Apparatus for thermally processing a workpiece using a laser beam and protective hood suitable for thermally processing a workpiece using a laser beam

Abstract

The present invention relates to an apparatus for thermally processing a workpiece using a laser beam, the apparatus having a fiber laser generating a laser beam with a wavelength in the range of 1020 nm to 1120 nm, a) the apparatus includes a laser processing machine, the laser processing machine having a mounting surface for the workpiece, a laser processing unit with a laser processing head, and a moving unit with a lateral gantry for moving the laser processing head relative to the mounting surface, b) the apparatus includes a laser protection hood, the laser protection hood surrounds the laser processing head, opens toward the mounting surface, is movable together with the laser processing head by the moving unit, has an outer wall and an inner wall, a hollow space is provided between the outer wall and the inner wall, and at least one laser light sensor is arranged in the hollow space, and c) the apparatus includes a laser protection housing, the laser protection housing surrounds the laser processing machine and the laser protection hood in a hood-like manner.

Description

[Technical field]

[0001] Background technology The present invention relates to an apparatus for thermally processing a workpiece using a laser beam, the apparatus comprising a fiber laser for generating a laser beam having a wavelength in the range of 1020 nm to 1120 nm, and a laser processing machine, the laser processing machine being: a support surface for the workpiece; a laser processing unit having a laser processing head; A moving unit including a lateral gantry for moving a laser processing head relative to a mounting surface, the lateral gantry having a support beam extending above the mounting surface, the support beam being supported on a side of the mounting surface and capable of traveling on a traveling track; and The present invention relates to an apparatus having the following structure:

[0002] Furthermore, the invention relates to a laser protective hood for a laser processing head of a laser processing machine, the laser processing machine being equipped with a fiber laser which generates a laser beam with, inter alia, a wavelength in the range of 1020 nm to 1120 nm.

[0003] The device according to the invention is designed for thermal processing of workpieces with a laser beam. The term "thermal processing" includes welding, cutting or marking of workpieces. For thermal processing of workpieces, a fiber laser is used according to the invention, which generates a laser beam with a wavelength in the range of 1020 nm to 1120 nm, among others.

[0004] A "laser processing machine" in the sense of the present invention comprises a workpiece placement surface, a laser processing unit and a movement unit in the form of a transverse gantry arranged transversely to the longitudinal axis of the work table, on which the laser processing head is arranged. A "laser processing head" is a movably supported machine part for emitting a laser beam in the direction of the placement surface. The laser processing head usually includes the focusing optics of the laser processing unit. The movement unit is designed in such a way that the laser processing head can be moved in space by means of it, preferably in all three spatial directions.

[0005] In the case of a fiber laser, the laser beam is formed by a laser active doping material in the core of a glass fiber. The laser active core is surrounded by a cladding with a relatively low refractive index. Fiber lasers are distinguished, among other things, by efficient excitation of the laser active medium (by a laser diode), by relatively simple beam guidance in optical waveguides, and by high beam quality. A fiber laser suitable for thermal processing of materials is, for example, the ytterbium laser.

[0006] Prior Art Known devices used for the thermal processing of metallic workpieces are often surrounded by protective elements, which are intended to protect humans and also sensitive objects in the vicinity of the device from unintended effects of the laser beam. A simple example of such a protective element is a housing surrounding the device.

[0007] When using fiber lasers with wavelengths in the range of 1020 nm to 1120 nm, special demands are made on the protective elements because, in contrast to CO2 lasers, with these lasers dangers arise not only from the direct or reflected laser beam but also from diffuse scattered light. This is due to the fact that the wavelengths of fiber lasers are located close to the visible range. This means that the laser beam can strike the retina instead of being absorbed in the lens of the eye, as is the case with CO2 lasers. Even very small leaks in the protective elements can be dangerous. Effective protection can be achieved by a complete housing, which usually contains several modular protective elements connected to each other.

[0008] In the simplest case, the protective element is designed to withstand a certain duration of irradiation by a laser beam. Such protective elements are also called passive protective elements. The housing of the passive protective element is usually made of a more or less thick metal plate. When using a fiber laser, the passive protective element must have a relatively large wall thickness. The disadvantage of passive protective elements is that they require the use of a large amount of material. A complete housing is therefore heavy, space-consuming and correspondingly expensive.

[0009] For the reasons mentioned above, instead of passive protective elements, active protective elements with sensor elements are often used for the housing, which can recognize imminent or actual damage to the protective element. If damage is recognized, the laser processing unit is usually automatically switched off. Active protective elements can be manufactured from relatively thin metal plates. Active protective elements are less durable than passive protective elements, but can therefore be manufactured more simply and more cost-effectively. Active protective elements are often constructed with a double wall, in which case the sensor element is a laser light sensor arranged in the hollow space of the double wall, which is designed to recognize the laser beam impinging on this laser light sensor.

[0010] However, the known laser light sensors only have a limited detection range, which allows them to reliably detect impending damage. In the case of relatively large housings in particular, it is often necessary to use a large number of laser light sensors. However, it is fundamentally desirable, both from the standpoint of cost and from the standpoint of technical complexity, to keep the number of laser light sensors and also the entire sensor technology as low as possible.

[0011] Therefore, in DE 10 2014 116 746 A1, a modular active laser protection wall is proposed, in which each wall module is not provided with a radiation sensor, but instead the side surfaces of the wall modules are designed as open as possible, so that a laser beam incident on a wall module where no radiation sensor is arranged can be deflected towards a wall module where a radiation sensor is arranged.

[0012] However, due to the limited detection range of the known laser light sensors, a large number of laser light sensors are still required in the case of relatively large protective housings. This is especially true for protective housings that are longer, wider and / or have protective walls that are higher than 5 m. However, even in the case of several laser protective walls arranged at an angle to one another, in most cases at least one own laser light sensor is provided for each of these laser protective walls, and even several laser light sensors are provided in the case of relatively long laser protective walls.

[0013] A two-dimensional fiber laser cutting installation is known from DE 202018105888. The cutting installation comprises a machine table and a longitudinally movable gantry with a cutting head. The cutting installation is provided with a full-length housing that encloses the working space of the cutting installation in the form of a hood.

[0014] EP 3308898 A1 discloses a protective housing for a machine for material processing of workpieces with the laser beam of a fiber laser. The protective housing is attached to the end of a robot arm and is of double-walled construction. The spaced-apart walls of the protective housing enclose a hollow space in which a sensor for the electromagnetic beam can be arranged.

[0015] DE 10 2012216632 A1 discloses a laser cutting machine with a protective element for shielding the laser processing head, which is configured as a hollow space in which a sensor for detecting the laser beam is arranged, which is connected to a control device with which the laser can be switched off.

[0016] From German utility model DE 202007012255 A1 a housing for a laser cutting machine is known, which has a partial volume defined by walls spaced apart from one another at a distance within a range of approximately 35 mm, and a unit for detecting the laser beam, which passes through the housing, is composed of receivers and transmitters arranged on a circle concentrically surrounding the receivers.

[0017] DE 102017002649 relates to a laser cutting machine with a laser protective housing and a sealing brush assembled to the laser protective housing and bordering the housing in the direction of the surface. The sealing brush is made of graphite and / or a fibre-metal composite and is under high voltage. A safety sensor adapted to the electrical conductivity of the sealing brush bristles is used to switch off the laser. A laser cutting machine with a protective cover in which the brush assembly is included is also described in EP 3402625.

[0018] DE 10 2019207 940 A1 describes an unbalance measuring device for a rotating body, in which the generated unbalance force is detected by a force sensor, and from the results the unbalance of the rotating body and the required unbalance compensation are calculated. To realize the unbalance compensation, a laser beam is incident on the rotating body. For example, the laser is configured as a continuously operating fiber laser with a laser power of, for example, 12 kW (kilowatts), the wavelength being adapted, inter alia, to the material of the rotating body to be removed. For example, in the case of carbon steel, a fiber laser with a wavelength of about 1060 nm is used.

[0019] WO 2020 / 117816 discloses a high-power all-fiber laser system with multiple spaced apart fiber lasers integrated together via a tapered fiber combiner, which includes a central guide fiber and multiple peripheral guide fibers, allowing different laser powers and laser beam shapes to be realized depending on the type and number of fiber lasers switched on.

[0020] DE 100 59 246 A1 describes a protection device for handheld laser machines, inter alia for laser engraving, on which a sealing element can be coupled, which has a tubular or conical area surrounding the laser beam during operation.

[0021] Technical challenges The problem underlying the present invention is therefore to provide an apparatus for thermal processing of workpieces by means of a fiber laser, which is operationally safe, simple to operate and particularly cost-effective.

[0022] Furthermore, the problem underlying the invention is to provide a laser protection element for such an apparatus which is operationally safe, simple to operate and particularly low-cost.

[0023] Summary of the Invention With regard to the device, the above-mentioned problem is solved according to the invention by providing a device for thermal processing of a workpiece by means of a laser beam, the device having a fiber laser generating a laser beam with a wavelength in the range of 1020 nm to 1120 nm, a) The apparatus includes a laser processing machine, a support surface for the workpiece; a laser processing unit having a laser processing head; A moving unit including a lateral gantry for moving a laser processing head relative to a mounting surface, the lateral gantry having a support beam extending above the mounting surface, the support beam being supported on a side of the mounting surface and capable of traveling on a traveling track; and having b) the apparatus includes a laser protective hood, the laser protective hood surrounds the laser processing head, is open toward the placement surface, is movable together with the laser processing head by the moving unit, has an outer wall and an inner wall, and a hollow space is provided between the outer wall and the inner wall, and at least one laser light sensor is arranged in the hollow space; c) the apparatus includes a laser protective housing, the laser protective housing surrounding the mounting surface, the laser processing unit, the moving unit, and the laser protective hood in a hood-like manner; This is solved by the device.

[0024] When a laser processing machine with a fiber laser is used to process workpieces, an outer protective housing is required, which is relatively expensive, especially when the length of the workpiece exceeds 5 m, because several laser light sensors are required and the signal detection is correspondingly laborious.

[0025] The idea behind the invention is to additionally provide the laser processing head with a separate inner laser protection hood, which on the one hand completely prevents the escape of a directional laser beam and sufficiently prevents the escape of a divergent laser beam, and on the other hand also withstands the foreseeable maximum irradiation itself. This presupposes a suitable design of the inner laser protection hood, more particularly with regard to the durability of the laser protection hood against the laser beam and also with regard to the sealing of the laser protection hood against the light beam. Known laser protection hoods, as used, for example, in devices with CO2 laser sources, are no longer suitable as protection hoods for fiber lasers, since they are not constructed as double-walled and do not provide active protection against high laser powers. Furthermore, it has been found that in the case of these known protection hoods, problems exist in the area between the protection hood and the workpiece or between the protection hood and the support surface, since this area is not optimally sealed against back reflections.

[0026] Due to the fact that the laser protection hood according to the invention is configured as a double-walled active protection hood with at least two laser light sensors, the laser protection hood has a smaller weight than a passive protection hood for the same level of protection. This has several advantages: on the one hand, the laser protection hood can be moved more easily relative to the resting surface, and the movement unit also has to meet lower requirements. On the other hand, however, it is also possible to move the laser processing head more precisely, since the laser processing head is entrained when the laser protection hood is moved.

[0027] According to the invention, at least one laser light sensor is arranged in the hollow space of the laser protection hood. With an appropriate size and geometry of the laser protection hood, the hollow space can be completely monitored for the incidence of laser light to the side and above by using only one laser light sensor. However, depending on the size and geometry of the hollow space, it is also advantageous to use several laser light sensors.

[0028] However, it has been found to be advantageous in this case if the hollow space comprises a number of partial spaces, in each of which at least one laser light sensor is arranged. Advantageously, the partial spaces are adjacent to one another and follow one another. The provision of a number of partial spaces ensures that sufficient safety is guaranteed with regard to the detection of the laser beam incident on these partial spaces, even in the case of a relatively large laser protection hood, and even in the case of a laser protection hood with a complex geometric shape. Furthermore, the assignment of a respective laser light sensor to the partial spaces also makes it possible to easily localize damage to the laser protection hood.

[0029] Due to the shape of the hood, the laser protection hood cannot be completely sealed against the divergent laser beam only in the direction facing the workpiece surface or the mounting surface. The laser protection hood cannot therefore completely replace the outer protective housing. However, if the dimensions of the laser protection hood are selected larger, the leakage of the divergent laser beam can be reduced. Furthermore, the provision of the laser protection hood places lower demands on the outer protective housing in terms of laser resistance. This has the advantage that instead of a large active outer protective housing with multiple laser light sensors, a low-cost single-walled laser protection housing with a small wall thickness can also be used. For example, in the case of a laser protection housing made of sheet metal, a wall thickness in the range of 1.5 mm to 2.5 mm is usually sufficient. Such a laser protection housing does not require a significant amount of material and is therefore significantly less expensive. Furthermore, laborious control and inspection of the sensors in the outer protective housing is omitted.

[0030] The laser protective housing surrounds the mounting surface, the laser processing unit, the moving unit and the laser protective hood in a hood-like manner, i.e. laterally and upwardly, and is open downwards, i.e. on the bottom side, but is sealed against the bottom so that neither the directional beam nor the diffusely scattered beam can escape from the laser protective housing.

[0031] In a preferred embodiment of the device according to the invention, the laser processing machine has a first mounting surface for a first workpiece and a second mounting surface for a second workpiece, and the laser protective housing is movable such that the laser protective housing surrounds either the first mounting surface or the second mounting surface.

[0032] In order to be able to thermally process a workpiece in the device according to the invention, it must be transferred onto the support surface before thermal processing and removed from the support surface again after thermal processing. This can be carried out, for example, by means of a crane or other lifting device. However, in the case of a device with a protective housing, positioning the workpiece on the support surface and removing it are already difficult, since only limited space is provided for this, even when the laser protective housing is partially opened. If the device comprises two support surfaces and the laser protective housing can be moved between a first position surrounding the first support surface and a second position surrounding the second support surface, the loading and unloading of the workpiece is facilitated. This has the advantage that one of the support surfaces is located inside the laser protective housing, while the other support surface is arranged outside the laser protective housing. The support surface located outside the laser protective housing can be simply and quickly loaded, prepared for further processing and finally removed again, while at the same time the workpiece located on the other support surface can be thermally processed, which reduces downtimes and shortens process times.

[0033] Furthermore, the smaller the mass of the laser protection housing, the easier it is to move between the first and second positions. By providing the inner laser protection hood, the outer laser protection housing can be constructed as a single wall without a laser light sensor. This not only makes the laser protection hood lighter, but also eliminates the need to ensure that the electrical contacts of the laser light sensor are not damaged by the movement of the laser protection housing. Both of these factors make it much easier to move the laser protection housing.

[0034] It has proven to be advantageous if the laser protective hood has an upper hood region that is configured in the shape of a dome, a cone or a truncated pyramid and at least two laser light sensors are arranged in the upper hood region.

[0035] The laser light sensor can detect adjacent partial spaces of the hollow space that are bent at an angle of up to 45° together, as long as these partial spaces are connected to one another. The laser protection hood surrounds the laser processing head laterally and from above. Angular laser protection hoods with walls that are bent at an angle of more than 45° usually require the use of a laser light sensor or a suitable reflector, for example a mirror, in both walls of the laser protection hood. This applies in particular to the upper hood area. A dome-shaped, conical or truncated pyramidal upper hood area contributes to avoiding bending at angles of more than 45°. This shape of the upper hood area allows the number of laser light sensors to be kept as low as possible. This not only reduces costs, but also reduces the effort for electrical contacting of the sensors and thus the weight of the laser protection hood, which makes it easier to move the laser protection hood. In the ideal case, for the entire upper hood area, only one laser light sensor, arranged in the center of the upper hood area, is sufficient. Preferably, the number of laser light sensors in the laser protection hood is less than 10, particularly preferably less than 6.

[0036] It has proven expedient if at least two laser light sensors, preferably at least three laser light sensors, particularly preferably at least four laser light sensors are arranged in the hollow space.

[0037] Depending on the size and the exact geometry of the hollow space, one laser light sensor may not be sufficient to reliably detect the laser beam incident in the hollow space. The hollow space therefore preferably has at least two, preferably at least three, particularly preferably at least four laser light sensors. The hollow space preferably has a number of subspaces corresponding to the number of laser light sensors, in each of which one of these laser light sensors is arranged. In this case, it has proven to be advantageous if at least one laser light sensor is arranged in the upper hood area. Preferably, at least two laser light sensors are arranged in the upper hood area. The remaining laser light sensors are preferably arranged outside the upper hood area. The upper hood area represents the hood lid. In the upper hood area, the regular bends of the hollow space make it difficult to detect the laser beam incident in this upper hood area. If one laser light sensor is provided in the upper hood area, it has proven effective to arrange the laser light sensor as centrally as possible with respect to the upper hood area, for example in the center of the dome if the upper hood area is dome-shaped.If two or more laser light sensors are arranged in the upper hood area, it has proven effective to arrange the laser light sensors symmetrically with respect to the central longitudinal axis of the laser protective hood.

[0038] In a preferred modification of the device according to the invention, the laser processing head has a working axis and can be swiveled relative to the laser protective hood in such a way that, both when swiveling in the x-direction and when swiveling in the y-direction, the working axis forms a swiveling angle α of up to 50° with the surface normal of the mounting surface, and the laser protective hood is dimensioned such that the laser beam reflected by the workpiece, which is ideally flat, impinges on the inner wall of the laser protective hood regardless of the swiveling angle α.

[0039] The laser protective hood can surround a vertical laser processing head, but can also surround a laser processing head for chamfer cutting.

[0040] The vertical laser processing head is oriented perpendicular to the mounting surface during the cutting process and is moved in the x-, y- and z-directions by the moving unit. Compared to the laser processing head for chamfer cutting, the dangers arising from the vertical laser processing head are fundamentally smaller, since the reflected laser beam is usually reflected vertically and is blocked by the laser processing head itself, i.e. does not strike the wall of the laser protection hood in the normal case. However, even when using a vertical laser processing head, the beam that strikes the mounting surface or the workpiece perpendicularly can be reflected obliquely outward by the workpiece, for example, which is tilted relative to the mounting surface, and pass by the side of the laser processing head.

[0041] In addition to the movement in the x-, y- and z-directions, the laser processing head for chamfer cutting can be swiveled in two further axes by the movement unit. These axes are often referred to as the a- and b-axes. The swivelling ability of the laser processing head relative to the rest surface allows the cutting of chamfers on the workpiece. The swivelling ability of the laser processing head in both the x (a) and y (b) directions allows the cutting of chamfers even in the case of curved cutting shapes. With a swivelling angle α of up to 50°, chamfer angles in the range of 0°-50° can be generated. Advantageously, the swivelling angle α is infinitely adjustable. When using a laser processing head for chamfer cutting, the laser beam often strikes the workpiece surface at a flat angle (0°-50° to the perpendicular). The reflected beam will therefore strike the wall of the laser protection hood with a much higher probability. The use of such a laser processing head therefore also entails a greater potential danger. The maximum adjustable swivel angle α has an effect on the size of the laser protection hood. That is, under the condition that the laser beam reflected by the ideally flat workpiece should strike the inner wall of the laser protection hood regardless of the swivel angle α, for a given distance between the workpiece and the laser protection hood, the laser protection hood must be dimensioned larger as the permissible swivel angle α increases. A swivel angle α of up to 50° is sufficient for most thermal processing methods.

[0042] Advantageously, the hollow space between the outer wall and the inner wall has a hollow space width in the range of 35 mm to 50 mm, preferably in the range of 40 mm to 50 mm.

[0043] A hollow space width in the above-mentioned range has technical advantages, since it has an influence on the sealing of the laser protection hood against diffuse scattered radiation. The larger the hollow space width, the wider the free space covered by the laser protection hood to the workpiece or the support surface. In order for the scattered radiation to be able to penetrate outwards, it must pass through this free space without hitting the laser protection hood or the workpiece or the support surface. A hollow space with a width of less than 35 mm only suppresses diffuse scattered radiation to a limited extent. Furthermore, a hollow space with such a small hollow space width is only to a limited extent suitable for accommodating a laser radiation sensor. A hollow space width of more than 50 mm requires a laser protection hood with a relatively large volume. In the case of a wide hollow space, a sensor element as large as possible is required in order to reliably detect the laser radiation. In order to be able to process the entire support surface, a certain space must be left around the support surface on all sides. This space increases as the hollow space width increases. A cavity width of more than 50 mm is accompanied by only a slight improvement in the tightness against scattered beams. A cavity width of 40 mm to 50 mm has been found to be particularly effective.

[0044] The laser protection hood is 0.5m above the mounting surface. 2 ~1.0m 2 It has been found that covering an area within the range of

[0045] The laser protection hood according to the invention differs from the known laser protection hoods in terms of its size. In this case, it basically applies that the larger the area covered by the laser protection hood on the support surface, the better the laser protection hood protects against the escape of diffuse scattered beams. However, the larger the laser protection hood, the greater its mass, the more inert it becomes and the more difficult it is to position it accurately together with the laser processing head. This has proved to be problematic precisely in the case of devices for thermal processing, since it is important to position and guide the laser beam as accurately as possible. The abovementioned area ranges have the following technical advantages: the laser protection hood can be covered on the support surface with a coverage area of ​​0.5 m2 or less. 2 If the laser protection hood covers an area of ​​less than 1.0 m above the mounting surface, the effect of the laser protection hood according to the present invention in preventing the escape of the diffuse scattered beam is lost. 2 When covering an area larger than this makes accurate positioning of the laser protective hood and laser processing head difficult.

[0046] In an advantageous embodiment of the device according to the invention, the laser protective hood has a lower edge which extends at a distance leaving a free space relative to the mounting surface, a laser protective curtain with flexible cover members is attached to the laser protective hood, the laser protective curtain protruding into the free space between the laser protective hood and the mounting surface, and is designed in such a way that damage to one of the cover members causes the laser beam to switch off the laser processing unit.

[0047] In order to avoid collisions between the laser protective hood and the workpiece, it is unavoidable that a free space is left between the lower edge of the laser protective hood and the mounting surface. However, this free space is a weak point of the laser protective hood, since diffusive scattered beams can escape from this free space. This applies in particular to laser beams that can penetrate the free space at a small angle to the mounting surface or to the workpiece surface. However, it is possible to reduce the proportion of scattered beams escaping from the free space by means of a laser protective curtain with a flexible cover element protruding into the free space. Inevitably, such a laser protective curtain has only a small distance to the laser beam and thus to the thermal processing process. Therefore, the laser protective curtain can also be easily damaged. In order to ensure that the laser protective curtain is always in a proper state, the protective curtain is designed in such a way that damage to the protective curtain can be identified, for example, by interruption of the current circuit. If damage is recognized, this results in the laser processing unit being switched off.

[0048] Advantageously, the moving unit has a horizontal travel path defined such that a minimum distance of 1440 mm is left between the laser protective hood and the laser protective housing, and the moving unit has a vertical travel path designed such that a minimum distance of 90 mm, preferably at least 100 mm, is left between the laser protective hood and the mounting surface.

[0049] The laser processing head is movable relative to the support surface by means of a moving unit. In this case, the laser processing head must be able to travel over the entire support surface by means of the moving unit and be positionable above the entire support surface. If the laser processing head is positioned at the edge of the support surface, the laser protection hood protrudes beyond the support surface. In order to avoid collisions between the laser protection hood and the laser protection housing, a minimum distance must be left between the laser protection housing and the laser protection hood. Furthermore, in order to avoid collisions, a minimum distance must also be left between the laser protection hood and the support surface. In this connection, it has proven to be useful if the laser processing head is movable in a direction perpendicular to the support surface by means of a moving unit. This makes it possible to easily adjust the distance between the laser protection hood and the support surface to different workpiece thicknesses. Furthermore, the possibility of moving the laser processing head in a direction perpendicular to the support surface can be used to prevent collisions between the laser processing head and taller parts of the workpiece.

[0050] The above-mentioned problems with regard to the laser protection element are solved according to the invention by a laser protection hood, which has an outer wall and an inner wall, between which a hollow space is provided, and in which at least one laser light sensor is arranged.

[0051] The laser protection hood according to the invention is designed to completely prevent the escape of directional laser beams and to sufficiently prevent the escape of divergent laser beams so as to withstand the maximum foreseeable irradiation, which presupposes a corresponding construction type of the inner laser protection hood, more specifically with regard to the durability of the laser protection hood against laser beams and also with regard to the sealing of the laser protection hood against light beams.

[0052] The laser protection hood according to the invention is configured as an active protection hood with at least one laser light sensor, double-walled, and has a smaller weight than a passive protection hood with the same level of protection. This has several advantages: on the one hand, the laser protection hood can be moved more easily relative to the resting surface, and the movement unit also has to meet lower requirements. However, on the other hand, it is also possible to move the laser processing head and the laser protection hood more precisely.

[0053] According to the invention, at least one laser light sensor is arranged in the hollow space. With the appropriate size and geometry of the laser protection hood, the hollow space can be completely monitored with respect to the incidence of the laser light, both to the side and above, by using only one laser light sensor. Due to its shape, the laser protection hood cannot be completely sealed against the divergent laser beam only in the direction facing the workpiece surface or the rest surface. The leakage of the divergent laser beam cannot be avoided, since there is always a possibility of back reflection, for example from the rest surface. The workpiece rest is formed of a narrow (3 mm to 10 mm) steel rest web arranged upright, for example with a sawtooth or corrugated upper surface. The horizontal distance between the parallel webs is typically 40 mm to 60 mm. Since the workpiece has only point-like contact points with the web, the slug released from the cutting gap can be discharged downwards to the cutting table as unhindered as possible. Any laser beam that escapes the cutting gap can impinge on the underside of the table and be diffusely reflected therefrom.

[0054] Therefore, the laser protection hood cannot completely replace the outer protective housing. However, if the dimensions of the laser protection hood are selected larger, the leakage of the divergent laser beam can be reduced. The laser protection hood according to the invention imposes lower requirements on the outer protective housing in terms of laser resistance.

[0055] In a preferred modification of the laser protective hood according to the invention, the laser protective hood has an upper hood region that is configured in a dome-, cone- or pyramidal shape, and at least two laser light sensors are arranged in the upper hood region.

[0056] The dome-, cone- or pyramidal-shaped upper hood area contributes to avoiding bending at angles of more than 45°. This shape of the upper hood area allows the number of laser light sensors to be kept as low as possible. This not only reduces costs, but also reduces the weight of the laser protection hood, which makes it easier to move. In the ideal case, only one laser light sensor, located in the center of the upper hood area, is sufficient for the entire upper hood area. Preferably, the number of laser light sensors of the laser protection hood is less than 10, particularly preferably less than 6.

[0057] Advantageously, at least two laser light sensors, preferably at least three laser light sensors, particularly preferably at least four laser light sensors are arranged in the hollow space.

[0058] Depending on the size and the exact geometry of the hollow space, a single laser light sensor may not be sufficient to reliably detect the laser beam incident in the hollow space. The hollow space therefore advantageously has at least two, preferably at least three, particularly preferably at least four laser light sensors. In particular, in the upper hood region, the regular bends of the hollow space make it difficult to detect the laser beam incident in this upper hood region.

[0059] Working Example In the following, the device according to the invention for the thermal processing of workpieces and the protective hood according to the invention are explained in more detail on the basis of the drawings. [Brief description of the drawings]

[0060] [Figure 1] FIG. 2 shows an apparatus according to the invention for thermal processing of workpieces, with a laser protective hood and a laser protective housing. [Diagram 2] FIG. 2 is a side view of a laser protective hood according to the present invention. [Diagram 3] FIG. 3 is a plan view of the laser protection hood according to the present invention of FIG. 2. [Figure 4] FIG. 3 is an exploded view of the laser protection hood according to the present invention shown in FIG. 2. [Diagram 5] 3 is a cross-sectional view of the laser protection hood according to the present invention taken along line A-A' of FIG. 2. [Figure 6] FIG. 1 shows three laser protection hoods (A, B, C) according to the invention with different hood geometries. [Figure 7] FIG. 2 shows a laser protection hood according to the invention with a laser protection curtain. [Figure 8] FIG. 3 shows the laser protection hood according to the invention of FIG. 2 in a moving unit with a lateral gantry.

[0061] Fig. 1 shows an apparatus 100 designed for thermal processing of metallic workpieces by means of a laser beam. The apparatus 100 is built on and connected to a base 117. For the purpose of explaining the apparatus 100 and its mode of functioning, Fig. 1 further shows two identical workpieces 101a, 101b made of steel, which workpieces 101a, 101b are not themselves part of the apparatus 100. The workpieces 101a, 101b each have a length of 12 m, a width of 3 m and a thickness of 25 mm.

[0062] The apparatus 100 includes a laser processing machine, a laser protective hood 110, and a laser protective housing 115. In detail, the apparatus 100 is as follows.

[0063] The laser processing machine includes a work table 102, a laser processing unit 104, and a moving unit 106.

[0064] The work table 102 is made of steel and has a length of 28 m, a width of 3850 mm, and a height of 720 mm. The work table 102 is provided with two mounting surfaces 103a, 103b, on which one or more workpieces can be placed, respectively. The two mounting surfaces 103a, 103b have a length of 13800 mm and a width of 3250 mm. In FIG. 1, the workpiece 101a is placed on the mounting surface 103a, and the workpiece 101b is placed on the mounting surface 103b.

[0065] In the present invention, the laser processing unit includes a fiber laser and a laser processing head, both not shown in FIG. 1. The fiber laser has a laser power of 10 kW and generates a laser beam with a wavelength of about 1070 nm. In the case of two other embodiments (both not shown), the fiber laser has a laser power of 16 kW or 20 kW. The laser beam emerging from the laser processing head is directed towards the working surface and thus towards the workpiece to be processed during operation.

[0066] The moving unit 106 includes a lateral gantry 107, and the laser processing head can be moved in the x-direction and y-direction relative to the placement surfaces 103a, 103b via the lateral gantry 107. The lateral gantry has a support beam 108, which extends above the work table 102 and is supported on the side of the work table 102. The lateral gantry 107 including the support beam 108 can travel on travel tracks 109a, 109b.

[0067] The laser protection hood 110 surrounds the laser processing head and is open only toward the mounting surfaces 103a and 103b. The laser protection hood 110 is constructed with a double wall, and therefore has an outer wall and an inner wall. The wall thickness of the inner wall and the outer wall is 2 mm each. A hollow space is provided between the outer wall and the inner wall, and two laser light sensors are arranged in this hollow space.

[0068] The laser protection housing 115 is used for protection against diffusely scattered light, for example light that may escape through the free space between the lower edge of the laser protection hood and the resting surface / workpiece. The laser protection housing 115 is formed from a single-walled sheet metal element 116 with a wall thickness of 2 mm. The laser protection housing 115 has a length of 15800 mm, a width of 8000 mm and a height of 3000 mm. For reasons of clarity of the drawing, only the side walls of the laser protection housing 115 are shown in FIG. 1. In fact, the ceiling of the laser protection housing 115 is also closed by a sheet metal element. The laser protection housing 115 is only open on the bottom side. For this reason, the laser protection housing 115 is optically sealed against the bottom 117. Otherwise, the laser protection housing 115 completely surrounds the laser processing unit, the moving unit 106 and the laser protection hood 110, but only partially surrounds the work table 102.

[0069] The laser protection housing 115 can move on the support rails 118a, 118b between a first position and a second position, where in the first position the first rest surface 103a is located inside the laser protection hood 110, and in the second position the second rest surface 103b is located inside the laser protection hood 110. The workpiece on the rest surface located inside the laser protection housing 115 can be processed by the laser processing unit. The workpiece to be processed can be simply loaded onto the rest surface located outside the laser protection housing 115, and after processing the workpiece can be removed again. The travel path of the moving unit 106 inside the laser protection housing 115 is limited, i.e. in the x- and y-directions it is selected so that a distance of 1500 mm is left between the laser protection hood 110 and the laser protection housing 115, and in the z-direction it is selected so that a distance of at least 90 mm is left between the laser protection hood 110 and the rest surface 103.

[0070] 2, 3 and 4 show a laser protection hood according to the invention in a side view, a plan view and an exploded view. The laser protection hood is generally assigned the reference number 210. The laser protection hood 210 is designed for a laser processing head of a laser processing machine with a high laser power. The laser processing head is not a constituent part of the laser protection hood 210. Nevertheless, in FIG. 2, for the sake of clarity, a laser processing unit with a laser processing head (X) is shown hatched. The laser protection hood 210 can be used instead of the laser protection hood 110 in the device of FIG. 1.

[0071] The laser protection hood 210 has a double wall with an inner wall (not shown in Figs. 2, 3, and 4) and an outer wall 220. The outer wall 220 and the inner wall of the laser protection hood 210 are each made of aluminum sheet metal with a sheet metal thickness of 2 mm. The outer dimensions (L x B x H) of the laser protection hood are (900 mm x 930 mm x 1600 mm). The laser protection hood 210 has a height of 0.76 m on a mounting surface (not shown here) associated with the laser protection hood 210. 2The area of ​​the laser beam sensor 221a is covered by the laser beam sensor 221b. Between the inner wall and the outer wall 220, a hollow space (not shown in Figs. 2, 3 and 4) is located. The hollow space width, i.e. the distance from the inner wall to the outer wall 220, is 50 mm. The hollow space includes three partial spaces 240a, 240b, 240c, the boundaries of which are shown diagrammatically as dashed lines in Fig. 4. In each of the partial spaces 240a, 240b, 240c, one of the three laser beam sensors 221a, 221b, 221c protrudes. The laser beam sensor 221a is arranged in the upper hood area 229. Due to the upper hood area 229 being configured in a pyramidal truncated shape and the laser beam sensor 221a being arranged in the center, it is possible to monitor the entire upper hood area 229 by one sensor. In an alternative embodiment, the upper hood area 29 is configured in a dome- or cone-shaped manner. The rear of the laser protection hood 210 is configured as a solid aluminum plate, on which an interlocking mechanism 222 is arranged, by means of which the laser protection hood 210 can be attached to the moving unit and at the same time allows the laser protection hood 210 to be tilted / tilted into an assembly position relative to the moving unit 106. For this purpose, two grips 223 are provided, by means of which the laser protection hood can be lifted upwards or swiveled. This ensures access to the laser processing head X, for example for manually replacing the cutting nozzle.

[0072] Figure 5 shows the laser protection hood 210 according to the invention from figures 2, 3 and 4 in a schematic cross-sectional view along A-A'. The laser protection hood 210 has an outer wall 220 made of aluminum sheet metal with a sheet metal thickness of 2 mm and an inner wall 230 made of aluminum sheet metal with a sheet metal thickness of 2 mm. Between the outer wall 220 and the inner wall 230 a hollow space with a hollow space width d of 50 mm is located. The faces of the outer wall 220 and the inner wall 230 facing towards the hollow space 240 are painted in a light colour (RAL7035 light grey) so as to reflect the impinging beam. Two sensors 221b, 221c protrude into the hollow space 240. The two sensors include sensor elements 221b-I, 221c-I arranged inside the hollow space 240 and evaluation elements 221b-II, 221c-II arranged outside the hollow space 240, where the evaluation elements 221b-II, 221c-II include electronic components for processing and forwarding the sensor signals provided by the sensor elements 221b-I, 221c-I.

[0073] If during the machining process the inner wall 230 is damaged and the laser beam 260 leaks through an opening 250 in the inner wall 230 into the hollow space 240, this laser beam 260 is deflected so that it strikes at least one of the sensor elements 221b-I, 221c-I on the inner surface of the outer wall 230 or on the inner surface of the inner wall 230. The corresponding evaluation element 221b-II, 221c-II recognizes the damage on the basis of a corresponding change in the sensor signal and switches off the laser machining unit with the laser machining head X.

[0074] FIG. 6 shows three laser protection hoods according to the invention with A, B and C, which differ in terms of their respective hood geometrical outlines. FIG. 6A shows a side view of a laser protection hood with an upper hood area 729 configured in a hemispherical shape, in which the laser light sensor 721 is arranged in the upper hood area. FIG. 6B shows a side view of a laser protection hood with a dome-shaped upper hood area 729, in which two laser light sensors 721 are arranged in the upper hood area 729 and two laser light sensors 721 are arranged in the remaining hood area. FIG. 6C shows a side view of a laser protection hood with an upper hood area 729 tapering upwards in a conical shape, in which two laser light sensors 721 are arranged in the upper hood area 729.

[0075] 7 shows a laser protection hood 710 according to the invention with a laser processing head X, which is arranged inside the laser protection hood 710. The laser processing head X has a central longitudinal axis 745 (working axis), which is rotatable such that the central longitudinal axis 745 forms a rotation angle α of up to 50° with the surface normal 746 of the mounting surface 703. Furthermore, FIG. 7 shows a laser beam 747 reflected by the workpiece 701, which is ideally flat.

[0076] The laser protection hood 710 has a lower edge 751 that extends at a distance from the rest surface 703. Between the lower edge 751 and the rest surface 703, a free space 752 with a width of 130 mm is left. A laser protection curtain 753 is attached to the laser protection hood 710, which is formed of flexible cover members that protrude into the free space 752. The laser protection curtain 753 is connected to a machine control (not shown). Damage to one of the cover members of the laser protection curtain causes a switch-off of the laser processing unit (not shown).

[0077] FIG. 8 shows a side view of a laser processing machine 600 including a work table 102, a laser processing unit (not shown in FIG. 8), a moving unit 601, and a laser protection hood 210.

[0078] The laser processing machine 600 is mounted on a stable flat bottom 117. The bottom 117 is provided with a running track 109, on which a moving unit 601 is supported on the side of the work table 102 via a support element 602, and on which the moving unit 601 can run. A loading surface for a workpiece is located on the work table 102 (not shown in FIG. 8). A support beam 108 extends above the work table, and thus transversely to the loading surface, and a moving element 125 is provided on the support beam 108, which allows the laser processing head and the laser protection hood 210 to move along the support beam 108 in a transverse direction to the work surface. Furthermore, the moving element 125 also allows the laser processing head and the laser protection hood 210 to move in a direction perpendicular to the work surface.

[0079] The laser protective hood 210 corresponds to the laser protective hood described in Fig. 2 to Fig. 5. The laser protective hood 210 has an outer wall 220, an inner wall, and a hollow space between the outer wall and the inner wall, and three laser light sensors 221a and 221b are arranged in this hollow space. The laser protective hood 210 is attached to the moving unit 601 so as to be tiltable to an assembly position relative to the moving unit 601.

Claims

1. An apparatus (100) for thermal processing of a workpiece (101a; 101b) by means of a laser beam (260), said apparatus (100) comprising a fiber laser generating a laser beam (260) with a wavelength in the range of 1020 nm to 1120 nm, a) The apparatus (100) includes a laser processing machine (600), and the laser processing machine (600) a resting surface (103a; 103b; 703) for said workpiece (101a; 101b; 701), a laser processing unit (104) equipped with a laser processing head (X); a moving unit (106; 601) including a lateral gantry (107) for moving the laser processing head (X) relative to the placement surface (103a; 103b; 703), the lateral gantry (107) having a support beam (108) extending above the placement surface (103a; 103b; 703), the support beam (108) being supported on the side of the placement surface (103a; 103b; 703) and capable of traveling on a traveling track (109; 109a; 109b); and b) the device (100) comprises a laser protective hood (110; 210; 710), the laser protective hood (110; 210; 710) surrounding the laser processing head (X), open towards the placement surface (103a; 103b; 703), movable together with the laser processing head (X) by the moving unit (106; 601), having an outer wall (220) and an inner wall (230), a hollow space (240) between the outer wall (220) and the inner wall (230), and at least one laser light sensor (221a; 221b; 221c; 721) arranged in the hollow space (240); c) the device (100) comprises a laser protection housing (115), which surrounds the placement surface (103a; 103b; 703), the laser processing unit (104), the moving unit (106; 601), and the laser protection hood (110) in a hood-like manner; Apparatus (100).

2. The laser processing machine (600) has a first placing surface (103a; 103b; 703) for a first workpiece (101a; 101b; 701) and a second placing surface (103a; 103b; 703) for a second workpiece (101a; 101b; 701), the laser protection housing (115) is movable so that the laser protection housing (115) surrounds either the first mounting surface (103a; 103b; 703) or the second mounting surface (103a; 103b; 703); The apparatus (100) of claim 1.

3. the laser protective hood (110; 210; 710) has an upper hood region (229; 729) configured in the shape of a dome, a cone, or a truncated pyramid, At least two of the laser light sensors (221a; 221b; 221c; 721) are arranged in the upper hood area (229; 729), The device (100) of claim 1 or 2.

4. the laser processing head (X) has a working axis (745) and is rotatable relative to the laser protective hood (110; 210; 710) such that the working axis (745) forms a rotation angle α of up to 50° with a surface normal (746) of the placement surface (103a; 103b; 703); the laser protection hood (110; 210; 710) is dimensioned so that the laser beam (747) reflected by the workpiece (101a; 101b; 701), which is ideally flat, impinges on the inner wall (230) of the laser protection hood (110; 210; 710) regardless of the rotation angle α; The device (100) of claim 1 or 2.

5. At least two laser light sensors (221a; 221b; 221c; 721), preferably at least three laser light sensors (221a; 221b; 221c; 721), particularly preferably at least four laser light sensors (221a; 221b; 221c; 721), are arranged in the hollow space (240); The device (100) of claim 1 or 2.

6. The hollow space (240) between the outer wall (220) and the inner wall (230) has a hollow space width d in the range of 35 mm to 50 mm. The device (100) of claim 1 or 2.

7. The laser protection hood (110; 210; 710) is positioned 0.5 mm above the mounting surface (103a; 103b; 703). ２ ~1.0m ２ Covering an area within the The device (100) of claim 1 or 2.

8. the laser protective hood (110; 210; 710) has a lower edge (751), the lower edge (751) extends at a distance from the mounting surface (103a; 103b; 703) while leaving a free space (752); a laser protection curtain (753) having a flexible cover member attached to the laser protection hood (110; 210; 710); the laser protection curtain (753) protrudes into the free space (752) between the laser protection hood (110; 210; 710) and the placement surface (103a; 103b; 703) and is designed so that damage to one of the cover members causes the laser beam to switch off the laser processing unit (104). The device (100) of claim 1 or 2.

9. the moving unit (106; 601) has a horizontal travel path defined such that a minimum distance of 1440 mm is left between the laser protection hood (110; 210; 710) and the laser protection housing (115); the moving unit (106; 601) has a vertical travel path designed to leave a minimum distance of 90 mm, preferably 100 mm, between the laser protection hood (110; 210; 710) and the placement surface (103a; 103b; 703), The device (100) of claim 1 or 2.

10. The fiber laser has a laser power of at least 10 kW, preferably at least 15 kW, particularly preferably at least 20 kW; The device (100) of claim 1 or 2.

11. A laser protection hood (110; 210; 710) for a laser processing head (X) of a laser processing machine (600), comprising: The laser processing machine (600) comprises a fiber laser that generates a laser beam (260) with a wavelength in the range of 1020 nm to 1120 nm, The laser protective hood (110; 210; 710) has an outer wall (220) and an inner wall (230), A hollow space (240) is provided between the outer wall (220) and the inner wall (230), and at least one laser light sensor (221a; 221b; 221c; 721) is arranged in the hollow space (240). Laser protection hood (110; 210; 710).

12. the laser protective hood (110; 210; 710) has an upper hood region (229; 729) configured in the shape of a dome, a cone, or a truncated pyramid, At least two of the laser light sensors (221a; 221b; 221c; 721) are arranged in the upper hood area (229; 729), A laser protective hood (110; 210; 710) according to claim 11.

13. At least two laser light sensors (221a; 221b; 221c; 721), preferably at least three laser light sensors (221a; 221b; 221c; 721), particularly preferably at least four laser light sensors (221a; 221b; 221c; 721), are arranged in the hollow space (240); A laser protective hood (110; 210; 710) according to claim 11 or 12.

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