Patent Description:
Additive manufacturing, e.g., selective laser melting, can be understood in that a thin layer of e.g. metal powder is spread onto a substrate and then fused or hardened by a laser beam. The laser beam effects a melting and welding of the metal powder particles to form a quasi-solid metal. This process can be repeated layer by layer until the product is complete.

Conventional powder-bed-based laser melting systems for a layered construction are not designed for a high system productivity, rather conceptually intended for individual pieces and prototypes. Further, such systems require a time-consuming setup and preparation. For example, a change of powder material requires in most cases a very time-consuming cleaning of all powder-contaminated components and assemblies before the system can be filled with a fresh metal powder. In addition, the powder must be manually removed from a construction area of the system using protective devices such as a dust mask or gloves and an operation is only permitted in a dust-free environment. During this maintenance work, the system is not productive and cost-intensive laser and optical units are unavailable due to the manual intervention and work. The productivity of conventional additive manufacturing systems is thus limited and not suitable for industrial mass production of components.

<CIT> discloses a device for a production of metallic or ceramic molded bodies. The device comprises supports for a layer structure of molded bodies arranged in a process chamber housing and a powder layer preparation unit having a powder reservoir assigned to the supports to prepare the powder for each construction process.

<CIT> discloses an interchangeable container for a plant for a construction of a molded body by forming layers from granular materials horizontally lying one upon the other. The interchangeable container comprises a ground structure movable in an interior of a container in a direction to container sidewalls, and a spindle drive having a screw rod that is revolvably incorporated in a container side and a spindle nut on which the ground structure is braced, so that the ground structure is gradually lowered in the interior of the container by the spindle drive.

<CIT> discloses an apparatus with a build module and methods for additive manufacturing.

There may be a need to provide an improved additive manufacturing system and method, which allow a continuous production of layered products, accordingly a high productivity of the additive manufacturing system.

The objective of the present invention is solved by the subject-matters of the independent claims, wherein further embodiments are incorporated in the dependent claims. It should be noted that the aspects of the invention described in the following apply also to the additive manufacturing system and the method for applying a powder material to a substrate.

According to the present invention, an additive manufacturing system for applying a powder material to a substrate is presented. The additive manufacturing system comprises a rotary manufacturing unit.

The rotary manufacturing unit comprises a first manufacturing chamber and a second manufacturing chamber. The first manufacturing chamber comprises a first openable cover and the second manufacturing chamber comprises a second openable cover. The first manufacturing chamber comprises a first doctor blade configured to apply a powder layer on a first substrate and the second manufacturing chamber comprises a second doctor blade configured to apply a powder layer on a second substrate. The rotary manufacturing unit is configured to be rotatable into a first position in which the first manufacturing chamber is positioned for irradiating the powder layer on the first substrate and the second manufacturing chamber is positioned for enabling an opening of the second cover. The rotary manufacturing unit is also configured to be rotatable into a second position in which the second manufacturing chamber is positioned for irradiating the powder layer on the second substrate and the first manufacturing chamber is positioned for enabling an opening of the first cover.

The additive manufacturing system according to the invention is suitable for selective laser melting systems. Selective laser melting (SLM) can be understood in that thin layers of fine metal powder are evenly distributed on a substrate by means of a doctor blade as coating mechanism. This may take place inside a chamber containing a tightly controlled atmosphere using inert gas at very low oxygen levels. Once the layer has been distributed, the two-dimensional layer or slice of a product may be fused or hardened by selectively melting the powder. This may be accomplished by means of a high power laser beam. The laser energy shall be configured to permit a melting and welding of the fine metal powder particles to form a quasi-solid metal. This process shall be repeated layer after layer until the product is complete.

The rotary manufacturing unit may be shaped three-dimensional having a bottom, walls and an inner space where the selective melting of the metal powder can be conducted. The term "rotary" may be understood in that the manufacturing unit can be rotated about a center of the manufacturing unit, for example, by means of a rotary drive and a pivot bearing ring gear, each of which may be rotated <NUM> degrees, preferably continuously in the same direction and not alternating.

The rotary manufacturing unit may comprise at least two structurally identical manufacturing chambers. However, the number of manufacturing chambers arranged in the rotary manufacturing unit is not limited to two. Each of the manufacturing chambers may comprise an openable cover, a substrate and a doctor blade. The openable cover can be operated manually or automatically. The openable cover can be configured to prevent penetrating of substances interfering the SLM process such as dust, oxygen or the like. Accordingly, the openable covers may be hermetically sealed in a closed position, such that a protection atmosphere may be provided in the manufacturing chambers.

The doctor blade may be configured to be moveable relative to the substrate and to spread the powder material onto the substrate. The term "doctor blade" can be understood as doctor knife, spreading knife, squeegee, scraper, wiper, coater, roller or the like. The doctor blade may apply any kind of coating mechanism suitable to spread or distribute material on the substrate or carrier or another material layer and/or to remove excess material such as powder material or splashes from the substrate or another material layer.

By rotating the rotary manufacturing unit, the first manufacturing chamber may be positioned in an irradiating position whereas the second manufacturing chamber may be positioned in a maintaining position and vice versa. In the irradiating position, i.e. operating position, the respective manufacturing chamber is configured to receive a laser beam to irradiate the powder layer on each substrate. Further, in the maintaining position, the respective manufacturing chamber is configured to enable an opening of the openable cover to execute job preparation activities such as refilling the fresh powder material, replacing a doctor blade etc. for a succeeding SLM process, maintenance works, cool down the manufacturing chamber and product and/or remove the components and the product out of the additive manufacturing system.

The additive manufacturing system according to the invention may allow a continuous production of products by layering of material (metal) powder, which again enables a mass or series production of the layered products. Accordingly, it may not be necessary to shut the additive manufacturing system down to execute maintenance works or to remove the products out of the additive manufacturing system. As a result, irradiation time can be maximized and the laser can be operated continuously, which means a maximum overall equipment efficiency and a parallelization of main time and pre- and post-processing can be achieved.

In an example, the first manufacturing chamber and the second manufacturing chamber are of essentially similar in size and/or shape. In other words, the manufacturing chambers may have an identical structure such that the rotation of the rotary manufacturing unit does not affect the selective melting of the metal powder on the substrate, instead results in the same product without any adjustment of the components in the rotary manufacturing unit. Consequently, a reliable continuous SLM process can be realised.

In an example, the rotary manufacturing unit has an essentially circular base area. In other words, the bottom of the rotary manufacturing unit may be shaped as a circle or the like, which allows a smooth rotation of the rotary manufacturing unit about its center.

In an example, the first manufacturing chamber and the second manufacturing chamber each comprises a ventilation inlet and a ventilation outlet configured for providing a gas flow relative to the respective substrate. For an optimal laser melting process, it might be necessary to remove smoke, splashes and particles particularly on an optic passage, where for example a laser beam can be transmitted, by means of a laminar gas flow over the substrate. The ventilation inlet and the ventilation outlet may be configured to provide an inert gas to the manufacturing chamber to protect the powder material from oxidation or to form a vacuum in the manufacturing chamber. The ventilation inlet and outlet may be a simple hole, a gas port, a gas nozzle or the like. They may also be a single opening, a row of openings, an array of openings or the like. The gas flow may be configured to reduce smoke generated by the laser beam scanning the powder material spread on the substrate or to provide an oxygen-reduced process condition. The ventilation inlet may be configured to provide the gas flow essentially parallel to a motion direction of the doctor blade relative to the substrate or essentially perpendicular to the motion direction of the doctor blade relative to the substrate or in any other angular direction relative to the motion direction of the doctor blade. Each manufacturing chamber may also have more than one ventilation inlet and outlet to provide the gas flow separately at the optic passage and the substrate.

In an example, the first manufacturing chamber and the second manufacturing chamber each comprises a detector window configured to let a detector signal pass. Through the detector window, various imaging sensors may monitor the SLM process. Imaging sensors may be mounted for example outside of each manufacturing chamber and monitor the process through the detector window. The imaging sensors may monitor a powder melting bath as well as the entire substrate surface in order to control a powder application quality or a surface temperature etc. The imaging sensors may also allow, for example, monitoring the gas flow, particularly a homogeneous and laminar gas flow, to avoid an oxidation of the powder material, a moisture absorption by the powder material etc. during a laser scanning. Further, the gas flow may be monitored over the entire working space of the additive manufacturing device. Consequently, a reliable manufacturing process and thereby high quality products may be achieved.

In an example, the first manufacturing chamber and the second manufacturing chamber each comprises a manufacturing chamber bottom plate, which comprises a guiding unit configured to guide the respective doctor blade. The manufacturing chamber bottom plate may be part of the circular bottom of the rotary manufacturing unit or a removable plate. The guiding unit may be arranged on the manufacturing chamber bottom plate and may serve as an accurate reference and running surface for the doctor blade. The guiding unit may be easily replaced in case of wear.

In an example, the first cover and the second cover each comprises an irradiation window configured to let irradiation pass to the powder layer. The irradiation window of each of openable cover may be configured for receiving an irradiation into the manufacturing chamber. The irradiation window may be formed from an optically transparent material, which can be placed essentially above the substrate of the manufacturing chamber in a closed position of the openable cover. The irradiation window may be sealed in the openable cover to prevent an entering of any undesired component into the manufacturing chambers. This allows a separation of a laser source from the laser melting process, consequently may prevent contacting splattering vapors, splashes and powder dusts on the laser optics. Hence, the maintenance and cleaning efforts for an operator may be reduced.

In an example, the first manufacturing chamber and the second manufacturing chamber each further comprise a sealing. Accordingly, when the openable covers are in closed position, i.e. engaged with the rotary manufacturing unit, the sealing may hermetically seal the openable cover relative to the manufacturing chamber or the rotary manufacturing unit. Hence, a protection atmosphere may be established in the manufacturing chambers by applying vacuum and then introducing inert gas into the manufacturing chambers. It is particularly advantageous for a high-quality process if it is possible to ensure a low oxygen content during the laser melting process.

According to the invention, the additive manufacturing system further comprises at least a powder unit configured to store fresh powder, to apply a powder layer to a substrate, and to receive excess powder. The powder unit may allow a fluent supply of the material powder to the substrate of the additive manufacturing system such that a fresh powder can be accurately provided and the remaining / excess powder can be clearly collected.

In an example, the powder unit comprises e.g. three containers, i.e. a fresh powder container configured to store fresh powder, a powder application container configured for forming a powder layer on the substrate, and an excess container configured to collect excess powder and splashes after applying the powder layer to the substrate. The powder unit can be introduced either manually or automated in the additive manufacturing system through a powder unit opening, which may be formed at a lateral side of the additive manufacturing system. The powder unit may comprise a fresh powder container in which the fresh material powder is stored in sufficient quantity for an intended product, a powder application container in which the component is built up in layers and an excess container in which the excess powder and splashes after the SLM process is collected. The powder unit may be engaged with the manufacturing chamber bottom plate through an opening, which can be formed in the bottom of the rotary manufacturing unit. Accordingly, the powder unit may be correctly positioned at the rotary manufacturing unit without any adjustment step.

In an example, the powder unit and/or at least one of the containers comprises a powder lid. In other words, the powder unit as a single container or at least one, preferably each of three individual containers of the powder unit may have a lid. The lid may be manually or automatically put on each container after an inertisation of the powder material and manually or automatically removed from each container inside the additive manufacturing system during a SLM process. For an automatic and easier handling of the container lid a lid support element such as a mini crane may be provided inside the additive manufacturing system. The lid support element may also be used to assist a handling of heavy manufacturing plates or workpieces in a protective or low pressure atmosphere. The inertisation can be understood in that undesired gas such as oxygen is drawn out from the powder unit by an evacuation means, subsequently an inert gas is provided to ensure a very low oxygen content for manufacturing a high-qualitative product.

Accordingly, the powder, especially the fresh powder can be prevented from being contaminated by smoke, splashes, vapor or particularly oxygen.

In an example, the doctor blade is configured to supply powder from the fresh powder container to the powder application container and from the powder application container to the excess container. In other words, the containers of the powder unit arranged such that the powder application container is located between the fresh powder container and the excess container. Accordingly, if the doctor blade may move from the fresh powder container to the excess container, the metal powder may be supplied firstly to the powder application container and the excess powder and splashes from the powder application container can be removed to the excess container.

In an example, the powder unit further comprises a powder unit supporting plate and a driving means. The powder unit supporting plate is configured to support the powder unit and the driving means is configured to the drive powder unit supporting plate, accordingly the powder unit between a powder application position and a container exchange position. The powder unit supporting plate may provide space for the e.g. three containers of the powder unit and support a vertical movement of the powder unit relative to the rotary manufacturing unit. The vertical movement can be realized by the driving means and a lifting guide, which may connect the powder unit supporting plate and the rotary manufacturing unit. By driving the powder unit supporting plate, accordingly, the powder unit is elevated to the rotary manufacturing unit and the powder unit may come in the powder application position in which the powder unit engages with and/or is pressed against the opening of the rotary manufacturing unit and/or the manufacturing chamber bottom plate. Further, the powder unit supporting plate may also be decreased away from the rotary manufacturing unit by the driving means and the powder unit may come in the container exchange position in which either the containers can be changed through a lateral side of the additive manufacturing system, a maintenance work to the powder unit can be performed or the rotary manufacturing unit can be rotated. The driving means and in particular the lifting guide may also be used for a vertical movement of a manufacturing plate.

In an example, the fresh powder container and the powder application container each comprises a container bottom plate and a lifting means. The lifting means is configured to lift the container bottom plate within the respective container. The fresh powder container and the powder application container of the powder unit may each comprise a container bottom plate, which seals inside of each container to the outside. On the container bottom plate, a zero point clamping system may be integrated, which allows a fast, easy and accurate replacement of a substrate. Each container bottom plate may be engaged with a lifting means to move the container bottom plate vertically relative to the corresponding container. The lifting means may be fixedly attached to a bottom of the additive manufacturing system or be rotated together with the respective container to ensure a reliable engagement between the container and the lifting means despite repeated rotations of the powder unit. When the rotary manufacturing unit is rotated e.g. <NUM> degrees before or after a production cycle, i.e. the rotary manufacturing unit does not rotate during a SLM process, the lifting means may be in a retracted position and have no engagement with the container bottom plate ensuring a collision-free rotation. In an example, the excess container may also comprise a container bottom plate and a lifting means to facilitate a removal of the excess powder and splashes out of the excess container.

In an example, the lifting means comprises a lifting rod and a lifting interface. The lifting interface comprises a base plate and an intermediate plate arranged between the base plate and the container bottom plate. The base plate is mounted on the lifting rod. The intermediate plate may be engaged with the base plate by a zero point clamping system allowing a fast, easy and accurate positioning of the intermediate plate. Further, the container bottom plate may be connected to the intermediate plate by a three-point support system. Hence, the container bottom plate may move vertically in accordance with the movement of the lifting rod.

In an example, the intermediate plate is configured to heat the container bottom plate and the base plate is configured to prevent heat conduction from the intermediate plate into the direction of the lifting rod. The intermediate plate may function as a heating plate to heat an engaged component. Preferably, the intermediate plate, in other words heating plate, may heat the container bottom plate, in particular the substrate, up to several hundred °C to increase an efficiency and a quality of the SLM process.

Heat conduction from the intermediate plate may be obstructed in direction to the lifting rod or a container bottom side by cooling the base plate. Due to a high temperature inside the powder application container, the lifting means providing the zero point clamping system and/or the three-point support system, which are based on an accurate force-fitting or form-fitting engagement, may be affected. Hence, the base plate may be cooled by means of a cooling medium such as water to prevent heat conduction in direction to bottom side of the container.

In an example, the fresh powder container and the powder application container each comprise at least a fixing element having a spring-biased pin and a clamping ball. The fixing element is configured to fixedly hold the container bottom plate in the container exchange position. The container bottom plate may be differently positioned inside the fresh powder container and the powder application container according to the process step. When removing the powder unit out of the additive manufacturing system after finishing the SLM process, it is important to fix the container bottom plate to provide a smooth transfer to a post-processing system such as treatment of the metallic materials or the substrate.

The fixing element may be arranged at an undermost side of each container and at each edge of the undermost side. The spring-biased pin and the clamping ball may be inserted into both the intermediate plate and the container bottom plate and fixedly hold them together. Accordingly, the powder unit may be securely transferred from the additive manufacturing system to the post-processing system even with a reversed holding of the powder unit. According to the invention, the manufacturing chamber bottom plate comprises a sealing interface configured to hermetically seal the powder unit to the manufacturing chamber. The sealing interface is adapted to remove residual metallic powders on the manufacturing chamber bottom plate. To realize a hermetical engagement between the manufacturing chamber and the powder unit, a sealing interface is provided between the manufacturing chamber bottom plate and an opening of the powder unit.

In an example, between the opening of the powder unit and the sealing interface a peripheral groove may be provided. The peripheral groove may surround the opening of the powder unit. The sealing interface may further comprise at least one suction port connected to the peripheral groove to remove the residual metallic powder on the bottom of the manufacturing unit. Accordingly, the residual metallic powder material may be collected in the peripheral groove during the manufacturing process and removed via the suction port in order to prevent a spreading of the residual metallic powder when disengaging the container unit after a manufacturing process. The sealing interface is particularly advantageous, since it may be not only adapted to a rotary manufacturing unit but also to a conventional manufacturing system, in which a powder unit engages with the additive manufacturing chamber.

In an example, additive manufacturing system further comprises an irradiation unit configured to provide irradiation for irradiating the powder layer. The irradiation unit may comprise at least one laser and at least an irradiation deflection unit configured to guide irradiation from an irradiation source to the powder layer. In a simple form, the additive manufacturing system may have at least one irradiation deflection unit, but can be extended up to four and more irradiation deflection units for a highly productive design. The irradiation source may be housed in an air-conditioned control cabinet and the irradiation may be guided, for example in an optical fiber cable to the corresponding irradiation deflection unit such that the irradiation can be applied on the substrate. The irradiation unit may be separated from the manufacturing chamber via the openable cover and the irradiation window. In other words, the irradiation may pass to the powder layer through the irradiation window in order to separate the irradiation unit from the dusty process environment. Consequently, the maintenance and cleaning effort for an operator may be reduced.

In an example, the additive manufacturing system further comprises an evacuation unit configured to reduce a pressure in the manufacturing chamber. The evacuation unit allows drawing out undesired gas such as oxygen from the manufacturing chamber and the powder unit and maintaining vacuum or providing an inert gas to ensure a very low oxygen content for manufacturing a high-qualitative product.

In an example, the additive manufacturing system further comprises a heating unit configured to heat the manufacturing chamber. Particularly, the heating unit may heat the substrate to <NUM>, or even to <NUM> - <NUM> at which the SLM process is performed. The heated substrate may provide lower temperature gradients during a cooling step of the layered product, which can reduce a residual stress of the product.

In an example, the rotary manufacturing unit and the powder unit are arranged in a base portion and the irradiation unit is arranged in an optic portion, wherein the base portion and the optic portion are releasably mounted to each other. The optic portion can be pre-assembled parallel to the structure of the base portion with all optical components. The optical components may be integrated by means of an optic assembly board in the optic portion. The optic assembly board may serve for the integration and arrangement of the irradiation deflection unit. By a simple change of the optic assembly board with different irradiation deflection units, the additive manufacturing system can be modular.

In an example, the base portion and/or the optic portion are made of mineral cast. The use of mineral cast may provide high vibration damping, thermal inertia and an ideal machine base for high precision optical machines.

In an example, the additive manufacturing may further comprise two protective covers fixedly arranged at the optic portion above each manufacturing chamber. The protective covers may not rotate while the manufacturing chambers rotate into the first and second position. In other words, the manufacturing chambers may rotate out of the first protective cover and the second protective cover and rotate in the second protective cover and the first protective cover or respectively. The protective covers may be opened for preparing a SLM process or executing maintenance works.

According to the invention, also a method for applying a powder material to a substrate is presented, according to claim <NUM>.

The rotary manufacturing unit does not rotate during a SLM process, but only the doctor blade moves in the respective manufacturing chamber to supply fresh powder from a fresh powder container to the respective substrate.

In an example, the method further comprises between step a) and step b) at least one of the following steps:.

After a SLM process for example in the first manufacturing chamber, the rotary manufacturing unit may rotate <NUM> degrees such that the first manufacturing chamber with a completely layered product can rotate into the second position. In the second position, the second manufacturing chamber can be positioned for irradiating the powder layer on the second substrate and the first manufacturing chamber can be positioned for allowing maintenance works and removal of the layered product. After completing a SLM process in the second manufacturing chamber, the rotary manufacturing unit may rotate and a subsequent SLM process can follow in the first manufacturing chamber. In this way a continuous SLM process can be realized.

The additive manufacturing system according to the invention has been designed for industrial use and can be operated in a normal production environment. The system and its interfaces are adapted to allow safer operation in handling metal powders without personal protective equipment. In addition, the additive manufacturing system is configured to avoid direct powder contact during operation of the system. The additive manufacturing system further allows a robust and precise construction.

It shall be understood that the additive manufacturing system and the method for apply a powder material to a substrate according to the independent claims have similar and/or identical preferred embodiments, in particular, as defined in the dependent claims. It shall be understood further that a preferred embodiment of the invention can also be any combination of the dependent claims with the respective independent claim.

These and other aspects of the present invention will become apparent from and be elucidated with refer to the embodiments described hereinafter.

Exemplary embodiments of the invention will be described in the following with reference to the accompanying drawings:.

<FIG> shows schematically and exemplary a rotary manufacturing unit <NUM> of an additive manufacturing system <NUM> according to the invention for applying a powder layer to a substrate <NUM>. The rotary manufacturing unit <NUM> comprises a first manufacturing chamber M and a second manufacturing chamber M. The first manufacturing chamber M and the second manufacturing chamber M are essentially of similar size and/or shape.

Further, the first manufacturing chamber M and the second manufacturing chamber M each comprise a detector window 20a, through which the laser melting process can be monitored by means of various imaging sensors <NUM> (see <FIG>).

For an optimal laser melting process, it might be necessary to remove smokes, splashes and particles from the irradiation zone by means of a laminar gas flow over the powder bed or substrate <NUM>. Accordingly, a ventilation inlet 20b and a ventilation outlet 20c are integrated in each manufacturing chamber M of the rotary manufacturing unit <NUM> along the irradiation zone. The gas flow within the manufacturing chambers M can be conducted, for example, by means of attachable gas flow nozzles 20e (see also <FIG>).

Both manufacturing chambers M can be hermetically sealed by means of an openable cover <NUM> such that a protective atmosphere can be built up in the manufacturing chambers M (see also <FIG>). In particular, a seal 20d arranged between the rotary manufacturing unit <NUM> and the openable covers <NUM> allows generating a vacuum and flowing an inert gas in the manufacturing chamber M without leakage.

The openable cover <NUM> is formed circular to be fitted to the rotary manufacturing unit <NUM> and arranged symmetrically at the rotary manufacturing unit <NUM>. In addition, each manufacturing chamber M comprises an opening formed in the bottom of the rotary manufacturing unit <NUM>. Through the opening, a powder unit P can be engaged with the rotary manufacturing unit <NUM>.

<FIG> shows schematically and exemplary an embodiment of the rotary manufacturing unit <NUM> engaged with the powder unit P of the additive manufacturing system <NUM> according to the invention. On the lower side of the rotary manufacturing unit <NUM>, two powder units P are symmetrically arranged in the opening of the rotary manufacturing unit <NUM>.

As shown in <FIG>, each powder unit P may comprise e.g. three containers. A fresh powder container <NUM> stores fresh powder, a powder application container <NUM> allows forming a powder layer on a substrate <NUM>, and an excess container <NUM> collects excess powder and splashes after applying the powder layer to the substrate <NUM>.

Each powder unit P is disposed on a powder unit supporting plate <NUM>, which can be moved vertically between a powder application position and container exchange position by means of a driving means <NUM>. The driving means <NUM> is mounted between the lower side of the rotary manufacturing unit <NUM> and the powder unit supporting plate <NUM> to raise or lower the powder unit supporting plate <NUM>, accordingly the powder unit P. When lifting the powder unit supporting plate <NUM> by the driving means <NUM>, the powder unit P can be positioned accurately and sealed hermetically by a manufacturing chamber bottom plate <NUM>, by which the powder unit P is engaged with the rotary manufacturing unit <NUM> (see also <FIG>). For example, four lifting guides <NUM> connect the rotary manufacturing unit <NUM> and the powder unit supporting plate <NUM> using lifting guide bushings 23b to support a vertical movement of the powder unit supporting plate <NUM>. In the lowered position, i.e. container exchange position, the powder unit P can be exchanged. The powder unit P can also comprise a handle <NUM> for automatic insertion and removal of the powder unit.

<FIG> shows schematically and exemplary a cross-sectional view of the powder unit P engaged with the rotary manufacturing unit <NUM>. The fresh powder container <NUM> and the powder application container <NUM> have an integrated container bottom plate <NUM>, which seals the interior of the powder containers to the outside. On the container bottom plate <NUM>, a zero point clamping system 80a is integrated, which allows a fast, easy and accurate replacement of substrate <NUM>.

On each bottom side of the fresh powder container <NUM> and the powder application container <NUM>, a lifting means <NUM> is attached (see also <FIG>). The lifting means <NUM> may be rotated together with the respective container, or be fixed at the bottom of the additive manufacturing system <NUM>. The lifting means <NUM> comprises a lifting rod 11a and a container bottom plate interface 11b and moves the container bottom plate <NUM> vertically within the containers <NUM>, <NUM>. When the engaged rotary manufacturing unit <NUM> is rotated <NUM> degrees before or after a production cycle, the lifting means <NUM> moves to a retracted position and has no engagement with the container bottom plate <NUM>, which ensures a collision-free rotation of the rotary manufacturing unit <NUM>. Meanwhile, the container bottom plate <NUM> is held in place by the integrated clamping unit 80b, when the lifting means moves into the retracted position.

During a SLM process in one of the manufacturing chambers M, the container bottom plate <NUM> of the powder application container <NUM> is coated in layers by means of a doctor blade <NUM> attached to a doctor blade body <NUM>. The doctor blade <NUM> supplies powder from the fresh powder container <NUM> to the powder application container <NUM> and from the powder application container <NUM> to the excess container <NUM> through its linear movement guided by a doctor blade rail <NUM>. The movement of the doctor blade <NUM> is supported by a doctor blade drive means <NUM> connected to the doctor blade body <NUM>.

On the manufacturing chamber bottom plate <NUM>, a guiding unit <NUM> is mounted, which serves as an accurate reference during movement of the doctor blade <NUM>. The guiding unit <NUM> is easy to replace in case of wear. Therefore, the doctor blade <NUM> can move rapidly back to the starting position and the coated layer is ready to be exposed by means of an irradiation deflection unit <NUM>, <NUM> (see also <FIG>) according to product specifications. Subsequently, the required material powder for the next layer is supplied by the lifting means <NUM> of the fresh powder container <NUM> in order to spread the powder onto the substrate <NUM>. At the same time, excess powder is swept by the doctor blade <NUM> into the excess container <NUM>. Coating and irradiation process is repeated until the entire component has been built up in layers.

<FIG> show schematically and exemplary an embodiment of the additive manufacturing system <NUM>. The additive manufacturing system <NUM> comprises a base portion <NUM> and an optic portion <NUM>, wherein the base portion <NUM> and the optic portion <NUM> are releasably mounted to each other. The base portion <NUM> and/or the optic portion <NUM> are made of mineral cast. Mineral cast allows high vibration damping and thermal stability, and is therefore an ideal machine base for precision optical machines.

In the base portion <NUM>, the rotary manufacturing unit <NUM> and the powder unit P are arranged and in the optic portion <NUM> an irradiation unit is arranged. The rotary manufacturing unit <NUM> in the base portion <NUM> can be continuously rotated in the same direction or can be rotated <NUM> degrees alternating to the left or right by means of a rotary drive <NUM> and a pivot bearing ring gear <NUM>. On the base portion <NUM>, the optic portion <NUM> is positioned after an integration of the complete rotary manufacturing unit <NUM> engaged with the powder unit P. The optic portion <NUM> can be pre-assembled with all optic components parallel to the assembly of the base portion <NUM>. The optic components are integrated in the optic portion <NUM> using an optic assembly board <NUM>. The optic assembly board <NUM> essentially serves for the integration and arrangement of the irradiation deflection unit <NUM>, <NUM>. The irradiation deflection unit <NUM>, <NUM> guides irradiation from an irradiation source to the powder layer.

The additive manufacturing system <NUM> can be modular by a simple change of the optic assembly board <NUM> with different irradiation deflection units. In a simple form, the additive manufacturing system <NUM> has at least one irradiation deflection unit <NUM> but can be extended up to four irradiation deflection units for a highly productive design.

The irradiation source may be housed in an air-conditioned control cabinet <NUM> and the irradiation is guided by an optical fiber cable to the corresponding irradiation deflection unit <NUM>, <NUM>. The irradiation unit <NUM>, <NUM> is separated from the manufacturing chamber M via the openable cover <NUM> and the irradiation window <NUM> such that the irradiation passes to the powder layer / substrate <NUM> through the irradiation window <NUM> without affecting the irradiation unit <NUM>, <NUM> from the dusty process environment, such as smoke, splashes, particles etc..

The optic portion <NUM> can be provided additionally with a protective cover <NUM>, a monitor window <NUM>, an access means <NUM>, a powder suction unit <NUM> and an openable cover guide unit <NUM>, <NUM>. The protective cover <NUM> can be opened such that an operator may have an access inside of the additive manufacturing system <NUM> via the access means <NUM> for maintaining (cleaning, replacing, etc.) the doctor blade <NUM> which can be monitored through the monitor window <NUM>. Further, the powder suction unit <NUM> removes the powder from a completed layered product and the openable cover guide unit <NUM>, <NUM> support the openable cover <NUM> for an easy opening and closing. The openable cover <NUM> may be opened in a vertical direction by means of the cover guide unit <NUM>, <NUM> or may be a flap to be folded up and down to be opened and closed.

In the base portion <NUM> the powder unit P can be inserted to the additive manufacturing system <NUM> either manually or automated through a powder unit opening 10b arranged at a front surface or at a lateral surface of the base portion <NUM>. The powder unit P may be inserted into the additive manufacturing system <NUM> or extracted out of the additive manufacturing system <NUM>, for example, by means of a powder unit conveying rail. The fresh powder container <NUM> can comprise a lid <NUM>, which can be closed after the SLM process, removed after a maintenance work via the access means <NUM> and stored in a storing position in the optic portion <NUM>. The container lid <NUM> may be also automatically opened and closed by means of a lid support element such as a mini crane, which may be provided inside the additive manufacturing system <NUM>.

The powder unit opening 10b may have two door leaves, which may be opened like a gate. Additionally, as soon as an opening angle of the two door leaves exceeds about <NUM>°, the door leaves can be at least partially slid inside a recess or a slit in or under the base portion <NUM>.

<FIG> shows schematically and exemplary an embodiment of an automated additive manufacturing system according to the invention for applying a powder layer to a substrate. In the automated additive manufacturing system, a plurality of additive manufacturing systems <NUM> are arranged in series.

In case of a material change or an automatic removal of the powder unit P, the powder unit supporting plate <NUM> is lowered into the powder change position and the powder unit P can be removed through the powder unit opening 10b and replaced by newly prepared powder containers with an automation device <NUM>. Thus, the automation device <NUM> allows an industrial mass production. The fresh powder container <NUM> and the excess container <NUM> can be transported via the automation device <NUM> to a powder extraction and powder preparation unit <NUM>. In the powder preparation unit <NUM>, remaining powder in the excess container <NUM> and the fresh powder container <NUM> is removed and fresh powder 1a is supplied into the fresh powder container <NUM> for an upcoming use in the additive manufacturing system <NUM>.

Meanwhile, the powder application container <NUM> is transported to a substrate preparation unit <NUM> by means of the automation device <NUM>. The substrate <NUM> with a product 1b is automatically removed from the powder application container <NUM> and the product 1b can be separated from the substrate <NUM>. The substrate <NUM> can be prepared in the substrate preparation unit <NUM> and positioned in the powder application container <NUM> and be then provided to the additive manufacturing system <NUM> again.

The additive manufacturing system <NUM> is very easy and modern to operate and allows an individual use for an operator. Accordingly, a multi-touch display can be integrated and user profiles and user views can be created, for example on a smartphone or a Head Up Display, in accordance with the operator authorization levels. In the additive manufacturing system <NUM> according to the invention, desired views of the process, control programs and/or process data can be displayed on the display in a desired size by e.g. the imaging sensors <NUM> integrated in the additive manufacturing system <NUM>.

<FIG> shows a schematic overview of steps of a method for applying a powder material to a substrate <NUM>.

The first manufacturing chamber M comprises a first openable cover <NUM> and the second manufacturing chamber M comprises a second openable cover <NUM>.

The first manufacturing chamber M comprises a first doctor blade <NUM> configured to apply a powder layer on a first substrate <NUM> and the second manufacturing chamber M comprises a second doctor blade <NUM> configured to apply a powder layer on a second substrate <NUM>.

The method for applying a powder material to a substrate <NUM> may comprise further steps (not shown):.

The test layer and the SLM process can be qualitatively controlled by an operator through the monitor window <NUM>. As soon as the test layer on the substrate <NUM> of the powder application container <NUM> is satisfactory, the openable cover <NUM> can be lowered by means of an openable cover guide unit <NUM> and hermetically seals the manufacturing chamber M.

During the SLM process, the substrate <NUM> of the powder application container <NUM> is coated in layers by means of the doctor blade <NUM>. The excess powder is swept by the doctor blade <NUM> into an excess container <NUM>. Subsequently, the doctor blade <NUM> moves rapidly back to a starting position and the powder layer on the substrate <NUM> is exposed according to the component specification to the irradiation deflection units <NUM>, <NUM>. At the same time, the required material powder for a subsequent layer is supplied by the lifting means <NUM> of the fresh powder container <NUM> and the coating and irradiation process is repeated until the entire product has been built up in layers.

<FIG> shows schematically and exemplary a cross-sectional view of the powder unit P engaged with the manufacturing chamber M. For preparing a manufacturing process, the powder unit P is inserted into the additive manufacturing system <NUM> and moved vertically to engage with the manufacturing chamber bottom plate <NUM> by the lifting means <NUM> (see also <FIG>). To realize a hermetical engagement between the manufacturing chamber M and the powder unit P, a sealing interface <NUM> is provided between the manufacturing chamber bottom plate <NUM> and an opening of the powder unit P. The sealing interface <NUM> comprises a peripheral groove <NUM> surrounding the opening of the powder unit P.

Further, the sealing interface <NUM> comprises at least one suction port <NUM> connected to the peripheral groove <NUM> to remove the residual metallic powder. Accordingly, the residual metallic powder material is collected in the peripheral groove <NUM> during the manufacturing process and removed via a suction port <NUM> in order to prevent a spreading of the residual metallic powder when disengaging the powder unit P after a manufacturing process. In addition to the suction port <NUM>, a temperature control element may be integrated in the sealing interface <NUM> to avoid any expansion or distortion of the sealing interface <NUM>.

As show in <FIG>, the powder application container <NUM> and the excess container <NUM> may be integrated in a transportable container P'. In other words, the transportable container P' may be divided into two containers separated by a wall, wherein one container <NUM> is adapted to apply a powder layer to a substrate <NUM> and the other container <NUM> is adapted to collect excess powder after applying the powder layer to the substrate <NUM>. The fresh powder container <NUM> may be also configured to be transportable. By providing a transportable powder unit P, the additive manufacturing system <NUM> may be operated in a fully automated process. The transportable powder unit according to the invention is particularly advantageous, since it is not only adapted to a rotary manufacturing unit but also to a conventional manufacturing system, in which the powder unit engages with an additive manufacturing chamber.

The powder application container <NUM> comprises a gas-tight container lid <NUM> (see also <FIG>), a container bottom plate <NUM>, which is the substrate <NUM> in the case of the powder application container <NUM>, an intermediate plate <NUM>, which can be a heating plate in the case of the powder application container <NUM>, and a lifting means <NUM>. The lifting means <NUM> comprises a base plate <NUM> and at least one lifting rod 11a. The heating plate <NUM> is engaged with the base plate <NUM> to enable a vertical movement of the substrate <NUM> connected to the heating plate inside the powder application container <NUM>. The base plate <NUM> may control a heat conduction resulting from the heating plate <NUM>, particularly in the direction to a bottom side of the powder application container <NUM>. Accordingly, the lifting rod 11a comprises an inlet and an outlet port for a cooling medium to provide a liquid-cooled base plate <NUM>. Hereinafter each component of the powder application container <NUM> is detailed described.

The powder unit P comprises a fresh powder container <NUM>, a powder application container <NUM> and an excess container <NUM>, wherein the powder application container <NUM> and the excess container <NUM> may be integrated together in a transportable container P'. The volume ratio of the powder application container <NUM> and the excess container <NUM> may <NUM>:<NUM>. Yet, the volume of the powder application container <NUM> may be preferably lager than that of the excess container <NUM>, and more preferably, the volume ratio of the powder application container <NUM> and the excess container <NUM> may be <NUM>:<NUM>.

The transportable container P' may comprise rounded edges allowing an ergonomic handling of the container P'. Further, a wall thickness of the transportable container may be adapted such that no deformation occurs even at a pressure difference of <NUM> bar between an outer wall and an inner wall of the container.

<FIG> show an enlarged schematic view of an engagement of the substrate <NUM>, the heating plate <NUM> and the liquid-cooled base plate <NUM>. At an underside of the substrate <NUM> at least three engaging elements <NUM> protruding from the underside of the substrate <NUM> in direction to the heating plate <NUM> are arranged to bring the substrate <NUM> on the heating plate <NUM> through a three-point support system.

The intermediate plate <NUM> arranged between the container bottom plate (here, substrate <NUM>) and the base plate <NUM> can be a heating plate. The heating plate <NUM> may comprises ceramic heating elements, which is isolated in a downward direction by an isolating layer to conduct heat only to the substrate <NUM> in an upward direction of the powder unit P and avoid heat conduction in an opposite (downward) direction. By means of the heating plate <NUM>, the substrate <NUM> may be heated up to several hundred °C. Hence, the substrate <NUM> may not be directly connected to a heating source.

Further, at each edge of the heating plate <NUM> a through-hole <NUM> is provided, through which a fixing element <NUM> arranged on an undermost bottom of the powder application container <NUM> can be inserted and lock the heating plate <NUM> and the substrate <NUM> together (see <FIG>). The insertion of the fixing element <NUM> through the through-hole <NUM> may be performed in a contactless manner. Additionally on an underside of the heating plate <NUM> a fixing pin <NUM> is formed for fixedly engaging the base plate <NUM> of the lifting means <NUM> by a zero-point clamping system 80a.

The base plate <NUM> of the lifting means <NUM> may be cooled by a cooling medium such as water to obstruct heat conduction from the heating plate <NUM> downwardly, in the direction to the lifting rod 11a. The liquid-cooled base plate <NUM> constitutes an interface between the lifting rod 11a and the heating plate <NUM>, and consequently the substrate <NUM>. The liquid-cooled base plate <NUM> comprises a recess <NUM> to receive the fixing pin <NUM>, preferably in the center of the base plate <NUM> to provide a force- and form-fitting connection with the heating plate <NUM>. Inside the liquid-cooled base plate <NUM> liquid channels may be arranged, in which the cooling medium is introduced to prevent heat conduction from the heating plate <NUM> and a subsequent thermal elongation or distortion of the components of the lifting means <NUM>, which are precisely manufactured to fit each other.

To allow an oxygen-free and contamination-free transport of the metallic powder material, the powder unit P may be adapted to be secured in a different processing steps and/or conditions. For this purpose, the fixing element <NUM> comprising a spring-biased pin <NUM> and at least one clamping ball <NUM> is arranged at the undermost bottom of each container. The fixing element <NUM> secures a correct positioning of the substrate <NUM> either in a powder application (extended) position, in which the substrate <NUM> is separated from the fixing element <NUM>, or in a container exchange (retracted) position, in which the substrate <NUM> is fixedly held by the fixing element <NUM>.

During an additive manufacturing process the substrate <NUM> is connected to the base plate <NUM> of the lifting means <NUM> via the heating plate <NUM>, but the substrate <NUM> is not engaged with the fixing element <NUM>. In other words, the spring-biased pin <NUM> is configured not to press the clamping ball <NUM> into the clamping recess <NUM> of the substrate <NUM> as long as the substrate <NUM> is in the powder application position (see <FIG>).

In case of an extraction of the powder unit P out of the additive manufacturing system <NUM>, the fixing element <NUM> is inserted to the through-hole <NUM> of the heating plate <NUM> and fixedly engages with the substrate <NUM>, as shown in <FIG>. The spring-biased pin <NUM> may be pressed into the substrate <NUM> by an external force exerted from an outside to an inside the powder application container <NUM>. Meanwhile, the clamping ball <NUM> may be locked at the clamping recess <NUM> in the substrate <NUM>. Accordingly, the clamping element <NUM> may fixedly hold the heating plate <NUM> and the substrate <NUM> does not move in the container exchange position.

<FIG> shows schematically the fresh powder container <NUM>. The fresh powder container <NUM> comprises a transportable container P' having a container bottom plate <NUM> connected to the lifting means <NUM> by the zero point clamping system 80a. The container bottom plate <NUM> may be also fixedly engaged with the fixing element <NUM>, when extracting the fresh powder container <NUM> out of the additive manufacturing system <NUM>, as explained above.

The container lid <NUM> must be hermetically sealed so that no ambient gas can penetrate into the container or protective gas can escape out of the container. Hence, an inert gas atmosphere of argon or nitrogen in the powder application container <NUM> and in the powder storage container can be maintained in order to prevent a reaction between the metallic powder material and oxygen.

Furthermore, as shown in <FIG>, the container lid <NUM> comprises an exchange port <NUM> configured to allow a controlled discharging of the metallic powder from the container sealed with the container lid <NUM>. A suction tube may be connected to the exchange port <NUM> to remove the metallic powder out of the container. At the same time, an inert gas may be inserted into the container with the same volume of the removed powder. Accordingly, any vacuum or low pressure due to the discharge of powder may be avoided.

Claim 1:
An additive manufacturing system (<NUM>) suitable for selective laser melting for applying a powder layer to a substrate (<NUM>), comprising a rotary manufacturing unit (<NUM>) and at least a powder unit (P) configured to store fresh powder, to apply a powder layer to the substrate (<NUM>), and to receive excess powder,
wherein the rotary manufacturing unit (<NUM>) comprises a first manufacturing chamber (M) and a second manufacturing chamber (M),
wherein the first manufacturing chamber (M) comprises a first openable cover (<NUM>) and the second manufacturing chamber (M) comprises a second openable cover (<NUM>),
wherein the first manufacturing chamber (M) comprises a first doctor blade (<NUM>) configured to apply a powder layer on a first substrate (<NUM>),
wherein the second manufacturing chamber (M) comprises a second doctor blade (<NUM>) configured to apply a powder layer on a second substrate (<NUM>),
wherein the first manufacturing chamber (M) and the second manufacturing chamber (M) comprises an opening formed in the bottom of the rotary manufacturing unit (<NUM>) through which the powder unit (P) can be engaged with the rotary manufacturing unit (<NUM>),
wherein a manufacturing chamber bottom plate (<NUM>) of each manufacturing chamber (M) comprises a sealing interface (<NUM>) configured to hermetically seal the powder unit (P) to the manufacturing chamber (M),
wherein the rotary manufacturing unit (<NUM>) is configured to be rotatable into a first position in which the first manufacturing chamber (M) is positioned for irradiating the powder layer on the first substrate (<NUM>) and the second manufacturing chamber (M) is positioned for enabling an opening of the second cover (<NUM>), and
into a second position in which the second manufacturing chamber (M) is positioned for irradiating the powder layer on the second substrate (<NUM>) and the first manufacturing chamber (M) is positioned for enabling an opening of the first cover (<NUM>).