WO2019048612A1

WO2019048612A1 - Powder nozzle for a laser machine tool

Info

Publication number: WO2019048612A1
Application number: PCT/EP2018/074135
Authority: WO
Inventors: Udo STÜRMER; Andreas Abt
Original assignee: Sauer Gmbh
Priority date: 2017-09-07
Filing date: 2018-09-07
Publication date: 2019-03-14
Also published as: DE102017215841A1

Abstract

The invention relates to a powder nozzle (15) for a tool (1) for machining workpieces and/or producing moulded bodies by location-selective compaction of material powder to form continuous regions by means of a laser beam. The powder nozzle (15) comprises a substantially rotationally symmetric base body with an axial through-opening for the laser beam and securing means (16) for detachably securing the powder nozzle (15) to a laser machining head (2) of the tool (1). According to the invention, the powder nozzle (15) comprises means for cooling the powder nozzle (15).

Description

Powder nozzle for a laser processing machine

description

The present invention relates to a powder nozzle for a machine for processing workpieces and / or for producing shaped bodies by locally selective solidification of material powder to coherent areas by means of a laser beam. More particularly, the invention relates to a powder nozzle for a machine for producing shaped articles according to the principle of selective laser melting, selective laser sintering or laser deposition welding. In summary, for the various types of machines for processing / manufacturing / producing a workpiece or a shaped body with a laser beam, the term laser machine tool or simply a machine is used below.

background

With the method of selective laser melting, laser sintering or laser cladding, moldings such as machine parts, tools, prostheses, trinkets, etc., may be manufactured or machined according to geometric description data of the respective moldings, for example by layering from a metallic or ceramic material powder or a plastic powder. In the manufacturing process, the material powder is heated by a focused laser beam in a predetermined area, which corresponds to a selected cross-sectional area of the model of the molded body, so that the material powder is remelted in the irradiated areas to coherently solidified sections. A protective gas can prevent oxidation during the build-up process. After cooling, a layer of material is created, which can be processed mechanically.

The prior art relating to the field of selective laser melting, for example, reference is made to DE 10 2015 222 689 AI. Furthermore, a laser machine tool of the type mentioned in the introduction is known for example from EP 2 052 845 A2. A machine tool for build-up welding is described, for example, in the published patent application DE 10 2013 224 649 A1. In the German patent application DE 196 30 147 AI a connection head for machining a workpiece by means of a laser beam is described, which has an automatic focusing lens change mechanism, which is designed as a revolver. The article "Laser unit makes build-up welding on machining center possible" by Nowotny et al. in "MM Das Industriemagazin", 17/2009, page 42 ff., describes a laser processing optics, which is used via a steep taper in the milling spindle of a CNC machine. In the laser focal point weld metal (material powder) is fed through a powder nozzle. The workpiece can be milled in the same machine.

In the patent application US 2017/0136578 AI a machine for layered construction of a three-dimensional molded body by melting a material powder is described with a generic powder nozzle. The material pu Iver is conducted by means of the attached to a laser processing head powder nozzle to an operating point where it is melted by a laser beam, which is passed through the powder nozzle. The machine has a powder nozzle changing unit which can exchange the powder nozzle attached to the laser processing head.

European patent application EP 2 062 679 A1 discloses a machining head for a laser processing machine which has a stationary part in the form of a laterally open housing which encloses a space for a change module which can be separated as a whole from the stationary part of the machining head without the stationary part having to be dismantled into individual parts. The interchangeable module comprises a focusing optics, which is movable coaxially to the laser beam, and a measuring device for determining the position of the focusing optics.

A laser machine tool is usually operated with a laser that provides a laser beam with an output power of several hundred to several thousand watts, which are usually operated in continuous operation ("continuous wave", CW) 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 The beam diameter of the collimated laser beam can be determined in particular by the focal length of a collimating optical system n laser beam, or the waist of a Gaussian laser beam can be adjusted by a suitable choice of the collimating optics without changing the focal length of the focusing optics. According to the state of the art, essentially two types of machines are known for machining workpieces and / or for producing shaped bodies by locally solidifying material powder into contiguous areas by means of a laser beam, in particular by selective laser melting or selective laser sintering. The types of machines differ, among other things, in the way the material powder is provided. In a first type of machine, a powder bed is built up in layers. In a second type of machine, the material powder is provided by means of a powder nozzle at the point of machining. In particular, the present invention relates to machines in which the laser beam is provided by means of a laser processing head. The mechanical structure for moving the laser processing head and / or the workpiece, for example, as in a known five-axis machining center, wherein instead of a mechanical tool, the laser processing head is provided. Machine tools have also been available on the market for some years now, which permit both laser machining and machining, for example with a milling tool. In such hybrid machining centers, the laser processing head can be attached to the recording of the Werkzugspindel.

The laser processing head may include a variety of optical components for manipulating the laser beam, such as for collimating, focusing, redirecting, monitoring, switching and / or modulating the power of the laser beam. It has proved to be advantageous to combine as many components as possible in a preassembled as an exchangeable component optical module, which can be releasably secured by suitable means to the machine. As a result, the maintenance of a laser machine tool can be simplified and accelerated, so that the machine can be used more efficiently, since an idle time of the machine can be shortened. The powder nozzle is usually attached to the laser processing head.

Summary

The present invention has for its object to provide a powder nozzle, which can be exchanged quickly and easily. In addition, the powder nozzle should be able to produce as homogeneous a material powder flow for laser deposition welding. Furthermore, a powder nozzle is to be provided which can also be used at very high laser beam powers. The object is achieved by a powder nozzle with a substantially rotationally symmetrical base body with an axial passage opening for a laser beam and fastening means for releasably securing the powder nozzle to a laser processing head of a machine. According to the invention, the powder nozzle has means for cooling the powder nozzle. When machining a workpiece with a laser beam, scattered or reflected laser light can strike the powder nozzle. As a result, the powder nozzle can be heated. Especially at high laser beam powers of several thousand watts there is a risk that the powder nozzle can be very hot. In order to dissipate the heat transferred from the laser beam to the powder nozzle, the powder nozzle can be cooled according to the invention. For this purpose, the powder nozzle, for example, a circuit for a fluid coolant such as water.

In particular, the powder nozzle can be changed automatically during a machining process, so that, for example, when changing the diameter of the laser beam at the operating point during the machining process, a suitable powder nozzle can be automatically attached to the laser processing head.

The laser processing head can have a detachably mountable optical 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 optical module. A collimating lens arranged in the optical module serves for collimating a laser beam divergently coupled into the optical module. For example, the laser beam can be coupled into the optical module by means of an optical fiber. The optical module can accordingly 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 focus by a focusing lens attached to the optics module. The laser beam thus leaves the optics module as a focused beam.

On the one hand, optical components of laser machine tools can be subject to increased wear due to the relatively high laser powers. On the other hand, especially in a hybrid machine, which can perform both laser machining and machining manufacturing processes, contamination of optical components, for example by coolants, dust, chips and other particles, may occur. Furthermore, the material powder can contribute to the contamination of optical components. Dirt particles deposited on an optical component can, especially at high laser powers, lead to a high heat effect on the optical component and thus to its damage. Therefore, it is desirable if optical components can be replaced quickly and easily in the event of damage or contamination. On the one hand, this is achieved by the fact that the entire optical module can be detachably fastened as a preassembled subassembly to a positioning axis and is therefore easily replaceable. On the other hand, interchangeable optical components allow one quick change without removing the entire optical module. Thus, for example, a collimating optical changer arranged in the optical module can enable a fast automatic change of the collimating optics, without it being necessary to exchange the entire collimation changer or the optical module.

The optical components arranged in the optical module can each be releasably secured in or on the housing of the optical module. Thus, on the one hand take place during operation of the machine, an automatic change of the optical components. On the other hand, an optical module to be serviced can be brought back into an operable state by exchanging individual optical components. For example, the collimator changer can be detachably arranged as an exchangeable module in the housing of the optical module and thus exchanged during maintenance of the optical module.

Advantageous embodiments and developments, which can be used individually or in combination with each other, are the subject of the dependent claims.

The optical module preferably has means for fixing an automatically exchangeable focusing module. The focusing module can be connected, for example via at least two clamping bolts with the optical module. The optical module can have corresponding receptacles for the clamping bolts. The recordings can be designed in particular as electromagnetically, hydraulically or pneumatically actuated or tensioned by a spring clamping mechanisms. The optical module may further comprise 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, an automatic change of the focusing optics can take place. This can then be replaced fully automatically similar to a tool of a machining center during the manufacturing or machining process. By automatically changing the focusing optics and the collimation optics, the beam diameter of the laser beam in the focus can be set within a wide range, depending on the requirements. The clamping bolts allow a fast and secure fastening of the focusing module to the optical module. Furthermore, the clamping bolts ensure that the focusing module can be attached to the optical module with a high positional accuracy.

A focusing module preferably comprises a substantially cylindrical carrier with a circular cross section, which is made for example of a metal or a metal alloy. In the carrier a focusing optics is arranged. Preferably, the focusing optics can be detachably fastened in the carrier of the focusing module, so that replacement of the focusing optics is possible. The focal length of the focusing optics may be, for example, a few hundred millimeters. at The focusing optics may be a conventional converging lens or a combination of several lenses. The focusing module preferably has means for measuring the temperature of the focusing optics. It is further preferred that the focusing module has means for cooling the focusing optics.

The focusing module may have at least one protective glass for protecting the focusing optics from contamination. The protective glass can also protect against mechanical effects on the focusing optics. The protective glass is preferably detachably fastened in the carrier of the focusing module. If dirty, the protective glass can be replaced. Preferably, a protective glass is arranged on both sides of the focusing optics in the axial direction in the carrier of the focusing module, so that the focusing optics is protected from contamination on both sides. The focusing module may also include 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 rise in temperature.

The optical module may further comprise means for attaching an automatically replaceable powder nozzle. The powder nozzle may for example comprise at least two clamping bolts. The optical module can have corresponding receptacles for fastening the clamping bolts. The receptacles may have a clamping mechanism, which may be designed in particular as hydraulically or pneumatically actuated or tensioned by a spring mechanism. The clamping bolts allow quick and secure attachment of the powder nozzle to the optics module. Furthermore, the clamping bolts ensure that the powder nozzle with a high position accuracy can be attached to the optical module. The powder nozzle can be constructed in one piece or in several parts. In a multi-part construction, the powder nozzle can comprise a powder nozzle flange, on which the means for fastening the powder nozzle to the optical module, for example at least two clamping bolts, are arranged. On Pulverdüsenflansch also interfaces for supplying protective gas, carrier gas, coolant and / or powder material can be arranged. The powder nozzle flange may preferably be disposed at a central portion formed as a carrier for a powder nozzle tip. The powder nozzle tip may be releasably attachable to the central portion of the powder nozzle, so that replacement of the powder nozzle tip is possible.

The powder nozzle has in particular in the middle section at least one channel for material powder in order to convey the material powder to the focal point of the laser. Preferably, the powder nozzle 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 uniformly 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 causes a uniform distribution of the material powder along an annular opening formed coaxially with the laser beam. Preferably, the material powder is passed from the material powder channels via a plurality of openings in the annular gap in order to lead the material powder as evenly distributed as possible in the annular gap.

The channels for the material powder can also be used for supplying a protective or carrier gas. The protective gas serves to prevent a reaction of the heated material powder with atmospheric oxygen. Furthermore, the protective gas can cause the transport of the material powder as a carrier gas. The material powder is then carried along by the flow of the carrier gas and carried by the material powder channels to the operating point at the focal point of the laser beam. In particular, inert gases such as argon are suitable as protective or carrier gas. The more material powder channels are provided in the powder nozzle, the larger the flow rate of the material can be powder. In order to direct the material powder as uniformly as possible to the focal point of the laser beam, a configuration with at least three or four material powder channels has proven to be advantageous. Optionally, the powder nozzle may have a plurality of different material powder channels with different diameters for different powder grains.

The optical module may comprise a plurality of interfaces for directing material powder from lines for the material powder arranged on the optical module into the material powder channels of the powder nozzle. The interfaces may be formed, for example, as inlet openings on a flange for fastening the powder nozzle. The inlet openings may comprise sealing means for gas-tight sealing when attaching the powder nozzle to the optical module. The inlet ports may include means for aligning the inlet ports with the conduits on the optics module.

The powder nozzle may have cooling channels for a fluid coolant for cooling the powder nozzle. In order to supply the coolant to the powder nozzle, the optical module can have corresponding lines. The optical module preferably has at least one coolant feed and one coolant return. The powder nozzle preferably has at least two couplings as detachable interfaces between the coolant flow and coolant return of the optical module and the coolant channels of the powder nozzle. The couplings may for example be designed as quick couplings that can be connected to corresponding counterparts on the optical module. By providing means for releasably securing an automatically replaceable powder nozzle, an automatic change of the powder nozzle can take place. This can then be replaced fully automatically as a tool of a machining center during the manufacturing or machining process.

The beam path through the optical module is preferably sealed gas-tight, so that a sealing gas atmosphere can be maintained. In particular, inert gases such as nitrogen or argon can be used as the sealing gas. It is important, above all, that the sealing gas is free of particles that can pollute the optical components. Preferably, the entire housing of the optical module is sealed gas-tight. To build up the sealing gas atmosphere in the housing of the optical module, the optical module preferably has corresponding gas supply lines and / or means for connecting feeders. Instead of sealing the housing in a gas-tight manner, 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 so that it is possible to prevent particles of dust or material from getting inside the optics module.

Brief description of the figures

Further advantageous embodiments will be described in more detail below with reference to an embodiment shown in the drawings, to which the invention is not limited.

They show schematically:

Figure 1: a machine tool with an optical module for producing or processing a shaped body or workpiece by means of laser radiation.

FIG. 2 shows a perspective sectional view of an embodiment of a

Optical module.

FIG. 3 shows a further perspective sectional view of that shown in FIG

Embodiment of the optical module.

FIG. 4 shows a perspective view of an exemplary embodiment of a machine tool for producing or processing a shaped body or workpiece by means of

Laser radiation. FIG. 5 shows a perspective view of a tool changer for a machine tool for producing or processing a shaped body or workpiece by means of FIG

Laser radiation.

Figure 6: (A) is a partially cutaway perspective view and (B) is a perspective view

View of a replaceable powder nozzle according to the invention.

Figure 7 Illustration of the principle of action of laser deposition welding.

Figure 8 (A) is a perspective view of a replaceable focusing module, (B) and

(C) are each sectional views of the exchangeable focusing module with different focal lengths of the focusing optics.

Detailed description of the invention with reference to an embodiment

In the following description of a preferred embodiment of the present invention, like reference characters designate like or similar components.

1 shows a schematic representation of a machine 1 for processing a workpiece 30 and / or for producing a shaped body 30 by locally selective solidification of material powder to coherent areas by means of laser radiation. The IV machine 1 has a machine frame 21, on which on the one hand a workpiece table 20 and on the other hand an optical module 2 are attached indirectly via adjusting axles 18, 19 on the one hand. The adjusting axles 18, 19 may each have a plurality of translatory (X, Y, Z) or rotary (φ, λ, θ) axes, which are adjustable in accordance with a machine control.

The design can be, for example, such that the optical module 2 is fastened to the machine frame 21 via one, two or three translatory adjusting axes 18 (X and / or Y and / or Z), while the workpiece table 20 is mounted via one, two or three rotary adjusting axes 19 is attached to the machine frame 21. Such a laser machine tool 1 generally has a closed cabin (not shown) in which, for example, a protective gas atmosphere can be built up, and which shields the working space from contamination.

On the workpiece table 20, a workpiece 30 can be releasably secured for editing. Alternatively, a shaped body 30 can be built up in layers on the workpiece table 20 by site-selective solidification of material powder. The machine 1 may, for example, be a five-axis laser machine tool for producing shaped bodies by means of site-selective solidification of material powder to coherent areas by means of laser radiation. The optical module 2 is in this case releasably attached to the adjusting axles 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 optical module 2 is fastened to the machine frame 21 via three translatory adjusting axes 18 (X, Y and Z) and the workpiece table 20 is arranged on the machine frame via two axes of rotation.

An exemplary representation of a five-axis laser machine tool 1 for the production of moldings by means of laser selective radiation of locally solidified material powder to coherent areas is shown in Fig. 4. The illustrated embodiment essentially corresponds to the machine 1 shown schematically in FIG. 1. The workpiece table 20 and the adjusting axes 18 of the optical module 2 are arranged in a process chamber 22 that can be closed essentially by a process chamber door 23. An outside of the process chamber 22 arranged display 24 serves as an interface between the user and machine control. For example, measured values and / or warning messages and / or control applications can be displayed on this display 24.

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

The tool changer 25 further has a storage surface for at least two focusing modules 13 with focusing optics 14 of different focal lengths. By means of two adjusting axes 25a, 25b, the focusing modules 13 and the powder nozzles 15 can be moved into the process chamber 22, so that they can be attached to the optical module 2. A method for changing the powder nozzles 15 or the focusing modules 13 will be described below. The tool changer 25 can be moved by means of the adjusting axes 25a, 25b into a tool chamber which can be separated from the process chamber 22 by means of a displaceable dividing wall. In the tool chamber, the focusing modules 13 and the powder nozzles 15 are present Pollution, for example, protected by material powder or by welding fumes, when a machining of the workpiece in the process chamber 22 is performed.

In Fig. 2, an embodiment of an optical module 2 is shown, which is detachably mounted on a control axis 18. The adjusting axis 18 is, for example, a translational axis which can be moved in the Z direction and which can be arranged on two further translation axes which can be moved in the X and Y directions, so that the optical module 2 can be moved in all three spatial directions. The optical module 2 is in particular mounted on the adjusting axis 18 in such a way that the laser beam exits the optical module 2 vertically downwards (parallel to the direction of gravity or in the Z direction). By moving the adjusting axes 18, a focus of the focused laser beam can thus be moved in space in three dimensions, in order to machine a workpiece or to build up a shaped body in layers. Thus, a molded body as in a 3D printer by merging material powder layer by layer are constructed.

The optical module 2 has a housing 8, in which a plurality of optical components is arranged. The housing 8 serves on the one hand as a mechanical platform for arranging the optical components and for protecting the optical components against mechanical influences. In the housing 8, a protective gas atmosphere can be established. For example, overpressure can prevent particles and dirt from entering the housing.

At an upper portion of the housing 8, a fiber coupler 10 is arranged, via which a laser beam from an optical fiber can be coupled. By using an optical fiber, laser light from a laser beam source can be reliably guided to the optical module 2. The flexible optical fiber allows the optics module 2, and thus the laser beam to move without having to move the laser beam source itself. Further, an optical fiber can provide a laser beam with a particularly uniform beam profile.

As a laser beam source, for example, a high-power solid-state laser can be used. These include, for example, doped YAG lasers. In particular, a Ytterbium-doped YAG disc 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 may be used as the beam source. Diode lasers can provide laser beams with a power of several watts up to several thousand watts. Thus, sufficient laser power can be provided for various machining and manufacturing processes.

Directly below the fiber coupler 10, a Kollirmationsoptikwechsler 3 in the housing 8 of the optical module 2 is arranged. A collimating optics 4 with a first focal length of, for example, 80 mm is arranged in such a collimating optical changer 3, that from the Fiber emerging laser beam is collimated to a diameter of about 36 mm. The collimating optical 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 be used to provide collimated laser beams with diameters between approx. 10 mm and 100 mm. As collimating optics 4, for example, suitable types of converging lenses may be used. A collimating optic 4 may consist of a single lens or comprise a plurality of lenses. Material, coating and other lens properties can be selected depending on the laser wavelength and laser power used.

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

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

Seven exemplary combinations of focal lengths of the collimation optics 4 and the focusing optics 14 are shown in Table 1 below. Table 1 lists by way of example also resulting values of the diameter of the collimated laser beam and the focused laser beam for a fiber core diameter of 600 μιτι on.

The smaller the beam diameter, the higher the laser intensity. In particular, smaller structures can be produced with a smaller beam diameter at the focal point of the laser beam. A smaller beam diameter at the focal point can be achieved with the same focal length of the focusing optics by 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 optical module 2 are exposed to a lower laser intensity are. Thus, the optical elements are less likely to be damaged because, for example, they are less heated.

Table 1: Seven exemplary combinations of collimating optics focal length and

Fokussieroptikbrennweite:

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

At an upper edge of the focusing module 13 fastening means, for example two clamping bolts 16 are arranged. The fastening means 16 also serve to ensure the highest possible positioning accuracy of less than 1 mm. This is especially important for the accurate beam guidance of the laser beam through the powder nozzle and to the correct operating point. If deviations nevertheless occur, this can be detected by the camera 9 and corrected by the deflecting mirrors 6, 7. The focusing module 13 has at least one protective glass 14a for protecting the focusing optical system 14 from dirt or damage. Preferably, as shown in the sectional drawings of Fig. 8B and C on both sides of the focusing optics 14 each have a protective glass 14a arranged in the focusing module 13 to protect the focusing optics 14 from both sides from contamination or mechanical action.

The temperature of the at least one protective glass 14a can each be monitored by a sensor 13a. In Figs. 8B and C, only the temperature of the upper protective glass 14a becomes first from the laser beam is monitored by a sensor 13a. As a sensor, for example, a temperature-dependent resistor (NTC resistor) or a thermocouple can be used. The thermocouple may 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 collimating optics 4, the protective glasses of the collimating optics 4, the deflection mirror 6, 7 and / or the focusing optics 14 can be monitored.

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

The interfaces 13b may also serve to signal the machine controller to successfully attach a focus module 13. Accordingly, the machine control can detect that the focusing module 13 has been successfully released and stored when a signal transmitted via the interfaces 13b is interrupted.

The replaceable powder nozzle 15 according to the invention can be fastened under the focusing module 13 which can be fastened to the optical module 2. An exemplary embodiment of the powder nozzle 15 is shown in FIGS. 6A and 6B. The powder nozzle 15, like the focusing module 13, has fastening means 16 which can be fastened to the optical module 2 by means of appropriate receptacles 12. As a fastening means 16, for example, a plurality of clamping bolts may be arranged on the powder nozzle 15. Such clamping bolts are similarly used for mounting tools in conventional machine tools. The receptacles 12 on the optical module 2 can clamp these clamping bolts for fastening the powder nozzle 15 via a hydraulic, pneumatic, electromagnetic or tensioned by a spring mechanism so that the powder nozzle 15 is releasably secured to the optical module 2, wherein within a predetermined tolerance always the same position Pulverdüse 15 can be achieved. The powder nozzle 15 shown in FIGS. 2 and 6 has at the upper end facing the optical module 2 a flange 15a on which the fastening means 16, for example two clamping bolts, are arranged. On the flange 15 a, a substantially cylindrical central portion of the powder nozzle 15 is arranged. At the lower end of the central portion, a substantially conical powder nozzle tip 15b is arranged. The central portion of the powder nozzle 15, together with the flange 15a, may advantageously serve as a carrier with coolant and material powder feeds to which the powder nozzle tip 15b may be releasably secured. Thus, a change of the powder nozzle tip 15b can be made possible. At the flange 15a of the powder nozzle 15 are connections 15f, 15g or interfaces for supplying a coolant or a material powder arranged. The connections 15f for the coolant can be designed, for example, as quick-release couplings, which automatically connect with corresponding lines on the optical module 2 when the powder nozzle 15 on the optical module 2 is fastened. The inlets 15g for the material powder may be formed as simple openings, which have a sealing ring. When attaching the powder nozzle 15 on the optical module 2, the inlets are pressed with the sealing rings to corresponding outlets on the optical module such that a gas-tight connection is formed.

The inlets 15g for material powder are respectively in flow communication with channels 15d for the material powder passing through the powder nozzle 15 to the tip 15b of the powder nozzle 15. In the tip 15b of the powder nozzle 15, an annular gap 15c is formed whose gap width can taper in the flow direction in order to achieve a nozzle effect. The transition between material powder channels 15d and annular gap 15c is shaped such that a circumferentially uniform distribution of the material powder is produced. For example, a plurality of holes may be provided in a transition from the material powder channels 15d to the annular gap 15c. The holes can cause a uniform distribution of the material powder P in the annular gap 15c. The flow of material powder P may be in the form of a cone coaxial with the focal point of the laser beam, as indicated by the illustration of FIG.

The powder nozzle tip 15b may be detachably attached to the powder nozzle 15 so that it may be exchanged by heat, for example, when damaged or deformed. In a multi-part structure of the powder nozzle 15, 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. Different sized powder nozzle tips 15b may be used for different laser beam diameters, for example. Furthermore, differently dimensioned annular gaps 15c with different opening widths can be formed in exchangeable powder nozzle tips 15b. Accordingly, different powder nozzles 15 with different dimensioned powder nozzle tips 15 b are kept in the machine 1, so that if necessary, the entire powder nozzle 15 can be replaced. The diameter of the lower opening of the powder nozzle tip 15b facing the workpiece may be, for example, 1 mm, 2 mm, 3 mm, 4 mm or 5 to 8 mm. The replacement of the powder nozzle tips 15b is preferably carried out manually, while the change of the entire powder nozzle 15 as described below can be carried out fully automatically.

The powder nozzle 15 has at least two couplings 15f for coolant, which are preferably designed as quick couplings. A coupling 15f serves as a connection for the flow of the coolant from the optical module 2, the other coupling 15f serves as a connection for the return of the coolant to the optical module 2. The connections 15f for coolant are in fluid communication with coolant channels 15e in the powder nozzle 15, which in the partial cut view of Fig. 6A are illustrated. The coolant channels 15e may, for example, be arranged annularly, helically or helically around the laser beam opening in order to ensure uniform cooling of the powder nozzle 15.

Inside the flange 15a, a substantially cylindrical recess for the focusing module 13 is formed. When the focusing module 13 and the powder nozzle 15 are attached to the optical 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 with one another and with the laser beam on the optical module 2.

The powder nozzle 15 has due to the plurality of channels for coolant 15e and channels for material powder 15d, as well as with their axial direction to the laser focal point tapered axial opening a very complex shape. Such a complex shape can be produced, for example, by a laser deposition welding method in a machine 1 according to the invention. In order to carry out the manufacturing process of the powder nozzle 15 by laser deposition welding in as little time and with the highest possible savings of material, for example, the substantially cylindrical central portion of the powder nozzle 15 can be constructed with the thinnest possible wall thickness. In order to increase the mechanical strength of the powder nozzle 15, the wall may be reinforced by fins 151. Similarly, the transition between flange 15a and middle portion of the powder nozzle 15 can be fabricated to save material, for example by using a honeycomb structure 15w as shown in Fig. 6B, which provides high mechanical strength with low material consumption.

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

The replacement of the powder nozzle 15 can be carried out, for example, as described below. The partition between the process chamber 22 and the laterally disposed tool chamber is pushed. By means of the adjusting axis 25b, the lower part of the tool changer 25 is moved with the powder nozzles 15 in the process chamber 22. The adjusting axles 18 move the optical module 2 to the position at which the tool changer 25 with the plurality of powder nozzles 15 is located. For depositing a powder nozzle 15 attached to the optical module 2, unlike in FIGS. 4 and 5, a storage position of the tool changer 25 must be free. By opening the receptacles 12 on the optical module 2, the fastening means 16 of the powder nozzle 15 are released, so that the powder nozzle 15 is released from the optical module 2 and can be stored at a free storage position of the tool changer 25.

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

The automatic change of the powder nozzle 15 can take place in particular when the focal length of the laser beam is changed by a change of the focusing optics 14. Since the powder nozzle 15 is to guide 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 may be, for example, 200 mm or 300 mm. Correspondingly, corresponding powder nozzles 15 can be held in the tool changer 25 of the machine 1, which guide material powders to a focal point, for example 200 mm or 300 mm away from the focusing optics 14. Via the powder nozzle 15, a material powder at the operating point of the machine 1, ie in the immediate vicinity of the focal point of the laser beam, can be provided. For this purpose, the powder nozzle 15 has a channel or more channels through which the material is passed powder. When attaching the powder nozzle 15 to the optical module 2, a connection of the channels for the material powder with corresponding lines in the optical module 2 is produced. For connecting the channels and the lines, the powder nozzle 15 or the optical module 2 each have suitable interfaces. Furthermore, the powder nozzle 15 has a cooling channel or a plurality of cooling channels, in which a fluid coolant, in particular water, for circulating the powder nozzle 15 can circulate. The optical 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.

Furthermore, the powder nozzle 15 can conduct a protective gas to the operating point of the machine 1, so that unwanted reactions can be largely suppressed when the material powder melts in the focal point of the laser beam. The protective gas serves in particular to displace oxygen from the air. In particular, inert gases such as argon can be used as protective gas. For supplying the protective gas, the optical module 2 corresponding lines. The protective gas can also be supplied together with the material powder as a carrier gas. Thus, the inert gas serves on the one hand to prevent a reaction with atmospheric oxygen and on the other hand to convey the material powder.

During automatic replacement of the powder nozzle 15, the cooling lines of the optical module 2 with the cooling channels of the powder nozzle 15 are automatically connected or disconnected via the corresponding interfaces. Accordingly, the lines for material powder in the optical module 2 with the material powder channels in the powder nozzle 15 are automatically connected or separated via the corresponding interfaces. The corresponding interfaces for the lines and channels can be designed to be releasable and, for example, each be controlled via a hydraulic or pneumatic. An automatic change of the focusing module 13 can be done in a similar manner as the automatic change of the powder nozzle 15. In this case, the upper part of the tool changer 25 is moved by means of the control axis 25a with the focusing modules 13 in the process chamber 22. To change the focusing module 13, however, a powder nozzle 15 attached to the optical module 2 must first be released. This is done as described above by the powder nozzle 15 is deposited at a free storage position of the tool changer 25. The adjusting axes 18 then move the optical module 2 to a position at which the tool changer 25 is located with the plurality of focusing modules 13. The focusing module 13 fastened to the optical module 2 can be released by opening the receptacles 11 on the optical module 2, so that the focusing module 13 detached from the optical module 2 and can be stored at a free storage position of the tool changer 25. In the following, another focusing module 13 can be attached to the optical module 2. For this purpose, the optical module 2 is moved such that the fastening means 16 of the focusing module 13 engage in the receptacles 11 on the optical module 2. The receptacles 11 on the optical module 2 can now clamp the fastening means 16, for example via a hydraulic, pneumatic or tensioned by a spring mechanism to attach the focusing module 13 to the optical module 2. Subsequently, the tool changer 25 can be moved back into the detachable tool chamber and the processing of the workpiece can be started or continued.

The required travel paths of the adjusting axles 18, 25a, 25b can be stored in a memory of the machine control, so that the changing of the focusing module 13 or the powder nozzle 15 can be carried out fully automatically. The change 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 produced of the workpiece 30 or of the shaped body 30, a suitable diameter of the laser beam is selected at the focal point. The smaller the diameter of the laser beam at the focal point, the smaller the structures can be made. The diameter of the laser beam determines the focal length of the focusing optics 14 and of the collimation optics 3, as shown in Table 1. Thus, a suitable combination of collimating optics 4 and focusing optics 14 can be selected for each machining operation. Depending on the selected collimating optics 4 and focusing optics 14, a suitable powder nozzle 15 is again selected and attached to the optics module 2. On the one hand, the opening of the powder nozzle tip 15b must be large enough so that the laser beam L can pass unhindered. On the other hand, the opening of the powder nozzle tip 15b should be small enough to cause a favorable and uniform flow of the material powder P through the annular gap 15c to the focal point of the laser beam L. Correspondingly, a suitable collimating optical system 4 is adjusted on the collimating optical changer 3 and a suitable focusing module 13 and a corresponding powder nozzle 15 are fastened to the optical module 2 in accordance with the selected structure size.

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. For the wavelength of the laser beam, which is for example in the infrared spectral range, the dichroic mirror 7 is reflective. For visible light, however, the dichroic mirror may be permeable. Behind the dichroic mirror 7, a camera 9 may be arranged to monitor the manufacturing process. The camera 9 is viewed along the laser beam through the dichroic mirror and through the focusing optics 14 to the focal point of the laser beam arranged. Thus, with the camera 9, the operating point on the workpiece or the molded article to be manufactured can be monitored. Furthermore, by monitoring the laser beam by means of the camera 9, it can be prevented that the laser beam strikes the powder nozzle 15 directly and strongly heats or damages it.

The operating principle of the laser deposition welding is illustrated with reference to FIG. 7. 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 is coaxial with the powder nozzle 15 and is focused on an operating point on the workpiece W. The material powder P is passed 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 thereby transports the material powder P. The inert gas G, such as argon, also serves to prevent unwanted reactions of the heated material powder P or the workpiece W with atmospheric oxygen.

The features disclosed in the foregoing description, the claims and the drawings may be of importance both individually and in any combination for the realization of the invention in its various forms.

LIST OF REFERENCE NUMBERS

1 laser machine tool

2 optics module

3 collimation optics changer

4 collimation optics

6 first deflection mirror

7 second deflecting mirror (dichroic mirror)

8 housing

9 camera

10 fiber couplers

11 Interface for focusing optics

12 interface for powder nozzle

13 focusing module

13a thermocouple

13b Interface of the thermocouple

14 focusing optics

14a protective glass

15 powder nozzle 15a powder nozzle flange

15 b powder nozzle tip

15c annular gap

15d material powder channel

15e cooling channel

15f coolant coupling

15g material powder inlet

151 lamellae

15w honeycomb structure

16 clamping bolts

17 beam path of the laser

18 adjustment axes of the tool

19 adjustment axes of the workpiece table

20 workpiece table

21 machine frame

22 process chamber

23 process room door

24 display

25 tool changer

25a positioning axis of the focusing optical changer

25b Adjusting axis of the powder nozzle changer

30 workpiece

L laser beam

W workpiece

P workpiece powder

G protective gas and / or carrier gas

Claims

claims

1. powder nozzle (15) for a machine (1) for machining workpieces and / or for the production of moldings by site-selective solidification of material powder to coherent areas by means of a laser beam, comprising:

a substantially rotationally symmetrical base body with an axial passage opening for the laser beam;

Fastening means (16) for releasably securing the powder nozzle (15) to a laser processing head (2) of the machine (1), characterized in that

the powder nozzle (15) has means for cooling the powder nozzle (15).

2. powder nozzle (15) according to claim 1, wherein the fastening means (16) comprise at least two clamping bolts. 3. powder nozzle (15) according to claim 1 or 2, wherein as means for cooling the

A powder nozzle (15) comprises a coolant circuit having at least a coolant supply (15f) for supplying the coolant, a coolant return (15f) for returning the coolant, and a cooling passage (15e) for communicating flow from the coolant supply (15f) through the powder nozzle (15) Coolant return (15f) represents, is provided.

4. powder nozzle (15) according to claim 3, wherein the at least one coolant supply

(15f) and the at least one coolant return (15f) each having at least one quick coupling for connection to a coolant flow and a coolant return. 5. powder nozzle (15) according to any one of the preceding claims, wherein the powder nozzle

(15) has a plurality of channels (15 d) for material powder for conveying powder off Werkst to a focal point of the laser beam.

A powder nozzle (15) according to claim 5, wherein the powder nozzle (15) has a plurality of inlet openings (15g) for supplying material powder into the plurality of channels (15d) for

Has material powder.

7. powder nozzle (15) according to any one of the preceding claims, wherein the powder nozzle (15) has a tip (15 b) with an annular gap (15 c) which is adapted to direct the material powder circumferentially uniformly from all sides to an operating point of the laser ,

8. powder nozzle (15) according to claim 7, wherein the tip (15 b) is releasably attached to the powder nozzle (15).

9. powder nozzle (15) according to any one of the preceding claims, wherein the powder nozzle (15) comprises means for measuring the temperature of the powder nozzle (15).

10. Machine (1) for machining workpieces and / or for the production of moldings by locally solidifying material powder to coherent areas by means of a laser beam, characterized in that the machine has a powder nozzle (15) according to at least one of claims 1 to 9 ,