Process and production of three-dimensional objects by successive solidification of layers of a powdered building material

Abstract

Method for producing three-dimensional objects by successively solidifying layers of a powdered building material which can be solidified by means of electromagnetic radiation, in particular focused radiation such as laser radiation or electron radiation, at the locations corresponding to the respective cross-section of the objects, with the following features, - providing a construction device (1) which has a construction chamber (3) delimited by side walls (2) and a carrying device arranged within the construction chamber (3) so as to be height-adjustable for carrying the object, and - providing a coating device for applying layers of the building material to the support device or a previously formed layer and - Providing an irradiation device for irradiating layers of the building material at the locations corresponding to the respective cross-section of the object, - construction of a building cell (10) by generative construction of at least one building cell wall (11) which closely surrounds the object to be built either with at least one side wall (2) of the building chamber (3) or with further building cell wall sections and - Reduction of the coater volume and the area of ​​the coater application such that predominantly only the area within the construction cell (10) is coated, - characterized in that the contour of the construction cell (10) essentially follows the contour of the object to be built and the volume area lying inside the construction chamber (3) but outside the construction cell (10) is covered by a diaphragm provided with an opening, which is arranged below a coater (30).

Description

The invention relates to a method for producing three-dimensional objects by successively solidifying layers of a powdery building material which can be solidified by means of electromagnetic radiation, in particular bundled radiation such as laser radiation or electron radiation, at the locations corresponding to the respective cross section of the objects, having the further features of the preamble of claim 1.Such methods are known and are regularly carried out in laser sintering or melting installations and are referred to as laser sintering methods (SLS) or laser melting methods (SLM). The building devices used in such methods have a building chamber bounded by side walls, the bottom of the building chamber forming a support device for supporting the object to be manufactured. Furthermore, a coating device is provided, with which successive layers of the powdered building material can be applied to the carrying device or to a previously formed and already at least partially solidified layer. An irradiation device, for example a laser, is used for irradiating layers of the construction material at the locations corresponding to the respective cross section of the object, wherein the laser beam is guided via a scanner device, with which the beam impinging on the powder is guided and directed according to existing construction coordinates.In addition, it is fundamentally known to build up a construction chamber during the construction process, i.e. to pull up a wall in steps in addition to the object to be produced, which wall surrounds the actual object produced after completion of the construction process. This serves to be able to remove the object enclosed from the construction chamber and to allow it to cool.The methods known in the prior art are disadvantageous in that the powder application is always drawn over the entire surface of the existing construction chamber in order to construct the object and possibly walls surrounding the object. This is not only time consuming because the coating process takes up a not inconsiderable part of the total build time, but also disadvantageous with regard to the amount of powder required for each coating operation. The amount of powder to be transported by the coater is defined by the layer thickness and the area to be coated.DE 10 2010 020 418 A1 describes a device for generatively producing a three-dimensional object, wherein a layer-by-layer application of a powder material on a carrier or on a previously applied layer can be carried out by means of the device after the carrier has been lowered beforehand by the amount of a layer thickness. Furthermore, the powder material is selectively solidified by energy-containing radiation at locations corresponding to the object and the aforementioned steps are repeated until the object is finished. The device defines a two-dimensional maximum build area and additionally a reduced build area in which the powder material is applied and irradiated over less than the maximum length and / or less than the maximum width of the maximum build area.The invention is based on the object of specifying a method with which the construction process can be accelerated and construction material can be saved. This object is achieved by the characterizing features of claim 1, advantageous refinements being evident from the dependent claims.The core of the invention is considered to be the construction of a construction cell within the existing construction chamber, which either closely surrounds the object to be constructed with at least one side wall of the construction chamber or further construction cell wall sections and at the same time reduces the coating volume and the area of the coating application in such a way that predominantly only the region within the construction cell is coated and regions of the construction chamber lying outside the construction cell are excluded from the actual coating process, but at most serve as an overflow region.The invention is thus based on the combination of two basic concepts. Firstly, a construction cell is erected within the construction chamber, which is intended to closely surround the object to be constructed, wherein the construction cell wall preferably adjoins at least one side wall of the construction chamber. The second idea is based on a reduction in the coating volume and the area of the coater application, which can ultimately be carried out by a coater whose coating width can be adapted to the freely selectable construction cell width (extent of the construction cell at right angles to the application direction of the coater). A coater usable for the method can be provided, for example, with extendable or fold-out coater side parts which define the coater width.The method is particularly advantageous in that a large construction chamber can be "generatively reduced", i.e. the construction chamber of a relatively large installation in which relatively large-volume objects can be produced can be reduced by drawing in a construction cell wall generatively constructed with the object such that only little construction material has to be used. Although it is fundamentally the case that non-solidified construction material can be reused, this requires a screening of the construction material which surrounds the actual object, since during the melting process, melt sprays always fall onto the surface region of the powder layer surrounding the actual object and there enter into a more or less firm connection with the melt layer. Therefore, a part of the powder used for coating in the construction chamber as a whole can no longer be used. The method according to the invention thus saves powder to a not inconsiderable extent. Because the surface area of the construction cell to be coated is significantly smaller than the total surface area of the construction chamber, the method also accelerates, which leads overall to shorter construction times.In principle, it is possible to use the volume region between the outer side of the construction cell and the inner side of at least one construction chamber inner wall as an overflow region. According to the invention, the region lying within the construction chamber but outside the construction cell is covered by a screen provided with an opening, which is arranged under the coater or under the coater plane. The opening of the aperture substantially corresponds to the area of the construction cell. It can be dimensioned somewhat larger, so that excess construction material can be moved through a gap into the region of the construction chamber serving as an overflow.The contour of the construction cell can be designed variably, i.e. the walls can be shaped and laid in such a way that they enclose the component to be produced as closely as possible.The construction cell is advantageously arranged within the construction chamber in such a way that it borders a construction chamber wall from which the coating process begins. The coater will then be able to push powder-like construction material from the metering chamber into the region of the construction cell without construction material being previously brought into a region which is not to be coated.Advantageously, it is also possible for the powder penetrating into the volume region between the outer side of the construction cell and the inner side of the construction chamber walls to be conveyed back into a metering chamber during the construction process. This can be done continuously or always before an exposure process.If a diaphragm is used to cover the region of the construction chamber that is not required for the actual construction process, it is advantageous if the opening of the diaphragm is adapted to the contour of the construction cell.In a development of this concept, however, it is also possible to actively control the opening of the panel, so that it is adapted to the currently present contour of the construction cell top side. It is then possible to give the construction cell different cross sections during the construction process in order to enable an even better adaptation of the construction cell to the contour of the component.The control computer which controls the method has the possibility of calculating the volume of construction material required for a coating operation and is thus able to define the coater volume as a function of construction cell coating area. In other words, the coater receives from the metering chamber only as much construction material as is required for the coating operation. In addition, the variable coater can be controlled in such a way that it applies the material present in the coater substantially only over a width which substantially corresponds to the current construction cell width.The construction cell can consist of at least one construction chamber wall and a generatively constructed construction cell wall. The wall of the construction cell can be straight, round, polygonal or otherwise of any desired configuration. For example, it is possible to use two angularly contiguous building chamber walls and at least one generatively constructed building cell wall to form the building cell. The construction cell can comprise a construction cell wall running in the coating direction and extending from a first construction chamber wall to a second construction chamber wall, in order to divide the construction chamber into a construction region and an overflow region, for example.It is particularly advantageous to generatively build up, in the transition region between a construction chamber wall and a construction cell wall, a seal interacting with the construction chamber wall, which seal can be designed in particular in the manner of a labyrinth seal.The invention is explained in more detail with reference to exemplary embodiments in the drawing figures. These show FIG. 1 shows an illustration of the procedure according to the prior art; FIG. 2 is a diagram of a first method according to the invention; FIG. 3 is a diagram showing another method according to the present invention; FIG. 4 is a diagram of a third approach according to the invention; FIG. 5 is a diagram of a fourth method according to the invention; FIG. 6 is a diagram of a fifth method according to the invention; FIG. 7 is a diagram of a sixth approach according to the invention; FIG. 8 is a diagram of a seventh method according to the invention; FIG. 9 is a representation of a coater for use in conjunction with the method of the invention; FIG. 9a shows a coater blade according to the prior art; FIG. 9b shows a coater blade according to the invention; FIG. 10 shows the use of the coater according to FIG. 9 band the illustration of the directions of movement of the powder within the coater;Construction devices 1 according to the prior art have a construction chamber 3 which is bounded by side walls 2 and in which the construction process takes place. Construction material is supplied from a metering chamber via a coater blade which is moved in the direction of the arrow and conveys construction material onto a support device which forms the base of the construction chamber 3. Construction material not required is moved by the coater into an overflow.According to FIG. 2, according to the invention, only a reduced part of the construction chamber 3 is used as construction cell 10, the part serving as overflow region 20 in addition to the overflow.A building cell wall 11 serves for separating building cell 10 and overflow region 20, which in the embodiment shown in FIG. 2 leads centrally through the building chamber at right angles to the coating direction. In the drawing figures 3-8, other paths of the construction cell wall 11 are provided. In the exemplary embodiment shown in FIG. 3, two structural cell wall sections adjoining one another at right angles form the structural cell 10 together with the structural chamber wall 2. In the exemplary embodiment shown with FIG. 5, the construction cell wall 11 has an overall polygonal profile.In the exemplary embodiment illustrated with FIG. 6, the construction cell wall 11 extends in the coating direction and separates (as seen in the coating direction) the construction chamber 3 into a right overflow region 20 and a left construction cell section 10.In the exemplary embodiment shown in FIG. 7, two construction cell walls 11 run parallel in the coating direction and thus form two lateral overflow regions 20 which adjoin the construction cell 10 on both sides.In the exemplary embodiment shown in FIG. 8, the construction cell walls 11 run similar to FIG. 7, but do not extend as far as the opposite construction chamber wall 2, but are connected to one another by a construction cell end section.The embodiment of a variable coater shown in FIG. 9 bshows a coater blade, the lateral end regions of which are configured such that different coater widths can be adjusted in order to match the coating width to the current width of the construction cell 10. FIG. 10 to be adapted.In principle, it is possible to provide a diaphragm which is illustrated in FIG. 8 band which can be used to move the overflow regions 20. To cover FIG. 8. The aperture has an opening. This opening is adapted to the surface of the construction cell 10 or alternatively is of variable design.LIST OF REFERENCE CHARACTERS1 Construction device 2 Side wall 2 aFirst construction chamber wall 2 bSecond construction chamber wall 3 Construction chamber 4 Metering chamber 5 Arrow direction 6 Overflow 10 Construction cell 11 Construction cell wall 20 Overflow region 30 Coater 31 Delimiting element

Claims

Method for producing three-dimensional objects by successively consolidating layers of a powdery building material which can be consolidated by means of electromagnetic radiation, in particular bundled radiation such as laser radiation or electron radiation, at the locations corresponding to the respective cross section of the objects, having the following features, - providing a construction apparatus (1) which has a construction chamber (3) bounded by side walls (2) and a carrying apparatus, which is arranged within the construction chamber (3) so as to be displaceable in height, for carrying the object, and - providing a coating apparatus for applying layers of the building material to the carrying apparatus or a previously formed layer, and - providing an irradiation device for irradiating layers of the building material at the locations corresponding to the respective cross section of the object, - constructing a construction cell (10) by generatively constructing at least one construction cell wall (11), which surrounds the object to be built closely either with at least one side wall (2) of the construction chamber (3) or with further construction cell wall sections and - reduction of the coating volume and the surface of the coating application in such a way that predominantly only the region within the construction cell (10) is coated, - characterized in that the contour of the construction cell (10) substantially follows the contour of the object to be built and the volume region lying within the construction chamber (3) but outside the construction cell (10) is covered by a screen provided with an opening and arranged under a coating device (30).Method according to claim 1, characterised byuse of the volume region between the outer side of the construction cell (10) and at least one inner wall of the construction chamber as an overflow region (20).Method according to one of the preceding claims, characterized in that the contour of the construction cell (10) is variable.Method according to one of the preceding claims, characterized in that the powder which penetrates into the volume region between the outer side of the construction cell (10) and the inner side of the construction chamber walls (overflow region (20)) is conveyed back into a metering chamber during the construction process.Method according to one of the preceding claims, characterized in that the opening of the panel is adapted to the contour of the construction cell (10).Method according to one of the preceding claims, characterized in that the opening of the diaphragm is controlled in such a way that it is adapted to the current contour of the construction cell top side.Method according to one of the preceding claims, characterized in that the coater volume is controlled as a function of the construction cell coating area.Method according to one of the preceding claims, characterized in that the construction cell (10) consists of at least one construction chamber wall and a generatively constructed construction cell wall (11).Method according to one of the preceding claims, characterized in that the construction cell (10) comprises two construction chamber walls and at least one generatively constructed construction cell wall (11).Method according to one of the preceding claims, characterized in that the construction cell (10) comprises at least one construction cell wall (11) running in the coating direction and extending from a first construction chamber wall (2a) to a second construction chamber wall (2b).Method according to one of the preceding claims, characterized in that the coater (30) is provided with variable lateral limiting elements (31) for reducing the coater volume.Method according to one of the preceding claims, characterized in that in the transition region between a construction chamber wall and a construction cell wall (11), a seal interacting with the construction chamber wall is generatively constructed.Method according to Claim 12, characterized in that the seal is constructed in the manner of a labyrinth seal.

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