Patent Publication Number: US-2022212399-A1

Title: Additive manufacturing machine comprising a movable surface for receiving powder optimized to retain the grains of powder

Description:
The invention falls within the field of powder-based additive manufacturing by melting grains of this powder with the assistance of one or more energy or heat source(s), such as a laser beam and/or an electron beam and/or diodes. 
     More specifically, the invention falls within the field of additive manufacturing by powder bed deposition and it relates to layering the additive manufacturing powder inside a machine for additive manufacturing by powder bed deposition. 
     Even more specifically, the aim of the invention is to reduce the amount of powder used to produce each layer of powder and to improve the quality of the powder bed. 
     Application WO 2017/108868 describes a machine for additive manufacturing by powder bed deposition comprising a work top and at least one work area where layers of powder are spread and selectively successively consolidated one after another. 
     The machine described in application WO 2017/108868 comprises a device for depositing a layer of powder onto the work area and a heat or energy source used to selectively consolidate a layer of powder deposited onto the work area. The deposition device comprises a slide for receiving powder moving in the vicinity of the work area, a device for dispensing a bead of powder onto the slide and a device for spreading the bead of powder from the slide towards the work area. 
     In order to guarantee the quality of the manufactured parts, the powder must uniformly cover the entire work area or at least the parts of the work area in which parts are manufactured. To this end, excessive powder is deposited onto the slide and the excess powder that is not used to produce the layer of powder is pushed by the spreading device to a powder recovery tank. 
     Even if the excess powder recovered in the tank can be recycled, it is preferable that the amount of powder excessively deposited onto the slide and that must be recycled is limited. Indeed, it is always preferable to limit the powder consumption of the machine and to limit the amount of powder to be recycled since this recycling can be expensive. 
     Controlling the flow of the device for dispensing powder and controlling the movements of the slide allows the amount of powder forming the bead of powder that will be spread by the spreading device over the work area to be dosed in the best possible manner. 
     However, during any movements of the slide, the powder deposited onto the slide can be subject to vibrations and jarring, causing a certain amount of the grains of powder deposited onto the slide to fall off. Furthermore, the amount of excessive powder deposited onto the slide is generally increased in order to compensate for a certain amount of powder falling off during the movements of the slide. 
     In the case of additive manufacturing powders with high castability, the amount of excessive powder deposited onto the slide needs to be significantly increased in order to compensate for a greater amount of grains of powder falling off. 
     The aim of the present invention is to improve the retention of the grains of powder on a movable powder reception surface in an additive manufacturing machine, in particular for limiting and/or preventing a certain amount of grains of powder from falling off under the effect of vibrations or jarring experienced by the movable reception surface during the movements thereof. 
     To this end, the aim of the invention is a machine for additive manufacturing by powder bed deposition, this machine comprising a work top, a work area, a device for depositing a layer of powder onto the work area and a heat or energy source used to selectively consolidate a layer of powder deposited onto the work area, the device for depositing a layer of powder comprising a movable element for receiving powder moving relative to the work top and in the vicinity of the work area, a device for dispensing a bead of powder onto the movable element and a device for spreading the bead of powder from the movable element towards the work area. 
     According to the invention, the movable element assumes the form of a slide mounted to translationally move in a transverse horizontal direction relative to the work area and moving between a retracted position, in which this slide is located outside the trajectory of the powder spreading device, and a deployed position, in which this slide at least partly extends into the trajectory of the powder spreading device or the movable element externally surrounding the work area over its entire circumference and rotationally moving around the work area, at least part of the upper surface of a movable element is located above the upper surface of the work top and/or at least part of the upper surface of a movable element is located below the upper surface of the work top. 
     The one or more part(s) of the upper surface of the movable element that is/are located above and/or below the upper surface of the work top allow the roughness and/or the relative contact surface between the grains of powder deposited onto the movable element and the upper surface of the movable element to be increased. The increase in the roughness and/or the relative contact surface allows the grains of powder to be retained on the upper surface of the movable element, in particular during movements of this movable element. 
     The invention also makes provision for the following:
         the entire upper surface of a movable element is located below the upper surface of the work top;   the upper surface of a movable element is located between 60 micrometres and 5 millimetres, or between 100 micrometres and 1 millimetre, below the upper surface of the work top;   at least part of the upper surface of a movable element is located in the extension of the upper surface of the work top, this movable element also comprises at least one raised form rising above its upper surface and/or at least one recessed form extending below its upper surface;   a raised form is printed onto the upper surface of the movable element;   a recessed form is machined in the upper surface of the movable element;   a raised form or a recessed form is made up of a plurality of elementary patterns;   a single recessed form is provided in the upper surface of the movable element;   the single recessed form machined in the upper surface of the movable element assumes the form of a rectangular section recess in a vertical plane and assumes a height in a vertical direction ranging between 60 micrometres and 5 millimetres, or between 150 micrometres and 2 millimetres;   the single recessed form extends over a width at least equal to 80% of the width of the upper surface of the movable element;   the single recessed form extends lengthwise over a distance that is greater than the largest transverse dimension of the work area;   the movable element moves in the vicinity of the work area in a receptacle provided in the work top;   with the device for dispensing a bead of powder being fixed, a movable element moves under the dispensing 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 front view of a first variant of an additive manufacturing machine that can be improved with the invention; 
         FIG. 2  is a schematic top view of a first variant of an additive manufacturing machine that can be improved with the invention; 
         FIG. 3  is a schematic side view of a first variant of an additive manufacturing machine that can be improved with the invention; 
         FIG. 4  is a schematic top view of a second variant of an additive manufacturing machine that can be improved with the invention; 
         FIG. 5  is a schematic transverse section view of a first embodiment of the invention; 
         FIGS. 6, 7 and 8  are schematic transverse section views of various variants of an alternative embodiment of the invention; 
         FIGS. 9, 10 and 11  illustrate various patterns that can be used in the alternative embodiment of the invention of  FIGS. 6, 7 and 8 ; 
         FIG. 12  is a schematic transverse section view of another embodiment of the invention; 
         FIG. 13  is a schematic top view of the embodiment of the invention of  FIG. 12 ; 
         FIGS. 14 and 15  illustrate the operating principle of the invention in the embodiment of  FIGS. 12 and 13 . 
     
    
    
     The invention relates to a machine for additive manufacturing by powder bed deposition. Additive manufacturing by powder bed deposition is an additive manufacturing method in which one or more part(s) is/are manufactured by the selective melting of various mutually superposed layers of additive manufacturing powder. The first layer of powder is deposited onto a support such as a platform, then selectively sintered or melted using one or more source(s) of energy or of heat along a first horizontal section of the one or more part(s) to be manufactured. Then, a second layer of powder is deposited onto the first layer of powder that has just been melted or sintered, and this second layer of powder is in turn selectively sintered or melted, and so on, until the last layer of powder is reached that is useful for manufacturing the last horizontal section of the part or part(s) to be manufactured. 
     As illustrated in  FIG. 1 , and in order to allow additive manufacturing of parts by powder bed deposition, the additive manufacturing machine  10  according to the invention comprises, for example, a manufacturing chamber  12  and at least one heat or energy source  14  used to selectively, via one or more beams  16 , melt a layer of additive manufacturing powder deposited inside the manufacturing chamber  12 . 
     The one or more heat or energy source(s)  14  can assume the form of sources capable of producing one or more electron beam(s) and/or one or more laser beam(s). These sources are, for example, one or more electron gun(s) and/or one or more laser source(s). The one or more source(s)  14  is/are, for example, fixed relative to the manufacturing chamber  12 . In order to allow selective melting, and therefore allow the one or more beam(s)  16  of energy or of heat to move, each source  14  comprises means for moving and controlling the one or more beam(s)  16 . Alternatively, the one or more heat or energy source(s)  14  can be movably mounted inside the manufacturing chamber  12 , for example, when these sources are laser beam emitting diodes. 
     The manufacturing chamber  12  is a closed chamber. A wall of this manufacturing chamber  12  can comprise a glass pane for observing the manufacturing progress inside the chamber. At least one wall of this manufacturing chamber  12  comprises an opening granting access to the inside of the chamber for maintenance or cleaning operations, with this opening being able to be sealed closed again by a door during a manufacturing cycle. During a manufacturing cycle, the manufacturing chamber  12  can be filled with an inert gas, such as nitrogen, in order to prevent the additive manufacturing powder from oxidizing and/or in order to avoid risks of fire or of explosion. The manufacturing chamber  12  can be maintained at a slight overpressure in order to avoid the ingress of oxygen, or can be maintained under vacuum when an electron beam is used inside the chamber to sinter or melt the powder. 
     Inside the manufacturing chamber  12 , the additive manufacturing machine  10  according to the invention comprises, for example, a work area  20  and a device  29  for depositing a layer of powder onto the work area  20 . With the machine comprising a horizontal work top  18  with an upper surface S 18 , the work area  20  is located, for example, in the work top  18 . As illustrated in  FIG. 2 , a work area  20  is defined, for example, by an opening  21  provided in the horizontal work top  18  and by a manufacturing sleeve  22  and a manufacturing platform  24 . The sleeve  22  extends vertically under the work top  18  and it opens into the work top  18  via the opening  21 . The manufacturing platform  24  slides vertically inside the manufacturing sleeve  22  under the effect of an actuator  26  such as a ram. 
     In order to produce the various layers of powder used for the additive manufacturing of the one or more part(s) to be manufactured, the deposition device  29  comprises, for example, a movable element  28  for receiving powder moving relative to the work top and in the vicinity of the work area  20 , a device  32  for dispensing a bead of powder onto the movable element and a device  30  for spreading the bead of powder from the movable element towards the work area. 
     A device  32  for dispensing a bead of powder is fixedly mounted, for example, relative to the manufacturing chamber  12  and to the work top  18 . 
     The spreading device  30  assumes the form of a scraper and/or of one or more roller(s)  34  mounted on a carriage  35 . This carriage  35  is mounted to translationally move in a longitudinal horizontal direction D 35  above the work area  20 . In order to be set into longitudinal, horizontal translation movement, the carriage  35  can be motorized, or set in motion by a motor (not shown) located outside the manufacturing chamber  12  and connected to the carriage via a movement-transmission system such as pulleys and a belt. 
     In a first variant illustrated in  FIGS. 1, 2 and 3 , the additive manufacturing machine according to the invention can comprise two movable elements  28  for receiving powder and two devices  32  for dispensing a bead of powder, with each movable element receiving powder dispensed by at least one dispensing device. In greater detail, a movable element and a dispensing device are provided on each side of the work area  20  in the longitudinal horizontal direction D 35  of movement of the carriage  35  of the spreading device  30 . Thus, the powder spreading device does not make any needless journey over the work area, since it can spread powder in both directions of its longitudinal horizontal direction D 35  of movement. 
     As shown in  FIG. 2 , a movable element  28  translationally moves in the vicinity of the work area. To this end, a movable element  28  assumes the form of a slide  36 , for example. A slide  36  is mounted to translationally move in a transverse horizontal direction D 36  in relation to the work area  20 . A slide  36  moves between a retracted position, in which this slide is located outside the trajectory of the powder spreading device  30 , and a deployed position, in which this slide at least partly extends into the trajectory of the powder spreading device  30 . For example, the transverse horizontal direction D 36  in which a slide  36  moves is perpendicular to the longitudinal horizontal direction D 35  of movement of the carriage  35  of the spreading device  30 . The slide  36  is translationally driven, for example, by an actuator, such as a ram (not shown). 
     A dispensing device  32  is provided above each slide  36 , and therefore above each movable element  28 . Each slide  36 , and therefore each movable element  28 , is of elongated shape in the transverse horizontal direction D 36 . Each slide  36 , and therefore each movable element  28 , moves under the powder dispensing device when the slide transitions from its retracted position to its deployed position. 
     As shown in  FIGS. 2 and 3 , each slide  36  is mounted to translationally move in a receptacle  38  provided in the work top  18  of the manufacturing chamber  12 . Each slide  36  translationally moves in a horizontal plane. In its retracted position, the slide  36  is located, for example, in a sheath  39  sealably connected to the manufacturing chamber  12  and mounted opposite the receptacle  38 , such as a groove, provided in the work top. When it is in the deployed position, a slide  36  is located in the receptacle  38 . A receptacle  38  and the sheath  39  extend in the transverse horizontal direction D 36  in which a slide  36  moves. Each receptacle  38  extends in the vicinity of a work area  20 . Advantageously, a sheath  39  is equipped with a hopper  41  for recovering the grains of powder falling from the slide. 
     By being mounted to translationally move in the vicinity of a work area  20  and in the work top  18 , each slide  36  occupies a very small amount of space in the vicinity of the work area  20 . 
     With each movable element  28  assuming the form of a translationally movable slide, a work area  20  preferably assumes a rectangular form, for example. However, a work area  20  can also assume other forms better suited to the forms of the one or more part(s) to be manufactured, such as a circular, oval or annular form, for example. 
     In order to produce a layer of powder on the work area  20 , a dispensing device  32  delivers powder in the form of a bead onto the upper surface S 28  of a movable element  28 , then the scraper and/or the one or more roller(s) of the powder spreading device spread the powder deposited in the form of a bead over the work area  20 . In order to produce a bead of powder on the upper surface S 28  of a movable element  28 , this movable element  28  translationally moves under a powder dispensing device  32 . 
     As illustrated in  FIG. 2 , a powder dispensing device  32  comprises a buffer tank  40  connected to a powder supply  42 , and a powder dispensing point P 1 , below which a movable element  28  moves. The powder supply  42  assumes, for example, the form of a valve  43 , to which a container  45  is detachably connected. The container  45  contains the powder intended to feed the buffer tank  40  of a dispensing device  32  during a manufacturing cycle. The valve  43  allows the passage of powder towards a powder dispensing device  32  to be permitted or prevented. Alternatively, the powder supply  42  can also assume the form of an automated powder supply circuit allowing, for example, powder to be supplied to a plurality of additive manufacturing machines. 
     As illustrated in  FIG. 2 , the buffer tank  40  of a powder dispensing device  32  is connected to a powder supply  42 , and notably to the valve  43 , by a pipe  46 . In the event that the machine  10  comprises two powder dispensing devices  32  provided on either side of the same work area, these two powder dispensing devices  32  are connected, for example, to the same powder supply  42 , and therefore to the same valve  43 . 
     A powder dispensing device  32  allows a stable and controlled flow of powder to be delivered to a dispensing point P 1 , under which a movable element  28  moves. In greater detail, the outlet  58  of the dispensing device  32  corresponds to the powder dispensing point P 1 . As illustrated in  FIG. 3 , a powder dispensing device  32  is mounted, for example, above the sheath  39 . 
     In a second variant of the machine according to the invention illustrated in  FIG. 4 , the device  129  for depositing a layer of powder comprises a movable element  128  for receiving powder surrounding the work area  120 , a device  132  for dispensing a bead of powder onto the movable element  128  and a device  30  for spreading powder deposited onto the movable element  128 . 
     In this second variant, the work area  120  is circular. The opening  121  provided in the work top  18  and defining this work area is also circular. 
     For example, the movable element  128  externally surrounds the work area  120  over its entire circumference. The movable element  128  assumes the form of a ring and the upper surface S 128  of the movable element is annular. The movable element  128  moves in the vicinity of the work area  120  in a receptacle  138  provided in the work top  18 . This receptacle  138  assumes, for example, the form of an annular recess produced in the work top  18  around the work area  120 . 
     In greater detail, the movable element  128  rotates around the work area  120 . The movable element is set into rotation around the work area  120  by at least one actuator, such as a motor (not shown). The movable element is set into rotation around a vertical axis. By being mounted to freely rotate around the work area  120  and by having an annular form, the movable element  28  occupies a very small amount of space around the work area  120 . 
     In this second variant, the device  32  for dispensing a bead of powder onto the upper surface S 128  of the movable element  128  comprises a buffer tank  48  connected to a powder supply  50  and a dispensing pipe  52  connecting the buffer tank  48  to a powder dispensing point P 1  located above the movable element  128 . The dispensing pipe  52  is mounted, for example, on a vibrating device (not shown), so as to generate a continuous flow of powder in the dispensing pipe and the buffer tank  48  towards the powder dispensing point P 1 . The buffer tank  48  can be rigidly fixed to the dispensing pipe  52 . The buffer tank  48  is fixed to an upstream end of the dispensing pipe  52 , and the powder dispensing point P 1  is located at the other downstream end of the dispensing pipe. The buffer tank  48  is connected, for example, to the powder supply by a flexible pipe  56 . The powder supply  50  can be connected to an automated powder supply circuit or can assume the form of a detachable container. 
     In this second variant, the spreading device  30  also assumes the form of a scraper and/or of one or more roller(s) mounted on a carriage  35 . This carriage  35  is mounted to translationally move in a longitudinal horizontal direction D 35  above the work area  120 . In order to be guided for longitudinal horizontal movement, the carriage  35  can be mounted on rails  58 . 
     In any of the previously described variants, the upper surface S 28 , S 128  of a movable element  28 ,  128  moves under a powder dispensing device  32 ,  132  and in the vicinity of a work area  20 ,  120 . During these movements, the movable element  28 ,  128  can experience vibrations and jarring that is likely to cause a certain amount of powder to fall off the slide. 
     In order to prevent, or at least limit, the amount of powder falling from the upper surface S 28 , S 128  of a movable element  28 ,  128  during a movement of this movable element  28 ,  128 , at least part of the upper surface S 28 , S 128  of the movable element is located above the upper surface of the work top and/or at least part of the upper surface S 28 , S 128  of the movable element is located below the upper surface of the work top. 
     In other words, one or more part(s) of the upper surface S 28 , S 128  of the movable element is/are located above the upper surface S 18  of the work top, one or more part(s) of the upper surface S 28 , S 128  of the movable element is/are located below the upper surface S 18  of the work top, or one or more of the first part(s) of the upper surface S 28 , S 128  of the movable element is/are located above the upper surface S 18  of the work top and one or more of the second part(s) of the upper surface S 28 , S 128  of the movable element is/are located below the upper surface S 18  of the work top. 
     By increasing the roughness of the upper surface S 28 , S 128  of the movable element and/or by increasing the relative contact surface between the grains of powder and the upper surface of the movable element, the one or more part(s) of the upper surface of the movable element that are located above and/or below the upper surface of the work top allow the grains of powder to be better retained on the upper surface of the movable element, in particular during movements of this movable element. 
     In a first embodiment of the invention illustrated in  FIG. 5 , the entire upper surface S 28 , S 128  of a movable element  28 ,  128  can be located below the upper surface S 18  of the work top  18 . In this scenario, a residual amount Q of grains of powder is not carried by the powder spreading device  30  towards the work area  20 ,  120 . This residual amount Q of grains of powder allows the relative contact surface to be increased with the new grains of powder that will be deposited onto the upper surface S 28 , S 128  of a movable element  28 ,  128  by a dispensing device  32 ,  132 . For example, the upper surface S 28 , S 128  of the movable element  28 ,  128  is located between 60 micrometres and 5 millimetres, or between 100 micrometres and 1 millimetre, below the upper surface S 18  of the work top  18 . 
     As an alternative to this first embodiment, at least part of the upper surface S 28 , S 128  of a movable element is located in the extension of the upper surface of the work top, and the movable element also comprises at least one raised form  60  rising above its upper surface and/or at least one recessed form  62  extending below its upper surface. 
     As illustrated in  FIG. 6 , a movable element can comprise raised forms  60  rising above its upper surface and recessed forms  62  extending below its upper surface. 
     As illustrated in  FIG. 7 , a movable element can only comprise raised forms  60  rising above its upper surface. 
     As illustrated in  FIG. 8 , a movable element can comprise only recessed forms  62  extending below its upper surface. 
     The raised forms  60  and the recessed forms  62  can be obtained by laser machining, for example. The raised forms can be printed, for example, onto the upper surface of the movable element, for example, with an additive manufacturing method. The recessed forms  62  are machined, for example, i.e. obtained by removing material, in the upper surface of the movable element. 
     The raised forms  60  and/or the recessed forms  62  allow the relative contact surface to be increased with the new grains of powder that will be deposited onto the upper surface S 28 , S 128  of a movable element  28 ,  128  by a dispensing device  32 ,  132 . 
     In order to further increase the retention of the grains of powder on the upper surface of the movable element, a raised form  60  or a recessed form  62  is made up of a plurality of elementary patterns M. A pattern M can have an open or closed profile, and this profile can assume various forms: circular, triangular, polygonal, etc. 
     In a first example illustrated in  FIG. 9 , the elementary patterns M are joined together. 
     In another example illustrated in  FIG. 10 , the patterns M are intersecting. 
     In another example illustrated in  FIG. 11 , the patterns M are adjacent without intersection. 
     Optionally, one or more of the raised form(s) and/or one or more of the recessed form(s) can be provided on the upper surface S 28 , S 128  of a movable element  28 ,  128  that is located below the upper surface S 18  of the work top  18 . 
     In one embodiment illustrated in  FIGS. 12 to 15 , a single recessed form  64  is provided in the upper surface S 28 , S 128  of the movable element. 
     For example, the single recessed form  64  provided in the upper surface of the movable element assumes the form of a rectangular section recess in a vertical plane and assumes a height H 64  in a vertical direction ranging between 60 micrometres and 5 millimetres, or between 150 micrometres and 2 millimetres. 
     In order to maximize the increase in the relative contact surface with the new grains of powder deposited by a dispensing device, the single recessed form  64  extends over a width W 64  at least equal to 80% of the width W 28  of the upper surface of the movable element. 
     Particularly in the case where the movable element  28  assumes the form of a slide, and as illustrated in  FIG. 13 , the single recessed form  64  extends lengthwise over a distance that is greater than the largest transverse dimension of the work area. In the case where the work area is parallelepiped and where the movable element  28  also assumes a parallelepiped form, the single recessed form  64  extends over a length L 64  that is greater than the width W 20  of the work area. This thus ensures the quality of the powder bed deposited onto the longitudinal edges of the work area. 
       FIGS. 14 and 15  illustrate the implementation of the invention with the single recessed form  64  that has just been described. In a first step, illustrated in  FIG. 14 , a bead C of powder is deposited by a dispensing device  32 ,  132  onto the movable element  28 ,  128 . If no layer of powder has been produced beforehand, the recessed form  64  is also filled with powder by the dispensing device  32 ,  132  during this first step. In order to deposit the bead C of powder, the movable element  28 ,  128  moves, for example, below the dispensing device  32 ,  132 . 
     Once the bead C of powder is deposited and the movable element  28 ,  128  is positioned between the spreading device  30  and the work area  20 ,  120 , the spreading device is set into motion so as to spread the bead of powder towards the work area. 
     After the spreading device  30  passes above the movable element  28 ,  128 , a residual amount Q of grains of powder is still present in the recessed form  64 . This residual amount Q of grains of powder allows the relative contact surface to be increased with the new grains of powder that will be deposited onto the upper surface S 28 , S 128  of the movable element  28 ,  128  by a dispensing device  32 ,  132 .