Patent Description:
Application units for applying build material, in particular powdery build material, in a build plane of the process chamber of apparatuses for additively manufacturing three-dimensional objects are generally known from prior art.

At least in powder bed based additive manufacturing processes, i.e. processes in which material is layerwise applied in a powder bed and selectively consolidated to form the three-dimensional object, application units are used to layerwise apply the build material. Known application units usually comprise an application element that is carried by an application element carrier, e.g. fixedly mounted on a frame-like structure. The application element may, inter alia, be built as a blade or a rake or the like that is adapted to convey build material and distribute the build material in the build plane.

For example, it is possible to use the application unit to convey build material from a dose plane in which the build material is provided to a build plane in which the build material is (evenly) distributed in advance to a consolidation process. Further, it is known from prior art that different application elements, in particular application elements built from different materials can be used dependent on the additive manufacturing process, e.g. dependent on the type of build material that is used. Inter alia, it is possible to use steel tools or flexible rubber profiles or carbon brushes dependent on the additive manufacturing process. However, the different application elements may lead to negative impacts on the additive manufacturing process.

For example, it is possible that fragments of carbon brushes or even complete carbon bristles are removed from the application element during an application process. Further, small parts of rubber from a rubber profile used as application element can be removed during an application process step that may contaminate the build material. On the other side, rigid tools, such as steel tools may apply pressure on a region of the object that protrudes the actual layer of build material leading to a contact between the application element and the object that may cause damage to the object and the application element, e.g. in damage to a filigree portion of the object.

Application units with application elements are known from the documents <CIT>, <CIT>, <CIT>, <CIT> and <CIT>. Further, from the document <CIT> doctor blade holder that is adapted to accommodate a doctor blade in a slot in the holder and is provided with a resilient means at the base of the slot is known.

It is an object of the present invention to provide an improved application unit, wherein in particular negative influences on the additive manufacturing process are reduced or avoided.

The object is inventively achieved by an apparatus according to claim <NUM> and a method according to claim <NUM>.

Advantageous embodiments of the invention are subject to the dependent claims.

The application unit described herein is an application unit for an apparatus for additively manufacturing three-dimensional objects, e.g. technical components, by means of successive selective layerwise consolidation of layers of a powdered build material ("build material") which can be consolidated by means of an energy source, e.g. an energy beam, in particular a laser beam or an electron beam. A respective build material can be a metal, ceramic or polymer powder. A respective energy beam can be a laser beam or an electron beam. A respective apparatus can be an apparatus in which an application of build material and a consolidation of build material is performed separately, such as a selective laser sintering apparatus, a selective laser melting apparatus or a selective electron beam melting apparatus, for instance. Alternatively, the successive layerwise selective consolidation of build material may be performed via at least one binding material. The binding material may be applied with a corresponding application unit and, for example, irradiated with a suitable energy source, e.g. a UV light source.

The apparatus may comprise a number of functional units which are used during its operation. Exemplary functional units are a process chamber, an irradiation device which is adapted to selectively irradiate a build material layer disposed in the process chamber with at least one energy beam, and a stream generating device which is adapted to generate a gaseous fluid stream at least partly streaming through the process chamber with given streaming properties, e.g. a given streaming profile, streaming velocity, etc. The gaseous fluid stream is capable of being charged with non-consolidated particulate build material, particularly smoke or smoke residues generated during operation of the apparatus, while streaming through the process chamber. The gaseous fluid stream is typically inert, i.e. typically a stream of an inert gas, e.g. argon, nitrogen, carbon dioxide, etc..

As described before, the apparatus of claim <NUM> comprises an application unit for applying build material in a build plane of said apparatus, wherein the application unit comprises an application element carried by an application element carrier. Typically, the application element is used for conveying or distributing the build material in the build plane. Hence, the application unit moves the build material thereby, transmitting or applying a force on the build material to distribute the build material (evenly) in the build plane, wherein the application element protrudes from the application element carrier towards the build plane. The invention is based on the idea that the application element is coupled to the application element carrier via at least one deflection unit.

The deflection unit allows for deflecting the application element relative to the application element carrier, i.e. generating a relative movement between the application element and the application element carrier. Thus, dependent on the force that is applied on the application element, the application element can be moved relative to the application element carrier. Hence, it is ensured that the application element does not negatively influence the additive manufacturing process, e.g. by applying a force on the object that is above a defined threshold value that would lead to a damage of filigree parts of the object. For example, if the application element comes in contact with the object, the application element may deflect, i.e. move relative to the application element carrier, thereby reducing the force that is applied on the object. Therefore, it is possible to avoid excessive forces on the build material, the application element and the object.

Hence, it is possible to use a solid or rigid material for the application element, such as steel, for instance, wherein the wear of the application element is significantly reduced and a cross-contamination with e.g. carbon bristles or rubber parts, i.e. foreign particles, is avoided. Thus, the tool life of the application element is significantly increased and the risk of contamination is reduced.

As recited in claim <NUM>, the deflection unit comprises a spring element. The spring element is used to mount the application element to the application element carrier, e.g. mounting the spring element between the application element carrier and the application element. Dependent on the force acting on the application element, the spring element may, for example, be compressed, wherein the application element is moved relative to the application element carrier, in particular the application element is deflected with respect to the application element carrier. The spring element may be chosen dependent on the specific additive manufacturing process that is performed and in which the application element or the application unit, respectively, is used for applying build material. For example, different spring elements with different spring rates or build from different materials can be used, e.g. dependent on the type of build material or the structure of the object.

The spring element is built as or comprises a spring and/or an elastically deformable element. The spring element may, for example, be built as a coil spring or the spring element may comprise at least two coil springs via which the application element is mounted on the application element carrier. Thus, dependent on the force acting on the application element the one or more coil springs can be compressed to allow for a relative movement of the application element relative to the application element carrier. On the other hand, the deflection unit, in particular the spring element, may spring load the application element against the application element carrier.

It is also possible that the spring element may be built as or may comprise an elastically deformable element, such as a rubber element e.g. a rubber pad, via which the application element may be mounted on the application element carrier, in particular the elastically deformable element may be arranged between the application element and the application element carrier.

As described before, the application element is mounted to the application element carrier, wherein the deflection unit is arranged between the application element and the application element carrier. The application element is fastened against the application element carrier with the application unit acting as intermediate element. In other words, the application element may be mounted to the application element carrier, wherein the application element at least partially rests on the deflection unit. The deflection unit enables a movement of the application element relative to the application element carrier, e.g. in response to a force acting on the application element.

As recited in claim <NUM>, the application element is mounted to the application element carrier via a positive locking connection between the application element and the application element carrier, wherein the application element is spring-loaded against the application element carrier, via the deflection unit. According to the invention, a positive locking connection is provided between the application element and the application element carrier. The deflection unit may load the application element against the application element carrier, wherein the deflection unit may be compressed or otherwise deformed under a force acting on the application element, e.g. an excessive force above a defined threshold value resulting from a part of the object protruding the plane on which build material has to be applied.

Hence, it is particularly preferred that the deflection unit is adapted to enable a deflection of the application element relative to the application element carrier), preferably for enabling at least one of.

Thus, when the application element is moved across the build plane to convey and distribute the build material, (excessive) forces can be compensated, as the application element may deflect relative to the application element carrier and therefore, may evade the part of the object, e.g. protruding a planar surface of the object. Therefore, if a contact between the application element and a part of the object occurs, the application element may deflect avoiding damage to the application element and/or the object.

In an embodiment of the invention, the deflection unit may be adapted to enable a deflection of the application element for a deflection height. Thus, it is possible that the application element may be deflected for a defined deflection height compared to an initial position (application position) in which the application element is moved across the build plane in an application process. Therefore, the deflection unit provides a defined movement space in which the application element may be moved relative to the application element carrier, e.g. under force acting between application element and build material or object.

As recited in claim <NUM>, the application element comprises one surface inclined with respect to a build plane and/or the application element carrier. During an application process, the application element with the inclined surface is moved with the inclined surface facing in application direction. Hence, the application element may be moved more smoothly over irregularities in the build plane, such as a bump or an unevenness. The inclined surface facing the application direction changes the contact angle under which the application element comes in contact with the build material in that conveying the build material and distributing the build material is further improved.

Preferably, the application element may comprise a hull-shaped cross-section.

Thus, the cross-section of the application element may essentially be formed like the schematic hull of a ship with an inclined surface facing in application direction, for instance.

As described before, the application element may be built from different materials or comprise at least one portion build from a specific material, respectively. It is particularly preferred that the application element may comprise at least one portion build from a ceramic material and/or steel, preferably <NUM> and/or <NUM> and/or <NUM>, in particular a material related to the build material. Hence, the application element may be built from any arbitrary material, wherein, as described before, the application element may advantageously be built from a rigid material, as the deflection unit of the inventive application unit allows for a deflection, in particular a relative movement of the application element relative to the application element carrier. Thus, it is possible to use a rigid material, such as a ceramic or steel that allows for a long tool life and the possibility to precisely apply build material, as the application element itself does not deform during the application process.

It is particularly preferred that the application element is made from a material that is related to the build material, wherein preferably a new application element made from the same material that is used as build material is used in the additive manufacturing process. For example, if a metal powder is used as build material, the application element may be built from the same metal. Thus, a contamination of the build material with a different material can be avoided.

At least two of the application sub-elements that were described before can be built from the same material or from a different material. Thus, it is possible to choose the build material differently for the at least two different sub-elements, for example, if different regions of the build plane across which the application element is moved lead to a different wear behavior of the application element. For example, if a three-dimensional object is for the most part built in the center of the build plane, the central sub-elements of the application element can be built from a different material than application elements facing the edges of the build plane, for instance.

Further, the invention relates to a method for operating an apparatus for additively manufacturing three-dimensional objects by means of successive layerwise selective irradiation and consolidation of layers of a build material which can be consolidated by means of an energy source as recited in claim <NUM>.

All features, details and advantages described with respect to the apparatus are fully transferable to the method.

Exemplary embodiments of the invention are described with reference to the Fig. The Fig. are schematic diagrams, wherein.

<FIG> shows an application unit <NUM>, not forming part of the invention but useful to understand it, for applying, in particular powdery, build material in the build plane <NUM> in a process chamber <NUM> of an apparatus <NUM> for additively manufacturing three-dimensional objects. The application unit <NUM> comprises an application element <NUM> carried by an application element carrier <NUM>. The application element <NUM>, of course, protrudes from the application element carrier <NUM> in that the application element <NUM> can contact build material to convey and distribute build material. To apply build material the application element <NUM> is moved across the build plane <NUM> in an application direction <NUM> for layerwise applying build material in the build plane <NUM>, in particular conveying and distributing the build material in the build plane <NUM>.

In the application process forces act on the application element <NUM> as exemplarily indicated via arrow <NUM>. The application element <NUM> is mounted to the application element carrier <NUM> via a deflection unit <NUM> which is in this example built as an elastically deformable element, e.g. a rubber element. Of course, any other flexible or deformable material can be used to build the deflection unit <NUM>, for example a spring. To fasten the application element <NUM> to the application element carrier <NUM>, the application element carrier <NUM> comprises a fastening means <NUM>, e.g. a (threaded) metal plate, and a fastening element <NUM> e.g. a screw, via which the application element <NUM> can be fastened to the application element carrier <NUM>. As can be derived from <FIG>, the deflection unit <NUM> forms an intermediate element between the application element carrier <NUM> and the application element <NUM> allowing for a movement of the application element <NUM> relative to the application element carrier <NUM>.

In other words, if the force that acts / that is applied on the application element <NUM> in the direction that is indicated via arrow <NUM>, the application element <NUM> may deflect and move relative to the application element carrier <NUM> out of the initial position that is depicted in <FIG> (as indicated via arrow <NUM>). Hence, the application element <NUM> may be deflected for a deflection angle <NUM> out of the initial position that is depicted in <FIG>. Thus, the deflection unit <NUM> allows that the application element <NUM> may avoid a contact with the object or irregularities in the build plane <NUM>. Hence, errors or irregularities in the build plane <NUM> can be compensated. Therefore, it is possible that a rigid application element <NUM> is used, e.g. an application element <NUM> made from ceramic or steel, wherein the tool life of the application element <NUM> is significantly increased compared to application elements made from rubber or carbon bristles or the like.

Advantageously, the application element <NUM> may be made from the same material, in particular metal, that is used as build material in the additive manufacturing process. Thus, a contamination of the build material with foreign material is avoided.

<FIG> shows an application unit <NUM> according to an embodiment of the invention. The application unit <NUM> also comprises an application element <NUM> mounted on an application element carrier <NUM> which application element <NUM> can be moved across the build plane <NUM> for applying build material in the build plane <NUM>, as described before. The application unit <NUM> depicted in <FIG> comprises an application element <NUM> and an application element carrier <NUM> that provide a positive locking connection, e.g. via connecting means <NUM>. In this example, the application element <NUM> is loaded against the application element carrier <NUM>, in particular spring-loaded, via the deflection unit <NUM>.

Thus, the application element <NUM> is spring-loaded against the application element carrier <NUM> in the direction of the build plane <NUM>. In other words, forces acting on the application element <NUM> it during the additive manufacturing process, in particular an application process of build material, act on an inclined surface <NUM> that faces in application direction <NUM>. Therefore, the application element <NUM> is moved relative to the application element carrier <NUM> which movement, in particular which lateral movement is enabled by the deflection element <NUM>, which may be, inter alia, built as spring, in particular coil spring. In other words, the application element <NUM> maybe deflected out of the initial position that is depicted in <FIG> for a defined deflection height, as indicated via arrow <NUM>.

Therefore, (excessive) forces acting on the application element <NUM> lead to a relative movement between the application element <NUM> and the application element carrier <NUM> by compressing the deflection unit <NUM> and moving the application element <NUM> into the application element carrier <NUM>. To avoid build material from entering the application element carrier <NUM> sealing elements <NUM> are provided between the application element <NUM> and the application element carrier <NUM>.

<FIG> shows an application element <NUM> for an application unit <NUM>, for example one of the application units <NUM> from <FIG>, <FIG>. The application element <NUM> is comprised of individual application sub-elements <NUM> that are individually mounted via a corresponding fastening means <NUM> to an application element carrier <NUM>. Of course, it is also possible to provide a common application element <NUM> that is slotted into individual application segments or application sub-elements <NUM>.

The individual application sub-elements <NUM> are individually moveable, in particular deflectable, relative to the application element carrier <NUM>, as described before. The sub-elements <NUM> may individually be changed, e.g. loosened or attached to the application element carrier <NUM>. For example, if one of the application sub-elements <NUM> is worn, it can individually be exchanged and the other application sub-elements <NUM> can remain in position. It is also possible that deviations in the build plane <NUM> that occur only locally are compensated by a relative movement of only one application sub-element <NUM> instead of deflecting the entire application element <NUM>.

It is further possible that the individual application sub-elements <NUM> are made from the same or a different material. For example, application sub-elements <NUM> that are assigned to regions of the build plane <NUM> in which the wear on the application sub-elements <NUM> is higher, a different, in particular more rigid material can be used to increase the tool life.

Of course, all details, features and advantages described with respect to the individual embodiments can arbitrarily be exchanged, transferred and combined.

Claim 1:
Apparatus (<NUM>) for additively manufacturing three-dimensional objects by means of successive layerwise selective irradiation and consolidation of layers of a build material which can be consolidated by means of an energy source, the apparatus (<NUM>) comprising an application unit (<NUM>) for applying, in particular powdery, build material in a build plane (<NUM>) in a process chamber (<NUM>) of the apparatus (<NUM>), the application unit (<NUM>) comprising: an application element (<NUM>) comprising an inclined surface facing an application direction; an application element carrier (<NUM>) configured to carry the application element (<NUM>); and at least one deflection unit (<NUM>) coupling the application element (<NUM>) to the application element carrier (<NUM>), wherein the deflection unit (<NUM>) comprises a spring element, wherein the spring element is built as or comprises a spring and/or an elastically deformable element, wherein the application element (<NUM>) is fastened against the application element carrier (<NUM>) with the deflection unit (<NUM>) acting as intermediate element, characterized in that the application element (<NUM>) is mounted to the application element carrier (<NUM>) via a positive locking connection between the application element (<NUM>) and the application element carrier (<NUM>), wherein the application element (<NUM>) is spring loaded against the application element carrier (<NUM>) in the direction of the build plane, and wherein at least one sealing element (<NUM>) is disposed between the application element (<NUM>) and the application element carrier (<NUM>).