COMPONENT PRESSING METHODS AND DEVICES FOR THIS

Description

[0001] The present invention relates to the printing of components.

[0002] The so-called 3D printing of components is well known. In such processes, a component to be manufactured is gradually built up by irradiating materials to cause them to adhere to one another in such a way that the desired component is formed. This adhesion can occur, for example, by triggering a local chemical addition reaction or, for example, by melting and / or sintering powders using sufficiently high-energy radiation. These manufacturing processes are therefore also referred to as additive manufacturing processes.

[0003] One problem with additive manufacturing processes such as laser melting is that production is expensive due to the slow production speeds with conventional machines. Production speed cannot be increased simply by continually increasing the melting speed with higher laser beam power, because this would exacerbate the problems associated with heating and cooling the material—also due to the resulting temperature gradients.

[0004] Various beam cross-sections have already been proposed to improve production. For example, in addition to a beam cross-section with a Gaussian profile, beams with a so-called top-hat profile are used, or several beams are combined with a greater or lesser overlap to form lines or matrices. Furthermore, the use of beam profiles in which the material to be melted is preheated in a region of lower beam intensity is proposed (see, for example, EP 2 335 848 B1).

[0005] An arrangement according to EP 2 909 007 B1 is intended to form a continuous melt pool by forming a laser line with a coherent intensity distribution from individual beams. A coherent intensity distribution is understood to mean that the intensity within the illuminated area does not fall below 10% of the maximum intensity in this area. A movement device preferably has one or two translation axes, which can be perpendicular to one another. It is stated that by arranging individual laser spots, their diameters and by modulating the power, the effective power density distribution is changed spatially and temporally in such a way that the dimensions of the resulting melt pool are adapted to the component geometry to be produced by the temperature field established in the material.This will make it possible to adjust the dimensions of the melt pool in terms of length, width and depth independently of one another and to change them dynamically during processing.

[0006] From the publication "Laser powder-bed fusion additive manufacturing: Physics of complex melt flow and formation mechanisms of pores, spatter, and denudation zones" by Saad A. Khairallah, Andrew T. Anderson, Alexander Rubenchik, and Wayne E. King in Acta Materialia 108(2016) 36-45, it is known that the creation of deep depressions during the melting process should be avoided to prevent pore formation. When changing direction along a scan path, the laser intensity should be reduced, as additional heat could lead to deep and narrow recesses that collapse and form pores. Conversely, a suitable scan vector overlap should increase densification by eliminating partially melted and trapped parts and associated shallow lateral pores. The authors suggest a smooth reduction of the laser power at the end of the scan path to improve surface quality.

[0007] EP 3 017 895 A1 discloses a method for manufacturing a component by selective laser melting. A laser field is generated with, for example, up to 20 simultaneously used lasers, which can be selectively switched on or off to irradiate or not irradiate specific areas. This is intended to melt powdered material selectively to create contours. It is obvious that switching off the lasers necessarily reduces the irradiated power compared to the maximum power that can be generated by all the lasers together. Where effects from particularly high power levels must be considered for particularly fast processing in product manufacturing, the changing power levels actually make processing more difficult.

[0008] DE 10 2011 079 521 A1 discloses a method in which a laser beam is shaped using a beam-shaping system for the layer-by-layer production of three-dimensional objects. The maximum power density at the focus should not be set greater than 50% above the average power density at the focus. This is said to be advantageous when using the arrangement with plastic particles.

[0009] WO 2012 / 136615 A1 discloses a laser melting system that uses an intensity profile that is improved compared to a Gaussian beam. It is stated that the melting of edge particles with known beam profiles creates problems at the edge due to the drop in intensity, making the process difficult to control and posing a high risk of a reduction in the surface quality of the component. Therefore, the goal is to achieve a uniform intensity profile over a defined area, which, in particular, should be nearly rectangular.

[0010] WO 2017 / 190863 A1 discloses a method to simplify the calibration of an irradiation system.

[0011] An "OPTICAL SYSTEM FOR VARIABLE BEAM SHAPING" is known from an annual report of the FhG ILT, where the intensity profile, as an important process parameter, is said to significantly influence the processing results of laser-assisted machining processes. The often Gaussian intensity profile emitted by a laser beam source is transformed into process-adapted intensity profiles in many applications using optical beam-shaping elements. However, the resulting intensity profiles are static, and dynamic adaptation to the process is not possible. Therefore, an optical system is described that optionally provides a rotationally symmetric, Gaussian or a homogeneous, linear spot in the processing plane.It is stated that an optical system consisting of cylindrical lenses can be provided to form a Gaussian input beam into a homogeneous, line-shaped spot in the processing plane and that in a process for which a patent has been applied for by the Fraunhofer ILT, the system is adapted so that the degree of homogenization can be varied.

[0012] The optical system is said to be capable of generating not only a rotationally symmetric intensity distribution with a Gaussian profile, but also a linear intensity distribution with an aspect ratio of 30:1. This linear intensity distribution is said to exhibit high homogeneity along the longitudinal axis. The working distance is said to remain constant during switching between the intensity profiles. The system reportedly requires less than 0.2 seconds to switch to another intensity profile. Furthermore, the cylindrical lenses made of quartz glass reportedly allow the use of laser powers up to 2 kW.

[0013] It is stated that, in principle, all laser material processing processes in which the intensity profile is homogenized in the processing plane benefit from variable beam shaping. The gained degree of freedom should also allow Gaussian profiles to be used, resulting in positive effects on processing time and quality.

[0014] DE 10 2015 202 347 A1 discloses a 3D component printing method in which a body is constructed from a starting material that is irradiated with a beam in tracks, as well as a 3D-printed component produced by this method. The beam has an effective surface profile that is not rotationally symmetrical, with the effective surface profile of the beam being aligned according to the track direction. The disclosure further relates to a beam-aligning assembly for a 3D printing machine and a 3D printing machine with such a beam-aligning assembly.

[0015] From US 2018 / 193955 A1 an additive manufacturing system for producing a component using a laser array with a non-uniform energy intensity profile is known,

[0016] From JP 2004 314406 A a method and a system for optical microforming with variable layer thickness is known, in which the aperture of a lens is enlarged or reduced depending on the layer thickness in order to change the light intensity.

[0017] From KR 101 740 266 B1, a device for three-dimensional structural processing with improved speed while maintaining dimensional accuracy and bond strength of layers is known, in which the diameter of a laser beam focus is adjusted.

[0018] The object of the present invention is to enable cost-effective production of high-quality components.

[0019] The solution to this problem is claimed independently. Preferred embodiments can be found in the subclaims.

[0020] According to a first basic idea of ​​the invention, a 3D component printing method is proposed in which a body is built up from starting material that is irradiated track by track with a beam having an effective surface profile that is not rotationally symmetrical. The effective surface profile of the beam is aligned according to and / or following the track direction. The effective surface profile can be the area in which a build-up, melting, curing and / or heating of starting material takes place. For example, the effective surface profile can be the area in which a powdered starting material is heated and / or melted in order to achieve a corresponding deposition along the track after its resolidification (so-called hatches).

[0021] Different types of radiation can be used to modify the starting material so that the body is constructed. For polymerizable liquids, irradiation with UV light or similar is particularly suitable, as the energy input only needs to be sufficient to trigger polymerization locally. Other starting materials, such as powdered starting materials (e.g., metallic materials), often have to be melted with sufficiently high-energy radiation, such as electron beams, ion beams, or laser beams of high beam intensity. It will be appreciated that radiation will often have a central region, which may be larger or smaller depending on the focus, and an area of ​​lower intensity surrounding it, where the beam intensity, i.e., the power per unit area, drops rapidly and which is not suitable for making a significant contribution to the construction of the body from the starting material.The size of the effective area will depend, among other things, on the total beam power, the focus, the beam speed and the material.

[0022] In conventional laser beam component printing processes, the effective surface profile will be the one at which the powdered starting material is melted or sintered. It is understandable that in very rare cases the beam will be completely rotationally symmetrical. On the one hand, the beam is often deflected from a central point above a build plane, especially for large bodies to be formed, in order to build the body from the starting material away from the center of the processing surface. Assuming a circular beam cross-section at normal incidence, a deviation from rotational symmetry will be observable at the corners with an inclined beam without special optical measures; however, such minor deviations should be disregarded.In the context of the invention, the surface profile is therefore only understood to be non-rotationally symmetrical if the deviations from pure rotational symmetry go beyond this effect, in particular in such a way that the deviations of the beam intensity from pure rotational symmetry for at least 10% of the effective surface profile are at least 10% greater, preferably at least 20% greater, than the described effect. In other words, even with a perpendicular section through the beam, there is a surface profile that deliberately and specifically deviates from rotational symmetry through suitable measures. This non-rotationally symmetrical surface profile is then aligned according to the invention in accordance with the track of the beam. Such a non-rotationally symmetrical surface profile can, for example, already be present in front of a galvanometer with which the beam is deflected in the processing plane.It will become apparent below that alignment can be achieved by suitable beam-forming, beam-steering or beam-limiting arrangements.

[0023] It was recognized that such a procedure allows high-quality components to be produced particularly quickly, largely regardless of the current orientation of the path, for example where the path is curved. The invention is readily designed for use with straight paths and also offers advantages, for example, where the body is built up using essentially parallel paths in a respective processing plane (which form hatches of built-up material), whereby the paths of different processing planes (in particular the paths of immediately consecutive processing planes) preferably run obliquely and / or crosswise to one another (e.g. at an angle of 90°, 60° or a prime number).Here, the alignment of the surface profile ensures that practically constant beam energy can be used in every position and at the same beam speeds, which is advantageous for obtaining a body with homogeneous properties.

[0024] Alternatively and / or additionally, it is also possible to traverse curved paths and align the effective surface profile according to the path. It should be emphasized that high-quality components can be produced quickly and largely independently of the path's curvature radius. Where the curvature radius is very large compared to the beam width, even where 90° bends are required, almost uniform heating is achieved across the entire path surface at a constant scanning speed. Due to the beam rotation, the beam width itself is not aligned tangentially in places, but rather, work is always carried out with almost the same power density along the path.

[0025] This eliminates the need to terminate a scan path and realign the workpiece, which would otherwise be necessary, not only waste time but can also cause problems at the beginning of the path. This offers obvious advantages for curved lines that correspond to large angles. This is especially true when the curved line encloses angles of at least 20°, preferably over 30°, and especially over 45°.

[0026] However, advantages are not only offered by curved lines, i.e., parts of circular lines, but also by generally curved paths. It should be noted in particular that even with curved lines, it is possible to guide rays from plane to plane in such a way that the lines or hatches repeatedly intersect at the planes and do not run largely parallel in different planes, which is disadvantageous.

[0027] It is also possible to achieve unexpectedly high quality even with small bends. While more energy is applied to the radially inner area when traversing bends with a small radius, this could inherently result in higher temperatures there, several mitigating effects come into play where the center of the bend is located to the side of the beam. Firstly, transverse heat dissipation is greater because heat can also flow away transversely. This applies to the construction of walls, but particularly to interior volumes where the track is to be placed next to existing, compacted material. There, heat is dissipated not only downwards but also laterally into this material. Secondly, the beam intensity is often lower at the edge anyway, unless special measures have to be taken.

[0028] The ideal degree of such edge drop will depend, among other things, on the material to be melted. Since the hatches must partially overlap, the edge drop should be selected such that a sufficiently deep melting or similar of the material occurs at the edge, but at the same time, the melting does not cause any adverse material changes.

[0029] Even where the center of arcs lies within the line, the slightly higher energy input usually proves to be uncritical because arcs with such tight radii are usually short, so the total duration of irradiation will be short and thus the additional energy input remains low.

[0030] It can be advantageous if the effective surface profile in the 3D component printing process has a width B1 transverse to the track direction and a width B2 in the track direction, where B1 ≥ 1.5 B2, preferably B1 ≥ 3 B2 or B1 ≥ 5 B2. Typically, an effective beam that is broadly stretched transverse to the track is desired. A sufficiently wide beam with a sufficiently wide effective surface profile transverse to the track direction is advantageous because the same area can be traversed with fewer tracks. At the same time, the beam speed along the track is often not determined by the time within which the energy required to build the body can be supplied to the starting material; rather, care must often be taken to ensure that the starting material is not heated too quickly, as this would lead to undesired spattering, which could impair the quality of the printed body.A particularly wide beam is advantageous in this respect. For this reason, beams that are at least three times wider transverse to the track direction than in the track direction are preferred, whereas with beam widths that are too narrow, the additional effort required to orient the effective surface profile is less worthwhile. It can be estimated that particularly wide beams are advantageous where particularly massive bodies are to be built, which have large volumes, especially inside the body. Here, the effective surface profiles transverse to the track direction can often be greater than 5 or 10 times the width in the track direction. As mentioned above, beams with a width of, for example, 30:1 can also be generated, and it can be estimated that even beams with a ratio of over 40:1, over 50:1, over 60:1, over 70:1, over 80:1, over 90:1 or over 100:1 can be used.It should be mentioned that in addition to a fairly wide surface profile, a pretreatment zone can also be provided in which material is preheated, for example, before it is melted, in order to make the heating less sudden even if very high jet speeds are selected.

[0031] It is generally advantageous if the width B1 of the effective surface profile, at which, for example, melting of powder material takes place, is at least 1.5 mm, at least 2 mm, at least 3 mm, at least 5 mm or at least 10 mm. It is disclosed that, with advances in available laser power and the performance stability of the elements used for beam deflection and / or shaping, in particular optical elements, even greater widths such as 5 mm, 10 mm, 15 mm or 20 mm or more can be sensibly selected. With such wide beams, assuming sufficient power, beam speeds of at least 300 mm / sec along the path, preferably over 600 mm / sec and in particular over 1000 mm / sec are preferably used, particularly where metal powder, metal carbide powder, metal nitride powder and / or ceramic powder to be sintered (for example metal oxide ceramic powder) are used as the starting material.

[0032] In a preferred embodiment, the width B2 in the track direction will be at least 0.1 mm, preferably at least 0.5 mm. Where the width B2 is as small as 0.1 mm and high-melting starting material is used, the heating speed will be very high, which can lead to splashing, particularly where oxide layers of the starting material must first be overcome by heating. A length of at least 0.5 mm is particularly advantageous, especially at jet speeds along the track of around or above 50 mm / sec, 100 mm / sec, 300 mm / sec, 450 mm / sec or 600 mm / sec. It should be noted that large jets can also be used to build up the interior of the body, for example the area at a sufficient distance from walls, whereas the outer areas such as walls can also be generated with a different, smaller jet if necessary.On the one hand, this has advantages because less power needs to be irradiated in the outer area, i.e., for the "skin" or surface of the body, and, in some cases, a finer beam guidance is desired to reduce the required post-treatment steps. It is also possible to irradiate different amounts of energy where specific material properties are to be achieved through different grain formation, the successful or non-separated remelting of material, etc. For example, by selecting suitable beam power parameters such as beam speed and beam width, a specific melting behavior can be achieved, eutectics can be formed, etc. A 3D printing machine according to the invention can therefore have two lasers of different power levels, e.g.a first laser with a power of at least 2 kW, at least 4 kW or at least 8 kW and a second laser with a power of less than 800 W, preferably less than 400 W or less than 200 W.

[0033] In a particularly preferred embodiment, the 3D component printing process is carried out in such a way that the beam is guided along a path that is at least partially curved. The effective surface profile can then be oriented according to the curvature of the path simultaneously with the traversal of the path.

[0034] It should be noted in this regard that in 3D printing, the print paths are usually known in advance, perhaps because they are predefined based on a known CAD design. This makes it particularly easy to prevent hatches from running parallel in different planes for too long. In principle, it is possible either to traverse curved paths with the beam and rotate the effective surface profile accordingly, and / or to first determine the path orientation, particularly plane-by-plane, and then rotate the beam according to a pre-planned pattern.

[0035] The shaping of the beam into a non-rotationally symmetric surface profile can be achieved by various mechanisms and / or components, e.g., by freeform optics, a liquid crystal SLM, an acousto-optical beam former, and / or a diffractive optical element (DOE). According to the claims, at least one DOE is used. Some of these mechanisms and / or components also readily allow rotation of the generated and / or to-be-generated surface profile (e.g., liquid crystal SLM or acousto-optical beam former). Other components (e.g., diffractive optical elements) can be rotated or even replaced to rotate the beam itself. In this respect, a beam-shaping device can be present, which is arranged in the beam path. The beam-shaping device can be replaceable. Alternatively or additionally, the beam-shaping device can be rotatable, e.g., by means of an additional beam-shaping rotation device.

[0036] A change in the shape and / or orientation of the surface profile is achieved by changing different diffractive optical elements, for which different DOEs in a magazine are accessed. This allows the shape and / or orientation of the surface profile to be changed, for example, from one processing plane to another. However, it is also possible to change the shape and / or orientation of the surface profile in a specific processing plane, even in real time, depending on the beam-shaping device and / or beam-shaping rotation device used.

[0037] The 3D component printing process is designed such that the effective surface profile is rotated simultaneously during track-by-track irradiation. Diffractive optical elements can be selectively interchanged to effect the alignment of the effective surface profile. Within the scope of the invention, the diffractive optical elements themselves are rotated, e.g., using a suitable mechanism. Where diffractive optical elements alone form the effective surface profile from an input beam, it is advantageous to use a circular input profile, so that the alignment of the effective surface profile then depends only on the mechanical orientation of the diffractive optical element. In such a case, the diffractive optical element can, for example, be rotated in a controlled manner.

[0038] From the above, it will be apparent that deviations between the path and the orientation of the effective surface profile can certainly occur without deviating from the invention. On the one hand, deviations can occur because the rotation of the effective surface profile, as in the case of matrix diodes, is not sufficiently finely graduated, because the mechanical tracking of the diffractive optical element is not completely precise and / or because a time offset occurs between the beam guidance on the path and the rotation of lenses, diffractive optical elements, and so on. It will be understood, however, that such deviations are preferably less than 45°, particularly preferably less than 30°, especially preferably less than 15°, and typically in the range of not more than 10°, and in particularly high-quality systems even less than 5°.

[0039] It will be appreciated that with very large deviations, the advantages of the invention cannot be fully achieved, while very small deviations have hardly any effect. Thus, even when working at the limits of possible speeds and / or energies, the advantages of particularly high precision are not necessarily achieved. The permissible tolerances may depend on the power output; however, for currently available power outputs of 5 to 10 kW, even at beam velocities >600 mm, deviations between 5° and 12°, preferably between 8° and 10°, are generally acceptable without losing any of the essential advantages of the invention.

[0040] It should also be noted that various measures are possible for generating and orienting an effective surface profile that is oriented according to a path. For example, a diode array could be combined with the diffractive optical element and cylindrical lenses, and so on.

[0041] It may be advantageous if the 3D component printing process is carried out in such a way that starting material is melted by the irradiation and a profile of the starting material-melting beam intensity transverse to the track is at least 1.5 times wider than in the direction of the track, preferably at least twice wider, particularly preferably at least three times wider, in particularly preferred variants also at least 4 times, 5 times or 10 times wider.

[0042] It should first be pointed out that the beam does not have to be used alone to heat the powdered material until it bonds with other materials, for example in selective laser sintering. Rather, it is sufficient to heat the partially formed component and / or the powder material considerably and then introduce only a small amount of additional energy for melting through irradiation. This already allows the use of quite wide beams with the beam powers achievable today, even when high track speeds are desired. This is useful when material is melted across a considerable width perpendicular to the track or when sufficiently strong energy is applied to bond it with other material. Cost-effectiveness is increased when the material-melting beam intensity perpendicular to the track is at least 1.5 times wider than in the direction of the track, preferably at least 2 times, 3 times, or 5 times.Preheating improves the usability of particularly wide beams. It is estimated that, for example, a tenfold widening is achievable. Beam alignment generally ensures that the material is melted or bonded to other materials as required, even with very high input power, especially when preheating or additional heating is applied in addition to blasting.

[0043] Where the beams are particularly wide, it is advantageous to achieve particularly good alignment. It is therefore particularly preferred if, for a beam that is at least three times wider, the deviation of the actual rotation of the effective surface profile during track-by-track irradiation is less than 25°, preferably less than 15°. Where the beam is at least five times wider, it is preferred to align the orientation to an accuracy of at least 15°. It should be noted that with very wide beams, track velocities of more than 60 cm / sec, preferably more than 1 m / sec (e.g. for Al-Si alloys) and / or track velocities of more than 50 mm / sec, preferably more than 150 mm / sec (e.g. for Al-Cu alloys) can nevertheless be achieved.

[0044] By widening the beam, among other things, the spraying behavior of the heated material is changed because the gradient to the sides is not as high. At the same time, the material can be preheated before the actual intense laser beam, which can reduce spraying in the direction of the web. It is also advantageous if, according to the 3D component printing process according to the invention, the area of ​​the profile with which the starting material is melted is preceded and / or followed by an area of ​​lower intensity in the direction of beam movement, i.e. in the direction of the web. The use of a beam with a preheating zone does not preclude the material to be melted from being additionally preheated in another way. It should be noted that preheating can also occur in local areas, but these are significantly larger than the focus area of ​​the melting beam.Examples include inductive heating with a coil guided over the layer to be melted, heating with a separate, extended beam, etc.

[0045] A post-heating area can help to slow down the solidification process where material is melted on a larger scale, which influences grain formation and possibly also the other material properties of the body to be formed by the additive process.

[0046] It is not essential that the beam intensity transverse to the direction of beam movement is homogeneous within the region of the beam profile that is intense enough to melt the starting material. It is also possible to use a profile with intermediate intensity maxima, for example, or even to use separate regions in which material melts, while no material melts in the intermediate region. Failure to melt material at certain points due to insufficient beam intensity can be used specifically where a non-compact body is desired. Furthermore, it may be possible to cause molten material in the region of higher intensity to flow to regions where the material was not melted. The resulting heat transfer can also lead to melting at these points, so that overall a particularly broad beam can be used with the same beam power.

[0047] If a beam is used that is not homogeneous across the path, but rather one that exhibits intensity peaks across the path, it is advantageous if the intensity at these intensity peaks is at least 1.3 times, preferably at least 1.5 times, and particularly preferably at least twice as high as along the area across the path where the intensity is sufficient to melt the starting material. It should be noted that partial intensity increases can also lead to a better connection to paths lying beneath the current path in some areas, thus resulting in an overall better hatch connection.

[0048] Where the wide beam transverse to the path does not have a homogeneous power distribution in the area in which material is melted, it can be advantageous if the beam intensity is higher at the outermost sections than in the center of the beam. This can be advantageous because the energy outflow is greater towards the edge, so that more energy may be needed for melting there. When determining the average beam intensity in this way, the beam intensity transverse to the direction of beam movement can typically be averaged over a region that is still small compared to the total beam width, for example by averaging over at least 0.1 mm, preferably 0.2 mm, more preferably over 0.3 mm, whereas a total beam width of over 1 mm, preferably over 2 mm, especially preferably over 3 or 5 mm is used.

[0049] The track along which the beam is guided will, in preferred embodiments, be curved at least in some areas. In such a case, it may be possible to select a mean beam intensity along a section of the profile region of the starting material melting that is radially outermost to the track, greater than the mean beam intensity along a section radially innermost to the track. In other words, a higher power density is used where the beam moves faster due to the curvature of the beam path. This is readily possible, for example, with individually controllable diodes of a diode array arrangement, but also when using a corresponding diffractive optical element. Again, it can be assumed that the beam intensity is increased or decreased accordingly at the respective outer or inner radius regions.is lowered when an average beam intensity is lower, for example averaged transversely to the beam movement direction over a length of 0.1 mm, preferably 0.2 mm or 0.3 mm, as before.

[0050] In a particularly preferred embodiment, the additive process, i.e., the 3D component printing process, can be carried out using an optical beam, particularly preferably a laser beam, preferably a continuous-wave laser beam. It should be noted that it is also possible to use particle beams, for example, electron beams or ion beams of sufficient current and energy.

[0051] Where the beam is generated by a laser, this laser can have an output power of at least 5 kW, preferably at least 8 kW, especially at least 10 kW. It should be appreciated that the achievable beam width, which is considered particularly advantageous from a technological perspective, will depend on the beam's output power. Thus, a higher power can result in the use of a more advantageously wide beam with an advantageously higher path speed.

[0052] It is possible to place several beam shaping devices spatially one behind the other and / or to use them one after the other in time. It is also possible to exchange the beam shaping devices not only to achieve different alignments, but also to provide different line widths using different beam shaping devices. This can be done in particular to create internal volumes with wider beams, while edge regions, walls, etc. are created with relatively narrow beams, which produce a higher surface quality. According to the claims, this is done by accommodating the diffractive optical elements in a magazine (e.g. a revolver-like rotatable magazine or a linear magazine), from which one DOE or a few DOEs are taken at a time. It is also possible to select the beam shaping devices depending on their performance. Alternatively or additionally, the beam shaping device (orthe DOE(s) must be selected depending on the material to be processed.

[0053] The beam-shaping device comprises at least one diffractive optical element. Where charged particles such as electrons or ions are used, a beam-shaping device is typically constructed with magnets.

[0054] As mentioned above, in a component printing method according to the invention, the beam shaping device can be rotated for beam alignment. However, this is not mandatory. It is also possible to rotate the beam source or, for example, where a laser beam is guided to a 3D printing area via a fiber optic cable, to rotate the fiber optic cable or the output coupler. The fact that the entire beam source is also rotatable has already been demonstrated using the example of a linear laser diode array.

[0055] The invention comprises a beam directing assembly according to claim 9.

[0056] Such a beam-aligning assembly will typically have a controller or a control input to steer the beam along a track that is at least partially curved and then orient the effective surface profile according to the track curvature. It should be noted that beam steering and rotation are typically preferred over component rotation.

[0057] It should also be noted that a 3D printing machine may be operated with more than one independently movable beam. Where this is the case, it may be sufficient to align only one of the beams in the manner described in the invention.

[0058] It should be noted that various beam sources are self-orientable to achieve the desired directed irradiation of the source material. Examples include electrons, positrons, protons, helium, but also heavier ions, etc.

[0059] The invention will be described below by way of example only with reference to the drawing, in which Figure 1 the beam steering unit of a 3D printing machine according to the invention; Figure 2 a collimator unit with fiber adapter and holder for a beam-aligning assembly according to the invention according to detail A of Figure 1 ; Figure 3a a detailed view of a beam alignment assembly used for beam orientation; Figure 3b a detail about it; Figure 4a an arrangement according to the claims with a rotatable magazine for different diffractive optical elements, which can be introduced alternately and / or in combination into an optical beam path of a 3D printing machine in order to achieve different shapes and / or orientations of the beam; Figure 4ban alternative embodiment according to the claims for a beam-aligning assembly with a linear magazine from which different diffractive optical elements can also be removed in order to move them into the beam path for beam shaping and / or beam orientation.

[0060] After Figure 1comprises a beam shaping and steering unit of a 3D printer, with which a body can be additively built from starting material by irradiating it with a beam in tracks, a connection 2 for an optical fiber 3 with a fiber end 3a, into which a laser beam from a high-power laser is coupled, a zoom unit 5, a variable collimator 4, a beam steering unit 6, implemented here as a galvanometer scanner, and an exit lens 7, which is designed as an F-θ lens. Connections for process monitoring 8 and a trackable camera port 9 are provided in order to be able to monitor the beam steering and process control. The corresponding arrangement is essentially conventional and suitable for guiding the beam 10 along paths in different processing planes 11a, 11b, 11c, whereby a corresponding volume layer of the body can be produced by the paths of a respective processing plane.The paths can be straight or curved. It should be noted that the beam steering unit can be assigned a controller to guide the beam track-by-track as required, e.g., over a bed of preheated powder, according to a digitized plan for a body to be additively built.

[0061] The illustrated beam shaping and steering unit differs from conventional units of a conventional 3D printer, in particular in that the beam 10 has an effective surface profile which is not rotationally symmetrical and can be aligned according to the track direction. For this purpose, an assembly 14 for beam shaping and / or beam orientation can be provided. The assembly 14 can shape the beam 10 into the non-rotationally symmetrical surface profile and, according to the claims, rotate the non-rotationally symmetrical surface profile in the processing plane, e.g., in order to align it according to the track direction. For this purpose, a freeform optics, a liquid crystal SLM, an acousto-optical beam shaping system, and, according to the claims, a diffractive optical element can be used. In the exemplary embodiment illustrated, a diffractive optical element 14 is inserted into the beam path. This will be explained in more detail with reference to Figure 2 in which parts of the beam shaping and steering unit are shown in more detail as examples.

[0062] The fiber coupling 2 is in Figure 2 shown above and comprises the fiber end 3a and a fiber socket 2b for receiving the fiber end. The fiber end 3a radiates light via a lens arrangement that collimates and allows zooming to subsequently obtain a parallel beam, indicated at reference numeral 13. The fiber arrangement and the lens arrangement behind the fiber arrangement are formed to obtain a homogeneous Gaussian beam with a generally circular cross-section. It is understood that real beams will deviate slightly from an actual Gaussian beam, but in the expanded beam, the region that, when focused, yields the area of ​​the effective surface profile will not vary by more than 10% power density.

[0063] A converging lens is provided with which the parallel beam can be focused and then directed onto the source material.

[0064] The diffractive optical element 14 can be used, for example, in the region where a parallel, homogeneous Gaussian beam is present. The diffractive optical element 14 can be designed to produce the desired non-rotationally symmetric surface profile.

[0065] To orient and / or rotate this non-rotationally symmetrical surface profile in the machining plane, the diffractive optical element 14 is rotated. To enable the rotation of the diffractive optical element 14, it is arranged in the assembly 14 in such a way that the rotation can be precisely adjusted using the machine's control system.

[0066] Such a rotating arrangement is exemplified in Figure 3aHere, the diffractive optical element is provided inside a gear with external teeth. The gear 15 can be provided with a conical sliding bearing surface 15a along its outer area (see Fig. 3b ). A toothed belt 16 can be guided from the external toothing to a drive gear 17, so that rotation of the drive gear 17 results in rotation of the diffractive optical element together with the gear 15. The toothed belt 16 can be kept tensioned, for example, with an eccentric tensioning roller 18.

[0067] The diffractive optical element itself can be manufactured, for example, by structuring an indium tin oxide (ITO) layer on a glass substrate. First, the glass substrate is coated with ITO and then a phase mask is patterned into the ITO layer. In this way, a phase shift can be generated when light passes through the glass substrate depending on the location of the passage, and intensity distributions can be specifically adjusted. It should be noted that other options exist for manufacturing a diffractive optical element.

[0068] The drive wheel 17 can be driven by an electric motor, which can be designed as a stepper motor here, to effect a controlled rotation of the drive wheel 17 and, via the toothed belt 16, also of the gear wheel 15, and thus a targeted orientation of the diffractive optical element built into the gear wheel 15. The stepper motor of the drive gear wheel 17 can be controlled by the same control unit that also controls the galvanometer scanner(s) 5 in the beam shaping and steering unit in order to guide the beam along a path that is curved, in this case in particular according to a digitized plan. The control and drives (not shown) are designed such that the paths can be curved as planned in the respective processing planes 11a, 11b, 11c. The diffractive optical element 14 can be structured such that an elongated surface profile is obtained from the circularly symmetrical profile of the beam.The control of the drive gear 17 is preferably designed such that the section of greatest extent of the effective surface profile is always exactly 10° perpendicular to the path tangent.

[0069] In this case, the stepper motor control for the diffractive optical element 14 is synchronized with the beam-directing galvano scanner 6 and is controlled as planned.

[0070] In the present embodiment, the data required for printing a component, according to which the beam is guided over the source material, is preferably available in digital form. The diffractive optical element, which is incorporated into gear 15, is aligned according to the curved beam path during irradiation. This continuously ensures that the effective surface profile of the beam is aligned according to the track direction.

[0071] According to the claims, such different diffractive optical elements can be used to shape the beam 10 differently, i.e., to generate different effective surface profiles. The generated surface profiles can have different widths, a different intensity distribution within the respective surface profile (e.g., with preheating zones), and / or different shapes (e.g., rectangular, oval, elliptical, crescent-shaped).

[0072] Different diffractive optical elements are fed via a magazine arrangement. Such a magazine arrangement is shown, for example, in Figure 4ashown. Here, different diffractive optical elements 19 are arranged in interchangeable magazine holders 20 of an interchangeable magazine 21 that is rotatable about an axis 22, wherein the respective diffractive optical elements can be inserted into the optical beam path 25 using an actuating means 23. The diffractive optical elements 19 introduced into the various holders 20 arranged on the circumference of the arrangement 21 can generate an effective surface profile that is each of the same length but rotated by a few degrees. This allows a particularly good alignment of the beam for the position of this path to be selected in advance when traversing a path. Alternatively, the various diffractive optical elements 19 can generate different surface profiles and / or surface profiles with different intensity distributions.The change of the diffractive optical elements 19 can be carried out automatically, in particular by the mentioned control according to a presetting or according to the provided digital data.

[0073] Another possibility to change a diffractive optical element, which causes a different alignment and / or shaping in the beam, is in Figure 4b . A linear interchangeable magazine holder is provided there, which accommodates several diffractive optical elements 19, e.g., in interchangeable magazine holders 20. The respective diffractive optical elements 19 can be inserted into the optical beam path 25 using an actuating means 23, which can move, e.g., transversely and / or perpendicularly to the direction of extension of the magazine. This interchangeable magazine holder can resemble a linear slide magazine, from which a selected diffractive optical element, such as a slide, can be moved into the beam path.

[0074] The process can be used with various powder mixtures known from the prior art, such as tungsten carbide, hot-work steel powder, etc. It has been shown that the beam rotation according to the invention can achieve good microstructures despite high processing speeds, and the processing speed can be selected to be approximately ten times higher than with a point-shaped or circularly symmetrical planar focus.

Claims

1. A 3D component printing process wherein a body is built up from starting material which is irradiated track by track with a beam (10), the beam (10) having an effective area profile, the effective area profile not being rotationally symmetric, and wherein the effective area profile of the beam (10) is rotated simultaneously during the track-by-track irradiation and aligned in accordance with the track direction, wherein the effective area profile is generated by a beam shaping device, wherein the beam shaping device comprises at least one diffractive optical element (14), wherein the diffractive optical element (14) is rotated for orientation and / or rotation of the effective area profile, and different diffractive optical elements (19) are arranged in a magazine (21).

2. The 3D component printing process according to the preceding claim, wherein the effective area profile has a width B1 transverse to the track direction and a width B2 in the track direction, wherein B1 ≥ 1.5 B2, preferably B1 ≥ 3 B2, wherein preferably the width B1 is at least 1.5 mm, preferably at least 2 mm or at least 3mm, and / or wherein the width B2 is at least 0.1 mm, preferably at least 0.5 mm.

3. The 3D component printing process according to any one of the preceding claims, wherein starting material is melted by irradiation and a profile of the starting material melting beam intensity, which profile is transverse to the track, is at least 1.5 times as wide as in the direction of the track, preferably at least 2 times as wide, particularly preferably at least 3 times as wide.

4. The 3D component printing process according to any one of the preceding claims, wherein the beam (10) is guided on a track which is curved at least in some portions, and the effective area profile is oriented in accordance with the curvature.

5. The 3D component printing process according to the preceding claim, wherein, in the beam movement direction, the profile area of starting material melting intensity is preceded by a preheating area of lower intensity and / or followed by an area of lower intensity.

6. The 3D component printing process according to one of the preceding two claims, wherein the beam intensity varies transverse to the beam movement direction over the profile area of starting material melting beam intensity, wherein preferably the profile area of the starting material melting beam intensity has a plurality of intensity peaks transverse to the beam movement direction, wherein the intensity at these intensity peaks is preferably at least 1.3 times, preferably at least 1.5 times or 2 times, as high as along the remaining profile area of starting material melting beam intensity, and / or wherein a mean beam intensity along at least one outermost portion of the profile area of starting material melting beam intensity in a direction transverse to the beam movement direction, is higher than a mean beam intensity along an inner portion of the profile area of starting material melting beam intensity in a direction transverse to the beam movement direction, wherein, in order to determine the mean beam intensity, in each case the beam intensity transverse to the beam movement direction is averaged over a length of 0.1 mm, preferably 0.2 mm or 0.3 mm, and / or wherein, when the beam (10) is guided on a track which is at least curved in some portions, a mean beam intensity along a portion of the profile area of starting material melting beam intensity which is radially outermost with respect to the track is higher than a mean beam intensity along a portion of the profile area of starting material melting beam intensity which is radially innermost with respect to the track, wherein, in order to determine the mean beam intensity, the beam intensity transverse to the beam movement direction is averaged over a length of 0.1 mm, preferably 0.2 mm or 0.3 mm.

7. The 3D component printing process according to any one of the preceding claims, wherein an optical beam, preferably a laser beam, particularly preferably a continuous wave laser beam, is used as the beam (10), wherein preferably the beam (10) is generated by means of a laser, the laser having an output power of at least 5 kW, preferably at least 8 kW or at least 10 kW.

8. The 3D component printing process according to any one of the preceding claims, wherein the magazine is a revolver-like rotating magazine (21) or a linear magazine, and / or wherein the different diffractive optical elements are introduced alternately and / or in combination into the beam path (25).

9. A beam orienting assembly for a 3D printing machine in which starting material is irradiated track-wise with a beam (10) to build up a body therefrom, the beam (10) having an effective area profile which is not rotationally symmetric, wherein the beam orienting assembly is adapted to rotate the effective area profile of the beam in accordance with the track direction simultaneously during the track-by-track irradiation, wherein the effective area profile is generated by a beam shaping device, wherein the beam shaping device comprises at least one diffractive optical element (14), wherein the diffractive optical element (14) is configured to be rotated for orientation and / or rotation of the effective area profile, and different diffractive optical elements (19) are arranged in a magazine (21).

10. The beam orienting assembly according to the preceding claim, wherein the beam orienting assembly further comprises a liquid crystal matrix for beam shaping and / or a beam rotating element.

11. A 3D printing machine comprising a beam orienting assembly according to one of the two preceding claims, characterized in that a control is provided for directing the beam (10) along a track curved in at least in some portions, and orienting the effective area profile in accordance with the track curvature.

12. The 3D printing machine with a beam orienting assembly according to claim 9 or claim 10, characterized in that it comprises a beam source which is configured to generate a beam (10) intended for irradiation into the beam orienting assembly, and in that the beam orienting assembly is configured to output a beam (10) irradiated therein with an oriented effective area profile, wherein preferably the 3D printing machine further comprises a beam shaping device for providing the beam (10) from the beam source with an orientable, not rotationally symmetric beam profile.