Patent Application
20190329493
The invention relates to an apparatus for additively manufacturing three-dimensional objects by means of successive layerwise selective irradiation and consolidation of layers of a build material which can be consolidated by means of an energy beam, which apparatus comprises a determination device that is adapted to determine at least one parameter relating to the energy beam.
Apparatuses for additively manufacturing three-dimensional objects in which the build material is selectively irradiated and thereby consolidated, e.g. via irradiation with an energy beam, are generally known from prior art. In such apparatuses an energy beam is guided over build material which is arranged in a build plane to deplete energy in the build material and thereby consolidate the build material dependent on the geometrical structure of the object to be additively manufactured.
Further, it is known from prior art that the amount of energy that is depleted in the build material, i.e. in a certain volume of build material, is crucial for process quality and object quality, as the consolidation behavior is significantly influenced by the amount of energy that is depleted in the respective volume of build material. Thus, it is beneficial to measure the intensity of the energy beam, e.g. via a measurement performed via an optical sensor, such as a CCD or a CMOS sensor, for example in advance to an additive manufacturing process. Such an optical sensor can be arranged in a build chamber of the apparatus and the energy beam can be guided onto the optical sensor, wherein the intensity and therefore, the energy depleted via the energy beam can be determined.
In this known approach it is not possible to take certain properties or conditions which are present in the additive manufacturing process into calculation, for example an absorption coefficient of the build material, residues that are generated during the additive manufacturing process that may influence, in particular absorb, a part of the energy beam before it is incident on the build material, or the like.
It is an object of the present invention to provide an apparatus for additively manufacturing three-dimensional objects, wherein the determination of the parameter relating to the energy beam, in particular the parameter relating to an energy that is depleted in the build material via the energy beam, is improved.
The object is inventively achieved by an apparatus according to claim 1. Advantageous embodiments of the invention are subject to the dependent claims.
The apparatus described herein is an apparatus for additively manufacturing three-dimensional objects, e.g. technical components, by means of successive selective layerwise consolidation of layers of a powdered build material (“build material”) which can be consolidated by means of an energy beam, in particular a laser beam or an electron beam. A respective build material can be a metal, ceramic or polymer powder. A respective energy beam can be a laser beam or an electron beam. A respective apparatus can be an apparatus in which an application of build material and a consolidation of build material is performed separately, such as a selective laser sintering apparatus, a selective laser melting apparatus or a selective electron beam melting apparatus, for instance.
The apparatus may comprise a number of functional units which are used during its operation. Exemplary functional units are a process chamber, an irradiation device which is adapted to selectively irradiate a build material layer disposed in the process chamber with at least one energy beam, and a stream generating device which is adapted to generate a gaseous fluid stream at least partly streaming through the process chamber with given streaming properties, e.g. a given streaming profile, streaming velocity, etc. The gaseous fluid stream is capable of being charged with non-consolidated particulate build material, particularly smoke or smoke residues generated during operation of the apparatus, while streaming through the process chamber. The gaseous fluid stream is typically inert, i.e. typically a stream of an inert gas, e.g. argon, nitrogen, carbon dioxide, etc.
As described before, the invention relates to an apparatus for additively manufacturing three-dimensional objects with a determination device which is adapted to determine at least one parameter relating to the energy beam that is used in the additive manufacturing process to consolidate the build material. The invention is based on the idea that the determination device comprises at least one determination unit adapted to determine at least one first parameter of a reflected part of the energy beam, which is reflected at the build plane, wherein the determination device is adapted to determine a difference between a reference parameter and the at least one first parameter of the reflected part.
Thus, it is inventively achieved that a first parameter of a reflected part of the energy beam can be determined to extrapolate on the amount of energy that has been depleted in the build material. For example, the part of the energy beam that is reflected at the build plane, i.e. a plane (surface) in which build material is arranged to be irradiated and thereby consolidated to form the three-dimensional object, depends on the amount of energy (and the part that is absorbed in the build plane). Dependent on the conditions under which the additive manufacturing process is performed, the amount of energy (part of the energy beam) that is depleted in the build material and the amount of energy (part of the energy beam) that is reflected at the surface of build material can vary. The determination device of the inventive apparatus may compare the first parameter relating to the reflected part of the energy beam with a reference parameter and therefore, determine a difference between the reference parameter and the first parameter of the reflected part of the energy beam.
For example, the reference parameter can define a specific (target) value or a value range, such as an interval, wherein the reference parameter relates to a proper energy value, e.g. an energy that should be depleted in the build material to achieve a defined consolidation behavior. Thus, if the first parameter of the reflected part of the energy beam matches the reference parameter, the proper amount of energy is depleted in the build material. If the first parameter of the reflected part of the energy beam differs from the reference parameter, it is possible that too much or too little energy is depleted in the build material. Thus, it is possible to determine whether a proper amount of energy is depleted in the build material and thereby, whether the irradiation process and the consolidation process of the build material are performed under suitable process conditions, whereas, if a difference between the reference parameter and the first parameter of the reflected part of the energy beam is determined, an adjustment to the process conditions can be deemed necessary, such as decreasing or increasing the intensity of the energy beam, for instance.
The reference parameter may be defined or may be determined. For example, a determination of the reference parameter is possible, in particular via a corresponding determination unit, as will be described below. It is also possible to define the reference parameter, for example in a control unit or via a user interface. A user of the apparatus, e.g. a plant operator, may enter the reference parameter via the user interface, wherein the reference parameter may be stored in a corresponding control unit of the apparatus. It is also possible to enter information relating to the additive manufacturing process, for example which type of build material is used, and to have the control unit determine the reference parameter based on the entered information.
According to another embodiment of the inventive apparatus, the determination device may be adapted to determine the first parameter of at least one reflected part of the energy beam and adapted to determine at least one second parameter of an initial part of the energy beam. Thus, the first parameter relates to the reflected part of the energy beam, which is reflected at the build plane and the second parameter relates to an initial part of the energy beam. The term “initial part” may refer to a part of the energy beam, which is generated via a corresponding energy source, wherein the second parameter is determined before the initial part is incident on the build plane, e.g. the “initial” part refers to a part of the energy beam that is coupled into the optical system of the apparatus before it is incident on the build material. Therefore, the initial part of the energy beam relates directly to the energy beam that is coupled into the optical system of the additive manufacturing apparatus without interfering with the process atmosphere or residues in the process chamber. In particular, the second parameter is determined before the initial part of the energy beam is incident on the build plane. The second parameter may therefore, be used as reference parameter.
It is possible to use the second parameter of the initial part of the energy beam and compare the first parameter with the second parameter, which first parameter is related to the reflected part of the energy beam, wherein the determination device may compare both parameters and therefore, extrapolate on the process conditions, in particular the consolidation behavior of the build material that is arranged in the build plane. In particular, it is possible to determine to which degree the energy beam that is incident on the build plane is absorbed in the build material and which part of the energy beam is reflected at the build plane.
The determination device of the inventive apparatus may further comprise at least one first determination unit adapted to determine the first parameter of the at least one reflected part of the energy beam and at least one second determination unit adapted to determine the at least one second parameter of the initial part of the energy beam, wherein the determination device may be adapted to determine a difference between the second parameter of the at least one initial part and the at least one first parameter of the reflected part of the energy beam.
Thus, it is possible that the determination device comprises a first determination unit and a second determination unit, wherein the first determination unit is used to determine the first parameter relating to the reflected part of the energy beam. Further, the determination device comprises the second determination unit to determine the second parameter which relates to the initial part of the energy beam, as described before. As described before, the second parameter of the at least one initial part of the energy beam may be used as reference parameter or may be deemed as reference parameter. The determination device is adapted to determine a difference between both parameters, i.e. the second parameter (reference parameter) and the first parameter. Hence, it is possible to compare the first parameter and the second parameter and therefore, determine the difference between both parameters. The first parameter of the reflected part of the energy beam and/or the second parameter of the initial part of the energy beam are preferably the same type of parameter, for example an energy of the respective part of the energy beam or an intensity (power) of the respective part of the energy beam or the like.
By comparing the first with the second parameter it is possible to determine the amount of the energy beam which is guided onto the build plane that is received within the build material, i.e. absorbed in the build material. In other words, the second parameter of the initial part of the energy beam, e.g. the intensity of the initial part of the energy beam, defines in comparison to the first parameter of the reflected part of the energy beam, e.g. the intensity of the reflected part of the energy beam, the ratio or part of the energy beam that is absorbed in the build material. Thus, the comparison between the first and second parameter or the ratio between the first and the second parameter, defines how much of the energy beam is absorbed in the build material and how much of the energy beam is reflected at the build material. Hence, the determination device is adapted to determine whether the proper amount of energy is depleted in the build material or if too much or too little energy is depleted in the build material. Therefore, the determination device is adapted to determine whether the irradiation process and therefore, the consolidation process is performed under proper conditions.
The first parameter and/or the second parameter preferably are intensities or relate to an intensity (power) of the energy beam and/or an absorbed intensity that is absorbed in the build material. Thus, the first parameter and/or the second parameter may relate to an intensity of the respective part of the energy beam, i.e. the initial part of the energy beam or the reflected part of the energy beam.
Further, the first parameter may relate to topography information of the build material that is arranged in the build plane. As described before, the first parameter of the reflected part of the energy beam relates to the amount of energy or the ratio of the energy beam that is reflected at the build plane. Thus, it is possible to determine the topography of the build material that is arranged in the build plane, e.g. variances in the topography of the surface of build material arranged in the build plane via the first parameter of the reflected part of the energy beam. Variances in the topography of the build material will also result in a variance of the first parameter, as the first parameter, for example the intensity of the reflected part of the energy beam, varies with the topography of the build material the energy beam is incident on, e.g. the direction in which the reflected part of the energy beam propagates. For example, if variances in the topography, such as warps of the object or the build material arranged in the build plane occur, the amount of energy or the ratio of the energy beam that is reflected or scattered and not properly guided to the first determination unit, will increase, as the energy beam is scattered or reflected into another direction and is not incident on the corresponding (first) determination unit. Thus, the variances in the first parameter may directly be related to variances in the topography of the build material arranged in the build plane.
The inventive apparatus may further be improved in that the determination device may be adapted to determine at least one process parameter, wherein the determination device may be adapted to perform the determination of the first parameter dependent on the process parameter. As described before, the additive manufacturing process is performed under various conditions that may directly influence the process quality and/or the object quality, in particular directly influence the consolidation behavior caused by the irradiation of build material. According to this embodiment, the determination device may take into calculation at least one of those process parameters to perform the determination of the first parameter of the reflected part of the energy beam dependent on the process parameter. Thus, process parameters that describe or influence the additive manufacturing process may be determined and taken into calculation to ensure that the first parameter of the reflected part of the energy beam is properly determined.
The process parameter may be or may relate to a build material, in particular an absorption coefficient of the build material, and/or an angle of incidence of the energy beam on the build plane and/or residues generated in the additive manufacturing process. Thus, it is possible to take various process parameters into calculation that influence the amount of energy or the ratio of the energy beam that is reflected or absorbed. For example, the build material that is used in the additive manufacturing process, in particular the absorption coefficient of the build material used in the additive manufacturing process, directly influences the amount of energy that can be depleted in the build material or the ratio of the energy beam that is absorbed via the build material.
Further, the angle of incidence under which the energy beam is incident on the build material that is arranged in the build plane also directly influences the part of the energy beam that is absorbed and a part of the energy beam that is reflected at the build plane. Another process parameter that can be taken into calculation that may influence the ratio of the energy beam that is absorbed in the build material are residues that are generated in the additive manufacturing process, such as a soot, smoke or smolder or non-consolidated build material particles, such as swirled up build material, the atmosphere inside the process chamber is charged with. The energy beam that is guided through the atmosphere of the process chamber can be partially absorbed via those residues, wherein determining the residues and therefore, taking into calculation the ratio of the energy beam that is absorbed via the residues improves the determination of the first parameter, as well.
According to another embodiment of the inventive apparatus, the beam splitting unit may be provided that is adapted to split the initial part off the energy beam, wherein an irradiation device of the apparatus may be adapted to guide the reflected part of the energy beam in line with the energy beam and to guide the reflected part of the energy beam through the beam splitting unit towards the first determination unit. Thus, a beam splitting unit can be provided to split the initial part off the energy beam, e.g. an energy beam incident on the beam splitting unit, wherein a (minor) part of the energy beam is split off the energy beam and guided to the second determination unit, for instance. The reflected part of the energy beam, which propagates from the build plane, is guided in line with the energy beam, e.g. guided via the same irradiation device, in particular a scanning mirror, that is used to guide the energy beam over the build plane towards the beam splitting unit. The reflected part of the energy beam may pass the beam splitting unit and can therefore, be guided to the first determination unit.
Further, a second beam splitting unit may be provided that is adapted to separate the reflected part of the energy beam from radiation emitted from the build plane. Hence, the second beam splitting unit may be provided, for example in succession to the first beam splitting unit with respect to the propagating direction of the reflected part of the energy beam. The second beam splitting unit is adapted to separate radiation that is emitted from the build plane, such as a separation of thermal radiation from the reflected part of the energy beam which is reflected at the build plane. In other words, radiation that is emitted from the build plane and the reflected part of the energy beam that is reflected at the build plane can be guided in line with the energy beam (in the opposite direction), e.g. via the same irradiation device towards the second beam splitting unit. Thus, radiation emitted from the build plane may also be adapted to pass the first beam splitting unit. The second beam splitting unit separates the radiation emitted from the build plane from the reflected part of the energy beam to allow the reflected part of the energy beam to propagate further towards the first determination unit, wherein the radiation emitted from the build plane may propagate towards another (optional) determination unit adapted to determine parameters of the radiation emitted from the build plane.
Additionally or alternatively, the or a first determination unit may be arranged on a transparent wall element delimiting a process chamber in which the additive manufacturing process is performed, wherein the transparent wall element is transparent for the reflected part of the energy beam. In other words, the transparent wall element forms a “window” through which the reflected part of the energy beam can at least partially pass and leave the process chamber towards the first determination unit.
The term “transparent” in this context may refer to the ability of the reflected part of the energy beam to at least partially pass the transparent wall element. Of course, a transparent wall element which can be passed only by a certain ratio of the reflected part of the energy beam, preferably above a defined ratio, e.g. 80% of the reflected part of the energy beam, is also deemed as “transparent”. According to this embodiment it is possible to arrange the first determination unit in line with the transparent wall element that delimits the process chamber of the apparatus to allow for the reflected part of the energy beam or a reflected part of the energy beam to propagate through the transparent wall element towards the first determination unit which is adapted to determine the first parameter of the reflected part of the energy beam. Although, it is not necessary, the first determination unit may be arranged directly on the transparent wall element. However it is also possible to arrange the first determination unit in line with the transparent wall element with respect to the propagation direction of the reflected part of the energy beam, for example spaced a defined distance away from the transparent wall element, e.g. 5 cm.
The determination device of the inventive apparatus may comprise at least one optical filter unit that is adapted to filter radiation with a wavelength or a wavelength range differing from the energy beam, in particular differing from 1070 nm. By providing the optical filter unit it is ensured that only the reflected part of the energy beam and/or a the initial part of the energy beam reach the corresponding determination unit, whereas other types of radiation are filtered by the optical filter unit, such as thermal radiation that is emitted from the build plane or a marker beam, which will be absorbed or reflected or scattered at the optical filter unit and cannot pass the optical filter unit to be incident on the determination units.
The determination device may preferably further comprise two optical filter units, wherein the first optical filter unit is arranged between an energy source generating the energy beam and the second determination unit and the first optical filter unit is arranged between the build plane and the first determination unit. Thus, the energy beam that is generated via a corresponding energy source may be incident on the first beam splitting unit, via which the initial part of the energy beam is split off the energy beam. The second optical filter unit can be arranged between the energy source and the second determination unit to filter the radiation components from the initial part of the energy beam. The first optical filter unit may be arranged in advance to the first determination unit with respect to the propagation direction of the reflected part of the energy beam. Thus, the reflected part of the energy beam, which is reflected at the build plane propagates through the optical system towards the first determination unit. Preferably, the first optical filter unit is arranged between the second beam splitting unit and the first determination unit.
Besides, the invention relates to a determination device for an apparatus for additively manufacturing three-dimensional objects by means of successive layerwise selective irradiation and consolidation of layers of a build material which can be consolidated by means of an energy beam, in particular an inventive apparatus, as described before, wherein the determination device comprises at least one determination unit adapted to determine at least one first parameter of a reflected part of the energy beam, which is reflected at a build plane, wherein the determination device is adapted to determine a difference between a reference parameter and the at least one first parameter of the reflected part.
Further, the invention relates to a method for determining at least one parameter of an energy beam used in an apparatus for additively manufacturing three-dimensional objects by means of successive layerwise selective irradiation and consolidation of layers of a build material which can be consolidated by means of an energy beam, wherein the energy beam is guided onto build material that is arranged in a build plane, wherein the energy beam is partially reflected at the build plane, wherein at least one first parameter of a reflected part of the energy beam, which is reflected at the build plane and a difference between a reference parameter and the at least one first parameter of the reflected part is determined.
Exemplary embodiments of the invention are described with reference to the Fig. The Fig. are schematic diagrams, wherein
The apparatus 1 further comprises a determination device 8 that comprises a first determination unit 9 that is adapted to determine a first parameter of a reflected part 10 of the energy beam 5, which is reflected at the build plane 7. The determination device 8 is further adapted to determine a difference between a reference parameter and the first parameter of the reflected part 10. It is possible that the reference parameter is defined, in particular via a control unit (not shown) or via a user interface (not shown). In this exemplary embodiment the reference parameter is determined via the determination device 8, in particular via a second determination unit 11.
Via the second determination unit lithe determination device 8 is adapted to determine a second parameter of an initial part 12 of the energy beam 5, wherein the determination device 8 is adapted to determine a difference between the first parameter of the reflected part 10 and the second parameter of the initial part 12. In this exemplary embodiment, the apparatus 1 comprises a first beam splitting unit 13 that is adapted to split the initial part 12 off the energy beam 5 as the energy beam 5 is incident on the first beam splitting unit 13. The energy beam 5 is guided via the first beam splitting unit 13 to the irradiation device 6 which is adapted to guide the energy beam 5 in the build plane 7 or across the build plane 7, respectively.
The reflected part 10 of the energy beam 5 is reflected at the build plane 7, in particular the surface of build material 3 that is arranged in the build plane 7. The reflected part 10 therefore, propagates towards the irradiation device 6 and is guided in line (in the opposite direction) with the energy beam 5. Thus, the reflected part 10 of the energy beam 5 is incident on the first beam splitting unit 13 and may pass the first beam splitting unit 13 to further propagate towards the first determination unit 9. As can be derived from
As can further be derived from
The determination device 8 further comprises a second optical filter unit 15 that is arranged between the energy source 4 and the second determination unit 11. Similar to the first optical filter unit 14, in particular identical to the first optical filter unit 14, the second optical filter unit 15 is adapted to filter radiation other than the initial part 12 of the energy beam 5. Hence, only the initial part 12 of the energy beam 5 may pass the second optical filter unit 15 and can be incident on the second determination unit 11. The first and second determination unit 9, 11 may be built as optical sensors or may comprise optical sensors, such as a CCD or CMOS sensors, in particular a photo diode and/or a camera. Hence, the first and the second determination unit 9, 11 are adapted to determine various parameters of the reflected part 10 or the initial part 12 of the energy beam 5, in particular the power or the intensity of the respective part 10, 12, in particular spatially resolved.
The first parameter of the reflected part 10 of the energy beam 5 may also relate to topography information indicating whether the topography of the build material 3 arranged in the build plane 7 is even or whether variances in the topography of the build material 3 occur. As the intensity or the power of the reflected part 10 that is incident on the first determination unit 9 varies, if the surface of build material 3 arranged in the build plane 7 varies in height or is unevenly distributed or the surface of the object 2 arranged in the build plane 7 is not plane. Thus, the reflected part 10 of the energy beam 5 will be scattered or reflected into a different direction and cannot be properly guided in line towards the first determination unit 9. Further, the reflection characteristic in which the energy beam 5 is reflected at the build plane 7 generating the reflected part 10 of the energy beam 5 also varies with the topography of build material 3 that is arranged in the build plane 7.
Further, the determination device 8 comprises a second beam splitting unit 16 that is adapted to split the radiation that is emitted from the build plane 7, in particular separate the reflected part 10 of the energy beam 5 from other types of radiation, such as thermal radiation emitted from the build plane 7. The determination device 8 comprises a third determination unit 17 that is adapted to determine a parameter of radiation that is emitted from the build plane 7, in particular thermal radiation, such as the intensity of thermal radiation or the temperature of build material 3 arranged in the build plane 7, for instance.
Deviant from the setup that is depicted in
Therefore, a control of the energy that is depleted within the build material 3 is feasible to ensure that a proper amount of energy is absorbed, which directly influences the consolidation behavior of irradiated build material 3 arranged in the build plane 7.
Further, the determination device 8 according to the exemplary embodiment that is depicted in
The determination device 8 of the apparatus 1 depicted in
Of course, all features, details and advantages described with respect to the individual embodiments can arbitrarily be exchanged, transferred or combined. Self-evidently, the inventive method can be performed on the inventive apparatus 1, preferably using an inventive determination device 8.
| Number | Date | Country | Kind |
|---|---|---|---|
| 18169957.0 | Apr 2018 | EP | regional |
