Calibration system for an energy beam of an additive manufacturing device

Abstract

The invention relates to a calibration system (100, 100', 100'') for an energy beam (22) of an additive manufacturing device (1). The calibration system comprises an additive manufacturing device (1) with a beam inlet (25) for the energy beam (22), a gas supply (31) for providing a gas that is suitable for calibration, and a measuring unit (35) for detecting a beam property of the energy beam (22). In addition, the calibration system (100, 100', 100'') comprises a calibration aid (40, 60, 80) with a hollow space (54, 74, 94) and an inflow opening (41, 61, 81) for introducing the gas into the hollow space (54, 74, 94). The calibration aid (40, 60, 80) is arranged in the additive manufacturing device (1) and the energy beam (22) is surrounded by the hollow space (54, 74, 94) from the beam inlet (25) to the measuring unit (35). For calibration purposes, the gas flows into the hollow space (54, 74, 94). The invention further relates to a method for calibrating an energy beam (22) and to the use of a calibration aid (40, 60, 80) for calibrating an energy beam (22).

Description

[0001] CALIBRATION SYSTEM FOR AN ENERGY BEAM OF AN ADDITIVE MANUFACTURING DEVICE

[0002] The present invention relates to a calibration system and a method as well as a use of a calibration aid for calibrating an energy beam.

[0003] Additive manufacturing processes are becoming increasingly relevant in the production of prototypes and, now, also in series production. In general, "additive manufacturing processes" refers to manufacturing processes in which a finished product or component is built up by depositing material, usually based on digital 3D design data. The build-up is usually achieved by applying a build-up material layer by layer and selectively solidifying it. The term "3D printing" is often used as a synonym for additive manufacturing. The production of models, samples, and prototypes using additive manufacturing processes is often referred to as "rapid prototyping," the production of tools as "rapid tooling," and the manufacture of series products as "direct manufacturing."

[0004] The selective solidification of the build-up material often occurs by repeatedly applying thin layers of the build-up material, usually in powder form, one on top of the other and solidifying them by spatially limited irradiation with an energy beam, e.g., using light and / or heat and / or particle radiation, at the locations that are to become part of the finished product after production. An example of a process that uses irradiation is "laser powder bed fusion" or "selective laser melting." During the solidification process, the powder grains of the build-up material are partially or completely melted with the help of the energy locally introduced by the radiation at this location. After cooling, these powder grains are then bonded together to form a solid.

[0005] In such manufacturing, it is often necessary for a process gas to be passed through the process chamber for inerting, cooling, or exhaust purposes (particularly with a fan). This means that the additive manufacturing process takes place in a process gas atmosphere whose properties differ – possibly significantly – from the normal ambient atmosphere. For example, the process gas atmosphere may have a lower humidity content than the normal ambient atmosphere. Sometimes it is necessary to calibrate the energy beam in order to adjust its properties as optimally as possible for production. For this purpose, a measuring instrument is inserted into the beam path to record measured values ​​for specific beam properties of the energy beam.To ensure the same atmosphere as possible for calibration as in additive manufacturing, the entire process chamber is typically flooded with the process gas. This is particularly time-consuming if multiple calibration steps must be performed and / or the process chamber must first be returned to normal ambient atmosphere for safe opening.

[0006] It is an object of the present invention to simplify calibration of an energy beam of an additive manufacturing device.

[0007] This object is achieved by a calibration system according to patent claim 1, a method for calibrating an energy beam according to patent claim 13 and a use of a calibration aid for calibrating an energy beam according to patent claim 15.

[0008] The calibration system for an energy beam of an additive manufacturing device mentioned above comprises an additive manufacturing device with a beam inlet for the energy beam. It further comprises a gas supply for providing a gas suitable for calibration, a measuring unit for detecting a beam property of the energy beam, and a calibration aid with a cavity and an inlet for introducing the gas into the cavity. The calibration aid is arranged in the additive manufacturing device such that the energy beam is enclosed by the cavity from the beam inlet to the measuring unit, and the gas is flowed into the cavity for calibration.

[0009] The energy beam is basically any energy beam suitable for the selective melting or sintering of a corresponding material for additive manufacturing. For example, the energy beam is generated by a laser, preferably a CO laser. It can also be a CO2 laser, a diode laser, in particular a diode laser with a wavelength of 4-7 pm, an Nd:YAG laser, an electron beam, or the like. During operation, the energy beam enters the process chamber or the build space of the additive manufacturing device via at least one beam inlet. The beam inlet can be simply designed as an opening or breakthrough in the process chamber. In order to keep the volume of the areas to be filled with process gas small, the process chamber is preferably gas-tight from other areas of the additive manufacturing device, such as, for example,an optical chamber for the optical elements for adjusting the energy beam. The beam inlet is therefore designed, for example, as a coupling window that is transparent to the energy beam.

[0010] The gas suitable for calibration is selected depending on the energy beam, i.e., the type of energy beam. It has at least similar optical properties to the process gas. For a CO laser, dry air or nitrogen is preferably suitable as a gas for calibration. The gas is provided, for example, via a gas cylinder, via a separate in-house gas supply, or preferably via the gas supply of the additive manufacturing device.

[0011] The cavity of the calibration aid is enclosed by a hollow body. The hollow body can essentially be formed by corresponding elements of the calibration aid. Alternatively, the hollow body is formed by an interaction of elements of the calibration aid with elements of the additive manufacturing device, such as a wall of the process chamber and / or the coupling window or beam inlet. Thus, during normal operation, the energy beam is simultaneously enclosed from the beam inlet to the measuring unit or measuring instrument. This means that the beam path or beam path of the energy beam is largely enclosed within the process chamber by the beam inlet, the calibration aid, and the measuring instrument. It runs through the cavity of the calibration aid.Thus, the beam path in the calibration system is shielded from the ambient atmosphere, which may have properties that would hinder precise calibration. This improves calibration reproducibility.

[0012] For calibration, the gas is introduced or introduced through the inlet opening into the cavity of the calibration aid. For this purpose, the inlet opening is fluidically connected to the gas supply, e.g., via a hose or similar device.

[0013] The measuring unit is designed depending on the beam property of the energy beam to be recorded. For example, if the measuring unit measures or records the power of the energy beam as a beam property, the measuring unit is designed as a power meter. It is arranged adjacent to the calibration aid and preferably attached to it in such a way that the energy beam impinges on a measuring area of ​​the measuring unit.

[0014] The calibration aid is therefore preferably an additional unit that can be easily separated from the additive manufacturing device or removed from the process chamber and is introduced into the process chamber only for the calibration of the energy beam.

[0015] Accordingly, the method mentioned at the outset for calibrating an energy beam of an additive manufacturing device, which comprises a beam inlet, comprises at least the following steps: In one step, a calibration aid is provided which comprises a cavity and an inlet opening for introducing a gas suitable for calibration. In a further step, the calibration aid is introduced into the additive manufacturing device such that the energy beam is largely enclosed by the cavity from the beam inlet to a measuring unit. In a further step, the cavity of the calibration aid is flowed with the gas. Meanwhile, in a subsequent step, the calibration of the beam path is carried out. In this process, the measuring unit records a beam property of the energy beam.

[0016] The method thus essentially comprises the functionally designed features of the calibration system described above. After calibration, the calibration aid and the measuring unit are preferably removed from the process chamber in order to be able to carry out additive manufacturing processes using the additive manufacturing device.

[0017] As mentioned at the beginning, a calibration aid is used according to the invention for calibrating an energy beam of an additive manufacturing device. The calibration aid is introduced with its cavity into the additive manufacturing device, so that the energy beam is enclosed in the cavity from the beam inlet to a measuring unit. During calibration of the beam path, the cavity of the calibration aid is flushed with a gas suitable for calibration, and a beam property of the energy beam is recorded using the measuring unit.

[0018] Compared to flooding the entire process chamber, the inventive use of the calibration aid in the process chamber of an additive manufacturing device advantageously reduces the volume that must be flowed or flooded with the gas suitable for calibration of the energy beam. This significantly reduces the time required for calibration. This is especially the case when multiple calibration steps and thus multiple flooding steps are necessary after a new, adjusted setting of the energy beam.

[0019] Further, particularly advantageous embodiments and developments of the invention emerge from the dependent claims and the following description, wherein the independent claims of one claim category can also be developed analogously to the dependent claims and embodiments of another claim category and, in particular, individual features of different embodiments or variants can be combined to form new embodiments or variants.

[0020] The gas suitable for calibration is referred to below as "gas". The gas is preferably fed into the cavity in such a way that a relative humidity of below 5%, more preferably below 4%, and most preferably below 3%, is maintained in the cavity during calibration. As described above, the relative humidity is relevant, for example, for the beam properties of a CO laser or a diode laser with a wavelength of 4-7 pm. Since the relative humidity in an additive manufacturing process is similarly low to the preferred humidity values, it is advantageous to calibrate the energy beam under these conditions as well. The temperature of the gas during calibration is preferably at least 10°C and / or at most 50°C.

[0021] In contrast, in the remaining volume of the process chamber of the additive manufacturing device, a typical relative ambient humidity prevails during the flow of the cavity, which on average is preferably greater than 3%, more preferably greater than 5%, even more preferably greater than 10%, particularly preferably greater than 20%.

[0022] The cavity of the calibration system, i.e., the volume between the beam inlet, the calibration aid, and the measuring instrument, does not need to be gas-tight. It preferably has small gaps, e.g., at the connection points between the individual elements, through which the gas can escape. This advantageously displaces the gas composition of the ambient atmosphere from the cavity—particularly when the cavity is first flooded with gas. The gas is preferably provided via the gas supply of the additive manufacturing device. This is advantageous because the same gas is used as in the manufacturing process, thus essentially creating the same optical conditions as in the process gas atmosphere.

[0023] The gas is preferably introduced into the cavity via a separate connection or inlet in the process chamber. This means that an additional gas connection or gas inlet is preferably arranged in the process chamber for calibration. Therefore, the one or more existing gas inlets in the process chamber, which serve for relatively large-volume inerting and / or cleaning of the process chamber volume from impurities in the process gas, are preferably not used for calibration. The inlets for the manufacturing process therefore do not have to be adjusted. Furthermore, the separate connection for calibration can preferably be controlled or regulated independently of the other inlets. By controlling the volume flow of the gas for calibration in this way, the aforementioned relative humidity values ​​in the cavity can also be achieved, for example.

[0024] According to an alternative preferred embodiment, a number of existing gas inlets in the process chamber are used to provide the gas suitable for calibration. For this purpose, the gas is particularly preferably provided by means of an inflow device of the additive manufacturing device assigned to a number of beam inlets. During regular production operation, the inflow device or blow-off device is used for the directed flow of at least one beam inlet or laser window or coupling window. To carry out the calibration, the inflow device is activated and regulated or controlled separately, while other devices for the global flooding / flow of the process chamber with process gas / inert gas can be deactivated at the same time. To carry out the calibration, the inflow device therefore supplies the inflow opening of the calibration aid with the gas suitable for calibration.

[0025] For example, the cavity of the calibration aid can be docked to a process chamber-side opening (gas inlet) of the flow device in its intended position and, during calibration, direct the gas into the area between the beam inlet or coupling window and the measuring unit. Relative gas tightness can be achieved, for example, by designing the calibration aid in a manner that complements the geometry of the ceiling wall in some areas. This means that, due to its shape, the calibration aid connects essentially gas-tight to the wall or ceiling of the process chamber—e.g., through appropriate positioning and manufacturing precision and / or by means of additional seals.

[0026] The calibration aid preferably forms the cavity in a designated position in cooperation with a process chamber wall of the additive manufacturing device. The inlet opening of the calibration aid is particularly preferably located at a gas outlet opening of the inflow device and is fluidically connected thereto.

[0027] The cavity thus serves as a gas guide or as a gas channel and can be realized, for example, by recesses or a configuration of the calibration aid, which, in the intended position, includes surfaces that are partially spaced from the process chamber wall. When docked as intended to the inflow device and / or to a process chamber ceiling and / or wall, the calibration aid according to the invention can form the cavity, or thus a flow-through gap or channel, with the measuring unit. The cavity formed in this way can have an outflow opening, which, during intended operation, is the only opening of the calibration aid that allows the inflowing gas to escape into the interior of the process chamber.

[0028] An advantageous synergy effect arises with this design because such flow devices are generally arranged on a ceiling wall of the process chamber and near the existing number of beam inlets or coupling windows. Their use within the framework of the method or calibration system according to the invention therefore serves a further purpose outside the manufacturing process, so that any additional connections, valves, and / or line routing that might otherwise be required are advantageously eliminated.

[0029] The cavity preferably has a variable height. In other words, the distance between the beam inlet and the measuring unit is adjustable by means of the cavity, in particular by means of the elements that form the hollow body. This makes it possible, for example, to calibrate the beam properties of the energy beam at different height positions on the production level or in the construction field. Detailed embodiments are described below. In order to vary the height, the cavity is preferably designed to be expandable. For this purpose, the cavity, i.e. in particular the hollow body, can particularly preferably be made from an elastic material, in particular as a hose. Alternatively or additionally, it can particularly preferably be designed as a bellows or a similarly expandable element. At least the hollow body preferably has correspondingly expandable regions.This design allows the height position of the measuring unit to be varied, as well as the position within the production plane perpendicular to the height.

[0030] Furthermore, the cavity or hollow body can particularly preferably be designed as an elastic tent or as a tent in the form of a bellows. It can, for example, have a pyramidal or conical shape. Unlike a substantially linear or tubular design of the hollow body, a tent-like, pyramidal, or conical design allows calibration measurements to be performed across the entire construction area without repositioning the calibration aid.

[0031] To vary the height, the cavity or hollow body is preferably designed to be extendable, alternatively or additionally. This means that it has at least one extendable part or extension. It can also include rigid components. The extension can be a telescopic extension, for example.

[0032] The calibration aid preferably has a joint at at least one, particularly preferably at each, end of the hollow body. The joint can be, for example, a simple rotary joint or a combination of several joints. The joint can also be designed like a bellows, for example. However, the joint is most preferably designed as a ball joint. By means of the joint, in particular in combination with the variable height of the cavity or hollow body, the measuring unit can advantageously be positioned at any height setting of the production level at different positions, in particular at different positions required for calibration. The beam path remains enclosed by the hollow body or enclosed in its cavity, so that the energy beam passes through the gas suitable for calibration during calibration.

[0033] The calibration aid is preferably designed to be self-retaining. This means that it is preferably designed to maintain a height and / or joint position once set. The calibration aid is therefore particularly preferably designed to be self-retaining in such a way that it maintains a fixed position and / or dimension in the additive manufacturing device.

[0034] This is achieved, for example, by creating frictional resistance between the individual adjustable elements. This frictional resistance can be generated by a relatively small amount of play and / or appropriate surface properties, particularly by a suitable surface roughness, of the elements. The frictional resistance is preferably easy to overcome during manual adjustment, but is sufficient to ensure that the individual elements maintain their relative position or arrangement without external influence.

[0035] The calibration system preferably has fastening means for attaching the calibration aid to the additive manufacturing device. The fastening means are arranged, for example, on the calibration aid or the additive manufacturing device. They are preferably designed as complementary elements forming a positive and / or frictional connection. The calibration aid can be implemented, for example, using clamping screws or a clip closure, in particular using manually releasable, positive locking lugs, other positive locking elements, and / or the like. The calibration aid is preferably fastened in the area of ​​the beam entry into the process chamber or the coupling window for the energy beam.

[0036] The calibration aid preferably extends in the additive manufacturing device over a partial or complete distance between a production plane or the build area and a beam inlet of the additive manufacturing device. This means that the calibration aid is attached, for example, to the coupling window, as described above. However, from there, it does not extend completely to the production plane, but rather holds the measuring unit – virtually floating – in a position between the production plane and the beam inlet.

[0037] The hollow body of the calibration aid preferably completely encloses the energy beam from the moment the energy beam passes through the beam inlet or the coupling window until it strikes the measuring unit. The volume enclosed by the hollow body, i.e. the cavity, is preferably smaller than the volume of the process chamber, in particular smaller than a third, more preferably smaller than a quarter, even more preferably smaller than a tenth, particularly preferably smaller than a fiftieth, and most particularly preferably smaller than a hundredth of the volume of the process chamber. This ratio and the resulting savings effect continually improve with increasing installation space size. Accordingly, the time required for flooding the volume for calibration is also advantageously reduced.

[0038] The calibration aid and / or the measuring unit are preferably removable from the process chamber and are removed from the process chamber before an additive manufacturing process. This means that before commissioning the additive manufacturing device or after a previous additive manufacturing process, a calibration method according to the invention is preferably carried out. Following this, the calibration aid and / or the measuring unit are preferably removed from the process chamber, and a new, subsequent additive manufacturing process is then carried out.

[0039] This means that an additive manufacturing process preferably does not take place during calibration. Accordingly, the flow to the process chamber, which can be provided, for example, by a circulation system for supplying and recirculating process gas, possibly with filtering of contaminated process gas, is particularly preferably deactivated during calibration with the calibration system according to the invention. This advantageously saves process gas or the energy required to circulate the process gas.

[0040] The property of the energy beam measured for calibration preferably includes a beam power, an intensity distribution, a focus position, a focus geometry, and / or a response behavior of the energy beam. Alternatively or additionally, properties of an energy beam deflection device (e.g., a galvanometer scanner) can also be measured, e.g., the relative positioning accuracy of one or more deflection devices.

[0041] To determine the laser power, a typical power meter is used, for example, as described above. The laser power is preferably measured outside the focus rather than at the focal point, since the intensity at the focus may be too high in some places. If the focal point is, for example, on the production plane, the power meter is simply placed on the production plane or a build platform. The offset to the focal point created in this way is sufficient for the power measurement, because in this way the power meter can still record the entire power without the intensity being too high at any one point. The focus position indicates the position of the focus in three-dimensional space in relation to the additive manufacturing device, i.e. in particular a height above the production plane or a distance to the beam entrance as well as a two-dimensional position in a plane parallel to the production plane.The focus geometry indicates whether the focus is circular, elliptical, particularly with information about the principal axes, or other shapes. The focus position and focus geometry can be determined, for example, using a focus monitor as a measurement unit. This can be easily implemented using a power meter with a pinhole (a point-shaped aperture) in front of it.

[0042] The response behavior of the energy beam describes a reaction delay or power curve when switching on, off, or when the power requirement changes. Thermal paper, for example, can serve as a measurement unit for the response behavior. After calibration measurements, the corresponding response characteristics can be determined on this paper.

[0043] The invention is explained in more detail below with reference to the accompanying figures using exemplary embodiments. In the various figures, identical components are provided with identical reference numerals. The figures are generally not to scale. They show:

[0044] Figure 1 is a schematic, partially sectioned view of an additive manufacturing device for additively producing a three-dimensional object,

[0045] Figure 2 is a schematic, partially sectioned view of an embodiment of a calibration system according to the invention for an energy beam of an additive manufacturing device,

[0046] Figure 3 is a schematic, sectional detailed view of another embodiment of a calibration system according to the invention,

[0047] Figure 4 is a schematic, sectional detailed view of the calibration system from Figure 2, Figure 5 is a schematic perspective detailed view of a further embodiment of a calibration system according to the invention,

[0048] Figure 6 is a sectional view of the calibration system of Figure 5,

[0049] Figure 7 is a perspective detailed view of the calibration aid from Figure 5 with a measuring unit and

[0050] Figure 8 is a flow diagram shown in block diagram form of an embodiment of a method according to the invention for calibrating an energy beam of an additive manufacturing device.

[0051] The following describes an additive manufacturing device 1 for a three-dimensional object with reference to Fig. 1. The manufacturing device 1 shown schematically and partially in section in Fig. 1 is a selective laser melting device 1. For building an object 2, it contains a process chamber 3 with a chamber wall 4.

[0052] Arranged in the process chamber 3 is a container 5 open at the top and having a container wall 6. The upper opening of the container 5 defines a production level 7, with the area of ​​the production level 7 located within the opening, which can be used to construct the object 2, being referred to as the construction field 8. Furthermore, the process chamber 3 comprises a process gas supply 31 assigned to the process chamber 3, as well as a process gas outlet 32.

[0053] Arranged in the container 5 is a carrier 10 which is movable in a vertical direction V and to which a base plate 11 is attached, which closes off the container 5 at the bottom and thus forms its base. The base plate 11 can be a plate formed separately from the carrier 10 and fastened to the carrier 10, or it can be formed integrally with the carrier 10. Depending on the powder used and the process, a build platform 12 can be attached to the base plate 11 as a build base, on which the object 2 is built. However, the object 2 can also be built on the base plate 11 itself, which then serves as a build base. In Fig. 1, the object 2 to be formed in the container 5 on the build platform 12 is shown below the working plane 7 in an intermediate state with several solidified layers, surrounded by unsolidified build material 13.The laser melting device 1 further contains a storage container 14 for a powdered building material 15 that can be solidified by electromagnetic radiation and a coater 16 that can be moved in a horizontal direction H for applying the stored building material 15 within the construction field 8. The coater 16 preferably extends transversely to its direction of movement over the entire area to be coated.

[0054] The laser melting device 1 further comprises an exposure device 20 with a laser 21, preferably a CO laser, which generates a laser beam 22, which is deflected via a deflection device 23 and focused onto the working plane 7 by a focusing device 24 via a beam inlet 25 or a coupling window 25, which is attached to the top of the process chamber 3 in the chamber wall 4.

[0055] The laser melting device 1 further includes a control unit 29, via which the individual components of the laser melting device 1 are controlled in a coordinated manner to carry out the construction process. Alternatively, the control unit 29 can also be mounted partially or entirely outside the laser melting device 1. The control unit can contain a CPU whose operation is controlled by a computer program (software). The computer program can be stored separately from the laser melting device 1 on a storage medium, from which it can be loaded into the laser melting device 1, in particular into the control unit 29.

[0056] As the building material 15, a powdery material is preferably used, which can be, for example, a metal-containing or metal-based building material, but is preferably a polymer-containing, particularly preferably a polymer-based (> 50 wt.% polymer content) building material.

[0057] During operation, to apply a powder layer, the carrier 10 is first lowered by a height corresponding to the desired layer thickness. The coater 16 first moves to the storage container 14 and takes from it a quantity of the building material 15 sufficient to apply one layer. It then moves over the build area 8, where it applies powdered building material 15 to the build base 12 or a previously existing powder layer, and spreads it out into a powder layer. The application takes place at least over the entire cross-section of the object 2 to be manufactured, preferably over the entire build area 8, i.e. the area delimited by the container wall 6. Optionally, the powdered building material 15 is heated to a working temperature by means of a radiant heater.

[0058] The cross-section of the object 2 to be manufactured is then scanned by the laser beam 22, so that the powdered building material 15 is solidified at the locations corresponding to the cross-section of the object 2 to be manufactured. The energy introduced by the radiation partially or completely melts the powder grains at these locations, so that after cooling, they are bonded together as a solid. These steps are repeated until the object 2 is finished and can be removed from the process chamber 3.

[0059] Figure 2 shows a schematic, partially sectioned view of an embodiment of a calibration system 100 according to the invention for an energy beam 22, in particular the beam of a CO laser, of an additive manufacturing device 1. The additive manufacturing device 1 corresponds to the additive manufacturing device 1 from Fig. 1. However, to better illustrate the calibration system 100, some elements of the additive manufacturing device 1 are not shown here. The carrier 10 and the base plate 11 are arranged here in a starting position adjacent to the production level 7 and the build area 8, respectively.

[0060] In addition to the additive manufacturing device 1, the calibration system 100 comprises a calibration aid 60 and a measuring unit 35. The measuring unit 35 is designed here as a power meter 35 for measuring the laser power as a beam property and is positioned in the beam path of the laser beam 22 on the production level 7.

[0061] The beam path of the laser 22 within the process chamber 3 is enclosed by the calibration aid 60 from the coupling window 25 to the power meter 35. The calibration aid 60 has an inlet opening 61, which in this exemplary simple design is fluidically connected to the process gas supply 31 by means of a hose 26 and a plug 27. During calibration, the interior or cavity 74 (see Fig. 4) of the calibration aid 60 is supplied with process gas, in particular nitrogen, as illustrated by the arrows. The process gas penetrates through small gaps between the elements of the calibration aid 60 and displaces the gas composition of the surrounding atmosphere from the calibration aid 60. Since the process gas is identical for the manufacturing process and the calibration process, it is a suitable gas for calibration because it has the same optical properties.For example, the inflowing gas achieves a relative humidity of less than 3% in the cavity of the calibration aid, whereby the humidity has an influence on the calibration and the beam properties, especially in the case of CO lasers.

[0062] The calibration aid 60 is described in detail with reference to Fig. 4.

[0063] Figure 3 shows a schematic and sectional view of a detailed view of another embodiment of a calibration system 100' according to the invention. For better illustration, only the manufacturing plane 7 and the top side of the chamber wall 4 with the coupling window 25 of the additive manufacturing device 1 are shown here, which separates the irradiation device 20 or the optics chamber in a gas-tight manner from the process chamber 3 by means of a circumferential seal 34 (see also Fig. 1).

[0064] The calibration aid 40 comprises an upper part 42 and a lower part 43. The upper part 42 and the lower part 43 are essentially cylindrical in shape and arranged concentrically, so that together they form a hollow body with a cavity 54. An outer dimension of the lower part 43 is dimensioned in relation to an inner dimension of the upper part 42 such that they can be moved telescopically against each other. As a result, the height of the calibration aid, i.e. the distance from the free end of the upper part 42 to the free end of the lower part 43, can be varied or adjusted. The upper part 42 and the lower part 43 are preferably dimensioned such that they form a frictional connection without manual force, which automatically holds the lower part 42 and other components attached to it.

[0065] An upper receptacle 44 is formed at the free end of the upper part 42. The upper side of the chamber wall 4 has a ledge 33 in the area around the coupling window 25. The ledge 33 is enclosed by the upper receptacle 44 of the calibration aid 40 with essentially a precise fit, i.e. with only a small gap. The ledge 33 and the upper receptacle 44 thus have complementary shapes. For example, they can be arranged concentrically, circularly, or squarely around the coupling window 25. The upper receptacle 44 is preferably manufactured with such a precise fit that a frictional connection with the ledge 33 is created. This creates a simple plug-in connection. Alternatively, the upper receptacle 44 can also be connected to the ledge 33 in a force-fitting and / or form-fitting manner using fastening means such as clamping screws and / or a clip closure. The upper part 42 also has an inflow opening 41, which can be used, for example,can be fluidically connected to the gas supply, in particular the process gas supply 31, by means of a hose 26 (see Fig. 2). The inlet opening 41 is preferably arranged closer to or adjacent to the free end of the upper part 42.

[0066] A lower receptacle 45 is formed at the free end of the lower part 42. The lower receptacle 45 is manufactured to fit precisely with a holder 46 for the measuring unit 35 and encloses the opening facing the coupling window 25. Here, too, "precise fit" preferably means that a frictional connection is created between the lower receptacle 45 and the holder 46, forming a simple plug-in connection. Alternatively, the fastening means specified above can also be used here.

[0067] The calibration aid 40 is therefore preferably designed such that it automatically maintains a height once set and thus holds the measuring unit 35 in its holder 46 even when hanging from the ledge 33. Only small gaps occur between the elements of the calibration aid 40 and the connection points with the ledge 33 and the holder 46, through which only a small amount of the gas suitable for calibration and introduced through the inlet opening 41 can escape. Thus, after an initial flooding, the cavity 54 is filled with the gas suitable for calibration and is easily flowed through by it, so that gases from the surrounding atmosphere do not penetrate into the calibration aid 40. The entire beam path of the laser beam 22 running through the process chamber 3 is therefore enclosed by the calibration aid 40 and runs from the coupling window 25 through the gas suitable for calibration until it reaches a measuring window 36 orMeasuring area 36 of the measuring unit 35. As a result, the laser beam 22 can be calibrated under essentially the same conditions, ie with the same optical properties, under which a subsequent additive manufacturing process is carried out.

[0068] After calibration, the plug connections of the calibration aid 40 (and their fastening means, if applicable) to the ledge 33 and to the holder 46 can be loosened and the calibration aid 40 removed from the process chamber 3. To facilitate removal, the calibration aid 40 can be pushed together, for example, using the telescopic height adjustment between its upper part 42 and its lower part 43. Figure 4 shows a detailed schematic sectional view of the calibration system from Fig. 2. The calibration aid 60 shown here is similar to the calibration aid 40 from Fig. 3. In contrast, the calibration aid 60 has two ball joints 68, 69, 70, 71, 72, 73.

[0069] An upper ball joint 68, 69, 70 is formed between the upper receptacle 64 and the upper part 62. It comprises a central calotte 68, an outer calotte 69 and an inner calotte 70, which are arranged concentrically. The calottes 68, 69, 70 are shaped as a spherical calotte or as a layer of a spherical calotte and have radii that increase from the inside to the outside. The outer calotte 69 and the inner calotte 70 are formed on the upper receptacle 64. The central calotte 68 is formed on the upper part 62. Compared to the outer calotte 69 and the inner calotte 70, it is shaped as a spherical layer that is closer to the pole of the ball and thus partially engages between the outer calotte 69 and the inner calotte 70. The upper part 62 is thus mounted so as to be movable or rotatable relative to the upper receptacle 64 around the common center of the domes 68, 69, 70.The production of such a pivot bearing 68, 69, 70 composed of interlocking calottes 68, 69, 70 is possible, for example, by means of additive manufacturing.

[0070] Between the lower receptacle 65 and the lower part 63, a lower ball joint 71, 72, 73 is formed in the same way as the upper ball joint 68, 69, 70. Here, too, a central cap 71 arranged on the lower part 63 engages between an inner cap 73 and an outer cap 72, both of which are formed on the lower receptacle 65. The two ball joints 68, 69, 70, 71, 72, 73 are preferably designed to be self-retaining, like the telescopic connection between the upper part 62 and the lower part 63, due to the frictional resistance existing between them.

[0071] By means of the ball joints 68, 69, 70, 71, 72, 73, the measuring unit 35 can be positioned at an offset D to a position on a central vertical axis A of the coupling window 25. This makes it possible to calibrate the beam properties of laser beams 22 that are inclined at an angle a to the central vertical axis A.

[0072] In Figures 5 and 6, a further embodiment of a calibration system 100" according to the invention is shown schematically in a perspective view. Fig. 6 shows a sectional view along the sectional plane S marked in Fig. 5. For better illustration, only the top side of the chamber wall 4 is shown in detail here.

[0073] A coupling window 25 is arranged in a recess in the upper side of the chamber wall 4. A laser beam 22 passes through the coupling window 25 onto a measuring area 36 of a measuring unit 35, which is arranged within the process chamber 3 (see Fig. 1). The measuring unit 35 also has a fan 37 with cooling fins to dissipate any heat that may be generated.

[0074] The measuring unit 35 is fastened adjacent to the coupling window 25 by means of the calibration aid 80. For precise positioning and fastening, the calibration aid 80 has two pins 84 (see Figs. 6 and 7) which engage positively with complementary elements (not shown) that are rigidly connected to the chamber wall 4. By means of the pins 84 and the complementary elements, the calibration aid 80 and thus also the measuring unit 35 are guided exactly into the position required for the measurement. For fastening, metal sheets 26 are also arranged parallel to the section plane S on both sides next to the coupling window 25. The metal sheets 26 are each encompassed by a fastening clamp 82 of the calibration aid 80. The calibration aid 80 is fastened to the metal sheets 26 in a force-fitting manner by means of the fastening clamps 82 and a knurled screw 83 each.

[0075] Between the coupling window 25 and the measuring area 36 of the measuring unit 35, a cavity 94 is arranged, which is enclosed by the hollow body of the calibration aid 80. Compared to the exemplary embodiments of Figs. 3 and 4, the cavity 94 is designed to be flat, resulting in a substantially laminar flow of the gas suitable for calibration. This is illustrated in Fig. 7, which schematically shows a perspective view of the calibration aid 80 from Figs. 5 and 6 with the measuring unit 35, but without the chamber wall 4.

[0076] For introducing the gas into the cavity 94, the calibration aid 80 has an inlet opening 81. The inlet opening 81 is preferably fluidically connected directly to a gas supply (not shown). The gas supply here is preferably not the process gas supply intended for the actual circulation of the process gas. The gas supply used here is preferably designed separately from the process gas supply and is preferably regulated separately. The laser beam 22 thus runs between the coupling window 25 and the measuring area 36 of the measuring unit 35 in the cavity 94, which is enclosed by the calibration aid 80 and through which the gas suitable for calibration flows during calibration. As a result, the laser beam 22 is protected from gases from the ambient atmosphere that could have a negative influence on the calibration.

[0077] While the calibration aids 40, 60 of Fig. 3 and Fig. 4 are particularly suitable for performing a calibration based on beam properties that are recorded in the region of the production level 7, the calibration aid 80 shown in Figs. 5 to 7 has an advantageously small volume to be flooded and is used for calibration measurements that can be performed in the region of the coupling window 25, such as a measurement of the total power of the laser beam 22.

[0078] Figure 8 shows a flow diagram in block diagram form of an embodiment of a method according to the invention for calibrating an energy beam 22 of an additive manufacturing device 1.

[0079] In a first step I, a number of additive manufacturing processes are carried out using the additive manufacturing device 1. After a predetermined number of manufacturing cycles, a predetermined operating time, or as needed, calibration of the energy beam 22 is required.

[0080] For this purpose, in a second step II, a calibration aid 40, 60, 80 is provided, which has a hollow body 54, 74, 94 with an inflow opening 41, 61, 81.

[0081] In a third step III, the calibration aid 40, 60, 80 is introduced into a process chamber 3 of the additive manufacturing device 1 so that it encloses the energy beam from a coupling window 25 or a beam inlet 25 to a measuring unit 35 for the subsequent calibration.

[0082] The inlet opening 41, 61, 81 is fluidically connected to a gas supply so that the hollow body 54, 74, 94 is flowed through with a gas suitable for calibration in a fourth step IV.

[0083] In a fifth step V, calibration is carried out under this gas atmosphere.

[0084] For this purpose, a beam property, such as the power of the energy beam 22, is measured using the measuring unit 35, such as a power meter. Depending on the measured values, adjustments are made to the optics 22, 23 or to the generation 21 of the energy beam 22 until the desired beam property is achieved.

[0085] In a sixth step VI, after calibration, the calibration aid 40 and the measuring unit 35 are removed from the process chamber 3.

[0086] In a seventh step VII, a number of manufacturing processes can be carried out with the calibrated energy beam 22 until recalibration is required and steps II to VI are repeated.

[0087] Finally, it should be noted once again that the figures described in detail above are merely exemplary embodiments which can be modified in a variety of ways by a person skilled in the art without departing from the scope of the invention. Although only a CO laser as the energy beam and nitrogen as the gas suitable for calibration were described above, other types of lasers and correspondingly suitable gases or gas mixtures are also encompassed by the scope of the present invention. The calibration aid can also have other designs, such as a bellows shape or the like. Furthermore, the use of the indefinite articles "a" or "an" does not exclude the possibility that the features in question can be present multiple times.Likewise, the terms “unit”, “device” or “system” do not exclude the possibility that these consist of several interacting sub-components, which may also be spatially distributed.

[0088] List of reference symbols

[0089] 1 additive manufacturing device / laser melting device

[0090] 2 Object / Component

[0091] 3 Process Chamber

[0092] 4 chamber wall

[0093] 5 containers

[0094] 6 Container wall

[0095] 7 Production Level

[0096] 8 Construction site

[0097] 10 carriers

[0098] 11 Base plate

[0099] 12 Construction platform

[0100] 13 unconsolidated building material

[0101] 14 storage containers

[0102] 15 Construction material

[0103] 16 coaters

[0104] 17 Radiant heating

[0105] 20 Irradiation device / exposure device

[0106] 21 lasers

[0107] 22 Laser beam, beam path

[0108] 23 Deflection device / scanner

[0109] 24 Focusing device

[0110] 25 Coupling window / beam entry

[0111] 26 sheet metal

[0112] 28 hose

[0113] 27 plugs

[0114] 29 Control unit

[0115] 31 Process gas supply

[0116] 32 Process gas outlet

[0117] 33 Sims

[0118] 34 Seal

[0119] 35 measuring unit

[0120] 36 measuring range / measuring window

[0121] 37 fans

[0122] 40, 60, 80 Calibration aid 41, 61 , 81 Inlet opening

[0123] 42, 62 top

[0124] 43, 63 lower part

[0125] 44, 64 upper shot

[0126] 45 lower mount

[0127] 46 Bracket

[0128] 54, 74, 94 cavity / hollow body

[0129] 68, 71 middle dome

[0130] 69, 72 outer calotte

[0131] 70, 73 inner calotte

[0132] 68, 69, 70 upper ball joint

[0133] 71, 72, 73 lower ball joint

[0134] 82 Mounting clamp

[0135] 83 Knurled screw

[0136] 84 cones

[0137] 100, 100', 100" calibration system

[0138] A axis a angle

[0139] D Offset

[0140] V vertical direction

[0141] Section plane S

[0142] I, II, VII procedural steps

Claims

AMENDED CLAIMS received by the International Bureau on 20 October 2023 (20.10.2023) 1. Calibration system (100, 100', 100") for an energy beam (22) of an additive manufacturing device (1), comprising - an additive manufacturing device (1) with a beam inlet (25) for the energy beam (22), - a gas supply (31) to provide a gas suitable for calibration, - a measuring unit (35) for detecting a radiation property of the energy beam (22) and - a calibration aid (40, 60, 80) with a cavity (54, 74, 94) and an inlet opening (41, 61, 81) for introducing the gas into the cavity (54, 74, 94), wherein - the calibration aid (40, 60, 80) is arranged in the additive manufacturing device (1) and is an additional unit that can be removed from a process chamber (3), - the energy beam (22) from the beam entry (25) to the measuring unit (35) is enclosed in the cavity (54, 74, 94) and - the gas for calibration is introduced into the cavity (54, 74, 94).

2. Calibration system according to claim 1, wherein the gas is directed into the cavity (54, 74, 94) in such a way that during calibration a relative humidity is maintained in the cavity (54, 74, 94) below 5%, preferably below 4%, particularly preferably below 3%.

3. Calibration system according to one of the preceding claims, wherein the gas is provided by means of the gas supply (31) of the additive manufacturing device (1).

4. Calibration system according to one of the preceding claims, wherein the cavity (54, 74, 94) has a variable height.

5. Calibration system according to one of the preceding claims, wherein the cavity (54, 74) is extendable to vary the height.

6. Calibration system according to claim 5, wherein the calibration aid (60) has a joint (68, 69, 70, 71, 72, 73) at at least one, preferably at each, end of the cavity (74), which is preferably designed as a ball joint (68, 69, 70, 71, 72, 73). AMENDED SHEET (ARTICLE 19) 7. Calibration system according to one of the preceding claims, wherein the gas is provided to the additive manufacturing device (1) by means of a flow device associated with a number of jet inlets (25).

8. Calibration system according to one of the preceding claims, wherein the calibration aid (80) in a position intended, in conjunction with a process chamber wall of the additive manufacturing device (1), forms the cavity (94), wherein the inlet opening (81) of the calibration aid (80) preferably abuts a gas outlet opening of the inlet device.

9. Calibration system according to one of the preceding claims, wherein the calibration aid (40, 60, 80) is self-retaining.

10. Calibration system according to one of the preceding claims, wherein the calibration aid (40, 60, 80) is designed to be self-retaining in such a way that it remains positionally fixed and / or dimensionally fixed in the additive manufacturing device (1).

11. Calibration system according to one of the preceding claims, comprising fastening means (82, 83, 84) for attaching the calibration aid (80) to the additive manufacturing device (1).

12. Calibration system according to one of the preceding claims, wherein the calibration aid (40, 60, 80) extends in the additive manufacturing device (1) over a partial or complete distance between a manufacturing plane (7) and a beam entry (25) of the additive manufacturing device (1).

13. Method for calibrating an energy beam (22) of an additive manufacturing device (1) comprising a beam inlet (25), comprising at least the following steps: - Providing a calibration aid (40, 60, 80) comprising a cavity (54, 74, 94) and an inlet opening (41, 61, 81) for introducing a gas suitable for calibration, - Inserting the calibration aid (40, 60, 80) into the additive manufacturing device (1) so that the energy beam (22) from the beam inlet (25) to a measuring unit (35) is enclosed by the cavity (54, 74, 94), - Flow of gas into the cavity (54, 74, 94) of the calibration aid (40, 60, 80) and AMENDED SHEET (ARTICLE 19) - Performing the calibration of the energy beam (22), wherein the measuring unit (35) detects a beam property of the energy beam (35).

14. Method according to claim 13, wherein for calibration a beam power, an intensity distribution, a focus position, a focus geometry and / or a response behavior of the energy beam is recorded as a beam property of the energy beam (22).

15. Use of a calibration aid (40, 60, 80) for calibrating an energy beam (22) of an additive manufacturing device (1), wherein - the calibration aid (40, 60, 80) with its cavity (54, 74, 94) is inserted into the additive manufacturing device (1) so that the energy beam (22) from the beam inlet (25) to a measuring unit (35) is enclosed by the cavity (54, 74, 94), - the cavity (54, 74, 94) of the calibration aid (40, 60, 80) is supplied with a gas suitable for calibration and - the calibration of the energy beam (22) is carried out, wherein the measuring unit (35) detects a beam property of the energy beam (22). AMENDED SHEET (ARTICLE 19)

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