Process chamber for additive manufacturing equipment and method for operating the process chamber

Abstract

A process chamber housing (1) for an additive manufacturing apparatus, the process chamber having a bottom (9), a ceiling (10), and side walls (11, 12, 13) that together enclose a volume (51) of the process chamber (5), an inert gas inlet (6) at a front wall (11) of the side walls (11, 12, 13) configured to provide an inert gas to the process chamber (5), and an inert gas outlet (7) at a rear wall (12) of the side walls (11, 12, 13) configured to discharge the inert gas from the process chamber (5), provides improved beam quality if the inert gas inlet (6) and the inert gas outlet (7) are arranged on opposite sides of an opening (94) and face each other, thereby generating an inert gas flow (2) in a main flow direction (2) from the inert gas inlet (6) across the opening to the inert gas outlet (7).

Description

[Technical Field]

[0001] The present invention relates to additive manufacturing by powder bed fusion bonding. In particular, the present invention relates to a process chamber housing for an additive manufacturing apparatus. The process chamber housing has a process chamber having a bottom, ceiling, and side walls that together enclose the volume of the process chamber. An inert gas can be supplied into the process chamber through an inert gas inlet in one of the side walls, for example, the front side wall, and an inert gas outlet in one of the side walls, for example, the rear side wall, is provided for releasing the inert gas from the process chamber.

[0002] Description of related technologies Additive manufacturing is an increasingly important method for producing three-dimensional workpieces. While there are various additive manufacturing processes, this specification focuses on methods and apparatus for bonding powder particles, for example, by selectively heating powder particles on the upper surface of a powder bed, to cause some of the particles to adhere to one another. Powder particles are bonded to each other by sintering, fusion bonding, and / or welding (hereinafter collectively, "fusion bonding"). The heat for these processes is typically supplied by focused radiation, such as an electron beam or laser beam. These beams selectively heat the upper portion of the powder bed, thereby causing the upper layer particles to adhere to the particles in the previously formed layer. This process is generally called a powder bed fusion bonding process, or simply a powder fusion bonding process. In this specification, different types of radiation are not distinguished and are simply referred to as "beams."

[0003] Recent apparatuses for powder bed fusion have a housing with a process chamber. The process chamber has a support opening for accommodating a movable support. First, a thin layer of powder is applied to the support. This is mainly done by a recoater (see, for example, International Publication 2018 / 156264, International Publication 2017 / 143145, European Patent Application Publication 1234625, and German Patent Invention 102006056422). Once the layer is beam-treated, a subsequent layer of powder is applied, and this powder layer is then selectively fused again. This process is repeated until the additive manufacturing of the workpiece is complete. Further processing of the workpiece, such as grinding, cutting, or milling, may still be required.

[0004] For example, as taught in European Patent No. 3321003, the process chamber is preferably filled with an inert gas. During the additive manufacturing process, the inert gas flows from the gas inlet, over the bottom surface, and then over the upper layer of powder on the support to the gas outlet. European Patent No. 3321003 aims to form a substantially layered flow of the inert gas, thereby removing fumes, smoke, or other by-products (hereinafter collectively referred to as "smoke") from the melt bonding process. For this purpose, the inlet opening is formed from a porous material, thereby releasing a substantially uniform flow of the inert gas through the process chamber. The selection of inert gases is described in International Publication Nos. 2012 / 3828, 2020 / 064147, 2020 / 064148, or 2020 / 126086, specifically proposing argon (Ar) or nitrogen (N2) atmospheres with an oxygen concentration of less than 1000 ppm (parts per million). The addition of helium (He) to the inert gas atmosphere has also been proposed to enable high laser scanning speeds.

[0005] Early powder bed fusion processes suffered from the problem of being time-consuming, and many attempts have been made to shorten manufacturing time by, for example, using multiple beam sources simultaneously, thereby reducing the costs associated with a certain amount of additively manufactured workpieces. The difficulty with this approach is that, without significantly compromising the quality of the workpiece, the second beam does not fuse any part of the powder bed while a smoke column resulting from the operation of the first beam is located between the second beam source and the corresponding part of the powder bed. Such smoke columns appear to deform, absorb, and scatter the beam, and thus many concepts have been developed to avoid fusion of parts of the powder bed that are shadowed by smoke columns resulting from the scanning of the powder bed by other beams (see, for example, International Publication 2016 / 075026 or International Publication 2020 / 178216).

[0006] Summary of the Invention The problem to be solved by this invention is to improve the powder bed process.

[0007] The solution to this problem is described in the independent claim. The dependent claims relate to further improvements of the present invention.

[0008] The process chamber housing has a process chamber comprising a bottom, a ceiling, and side walls. The bottom, ceiling, and side walls together enclose the volume of the process chamber. In a preferred embodiment, at least one inert gas inlet is provided on the front side wall of the side wall and is configured to supply inert gas into the volume of the process chamber. At least a portion of the inert gas supplied into the volume can be removed through at least one inert gas outlet on the rear side wall of the side wall, and thus the inert gas outlet is configured to release the inert gas from the process chamber. Alternatively or additionally, the gas inlet and / or gas outlet may be provided on the ceiling, bottom, different side walls or the same side wall. The gas inlet and gas outlet may preferably be located on opposite sides of the process chamber.

[0009] The bottom surface may have an opening. The opening may be defined by opening walls. Preferably, vertically movable supports for supporting the powder bed, and therefore the three-dimensional (3D) object produced by selective powder bed fusion bonding, may be located between the opening walls. As is already apparent, the supports are preferably movably supported within the opening. For example, the supports may be further retracted into the opening (i.e., lowered, assuming a horizontal support surface) before adding a new powder layer to the powder bed.

[0010] The opening wall may be a linear bearing, and / or a linear bearing may be provided, that restricts movement to at least substantially perpendicular directions with respect to the edge formed by the transition between the bottom surface and the opening wall. "At least substantially perpendicular" means preferably perpendicular, but allowing for small deviations, e.g., deviations smaller than 1°, 2.5°, 5°, and / or 10°. The opening wall may surround a space, e.g., a box or cylinder, which can accommodate an already fused portion of the powder bed. The opening wall may be configured to be removable from the process chamber housing, allowing for easy replacement of the opening wall with a set of empty walls after the workpiece has been manufactured.

[0011] Preferably, the inert gas inlet and inert gas outlet are located on opposite sides of the opening and face each other. This makes it possible to provide a main inert gas flow in the main flow direction by injecting the inert gas from the (first) inert gas inlet while removing the inert gas from the volume through the (first) inert gas outlet, or in other words, by providing a pressure gradient from the inert gas inlet to the inert gas outlet. This main inert gas flow is preferably at least substantially parallel to the bottom surface and / or the upright surface of an optional support. The main inert gas flow may include an upward or downward component. In a preferred example, the direction of the main inert gas flow has a non-disappearing component parallel to the bottom surface and / or support. This non-disappearing component provides a direction in which the smoke column generated when the beam scans the powder bed is inclined relative to the vertical.

[0012] In a preferred example, the gas inlet is connected to an inert gas source that provides an inert gas containing He. The inert gas source is preferably configured to supply an inert gas containing at least helium (He) and one of other noble gases (i.e., at least one of neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), radon (Rn)) and / or nitrogen (N2). The inert gas source is configured to supply the inert gas containing He from the inert gas source into the volume of the process chamber. Particularly preferably, the inert gas source supplies a gas containing He and / or Ne in at least one percentage of 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 98%, 99%, where the percentage is in relation to the amount of moles of He and / or Ne relative to the total amount of moles of gas.

[0013] Unexpectedly, by replacing Ar or N2 with He and / or Ne, it was found that when the smoke generated by the first beam emitted by the first beam source is located between the beam outlet of the second beam source and the portion of the powder bed to be melted, the portion of the powder bed can be melted by the second beam emitted by the second beam source. Thus, in one embodiment, the present invention includes the step of melting a powder bed using at least two beams, while at least one second beam is controlled to melt a portion of the powder bed that is covered by a smoke column resulting from the melting of another portion of the powder bed by another beam (at least one first beam), in which case the smoke column is removed from the process chamber by a main inert gas flow, in which case it contains at least 20% He and / or Ne and / or 1.4 kg / m³ 3 1.2 kg / m 3 , 1 kg / m 3 , 0.6 kg / m 3 , 0.4 kg / m 3 , and 0.2 kg / m 3A main inert gas flow is generated by an inert gas having a density less than at least one of the following densities. The density is preferably based on normal conditions (0°C, 10¹³ hPa), but may be based on the actual conditions in the process chamber. In other words, at least one second beam source operates downstream of the beam spot of another beam source, in this case downstream with respect to the direction of the main inert gas flow above the powder bed. Covered means that a smoke column is present within the beam path of at least one second beam. As already mentioned, the beam source is preferably, but not limited to, a laser beam source. The use of the terms “laser beam” or “laser beam source” herein should be understood as preferred examples of “beam” or “beam source”. When in operation, the beam source may be swirled to scan the location on the powder bed to be melted. For example, a mirror swirled to project a laser beam onto the aforementioned location on the powder bed can be considered a beam source even if the beam is not generated by the mirror itself. In such applications, the location from which the beam is directed towards a single point on the powder bed is important, while the type of beam or beam generator is not.

[0014] Unlike all teachings of the prior art, by replacing at least a portion of Ar and / or N2 with He and / or Ne, it becomes possible to manipulate the smoke columns generated by scanning a portion of the powder bed with a first beam. Furthermore, studies have shown that the smoke within these smoke columns has a relatively low impact on the quality of the molten regions that are molten by penetrating smoke columns generated by another beam. As is evident from these observations, the density changes within the heat-induced smoke columns result in laser beam distortion, which in turn leads to defocusing and / or changes in the beam profile and / or changes in the beam intensity distribution across the beam profile, where the beam should be well focused. The decrease in density of He and / or Ne, combined with the increased thermal conductivity of He and / or Ne, reduces the density gradient between the high-temperature and low-temperature portions of the inert gas flow, thereby reducing the effects of defocusing. The advantageous effect of reducing laser beam distortion due to thermal non-uniformity in the inert gas flow can be further enhanced by reducing the amount of gas in the volume, i.e., by operating the process chamber at a pressure lower than the ambient pressure. By significantly reducing the pressure, it is also possible to use Ar and / or N2 as the inert gas (or simply use air), i.e., to omit He and / or Ne. A further advantage of reducing the pressure (i.e., reducing the amount of gas molecules in the volume) is that the flow velocity of the inert gas flow can be increased without moving (blowing away) the powder particles that have been pre-deposited in the powder bed by the inert gas flow.

[0015] Particularly preferably, the inert gas has a thermal conductivity of at least one of the following values ​​at normal conditions (0°C, 1013 hPa): 0.15 W / m·K, 0.1 W / m·K, 0.05 W / m·K, 0.025 W / m·K, and 0.02 W / m·K, and / or has a thermal conductivity of at least one of the following values ​​at least 0.15 W / m·K, 0.1 W / m·K, 0.05 W / m·K, 0.025 W / m·K, and 0.01 W / m·K, under the conditions within the process chamber.

[0016] In a preferred example, the inert gas flow may have a velocity in the main flow direction, where the average velocity measured at 1013 hPa and 0.5 cm above the opening is greater than 0.75 m / s, preferably greater than 1 m / s, and / or less than 4 m / s, preferably less than 3 m / s, and more preferably less than 2.5 m / s. These boundaries may preferably be raised when the gas pressure in the process chamber volume decreases and / or when the molar mass of the gas decreases.

[0017] In a preferred example, the process chamber has at least one oxygen sensor and / or gas density sensor and / or thermal conductivity sensor and / or thermal capacity sensor configured to measure values ​​representing the thermal conductivity and / or thermal capacity of each inert gas. At least one of these sensors is preferably located in the bottom portion of the volume. For example, at least one of these sensors may be located on the bottom and / or in a recess of the bottom and / or less than 5 cm above the bottom and / or on a support and / or below the support and / or within at least one of 10 cm, 5 cm, 2.5 cm, 1 cm, and 0.5 cm from the edge surrounding the opening. In another example, at least one of these sensors is preferably located at the (first) inert gas outlet, preferably on the bottom of the (first) inert gas outlet and / or within at least one of 10 cm, 5 cm, 2.5 cm, 1 cm, and 0.5 cm from the edge surrounding the (first) inert gas outlet. Each of these exemplary locations allows for the measurement of oxygen concentration in the vicinity of the powder bed. When He(4u) and / or Ne(10u) are used as inert gases (where u is typically a unified atomic mass unit), oxygen will accumulate at the bottom of the volume because it has a higher mass per molecule (16u). Thus, potential leaks and impurities originating from gas sources can be quickly detected. Furthermore, this measurement is as representative as possible of the oxygen level just above the powder bed. Additionally or alternatively, at least one of the sensors may be located in a duct connecting at least one inert gas outlet to at least one inert gas inlet.

[0018] At least one oxygen sensor and / or gas density sensor and / or thermal conductivity sensor and / or heat capacity sensor are preferably located within the inert gas flow through the chamber. Particularly preferably, each sensor is oriented at least substantially parallel to the inert gas flow, where at least substantially parallel means preferably parallel, but a deviation of a few degrees (e.g., within ±30°, ±20°, ±10°, ±5°, ±2.5°, ±1°, or 0°) is acceptable.

[0019] At least one oxygen sensor and / or gas density sensor is preferably connected to a process chamber control device, i.e., the entire additive manufacturing apparatus comprising the process chamber and / or electronic circuits for controlling the operation of the process chamber (hereinafter simply referred to as the “control device”). In particular, for example, when the oxygen level exceeds a predetermined threshold, the control device may increase the flow velocity of the inert gas flow above the opening, for example, by increasing the power supplied to a vacuum pump connected to the inert gas outlet and / or by opening a throttle valve upstream of the inert gas inlet. Furthermore, prior to powder bed fusion bonding, the process chamber is preferably filled with inert gas. When the oxygen level falls below a predetermined threshold, an inert gas pump may be used to circulate the inert gas from the inert gas outlet to the inert gas inlet, thereby forming an inert gas flow.

[0020] In a preferred example, the process chamber may have a gas component concentration sensor configured to measure a value representing at least one of the concentrations of O2, N2, He, Ne, Ar, Kr, Xe, and Rn, and / or a value representing the ratio of at least two of these gases in an inert gas. The gas component sensor may be located in the position described above for the oxygen sensor, or may have a gas inlet in that position. The sensor described above can be considered an example of a gas component concentration sensor. In other words, the gas component concentration sensor may be at least one of the oxygen sensor and / or gas density sensor and / or thermal conductivity sensor and / or heat capacity sensor and / or gas chromatograph and / or spectrometer and / or gas analyzer, particularly a He analyzer, or may include at least one of these. Furthermore, it should be noted that, given a known total pressure, the partial pressure values ​​of O2, N2, He, Ne, Ar, Kr, Xe, and Rn may be considered to represent at least one of the concentrations of these gases. Therefore, a simple yet efficient method for measuring concentration is to measure the partial pressure of at least one of these gases, for example, by measuring the diffusion rate through a semipermeable membrane. For example, if the semipermeable membrane is permeable only to He, the partial pressure of He in the inert gas can be measured by using the diffusion rate through the membrane at a predetermined pressure difference between the spaces separated by the membrane.

[0021] The gas component concentration sensor is preferably connected to the process chamber control device by a data line. Therefore, the values ​​obtained by the gas component concentration sensor may be available to the process chamber control device.

[0022] In any embodiment, the method may include the step of supplying at least a portion of the inert gas removed through the inert gas outlet to the process chamber through the inert gas inlet. This is also known as inert gas recycling or circulation.

[0023] Therefore, a method for melt-bonding at least a portion of a powder bed may include controlling the composition of an inert gas flow generated above the powder bed.

[0024] This method may include the step of measuring the concentration and / or partial pressure of at least one component of O2, N2, He, Ne, Ar, Kr, and Xe in an inert gas stream generated above the powder by detecting the concentration and / or partial pressure of at least one component of O2, N2, He, Ne, Ar, Kr, and Xe in the inert gas that is present in the process chamber and / or removed from the process chamber via at least one inert gas outlet and / or supplied to the process chamber via an inert gas inlet. This method may further include the step of obtaining a measurement that represents the concentration and / or partial pressure of at least one component of O2, N2, He, Ne, Ar, Kr, and Xe in the inert gas, and comparing this measurement to lower and / or upper limits for the concentration and / or partial pressure of each of the at least one component of N2, He, Ne, Ar, Kr, and Xe in the inert gas. Note that O2 is not inert and therefore should not be included in the inert gas. However, by utilizing the monitoring of unintended O2 concentrations, the concentration of the inert component of the inert gas can be increased, thereby reducing the partial pressure and concentration of O2, which can be considered an effective removal of unintended O2 from the process chamber and, consequently, from the melt bonding process.

[0025] If the aforementioned comparison indicates that this measured value is less than the lower limit value, the method adds the corresponding reduced component to the inert gas flow passing through the process chamber by, for example, circulating the corresponding reduced component from the inert gas outlet to the inert gas inlet and adding it to the inert gas flow passing through the process chamber. During this process, at least one other component of the inert gas mixture may include steps of not adding or adding relatively little to the inert gas mixture. In this context, "relatively little" refers to the amount of the reduced component, that is, it means that the amount added of at least another component to be added is less than the amount added of the reduced component.

[0026] Similarly, if the aforementioned comparison indicates that this measured value exceeds the upper limit value, the method adds at least one component different from the aforementioned component having a measured value exceeding the upper limit value to the inert gas in the process chamber by, for example, supplying it from the inert gas outlet through a duct to the inert gas inlet (and thus into the process chamber) and adding this different component to the inert gas flow. During this process, the aforementioned component having a measured value exceeding the upper limit value may include steps of not adding or adding relatively little. As described above, "relatively little" relates to the amount of at least one other component to be added. In other words, at least one other component is added in a larger amount than the component having a measured value exceeding the upper limit value. [[ID=#6]]

[0027] This method enables partial and selective replenishment of only those components of the inert gas that have been shown to be insufficient in a given composition as defined by the upper and lower limits of each component. This helps to maintain low operating costs while maintaining the high quality of the workpiece. Such method steps are based on the consideration that, for practical purposes, the inert gas is often substantially a mixture of He and / or Ne with Ar and / or N2, where the concentrations of He, Ne, Ar, and N2 in the mixture are well-defined. However, He and Ne diffuse through the duct walls and other defining structures of the process chamber housing at a significantly high rate. Thus, by this method, the partial pressure and / or concentration of He and / or Ne in the inert gas can be maintained within a predetermined limit, while the inert gas depleted of He and / or Ne from the process chamber is not replaced by (expensive) "new" inert gas. For example, if a value representing the concentration (and / or partial pressure) of He and / or Ne is measured and a decrease in He and / or Ne below their respective lower limits is observed, only He and / or Ne is added to the inert gas circulating through the process chamber housing. Such an approach can also be used for all other inert gases mentioned above, i.e., the correction of the decrease in He and / or Ne is merely a preferred example. All other decreases can also be eliminated by adding the depleted component, preferably only that component.

[0028] These steps for controlling the composition of the inert gas stream generated above the powder bed may be performed by a process chamber control device, also referred to as a "control device". In other words, the process chamber control device may be configured to directly perform any of the method steps described above, or to perform them by controlling and / or communicating with corresponding components such as, for example, a gas component concentration sensor.

[0029] The corresponding process chamber housing may therefore have a process chamber control device. The process chamber control device may be connected, for example, to at least one gas component concentration sensor via a data line and / or any other data transmission means. Such a gas component concentration sensor may be located within the process chamber. Alternatively or additionally, this (or other) gas component concentration sensor may be located in a duct connecting an inert gas outlet to an inert gas inlet, and / or mounted on this duct, and / or incorporated into this duct.

[0030] The process chamber may further include an inert gas component supply source containing only one or a limited number of components of the inert gas within the process chamber. For example, if the inert gas is a mixture of three gases in total, the inert gas component supply source may contain only He and / or Ne, and not Ar or N2. In practice, it is sufficient that the concentration of the reduced inert gas component in the gas supplied by the inert gas component supply source is higher than a predetermined or intended concentration of the reduced component in the inert gas. This is because, in this case, adding the gas mixture from the inert gas component supply source increases the concentration of the reduced component in the inert gas circulating through the process chamber and the duct connecting the inert gas outlet to the inert gas inlet.

[0031] The process chamber may have two or more inert gas component sources, each containing one different inert gas component and / or a different mixture of inert gases.

[0032] Typically, "a limited number of components" means that at least one component of the (intended) inert gas mixture is not present or is insufficient in the inert gas component supply source. The inert gas component supply source may be fluidly connected to the inert gas inlet via at least one inert gas component valve, or to a separate gas inlet, for example, via a branch in a duct. Fluid connection via a duct is preferred because it ensures a more uniform concentration of the components of the inert gas supplied to the process chamber. In other words, the inert gas in the process chamber has a more uniform composition.

[0033] The process chamber control device may be connected to the inert gas component valve, for example, via at least one control line and / or contactless data connection, thereby enabling the inert gas component valve to be opened and closed.

[0034] In another preferred example, the process chamber includes a heater configured to raise the temperature of at least a portion of the inert gas flow through the process chamber to at least one of the following temperatures: 25°C, 40°C, 60°C, 80°C, 100°C, 150°C, 250°C, 300°C, 350°C, 400°C, 450°C, 500°C, 600°C, 700°C, 800°C, 900°C, and 1000°C. When higher temperatures are used, the process chamber housing is preferably thermally insulated. Such an increase in gas temperature reduces the temperature gradient in the smoke column and therefore reduces beam distortion in the smoke column, although it is not negligibly small.

[0035] As already mentioned above, the process chamber preferably includes a pressure control device configured to maintain the pressure inside the process chamber below the ambient pressure outside the process chamber and / or below at least one of the following pressures: 1000 hPa, 900 hPa, 800 hPa, 700 hPa, 600 hPa, 500 hPa, 400 hPa, 300 hPa, 200 hPa, and 100 hPa. The pressure control device may be incorporated into the process chamber control device or may form part of the process chamber control device. In another preferred example, the pressure inside the process chamber is higher than the ambient pressure, thereby ensuring that oxygen is not accidentally drawn into the process chamber. In yet another example, the process chamber is housed in a separate housing, where the pressure inside the process chamber is lower than the ambient pressure, while the pressure in the volume defined by the boundary between the process chamber and the separate housing is higher than the ambient pressure, and the gas in this volume is also an inert gas, preferably the same as the one inside the process chamber. This fills the volume between the process chamber and the boundary of another housing with an inert gas, which has a pressure higher than the ambient pressure. This reduces the risk of oxygen being accidentally drawn into the process chamber while simultaneously ensuring a low pressure within the process chamber.

[0036] For example, the inert gas outlet may be fluidly connected to the low-pressure side inlet of the gas pump (e.g., the vacuum pump inlet) via, for example, the duct described above, and / or the inert gas inlet may be fluidly connected to an inert gas supply source (e.g., the high-pressure side gas outlet of the gas pump), and a throttle valve may be located upstream of the inert gas inlet. An optional pressure control device may be configured to increase and / or decrease the power supplied to the gas pump. Furthermore, this pressure control device may be configured to open and / or close the throttle valve by, for example, supplying power to an actuator. The optional pressure control device may therefore also control the flow velocity of the inert gas flow. The optional pressure control device may be connected to at least one pressure sensor and / or flow velocity sensor and may control the pressure and / or flow velocity in the process chamber in response to signals provided by at least one of the pressure sensor and / or flow velocity sensor.

[0037] Changes in the inert gas can affect the signals provided by flow velocity sensors and / or pressure sensors. Such effects may necessitate recalibration of the sensors if the inert gas changes during the manufacturing of a workpiece or between the manufacturing of two workpieces. For example, if an inert gas with increased heat capacity and / or increased thermal conductivity is used, a flowmeter used to measure flow velocity may require recalibration. For instance, if the thermal conductivity of the inert gas increases, a hot-wire flowmeter will experience better cooling. Therefore, if the increased thermal conductivity is not taken into account, the resistivity of the hot wire will decrease, which will likely lead directly to an inaccurate flow velocity reading. Similarly, if a vane flowmeter or cup flowmeter is used, changes in the (average) molar mass and / or density of the inert gas may also necessitate recalibration of the flow velocity sensor.

[0038] In a preferred example, the process chamber further comprises at least one second gas outlet located in at least one of the bottom surface, support, opening wall, and bottom surface of the opening. The second gas outlet may be used to replace a gas (mixture) such as air with an inert gas, for example, at least one of He and / or Ne and / or Ar and / or N2, which may then preferably be supplied to the volume via at least one second inert gas inlet in the ceiling. The use of expensive He and / or Ne or other inert gases can be reduced by each of these means.

[0039] An optional second gas outlet may be connected to a second gas outlet control valve, preferably to a check valve configured to prevent gas from flowing into the process chamber through the second gas outlet. Furthermore, the second gas outlet may be connected to the gas inlet of a second outlet vacuum pump via a tube or the like.

[0040] As already mentioned, the process chamber preferably comprises at least one (laser) beam entry window which may be located above the support. In a particularly preferred example, the process chamber further comprises at least one inert gas jet inlet nozzle. As will be discussed in more detail later, the term “jet” is used solely to indicate that this gas flow is a linguistically distinct second gas flow that flows above the inert gas flow. The inert gas jet inlet nozzle is preferably located in the upper portion of the process chamber and preferably directed to supply an inert gas jet between the window and the support. Particularly preferably, the inert gas jet is directed to adhere to the window surface and / or downward. This is achieved by directing the inert gas jet inlet nozzle in such a manner, for example, toward the window surface and / or by utilizing the Coanda effect.

[0041] Preferably, at least one inert gas jet outlet nozzle may be located opposite the inert gas jet inlet nozzle, and is therefore well positioned to supply an inert gas jet between the window and the support.

[0042] The inert gas jet counteracts the effect that smoke tends to rise higher in a reduced-density atmosphere. The inert gas jet protects the window from contamination by condensed or sublimated smoke, which can degrade beam quality and, consequently, workpiece quality. Therefore, the proposed means allows for proper maintenance of the volume's vertical dimensions, thereby reducing operating and installation costs. However, the increased distance between the laser source and the powder leads to more imperfections in beam focusing, ultimately resulting in a decrease in workpiece quality to some extent.

[0043] For example, at least one inert gas jet inlet nozzle is positioned at an angle α from a direction parallel to the (first) inert gas inlet. js It may have a nozzle outlet opening directed inward, α js The angle is ∈A, where A = {30°, 20°, 10°, 5°, 2.5°, 1°, 0.5°, 0°}. By this means, turbulence within the volume is reduced, and therefore the efficiency of smoke removal from the volume is increased.

[0044] Preferably, the velocity of the inert gas jet relative to the window is at least 1.1, 1.25, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 7.5 and / or 10 times the velocity of the inert gas flow 0.5 cm above the opening. Thus, this increased velocity provides a velocity gradient from the bottom to the ceiling. This gradient allows for the safe removal of smoke without blowing powder from the powder bed towards the inert gas outlet.

[0045] In a preferred example, the temperature of at least one optional inert gas jet is lower than the temperature of the main inert gas stream, measured at least at the corresponding nozzle opening. Thus, the residue in the smoke can condense before reaching the window, and the residue in the smoke does not condense, or at least hardly condenses, on the window.

[0046] In another example, the temperature of at least one optional inert gas jet is higher than the temperature of the main inert gas flow, measured at least at the corresponding nozzle opening. This allows the powder bed to be efficiently cooled by the main inert gas flow, which preferably flows at least almost directly above the powder bed. This is achieved by positioning the lower edge of the (first) inert gas inlet and / or the lower edge of the (first) inert gas outlet at the height of the edge of the support opening and / or the height of the bottom surface, or slightly above these heights. Slightly above means within at least one of the heights of 0.5 cm, 1 cm, 1.5 cm, 2 cm, and / or 2.5 cm above the corresponding reference height. Furthermore, the temperature of the main (first) inert gas flow from the (first) inert gas inlet to the (first) inert gas outlet is preferably below the ambient temperature, for example, at least one of the temperatures of 23°C, 20°C, 18°C, 10°C, 0°C, -5°C, -10°C, and -20°C. The lower the temperature, the better the cooling, i.e., the better the heat transfer from the powder bed and / or workpiece to the main inert gas flow. The temperature of the inert gas jet may preferably be above the ambient temperature, and may be at least one of the following temperatures: 25°C, 40°C, 60°C, 80°C, 100°C, 150°C, 250°C, 300°C, 350°C, 400°C, or 450°C. Such a particularly preferred combination of having a lower temperature near the powder bed and a higher temperature above it provides both good cooling and low beam distortion.

[0047] Furthermore, it is preferable that the vertical thickness of the main inert gas flow or the main inert gas flow is significantly smaller than the vertical thickness of the inert gas jet above the main inert gas flow. The vertical thickness of each flow can be adjusted, for example, by the vertical dimensions of each inlet opening. Therefore, the vertical dimension d2 of the inert gas jet inlet is preferably at least x times the vertical dimension d1 of the (first) inert gas inlet, in which case x ∈ {1.5, 2, 2.5, 5, 10, 15}, i.e., x·d1 ≤ d2.

[0048] As is clear, both the main inert gas flow from the inert gas inlet nozzle to the inert gas outlet nozzle and the inert gas jet are "inert gas flows," and the terms main inert gas flow and inert gas jet are used solely to distinguish them linguistically. Alternatively, the terms first gas flow and second gas flow could be used, but we believe the initially proposed terminology is clearer. As is clear, in a preferred example, the second inert gas flow (i.e., the inert gas jet) has a higher flow velocity over the entire volume than the first (main) inert gas flow. The flow rate of the second inert gas flow may be higher than that of the first (=main) inert gas flow. Thus, the word "main" has no relevance to the amount of gas flowing per unit time compared to the other inert gas flow.

[0049] The additive manufacturing apparatus according to the present invention may, of course, be characterized by including a process chamber having at least one of the features described above. In particular, the additive manufacturing apparatus may have one laser beam entry window and at least two (laser) beam sources located outside the process chamber and in front of at least one window, each configured to radiate at least one (laser) beam onto a powder bed on the upper surface of a support. Needless to say, the window is at least substantially transparent to the beam radiated by the (laser) beam sources onto the support through at least one window. In a preferred example, the additive manufacturing apparatus is configured to scan the surface of the powder bed below the smoke column generated by the operation of the first (laser) beam source. Such means can also improve workpiece quality, for example, by optimizing the thermal stress on the workpiece during manufacturing.

[0050] Description of the drawing In the following, the invention will be described as an example, without limiting the general concept of the invention, based on several examples of embodiments related to the drawings. [Brief explanation of the drawing]

[0051] [Figure 1] This figure shows an exemplary process chamber for additive manufacturing equipment. [Figure 2] This figure shows another exemplary process chamber of an additive manufacturing apparatus.

[0052] Figure 1 shows a simplified cross-sectional view of an exemplary additive manufacturing apparatus 1 having a process chamber 5. The process chamber 5 has a volume 51 surrounded by side walls 11, 12, 13 (the fourth side wall is not visible), a ceiling 10, and a bottom surface 9. The bottom surface 9 has an opening 94 with an opening wall 93. The opening wall 93 may provide a linear bearing for a movably supported liftable support 8. An optional powder bed 99 may be on the upper surface of the support 8, and a partially manufactured workpiece 4 may be embedded in this powder bed. The powder bed 99 and the workpiece 4 are shown by way of example only, but the additive manufacturing apparatus 1 and / or the process chamber 5 are typically delivered without a powder bed or a workpiece.

[0053] The ceiling 10 has windows 101, 102 that are transparent to beams 81, 91 emitted by beam sources 80, 90. A first beam source 80 and a second beam source 90 that emit a first beam 81 and a second beam 91 respectively are shown. Preferably, the process chamber 5 has three or more beam sources 80, 90. The windows 101, 102 may be integral, and thus at least one window is provided above the opening 94 in the bottom surface.

[0054] An (first) inert gas inlet 6 in the front side wall 11 and an (first) inert gas outlet 7 in the rear side wall 12 enable the supply of a main inert gas flow 20 that crosses the opening 94 in the bottom surface 9, i.e., in the main inert gas flow direction 2. As can be seen, the main inert gas flow 20 is at least substantially parallel to the bottom surface 9 (i.e., ±α ms (α ms ∈ {30°, 20°, 10°, 5°, 2.5°, 1°, 0.5°, 0°}) and thus can flow at least substantially parallel to the powder bed surface and the powder bed support surface of the support 8. In the illustrated example, the main inert gas flow direction 2 has a small downward component. Preferably, the inert gas contains at least 20% helium (He) and / or 1.4 kg / m 3It has a density less than and / or a temperature above the dew point temperature of the gas. In one example, the pressure may be greater than or equal to the ambient pressure. In another example, the pressure may be less than or equal to the ambient pressure.

[0055] Above the main inert gas inlet 6 are at least one optional second inert gas inlet 256 and at least one optional third inert gas inlet 266. Above the main inert gas outlet 7 are at least one optional second inert gas outlet 257. These can also be called inert gas jet inlets or inert gas jet outlets, respectively.

[0056] During operation, a second inert gas flow may flow above the main (first) inert gas flow from at least one optional second inert gas inlet 256 to at least one optional second inert gas outlet 257. As indicated by arrow 25, the volume per unit time, i.e., flow rate and / or velocity, of the optional second inert gas flow 25 is preferably higher than the flow rate and / or velocity of the main inert gas flow 20, respectively. Furthermore, the downward component of the flow direction of the second inert gas flow direction 252 is preferably greater than the downward component of the main inert gas flow direction 2. The temperature of the second inert gas flow 25 is preferably lower than the temperature of the main inert gas flow 20.

[0057] The optional third inert gas inlet 266 is preferably located near (within 10 cm, 5 cm, 2.5 cm, and / or 1 cm of) at least one window 101,102 of the ceiling 10 and is positioned to deposit a third inert gas flow onto the surface of at least one window 101,102, thereby contributing to keeping at least one window 101,102 condensation-free. Preferably, the temperature of the inert gas exiting the third inert gas inlet is higher than the temperature of the second inert gas entering the volume 51 from at least one second inert gas inlet 256.

[0058] As shown in the diagram, each beam 81, 91 is directed to a different location in the powder bed 99, and the melting process generates first and second smoke columns 82, 92. The distance between the first position and the second position may be less than at least one of the following distances: 100 mm, 70 mm, 40 mm, 30 mm, 20 mm, and 10 mm. The time interval between the moments when the first beam and the second beam are radiated to the first position and the second position may be less than at least one of the following periods: 10%, 20%, 30%, 40%, 50%, 60%, 70%, and 80% of the maximum period during which the first beam or the second beam is radiated onto the layer. As shown in the diagram, the second beam 91 passes through the first smoke column 82, which is generated by the interaction between the first beam 81 and the powder bed 99.

[0059] The inert gas is removed by at least one pump 32, i.e., the first and second inert gas outlets 7,257 are in fluid communication with the low-pressure inlet of the gas pump 32, and the pump then supplies the inert gas to at least one of the inert gas inlets 6,256,266 via the duct 33. The temperatures of the different inert gas flows can preferably be controlled by optional indirect heat exchangers 201,251,261.

[0060] The control device 3 may be connected to the beam sources 80, 90, sensors 30, pump 32, valve 38, etc., by data lines and / or power lines. Connection examples are shown by dashed or dotted arrows.

[0061] Figure 2 shows another simplified cross-sectional view of an exemplary additive manufacturing apparatus 1 having a process chamber 5. The description of Figure 1 can also be read for Figure 2. Here, only the differences will be described. Similar to Figure 1, at least one of the inert gas outlets 7 and 257 of the process chamber 5 may be connected to at least one of the inert gas inlets 6, 256, 266 via a duct 33. The pump 32 may have a pump inlet that is in fluid communication with at least one of the inert gas outlets 6, 25, and the pump outlet may be in fluid communication with at least one of the inert gas inlets 6, 256, 266 via a duct 33. The duct may have a gas component sensor 30. The values ​​measured by the gas component sensor 30 may be supplied to the control device 3 by several data lines or any other means of communication, regardless of its location. The control device may be referred to as the process chamber control device 3.

[0062] The process chamber housing preferably has at least one of these gas component sensors 30. In Figure 2, two gas component sensors 30 are shown in a preferred position for illustrative purposes. Other numbers of gas component sensors may also be used.

[0063] The process chamber housing may further have at least one inert gas component supply source 34. In one example, the inert gas component supply source 34 may have a tank filled with, or configured to be filled with, for example, He and / or Ne or other inert gases or mixtures of inert gases.

[0064] The inert gas component supply source 34 is fluidly connected to at least one of the inert gas inlets 6, 256, and 266 via the inert gas component valve 36.

[0065] The control device 3 is preferably configured to monitor the concentration and / or partial pressure of at least one of He and Ne in the inert gas in the process chamber 5 and / or duct 33 based on at least one measured value. Such a measured value can be derived from at least one of at least one inert gas component sensors 30. If the concentrations of He and Ne in the inert gas in the process chamber 5 fall below a predetermined lower limit, the control device may be configured to open the inert gas component valve 36, for example, for a predetermined period of time. This period may be calculated based on the difference between the lower limit and the measured value. By opening the inert gas component valve 36, the reduced inert gas component can be supplied to the inert gas being supplied to the process chamber. This allows the concentration of the reduced component, in this example, He and / or Ne, to be corrected. Similarly, if the measured concentration of another component of the inert gas in the process chamber 5 and / or duct exceeds an upper limit, the control device can open the inert gas component valve 36 to reduce the concentration of the component that has a concentration above the upper limit. The process chamber may have multiple inert gas component supply sources 34 filled with different inert gases and corresponding inert gas component valves 36, thereby allowing for selective replenishment of depleted inert gas components. [Explanation of symbols]

[0066] 1. Additive manufacturing equipment 2. Main inert gas flow direction 3. Control Devices / Process Chamber Control Devices 4. Bonding area between workpiece / raw material 5 Process Chambers 6. Gas Inlet 7 Gas outlet 8 Support 9. Base 10 Ceiling 101 Window 102 Window 11 First side wall 12. Second side wall 13. Third side wall 20 Main inert gas flow 201 Heat exchanger 25. Second inert gas flow (inert gas jet) 251 Heat exchanger 252 Direction of the second inert gas flow 256 Second inert gas inlet 257 Second inert gas outlet 26 Third inert gas flow 261 Heat exchanger 266 Third inert gas inlet 30 Gas component sensors, for example, oxygen sensors and / or gas density sensors and / or gas component concentration sensors 32 pumps 33 Duct 34. Source of inert gas components 35 Heater 36 Inert gas component valve 50 Ricohta 80 First beam source 81 First Beam / First Laser Beam 82 First column of smoke 90 Second beam source 91 Second beam / Second laser beam 92 Second column of smoke 93 Opening Wall 94 Support opening at the bottom surface 9, configured to receive the support 8. 99 Powder bed

Claims

1. Additive manufacturing apparatus comprising at least one first beam source (80) configured to emit at least one first beam (81), at least one second beam source (90) configured to emit at least one second beam (91), and a process chamber housing (1), wherein the process chamber housing (1) has a process chamber (5), and the process chamber (5) has at least the following components: The bottom surface (9), ceiling (10), and side walls (11, 12, 13) together surround the volume (51) of the process chamber (5), An inert gas inlet (6) configured to supply an inert gas into the process chamber (5), An inert gas outlet (7) configured to release the inert gas from the process chamber (5) and It has, The bottom surface (9) has an opening (94) defined by a plurality of opening walls (93), and a vertically movable support (8) for supporting a three-dimensional object (4) placed between the powder bed (99) and the plurality of opening walls (93), and, The gas inlet (6) has a flow rate of 1.4 kg / m³. ３ In an additive manufacturing apparatus configured to supply a lightweight inert gas having a density of less than 1 to the process chamber (5), The additive manufacturing apparatus controls the additive manufacturing apparatus to at least, A first smoke column (82) is generated by melting and bonding a first position of the powder bed (99) using the first beam (81), and, The process chamber control device (3) is configured to perform a melting step, which generates a second smoke column (92) by melting a second position of the powder bed (99) using the second beam (91), Here, the first position is closer to the inert gas inlet (6) than the second position, the second position is closer to the inert gas outlet (7) than the first position, and the at least one second beam (91) is controlled to melt-bond the second position of the powder bed (99), which is covered by the first smoke column (82) generated by melt-bonding the first position of the powder bed (99) with the at least one first beam (81). The inert gas inlet (6) and the inert gas outlet (7) are configured to remove the smoke columns (82, 92) from the process chamber (5) by an inert gas flow, and the inert gas flow is generated by an inert gas containing at least 20% He and / or Ne. An additive manufacturing apparatus characterized by the following.

2. The additive manufacturing apparatus according to claim 1, wherein the inert gas inlet (6) and the inert gas outlet (7) are arranged on opposite sides of the process chamber and / or the opening (94), so as to generate the inert gas flow (2) in the main flow direction (2) from the inert gas inlet (6) through the opening (94) to the inert gas outlet (7).

3. The inert gas flow in the main flow direction (2) has a flow velocity, and the average flow velocity measured 0.5 cm above the opening (94) is It is greater than 0.75 m / s and / or It is less than 4 m / s. Additive manufacturing apparatus according to claim 1.

4. The process chamber (5) has at least one gas component concentration sensor, and at least one of the at least one gas component concentration sensor (30) is On the bottom surface, and / or In the recess of the bottom surface, and / or Below a distance of 5 cm above the aforementioned bottom surface, and / or On the support and / or below the support, and / or Within 10 cm from the edge of the bottom surface surrounding the opening (94), and / or The inert gas outlet (7) is placed inside the duct (33) that connects to the inert gas inlet (6), The additive manufacturing apparatus according to claim 1, which is arranged in this manner.

5. The additive manufacturing apparatus according to claim 4, wherein the process chamber housing further comprises at least one inert gas component supply source (34) fluidly connected to the inert gas inlet (6) of the process chamber (5) via an inert gas component valve (36).

6. The additive manufacturing apparatus according to claim 1, wherein the process chamber (5) is equipped with a heater (35) configured to heat at least a portion of the inert gas flow passing through the process chamber to 25°C or higher.

7. The additive manufacturing apparatus according to claim 1, wherein the inert gas outlet (7) is in fluid communication with a vacuum pump and / or the inert gas inlet (6) is in fluid communication with an inert gas supply source, and a throttle valve is located upstream of the inert gas inlet.

8. The aforementioned process chamber is: At least one second gas outlet provided on at least one of the bottom surface, the support, the opening wall, and the bottom surface of the opening, and / or At least one second inert gas inlet provided in the ceiling The additive manufacturing apparatus according to claim 1, further comprising:

9. The second gas outlet is connected to a second gas outlet control valve, and / or The second gas outlet is connected to the gas inlet of the second outlet vacuum pump. The additive manufacturing apparatus according to claim 8.

10. The additive manufacturing apparatus according to claim 1, further comprising: the process chamber housing (1) at least one beam entry window located above the opening (94); and at least one inert gas jet inlet nozzle disposed to supply an inert gas jet between the window and the support.

11. The process chamber housing (1) includes at least one beam entry window located above the opening (94), The additive manufacturing apparatus according to claim 1, wherein the process chamber housing (1) further comprises at least one inert gas jet inlet nozzle and at least one inert gas jet outlet nozzle arranged to supply an inert gas jet between the window and the support.

12. The at least one inert gas jet inlet nozzle is positioned at an angle α from a direction parallel to the inert gas inlet. ｊｓ It has a nozzle outlet opening directed within the α ｊｓ The additive manufacturing apparatus according to claim 10, wherein is ∈A, and A = {30°, 20°, 10°, 5°, 2.5°, 1°, 0.5°, 0°}.

13. At least two beam sources of the additive manufacturing apparatus are positioned in front of at least one beam entry window. Outside the process chamber (5), the at least two beam sources are each configured to emit at least one beam onto the powder bed (99) on the upper surface of the support (8). Additive manufacturing apparatus according to claim 10.

14. A method for melt-bonding at least a portion of a layer of powder bed (99), comprising: The steps include: radiating at least two different beams (81, 91) from at least two different beam sources (80, 90) to at least two different positions on the powder bed (99) that generate smoke columns (82, 92), respectively; A step of removing the smoke column (82, 92) by generating an inert gas flow from an inert gas inlet (6) to an inert gas outlet (7), wherein the inert gas flow has a component direction parallel to the powder bed, a first position struck by a first beam (81) from a first beam source (80) is closer to the inert gas inlet (6) than a second position struck by a second beam (91) from a second beam source (90), and the second position is closer to the inert gas outlet (7) than the first position, A step of melting and bonding the second position of the powder bed (99) with the second beam (91) from the second beam source (90), wherein at least a portion of the first smoke column (82) is located between the second beam source (90) and the second position, and the density of the inert gas flow is 1.4 kg / m³ under standard conditions and / or at a distance of 20 mm above the layer. ３ The steps are as follows: A method comprising, wherein the inert gas stream is generated by an inert gas containing at least 20% He and / or Ne.

15. The method according to claim 14, further comprising the step of providing an additive manufacturing apparatus according to any one of claims 1 to 13.

16. The method according to claim 14, wherein the distance between the first position and the second position is less than 100 mm.

17. The method according to claim 16, wherein the time interval between the moments when the first beam and the second beam are radiated to the first position and the second position is less than 80% of the maximum period during which the first beam (81) or the second beam (91) is radiated onto the layer.

18. The method according to claim 14, wherein the generated inert gas stream contains at least 20% He, and these percentages are relative to the amount of moles of He relative to the total amount of gas.

19. The method according to claim 14, wherein the generated inert gas flow has a temperature of 25°C or higher.

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