range. However, the dichroic mirror can be transparent for visible light. A camera 9 for monitoring the production process can be arranged behind the dichroic mirror 7. The camera 9 is arranged with a view along the laser beam through the dichroic mirror and through the focusing optics 14 to the focal point of the laser beam. Thus, the camera 9 can be used to monitor the working point on the workpiece or the molded body to be manufactured.Furthermore, by monitoring the laser beam using the camera 9, it can be prevented that the laser beam hits the powder nozzle 15 directly and causes it to heat up or be damaged.

[0073] The working principle of laser cladding is explained using the Fig. 7 illustrated. Fig. 7 shows the tip 30 of a powder nozzle 15 in the vicinity of a workpiece W to be machined. A focused laser beam L runs coaxially to the powder nozzle 15 and is focused on a working point on the workpiece W. The material powder P is guided coaxially to the laser beam L through the powder nozzle 15 to the focal point of the laser beam L on the workpiece W. A protective or carrier gas G also flows through the powder nozzle 15 and transports the material powder P. The protective gas G, for example argon, also serves to prevent undesirable reactions of the heated material powder P or the workpiece W with atmospheric oxygen.

[0074] The features disclosed in the above description, the claims and the drawings may be important both individually and in any combination for the realization of the invention in its various embodiments. List of reference symbols 1 laser machine tool 2 optics module 3 collimation optics changers 4 Collimation optics 6 first deflection mirror 7 second deflecting mirror (dichroic mirror) 8 housings 9 Camera 10 fiber couplers 11 Interface for focusing optics 12 Interface for powder nozzle 13 Focusing module 13a Thermocouple 13b Thermocouple interface 14 Focusing optics 14a protective glass 15 Powder nozzle 15a Powder nozzle flange 15b Powder nozzle tip 15c Annular gap 15d material powder channel 15e cooling channel 15f coolant coupling 15g material powder inlet 15l slats 15w honeycomb structure 16 Fastening means comprising at least two clamping bolts 17 Laser beam path 18 tool adjustment axes 19 adjustment axes of the workpiece table 20 Workpiece table 21 machine frames 22 Process Chamber 23 Process room door 24 displays 25 tool changers 25a Adjustment axis of the focusing optics changer 25b Adjustment axis of the powder nozzle changer 30 workpiece L laser beam W workpiece P Workpiece powder G Shielding gas and / or carrier gas

Claims

[1] Powder nozzle (15) for a machine (1) for machining workpieces and / or for producing shaped bodies by locally solidifying material powder into coherent regions by means of a laser beam, comprising: a base body with an axial through-opening for the laser beam; Fastening means (16) for releasably fastening the powder nozzle (15) to a laser processing head (2) of the machine (1); means for cooling the powder nozzle (15), characterized by that the fastening means (16) comprise at least two clamping bolts. [2] Powder nozzle (15) according to claim 1, wherein a coolant circuit with at least one coolant supply (15f) for supplying the coolant, a coolant return (15f) for returning the coolant and a cooling channel (15e) which represents a flow connection from the coolant supply (15f) through the powder nozzle (15) to the coolant return (15f) is provided as means for cooling the powder nozzle (15). [3] Powder nozzle (15) according to claim 2, wherein the at least one coolant supply (15f) and the at least one coolant return (15f) each have at least one quick coupling for connecting to a coolant supply line and a coolant return line. [4] Powder nozzle (15) according to one of the preceding claims, wherein the powder nozzle (15) has a plurality of channels (15d) for the material powder for conveying the material powder to a focal point of the laser beam. [5] Powder nozzle (15) according to one of the preceding claims, wherein the powder nozzle (15) has a plurality of inlet openings (15g) for supplying the material powder. [6] Powder nozzle (15) according to one of the preceding claims, wherein the powder nozzle (15) has a tip (15b) with an annular gap (15c) which is designed to guide the material powder circumferentially uniformly from all sides to a working point of the laser. [7] Powder nozzle (15) according to claim 5, wherein the tip (15b) is detachably attached to the powder nozzle (15). [8] Powder nozzle (15) according to one of the preceding claims, wherein the powder nozzle (15) comprises means for measuring the temperature of the powder nozzle (15). [9] Machine (1) for machining workpieces and / or for producing shaped bodies by locally solidifying material powder into coherent areas by means of a laser beam, characterized bythat the machine has a powder nozzle (15) according to at least one of claims 1 to 8.

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