Patent Publication Number: US-7713048-B2

Title: Device for a layerwise manufacturing of a three-dimensional object

Description:
The present invention is related to a device for manufacturing a three-dimensional object by a layer-wise solidification of a building material in powder form at positions in the respective layers that correspond to the object 
   In DE 10 2005 016 940 A1 a device for a layerwise manufacturing of a three-dimensional object is described, which comprises a laser sintering device. In the device a building material in powder form is processed. For the application of a layer of the material in powder form a device is provided that comprises a powder application device, a conveyor roller and a feeding chute. 
   In WO 00/21736 A1 a device for manufacturing a three-dimensional object is described, which consists of a laser sintering device. A replaceable container is described, in which a work piece platform is integrated as bottom of the container. The replaceable container can be removed from the device, and a coupling device is provided in the device, which coupling device serves for mounting the container in the device and for connecting the work piece platform to a drive. 
   In such devices, in particular in laser sintering machines, a building material in an applied layer shall already have a temperature close to the processing temperature before the solidification, so that the process of selective solidification can follow quickly. Out of this reason in such known devices there are arranged heating devices in a building space in order to heat the building material by radiant heat. For the case that building material has been heated too much already before the application in a layer, however, the problem can arise that the building material changes its properties in a building material supply container before the spreading. Out of this reason the extent, to which the building material in the layer is pre-heated, is limited in the known devices. 
   It is an object of the present invention to create a device of the initially described type, by which the actual building process can be accelerated and at the same time a deterioration of the building material by thermal effects before the spreading as layer can be prevented. 
   The object is achieved by a device according to claim  1 . Advantageous further developments are described in the dependent claims. 
   By a double-wall structure the building material accommodation regions can be insulated, so that the building material therein can be kept at a lower temperature. Thereby a deterioration of the building material before the spreading as layer is avoided. 

   
     Further features and advantages of the invention arise from the description of embodiments on the basis of the accompanying drawings, of which: 
       FIG. 1  shows a schematic representation of a frame system according to an embodiment; 
       FIG. 2  shows a schematic representation of the beam guide in the embodiment according to  FIG. 1 ; 
       FIGS. 3   a  and  3   b  show schematic detailed representations of the apertures in  FIG. 2 ; 
       FIG. 4  shows a schematic perspective representation of details of a ventilator system in the region of the beam guide in the embodiment; 
       FIG. 5  shows a schematic representation of the building space in the embodiment; 
       FIG. 6  shows a schematic representation of a building container ventilation system in the embodiment; 
       FIG. 7  shows a schematic representation of the mounting of a dosage device in the embodiment; 
       FIG. 8  shows a schematic representation of the mounting of a building space heating module in the embodiment; 
       FIG. 9  shows a schematic representation of the mounting of an application device in the embodiment; 
       FIG. 10  shows a schematic representation of a mounting of the building container; 
       FIG. 11  shows a schematic representation of a building platform seal in the embodiment; 
       FIG. 12  shows a schematic representation of a building material supply system in the embodiment; 
       FIG. 13  shows a schematic representation of an application system in the embodiment; 
       FIG. 14  shows a schematic view of a layer to be used in a beam adjustment method; and 
       FIG. 15  shows a further schematic representation illustrating the building material supply system. 
   

   With respect to  FIGS. 1 and 5  in the following the basic construction of a device for manufacturing a three-dimensional object by a layerwise solidification of a building material is described, which according to an embodiment is constructed as laser sintering device. In the device for a manufacturing of a three-dimensional object layers of a building material are subsequently applied on one another and the positions within each layer that are corresponding to the object to be manufactured in each layer are selectively solidified before the application of a subsequent layer. In the described embodiment a building material in powder form is used, which is solidified by the action of an energy beam on selected positions. In the described embodiment the building material in powder form is locally heated at the selected positions by means of a laser beam such that it is connected to nearby constituents of the building material by sintering or melting. 
   As shown in  FIG. 1  the laser sintering device comprises an optical system, wherein the components of the optical system are attached to the components of the machine frame. A building space  10 , which is schematically represented in  FIG. 5 , is provided in the machine frame. 
   In the described embodiment the optical system comprises a laser  6 , a deflection mirror  7  and a scanner  8 . The laser  6  generates a beam  9  that is incident on the deflection mirror  7  and is deflected by the deflection mirror  7  towards the scanner  8 . Alternatively, a different energy source such as a different radiation source that generates an energy beam, which is directed towards the scanner  8 , may be used instead of the laser. The scanner  8  is constructed in a known manner such that it can direct the incident beam  9  to arbitrary positions in a building plane  11  that is located in the building space  10  as shown in  FIG. 5 . In order to make this possible, an entrance window  12  is provided in an upper partition wall  56  of the building space  10  between the scanner  8  and the building space  10 , wherein the entrance window  12  enables a passing of the beam  9  into the building space  10 . 
   With respect to  FIG. 5  in the following the building space of the device in the embodiment is described. 
   As can be seen in  FIG. 5 , in the building space  10  a container  25 , which is open to the top, is provided. A support device  26  for supporting a three-dimensional object to be formed is arranged in the container  25 . The support device  26  can be moved back and forth in the container  25  in a vertical direction by means of a drive that is not shown. The building plane  11  is defined in the region of the upper edge of the container  25 . The entrance window  12  for the beam  9  that is directed onto the building plane  11  by means of the scanner  8  is arranged above the building plane  11 . An application device  27  is provided for applying building material that is to be solidified onto the surface of the support device  26  or onto a layer that has previously been solidified. The application device  27  can be moved over the building plane  11  in a horizontal direction by means of the drive that is schematically indicated by the arrows in  FIG. 5 . On both sides of the building plane  11  dosage devices  28  and  29 , respectively, are provided, which provide a predetermined amount of the building material for the application device  27  in order to be applied. 
   On the side of the dosage device  29  a supply opening  30  is provided. The supply opening  30  extends over the whole width of the building plane  11  in a direction that is perpendicular to the plane of  FIG. 5 . The supply opening serves for supplying building material to the building space, which in the shown embodiment is a powder material that can be solidified by means of radiation. 
   The building space in the embodiment is subdivided into an upper region  40  and a lower region  41 , as is schematically shown in  FIG. 5 . The upper region  40  forms the actual work space, in which a layerwise application of the building material and its selective solidification are carried out. The lower region  41  accommodates the container  25 . 
   In the shown embodiment some parts are formed by means of a method for a layerwise manufacturing of a three-dimensional element by selectively solidifying positions in the respective layers that correspond to the object. In the embodiment a laser sintering method is used for the manufacturing of the objects. With respect to conventional methods for manufacturing three-dimensional objects such as milling, turning, casting, etc., such a method particularly has an advantage, when complex geometries shall be generated and/or only relatively low quantities need to be manufactured. 
   Operation of the Device 
   When operating the device  1 , the building material is supplied to the building space  10  via the supply opening  30 , and a pre-determined amount of the material is supplied to the application device  27  by means of the dosage devices  28 ,  29 . The application device  27  applies a layer of the building material onto the support device  26  or a previously solidified layer and the beam  9  is directed to selected positions in the building plane  11  by means of the laser  6  and the scanner  8  in order to selectively solidify the building material in those positions that correspond to the three-dimensional object to be formed. Afterwards the support device is lowered by the thickness of one layer, a new layer is applied and the process is repeated until all layers of the object to be formed have been generated. 
   In the following several components of the device are described in more detail. 
   Frame Structure 
   At first the frame structure of the device of the shown embodiment is described based on  FIG. 1 . The device  1  comprises a machine frame, which is formed by three fundamental beams  2 ,  3  and  4 , which are connected to each other by cross-bracings  5 . The three fundamental beams  2 ,  3  and  4  are substantially vertical and form three corners of the device in the shown embodiment. In a plane view the device  1  thus substantially has the outline of a triangle. The fundamental beams  2 ,  3  and  4  and the cross-bracings  5  are arranged such that the outline substantially corresponds to the one of a right angle triangle, where the hypotenuse forms the front side of the device. The cross-bracings  5  are substantially horizontal and connect the fundamental beams such that a rigid, warp-resistant machine frame is formed, the components of which do not change their relative positions or only minimally change their relative positions, even when there is a unilateral action of forces. 
   Due to the design with three fundamental beams  2 ,  3  and  4  that are basically extending in a vertical direction and are arranged in the shape of a triangle, the device  1  can be supported at three positions on a substrate. Due to this construction having three legs the device can be arranged in a quick and uncomplicated way such that a jiggling or tilting with respect to the substrate is prevented. In particular, a change of the alignment with respect to the substrate may be achieved by changing the height of the support of one of the three support points, because this leads to a rotation around the line connecting the other two support points. With a four-point or multi-point support for a change of the alignment the height of at least two support points would have to be changed in order to achieve a stable support. 
   Each of the fundamental beams  2 ,  3  and  4  has a roller  50  and a height-adjustable support leg  51  arranged at its bottom side facing the ground. The support legs  51  are arranged on the corresponding fundamental beams  2 ,  3  or  4  such that they are adjustable in height. Each of the support legs  51  can be moved to a first position, in which the corresponding roller  50  has a larger distance to the bottom side of the respective fundamental beam than the bottom side of the support leg  51  has. Thus, in this first position the device  1  stands on the rollers  50  and the support legs  51  have a distance to the substrate. The rollers  50  are pivoted on the fundamental beams  2 ,  3  and  4 , such that the device  1  can be moved over the substrate in arbitrary directions on the rollers  50 . Also, each of the support legs  50  can be moved to a second position, in which the bottom side of the support leg  51  sticks out more from the bottom side of the respective fundamental beam  2 ,  3  or  4  than the respective roller  50 . In this position, the device  1  is standing on the support legs  51  and a movement of the device  51  relative to the support can be reliably prevented. 
   In the shown embodiment for each of the support legs  51  the side that is facing the respective fundamental beam  2 ,  3  or  4  is designed as threaded rod having an external thread. Corresponding bores having an inside thread, into which the support legs  51  may be screwed, are provided in the bottom side of the respective fundamental beams  2 ,  3  and  4 . Thus, by screwing a support leg  51  into the respective fundamental beam  2 ,  3  or  4  or unscrewing it, the distance of the bottom side of the support leg  51  from the fundamental beam can be continuously adjusted. 
   Two spirit levels  52  are mounted on the machine frame in two different positions. The spirit levels  52  are attached to the device  1  such that they are aligned in a stationary way. In the shown embodiment both spirit levels  52  are arranged in a plane, which is in parallel to the horizontal plane. In this plane, they have an angle of about 90° to one another. Both spirit levels indicate whether the device  1  is optimally aligned with respect to the horizontal plane. For an alignment of the device  1  the height of each of the three support legs  51  can be changed. The change of the alignment of the device  1  can be visually controlled by the spirit levels  52 . The components inside of the device are pre-adjusted with respect to each other. As they are rigidly mounted in the frame system and because of the stiff frame construction of the device  1  their relative position is maintained. Thus, after an alignment of the device  1  all components, for which an exact spatial positioning with respect to each other is necessary for a proper function, are in the correct relative position. The spirit levels facilitate an upright positioning of the device. As a result a fast and efficient alignment of the device  1  after a transport or a change of its position is possible. The construction having three fundamental beams  2 ,  3 ,  4  and corresponding support legs  51  contributes to the fact that the device  1  can be aligned in few steps. 
   Optical System 
   Based on  FIGS. 1 ,  2  and  4  in the following the optical system is described in more detail. The energy source, which is designed as laser  6 , is arranged in one of the vertical fundamental beams  2  of the machine frame or parallel to such a fundamental beam and is adjustably connected with it, as can be seen in  FIG. 1 . The beam  9  that is emanated from the laser  6  is guided through a pipe  13 . One end of the pipe  13  is connected to the casing of the laser  6  and the other end of the pipe is connected to a casing  14 , which encloses the deflection mirror  7  and further components. Thus, the beam  9  runs from the laser  6  to the deflection mirror  7  in a vertical direction. The casing  14  comprises a sidewall  14   a  that can be removed from the casing  14 , as can be seen in  FIG. 4 .  FIG. 2  shows the casing  14  having the sidewall  14   a  removed. 
   As can be seen in  FIGS. 2 and 4  an end of the casing  14  that is facing away from the pipe  13  is connected to an input side of the scanner  8  and the casing  14  is fixedly connected to the components of the machine frame. Thus, the pipe  13  and the casing  14  are arranged such that the beam  9  from the laser  6  runs to the scanner  8  inside of the pipe  13  and the casing  14  in a space that is secluded from the outside. A shutter  15 , which is only schematically shown in the figures, is provided at the joint between the pipe  13  and the casing  14 . The shutter  15  is designed such that the optical path of the beam  9  from the laser  6  to the deflection mirror  7  is interrupted, when the sidewall  14   a  is removed from the casing  14 . By this construction it is guaranteed that no injury to an operator occurs inadvertently due to inattention, when the energy source operates and the sidewall  14   a  is removed. In the embodiment the shutter  15  is implemented by a mechanical slide, which blocks a beam passage from the pipe  13  to the casing  14 , when the sidewall  14   a  is removed. 
   As can be seen in  FIGS. 1 and 2 , the deflection mirror  7  deflects the beam  9  to an entrance region  8   a  of the scanner. The deflection mirror  7  is suspended such that its alignment can be adjusted and it is provided with an adjustment mechanism  16  for adjusting its alignment. The adjustment mechanism  16  includes two actuators  17  and  18 , each of which is arranged such that a drive  17   a  and  18   a , respectively, of the actuators  17  and  18  is located outside of the casing  14 . Thus, the drives  17   a  and  18   a  can be accessed from the outside when the casing  14  is closed and the alignment of the deflection mirror  7  can be changed, when the casing  14  is closed. In the shown embodiment each of the actuators  17  and  18  is designed as mechanical set screw, which has a scale in the region of the drives  17   a  and  18   a , which scale corresponds to the alignment of the deflection mirror. The drives  17   a  and  18   a  are designed as adjusting knobs. In the shown embodiment the actuators  17  and  18  are manufactured by a laser sintering method. The adjusting knobs are lockable in order to prevent an inadvertent adjustment. 
   For an optimal functioning of the device an exact adjustment of the alignment of the beam  9  to the entrance region  8   a  of the scanner is necessary. To this end apertures  19 ,  20 ,  21 , which are integrated in the casing  14  and may be brought into the optical path, are provided. In the shown embodiment three apertures  19 ,  20 ,  21  are provided in the casing. However, also a higher or a lower number of them may be provided. In the embodiment the aperture  19  close to the deflection mirror  7  and the aperture  21  close to the entrance region  8   a  of the scanner  8  both are designed as apertures having a reticle as shown in  FIG. 3   a . Further, the aperture  20 , which is arranged therebetween, is designed as pinhole, as shown in  FIG. 3   b . For varying adjustment requirements there are also other designs of the apertures possible. Moreover, also several sets of apertures may be provided, which may be replaced depending on the requirement for a necessary adjustment. Depending on the energy source that is used for the beam  9 , instead of the mechanical apertures also other elements may be provided, which are known to the skilled person and which are able to detect the position of the beam such as optical sensors for the detection of the position of the beam. 
   Each of the apertures  19 ,  20 ,  21  is swivel-mounted on its retainer  19   a ,  20   a  and  21   a , respectively, that is mounted at the casing  14 . In a first setting they are brought into the optical path and fixed. In a second setting they are removed from the optical path and fixed. The suspension of the apertures can e.g. be implemented by means of an axis, around which the apertures  19 ,  20  and  21  are rotatable in a direction which is perpendicular to the optical path. The fixing of the apertures  19 ,  20 ,  21  in their respective settings can, for example, be done by means of a knurled head screw, which is screwed onto this axis. However, many different ways of suspension are possible that are obvious to the skilled person due to his expert knowledge. For instance, a mechanism is possible, in which the apertures can be engaged in both positions. 
   As is merely schematically shown in  FIG. 1 , the scanner  8  is also attached to another component of the machine frame. In the shown embodiment the scanner  8  is mounted to a cross bracing  5 . In the embodiment the scanner  8  is suspended such that an adjustment of the alignment of the scanner is possible by rotating it around an axis that is parallel to the optical path from the deflection mirror  7  to the entrance region  8   a  of the scanner. For this adjustment an adjustment mechanism  8   b  is provided. This makes an easy and quick fine adjustment of the alignment of the scanner  8  possible. 
   The beam  9  from the laser  6  to the scanner  8  is deflected only once. It is deflected via the deflection mirror  7 , wherein the alignment of the deflection mirror  7  can be adjusted, when the casing  14  is closed. This leads to an optical path that can easily be adjusted by adjusting the position of few components. Thus, in the shown embodiment only an adjustment of the position of the laser  6 , of the deflection mirror  7  and of the scanner  8  is necessary. The position of the laser  6  can be adjusted via an adjustment mechanism  6   b . Each one of the laser  6 , the deflection mirror  7  and the scanner  8  is directly fixed at the components of the rigid frame system. Therefore, in the event of a transport or a change of location of the device  1 , the laser  6 , the deflection mirror  7  and the scanner  8  do not change their relative positions to each other or do only slightly change their relative positions. Accordingly, a fine adjustment can be done within a short time and thus in an efficient way. 
   For an adjustment of the optical path each one of the apertures  19 ,  20  and  21  can be brought into the beam path individually or in combination with the other apertures. This additionally improves the possibility of adjusting the optical path in a quick and efficient way. Thus, it is possible to save costs when commissioning and servicing the device  1 , because there is less effort necessary for an adjustment. 
   Method for Adjusting the Beam 
   Possible methods for adjusting the beam path are described. 
   In one method one of the two reticle apertures  19  and  21  is brought into the optical path and an illumination paper is inserted immediately behind the reticle. Then, the illumination paper is illuminated with a laser pulse and the shadow image of the reticle is evaluated. The centre of the beam cross-section should be exactly coincident with the centre of the cross. The beam path is readjusted by adjusting the alignment of the deflection mirror  7  via the actuators  17  and  18  and by adjusting the position of the laser  6 . This method is suitable also in a case, in which the beam path initially deviates very much from the desired path. When using this method it is also possible to additionally insert the pin hole  20  into the beam path. 
   In a method for readjusting the optical system the aperture  20 , which is designed as pin hole, is inserted into the optical path and afterwards the casing  14  is closed. A power measuring device, which measures the total power of the beam  9 , is positioned in the building plane  11 . The scanner  8  is driven in such a way that the beam  9  for the case of an exact adjustment would be optimally directed to the power measuring device. The beam power, which is measured by the power measuring device, is monitored and the alignment of the deflection mirror  7  is varied by operating the actuators  17  and  18 . The alignment of the deflection mirror  7  is varied until the power measuring device measures the maximum beam power. In such position the beam  9  is optimally directed to the entrance region  8   a  of the scanner  8  by the deflection mirror  7 . This method can also be performed without any pin hole, so that the entrance opening at the scanner  8  takes over the function of an aperture. 
   This way of adjustment makes possible a simple and quick adjustment of the beam path in a case, in which only a small mutual change of the positions of the components of the optical system has occurred and merely a fine adjustment is necessary. By the method an adjustment can be carried out within a short time and the costs of the adjustment in a commissioning and in a service can be reduced. Depending on the adjustment requirement it is also possible to perform this method without an initial insertion of the pin hole  20  into the optical path. In this case there is a further saving of time and the labor costs are reduced. 
   In a further method a layer  110  of a material that is sensitive for an irradiation with the beam  9 , e.g. a paper that changes color by a temperature effect, is positioned in a defined region in the building plane  11 . At few selected positions at the edge of the construction field, which is to be irradiated by the laser  9  in a manufacturing process, the layer  110  is provided with marks  111 , as shown in  FIG. 14 . Afterwards those positions, which for a correct adjustment would correspond to the marks  111 , are exposed to the beam  9  via the scanner  8 . Then the deviations of the exposed positions from the marks  111  on the layer  110  in two directions are determined. In its simplest way the measurement can be performed for example by a ruler. On the basis of the measured boundary points it is then determined, whether with respect to the optical adjustment for example magnification errors or a tilting occurred. The errors that occurred can be determined for example by feeding the measured values into a corresponding evaluation program. 
   Magnification errors may e.g. result from mechanical distance variations between the scanner  8  and the construction field in the building plane  11  or from an electronic drift of the electronic components of the scanner  8 . Tilting errors may e.g. result from mechanical distance and angle variations, respectively. Magnification errors and/or tilting errors that have been found, depending on the error that has been found, may be compensated by the above-described fine adjustment such as a readjustment of the horizontal alignment of the scanner  8 , or by calculating correction parameters, which are used for correcting the aiming points of the laser  9  by programming in a control program for driving the scanner  8 . 
   In the method only individual measurement points at the edge of the construction field are measured. For points of the construction field between the measurement points a determination of the error is done by interpolation. The error correction for points between the measurement points is also done by interpolation. Thus, only few measurement points have to be recorded, which may be done in a short time and with a small effort. Accordingly, the labor time incurred for adjustment and service work can be considerably reduced and therefore also the operating costs incurred can be lowered. 
   Laser and Optics Cooling 
   With respect to  FIGS. 1 ,  2  and  4  in the following a ventilation system for the optical system is described. 
   Inside of the fundamental beam  2  there is a hollow space  53 , in which the laser  6  and the pipe  13  are located. Two ventilators  54  are provided. The ventilators  54  generate an airflow T that leads away warm air from the laser  6  and therefore cools it. In the embodiment the ventilator  54  is provided in the region of the pipe  13  in the hollow space  53 . The hollow space  53  is connected via two tubes  55  to the region of the device  1  above the building space  10 , in which building space  10  the scanner  8 , the deflection mirror  7  and the apertures  19 ,  20 ,  21  are provided. 
   As can be seen in  FIG. 5 , the airflow T is directed by the ventilator  54  to the upper partition wall  56  of the building space  10 . Thus, the airflow for cooling the energy source is also deflected towards the optical system. 
   The cooling system for cooling the energy source designed as laser  6  thus is used in the embodiment at the same for cooling the optical system, which comprises the scanner  8 , the deflection mirror  7  and the apertures  19 ,  20  and  21 . Therefore, it becomes possible to cool all components of the optical system with one ventilation system. 
   As the airflow T is also led onto the upper partition wall  56  of the building space  10 , the same ventilation system can also serve for a cooling of the upper side of the building space  10  and a too strong heating of control components of the device  1 , which are located above the building space  10 , can be prevented. The cooling of the upper side of the building space  10  is done by means of the ventilation system of the optical system. Therefore, no separate cooling needs to be provided, because the cooling system of the laser can be also used for leading process heat from the building process to the outside of the device  1 . Thus, costs can be saved and the device can be built in a compact way. 
   In this embodiment the hollow space  53 , in which the laser  6  is located, is connected to the upper side of the building space or construction space  10  by means of two tubes. However, it is e.g. also possible to implement a connection via flow channels in the machine frame itself. It is also possible to merely provide one tube or one connection channel. Though two ventilators  54  are described, depending on the necessary cooling capacity also merely one ventilator or a plurality of ventilators  54  may be provided. The arrangement of a common ventilation system for the optical system and for the upper side of the building space  10  is not limited to a construction, in which the energy source is a laser or in which the energy source is located in the fundamental beam  2 . The effect of an efficient and cost-effective cooling of the optical system and of the upper side of the building space is also achieved when using other arrangements. However, the arrangement of the energy source in a fundamental beam of the frame enables a space-saving implementation. 
   In the following individual components of the device  1  in the building space  10  are described. 
   Heating Device 
   A heating device  31  for heating the powder bed in the container  25  and in particular for pre-heating a layer that has been applied but not yet solidified is arranged in the building space  10  above the building plane  11 , as is shown in  FIG. 5 . The heating device is designed for example as one radiant heater or a plurality of radiant heaters such as (an) infrared radiator(s), which is/are arranged above the building plane  11  such that the applied layer of the building material can be uniformly heated. In the shown embodiment the heating device  31  is designed as a two-dimensional radiator having a heat radiating element that is composed of a graphite plate. As can be seen in  FIG. 8 , the heat radiating element has a meandering structure. 
   In the shown embodiment the heating device  31  being a substantially square plate having a substantially square cut at its centre below the entrance window  12  extends around the area, through which the beam  9  from the scanner  8  to the building plane  11  passes. 
   The mounting of the heating device  31  is described with respect to  FIG. 8 . As is shown in  FIG. 8 , the heating device  31  in the embodiment consists basically of a fixture  44  and of the radiant heater  45 . The fixture  44  is received in a support  46  that is arranged in the upper region  40  of the building space  10 . The radiant heater  45  is received in the fixture  44 . 
   As is schematically shown in  FIG. 8  by the arrows A, the fixture  44  can be removed together with the radiant heater  45  from the support  46 . The support  46  is designed as a rail, into which the fixture  44  is inserted. The fixture  44  can be inserted into the support  46  and removed from it without a tool. Several designs are possible for the connection between the fixture  44  and the support  46 . An attachment may be effected for example via springs, clamps or the like. There may be provided structures, wherein the fixture  44  is engaged in the support  46 . 
   The fixture  44  also has a rail-like structure, into which the radiant heater  45  is inserted. The radiant heater  45  can be introduced into the fixture  44  and can be removed from the fixture  44  without a tool. Again, as it was the case for the connection between the fixture  44  and the support  46 , different kinds of connection between the fixture  44  and the radiant heater  45  are possible. An engagement of the radiant heater  45  in the fixture  44  may be provided. 
   Thus, the described design of the support  46 , the fixture  44  and the radiant heater  45  on the one hand makes possible to remove the fixture  44  from the radiant heater  45  without the use of a tool. This is particularly advantageous for cleaning the building space  10 . On the other hand the radiant heater  45  can be removed from the fixture  44  without using a tool. This is particularly advantageous for the service and the replacement of the radiant heater  45 . The removal or replacement without tools of components of the heating device  31  enables a quick and uncomplicated cleaning of the device  1  and a quick and uncomplicated replacement of the radiant heater  45 . Thereby, time can be saved during service and cleaning work and the device  1  will be again available for the next working process within a shorter time. 
   Dosage Device 
   As is schematically shown in  FIG. 5 , in the shown embodiment each of the dosage devices  28  and  29  is formed in the shape of angulated plates, which extend over the whole width of the building plane  11  in a direction, which is perpendicular to the plane of  FIG. 5 . The dosage devices  28  and  29  can be rotated like a roll around an axis that is running in parallel to the building plane  11 , and each of the dosage devices  28  and  29  represents a conveyor roller. The dosage devices  28 ,  29  are formed in such a way that by the movement of the application device  27  they are driven such that they rotate by a defined angle around their axis. 
   The dosage device  28  is schematically shown in  FIG. 7 . The dosage device  29  is similar to the dosage device  28  and is not described in detail. The dosage device  28  can be removed from the device  1  and can be re-inserted without a tool. As is shown in  FIG. 7 , the dosage device  28  comprises a central portion  28   c  that is formed in the shape of an angulated plate and extends along the axis of rotation Z. The central portion  28   c  serves for dosing a defined amount of a building material. Further, the dosage device  28  comprises a first end  28   a , which in the direction perpendicular to the axis of the rotation Z has a smaller cross-section than the central portion  28   c . A second end  28   b  of the dosage device  28  also has a smaller cross-section than the central portion  28   c  in the direction perpendicular to the axis of rotation Z. The first end  28   a  of the dosage device  28  is connected to a suspension  36  around which the dosage device rotates or together with which the dosage device  28  rotates around the axis of rotation Z. For that purpose the first end  28   a  and the suspension  36  are connected with each other in a positive or form-locking way. In the shown embodiment the first end  28   a  has e.g. a cylindrical protrusion  28   a ′, which is positively inserted into a recess  36 ′, which is also cylindrical, in the suspension  36 . However, the suspension  36  and the first end  28  can be designed in a different way. For instance the first end  28   a  may have a recess and the suspension may have a protrusion. The recess and the corresponding protrusion may e.g. also have any other shape that leads to a form-locking connection. 
   The second end  28   b  of the dosage device  28  is connected to a bearing  37 . The second end  28   b  is pivot-mounted by the bearing  37 . In the shown embodiment the bearing  37  has an annularly protruding edge  37   a  that is concentrical to the axis of rotation Z. The second end  28   b  is designed as cylinder-shaped protrusion, which is inserted into the recess that is formed by the annularly protruding edge  37   a . However, also other designs of the bearing  37  and the second end  28   b  are possible. The bearing  37  can e.g. be designed as protruding pivot and the second end  28   b  may have a recess that is engaged by the pivot. For enabling a pivoting of the dosage device  28  several implementations are possible. 
   Moreover, in the shown embodiment a preload element  38  is provided on the side of the second end  28   b  between the dosage device  28  and the bearing  37 , wherein the preload element  38  preloads the dosage device  28  towards the suspension  36 . In the embodiment the preload element  38  is formed by a helical spring that is provided coaxially to the axis of rotation Z on or around the edge  37   a  and the second end  28   b . However, alternative embodiments are also possible. For instance, the pre-load element can be designed in the shape of a leaf spring, the preload element can be provided in the bearing  37  or in the second end  28   b  and the second end  28   b  itself can be moveably mounted on the dosage device  28  by the preload element. 
   In the shown embodiment the distance between the bearing  37  and the suspension  36  is larger than the length of the dosage device between the first end  28   a  and the second end  28   b  by a predetermined distance. The predetermined distance is slightly larger than the length of the protrusion  28   a ′ in the direction of the axis of rotation Z. Due to this design the dosage device  28  can be moved against the preloading force of the pre-load element  38  into the direction of the bearing  37 , so that the form-locking engagement between the first end  28   a  and the suspension  36  can be released. Then the dosage device  28  can be taken out and can e.g. be cleaned or be replaced by another dosage device. The insertion of the dosage device  28  takes place by using the reversed sequence of method steps. 
   Thus, the described embodiment makes it possible to remove the dosage device  28  without the use of a tool. The removal and the replacement of the dosage device  28  without a tool enable a quick and uncomplicated cleaning of the device  1  and a quick and uncomplicated replacement of the dosage device  28 . Thereby time can be saved during service and cleaning work and the device is again available for the next production process within less time and the operating costs of the device  1  can be lowered. 
   Alternatively, e.g. the bearing  37  and/or the suspension  36  may be configured as a drive shaft, which drives the dosage device such that it rotates. In such a case a form-locking connection can also be used between the second end  28   b  and the bearing. 
   The receptacles on both sides of the dosage device  28 , in which the latter is mounted, can for example be designed as recesses, into which the dosages device  28  is laterally inserted. A fixing can for example be achieved by the using of springs, clamps and the like. There may be provided structures, in which the dosage device  28  engages in its mounting. The dosage device  28  can e.g. also be fixed by means of a knurled head screw that may be tightened and released by hand. 
   Building Material Supply/Thermal Protection 
   With respect to  FIG. 5  the region of the dosage devices  28  and  29  in the building space  10  is described. 
   In the region of the dosage device  29  a building material accommodation region  23  is formed, which is extending beneath a plane, within which the building plane  11  is located. The building material accommodation region  23  is formed such that it can accommodate a limited amount of building material that is supplied by the application device  27 . In the region of the dosage device  29  and the supply opening  30  a building material accommodation region  24  is formed. The building material accommodation region  24  is dimensioned such that it can accommodate the building material, which is supplied via the supply opening  30 , and also the building material that is returned by the application device  27 . 
   The dimensions of the building material accommodation regions  23  and  24  and of the dosage devices  28  and  29  are matched to each other such that by each turn of the dosage device  28  or  29  by 180° a defined amount of the building material is moved in front of the application device  27 . 
   As is shown in  FIG. 5 , above the dosage devices  28  and  29  radiation protection shields  32  and  33 , respectively, are mounted. The radiation protection shields  32  and  33  prevent a heat radiation from the heating device  31  from directly acting on the building material that is located in the region of the dosage devices  28  and  29  and in the region of the supply opening  30  and in the building material accommodation regions  23  and  24 . 
   The lower side of the building material accommodation regions  23  and  24  is provided with a double wall structure, by which hollow spaces  34  and  35  are formed. The hollow spaces extend across the whole lower side of the building material accommodation regions  23  and  24 . By this double wall structure the building material accommodation regions are bottom-insulated with respect to the components of the device  1  located beneath them. According to one embodiment a fluid can be circulated through the hollow spaces  34  and  35  in order to adjust the temperature of the building material in the building material accommodation regions  23  and  24 . Also, a control device may be provided that controls the flow rate of the fluid through the hollow spaces  34  and  35  and/or the temperature of the fluid. By providing such a control device the temperature of the building material can be controlled. 
   By providing the radiation protection shields  32  and  33  and the hollow spaces  34  and  35  the temperature of the building material in the area of the dosage devices  28  and  29  and the powder accommodation regions  23  and  24  can be kept at a lower value than the temperature of the building space above the building plane  11  and the temperature of the region below the container  25 . 
   Thus, by providing the hollow spaces  34  and  35  and the radiation protection shields  32  and  33  a too high rise of the temperature of the building material in the building material accommodation regions  23 ,  24 , which is not desired, is prevented. Thereby the danger of thermally affecting the properties of the building material before the building process, which is undesirable, may be reduced. 
   Application System 
   In the following the application system in the embodiment is described with respect to  FIGS. 9 and 13 . 
   As can be seen in  FIG. 13 , the application system comprises the application device  27  and a drive mechanism  59 . The application device  27  comprises the application element  61  and a holder  60 . The application element  61  is held in the holder  60 . The holder  60  is connected to the drive mechanism  59 . 
   As can be seen in  FIG. 9  the holder  60  comprises a main arm  62  and two holder arms, a first holder arm  63  and a second holder arm  64 , which are vertically extending from the main arm  62  in a downward direction. The first holder arm  63  is rigid and is fixedly connected to the main arm  62 . The second holder arm  64  has one end  64   a  that is fixedly connected to the main arm  62 . The second holder arm  64  has flexibility, such that its free end  64   b  can be moved to a limited extent against a restoring force of the material of the second holder arm  64 , as is indicated in  FIG. 9  by the arrow C. By this movement the distance between the free ends  63   b ,  64   b  of the holder arms  63 ,  64  can be increased. In each of the holder arms  63  and  64  a recess  63   c  and  64   c , respectively, is provided. 
   The application element  61  comprises a main body  61   a , which extends substantially in parallel to the main arm  62  of the holder  60 , and two protrusions  61   b , which protrude laterally from the main body  61   a . The two protrusions  61   b  are dimensioned such that they can be inserted in a form-locking way into the recesses  63   c  and  64   c  of the holder arms  63  and  64 . The form-locking engagement brings about a torque proof connection between the application element  61  and the holder  60 . In the shown embodiments the application element  61  is designed as application blade, which has a lower edge  61   c  that effects the application of the building material and a smoothing of the same. 
   As is schematically shown in  FIG. 9  by the arrows C and D, the free end  64   b  can be moved away from the free end  63   b  in the direction of the arrow C, so that the form-locking engagement between the application element  61  and the second holder arm  64  is released. Then the application element  61  can be removed from the holder  60 , as is indicated by the arrow D. 
   A mounting of the application element  61  to the holder  60  is done in the reverse order. 
   By the described design the application element  61  can be released from the holder  60  and mounted on the holder  60  in a tool-less way, i.e. without using a tool. Thereby a quick and efficient exchange of the application element  61  is made possible. Time can be saved during service and cleaning work and the device  1  is in less time again available for the next production process. In particular, different application elements  61  can be used for subsequent building processes depending on the respective requirements and these application elements  61  can be changed between the building processes with a small effort. 
   Other configurations for connecting the application element  61  with the holder  60  are possible. For instance, recesses may be provided at the application element  61  and protrusions may be provided at the holder  60  for a form-locking connection. For instance, also an insertion into a groove and optionally an engagement between the application element  61  and the holder  60  may be provided. 
   The drive mechanism  59  of the application system  27  is described with respect to  FIG. 13 . As can be seen in  FIG. 13 , the holder  60  of the application device  27  is connected to a drive shaft  65  in a torque proof way. The drive shaft  65  is pivot-mounted at its ends in bearings  66  and  67 . The drive shaft is rotatable around an axis E that is perpendicular to the building plane  11 , which is shown in  FIG. 5 . The rotation is indicated by the arrows F in  FIG. 13 . Further, a lever  68  is mounted on the drive shaft  65  in a torque proof way. The lever  68  is connected to an actuation piston-cylinder system  69 . Further, the lever  68  is connected to a break piston-cylinder system  70 . In the embodiment the actuation piston-cylinder system  69  is designed as pneumatic system, which drives the drive shaft  65  such that the drive shaft  65  rotates around the axis E, when the piston is charged with pressure via the lever  68 . The rotation of the drive shaft  65  results in a rotation of the holder  60 , so that the application element  61  is set in motion in parallel to the building plane  11 . The drive shaft  65  is arranged laterally to the construction field or building field, in which the solidification of the building material is carried out, in the back region of the building space. Via the drive mechanism  59  the application device  27  can be moved on a path across a limited angular range, wherein the path corresponds to a sector of a circle. Thus, the application device  27  is moved back and forth on a circular path between a first position on one side of the construction field and a second position on the opposite side of the construction field. Due to this configuration the drive mechanism  59  for moving the application device  27  is arranged substantially on one side of the construction field and an unimpeded access to the construction field from the opposite side is ensured. By providing the pneumatic system as drive the motion of the application device can be implemented with high precision and at the same time at a low cost. 
   The break piston-cylinder system  70  is designed as an oil dashpot. The break piston-cylinder system  70  effects a damping of pressure variations, when the actuation piston-cylinder system is charged, or of variations of the resistive force that is countering the drive, which changes would effect an abrupt change of the velocity of the application device  27 . Thus, a uniform movement of the application device  27  with a predetermined velocity profile is enabled. The optimized motion of the application device  27  leads to an improved uniform application of a layer and thus to an improvement of the part quality. 
   In the embodiment an application device  27  is described, which moves on a circular path around the axis E in parallel to the building plane  11 . The circular path is dimensioned such that the application device  27  performs a movement across the whole building plane  11 . The application device can also be configured such that a linear movement across the building plane  11  is implemented. In this case the combination of the actuation piston-cylinder system  69  with the break piston-cylinder system  70  also leads to a more uniform movement of the application device and thus to an improved layer application. 
   Replacement Container/Suspension 
   The configuration of the container  25  in the embodiment is described with respect to  FIGS. 5 and 10 . In  FIG. 5  the container  25  having the support device  26  arranged therein is only shown schematically. 
   In the embodiment the container  25  is designed as a replacement container or swap container, which can be taken out of the device  1  together with the support device  26 , which forms a building platform and is located therein. A coupling mechanism that is not shown is provided in the device  1 . By the coupling mechanism the connection of the support device  26  and the container  25  to the drive for vertically moving the support device  26  can be established and released. This coupling mechanism is driven by a control of the device  1 . The coupling mechanism can be configured such that it is similar to the one that was described in the prior art mentioned in the introduction. 
   As is schematically shown in  FIG. 10 , a mounting  74  is provided at a door  73 . The door  73  is swivel-mounted at the machine frame of the device  1  and in a closed state secludes the building space  10  of the device  1  from the outside of the device  1 . In the embodiment the door  73  is mounted at one side such that it can be pivoted around an axis G as is indicated by the arrow H. In the shown embodiment the axis G runs vertically, so that the door  73  of the device  1  swings open to the side. 
   The container  25  comprises on the one side an attachment  75 . The attachment  75  can be brought into an engagement with the mounting  74  in the door  73  such that the container  25  is supported at the door  73  and together with the door  73  can swing open from the machine frame. In the shown embodiment the mounting  74  is formed on the inner side of the door  73  as a protrusion that has a recess at its top side. The attachment  75  at the container  25  is designed as a protruding hook, which engages into the recess. 
   In order to insert the container  25  into the device  1  the attachment  75  of the container  25  is engaged with the mounting  74  with the door  73  being open. This procedure can be comfortably carried out, because the mounting  74  is easily accessible from the outside of the device  1 , when the door  73  is open. The container  25  is decoupled from the mounting  74  via the coupling mechanism by means of the control of the device  1 . The support device  26  is connected to the respective drive. 
   In this state the container  25  is not connected with the door  73  and the door  73  can be opened if necessary without taking the container  25  out of the device  1 . On the other hand by the control of the device  1  the container  25  can be re-engaged with the mounting  74  and the support device  26  can be decoupled from the respective drive. In this state the container  25  can be moved out of the building space  10  and out of the device  1  by opening the door  73 . The container  25  swings out together with the door  73 . In this position the container  25  can be comfortably taken out of the device, wherein it is not necessary to reach into the inside of the machine. 
   Though in the embodiment the door  73  is swivelled around a vertical axis, it is e.g. also possible to provide a door that opens horizontally in a different way. Moreover, the connection between the door  73  and the container  25  is not limited to the described embodiment having recess and an engaging hook. Also other mechanisms can be provided that enable an engagement of the door  73  with the container  25 . 
   Building Platform Sealing 
   The guide of the support device  26  in the container  25  is described with respect to  FIG. 11 . As was already described with respect to  FIG. 5 , the support device  26  can be moved in a vertical direction K relative to the container  25  via a drive. The upper side of the support device  26  forms the building platform  78 , on which the three-dimensional object to be formed is generated layer-wise. Between the building platform  78  and the inside wall  79  of the container  25  there is a gap  80  that is dimensioned such that the support device  26  can be moved inside of the container  25  in a vertical direction. There is the danger that the building material gets from the region of the building platform  78  via the gap  80  into the region in the container  25  underneath the building platform  78 . The passing of building material is however not desired, because a contamination of the drive may occur and as a result service work will be necessary. 
   In order to avoid a passing through of building material, the gap  80  is closed by a seal  81  that is described in the following. The seal  81  is formed by a layer of a flexible material, which is annularly arranged along the edge of the building platform  78  underneath the building platform  78 . The seal  81  is for example made of a flat strip of a silicone material. However, also other materials, which have a sufficient temperature resistance and flexibility, are possible. In a flat state the seal  81  has an outer dimension in the plane perpendicular to the movement or shifting direction K, which is slightly larger than the inner dimension of the container  25 . Thus, when it is inserted in the container  25 , the seal  81  is slightly bent in the zone of the gap  80  and butts against the inside wall  79  of the container  25  with a small tension due to the flexibility of its material. 
   Underneath the building platform  78  a guide plate  82  is arranged under the seal  81 . In a plane, which is perpendicular to the direction of movement K, the guide plate  82  has a slightly larger outer dimension than the building platform  78 . The circumferential outer edge  82   a  of the guide plate  82  is angled towards the gap  80 . The outer edge  82   a  butts against the seal  81  in the zone of the gap  80 . The outer edge  82   a  bends the seal  81  in the region of its outer circumference, so that the edge of the seal  81  in the gap is angled towards an upper boundary of the space. Even when the building platform  78  is moved in a direction opposite to the bending direction of the angulated edge region of the seal  81 , the guide plate  82  prevents the flexible seal  81  from folding down in its edge region opposite to its pre-shaped direction. Thus, it is ensured that the support device  26  together with the building platform  78  can be reliably shifted relative to the container  25  in the shifting direction K. Moreover, a passing of particles of the building material into the region underneath the building platform  78 , which would be able to occur when the seal folds down, is prevented. 
   Further, the guide plate  82  having the angled edge region  82   a  has the effect that a plane plate made of e.g. silicone can be used as seal  81 . The seal  81  can e.g. also be made from a different plastic. Based on this implementation the seal need not have at its outer edge in the circumferential direction a special structure or shaping that is adapted to the exact dimension of the inner diameter of the container. 
   Tempering of the Container 
   The lower region  41  of the building space  10  is described with respect to  FIGS. 5 and 6 . As can be seen in  FIG. 5 , a chamber  85  is formed in the lower region  41 , wherein the chamber  85  surrounds the lower side of the container  25 . When operating the device  1 , the chamber  85  is filled with a fluid medium. In the embodiment the fluid medium is a gas. In particular, in one embodiment this gas is an inert gas, which is also used in the upper region  40  in order to prevent a deterioration of the building material by e.g. oxidation. 
   The chamber  85  is laterally limited by side walls  86  and at the top is separated from the upper region  40  of the building space  10  by a separating plate  87  at the height of the building plane  11 . The chamber  85  is bounded below by a bottom  88 . The bottom  88  comprises a passage  89  for a connection of the support device with its drive in the region below the container  25 . In the bottom  88  in a region under the corners of the container  25  outlets  90  are provided. In the shown embodiment under each corner of the container  25  two outlets  90  are provided. However, also a different number of outlets may be provided, e.g. only one outlet may be provided for each corner. 
   Moreover, in the side walls  86  openings  91  are provided in the upper part, as can be seen in  FIG. 5 . The openings  91  are connected to the outlets  90  via a ventilation system. In the embodiment the ventilation system is arranged outside of the chamber  85  and is formed by a second chamber  84  outside of the side walls  86  and under the bottom  88 . A ventilator  92  is located in the ventilation system. Moreover, a heating device  93  and a temperature sensor are provided in the ventilation system. By the ventilator  92  the fluid medium in the lower region  41  is sucked through the openings  91  into the second chamber  84  and a directed flow of this medium is re-introduced through the outlets  90  into the chamber  85 . Due to the positioning of the outlets  90  underneath the corners of the container  25  and due to the openings  91  in the side walls  86  a directed flow is generated in the region of the corners of the container  25 , which directed flow effects a temperature adjustment or balancing of the container  25 . This flow is indicated by the arrows S in  FIGS. 5 and 6 . By this flow the temperature profile of the container  25  can be defined and a uniform tempering of the container  25  is possible. By providing the heating device  93  and the temperature sensor an exact adjustment of the temperature of this flow is possible. Thus, the temperature of the container  25  and of the building material located therein can be adjusted in a defined way during the operation of the device  1 . The flow causes a heat exchange between the fluid medium and the container  25 , in particular in the corners of the latter. Based on the corners the temperature profile of the container  25  can be kept particularly homogenous in an advantageous manner. 
   By the selective tempering of the corners of the container by means of the directed flow a controlled cooling of the solidified building material and the surrounding non-solidified building material in the container  25  can be carried out during the operation. Thus, when the building material cools down, extreme temperature gradients, which would lead to a deterioration of the manufactured three-dimensional objects by warping during the cooling down, can be prevented. 
   In the embodiment the same process gas that is also used in the upper region  40  of the building space  10 , which is the actual building region, is used as fluid medium. Thus, a particular sealing between the upper region  40  and the lower region  41  of the building space  10  is not necessary. Thus, a cost-effective construction of the device  1  is made possible. Further, also a thermal aging of the building material in the container  25  is prevented in a higher degree. This is also particularly advantageous with respect to a recycling of the non-solidified building material in a further building process. 
   Building Material Supply 
   The supply of the building material to the device  1  is described with respect to  FIGS. 1 ,  12  and  15 . As can be seen in  FIG. 1 , in the backward region of the device  1  an opening  95  for feeding the building material is formed. The opening  95  is connected to the supply opening  30 , which leads to the building space  10  and is shown in  FIG. 5 . In the device  1  in the region of the opening  95  a duct  96  is formed. Via the duct  96  the building material is supplied to the supply opening  30 . In the embodiment the supply is effected based on the intrinsic weight of the building material by drop delivery. The upper region of the duct  96  is schematically shown in  FIG. 12 . 
   The duct  96  has a cover wall  97  at its top side, wherein in the cover wall two openings  97   a  and  97   b  are provided in order to be connected to filler pipes  98   a  and  98   b  for a building material supply. The filler pipes  98   a  and  98   b  have at its upper side connectors  99   a ,  99   b  for building material supply containers  100   a  and  100   b , respectively. The connectors  99   a  and  99   b  can be separately connected to the building material supply containers  100   a  and  100   b . In each of the filler pipes  98   a ,  98   b  a gate  101   a  and  101   b , respectively, is provided. Each of the gates  101   a ,  101   b  can be moved into a first position, in which the cross-section of the corresponding filler pipe  98   a  and  98   b , respectively, is closed, as it is shown on the left side in  FIG. 12 . The gates  101   a ,  101   b  can also be moved to a second position, in which the cross-section of filler pipe  98   a  and  98   b , respectively, is not closed or covered and building material can pass from the building material supply container  100   a  and  100   b , respectively, to the duct  96 . 
   In the duct  96  below the openings  97   a  and  97   b  filling level sensors  102   a  and  102   b , respectively, are mounted. The filling level sensor  102   a  detects, whether building material is in the duct  96  below the filler pipe  98   a . The filling level detector  102   b  detects, whether there is building material in the duct below the filler pipe  98   b.    
   Each of the filler pipes  98   a  and  98   b  is provided with a mechanism, by which it can be moved above the duct  96  and can be moved away from the duct  96 , respectively, together with a building material supply container  100   a  and  100   b , respectively, as is schematically shown in  FIG. 15 . Both filler pipes can be moved independently. In the embodiment this motion is a swiveling around an axis that is substantially horizontal. 
   In operation the duct  96  is initially filled with building material. A building material supply container  100   b  is also filled with building material and the corresponding gate  101  is in the open position. A column of the building material extends within the duct  96  to a position, which is higher than the respective filling level sensor  102   b . The second building material supply container  100   a  is also filled with building material. However, the respective gate is still in the closed position, as is shown in  FIG. 12 . 
   When operating the device  1 , building material is consumed and the filling level in the duct  96  falls, because the building material is supplied to the building space  10  via the supply opening  30  due to its weight. As long as there is building material in the building material supply container  100   b , this building material slides along into the duct  96 . When the building material supply container  100   b  is empty and the device  1  is further operated, the filling level in the duct  96  falls on the side of the filling level sensor  102   b . Then the filling level sensor  102   b  detects that the building material supply container  100   b  is empty. Afterwards the gate  101  in the filler pipe  98   b  is closed. The gate  101  in the other filler pipe  98   a  is opened, so that building material is supplied to the duct  96  from the other building material supply container  100   a.    
   In this position the building material supply container  100   b  can be removed from the device  1  and can be filled or can be replaced by another filled building material supply container. The connector  99   a  and  99   b , respectively, can e.g. be designed as an inside thread in the filler pipe  98   a  and  98   b , respectively, into which a corresponding outside thread at the building material supply container  100   a ,  100   b  is screwed. This enables the use of commercially available containers as building material supply containers. The filled or replaced building material supply container can again be connected with the filler pipe  98   b  and can be moved over the duct  96 , so that it is available when the other building material supply container  100   a  is empty. 
   When the building material supply container  100   a  is empty, the filling level in the duct  96  falls and the filling level sensor  102   a  detects this falling and outputs a signal to the control of the device  1 , which indicates that the building material supply container is empty. Afterwards the gate  101  in the filler pipe  98   a  can be closed and the gate  101  in the filler pipe  98   b  can be opened so that again building material from the building material supply container  100   b  can be supplied. The closing and opening of the gates  101  can be effected by the control of the device  1 . Then the building material supply container  100   a  can be exchanged. 
   Two building material supply containers  100   a  and  100   b  are provided, which can be independently connected to the device  1  via independent connectors  99   a  and  99   b . The operation of the device  1  need not be interrupted, when a building material supply container  100   a  and  100   b , respectively, is replaced or exchanged. The exchange of the building material supply container can be carried with the building process being continuously performed, when a three-dimensional object is manufactured in the building space  10 . An efficient operation of the device  1  is achieved and idle periods, in which there can be no building processes, can be reduced. The device  1  can be operated in a simpler way. During the operation a building material supply container can always be held in a filled state. 
   Further, a lid for closing the building material supply containers  100   a ,  100   b  can be provided. Then the building material supply containers may be closed before a supply to the device  1  and after an extraction. 
   By designing the filler pipes  98   a ,  98   b  such that they have connectors  99   a ,  99   b  for the building material supply containers  100   a ,  100   b , it is possible to use in the device building material supply containers, which are also suited for storing and for mixing the building material. Depending on the design of the connector commercially available containers can be used. 
   Moreover, also a plurality of building material supply containers may be provided for e.g. different building materials or for a storage of building material. In particular, a plurality of building material supply containers can be used such that the device  1  is operated with two building material supply containers and at the same time a mixing of building material is carried out in further building material supply containers. Further, the device  1  can also be provided with one connector or with more than two connectors for the building material supply containers. 
   In an embodiment the control of the device  1  is configured such that the filling level information is automatically sent electronically to the operators by the filling level sensors  102   a ,  102   b . The information can e.g. be sent via SMS or via e-mail. To this effect the device  1  has an appropriate network connection. 
   It was described that the supply of the building material is effected by using the intrinsic weight of the building material. However, the supply can also be effected in a different way. For instance, a mechanical device may be provided for the building material supply containers, which mechanical device assists in supplying the building material to the duct. For instance, a vibration device can be used, which induces a vibration of the building material supply containers  100   a ,  100   b  and of the building material therein, respectively, in order to assist the supply of building material to the duct  96 . The vibration device can e.g. be formed by one or more mechanical vibration exciters, which are arranged at the filler pipes  98   a ,  98   b  (filler portions). 
   Modifications 
   Modifications of the described device are possible. Instead of a laser a different energy source such as another light source or e.g. also an electron source or another particle source may be used. Depending on the energy source also other optical systems may be used. In the case of an electron source as energy source e.g. an electromagnetic lens and deflection system may be used. Some of the described features such as the design of the frame system can also be implemented in e.g. devices for a 3D printing using a method similar to inkjet printing or in mask exposition methods. 
   Also when using a laser as energy source, the device can e.g. be configured such that it is used in a laser sintering method or such that it is used in a laser melting method, in which the building material is locally melted. 
   A plurality of materials can be used as building material. For instance, a plastic powder such as a polyimide powder can be used or it is also possible to use metal or ceramics powders. It is also possible to use mixtures. For instance plastic-coated metals can be used.