Patent Publication Number: US-2022212266-A1

Title: Additive manufacturing machine with powder dispensing by sieving

Description:
The invention relates to an additive manufacturing machine using a powder-based additive manufacturing method. 
     More specifically, the invention falls into the domain of powder bed fusion additive manufacturing and seeks to optimize the deposition of very small quantities of powder, for example 0.5 grams, onto a working area of small surface-area—from 3 to 20 cm 2  as a rough idea of scale. 
     Application WO2017108867 describes a powder bed fusion additive manufacturing machine comprising a device able to deposit a variable profile line of powder in front of the device used to spread the powder over the working area. 
     More specifically, the machine described in application WO2017108867 comprises at least one injector for directly injecting powder over a working surface of the machine, this injector being movable with respect to the working surface along at least one transverse horizontal direction. In addition, this machine also comprises a system for regulating the amount of powder distributed by the injector. 
     According to this application WO2017108867, the amount of powder distributed by the injector can be regulated by regulating the height of the injector with respect to the working surface. For this reason, the injector is movable with respect to the working surface along a vertical direction, and the regulating system is able to regulate the vertical position of the injector with respect to the working surface. 
     The regulating system described in application WO2017108867 is unable to deposit a very small amount of powder, 0.5 grams for example, onto a working area of small surface-area—from 3 to 20 cm 2  for example. 
     Patent JP4351218 describes an additive manufacturing machine comprising a powder distribution device able to deposit a line of powder that is of variable profile or discontinuous across the width of a large working area and that can be adapted to distributing powders of different particle size and/or different fluidity. 
     For that purpose, the powder distribution device described in patent JP4351218 takes the form of a reservoir capable of translational movement along the length of the powder spreading device. Further, this mobile reservoir may be equipped with a vibrator and/or with a shut-off system preventing the distribution of powder. 
     Like the device described in application WO2017108867, the powder distribution device described in patent JP4351218 is unable to deposit a very small amount of powder, 0.5 grams for example, onto a working area of small surface-area—from 3 to 20 cm 2  for example. 
     Document CN103738747 describes a powder distribution device for an additive manufacturing machine. That powder distribution device takes the form of a mobile reservoir equipped with shut-off means and with two sensors for measuring upper and lower levels of powder in the reservoir. 
     The level sensors described in document CN103738747 provide information relating to a maximum or minimum amount of powder present inside the mobile reservoir. However, these sensors are unable to measure accurately and in real-time the exact amount of powder deposited in front of the powder spreading device. Therefore, these sensors do not allow a very small amount of powder, 0.5 grams for example, to be deposited onto a working area of small surface-area—from 3 to 20 cm 2  for example. 
     Document WO9534468 describes a powdered distribution device comprising a main reservoir connected to a powder feed hopper by a flexible pipe. The main reservoir is equipped with vibration means and comprises a powder distribution opening fitted with a screen. To complement this, the main reservoir may be equipped with a lid so that the powder distribution opening can be closed. The lid may also act as a buffer reservoir and be fitted with a sensor for measuring the amount of powder it contains, for example by measuring the weight of this powder. 
     One disadvantage is that document WO9534468 does not describe any means for managing the filling of the main reservoir from the feed hopper. 
     The key objectives of the present invention are to allow a very small amount of powder, 0.5 grams for example, to be deposited onto a working area of small surface-area—from 3 to 20 cm 2  for example, and to manage the filling of a reservoir used for powder distribution. 
     To this end, the object of the invention is a powder bed fusion additive manufacturing machine, this additive manufacturing machine comprising a working area able to receive a superposition of different layers of powder, a device for depositing a layer of powder onto the working area and a consolidation source used to selectively consolidate each layer of powder deposited onto the working area, the device for depositing a layer of powder comprising a powder reservoir able to be positioned above the working area, and a powder distribution opening being provided in the bottom part of the reservoir. 
     According to the invention, the device for depositing a layer of powder comprises a vibrating device able to subject the reservoir to vibrations, and the powder distribution opening of the reservoir is equipped with a sieve. 
     Again according to the invention, the reservoir is mounted on a weighing sensor. 
     By combining a sieve with the use of vibrations it is possible to distribute a small amount of powder, 0.5 grams for example, onto a working area of small surface-area—from 3 to 20 cm 2  for example. 
     When no vibration is applied to the reservoir, the sieve is able to keep the grains of powder in the reservoir by encouraging the grains of powder to arch. In other words, in the absence of vibrations, the sieve encourages the formation of arches of powder grains inside the reservoir, thus preventing the grains of powder from flowing. When vibrations are applied to the reservoir, the arches collapse and the grains of powder pass through the sieve at a flow rate that is limited by the mesh size of the sieve, allowing a very small amount of powder, 0.5 grams for example, to be delivered with a precision of 0.02 g. 
     Because the reservoir is mounted on a weighing sensor it is possible to achieve optimum management of the filling of this reservoir from a powder supply. 
     The invention also makes provision for the following:
         the mesh size of the sieve is comprised between 30 and 300 microns;   the surface area of the sieve is comprised between 3 and 20 cm 2 ;   the shape and surface area of the sieve are identical to the shape and surface area of the working area;   the sieve takes the form of a disc;   with the reservoir being mounted on a leaf spring, the vibrating device is mounted on the reservoir;   with a sieve being mounted on a reservoir via a ring having a shoulder to hold the sieve, the cross section of the sieve-holding shoulder decreases progressively in the direction away from the sieve;   the powder distribution opening of the reservoir is fitted with a shut-off element;   with the working area being fixed, the reservoir is mounted with the ability to move between a position in which it is situated above the working area and a position in which it is not situated above the working area;   the machine comprises a compaction device for compacting the layer of powder deposited by the depositing device on the working area;   the device for depositing a layer of powder comprises several reservoirs which are able to be positioned above a working area, each reservoir being equipped with a sieve and with a vibrating device.       

     The invention also covers a powder bed fusion additive manufacturing method performed with the machine according to the invention and the device thereof for depositing a layer of powder. 
     In the method according to the invention, a layer of powder is deposited on the working area by positioning the reservoir above the working area and then applying vibrations to the reservoir while the reservoir is situated above the working area, or by making several successive and juxtaposed deposits from various complementary positions adopted by the reservoir above a working area, vibrations being applied to the reservoir when it is situated over each one of these complementary positions, or by using the reservoir and its sieve to deposit powder in the form of a line next to the working area of the machine and in front of a powder spreading device. 
    
    
     
       Further features and advantages of the invention will become apparent in the following description. This description, which is provided by way of a non-limiting example, refers to the appended drawings, in which: 
         FIG. 1  is a schematic face-on view of an additive manufacturing machine according to the invention, with a device for depositing a layer of powder which is in position above a working area of the machine; 
         FIG. 2  is a schematic face-on view of an additive manufacturing machine according to the invention, with a device for depositing a layer of powder which is not positioned above a working area of the machine; 
         FIG. 3  is a schematic view from above of an additive manufacturing machine according to the invention having several working areas and several reservoirs for depositing a layer of powder; 
         FIG. 4  is an exploded view of a first variant of a device for depositing a layer of powder of an additive manufacturing machine according to the invention; 
         FIG. 5  is a view in section of a first variant of a device for depositing a layer of powder of an additive manufacturing machine according to the invention; 
         FIG. 6  is a view in section of a second variant of a device for depositing a layer of powder of an additive manufacturing machine according to the invention; and 
         FIG. 7  is a detailed view of the mounting of a sieve at the bottom part of a reservoir of a device for depositing a layer of powder of an additive manufacturing machine according to the invention; 
         FIG. 8  is a perspective view of a second variant of the mounting of a mobile reservoir on a weighing sensor in a device for depositing a layer of powder of an additive manufacturing machine according to the invention; 
         FIG. 9  is a view in section of a second variant of the mounting of a mobile reservoir on a weighing sensor in a device for depositing a layer of powder of an additive manufacturing machine according to the invention. 
     
    
    
     The invention relates to a powder bed fusion machine for additive manufacturing by powder bed deposition. Powder bed fusion additive manufacturing is an additive manufacturing method in which one or more parts are manufactured by the selective consolidation of various mutually superposed layers of additive manufacturing powder. 
     In a powder bed fusion additive manufacturing method, a first layer of powder is deposited on a support such as a platform, and then selectively consolidated according to a first horizontal section of the part or parts to be manufactured. Then, a second layer of powder is deposited onto the first layer of powder that has just been consolidated, and this second layer of powder is selectively consolidated, and so on, until the last layer of powder is reached that is useful for manufacturing the last horizontal section of the part or parts to be manufactured. 
     The consolidation is said to be selective because only zones of the powder layers that correspond to sections of the parts that are to be manufactured are consolidated. The consolidation is performed for example by total or partial fusion (sintering) of the grains of powder using one or more laser beams. 
     As illustrated in  FIGS. 1 to 3 , the additive manufacturing machine  10  according to the invention comprises one or more working areas  20  able to receive a superposition of different layers of powder, a device  30  for depositing a layer of powder on a working area, and a consolidation source  40  able to selectively consolidate each layer of powder deposited on a working area  20 . 
     A working area  20  is provided for example in a work surface  18  of the machine. A working area  20  is situated for example in an enclosed manufacturing chamber  16  of the machine. The work surface  18  is, for example, horizontal. A working area  20  is, for example, defined by a build sleeve  22  and a build platform  24 . For example, a build sleeve  22  extends vertically beneath the work surface  18  and opens into the work surface  18 . The build platform  24  slides vertically inside the build sleeve  22  under the effect of an actuator  26  such as a ram. As illustrated in  FIGS. 1 and 2 , the work surface  18  and the sleeve  22  may be mounted fixed, and the build platform  24  is able to move in vertical translation in the sleeve  22  under the effect of the ram  26 . In a variant (not illustrated) the build platform  24  is mounted fixed, and one or more rams are able to move the work surface  18  and the sleeve  22  in vertical translation relative to the platform. 
     The device  30  for depositing a layer of powder comprises one or more powder reservoirs  32  able to be positioned above a working area  20 . A powder distribution opening  34  is provided in the bottom part of a reservoir  32 . 
     The consolidation source  40  is, for example, a laser source emitting at least one laser beam  42 , this laser beam  42  being able to selectively melt a layer of additive manufacturing powder that has been deposited on a working area  20 . In a variant, several beams  42  may be emitted by several laser sources, such as laser diodes for example. Still in a variant, a beam  42  may be an electron beam emitted by an electron gun. One or more laser beams may also be combined with one or more beams of electrons in order to perform the selective consolidation of each layer of powder. 
     In order to allow selective consolidation of a layer of powder along paths corresponding to the section of the part or parts that are to be manufactured, a consolidation source  40  is associated with means for moving and controlling the beam or beams  42  and/or with means for moving this source. For example, optical lenses and mirrors are used to move the spot of a laser beam and modify its focus, electromagnetic coils and electrodes are used to move an electron beam and control its focus, and mechanical actuators are used to move one or more consolidation sources  40  above one or more working areas  20 . 
     In order to compact each layer of powder deposited on a working area  20  by the deposition device  30 , the additive manufacturing machine comprises a compaction device  50 . This compaction device  50  adopts the form of a scraper or of a roller  52 , for example mounted on a carriage  54 . This carriage  54  is mounted with the ability to move in translation in a longitudinal direction DL above the work surface  19  and above at least one working area  20 . The longitudinal direction DL is parallel to the work surface  18 . The longitudinal direction DL is perpendicular to the direction of superposition DS of the layers of powder in the working area  20 . The direction of superposition DS of the layers is the axis along which the layers are superposed on one another. This direction of superposition DS is perpendicular to the plane of each layer of powder. Because the plane of each layer of powder and the work surface  18  are, for example, horizontal planes, the axis of superposition AS is, for example, vertical. As illustrated in  FIG. 3 , the carriage  54  is, for example, mounted on rails  56  via rollers or glides. In order to be translationally driven in the longitudinal direction DL, the carriage  54  comprises, for example, an on-board drive system. Alternatively, the carriage  54  of the compaction device  50  may be moved by a motor mounted fixedly in the machine  10  and connected to the carriage via a movement transmission system such as a belt and pulleys. 
     Because it is possible for the powder to be deposited in excess on a working area  20 , a powder collecting tray  60  may be provided in the work surface  18  to collect the excess powder deposited on the working area and pushed across by the compaction device  50  as it passes over a working area. 
     As  FIG. 3  shows, the machine according to the invention may comprise several working areas  20  and/or the device  30  for depositing a layer of powder may comprise several reservoirs  32  which are able to be positioned above a working area, each reservoir being equipped with a sieve and with a vibrating device. By having several reservoirs, the deposition device allows the manufacture of one or more parts with different additive manufacturing powders, and therefore for example with different materials being combined into the one same part. By having several working areas and several reservoirs, the machine according to the invention for example allows parts to be manufactured with different additive manufacturing powders, and therefore different materials, simultaneously. With such a configuration, several collecting trays  60  may also be provided, so as to avoid mixing the excess powders collected. 
     As illustrated in  FIG. 3 , a build sleeve  22  may be cylindrical. In that case, the working area  20  is circular. However, a working area may also offer a working surface that is annular, polygonal, ellipsoidal, or any other shape suited to the geometry of the parts to be manufactured. 
     A reservoir  32  may contain enough powder for an entire additive manufacturing cycle. However, the deposition device  30  may also comprise at least one powder input  36  allowing powder to be delivered above the work surface  18  so as to supply a reservoir  32  with powder before or during an additive manufacturing cycle. 
     In instances in which the machine comprises several working areas and/or several reservoirs, several powder inputs  36  may be provided, delivering different additive manufacturing powders. 
     A powder input  36  takes the form of a chute or of a tube connected to a main powder reservoir  38 . A powder input  36  is, for example, mounted fixedly above the work surface  18 . In a variant, a powder input  36  may also be mounted with the ability to move above the work surface  18 . The free end  39  of the powder input  36  forms a powder supply point A 1  above the work surface  18 . Advantageously, a powder input  36  is inclined with respect to a horizontal plane so that the powder flows under the effect of gravity in the powder input  36 . To complement this, a powder input  36  may be equipped with a device  37  for controlling the flow rate of powder delivered by the supply point A 1 . This flow control device  37  may be a vibrating device and/or a device involving a valve. 
     In order to be able to fill a reservoir  32  with a powder input  36 , a reservoir  32  comprises a filling opening  62 . This filling opening is, for example, provided in the upper part of a reservoir  32 , as shown by  FIGS. 4 to 6 . This filling opening  62  allows the free end  39  of a powder input  36  forming a powder supply point A 1  to be introduced into a reservoir  32 . 
     According to the invention, a reservoir  32  is able to be positioned over a working area  20 . 
     In a first variant illustrated in  FIGS. 1 to 3 , a working area is fixed in the machine and a reservoir  32  is mounted with the ability to move between a position in which it is situated above a working area  20 , which position is illustrated in  FIG. 1 , and a position in which it is not situated above this working area, which position is illustrated in  FIGS. 2 and 3 . For example, a powder reservoir  32  is mounted with the ability to move in translation in the longitudinal direction DL above a working area  20 . To complement this, a reservoir  32  may also be mounted with the ability to move in a transverse direction DT parallel to the work surface  18  and perpendicular to the longitudinal direction DL. The transverse direction DT is perpendicular to the direction of superposition DS of the layers of powder in the working area  20 . 
     In order to be capable of translational movement in the longitudinal direction DL above a working area  20 , a reservoir  32  is, for example, mounted on a carriage  64  guided by the rails  56  and driven by an electric motor carried on board or sited at a distance outside the manufacturing chamber. 
     For the sake of its mobility in a transverse direction DT parallel to the work surface  18  and perpendicular to the longitudinal direction DL, a reservoir  32  is, for example, mounted on a traveller  66  guided and driven in its translational movement in the transverse direction DT on the carriage  64 , for example via a rail and a belt driven by an electric motor. The mobility of a reservoir  32  in the transverse direction DT facilitates for example the supplying of the reservoir with powder from the free end  39  of a powder input  36 , and also allows a layer of powder to be deposited on the working area as several successive and juxtaposed deposits from different complementary positions adopted by the reservoir above a working area. 
     In another variant which has not been illustrated, a reservoir  32  may be mounted fixedly in the machine. In that case, a working area  20  is mounted with the ability to move so that a reservoir  32  can be positioned over this working area  20 . 
     According to the invention, the device  30  for depositing a layer of powder comprises a vibrating device  68  able to subject a reservoir  32  to vibrations, and the powder distribution opening  34  of a reservoir is equipped with a sieve  70 , visible in  FIGS. 4, 7 and 9 . 
     The sieve  70  is produced in such a way as to hold the grains of powder in the reservoir  32  as long as no vibration is transmitted to the reservoir by the vibrating device  68 . In order to achieve this, the sieve  70  is produced in such a way that, in the absence of vibrations coming from the vibrating device  68 , the grains of powder form arches inside the reservoir  32 . 
     The vibrating device  68  takes the form of a vibrator, for example a pneumatic vibrator. For example, a vibrating device is mounted on a reservoir  32 . More specifically, because the powder distribution opening  34  is situated in the bottom part of a reservoir, the vibrating device  68  may be mounted on the upper part of a reservoir  32 , as illustrated in  FIGS. 4 to 6 . 
     With a reservoir in the form of a hollow body  72 , for example cylindrical and closed by an arched upper wall  74 , the vibrating device is mounted on the upper wall of this hollow body  72 . 
     As a variant, and as illustrated in  FIG. 8 , the vibrating device  68  may be juxtaposed with the reservoir  32  and for example fixed to a support  69  solidly attached to the reservoir  32 . 
     For example, the vibrating device  68  transmits vibrations at between 50 Hz and 200 Hz to a reservoir  32 , and more specifically to the body  72  of a reservoir, when this vibrating device  68  takes the form of a pneumatic vibrator. 
     To complement a pneumatic vibrator, the vibrating device  68  may also comprise a piezoelectric vibrator able to transmit vibrations at between 1 kHz and 35 kHz to a reservoir  32 , and more specifically to the body  72  of a reservoir. 
     Because additive manufacturing powders, for example metal powders, have a particle size of between a few microns and 150 microns, the mesh size of a sieve  70  is comprised between 30 and 300 microns. The mesh size of the sieve is adapted according to the particle size and fluidity of the powder to be distributed, so as to encourage the grains of powder to form arches inside a reservoir when no vibration is applied to this reservoir. 
     Because the machine according to the invention is intended for example for the manufacture of small-sized parts in alloys of expensive materials such as palladium, platinum, gold or silver or alloys of tungsten, molybdenum or tantalum which are specific to certain applications (for example horology), a working area  20  is, for example, circular, with a diameter of between 2 and 5 centimetres, and a sieve is, for example, circular, with a surface area of between 3 and 20 cm 2 . 
     To give an idea of scale, a reservoir  32  may contain between 15 and 200 cm 3  of additive manufacturing powder, namely approximately the maximum amount of powder that can be contained above the platform  24  in the build sleeve  22 . 
     To simplify the depositing of a layer of powder on the working area and avoid depositing powder by spreading and in excess, the shape and the surface area of the sieve  70  of a reservoir  32  may be substantially identical to the shape and surface area of the working area  20  and therefore to the shape and surface area of the build platform  24 . If the shape and surface area of the sieve  70  of a reservoir  32  are substantially identical to the shape and surface area of the working area  20 , a layer of powder may be deposited on the working area simply by positioning the reservoir above the working area and then applying vibrations to the reservoir while this reservoir is situated above the working area. 
     In instances in which the surface area of a working area is greater than that of the sieve  70  of a reservoir  32 , a layer of powder may be deposited on the working area by several successive and juxtaposed deposits, in the manner of a mosaic. These successive and juxtaposed deposits are made from different complementary positions adopted by the reservoir above a working area, vibrations being applied to the reservoir when it is situated in each of these complementary positions. 
     In addition to the deposit or deposits of powder made directly onto a working area by a reservoir  32 , compaction of the deposited powder by a compaction device  50  may advantageously be provided. 
     Of course, a reservoir  32  with a sieve  70  may also be used to deposit powder, for example in the form of a line, next to a working area and in front of a powder spreading device such as a scraper. 
     In instances in which the body  72  of the reservoir  32  is cylindrical, the sieve  70  takes the form of a disc. 
     A sieve  70  takes, for example, the form of a screen cut to the desired shape from a metallic fabric woven from metal, for example stainless steel, wires. 
     In a variant, a sieve  70  may take the form of a three-dimensional trellis structure, of the lattice type, for example made using additive manufacturing. A three-dimensional trellis structure for the sieve makes it possible to use a larger mesh size in order to avoid risks of blockage, while at the same time making it possible to increase the area that slows the grains of powder, providing better retention of the grains of powder in the reservoir  32  as long as no vibration is transmitted to the reservoir by the vibrating device  68 . 
     As illustrated in  FIG. 4  and in a first variant, with the vibrating device  68  mounted on a reservoir  32 , this reservoir is mounted on a leaf spring  76 . This leaf spring  76  connects the reservoir  32  to its support, such as a carriage  64 , a traveller  66  or a weighing sensor  78  visible in  FIG. 4 . A leaf spring  76  amplifies the amplitude of the vibrations of the reservoir when the vibrating device is active. 
     In a second variant illustrated in  FIGS. 8 and 9 , the vibrating device  68  and the reservoir  32  are mounted on a first support  69  mounted with the ability to slide with respect to a weighing sensor  78 . As a preference, the first support  69  is mounted with the ability to slide with respect to the weighing sensor  78  in the direction of superposition DS of the layers of powder. Thus, the reservoir oscillates mainly in a direction perpendicular to the plane of the sieve  70 , namely preferably in a vertical direction. For example, a spindle  88  is attached to the weighing sensor  78  using a second support  90 , and the first support  69  is mounted with the ability to slide along this spindle  88 . In order to control the oscillations of the reservoir  32  and return the reservoir to a stable rest position after the application of vibrations, springs  92  are interposed between the first support  69  and the second support  88 . For example, the springs  92  are mounted on the spindle  88 . 
     In order to know the exact amount of powder deposited by a reservoir  32 , and as illustrated by  FIGS. 4, 8 and 9 , a reservoir  32  is mounted on a weighing sensor  78 . A weighing sensor  78  is able to measure the mass of the reservoir and of the powder it contains. When powder is delivered by the reservoir  32 , the weighing sensor  78  is able to measure the reduction in the mass of powder present in the reservoir, and therefore the amount of powder delivered. Advantageously, a weighing sensor  78  is able to detect a break in the flow of powder or an abnormal reduction in the amount of powder deposited, for example as a result of a plug of powder forming in the reservoir or of clumps of powder which may accumulate in a reservoir  32  as the manufacturing cycles progress. A weighing sensor  78  also allows control over the filling of a reservoir  32  via a powder input  36 . 
     For example, the operation of the flow control device  37  of a powder input  36  is managed using the measurements taken by a weighing sensor  78 . For this purpose, the machine comprises a control unit (not illustrated) connected to the weighing sensor  78  and to the flow control device  37 . 
     A weighing sensor  78  is, for example, an extensometer gauge weighing sensor. A weighing sensor  78  for example takes the form of an arm mounted so that it can bend and fitted with an extensometer gauge. 
     By making it possible to know precisely the amount of powder deposited, the mounting of the reservoir  32  on a weighing sensor allows powder consumption to be optimized, this being something that is, for example, absolutely essential when the powder contains one or more precious metals. 
     In instances in which the device  30  for depositing a layer of powder comprises several reservoirs  32  containing different additive manufacturing powders, mounting each reservoir on a weighing sensor allows control over the ratio between the amounts of different powders deposited. 
     In instances in which a reservoir  32  is mounted on a carriage  64  via a traveller  66 , the weighing sensor  78  connects the reservoir  32  to the traveller  66 , it being possible for a leaf spring  76  to be interposed between the reservoir  32  and the weighing sensor  78 . 
     For the purposes of mounting a sieve  70  on a reservoir  32 , a mounting ring  80  is for example provided. 
     In a first variant illustrated in cross section in  FIG. 5 , with the distribution opening  34  of a reservoir  32  already being equipped with a nozzle  82 , an extension  84  is mounted on the body  72  of the reservoir  32  and the sieve mounting ring  80  is mounted on this extension. More specifically, the extension  84  is mounted at the bottom part of the reservoir, below the nozzle  82  already present, and the sieve mounting ring  80  is mounted at the bottom part of the extension  84 . In this first variant, the arches of powder that form above the sieve are situated in the extension  84 . In instances in which the body  72  of a reservoir  32  is cylindrical, the extension  84  also adopts the form of a cylindrical body, and the mounting ring  80  is likewise cylindrical. For example, the extension  84  is screwed onto the body  72  of a reservoir  32 . Thus, the reservoir  32  can be used with a sieve  70  or with a nozzle  82  by removing the sieve. For example, the mounting ring  80  is screwed onto the extension  84 . Thus, the mounting ring  80  can easily be removed to change the sieve  70  and adapt the mesh size of the sieve to a new powder with a different particle size and/or a different fluidity. 
     In another variant illustrated in  FIGS. 6 to 9 , the distribution opening  34  of a reservoir  32  is not equipped with a nozzle  82  and the sieve mounting ring  80  is mounted directly on the body  72  of the reservoir  32 . More specifically, the mounting ring  80  is mounted at the lower part of the reservoir. In this first second, the arches of powder that form above the sieve are situated in the body  72  of a reservoir  32 . In instances in which the body  72  of a reservoir  32  is cylindrical, the mounting ring  80  is likewise cylindrical. For example, the mounting ring  80  is screwed onto the body  72 . Thus, the mounting ring  80  can easily be removed to change the sieve  70  and adapt the mesh size of the sieve to a new powder with a different particle size and/or a different fluidity. 
     In either one of the variants for the mounting of a sieve, and as shown in detail in  FIG. 7 , a ring  80  is a hollow body comprising a shoulder  86  in the bottom part. The open cross section of the shoulder is smaller than that of the sieve  70  in order to hold the sieve against the extension  84  or the body  72  of the reservoir when the ring is mounted on this extension  84  or this body  72 . 
     In order to increase the amount of powder deposited around the exterior edge of the sieve, the cross section of the shoulder  86  holding the sieve decreases progressively in the direction away from the sieve. 
     In order to avoid any undesired distribution of powder, the powder distribution opening  34  of a reservoir  32  may be equipped with a shut-off element (not depicted) such as a valve, a flap, an orifice plate or a diaphragm for example. This shut-off element may be mounted below a sieve  70  or above the sieve and inside the reservoir. 
     The present invention also covers a powder bed fusion additive manufacturing method that can be implemented using the machine that has just been described. This method comprises a step of depositing a layer of powder on a working area  20  performed by subjecting a certain amount of powder to sieving and vibrations, for example using a reservoir  32  equipped with a sieve  70  and with a vibrating device  68 , and a step of selective consolidation of the deposited layer of powder. 
     According to this method and in a first variant, a layer of powder is deposited on the working area by positioning the reservoir  32  above the working area  20  and then by applying vibrations to the reservoir while this reservoir is situated above the working area. In that case, the shape and surface area of the sieve are preferably identical to the shape and surface area of the working area. 
     In a second variant of the method according to the invention, a layer of powder is deposited on the working area by performing several successive and juxtaposed deposits from different complementary positions adopted by the reservoir  32  above a working area  20 , vibrations being applied to the reservoir when it is situated in each of these complementary positions. 
     In a third variant of the method according to the invention, a layer of powder is deposited on the working area by using the reservoir  32  and its sieve  70  to deposit powder in the form of a line next to the working area of the machine and in front of a powder spreading device. 
     In instances in which a line of powder is deposited using the reservoir  32  and its sieve  70 , mounting the reservoir on a weighing sensor allows the movement of the reservoir  32  and the operation of the vibrating device  68  to be slaved to the amount of powder deposited and allows the amount of powder deposited to be adapted, for example, to suit the shape of the working area, a partial deposit at the end of manufacture, or a fractionated deposit or, for example, to increase the amount of powder deposited at the ends of the line of powder. 
     Optionally, this powder bed fusion additive manufacturing method may also have provision for the layer of powder deposited by sieving and vibrations to be compacted before it is selectively consolidated, for example using a compaction device  50 .