Method of operating an irradiation system, irradiation system and apparatus for producing a three-dimensional workpiece

Abstract

In a method of operating an irradiation system (10) for irradiating layers of a feedstock powder with electromagnetic or particle radiation to produce a three-dimensional workpiece (110), it is determined, depending on the geometry of the respective layer of the workpiece (110) to be produced, whether a region of the layer (11) of the feedstock powder to be selectively irradiated with electromagnetic or particle radiation is affected by particulate impurities or substantially not affected by particulate impurities. When selectively irradiating a region of the layer (11) of the feedstock powder with electromagnetic or particle radiation, the energy density applied by the radiation beam (14a, 14b) to the region of the layer (11) of the feedstock powder is controlled in such a way that the energy density is higher in the case where it is determined that the region of the layer (11) of the feedstock powder is affected by particulate impurities than in the case where it is determined that the region of the layer (11) of the feedstock powder is substantially not affected by particulate impurities.

Description

Technical Field

[0001] This invention relates to a method of operating an irradiation system for irradiating layers of raw material powder with electromagnetic radiation or particle radiation to produce three-dimensional workpieces. Furthermore, this invention relates to such an irradiation system. Finally, this invention relates to an apparatus for producing three-dimensional workpieces. Background Technology

[0002] Powder bed melting is a layer-by-layer additive manufacturing process that allows powdered raw materials, particularly metals and / or ceramics, to be shaped into complex three-dimensional workpieces. To do this, layers of raw powder are applied to a carrier and subjected to laser irradiation in a position-selective manner, according to the desired geometry of the workpiece to be produced. The laser irradiation penetrating the powder layers causes heating, thus melting or sintering the raw powder particles. Further layers of raw powder are then continuously applied to the laser-treated layers on the carrier until the workpiece achieves the desired shape and dimensions. Based on CAD data, powder bed melting can be used for the production or restoration of prototypes, tools, replacement parts, high-value components, or medical prostheses (e.g., dental or orthopedic prostheses).

[0003] An exemplary apparatus for producing three-dimensional workpieces by powder bed melting, as described in EP 3 321 003 B1, includes a processing chamber housing a carrier for receiving raw material powder. An irradiation device is provided to selectively irradiate the raw material powder on the carrier with electromagnetic radiation or particle radiation to produce the workpiece. A protective airflow is directed through the processing chamber to establish the desired atmosphere within the processing chamber and to remove impurities from the processing chamber.

[0004] When a three-dimensional workpiece is fabricated on a carrier in a powder bed fusion apparatus, the radiative energy introduced into the raw material powder causes it to melt and / or sinter. Specifically, a molten pool is generated in the area where the radiation beam impacts the raw material powder. During the melting of the raw material powder, welding fumes are generated, which typically form a plume containing light particulate impurities, such as smoke particles, dispersed raw material powder particles, and soot particles. Although the majority of the light welding fume particles are expelled from the processing chamber by being entrained by the airflow guided through the processing chamber, the plume of light particulate impurities may still undesirably shield and / or scatter the radiation beam that is guided through the plume before impacting the raw material powder to be irradiated.

[0005] Furthermore, the evaporation of raw materials from the molten pool can cause spatter particles to be ejected from the pool. However, spatter particles ejected from the molten pool in molten form and subsequently solidified are often too heavy to be carried away by the airflow guiding through the processing chamber. Therefore, these spatter particles deposit on the surface of the unirradiated raw material powder in the selectively irradiated raw material powder layer or on the surface of the newly formed workpiece layer. Consequently, these solidified spatter particles can lead to defects and / or irregularities in the resulting workpiece. Summary of the Invention

[0006] The object of this invention is to provide a method for operating an irradiation system (used for irradiating layers of raw material powder with electromagnetic radiation or particle radiation to produce three-dimensional workpieces) and such an irradiation system enabling the production of high-quality workpieces. Furthermore, this invention relates to an apparatus for producing three-dimensional workpieces, which enables the production of high-quality workpieces.

[0007] In methods of operating an irradiation system (used to irradiate layers of raw material powder with electromagnetic or particle radiation to produce three-dimensional workpieces), the raw material powder layer selectively irradiated with electromagnetic or particle radiation is subdivided into multiple regions according to the geometry of the corresponding layer of the workpiece to be produced. For example, the raw material powder layer can be subdivided into multiple strips. The strips can extend substantially parallel to each other. Furthermore, the strips can extend substantially perpendicular to the flow direction of the airflow guided through the raw material powder layer to remove particulate impurities. Alternatively or additionally, it is conceivable to subdivide the raw material powder layer into multiple strips that can extend substantially parallel to the flow direction of the airflow guided through the raw material powder layer. The raw material powder layer regions can remain fixed for all raw material powder layers to be irradiated during workpiece production, or they can vary depending on the size, shape, and / or position of the workpiece layer to be produced by selectively irradiating a corresponding raw material powder layer.

[0008] For at least one region, before selectively irradiating the region with electromagnetic radiation or particle radiation, it is determined whether the region is affected by particulate impurities or substantially unaffected by particulate impurities. In the context of this application, the term "affected by particulate impurities" should be understood to mean that a region of the raw material powder layer is in a state that could impair the quality of the workpiece layer portion produced by selectively irradiating the region of the raw material powder layer. Therefore, in the context of this application, the term "substantially unaffected by particulate impurities" should be understood to mean that a region of the raw material powder layer is in a state that allows for the production of a workpiece layer portion by selectively irradiating a region of the raw material powder layer that is substantially free of defects and irregularities caused by particulate impurities.

[0009] An irradiation system for selectively irradiating a raw material powder layer with electromagnetic or particle radiation may include a radiation beam source (particularly a laser beam source) and additionally may include at least one optical unit for splitting, guiding, and / or processing at least one radiation beam emitted by the radiation beam source. The optical unit may include optical elements such as objectives and a scanner unit, which preferably includes diffractive optical elements and deflecting mirrors. The irradiation system can irradiate the raw material powder layer with a single radiation beam. However, it is also conceivable that the irradiation system can irradiate the raw material powder layer with two or more radiation beams.

[0010] A layer of raw material powder can be applied to the surface of a carrier using a powder application device that moves through the carrier to distribute the raw material powder. The carrier can be a rigid, fixed carrier. However, preferably, the carrier is designed to be vertically movable, such that as the workpiece is built within the layer of raw material powder, the carrier can move downwards vertically as the workpiece's construction height increases. Furthermore, the carrier can be equipped with cooling and / or heating devices configured to cool and / or heat the carrier. The carrier and the powder application device can be housed within a processing chamber, which can be sealed to the ambient atmosphere. An inert gas atmosphere can be established within the processing chamber by introducing airflow through a gas inlet. After the airflow is guided through the processing chamber and across the layer of raw material powder applied to the carrier, the airflow exits the processing chamber through a gas outlet. The raw material powder applied to the carrier within the processing chamber is preferably a metal powder, particularly a metal alloy powder, but can also be ceramic powder or powder containing different materials. The powder can have any suitable particle size or particle size distribution. However, it is preferred to process powders with a particle size <100 μm.

[0011] Particulate impurities that can affect the raw material powder layer region in the most recent or subsequent layers can be particles, such as solidified splatter particles, that are too heavy and / or too large to be removed from the processing chamber by airflow guided through the processing chamber. Therefore, these particles deposit on the surface of the (still) unirradiated raw material powder in the recently selectively irradiated raw material powder layer, or on the surface of the workpiece layer just produced by selectively irradiating the raw material powder layer. If particulate impurities generated during the irradiation of the raw material powder layer are deposited in the still-to-be-irradiated portion of the raw material powder layer, these particulate impurities may have already affected the quality of the workpiece layer portion produced by selectively irradiating that portion of the raw material powder layer. However, the quality of the workpiece layer portion produced by selectively irradiating that portion of the raw material powder layer can also be affected by particulate impurities generated during the irradiation of the previous raw material powder layer and covering / bonding into the raw material powder of that portion of the raw material powder layer.

[0012] Alternatively or additionally, particulate impurities intended to affect the region of the raw material powder layer can be lighter particles, such as welding fume particles, dispersed raw material powder particles, and soot particles. These particles typically form a plume of smoke originating from a molten pool of raw material powder generated in the region where the radiation beam impacts the raw material powder. The plume of smoke from these lightweight particulate impurities can shield and / or scatter the radiation beam, which is guided through the plume before impacting the raw material powder layer to be irradiated. This can also affect the quality of the workpiece layer portion produced by selectively irradiating a region of the raw material powder layer.

[0013] When at least one region of a raw material powder layer is selectively irradiated with electromagnetic radiation or particle radiation (after determining whether the region is affected by particulate impurities or is substantially unaffected by particulate impurities), the energy density applied to the region of the raw material powder layer by the radiation beam is controlled. More specifically, the energy density is controlled in such a way that the energy density is higher when the region of the raw material powder layer is determined to be affected by particulate impurities than the energy density is higher when the region of the raw material powder layer is determined to be substantially unaffected by particulate impurities.

[0014] Because the energy density applied to the raw powder layer region increases when it is affected by particulate impurities, when the radiation beam is guided through this region, not only are the raw powder particles melted, but also the solidified spatter particles deposited on or embedded in the raw powder layer are melted. Furthermore, shielding and / or scattering effects caused by plumes of light particulate impurities (e.g., by the molten pool of another laser beam or by the blocked beam itself) can be compensated for. Therefore, irregularities or defects in the workpiece layer due to incomplete melting of the raw powder particles and / or particulate impurities can be minimized or even avoided.

[0015] Simultaneously, by applying a lower energy density to the raw material powder layer region without it being affected by particulate impurities, the undesirable effects of excessive energy application are avoided, such as the formation of an undesirable large molten pool and increased splashing of molten material from the pool due to over-evaporation. Finally, the raw material powder layer region is defined to be affected by or substantially unaffected by particulate impurities before irradiation begins, and the energy density applied to this region can be customized in a particularly reliable and precise manner. In summary, the overall quality of the workpiece layer produced by selectively irradiating the raw material powder layer can be improved.

[0016] The energy density applied to the region of the raw material powder layer can be controlled by appropriately adjusting at least one of the power, focal diameter, and focal shape of the radiation beam guided through the raw material powder layer. Specifically, the energy density applied to the region of the raw material powder layer can be increased by increasing the power of the radiation beam, decreasing the focal diameter of the radiation beam, and / or by changing the focal shape of the radiation beam in a manner that reduces the focal area of ​​the radiation beam. In the context of this application, the term "focal shape of the radiation beam" can be understood not only as the external shape or outline (e.g., circular, annular, or rectangular) of the radiation beam spot incident on the raw material powder, but also as the internal intensity distribution (e.g., Gaussian distribution, cap distribution, or annular distribution) within the focal spot.

[0017] Alternatively or additionally, the energy density applied to the region of the raw material powder layer can be controlled by appropriately adjusting at least one of the scanning speed and the scanning pattern, according to which the radiation beam is guided through the raw material powder layer. In particular, the energy density applied to the region of the raw material powder layer can be increased by reducing the scanning speed and / or by modifying the scanning pattern in a manner that reduces the distance between adjacent scanning vectors defining the scanning pattern.

[0018] Based on the flow direction of the airflow guided through the raw material powder layer, i.e., based on the flow direction of the airflow guided through the processing chamber, it is possible to determine whether the area of ​​the raw material powder layer is affected by particulate impurities or is substantially unaffected by particulate impurities, so as to establish the required atmosphere in the processing chamber and remove particulate impurities from the processing chamber.

[0019] Other processing parameters that may affect splash and / or plume generation can be considered, such as the material of the raw powder, the protective gas used, and the incident angle of the irradiation beam. Therefore, the determination of whether a region of the raw powder layer is affected or substantially unaffected by particulate impurities can also be performed based on the splash trajectory determined by the flow velocity of the airflow guided through the raw powder layer, the gas flow distribution of the airflow guided through the raw powder layer, and / or the particle weight of the particulate impurities.

[0020] For example, when a radiation beam irradiates a region of the raw material powder layer (which is located upstream of the raw material powder layer relative to the flow direction of the airflow guided through it, i.e., near the gas inlet of the processing chamber and far from the gas outlet of the processing chamber), the raw material powder layer region (located downstream of the raw material powder layer relative to the flow direction of the airflow guided through it, i.e., far from the gas inlet of the processing chamber and near the gas outlet of the processing chamber) is typically affected by a plume of splatter particles and light particulate impurities emitted from the molten pool. Therefore, the raw material powder layer region located downstream of the raw material powder layer can be identified as being affected by particulate impurities and, when selectively irradiated, is affected by an increased energy density.

[0021] The region extending a predetermined distance from the upstream edge of the raw material powder layer along the flow direction of the airflow guided through the raw material powder layer can be considered as a region of the raw material powder layer that is substantially unaffected by particulate impurities. In the context of this application, the term "upstream edge" refers to the edge of the raw material powder layer facing the gas inlet through which the airflow to be guided through the raw material powder layer is introduced into the processing chamber.

[0022] Alternatively or additionally, a region extending a predetermined distance from the upstream irradiation start position along the flow direction of the airflow guided through the raw material powder layer can be considered a region of the raw material powder layer substantially unaffected by particulate impurities. In the context of this application, the term "upstream irradiation start position" refers to the irradiation location, i.e., the location where the irradiation beam strikes the raw material powder layer, at the furthest point in the direction of the gas inlet through which the airflow guided through the raw material powder layer is introduced into the processing chamber. The predetermined distance can be determined based on an estimate of the "purification effect" of the airflow guided through the processing chamber, and is preferably selected in a manner that ensures the raw material powder layer region is substantially unaffected by particulate impurities.

[0023] Before commencing the production of a three-dimensional workpiece, a raw material powder layer selectively irradiated with electromagnetic or particle radiation can be subdivided into multiple regions. For example, before the production process for generating the workpiece begins, the raw material powder layer can be subdivided into multiple strips, multiple squares, rectangles, or other shaped regions. As mentioned above, when subdividing the raw material powder layer into individual regions, the shape and / or location of the workpiece layer produced by selectively irradiating the raw material powder layer can be taken into consideration. In particular, when the parameters of the workpiece layer should be considered, computer-aided simulation can be used to perform the subdivision.

[0024] However, it is also conceivable that during the production of a three-dimensional workpiece, the raw material powder layer, selectively irradiated with electromagnetic radiation or particle radiation, is subdivided into multiple regions. For example, when irradiating another region of a previous raw material powder layer or (the same) raw material powder layer, the development of splash particles and / or smoke plumes is monitored by a suitable sensor device, and then the shape and size of the region are defined based on the output of the sensor device. For example, once a threshold for particulate contamination of the region is reached, the edges of the region to be defined can be set. However, a threshold contamination value can also be considered when defining the regions before starting the production of the three-dimensional workpiece.

[0025] Sensor devices may include, for example, a camera that directly monitors the development of spatter particles and / or plumes of smoke generated during the irradiation of the raw powder layer. However, the camera can also be used to directly detect solidified spatter particles deposited on the surface of the raw powder layer before the application of the next raw powder layer. Therefore, monitoring results captured by the camera during the monitoring of the previous raw powder layer can be considered when determining whether a region of the raw powder layer is substantially unaffected by particulate impurities or is affected by particulate impurities. When monitoring the raw powder layer with a camera, the raw powder layer can be observed from different angles and / or illuminated, and / or illuminated with light of different wavelengths. Alternatively or additionally, a molten pool monitoring system can be employed to detect the emission of near-infrared radiation from the molten pool and / or monitor vapor capillaries, for example, for detecting capillary fluctuations. The amount and direction of spatter particles and / or plumes of smoke can be determined from the detected emission. The scattering of radiation on particulate impurities resulting from the interaction of another radiation beam on the powder can also be determined from the signal.

[0026] The size and / or shape of the defined regions when subdividing the raw material powder layer can vary between individual raw material powder layers and / or within (the same) raw material powder layer. Furthermore, before commencing production of the three-dimensional workpiece, the raw material powder layer can be subdivided into multiple regions, the size and / or shape of which can be adjusted as needed.

[0027] Before commencing production of the 3D workpiece, it can be determined whether a region of the raw material powder layer is affected by particulate impurities or is substantially unaffected by them. For example, a region of the raw material powder layer can be defined as being affected by particulate impurities or substantially unaffected by them based on its location within the raw material powder layer. Computer-aided simulation can be used for this definition.

[0028] Alternatively or additionally, during the production of a three-dimensional workpiece, it can be performed to determine whether a region of the raw material powder layer is affected or substantially unaffected by particulate impurities. For example, when irradiating a previous raw material powder layer or another region of the same raw material powder layer, the development of splash particles and / or smoke plumes can be monitored by a suitable sensor device, and then the determination of whether a region of the raw material powder layer is affected or substantially unaffected by particulate impurities can be performed based on the output of the sensor device.

[0029] When producing a three-dimensional workpiece from multiple layers of raw material powder, the determination of whether a region of the raw material powder layer is affected or substantially unaffected by particulate impurities can be performed in such a way that unaffected regions and / or affected regions overlap in some or all layers. However, it is preferable to perform the determination of whether a region of the raw material powder layer is affected or substantially unaffected by particulate impurities by changing it layer by layer.

[0030] In a particularly preferred embodiment of the method for operating the radiation system, the determination of whether a region of the raw material powder layer is affected or substantially unaffected by particulate impurities is performed based on the geometry of the workpiece layer, which is generated by irradiating the raw material powder layer with electromagnetic radiation or particulate radiation. When determining whether a region of the raw material powder layer is unaffected or affected by particulate impurities, the geometry of the workpiece layer to be generated is taken into account, and the portions of the raw material powder layer that do not overlap with the workpiece layer and are therefore unirradiated can be ignored. On the other hand, because the influence of the workpiece geometry on the tendency to generate particulate impurities in certain portions of the raw material powder layer can be taken into account, the portions of the raw material powder layer that overlap with the workpiece layer can be examined more precisely to determine whether those portions are unaffected or affected by particulate impurities.

[0031] Alternatively or additionally, the determination of whether a region of the raw material powder layer is affected or substantially unaffected by particulate impurities can be performed based on the geometry of the workpiece layer, which was produced by irradiating a previous raw material powder layer with electromagnetic or particle radiation. By considering the geometry of the previously produced workpiece layer when determining whether a region of the raw material powder layer is unaffected or affected by particulate impurities, portions of the actual raw material powder layer that may be affected by embedded curing splatter particles deposited during the irradiation of the previous raw material powder layer can be identified and associated with the raw material powder layer regions affected by particulate impurities.

[0032] The determination of whether the region of the raw material powder layer is affected or substantially unaffected by particulate impurities is based on at least one of the following: the range of energy density values ​​that the irradiation system is intended to apply to the raw material powder layer, the type of gas forming the airflow guided through the raw material powder layer 11, the flow rate of the airflow guided through the raw material powder layer, the pressure present around the raw material powder layer, the thickness of the raw material powder layer, the material contained in the raw material powder layer, the angle at which the radiation beam impacts the raw material powder layer, the direction of movement of the radiation beam through the raw material powder layer, in particular the direction of movement through the raw material powder layer relative to the flow direction of the airflow, and the distance to the airflow inlet and / or the upstream edge of the raw material powder layer.

[0033] The tendency for particulate impurities to form when a raw powder layer is irradiated by an irradiation system increases with increasing energy density applied to the raw powder layer and with decreasing pressure in the processing chamber, and thus with decreasing pressure around the raw powder layer. Furthermore, when the raw powder layer is selectively irradiated, the type of gas supplied to the processing chamber to establish a controlled atmosphere and to remove particulate impurities affects the tendency for spatter particle formation. For example, a helium atmosphere in the processing chamber reduces the tendency for spatter particle formation compared to a nitrogen atmosphere. The thickness of the raw powder layer directly determines the length of the vapor capillaries formed during irradiation, and therefore directly determines the tendency for spatter particles to be emitted from the molten pool. Additionally, the thicker the raw powder layer, the higher the energy density that must be applied during irradiation. Therefore, it is advantageous to consider at least one of these processing parameters when determining whether the raw powder layer is unaffected or affected by particulate impurities.

[0034] The flow rate of the airflow guided through the raw material powder layer determines the distance that splashed particles are transported through the powder layer by being entrained by the airflow. The material of the raw material powder layer affects the formation tendency and size of the splashed particles. The angle at which the radiation beam impacts the raw material powder layer affects the formation tendency and emission direction of the splashed particles. The direction of movement of the radiation beam, especially its direction of movement relative to the flow direction of the airflow guided through the powder layer, affects the emission direction of the splashed particles and the direction in which they are transported through the powder layer by being entrained by the airflow. Therefore, considering these parameters also allows for a more precise determination of whether a region of the raw material powder layer is unaffected by particulate impurities or is affected by them.

[0035] When a raw material powder layer is simultaneously irradiated by multiple radiation beams, the area of ​​the raw material powder layer irradiated by another radiation beam around its irradiation location may be affected by particulate impurities generated due to the interaction between the other radiation beam and the raw material powder layer. In fact, this area of ​​the raw material powder layer may be affected by splashing particles and the plume of smoke generated when the other radiation beam irradiates the raw material powder layer. For example, an area of ​​the raw material powder layer positioned downstream of the irradiation location of another radiation beam relative to the flow direction of the airflow guided through the raw material powder layer may be affected by particulate impurities that interfere with the irradiation of this area by the radiation beam.

[0036] Therefore, based on the irradiation positions of multiple radiation beams relative to each other, it is possible to determine whether a region of the raw material powder layer is affected by particulate impurities or is substantially unaffected by particulate impurities. In particular, if it is determined that the region of the raw material powder layer is affected by particulate impurities generated due to the interaction of another radiation beam with the raw material powder layer, the energy density applied to the region of the raw material powder layer by the radiation beam can be increased.

[0037] It is conceivable that the increased energy density applied to the raw material powder layer in the region affected by particulate impurities remains constant throughout the affected region. However, the interference of particulate impurities on the region can vary throughout the region depending on their location within the raw material powder layer, the workpiece geometry, and the aforementioned processing parameters. Therefore, different parts of the region may be affected by particulate impurities to varying degrees. Therefore, preferably, when selectively irradiating the region of the raw material powder layer identified as being affected by particulate impurities, the energy density applied to the region of the raw material powder layer by the radiation beam is varied according to the degree of interference of the particulate impurities on that region.

[0038] For example, when a region of a raw material powder layer is irradiated by a radiation beam, a plume of light particulate impurities generated by the interaction of another radiation beam (or even the blocked radiation beam itself) with the raw material powder layer can shield and / or scatter the radiation beam irradiating the raw material powder layer near the other radiation beam. Therefore, when a region of the raw material powder layer (defined as being affected by particulate impurities generated by the other radiation beam) is selectively irradiated by the radiation beam, the energy density applied to that region by the radiation beam increases compared to the energy density applied to the raw material powder layer by the other radiation beam.

[0039] The degree to which a radiation beam is affected by a plume of smoke generated by another radiation beam varies depending on the location where the radiation beam impacts the generally conical plume. This is particularly true when normal gas flow parameters, given the amount and velocity of the gas, are applied, most effectively capturing particulate impurities without disturbing the top powder layer. For example, the shielding and / or scattering effects on the radiation beam will be more severe when it impacts the plume in the central region than when it impacts it in the tip region near the irradiation point of the other radiation beam or in the edge region of the plume away from the irradiation point of the other radiation beam. Therefore, the energy density applied by the radiation beam to the region of the feed powder layer (which is affected by the plume of smoke generated by the other radiation beam) can vary depending on the irradiation position of the radiation beam relative to the plume of smoke generated by the other radiation beam.

[0040] The central region of the smoke plume typically extends from a plane extending through the smoke plume at a distance of approximately 60 mm from the irradiation position of the first radiation beam to a plane extending through the smoke plume at a distance of approximately 400 mm from the irradiation position of the first radiation beam. However, the shape of the smoke plume and the location of its central region can vary specifically depending on the position and direction of movement of the other radiation beam relative to the flow direction and flow rate of the gas stream guided through the feed powder layer. Clearly, plume generation can also often depend on known influencing factors such as the material of the feed powder, the incident angle of the radiation beam, and the protective gas used.

[0041] When selectively irradiating regions of a raw material powder layer that are identified as being affected by particulate impurities, the energy density applied to the region of the raw material powder layer by the radiation beam can increase in discrete increments as the degree of interference of the particulate impurities on that region increases.

[0042] However, it is also conceivable that the energy density applied to the region of the raw material powder layer by the radiation beam would increase continuously as the degree of interference from particulate impurities in that region increases. Finally, it is conceivable that in some portions of that region, the energy density increases in discrete increments as the degree of interference from particulate impurities increases, while in other portions of that region, the energy density increases continuously as the degree of interference from particulate impurities increases. For example, the increase in energy density applied to the region of the raw material powder layer identified as being affected by particulate impurities could vary from +1% to +100%, particularly from +5% to +50%.

[0043] An irradiation system for producing three-dimensional workpieces by irradiating layers of raw material powder with electromagnetic or particle radiation includes a control device configured to subdivide the raw material powder layer, selectively irradiated with electromagnetic or particle radiation, into multiple regions based on the geometry of the corresponding layer of the workpiece to be produced. Furthermore, the control device is configured to receive, for at least one region, a determining input indicating whether the region is affected by particulate impurities or substantially unaffected by particulate impurities before selective irradiation with electromagnetic or particle radiation. The determination of whether a region of the selectively irradiated raw material powder layer is affected by particulate impurities or substantially unaffected by particulate impurities can be performed by means of a suitable determining device and / or can be accomplished by user input into the control device.

[0044] The control device is also configured to control the energy density on the region of the raw material powder layer to which the radiation beam is applied in such a way that when the region of the raw material powder layer is determined to be affected by particulate impurities, the energy density is higher than when the region of the raw material powder layer is determined to be substantially unaffected by particulate impurities.

[0045] The control device can be configured to control the energy density applied to the region of the raw material powder layer by appropriately adjusting at least one of the power, focal diameter, and focal shape of the radiation beam guided through the region of the raw material powder layer. Alternatively or additionally, the control device can be configured to control the energy density applied to the region of the raw material powder layer by appropriately adjusting at least one of the scanning speed and scanning pattern, according to which the radiation beam is guided through the region of the raw material powder layer.

[0046] The determining device can be configured to determine whether a region of the raw material powder layer is affected by or substantially unaffected by particulate impurities based on the flow direction of the airflow guided through the raw material powder layer and / or based on a splash trajectory determined based on the flow velocity of the airflow guided through the raw material powder layer, the gas flow distribution of the airflow guided through the raw material powder layer, and / or the particle weight of the particulate impurities.

[0047] The region of the raw material powder layer extending a predetermined distance from the upstream edge of the raw material powder layer along the flow direction of the airflow guided through the raw material powder layer and / or extending a predetermined distance from the upstream irradiation start position along the flow direction of the airflow guided through the raw material powder layer can be regarded as the region of the raw material powder layer that is substantially unaffected by particulate impurities.

[0048] The control device can be configured to subdivide a layer of raw material powder selectively irradiated with electromagnetic radiation or particle radiation into multiple regions before the start of production of the three-dimensional workpiece and / or during the production of the three-dimensional workpiece.

[0049] The determining device can be configured to determine, before the start of production of a three-dimensional workpiece (e.g., in the form of a simulation) and / or during the production of the three-dimensional workpiece, whether a region of the raw material powder layer is affected by particulate impurities or is substantially unaffected by particulate impurities.

[0050] The determining device can be configured to determine whether a region of the raw material powder layer is affected by particulate impurities or is substantially unaffected by particulate impurities based on the geometry of the workpiece layer produced by irradiating the raw material powder layer with electromagnetic radiation or particle radiation and / or based on the geometry of the workpiece layer produced by irradiating a previous raw material powder layer with electromagnetic radiation or particle radiation.

[0051] The determining device can be configured to determine whether a region of the raw material powder layer is affected by particulate impurities or is substantially unaffected by particulate impurities based on at least one of the following: the range of energy density values ​​that the irradiation system intends to apply to the raw material powder layer, the pressure present around the raw material powder layer, the type of gas forming the airflow guided through the raw material powder layer, the thickness of the raw material powder layer, the flow rate of the airflow guided through the raw material powder layer, the material contained in the raw material powder layer, the angle at which the radiation beam impacts the raw material powder layer, the direction of movement of the radiation beam through the raw material powder layer, particularly the direction of movement of the radiation beam through the raw material powder layer relative to the flow direction of the guided airflow, and the distance to the airflow inlet and / or the upstream edge of the raw material powder layer.

[0052] The determining device can be configured to determine whether a region of the raw material powder layer is affected by particulate impurities or is substantially unaffected by particulate impurities based on the irradiation positions of multiple radiation beams relative to each other.

[0053] When selectively irradiating regions of a raw material powder layer that are identified as being affected by particulate impurities, the control device can be configured to vary the energy density of the regions of the raw material powder layer that are subjected to the radiation beam according to the degree of interference of the particulate impurities with those regions.

[0054] When selectively irradiating a region of a raw material powder layer (which is determined to be affected by particulate impurities generated by another radiation beam) by a radiation beam, the control device can be configured to increase the energy density applied to that region by the radiation beam compared to the energy density applied to the raw material powder layer by the other radiation beam.

[0055] When selectively irradiating regions of a raw material powder layer identified as being affected by particulate impurities, the control device can be configured to increase the energy density applied to the region of the raw material powder layer by the radiation beam in discrete increments and / or continuously as the degree of interference of the particulate impurities on that region increases.

[0056] The equipment used to produce three-dimensional workpieces is equipped with the aforementioned irradiation system. Attached Figure Description

[0057] Preferred embodiments of the present invention will be described in more detail with reference to the accompanying schematic diagrams, in which:

[0058] Figure 1 An apparatus for producing three-dimensional workpieces by irradiating a layer of raw material powder with electromagnetic radiation or particle radiation is shown.

[0059] Figure 2 The effect of particulate impurities on different regions of a raw material powder layer is shown, which overflows as a gas flow is guided through the raw material powder layer from a gas inlet located in a region at the side edge of the raw material powder layer.

[0060] Figure 3 The effect of particulate impurities on different regions of a raw material powder layer is shown, which overflows as a gas flow is guided through the raw material powder layer from a gas inlet arranged in the central region of the raw material powder layer;

[0061] Figure 4 A raw material powder layer is shown being irradiated by multiple radiation beams, wherein one radiation beam is affected to varying degrees by particulate impurities generated by another radiation beam, the degree of which depends on the irradiation position of the first radiation beam relative to the irradiation position of the second radiation beam. Detailed Implementation

[0062] Figure 1 An apparatus 100 for producing three-dimensional workpieces via a layer-by-layer additive manufacturing process is shown. The apparatus 100 includes a carrier 102 and a powder application device 104 for applying raw material powder onto the carrier 102. The carrier 102 and the powder application device 104 are housed within a processing chamber 106, which is preferably sealable relative to the ambient atmosphere. The carrier 102 can be vertically displaced into a building cylinder 108 such that, as the workpiece 110 is built layer-by-layer with raw material powder on the carrier 102, the carrier 102 can move downwards as the height of the workpiece increases. The carrier 102 may include a heater and / or a cooler.

[0063] The device 100 also includes an irradiation system 10 for selectively irradiating the raw material powder layer 11 applied to the carrier 102 with electromagnetic radiation or particle radiation. Figure 1In the embodiment of the illustrated device 100, the irradiation system 10 includes two radiation beam sources 12a, 12b, each configured to emit a laser beam 14a, 14b. Optical units 16a, 16b are associated with each of the radiation beam sources 12a, 12b for guiding and processing the radiation beams 14a, 14b emitted by the radiation beam sources 12a, 12b. However, it is also conceivable that the irradiation system 10 may be equipped with more than two or only one radiation beam source and only one optical unit, and thus emit only a single radiation beam. A control device 18 is provided to control the operation of the irradiation system 10 and other components of the device 100 (e.g., powder application device 104).

[0064] A controlled gas atmosphere, preferably an inert gas atmosphere, is established within the processing chamber 106 by supplying a protective gas to the processing chamber 106 via the processing gas inlet 112. After the gas is guided through the processing chamber 106 and passes through the raw material powder layer 11 applied to the carrier 102, the gas is discharged from the processing chamber 106 via the processing gas outlet 114. The processing gas can be recirculated from the processing gas outlet 114 to the processing gas inlet 112, and can thereby be cooled or heated. The illustrated arrangement of the gas inlets 112 in the sidewalls of the processing chamber 106 is merely exemplary and not limiting. Obviously, any arrangement can be implemented that uses airflow in the processing chamber 106, particularly on the raw material powder layer 11, for example, on the floor or ceiling of the processing chamber 106. Multiple gas inlets 112 may also be present.

[0065] During operation of the equipment 100 for producing three-dimensional workpieces, a layer 11 of raw material powder is applied to a carrier 102 by a powder application device 104. To apply the raw material powder layer 11, the powder application device 104 is moved across the carrier 102 under the control of a control unit 18. Then, again under the control of the control unit 18, the raw material powder layer 11 is selectively irradiated with electromagnetic radiation or particle radiation by an irradiation device 10 according to the geometry of the corresponding layer of the workpiece 110 to be produced. The steps of applying the raw material powder layer 11 to the carrier 102 and selectively irradiating the raw material powder layer 11 with electromagnetic radiation or particle radiation according to the geometry of the corresponding layer of the workpiece 110 to be produced are repeated until the workpiece 110 achieves the desired shape and size.

[0066] The radiant energy introduced into the raw material powder by the radiation beams 14a and 14b impacting the raw material powder layer 11 causes the raw material powder to melt and / or sinter. Specifically, a molten pool of the raw material is generated in the area where the radiation beams 14a and 14b impact the raw material powder. During the melting of the raw material powder, welding fumes are generated, which form a plume 124 containing light particulate impurities, such as smoke particles, dispersed raw material powder particles, and soot particles. Although the majority of the light welding fume particles are discharged from the processing chamber 106 by being entrained by the airflow guided through the processing chamber 106, the plume 124 of light particulate impurities generated by the interaction of the radiation beams 14b may still undesirably shield and / or scatter the radiation beams 14a, which are guided through the plume 124 caused by the radiation beams 14b before impacting the raw material powder to be irradiated.

[0067] Furthermore, the evaporation of the raw material from the molten pool causes spatter particles 126 to be ejected from the molten pool. These spatter particles 126, ejected from the molten pool in molten form and subsequently solidified, are typically too heavy to be carried away by the airflow guided through the processing chamber 106. Therefore, these spatter particles deposit on the surface of the unirradiated raw material powder of the selectively irradiated raw material powder layer 11 or on the surface of the newly formed workpiece layer. If the spatter particles 126 are deposited in a portion of the raw material powder layer 11 that is still to be irradiated by either of the radiation beams 14a or 14b, these particulate impurities may have already affected the quality of the workpiece layer portion produced by the selective irradiation of said portion of the raw material powder layer 11.

[0068] However, the quality of the workpiece layer produced by selectively irradiating the raw material powder layer 11 may also be affected by particulate impurities generated during the irradiation of the previous raw material powder layer and covering / bonding the raw material powder layer 11. Cured spatter particles present on the surface of the raw material powder layer 11 and / or embedded in the raw material powder layer 11 during irradiation may cause defects and / or irregularities in the workpiece 110 to be produced.

[0069] The device 100 is equipped with multiple sensor devices 116, 118, and 120. Sensor devices 116 and 118 are adapted to monitor various processing parameters, such as the temperature of the gas atmosphere within the processing chamber 106, the temperature of the carrier 106, and radiation emitted from the molten pool in and / or the region surrounding the focal points of the radiation beams 14a and 14b. Sensor devices 116 and 118 may, for example, constitute components of a molten pool monitoring system and may include a pyrometer or a suitable camera adapted to detect infrared radiation at multiple locations on the layer of raw material powder and / or to monitor vapor capillaries, for example, for detecting capillary fluctuations. The sensed radiation is guided to sensor devices 116 and 118 via optical units 16a and 16b.

[0070] Sensor device 120 is adapted to detect the temperature of the raw material powder / workpiece layer during and after irradiation with electromagnetic radiation or particle radiation. Sensor device 120 may, for example, be a component of a melt pool monitoring system or a layer control system, and may include a suitable camera adapted to monitor the uniformity of the applied powder layer. Sensor device 120 may also be adapted to directly monitor the development of spatter particles 126 and / or smoke plumes 124 generated during the irradiation of the raw material powder layer 11. However, sensor device 120 may also be used to directly detect solidified spatter particles deposited on the surface of the raw material powder layer 11 before the application of the next raw material powder layer. When monitoring the raw material powder layer 11 by sensor device 120, the raw material powder layer may be observed from different angles and / or illuminated, and / or illuminated by light of different wavelengths via illumination device 122.

[0071] In another exemplary embodiment, at least one of the sensor devices 116, 118, and 120 may be a pyrometer device capable of detecting the temperature at a specific point within the processing chamber 106 (e.g., on the raw material powder layer), or the average temperature over a region within the processing chamber 106 (e.g., on the raw material powder layer). The device 100 may include additional sensor devices, such as those for measuring the temperature of the processing gas at the processing gas inlet 112 or another location, or for measuring the composition of the processing gas within the processing chamber 106. It should be understood that this example is not limiting, and the device 100 according to the invention may include only a few named sensors or all named sensors, and may include additional sensors.

[0072] When operating the irradiation system 10, before or during the production of the three-dimensional workpiece, the raw material powder layer 11, selectively irradiated with electromagnetic radiation or particle radiation, is subdivided into multiple regions according to the geometry of the corresponding layer of the workpiece to be produced. Furthermore, for each region, before selectively irradiating it with electromagnetic radiation or particle radiation, it is determined whether the region is affected by particulate impurities or is substantially unaffected by particulate impurities. The determination of whether a region of the raw material powder layer 11 is affected by particulate impurities or substantially unaffected by particulate impurities is performed by a determining device 20. The determining device 20 may be associated with or integrated with the control device 18.

[0073] For example, before production of the three-dimensional workpiece 110 begins, a determination of whether a region of the raw material powder layer 11 is affected by particulate impurities or is substantially unaffected by particulate impurities, performed by the determining device 20, can be based on a preferred computer-aided simulation. Alternatively or additionally, during production of the three-dimensional workpiece 110, the determining device 20 can perform the determination of whether a region of the raw material powder layer 11 is affected by particulate impurities or is substantially unaffected by particulate impurities based on the output of at least one of the sensor devices 116, 118, 120.

[0074] For example, in order to determine whether a specific region of the raw material powder layer 11 is affected by particulate impurities or is substantially unaffected by particulate impurities, the development of splash particles 126 and / or smoke plumes 124 can be monitored by sensor device 120 with the aid of illumination device 122 when irradiating a previous raw material powder layer or a different region of (the same) raw material powder layer 11. Then, the determination of whether a region of the raw material powder layer 11 is affected by particulate impurities or is substantially unaffected by particulate impurities can be performed based on the output of sensor device 120.

[0075] When radiation beams 14a and 14b irradiate the raw material powder layer region (which is located upstream of the raw material powder layer 11 relative to the flow direction F of the airflow guided through the raw material powder layer 11, i.e. near the gas inlet 112 of the processing chamber 106 and far from the gas outlet 114 of the processing chamber 106), the raw material powder layer region (which is located downstream of the raw material powder layer 11 relative to the flow direction F of the airflow guided through the raw material powder layer 11, i.e. far from the gas inlet 112 of the processing chamber 106 and near the gas outlet 114 of the processing chamber 106) is generally affected by the plume 124 of splatter particles and light particulate impurities emitted from the molten pool.

[0076] Figure 2A top view of the raw material powder layer 11 is shown, which is overflowed by an airflow that is directed through the processing chamber 106 and passes through the raw material powder layer 11 in the flow direction F from a gas inlet 112 arranged in the side wall of the processing chamber 106 and thus in the area of ​​the side edge of the raw material powder layer 11. Figure 2 The dashed line in the figure represents the cross-section of the workpiece layer 22 produced by irradiating the previous raw material powder layer below the actual raw material powder layer 11, and can also be understood as a representation of the cross-section of the workpiece layer 22 to be produced. Figure 3 The raw material powder layer 11 shown is Figure 2 The only difference between the raw material powder layer 11 and the raw material powder layer 11 is that the gas inlet 112 for guiding gas into the processing chamber 106 and through the raw material powder layer 11 is not arranged in the area of ​​the side edge of the raw material powder layer 11, but in the central area of ​​the raw material powder layer 11. Figure 3 The gas outlet (not shown) is arranged correspondingly around the raw material powder layer 11.

[0077] Figure 2 and Figure 3 Each of the raw material powder layers 11 shown includes a first region 24 that is substantially unaffected by particulate impurities, a second region 26 that is moderately affected by particulate impurities, and a third region 28 that is severely affected by particulate impurities. According to... Figure 2 and Figure 3 In the exemplary raw material powder layer 11, the particulate impurities affecting the second region 26 and the third region 28 of the raw material powder layer 11 are generated when the previous raw material powder layer is irradiated, and the second region 26 and the third region 28 are now covered and / or embedded with the raw material powder of the raw material powder layer 11.

[0078] However, Figure 2 and Figure 3 It is clearly shown that the raw material powder layer regions 26 and 28, located in the downstream region of the raw material powder layer 11, are more severely affected by particulate impurities than the raw material powder layer region 24, located in the upstream region of the raw material powder layer 11. Therefore, in determining whether a region of the raw material powder layer 11 is affected by particulate impurities or is substantially unaffected by particulate impurities, the determining device 20 takes into account the flow direction F of the airflow guided through the processing chamber 106 and across the raw material powder layer 11, in order to establish the required atmosphere within the processing chamber 106 and remove particulate impurities from the processing chamber 106.

[0079] For example, the determining device 20 may consider a region extending a predetermined distance from the upstream edge 30 of the raw material powder layer 11 along the flow direction F of the airflow guided through the raw material powder layer 11 as a region of the raw material powder layer 11 that is substantially unaffected by particulate impurities. Alternatively or additionally, the determining device 20 may consider a region extending a predetermined distance from the upstream irradiation start position 32 of the raw material powder layer 11 along the flow direction F of the airflow guided through the raw material powder layer 11 as a region of the raw material powder layer that is substantially unaffected by particulate impurities. The predetermined distance may be determined by the determining device 20 based on an estimate of the "purification effect" (describing the efficiency of the airflow in capturing and removing particulate impurities) of the airflow guided through the processing chamber 106.

[0080] When producing a three-dimensional workpiece 110 from multiple layers of raw material powder, the determining device 20 can determine whether a region of the raw material powder layer is affected by particulate impurities or is substantially unaffected by particulate impurities in such a way that unaffected regions and / or affected regions overlap in some or all layers. However, preferably, the determination of whether a region of the raw material powder layer is affected by particulate impurities or is substantially unaffected by particulate impurities is performed in a layer-by-layer manner.

[0081] Specifically, the determining device 122 can determine whether a region of the raw material powder layer 11 is affected by particulate impurities or is substantially unaffected by particulate impurities based on the geometry of the workpiece layer 22, which is generated by irradiating the raw material powder layer 11 with electromagnetic radiation or particulate radiation. Alternatively or additionally, the determining device 122 can determine whether a region of the raw material powder layer 11 is affected by particulate impurities or is substantially unaffected by particulate impurities based on the geometry of the workpiece layer, which is generated by irradiating a previous raw material powder layer.

[0082] Furthermore, when determining whether a region of the raw material powder layer 11 is affected by particulate impurities or is substantially unaffected by particulate impurities, the determining device 20 may consider at least one of the following: the range of energy density values ​​that the irradiation system 10 intends to apply to the raw material powder layer 11, the type of gas forming the airflow guided through the raw material powder layer 11, the flow rate of the airflow guided through the raw material powder layer 11, the pressure present around the raw material powder layer 11, the thickness of the raw material powder layer 11, the material contained in the raw material powder layer, the angle at which the radiation beams 14a and 14b strike the raw material powder layer 11, and the direction of movement of the radiation beams 14a and 14b through the raw material powder layer 11, particularly the direction of movement through the raw material powder layer relative to the flow direction F of the airflow.

[0083] exist Figure 2 and Figure 3In the exemplary embodiment of the raw material powder layer 11 shown, the determining device 20 ignores the region arranged directly adjacent to the gas inlet 112 when considering the geometry of the workpiece layer 22 generated in the previous powder layer. For region I of the raw material powder layer 11, which extends a predetermined distance from the upstream edge 30 of the raw material powder layer 11 along the flow direction F of the airflow and also extends a predetermined distance from the upstream irradiation start position 32 along the flow direction F of the airflow, the determining device 20 determines that region I is substantially unaffected by particulate impurities.

[0084] The determining device 20 determines that region II, located downstream of the unaffected region I relative to the airflow direction F, constitutes a region of the raw material powder layer 11 moderately affected by particulate impurities. Finally, the determining device 20 determines that region III, located downstream of the moderately affected region II relative to the airflow direction F, constitutes a region of the raw material powder layer 11 severely affected by particulate impurities. Figure 2 and Figure 3 This indicates that regions II and III identified by the determining device 20 do not completely coincide with regions 26 and 28, but they overlap with regions 26 and 28 to a considerable extent.

[0085] Figure 4 A layer of raw material powder 11 irradiated by multiple radiation beams 14a, 14b is shown. Figure 4 The dashed lines in the diagram represent the irradiated portions 34 and 36, respectively, irradiated by radiation beams 14a and 14b. The overlapping portion 38 can be irradiated by both radiation beams 14a and 14b. In the first region 24, Figure 4 The raw material powder layer 11 is substantially unaffected by particulate impurities generated during the irradiation of the previous raw material powder layer. In the second region 26, the raw material powder layer 11 is affected by particulate impurities generated during the irradiation of the previous raw material powder layer and now embedded in the raw material powder layer 11. In the third region 28, the raw material powder layer 11 is affected by particulate impurities (especially spatter particles) generated during the irradiation of the previous raw material powder layer and during the irradiation of the actual raw material powder layer 11.

[0086] Furthermore, the radiation beam 14b generates a substantially conical smoke plume 124 upon impacting the raw material powder layer 11. When the radiation beam 14a is guided through the smoke plume 124 before impacting the raw material powder to be irradiated, the smoke plume 124 may undesirably shield and / or scatter the radiation beam 14a. The degree to which the radiation beam 14a is affected by the smoke plume 124 generated by the radiation beam 14b varies depending on the location where the radiation beam 14a impacts the substantially conical smoke plume 124. The shielding and / or scattering effect on the radiation beam 14a is more severe when it impacts the smoke plume 124 in the central region than when it impacts the smoke plume 124 in the tip region near the irradiation position of the radiation beam 14b or in the edge region of the smoke plume 124 away from the irradiation position of the radiation beam 14b.

[0087] Therefore, the determining device 20 also performs the determination of whether a region of the raw material powder layer 11 is affected by particulate impurities or is substantially unaffected by particulate impurities based on the irradiation positions of the plurality of radiation beams 14a, 14b relative to each other. Figure 4 The image shows different irradiation positions 14aa to 14ag of the radiation beam 14a relative to the irradiation position 14ba of the radiation beam 14b.

[0088] When selectively irradiating the raw material powder layer 11 with electromagnetic radiation or particle radiation, the energy density applied to the region of the raw material powder layer 11 by the radiation beams 14a and 14b is controlled by the control device 18 in such a way that the energy density is higher when it is determined that the region of the raw material powder layer 11 is affected by particulate impurities than when it is determined that the region of the raw material powder layer 11 is substantially unaffected by particulate impurities. Because the energy density applied to the region of the raw material powder layer increases when the region is affected by particulate impurities, when the radiation beams 14a and 14b are guided through the region of the raw material powder layer 11, not only are the raw material powder particles melted, but also the solidified spatter particles deposited on the surface of the raw material powder layer 11 or embedded in the raw material powder layer 11 are melted. Furthermore, the shielding and / or scattering effects caused by the smoke plume 124 of light particulate impurities can be compensated.

[0089] The energy density applied to the region of the raw material powder layer 11 can be controlled by appropriately adjusting at least one of the power, focal diameter, and focal shape of the radiation beams 14a and 14b guided through the raw material powder layer 11. Alternatively or additionally, the energy density applied to the region of the raw material powder layer 11 can be controlled by appropriately adjusting at least one of the scanning speed and scanning pattern, according to which the radiation beams 14a and 14b are guided through the raw material powder layer 11.

[0090] Furthermore, when selectively irradiating the areas of the raw material powder layer 11 that are identified as being affected by particulate impurities, the energy density on the areas of the raw material powder layer 11 applied by the radiation beams 14a and 14b varies under the control of the control device 18, depending on the degree of interference of the particulate impurities on the area.

[0091] exist Figure 2 and Figure 3 In the example, in region I, which is essentially unaffected by particulate impurities, the energy density applied to region I does not need to be increased when irradiating this region, and is therefore set to 0%. In region II, which is moderately affected by particulate impurities, the increase in energy density applied to region II is set to +5%. Finally, in region III, which is severely affected by particulate impurities, the increase in energy density applied to region III is set to +15%.

[0092] exist Figure 4 In the example, when setting the energy density applied by radiation beams 14a and 14b, the effects of particulate impurities generated during the irradiation of the previous raw material powder layer, the effects of particulate impurities generated during the irradiation of the actual raw material powder layer 11, and the effects of the smoke plume 124 are taken into account, as shown in the table below.

[0093]

[0094] As can be clearly seen from the table, the energy density on the region of the raw material powder layer 11 applied by the radiation beam 14a (which is affected by the smoke plume 124 generated by the radiation beam 14b) varies depending on the irradiation position of the radiation beam 14a relative to the smoke plume 124 generated by the radiation beam 14b. Furthermore, when the region of the raw material powder layer 11 (which is determined to be affected by particulate impurities generated by the radiation beam 14b) is selectively irradiated by the radiation beam 14a, the energy density applied to that region by the radiation beam 14a increases compared to the energy density applied to the raw material powder layer 11 by the radiation beam 14b.

[0095] In the table above, the energy density applied to the region of the raw material powder layer 11 by radiation beams 14a and 14b increases in discrete increments as the degree of interference from particulate impurities in that region increases. However, it is also conceivable that the energy density applied to the region of the raw material powder layer 11 by radiation beams 14a and 14b increases in a continuous manner as the degree of interference from particulate impurities in that region increases.

Claims

1. Method of operating an irradiation system (10) for irradiating layers of a feedstock powder with electromagnetic or particle radiation to produce a three-dimensional workpiece (110), the method comprising the steps of: - subdividing a layer (11) of a feedstock powder to be selectively irradiated with electromagnetic or particle radiation into a plurality of regions in accordance with a geometry of a corresponding layer of the three-dimensional workpiece (110) to be produced; - for at least one region, determining whether the region is affected by or substantially not affected by particulate impurities prior to selectively irradiating the region with electromagnetic or particle radiation; and - controlling an energy density applied to the region of the layer (11) of the feedstock powder by a radiation beam (14a, 14b) in such a way that the energy density is higher in case the region of the layer (11) of the feedstock powder is determined to be affected by particulate impurities than in case the region of the layer (11) of the feedstock powder is determined to be substantially not affected by particulate impurities when selectively irradiating the region of the layer (11) of the feedstock powder with electromagnetic or particle radiation.

2. The method according to claim 1, wherein controlling the energy density applied to the region of the layer (11) of the feedstock powder by appropriately adjusting at least one of a power, a focal spot diameter and a focal spot shape of the radiation beam (14a, 14b) directed through the region of the layer (11) of the feedstock powder and / or at least one of a scanning speed and a scanning pattern according to which the radiation beam (14a, 14b) is directed through the region of the layer (11) of the feedstock powder, wherein the energy density is controlled by appropriately adjusting the scanning pattern in such a way that a distance between adjacent scanning vectors defining the scanning pattern is reduced.

3. The method according to claim 1, wherein performing the determination whether a region of the layer (11) of the feedstock powder is affected by or substantially not affected by particulate impurities in accordance with a flow direction (F) of a gas flow directed through the layer (11) of the feedstock powder and / or in accordance with a spatter trajectory determined based on a flow velocity of a gas flow directed through the layer (11) of the feedstock powder and / or a gas flow distribution of the gas flow directed through the layer (11) of the feedstock powder and / or a particle weight of the particulate impurities.

4. The method according to claim 3, wherein a region of the layer (11) of the feedstock powder extending a predetermined distance from an upstream edge (30) of the layer (11) of the feedstock powder and / or a predetermined distance from an upstream irradiation start position (32) in the flow direction (F) of the gas flow directed through the layer (11) of the feedstock powder is considered to be a region of the layer (11) of the feedstock powder substantially not affected by particulate impurities.

5. The method according to claim 1, wherein: - the layer of raw material powder (11) is selectively irradiated with electromagnetic or particle radiation before starting the production of the three-dimensional workpiece (110) and / or during the production of the three-dimensional workpiece (110) is subdivided into a plurality of regions; and / or - the determination of regions of the layer of raw material powder (11) that are affected or substantially not affected by particle contamination is performed before starting the production of the three-dimensional workpiece (110) and / or during the production of the three-dimensional workpiece (110).

6. The method according to claim 1, wherein The determination of regions of the layer of raw material powder (11) that are affected or substantially not affected by particle contamination is performed according to the geometry of the workpiece layer resulting from the irradiation of the layer of raw material powder (11) with electromagnetic or particle radiation and / or according to the geometry of the workpiece layer resulting from the irradiation of a preceding layer of raw material powder (11) with electromagnetic or particle radiation.

7. The method according to claim 1, wherein The determination of regions of the layer of raw material powder (11) that are affected or substantially not affected by particle contamination is performed according to at least one of the following: a range of values of the energy density that the irradiation system (10) aims to apply to the layer of raw material powder (11), a pressure existing around the layer of raw material powder (11), a type of gas forming a gas stream directed through the layer of raw material powder (11), a thickness of the layer of raw material powder (11), a flow rate of the gas stream directed through the layer of raw material powder (11), a material contained in the layer of raw material powder (11), an angle at which a radiation beam (14a, 14b) hits the layer of raw material powder (11), a direction of movement of a radiation beam (14a, 14b) through the layer of raw material powder (11), and a distance from a gas stream inlet and / or an upstream edge of the layer of raw material powder (11).

8. The method according to claim 1, wherein The determination of regions of the layer of raw material powder (11) that are affected or substantially not affected by particle contamination is performed according to irradiation positions (14ba, 14aa to 14ag) of a plurality of radiation beams (14a, 14b) relative to each other.

9. The method according to claim 1, wherein, When selectively irradiating a region of the layer of raw material powder (11) that is determined to be affected by particle contamination, the energy density applied to the region of the layer of raw material powder (11) by a radiation beam (14a, 14b) is varied according to the degree of disturbance of the region by particle contamination.

10. The method according to claim 1, wherein When selectively irradiating a region of the layer of raw material powder (11) that is determined to be affected by particle contamination resulting from another radiation beam (14a, 14b) by a radiation beam (14a, 14b), the energy density applied to the region by the radiation beam (14a, 14b) is increased compared to the energy density applied to the layer of raw material powder (11) by the other radiation beam (14a, 14b).

11. The method according to claim 1, wherein, The energy density imparted by the radiation beam (14a, 14b) on the region of the layer of feedstock powder (11) is increased in discrete increments or continuously with increasing degree of interference of the particulate impurities with the region, or in some portions of the region, the energy density imparted by the radiation beam (14a, 14b) on some portions of the region of the layer of feedstock powder (11) is increased in discrete increments with increasing degree of interference of the particulate impurities with the region, while in other portions of the region, the energy density imparted by the radiation beam (14a, 14b) on other portions of the region of the layer of feedstock powder (11) is increased continuously with increasing degree of interference of the particulate impurities with the region, when the region of the layer of feedstock powder (11) is selectively irradiated with electromagnetic or particle radiation.

12. The method of claim 7, wherein The direction of movement is the direction of movement of the radiation beam (14a, 14b) through the layer of feedstock powder relative to the flow direction (F) of the directed gas flow.

13. Irradiation system (10) for irradiating a layer of feedstock powder with electromagnetic or particle radiation to produce a three-dimensional workpiece (110), the irradiation system (10) comprising a control device (18) configured to: - subdivide a layer of feedstock powder (11) to be selectively irradiated with electromagnetic or particle radiation into a plurality of regions according to the geometry of the corresponding layer of the three-dimensional workpiece (110) to be produced; - for at least one region, receive a determination input indicating that the region is affected by particulate impurities or substantially not affected by particulate impurities, before selectively irradiating the region with electromagnetic or particle radiation; and - when selectively irradiating the region of the layer of feedstock powder (11) with electromagnetic or particle radiation, control the energy density imparted by the radiation beam (14a, 14b) on the region of the layer of feedstock powder (11) in such a way that the energy density is higher in the case where the region of the layer of feedstock powder (11) is determined to be affected by particulate impurities than in the case where the region of the layer of feedstock powder (11) is determined to be substantially not affected by particulate impurities.

14. The irradiation system (10) of claim 13, wherein The control device (18) is configured to control the energy density imparted on the region of the layer of feedstock powder (11) by appropriately adjusting at least one of the power, the focal spot diameter and the focal spot shape of the radiation beam (14a, 14b) directed through the region of the layer of feedstock powder (11) and / or at least one of the scanning speed and the scanning pattern according to which the radiation beam (14a, 14b) is directed through the region of the layer of feedstock powder (11), wherein the appropriate adjustment of the scanning pattern is achieved in such a way that the distance between adjacent scanning vectors defining the scanning pattern is reduced.

15. The irradiation system (10) according to claim 13, the irradiation system (10) comprising a determination device (20), - wherein, the determination device (20) is configured to determine the areas of the raw material powder layer (11) that are affected by or substantially not affected by particulate impurities depending on a flow direction (F) of a gas stream that is directed through the raw material powder layer (11) and / or depending on a spatter trajectory that is determined based on a flow velocity of the gas stream that is directed through the raw material powder layer (11) and / or a gas flow distribution of the gas stream that is directed through the raw material powder layer (11) and / or a particle weight of the particulate impurities; and / or - wherein an area of the raw material powder layer (11) that extends a predetermined distance from an upstream edge (30) of the raw material powder layer (11) along a flow direction (F) of a gas stream that is directed through the raw material powder layer (11) and / or a predetermined distance from an upstream irradiation start position (P) along a flow direction (F) of a gas stream that is directed through the raw material powder layer (11) is considered to be an area of the raw material powder layer (11) that is substantially not affected by particulate impurities; and / or - wherein the control device (18) is configured to subdivide the raw material powder layer (11) that is selectively irradiated with electromagnetic radiation or particle radiation into a plurality of areas before starting production of the three-dimensional workpiece (110) and / or during production of the three-dimensional workpiece (110); and / or - wherein the determination device (20) is configured to determine the areas of the raw material powder layer (11) that are affected by or substantially not affected by particulate impurities before starting production of the three-dimensional workpiece (110) and / or during production of the three-dimensional workpiece (110); and / or - wherein the determination device (20) is configured to determine the areas of the raw material powder layer (11) that are affected by or substantially not affected by particulate impurities depending on a geometry of a workpiece layer that is generated by irradiating the raw material powder layer (11) with electromagnetic radiation or particle radiation and / or depending on a geometry of a workpiece layer that is generated by irradiating a preceding raw material powder layer (11) with electromagnetic radiation or particle radiation; and / or - wherein the determining device (20) is configured to determine that a region of the layer of raw material powder (11) is affected or substantially not affected by particulate impurities depending on at least one of the following: a range of values of the energy density intended to be applied by the irradiation system (10) to the layer of raw material powder (11), a pressure present around the layer of raw material powder (11), a type of gas forming the gas flow directed through the layer of raw material powder (11), a thickness of the layer of raw material powder (11), a flow rate of the gas flow directed through the layer of raw material powder (11), a material contained in the layer of raw material powder (11), an angle at which a radiation beam (14a, 14b) hits the layer of raw material powder (11), a direction of movement of a radiation beam (14a, 14b) through the layer of raw material powder (11), and a distance from a gas flow inlet and / or an upstream edge of the layer of raw material powder (11); and / or - wherein the determining device (20) is configured to determine that a region of the layer of raw material powder (11) is affected or substantially not affected by particulate impurities depending on irradiation positions (14ba, 14aa to 14ag) of a plurality of radiation beams (14a, 14b) relative to each other.

16. The irradiation system (10) according to claim 13, - wherein, when selectively irradiating a region of the layer of raw material powder (11) determined to be affected by particulate impurities, the control device (18) is configured to vary the energy density applied by a radiation beam (14a, 14b) to the region of the layer of raw material powder (11) depending on a degree of disturbance of the region by particulate impurities; and / or - wherein, in when selectively irradiating a region of the layer of raw material powder (11) determined to be affected by particulate impurities produced by another radiation beam (14a, 14b), the control device (18) is configured to increase the energy density applied by a radiation beam (14a, 14b) to the region compared to the energy density applied by the other radiation beam (14a, 14b) to the layer of raw material powder (11); and / or - wherein, when said control device (18) is configured to selectively irradiate the areas of the layer of feedstock powder (11) identified as affected by particle impurities, it is configured to increase, with increasing degree of interference of the particle impurities with said areas, the energy density imparted by the radiation beam (14a, 14b) on said areas of the layer of feedstock powder (11) in discrete increments or continuously, or, in some portions of said areas, to increase, with increasing degree of interference of the particle impurities with said areas, the energy density imparted by the radiation beam (14a, 14b) on some portions of said areas of the layer of feedstock powder (11) in discrete increments, while, in other portions of said areas, to increase, with increasing degree of interference of the particle impurities with said areas, the energy density imparted by the radiation beam (14a, 14b) on other portions of said areas of the layer of feedstock powder (11) continuously.

17. The irradiation system (10) according to claim 15, wherein said direction of movement is the direction of movement of the radiation beam (14a, 14b) through the layer of feedstock powder with respect to the flow direction (F) of the directed gas flow.

18. Apparatus (100) for producing a three-dimensional workpiece (110), equipped with an irradiation system (10) according to claim 13.

Images