Abstract:
A method and apparatus are disclosed for producing a three-dimensional body consisting of individual solidified layers, whereby a coating material is disposed on one of a carrier plate and an already-solidified layer of the body in a first layer thickness by slidably withdrawing a bottom plate of a storage container filled with the coating material, thereby allowing coating material to descend from the storage container onto the carrier plate or already-solidified layer of the body. The first layer thickness of the coating material is then reduced to a lesser second layer thickness by re-inserting the bottom plate through the coating material disposed on the carrier plate or already-solidified layer. The coating material is then solidified at predetermined locations in order to generate a desired layer contour of one solidified layer of the three-dimensional body.

Description:
CROSS-REFERENCE 
       [0001]    This application is a divisional of U.S. patent application Ser. No. 12/993,230 filed on Mar. 1, 2011, which is the U.S. National Stage of PCT/EP2008/006857 filed on Aug. 20, 2008, which claims priority to German patent application no. 10 2008 022 946.6 filed on May 9, 2008. 
     
    
     TECHNICAL FIELD 
       [0002]    The present disclosure generally relates to fibers for producing a shaped body made of individual, interconnected layers. The present disclosure further relates to a method for producing fibers and a method for producing a shaped body according to a layer-by-layer construction. Moreover, the present disclosure relates to a shaped body comprising a plurality of fibers lying one above another and interconnected with each other, as well as to the use of fibers for producing a shaped body. 
       BACKGROUND OF THE INVENTION 
       [0003]    Nowadays, a wide variety of manufacturing machines having specifically-defined fabrication chambers are used for fabricating products and/or components. Often, one or more components can be produced in a single production run in the fabrication chambers of these manufacturing machines, due to the type of production method. Such methods and devices are generally known, for example, by the term “Solid Freeform Fabrication” (SFF-systems) and basically include, for example, production methods and production machines, which are able to produce three-dimensional components directly from 3D-CAD-data. This term further includes all known rapid prototyping and rapid manufacturing methods. 
         [0004]    A common feature of all known SFF-systems is the layer-by-layer construction of a workpiece. In recent years, SFF-systems have been used, in which the individual layers are made of a powder or powder-like materials. In particular, metallic components are produced in a melting phase by laser sintering or electron beam melting. “Selective laser sintering” (SLS method) also works according to this principle. In “selective mask sintering” (SMS method), instead of a laser beam, a wide-surface radiation source, e.g., an array of infrared radiators, is used for curing and/or solidifying defined layer areas. A mask determines which areas of a layer will be cured and/or solidified and the mask has to be newly generated for each layer. 
         [0005]    All these methods are based on initially applying a layer of loose, i.e. non-solidified, coating material, which has an accurately defined layer thickness and shaped surface (usually a planar surface). The layer-buildup methods used together with the present teachings may be, for example, the following methods: 3DP of the company Zcorp, Polyjet of the company Objet, SMS of the company Sintermask, SLS and DMLS of the company EOS, SLA as well as IMLS of the company 3D Systems, LaserCUSING of the company Concept Laser, laser melting of the company MCP, Electron Beam Melting of the company Arcam, and Electron Beam Sintering. 
         [0006]    The above-mentioned layered construction (rapid prototyping) systems have been known for a long time for rapid and cost-effective production of prototypes or small series production. The primary application of previously-used rapid prototyping systems has been the production of components made from organic materials like polymers and waxes. Rapid prototyping systems are, however, also increasingly being used in the production of metal components. In particular, metal components are produced in a melting phase by laser sintering or electron beam melting. 
         [0007]    In the above-mentioned methods, 3D CAD data is typically first broken up into a plurality of individual layers or vertical sections and then the workpiece built up or fabricated in the actual production process based upon these individual layers or sections. That is, body outline data must exist for each layer in all known layered construction methods for producing three-dimensional bodies. Body outline data precisely specifies in each layer, which areas of the layer have to be melted or sintered in accordance with the type of layered construction technology used. Such a method is described, for example, in WO 2005/090448 A1. In this case, a layer is produced by applying a powder layer of a predetermined thickness on a base or an already-produced layer and then selectively solidifying this powder, for example, by laser irradiation in the areas that form each layer of the shaped body, thereby bonding it with the solidified areas of the previous layer which are positioned beneath. After completion of the top layer, the non-solidified powder is removed, so that only the shaped body made of the solidified powder is left. A prerequisite for these methods is a powder as a starting material that, on the one hand, can be applied on a base in layers having a defined thickness and, on the other hand, can be selectively solidified in a well-defined manner by targeted fusing, or sintering, or by contact with a liquid that cross-links the powder, thereby undergoing a mechanical bond with the already solidified areas of a previous layer. 
         [0008]    The production of such powders, which are, e.g., made of metals, metal alloys or thermoplastics, in particular polyamides having a long hydrocarbon chain between the amide groups, like PA 11 or PA 12, is relatively costly, because the powder particles must have dimensions (diameter, largest diameter to smallest diameter in elliptical particles, surface roughness, etc.) that are defined within narrow limits. 
         [0009]    It is also known from WO 2005/090448 A1 to admix additives, such as glass spherules, aluminum flakes or also stiffening or reinforcing fibers, e.g., carbon, glass, ceramic, or boron fibers, into the thermoplastic powder in order to improve its mechanical characteristics, wherein the volume fraction of said additives may amount to up to 30% of the powder and wherein their length distribution is chosen such that the percentage of fibers protruding from the surface of the powder particles, into which the fibers are incorporated during production, is as small as possible. This ensures that the cross linking of powder particles and/or the solidification of the powder is not impaired during the laser irradiation. 
         [0010]    In EP 1 058 675 B1 and U.S. Pat. No. 4,938,816, methods for laser sintering are disclosed wherein a ceramic powder or other powder is used. A device for laser sintering, in particular, metal powder is known from DE 195 14 740 C1. A device and a method for building up fluids are disclosed in DE 10 2004 008 168 A1. Finally, it is known from this prior art to compact the powder during laser sintering or to compact a layer during or prior to the solidification using the laser means in order to achieve a high volume density. 
         [0011]    The known devices and methods may, however, have the disadvantage that the coating material forming the individual layers is expensive and, under certain circumstances, may either only function in a very narrow process window or may have a low margin of error. Further, such methods may also make particularly high demands on the materials to be used, as the forces involved in the coating process are dependent on the flowability of the powders and the viscosity of the pastes, respectively. In particular, in contrast to spherical powders, so-called irregular or fiber-shaped powders may be problematic to process using conventional devices and methods, or may not attain sufficient powder density during the coating, in order to achieve a sufficient component density during processing. Therefore, powders having spherical particle geometries are often used, which powders are frequently mixed with flow improvers, such as, for example, carbon black or SiO 2  in order to make these powders usable for conventional coating devices. 
         [0012]    The known layering methods and devices may cause difficulties when the surface to be coated exhibits different states, e.g., when unhardened material and hardened material are present or when loose powder and fused powder are present. 
       DESCRIPTION OF THE INVENTION 
       [0013]    In a first aspect of the present teachings, a new raw material for a shaped body made of individual solidified layers is disclosed, which may be used to partially or completely overcome one or more of the above-mentioned problems. 
         [0014]    According to the first aspect, fibers may be used as the raw material for producing a shaped body comprised of individual interconnected layers according to a solid freeform fabrication method. 
         [0015]    In a solid freeform fabrication method according to another aspect of the present teachings, the fibers may be spread out in layers that are substantially comprised of loose fibers, which are then interconnected in predetermined areas of a fiber layer, preferably by applying energy, thereby forming solidified areas in said fiber layer. The solidified areas of one fiber layer are preferably connected with the solidified areas of an already existing fiber layer. 
         [0016]    In contrast to conventional powder particles that are close as possible to a spherical shape, the fibers according to the present teachings can be easily produced with precisely specified dimensions, whereby the fibers and the powder comprised thereof are cost-efficient and have specific characteristics. 
         [0017]    In another aspect of the present teachings, the fibers preferably may be comprised of different materials and/or have differing dimensions, thus enabling precise tuning to the particular requirements. 
         [0018]    The diameter of the fibers is, for example, between 0.001 and 0.5 mm, preferably between 0.01 and 0.1 mm. In a further aspect of the present teachings, the ratio of the average diameter to the average length of the fibers is advantageously between 0.1 and 1000, preferably between 0.5 and 3. With the stated dimensions, it is possible to apply the fibers in a homogenous, thin layer having a thickness, for example, between one and ten times the thickness of a fiber dimension, preferably the fiber diameter. 
         [0019]    In another aspect of the present teachings, the edges of the end faces of at least some of the fiber pieces are preferably irregular and/or chamfered. This improves the mutual mechanical bonding between the fiber pieces, for example during fusing or sintering. 
         [0020]    In another aspect of the present teachings, the fibers preferably comprise at least one of the following materials: thermoplastics such as polyamide (PA), polypropylene (PP), polylactide (PLA), polybutylene terephthalate (PBT) or polyethylene terephthalate (PET), etc. 
         [0021]    A filler material made of particulate material, for example, may be added to the fibers, wherein the filler material particles may be embedded in the solidified areas comprised of interconnected fibers, without being fixedly connected with the fiber pieces, or may be interconnected with each other, or may be connected with the fiber pieces as well as with each other. The proportion of filler material is preferably less than 50 volume percent, so that the matrix formed by the fibers will be maintained after solidification. The filler material may be, for example, carbon black, carbon, glass, metal oxide, or ceramic. Depending on the preferred effect of the filler material, the particles of the filler material are fibrous or spherical. The dimensions of the filler material particles are advantageously between 0.005 and 0.5 mm. 
         [0022]    In another aspect of the present teachings, a method for producing fibers is provided, wherein a material is extruded into elongated fibers. The fibers are subsequently trimmed into fiber pieces that are suitable for producing a shaped body comprised of individual interconnected layers according to a solid freeform fabrication method. 
         [0023]    At least one rotating cutting- or impact element may be utilized for trimming the fibers. 
         [0024]    In another aspect of the present teachings, a method for producing a shaped body according to layer-by-layer (rapid prototyping) construction is provided, wherein a fiber layer of defined thickness is applied to an existing fiber layer that is solidified in predetermined areas, wherein fiber layer itself is solidified in predetermined areas, and wherein the newly-formed, solidified areas undergo a bonding with the solidified areas of the already existing fiber layer. Accordingly, for the first time in this technical field, fibers are used as a raw material instead of the conventional materials. 
         [0025]    In another aspect of the present teachings, a shaped body is provided, whose solidified portions are comprised of a fiber material as described above. This shaped body can be produced in a cost-effective manner with a defined and predetermined quality. 
         [0026]    For the sake of good order, it is noted that the fibers according to the present teaching are structures having a diameter that is smaller than its length, i.e. structures which are thin in relation to their length, and which may possibly be flexible. Generally speaking, fibers are, for example, also structures whose geometrical shape results from an extruded cross-section. Basically, the fibers may be structures having a generally cylindrical shape. The basic shape of the cylinder may, however, be arbitrary; a circular cylinder merely is preferred. Slanted cylinders also fall within the present definition of fibers. 
         [0027]    The average length and the average diameter of the fibers are preferably determined by microscopic analysis as well as optical particle measurement. Herein, e.g., the direction of extrusion, i.e. the cylinder axis, is referred to as the length, and the circumference of the cross sectional area, i.e. the base surface of a cylinder, is referred to as diameter. The average values may, for example, be calculated by summing up the measured or determined values of a defined number of fibers, and dividing the summation value by the number of measured fibers. The number of fibers may be, for example, 10, 100, 1,000, 10,000, 100,000 or more. It is explicitly noted that also all possible intermediate values are to be understood as being expressly disclosed. Finally, it is noted that known computer-aided quantitative measurements for determining the average fiber lengths and average diameters also may be used, e.g., by utilizing computer tomography. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0028]    For further explanation and better comprehension, several exemplary embodiments of the present teachings are described and explained in more detail in the following with reference to the accompanying Figures. 
           [0029]      FIGS. 1   a ) to  1   e ) show perspective views of fibers which are used for the powder according to the present teachings; 
           [0030]      FIG. 2  shows a fiber powder comprised of different fiber pieces; 
           [0031]      FIG. 3  shows examples of possible cross-sections of the fibers, 
           [0032]      FIG. 4  shows a fiber powder comprised of fiber pieces and filler material particles; 
           [0033]      FIG. 5  shows a schematic sectional view of a device for producing a shaped body according to a layer-by-layer construction; 
           [0034]      FIG. 6  shows a fiber powder comprised of fiber pieces before solidification; and 
           [0035]      FIG. 7  shows the fiber powder of  FIG. 5  after solidification; 
           [0036]      FIGS. 8   a ) to  8   g ) show a sequence of method steps according to a first exemplary embodiment of the present teachings for producing a shaped body comprised of a plurality of fiber layers; 
           [0037]      FIGS. 9   a ) to  9   c ) show a sequence of method steps according to a second exemplary embodiment for producing a shaped body comprised of a plurality of fiber layers; 
           [0038]      FIG. 10  shows an exemplary embodiment of a device according to the present teachings with a plurality of material application and reducing devices; 
           [0039]      FIG. 11  shows a further exemplary embodiment of a combined application and reducing device; 
           [0040]      FIG. 12  shows a further exemplary embodiment of a part of a device according to the present teachings having a combined material application and reducing device; 
           [0041]      FIG. 13  shows a plurality of exemplary, schematically-illustrated cross-sectional views of surface shapes of coated material after the reducing step according to an exemplary embodiment for producing a shaped body comprised of a plurality of fiber layers; 
           [0042]      FIG. 14  shows a schematic cross-sectional view of part of a method according to the present teachings for reducing the thickness of a first layer; and 
           [0043]      FIGS. 15-18  show exemplary cross-sectional shapes of reducing devices, alternatively combined with smoothing devices, for use in embodiments according to the present teachings. 
       
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE PRESENT INVENTION 
       [0044]    According to  FIG. 1 , fiber pieces  9  having different cross-sectional shapes and different lengths, as well as different shapes of their end faces, may be used for the powder in accordance with certain aspects of the present teachings. 
         [0045]    In the present application, the term “fiber” or “fiber piece” is used for a structure or particle, whose length is larger than its diameter, wherein, for example, the lateral surface is formed in certain portions with a constant profile, at least in the longitudinal direction of the fiber. The fibers are produced, for example, by extruding the fiber material through an extrusion head with openings, the shape of said openings defining the cross-section of the fibers. 
         [0046]      FIG. 1   a  shows a fiber piece  509   a  having an elliptical cross-section,  FIG. 1   b  shows a fiber piece  509   b  having a circular cross-section, the fiber piece  509   c  according to  FIG. 1   c  has a shorter axial length than its diameter, and in the fiber pieces  509   d ,  509   e  according to  FIGS. 1   d  and  1   e , the respective visible end face is irregular or chamfered. 
         [0047]    The fiber pieces  509   a - 509   e , which are shown in an exemplary manner in  FIG. 1 , are produced in a generally known manner by mechanically trimming the fibers exiting the extruder, immediately after exiting from the extruder and after cooling, into fiber pieces  509   a - 509   e  having a predetermined length and having end faces formed in a predetermined manner. 
         [0048]      FIG. 2  shows a powder comprised of different fiber pieces  509 , wherein the different fiber pieces  509  may also be made of different materials. 
         [0049]    The fiber pieces  509   a - 509   e , which are shown in an exemplary manner in  FIG. 1 , may be produced in a precisely predetermined manner with regard to their size, so that the powder according to  FIG. 2  also may have a precisely predetermined constitution. 
         [0050]    The diameter of the fiber pieces  509  used for the powder according to the certain aspects of the present teachings is preferably between 0.01 and 0.5 mm, more preferably between 0.01 and 0.1 mm. The ratio of the diameter to the length of the fiber pieces  509  is preferably between 0.1 and 1000, more preferably between 0.5 and 3. Exemplary cross-sections of fibers are shown in  FIG. 3 , e.g. circular  511   a , elliptical  511   b , or irregularly formed  511   c.    
         [0051]    Preferred extrudable materials for the fiber pieces  509  are, for example, thermoplastics like polypropylene or polyethylene terephthalate. 
         [0052]    The materials are chosen with regard to the required stability and the intended solidification method for solidifying the powder comprising the fiber pieces  509 . 
         [0053]    For various reasons, such as the effect on stability, shrinkage behavior, etc., the powder may contain additives or filler material, which may also be fiber-shaped, but preferably are comprised of spherical, plate-shaped or irregular particles, in addition to the fiber pieces  509  that form the frame of the solidified area of a powder layer  519 , which will be described below. Depending on the application, said fillers or additives are comprised of carbon black, carbon, glass, metal oxides, ceramics or polymer materials. Their proportion is preferably less than  50  volume percent of the powder. 
         [0054]      FIG. 4  shows a powder that is comprised of different fiber pieces  509 , similar to the powder of  FIG. 2 , and additionally comprises additives in the form of spherical particles  512 . 
         [0055]      FIG. 5  schematically shows a cross-section through a device for producing a shaped body  517  according to layer-by-layer construction. Any powder according to the present teachings may be used in this device. 
         [0056]    According to  FIG. 5 , a platform  515  is movable upwards and downwards within a cylinder  513 , which is at least opened towards the top, using a not illustrated drive mechanism. The outer contour of the platform  515  is matched to the inner contour of the cylinder  513 , so that the outer edge of the platform  515  is guided on the inner side of the cylinder  513 . 
         [0057]    A shaped body, denoted as a whole by  517 , whose already formed portions  518  are cross-hatched, is produced in a layer-by-layer manner by disposing layers  519   1  to  519   n  one upon another; the layers preferably have the same predetermined thickness d. 
         [0058]      FIG. 5  shows the shaped body  517  in the state in which four layers  519   1  to  519   4  are already formed, and a fifth layer  519   5  is about to be formed. Just like the previous layers, layer  519   5  is formed by lowering the platform  505  by a distance d within the cylinder  513  after one layer has been formed, and then filling powder into the created space using a not illustrated device in a generally known manner. The constant thickness d of the new powder layer  509   5  may be achieved by slightly overfilling the powder and subsequently flattening the powder level to the level of the upper edge of the cylinder  513  using of a pusher, a press, etc. 
         [0059]    Then, an irradiation device  523 , e.g., a laser head radiating a focused laser beam, is controlled in accordance with CAD data of the to-be-produced shaped body  507 , which data delineate the shaped body in the area of the layer  519   5 , whereby the powder is solidified in the area(s) forming the shaped body, e.g., by surface-fusing, and is left unsolidified in the remaining area(s). The solidified areas  518   1  to  518   4  of the layers  519   1  to  519   4  are cross-hatched in the illustration. 
         [0060]    The entire shaped body  517  is constructed layer-by-layer in the above-described manner and can be removed from the tool after completion; after subsequent removal of the loose powder, it is available for further use. 
         [0061]    Depending on the dimensions of the fiber pieces, said fiber pieces will arrange themselves more or less in parallel to the extension of the respective layer and parallel to each other when the powder is applied, wherein the parallel alignment increases with increases in the ratio between the length of the fiber piece and the diameter of the fiber piece. The layer thickness d is preferably three to five times the diameter of the largest diameter fiber pieces. 
         [0062]      FIG. 6  shows fiber pieces  509  of the powder  511  disposed in a disordered manner prior to solidification. 
         [0063]      FIG. 7  shows the fiber pieces of  FIG. 6  after solidification, which solidification is effected by surface-fusing the fiber pieces  509  under the laser beam, thereby causing the fibers to fuse. As can be seen, a stable fiber frame is formed. Filler materials, if provided, are embedded or fused in the hollow spaces of the fiber frame. This type of insertion of material also allows for the formation of homogenous melted films. 
         [0064]    By using an appropriate ratio of the length and diameter of the fiber pieces  509 , wherein the fibers of the unsolidified powder are, to a large extent, arranged in parallel with each other and are parallel to the extension direction of the fibers, possibly arranged one above the other in a plurality of layers, a shaped body results that has a high volumetric efficiency of the material and good stability. 
         [0065]    The localized solidification may also be achieved with suitable materials of the fiber pieces by selectively spraying the particular layer area to be solidified with a liquid that causes a reaction, which directly connects the fiber pieces  509  with each other and/or solidifies the layer portion, thereby connecting the fibers with each other. 
         [0066]    A further exemplary embodiment of a method for producing a three-dimensional body  10  is shown in progressive method stages in  FIGS. 8   a )- 8   g ). As shown in  FIG. 8   a ), the body  10  is already comprised of a plurality of solidified or hardened layers  12 ,  14 ,  16 ,  18  which are arranged one on top of the other. Just like in the known laser-sintering method mentioned in the 
         [0067]    Background section, or according to the above-mentioned Sintermask-technology, a coating material  30 , e.g., a powder, has been cured, solidified, surface-fused or fused in predetermined areas. Hence, every layer  12 ,  14 ,  16 ,  18  has the desired contour of the body  10  to be produced. 
         [0068]    A vertical section of a container  20  is schematically shown in  FIG. 8   a ). Here, the container  20  is formed as storage container, in which the loose powder  30  is stored. The container  20  has walls  22 ,  24  which, together with a bottom  26 , form the container  20 . Together with not illustrated additional container walls and the bottom  26 , the container walls  22 ,  24  form a storage space, which may be opened to the top and in which the powder  30  to be used is stored. Alternatively, the container  20  may also be closed. 
         [0069]    The body  10  to be produced is supported on a vertically movable carrier plate  28 , which is movable upwards and downwards via not illustrated means. A source of radiation  100  is arranged above the body  10 , which is only partially constructed at this stage. The source of radiation  100  may comprise, for example, an array of infrared radiators. Alternatively, it is also possible to provide a directable laser beam as the source of radiation. 
         [0070]    In the exemplary arrangement as is shown here, a mask  112  is positioned below the source of radiation  100 , which mask may be formed, for example, by printing a glass plate. The to-be-solidified areas of a layer  50  to be newly formed are left blank on this mask  112 . The other areas of the glass plate are formed to be substantially impenetrable to the electromagnetic radiation of the radiation source  100 , e.g. they are blackened. This embodiment therefore shows an embodiment in which the Sintermask-technology mentioned in the Background section or the SMS-technology is used. 
         [0071]    Incidentally, in this embodiment, the carrier plate  28 , together with lateral walls, forms a collection container  40 , in which unsolidified coating fiber material remains above the carrier plate  28 . The walls may be arranged to be stationary relative to the carrier plate  28 . 
         [0072]    It is apparent from the subsequent sequences of  FIGS. 8   b )- 8   g ) that the container  20  is movably supported, in particular horizontally movable in the illustrated views according to  FIG. 8 , i.e. it is movable from lateral to the body  10  to above the body  10 . Moreover, the container bottom  26  is movably supported relative to the walls  22 ,  24 . 
         [0073]    According to the view of  FIG. 8   a ), the layer  18  of the body  10  to be produced has been hardened and/or solidified using known techniques. In order to produce a new fiber layer  50 , the carrier plate  28  with the already produced and hardened fiber layers  14 ,  16 ,  18  is then moved downwards by a predetermined distance. This step is illustrated in  FIG. 8   b ). 
         [0074]    As shown in  FIG. 8   c ), the container  20  is now moved over the most recently formed fiber layer  18 . Thereafter, according to the illustration of  FIG. 8   d ), the container bottom  26  is pulled out towards the left side. As a result, the fiber powder  30  slides downwards in the container  20  and covers the most recently formed fiber layer  18 . This stage of the method is also shown in  FIG. 8   e ) in more detail. By pulling or pushing out the container bottom  26 , a fiber layer  50  comprised of loose fibers, and having a large thickness D 1 , is thus achieved, which thickness is higher or thicker than the actual fiber layer thickness D 2  to be produced. 
         [0075]    Then, the bottom plate  26  is inserted in the step according to  FIG. 8   f ), whereby a layer thickness D 2  is achieved. D 2  is the final fiber layer thickness if no pressing and/or compacting takes place after the insertion of the separating element  26 . In other words, in the exemplary procedure illustrated in  FIG. 8 , a fiber layer  18  of material  30  to be solidified is first formed on the most recently prepared layer. The fiber layer  18  has a higher layer thickness than is desired for the final layer thickness D 2 . By inserting the bottom  26  again underneath the container  20 , the layer thickness D 2  of the fiber layer  50  to be newly produced is achieved. This is particularly clear from  FIG. 8   f ). 
         [0076]    In the step according to  FIG. 8   g ), the container  20  with the inserted separating element  26  is then moved back to the left starting position. After removing the container  20  together with the bottom plate  26 , which bottom plate functions as a separating element in this case, the new fiber layer  50  having the desired layer thickness D 2  is formed on the most recently solidified fiber layer  18 . Now, desired selective solidification and/or hardening of the loose fiber coating material  30  of the fiber layer  50  may be carried out using the radiation source  100  mentioned above. Then, additional fiber layers of the body  10  to be produced may be formed by a new sequence of the process steps according to  FIGS. 8   a )- 8   g ). 
         [0077]    A possible alternative embodiment may also provide a further step, wherein the carrier plate  28  is moved slightly upwards between the step of  FIG. 8   f ) and the step of  FIG. 8   g ), thereby compacting the prepared fiber layer  50 , because the bottom  26  is still located above the fiber layer  50 . Alternatively, the container  20  may be moved downwards by a defined distance in order to compact the fiber layer  50  to the predetermined final layer thickness D 2 . 
         [0078]    After the optional compacting step is completed, the container  20  is moved back as illustrated in  FIG. 8   g ). This possible special case of an embodiment for producing a three-dimensional body  10  may be advantageous for certain fiber materials, in particular in order to achieve a higher density in the layer  50  to be prepared. 
         [0079]    It is common to the above-described methods for producing a three-dimensional body  10  of plural fiber layers  12 ,  14 ,  16 ,  18  that, for the first time, when preparing the final fiber thickness D 2  of the fiber layer  50  to be produced, the forces acting on the fiber layer  50  to be produced, as well as the underlying layer  18 , and, possibly, on the further fiber layers  12 ,  14 ,  16 , are lower than before. Therefore, problems that may possibly occur under certain circumstances can be avoided. 
         [0080]      FIGS. 9   a )- 9   c ) show an alternative embodiment of a method and device for producing a three-dimensional body  10  according to the invention. Here, a container  20 ,  20 ′ is provided on each of the right side and the left side of the body  10  to be produced. Basically, such a container  20 ,  20 ′ may be formed like the container  20  according to  FIG. 8 . In a first step, one of the containers  20 , in this case the container  20 ′ on the right side according to  FIG. 9   a ), is moved over the body  10  to be produced. Then, the bottom plate  26 ′ of this container is removed according to  FIG. 8   d ). Hence, this method step according to  FIG. 9   c ) corresponds to the stage of the method shown in  FIG. 8   d ). The further method steps may now be carried out according to  FIG. 8   e )- 8   g ). Accordingly, reference is made to the above embodiments and explanations. 
         [0081]    Subsequently, the container  20 ′, which is located on the right side, may be moved back over the body  10  to be produced, or the other container  20 , which is located on the left side, may be moved over the layered body  10  in order to generate another layer  50  in the above-explained manner. In the embodiment shown in  FIG. 9 , it is advantageous that the containers  20 ,  20 ′ may contain different materials, so that a body  10  made of fiber layers comprised of different fiber materials can be produced according to the method shown herein. 
         [0082]    In principle, it is also possible to provide more than two containers  20 ,  20 ′ with different fiber materials  30 . In  FIG. 10 , for example, an embodiment with four containers  20  is shown that respectively contain different fiber materials. Here, each container may be moved relative to the layer body  10  to be produced. The arrangement according to  FIG. 10  is quite compact. According to the illustration of the embodiment shown in  FIG. 10 , it is, therefore, possible to produce a body  10  made of four different materials. In particular, bodies  10  adapted to ambient conditions can be created with specific characteristics in defined portions of different fiber layers  12 ,  14 ,  16 ,  18 ,  50 . 
         [0083]    In principle, the duration of the process for producing the three-dimensional body  11  can also be kept short by a method according to the present teachings, despite, for example, the use of different fiber materials, because only different containers  26  containing the different materials  30  have to be moved over the body  10  to be produced.  FIG. 11  shows an exemplary embodiment of a combined material application and reducing device as may be used in a method according to the invention. Like in the previously explained embodiment, a height-adjustable carrier  28  is provided, on which the body  10  to be produced will be formed. In the embodiment shown here, one fiber layer  18  of the body  10  to be produced is already formed on the carrier plate  28 . Then, the combined material application and reducing device  110  is moved over the body  10  to be produced from the left side. Here, fiber powder  30  in a large thickness D 1  is located below a vertical plate  120 , which leaves a gap  140  between the previously generated layer  18  and a lower edge. This gap  140  has a width larger than the layer thickness D 2  to be produced at the end of the application process. A horizontal separating plate  130  is disposed behind the vertical separating plate  120 . It defines the desired final layer thickness D 2 . 
         [0084]    This separating plate  130  has a narrow leading edge  132  in order to divide the coating material  30 , which is applied in a large thickness Dl onto the already generated fiber layer  18 , into an upper portion  32  and a lower portion  34 . Here, substantially only vertical forces are acting, but no shearing forces are acting that might be disadvantageous not only for the fiber layer  50  to be produced, but also for the already produced fiber layer  18 . The coating material  32 , which is located above the separating plate  130 , can not apply any forces onto the already produced fiber layers  18  or the fiber layer  50  to be produced, due to the design of the separating plate  130 . At the same time, a flawless upper surface and layer thickness D 2  can be generated on the bottom side of the separating element  130  due to optional special sliding properties. 
         [0085]    That is, in the embodiment according to  FIG. 11 , which is shown here, this combined material application and reducing device  110  is moved so far to the right that a defined layer of non-solidified fibers is generated across the entire carrier  28 . Then, the required solidification can take place at predetermined locations of the fiber layer  50 . Subsequently, a further container may be correspondingly moved over the carrier  28 , or, for example, the unit  110  may be turned and then moved from the right side shown in  FIG. 11  to the left side in order to generate a new fiber layer  50 . In principle, it is also possible to move such a unit  110  on a circular path. In this case, after application of the fiber layer  50 , the fiber layer  50  would be exposed in order to be solidified in the desired, known manner. After completion of one full revolution, the unit  110  would return in order to prepare a new fiber layer  50 . Incidentally, it is noted that, after solidifying the fiber layer  50 , the carrier  28  is, of course, moved downwards by the desired layer thickness D 2 , so that a new fiber layer  50  may be produced using the unit  110 . 
         [0086]      FIG. 12  shows an embodiment of a unit  210  very similar to  FIG. 11 , which basically corresponds to the unit  110 . Instead of the flat separating plate  130 , the separating plate  230  is curved upwardly in this case. Thus, it can be achieved that, immediately after applying the material  30  at the leading edge  232 , the material  30  (in this case the fibers) of the fiber layer  50  to be generated no longer slides along the bottom side of the separating device  230 . Possible adhesion, etc., can be thereby avoided. However, at the same time, under certain circumstances the coating material  30  located above the curved separating plate  230  are prevented from exerting forces onto the fiber layer  50  to be produced or onto fiber layers  18  that are positioned below, etc. Apart from that, the design of the unit  210  according to  FIG. 12  is implemented identical to the design of the unit  110 . It also is provided with a vertical separating wall  220 . 
         [0087]      FIG. 13  shows exemplary surface layer shapes. In accordance with the above illustrated method, it is easy to generate not only planar new fiber layers  50  having a defined layer thickness D 2 , but also wave-like or serrated new fiber layers  50 , which then lead to bodies  10 ′,  10 ″ that have no individual planar fiber layers  12 ,  14 ,  16 ,  18 ,  50 , but rather have stepped or wave-like surface shapes. 
         [0088]      FIG. 14  shows other possible separating devices, in this case the plate  130 , which may be used, for example, in the embodiments according to  FIGS. 11 and 12 . In this case, the separating element  130  has a leading edge  132 , which ends in particular in an extremely thin cutting edge  134 , so that a problem-free separation of the material  30  can take place, thereby producing the layer  50  to be newly generated with a defined layer thickness D 2 . In this exemplary embodiment of the plate  130 , the cutting edge  134  has an undercut, so that the material of the new layer  50  no longer slides along the plate  130  or the leading edge  132  directly behind the cutting edge  134 , whereby detachment problems that may occur under certain circumstances are avoided. 
         [0089]    It is noted that, in an exemplary embodiment, cooling elements such as, for example, cooling lines  200  are provided in the separating element  130  and/or in the cutting edge  134 , in order to achieve adequate cooling of a layer  50  to be solidified. Here, for example, meandering cooling lines  200  are formed within the separating element  130 . A cooling medium, such as e.g. water or other fluids, flows through the cooling lines  200 . The cooling lines  200  are integrated into a (not illustrated) cooling circuit with corresponding elements. 
         [0090]    Alternatively, a suitable design can also be provided for evenly heating the separating element  130  and/or the cutting edge  134 . A combination of cooling and heating elements  200  within the separating element  130  is also conceivable. For this reason, either a cooling or heating fluid may be pumped through the lines  200 . 
         [0091]      FIGS. 15 to 18  show further exemplary embodiments of leading edges of separating elements, which may be used, for example, in the units  110 ,  210  according to  FIGS. 11 and 12 , but also in the devices according to  FIGS. 9 and 10 .  FIG. 15 , for example, shows a design having an edge or cutting edge  134  that has upper and lower sides forming a tip.  FIG. 16  has a design similar to that of  FIG. 14 , wherein the leading edge is formed slightly different, i.e. with a tip that is inclined towards the front and with an undercut.  FIG. 17  shows a design having an undercut, wherein a separating surface and a slight sliding edge  138  are provided at the front edge. Finally,  FIG. 18  shows a design of the front edge  140  for a separating element  130 , which arrangement is very similar to  FIG. 14 . 
         [0092]    Additional embodiments disclosed herein include: 
         [0093]    1. Fibers ( 509 ) that are formed for producing a shaped body ( 10 ;  517 ) according to a solid freeform fabrication method, the shaped body being comprised of individual, interconnected layers ( 14 ,  16 ,  18 ;  519 ). 
         [0094]    2. The fibers according to embodiment 1, characterized in that the fibers ( 509 ) are formed such that they adhere, fuse, or react with each other at least at segments of the fibers by selective application of energy, e.g., by irradiation, or by a reactive means. 
         [0095]    3. The fibers according to one of the preceding embodiments, characterized in that the fibers ( 509 ) are made of different materials and/or have different dimensions. 
         [0096]    4. The fibers according to one of the preceding embodiments, characterized in that the average diameter of the fibers ( 509 ) is between 0.001 mm and 0.5 mm, preferably between 0.01 mm and 0.1 mm. 
         [0097]    5. The fibers according to one of the preceding embodiments, characterized in that the ratio of average diameter to average length of the fibers ( 509 ) is between 0.1 and 1000, preferably between 0.5 and 3. 
         [0098]    6. The fibers according to one of the preceding embodiments, characterized in that the fibers ( 509 ) at least partially have end faces that are irregular at the edges. 
         [0099]    7. The fibers according to one of the preceding embodiments, characterized in that the fibers ( 509 ) contain at least one of the following materials: thermoplastics such as PP, PET, PEEK, PA, PLA, ABS, PC and PBT. 
         [0100]    8. The fibers according to one of the preceding embodiments, characterized that at least one filler material ( 511 ) is admixed with the fibers ( 509 ). 
         [0101]    9. The fibers according to embodiment 8, characterized in that the proportion of the at least one filler material ( 511 ) is less than 50 volume percent. 
         [0102]    10. The fibers according to embodiment 8 or 9, characterized in that the filler material ( 511 ) contains at least one of the following materials: carbon black, carbon, glass, metal oxide, ceramic. 
         [0103]    11. The fibers according to one of embodiments 9 to 11, characterized in that the filler material ( 511 ) is not fiber-shaped. 
         [0104]    12. The fibers according to embodiment 12, characterized in that a maximum dimension of a filler material particle ( 511 ) is between 1 nm and 100 μm. 
         [0105]    13. A method for producing the fibers according to one of embodiments 1-12, comprising at least the following method steps:
       forming a material suitable for producing a shaped body ( 10 ;  517 ) according to a solid freeform fabrication method into an elongated fiber shape, which has an average diameter of between 0.001 mm and 0.5 mm, preferably between 0.01 mm and 0.1 mm,   trimming the elongated fiber shape into fiber pieces ( 509 ), which are suitable for producing a shaped body ( 10 ;  517 ) comprised of individual, interconnected layers ( 14 ,  16 ,  18 ;  519 ) according to a solid freeform fabrication method.       
 
         [0108]    14. The method according to embodiment 13, characterized in that the trimming is performed such that the ratio of average diameter and average length of the fiber pieces ( 509 ) is between 0.1 and 1000, preferably between 0.5 and 3. 
         [0109]    15. The method according to embodiment 13 or 14, characterized in that at least one rotating cutting or impact element is used for trimming the fibers ( 509 ). 
         [0110]    16. A method for producing a shaped body ( 10 ;  517 ), wherein
       individual, loose fibers ( 509 ) are spread in a defined layer thickness for forming a fiber layer ( 14 ,  16 ,  18 ;  519 ),   energy is selectively applied to the prepared fiber layer ( 14 ,  16 ,  18 ;  519 ), so that loose fibers ( 509 ) in the fiber layer ( 14 ,  16 ,  18 ;  519 ) undergo a connection to each other in predetermined areas ( 520 ), at least in segments of fiber, thereby forming solidified portions in said fiber layer ( 14 ,  16 ,  18 ;  519 ), and these solidified areas of the fiber layer ( 14 ,  16 ,  18 ;  519 ) are connected with the solidified areas of an already-existing, adjacent fiber layer ( 19 ), and   the above method steps are repeated until a three-dimensional shaped body ( 10 ;  517 ), which is formed in layers with the desired contour, is produced.       
 
         [0114]    17. The method for producing a shaped body ( 10 ;  517 ) according to embodiment 16, characterized in that fibers ( 509 ) are used, which are formed according to one or more of embodiments 1-12. 
         [0115]    18. The method for producing a shaped body ( 10 ;  517 ) according to embodiment 16 or 17, characterized in that the fibers ( 509 ) are formed such that they adhere, fuse, or react with each other, at least in segments of the fiber, by selectively applying energy or by reactive means. 
         [0116]    19. A shaped body comprising a plurality of fiber layers ( 14 ,  16 ,  18 ;  519 ) made of fibers that lie on each other and are connected with each other according to one or more of embodiments 1-12. 
         [0117]    20. Use of fibers ( 509 ) for producing a shaped body ( 10 ;  517 ) comprised of individual, interconnected layers ( 14 ,  16 ,  18 ;  519 ) according to a solid freeform fabrication method. 
         [0118]    21. The use of fibers according to embodiment 20, characterized in that the fibers ( 509 ) are formed such that they adhere or fuse with each other, at least in segments of the fiber, when energy is selectively applied.