Patent Publication Number: US-2023143131-A1

Title: Additive Manufacturing Method For Embedding Fibers In A Three-Dimensional Structure

Description:
PRIORITY CLAIM 
     This application is a divisional application of and claims priority to co-pending U.S. patent application Ser. No. 14/938,227, which is entitled “Additive Manufacturing System With Layers Of Reinforcing Mesh,” and which was filed on Nov. 11, 2015, and which issued as U.S. patent No. xx,xxx,xxx on mm/dd/yyyy. 
    
    
     TECHNICAL FIELD 
     The device disclosed in this document relates to printers that produce three-dimensional objects and, more particularly, to systems and methods for reinforcing such objects. 
     BACKGROUND 
     Digital three-dimensional manufacturing, also known as digital additive manufacturing, is a process of making a three-dimensional solid object of virtually any shape from a digital model. Three-dimensional printing is an additive process in which one or more printheads eject successive layers of material on a substrate in different shapes. The substrate is supported either on a platform that can be moved three dimensionally by operation of actuators operatively connected to the platform, or the printhead or printheads are operatively connected to one or more actuators for controlled movement of the printhead or printheads to produce the layers that form the object. Three-dimensional printing is distinguishable from traditional object-forming techniques, which mostly rely on the removal of material from a work piece by a subtractive process, such as cutting or drilling. 
     Current three-dimensional printers have significant limitations with regard to the viscosity range of the materials that can be ejected, with most materials having an upper limit between 10 and 20 centipoise (cP). The printers that eject liquid photopolymers that are cured are limited to the upper end of this range. Consequently, objects made with these materials may be too delicate and consequently limited in their functionality. Other additive manufacturing methods such as Fused Deposition Modeling (FDM) or Selective Laser Sintering (SLS) can use a wider range of materials and thus are capable of producing products that are more durable than the objects made from cured photopolymer materials. Therefore, a system capable of producing objects with cured photopolymer materials that are as durable as objects by the FDM and SLS methods would be advantageous. 
     SUMMARY 
     A manufacturing method that embeds fibers or one or more pieces of mesh in a three-dimensional structure during an additive manufacturing process of the structure increases the robustness and durability of the structure. The method includes operating with a controller at least one ejector in a plurality of ejectors to form at least one layer of a photopolymer material on a substrate, operating with the controller a source of ultraviolet (UV) radiation to cure the at least one layer of photopolymer partially, operating with the controller an actuator to position fibers onto a top surface of the at least one layer of partially cured photopolymer, and operating with the controller the at least one ejector to eject additional photopolymer material onto the fibers to form at least one other layer of photopolymer material on the fibers. 
     A system that embeds fibers or one or more pieces of mesh in a three-dimensional object during an additive manufacturing process of the structure increases the robustness and durability of the structure. The system includes a substrate, a plurality of ejectors configured to eject drops of photopolymer material towards the substrate, a source of ultraviolet (UV) radiation that emits radiation to cure the photopolymer material ejected from the plurality of ejectors, an actuator configured to position fibers on photopolymer material supported by the substrate, and a controller operatively connected to the plurality of ejectors, the source of radiation, and the actuator. The controller is configured to operate at least one ejector in the plurality of ejectors to form at least one layer of the photopolymer material on the substrate, operate the source of UV radiation to cure the at least one layer of photopolymer material partially, operate the actuator to position fibers on a top surface of the at least one layer of the partially cured photopolymer material, and operate the plurality of ejectors to eject additional photopolymer material onto the fibers to form at least one other layer of photopolymer material on the fibers. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing aspects and other features of a system that embeds fibers or one or more pieces of mesh in an additive manufactured three-dimensional object are explained in the following description, taken in connection with the accompanying drawings. 
         FIG.  1    illustrates a top-down view of a system for forming a three-dimensional structure using an additive manufacturing method that has the ability to custom cut mesh pieces during the building process. 
         FIG.  2    illustrates a side view of the system shown in  FIG.  1   . 
         FIG.  3    illustrates a top-down view of the system shown in  FIG.  1    comprising additional elements according to further embodiments of the invention. 
         FIG.  4    is a flow diagram of an additive manufacturing method for embedding a mesh piece or a plurality of mesh pieces in a three-dimensional structure. 
         FIG.  5    is an illustration of a fiber dispenser that can be used in the embodiment shown in  FIG.  3   . 
     
    
    
     DETAILED DESCRIPTION 
     For a general understanding of the environment for the system and method disclosed herein as well as the details for the system and method, reference is made to the drawings. In the drawings, like reference numerals designate like elements. 
       FIGS.  1  and  2    illustrate a system for forming a three-dimensional structure using an additive manufacturing method that has the ability to embed fibers or pieces of mesh in the structure during the building process. As used in this document, the term “fibers” refers a collection of filaments of one or more materials useful for imparting durability or tensile strength to the manufactured structure. As used in this document, “mesh” refers to a plurality of fibers that are organized to run in at least two different directions and which hold together to form an entity that is permeable to some degree of air and light. The printer  100  includes a substrate  10 , at least one ejector  12 , a cutting device  14 , an actuator  16 , a controller  18 , a raster image processor  22  that generates raster data and a printhead driver  24 . A three-dimensional part file  20 , such as that produced by a computer-aided design (CAD) system, is received by a three-dimensional raster image processor  22 , which generates raster image data for the layers to be printed to form the part  11 . The raster image processor  22  passes the raster image data to the printhead driver  24  and the driver generates the pixelated data for operating the at least one ejector  12  as well as sending the data to the controller  18 . The at least one ejector  12  is configured to eject drops of a photopolymer material towards the substrate  10 , such that the drops form a layer of photopolymer material on top of the substrate  10 . As shown in  FIG.  1   , multiple ejectors can be provided in succession and the part  11  is moved through the line of ejectors to receive drops of photopolymer material from each. The cutting device  14  is configured to cut a mesh material into virtually any shape. The actuator  16  is configured to move at least one piece of mesh material  13  from the cutting device  14  towards the substrate. The purpose of the at least one piece of mesh material  13  is to increase part robustness and strength by inserting at least one piece of mesh material  13  in between layers of the part. The mesh acts as a support structure within the part, and may be placed throughout the entire part or selectively placed at only high stress areas within the part. The mesh material may be made of any material that is strong enough to support the cured part. These materials include, but are not limited to, metals, such as nickel and stainless steel, and high strength plastics. 
     The controller  18  is operatively connected to the printhead driver  24 , the at least one ejector  12 , the cutting device  14  and the actuator  16 . The controller  18  is configured to operate the various components of the system. Controller  18  is configured, for example, as a self-contained, dedicated computer having a central processor unit (CPU) with electronic storage, and a display or user interface (UI). Controller  18  can also be configured with general or specialized programmable processors that execute programmed instructions stored in a memory operatively connected to the controller. The processors, their memories, and interface circuitry configure the controllers to perform the operations described below. These components can be provided on a printed circuit card or provided as a circuit in an application specific integrated circuit (ASIC). Each of the circuits can be implemented with a separate processor or multiple circuits can be implemented on the same processor. Alternatively, the circuits can be implemented with discrete components or circuits provided in very large scale integrated (VLSI) circuits. Also, the circuits described herein can be implemented with a combination of processors, ASICs, discrete components, or VLSI circuits. 
     First, the controller operates the at least one ejector  12  to eject drops of photopolymer material to form at least one layer of photopolymer material on the substrate  10 . The controller  18  may operate the at least one ejector  12  to add as many layers as required by the three-dimensional part file  20  or as desired by the user before the photopolymer material is cured. Once the photopolymer material is cured, at least one piece of mesh material  13  is positioned on the top layer of the photopolymer material. The controller  18  can also operate the cutting device  14  with reference to the processed data used to operate the at least one ejector  12  to cut the mesh material into one or more pieces of mesh  13  having a shape that corresponds to a portion of the at least top layer of cured photopolymer material. The resulting at least one piece of mesh material  13  is cut into a shape or shapes that correspond to the general cross-sectional shape of the top layer of the part  11  as shown in the embodiment of  FIG.  1   . Having a piece of mesh material  13  with a shape that is substantially similar to the shape of the top layer of the part maximizes the surface area of the top layer that the piece of mesh material  13  contacts. This maximization of the contact area enhances the structural integrity and durability of the part. The processed data used to operate the at least one ejector  12  can be used by the controller  18  to operate the cutting device  14  to cut multiple mesh pieces  13  that are individually placed onto the top layer of the part. The cutting device  14  is configured to cut the mesh material using various methods of cutting that are known to those skilled in the art. In one embodiment, the cutting device  14  is a laser cutting system and in another embodiment, the cutting device  14  is a reciprocating blade system operatively connected to an actuator configured to move the reciprocating blade system in response to signals received from the controller  18  to cut the mesh into shapes corresponding to the data used to operate the ejectors that formed the part. That is, the controller  18  operates the actuator  16  in the positive and negative X, Y and Z directions to move the at least one piece of mesh material  13  from the cutting device  14  to a top surface of the at least one layer of cured photopolymer material. To aid in strengthening the part, the controller  18  can also operate the actuator  16  to vary the orientation of the mesh pieces within a layer or in different layers. Finally, the controller  18  operates the at least one ejector  12  to add additional layers after the at least one piece of mesh material  13  is added to the top layer of cured photopolymer material to form at least one other layer of photopolymer material on top of the at least one piece of mesh material  13 . The mesh piece or pieces laid on the top surface of the cured photopolymer need not conform to the boundaries of the top layer. For example, a portion of the mesh piece or pieces can extend beyond the edges of the top layer. The extension portion of a piece can be used to manipulate the part during production or used as support for material to be ejected later. Once the part is completed, the extensions of the mesh pieces can be removed by known processes. The process of adding layers and mesh pieces is continued until the three-dimensional part  11  is completed. 
     Several additional embodiments of the aforementioned system are disclosed below. In one embodiment, as shown in  FIG.  3   , the system further comprises an optical sensor  26  configured to generate image data of at least one layer of the photopolymer material forming an object. The controller  18  is operatively connected to the optical sensor  26  to receive image data generated by the optical sensor  26  that corresponds to an image of the various features of the layer of photopolymer material, particularly its shape. These image data are sent to the controller  18 , which generates signals for operating the cutting device  14  and the at least one ejector  12 . The cutting device  14  then cuts the next piece of mesh material  13  to the desired specifications corresponding to the signals based on the image data generated by the optical sensor  26  sent from the controller  18 . The controller  18  may also take these data and operate the at least one ejector  12  to account for variations in the top surface of the layer of cured photopolymer material produced by the addition of the at least one piece of mesh material  13 . When the at least one piece of mesh material  13  is added to the top surface of the layer of cured photopolymer material, ridges or bumps may develop around the mesh. Also, the mesh itself may be raised above the plane of the top surface of the layer of cured photopolymer material. Therefore, the layer of photopolymer material that is to be added on top of the mesh must account for these deformities in the top layer surface. The optical sensor  26  captures this information and generates image data corresponding to this information, which is sent to the controller  18 . As noted above, the mesh material is permeable so the build and support material can fill the interstitial space within the mesh material and the amount of ejected material can be varied by location to level the top surface in the next photopolymer layer. Thus, controller  18  operates the at least one ejector  12  with reference to these image data to add more photopolymer material in some areas and less in others to achieve a flat top surface on the next layer of photopolymer material. 
     As noted above, the controller  18  can be configured to generate signals for operating the cutting device  14  with reference to image data used by the controller  18  to operate the at least one ejector  12  for forming the at least one layer of photopolymer material. In this configuration, the image data used by the controller  18  for each layer comes directly from the three-dimensional part file  20 . Image data does not come from the actual part  11  being constructed, and thus does not show any possible minute imperfections or unintended alterations that may have occurred during the building process. Similar to the previously discussed embodiment, the image data are used by the controller  18  to operate the cutting device  14  to cut each mesh piece  13 . Additionally, the controller  18  may take this image data from the part file and modify it with empirically determined data corresponding to variations in the top surface of the layer of photopolymer material in which at least one piece of mesh material  13  has been embedded. This empirically determined data corresponding to imperfections and ridges in the top surface of the layer of photopolymer material in which a mesh piece has been embedded is stored in the memory with the part file  20  before the building process begins. The controller  18  then takes this empirically determined data and operates the at least one ejector  12  to add more photopolymer material in some areas and less material in other areas to achieve a flat top surface on the next layer of photopolymer material. 
     These imperfections in the layer of photopolymer material applied over the mesh piece or pieces may be compensated using other methods as described in the following embodiments. In one embodiment, the system  100  as shown in  FIG.  3    may further comprise a second actuator  28  configured to move a plate or roller  30  with reference to the substrate  10 . The controller  18  is operatively connected to the second actuator  28  and is further configured to operate the second actuator  28  to press the plate or roller  30  into the layer of photopolymer covering the at least one piece of mesh material. When the plate or roller  30  is pressed into the layer of photopolymer covering the at least one piece of mesh material  13 , it pushes the photopolymer material into the at least one piece of mesh material  13 . Once the layer of photopolymer material is pushed into the mesh piece or pieces, the at least one piece of mesh material  13  is positioned slightly below, slightly above, or completely flush with the top surface of the layer of photopolymer material applied over the mesh piece or pieces. This positioning ensures that the top surface of the layer of photopolymer material is relatively flat and thus ready to receive the next layer of photopolymer material from the at least one ejector  12 . The plate or roller  30  may consist of a cylindrical rolling device that rolls over the layer of photopolymer material and the at least one piece of mesh material  13 . The plate or roller  30  may also consist of a warm plate that is pushed into the layer of photopolymer material and the at least one piece of mesh material  13  to warm the photopolymer layer to help adhere the at least one piece of mesh material  13  to the layer of photopolymer material applied to the mesh and level the top layer of the photopolymer material. 
     In another embodiment, the imperfections in the top surface of a layer of photopolymer material applied to one or more mesh pieces are repaired with a leveler  32  configured to remove a portion of the at least one layer of photopolymer material applied to the mesh piece or pieces. The controller  18  is operatively connected to the leveler  32  and is further configured to operate the leveler  32  to remove a portion of the at least one other layer of uncured photopolymer material applied to the mesh piece or pieces. The portion to be removed from the at least one other layer of uncured photopolymer material is any portion of the top surface of the last layer that is protruding or otherwise affecting the flatness of the top surface. Once these portions are removed, the top surface of the last layer of photopolymer material is sufficiently level to have additional layers of photopolymer material added on top of it. Not every layer is required to be perfectly level since data from the optical sensor  26  or the image data from the part file can be used to account for these imperfections and operate the at least one ejector  12  to form the next layer accordingly. 
     Another embodiment of system  100 , shown in  FIG.  3   , includes a robotic arm  34 , which is used to position a piece or pieces of mesh on the part being manufactured. The actuator  16  is operatively connected to the robotic arm  34  to enable the controller  18  to operate the actuator  16  to move the robotic arm  34  and position the at least one mesh piece  13  onto the layer of photopolymer material. Consequently, operation of the robotic arm  34  improves the speed and efficiency of the process of placing the at least one piece of mesh material  13  onto the top surface of the layer of photopolymer material. In this embodiment, pre-cut pieces of mesh  13  can be stored on another platen or the cutting device  14  can be operated by the controller  18  to cut the pieces of mesh. To facilitate the mesh shapes conforming to areas of the part being formed, a number of pre-cut mesh pieces having different widths and lengths can be stored on the platen or the cutting device  14  can be supplied with rolls of mesh having different widths. The controller  18  then picks the pieces of mesh  13  off of the platen to place them on the part  11 . Because the system  100  forms objects with curable liquid photopolymers, a source of UV radiation  36  is included in the system shown in  FIG.  3   . The controller  18  is operatively connected to the source of UV radiation  36  and is configured to operate the source of UV radiation  36  to cure the liquid photopolymer material ejected from the at least one ejector  12 . This curing of the part  11  can be done from time to time as needed. The part can be moved away from the at least one ejector  12  to where the source of UV radiation  36  may directly hit the part  11  and cure it. The part can then be moved back into its original position so the at least one ejector  12  can be operated to continue the building process. 
     An additive manufacturing method  200  for embedding a mesh piece or a plurality of mesh pieces in a three-dimensional structure is shown in  FIG.  4   . In the description of this method, statements that a process is performing some task or function refers to a controller or general purpose processor executing programmed instructions stored in a memory operatively connected to the controller or processor to manipulate data or to operate one or more components in the printer to perform the task or function. The controller  18  noted above can be such a controller or processor. Alternatively, the controller  18  can be implemented with more than one processor and associated circuitry and components, each of which is configured to form one or more tasks or functions described herein. 
     The controller  18  ( FIG.  1   ) operates at least one ejector  12  in a plurality of ejectors  12  to form at least one layer of a liquid photopolymer material on a substrate (block  204 ). The controller  18  then determines whether to add a piece of reinforcing mesh material  13  to the top surface of the layer of photopolymer material (block  208 ). If the data from the file  20  indicates no piece of mesh material is to be added, the controller  18  operates one or more ejectors  12  with image data for the next layer to form another layer of photopolymer material on top of the previous layer of photopolymer material (block  204 ). This determination is made with reference to image data received by the controller  18  from a three-dimensional part file  20 . If the data indicates a piece of mesh material is to be added, the controller  18  operates the radiation source  36  to cure the ejected photopolymer partially (block  210 ). As used in this document, “partially cured” means one or more layers of photopolymer have not been fully cured by exposure to a curing radiation. The shape or outline of one or more mesh pieces are identified (block  212 ). The outline identification is performed by processing image data received from the three-dimensional part file  20  or by processing image data received by the controller  18  from the optical sensor  26 , which is positioned to capture image data from the part  11  as it is being constructed. The controller  18  then operates a robotic arm  34  to select an appropriate mesh piece or the controller can operate cutting device  14  using either the image data from the three-dimensional part file  20  or the image data from the optical sensor  26  to cut at least one piece of mesh material  13  into the identified shape (block  216 ). Any method of cutting known in the art may be employed to operate the various cutting devices previously noted to cut the at least one piece of mesh material. The robotic arm  34  is then operated by the controller  18  to add one or more pieces of mesh material  13  to the top surface of the partially cured layer (block  220 ). The at least one piece of mesh material  13  is placed directly onto the top surface of the layer of the partially cured photopolymer material with an appropriate orientation of the filaments in the piece and is allowed to protrude above the photopolymer material. The controller  18  operates the at least one ejector  12  to eject additional photopolymer material onto the at least one piece of mesh material  13  to form at least one other layer of photopolymer material on the at least one piece of mesh material  13  (block  224 ). The distribution of photopolymer material to form the next layer of photopolymer material can be determined either from image data sent to the controller  18  from the three-dimensional part file  20  or from the optical sensor  26 . 
     To address possible imperfections in the top surface of the applied layer, the controller  18  then optionally operates a second actuator  28  to press a plate or roller  30  into the applied layer of photopolymer material and the at least one piece of mesh material  13  (blocks  228  and  232 ). The controller  18  operates the plate or roller  30  to either roll a cylindrical rolling device over the applied layer and piece of mesh material  13  or press a plate, which may be warm, against the applied layer and the at least one piece of mesh material  13 . The cylindrical rolling device pushes the applied layer of photopolymer material into the mesh material  13 , helping to flatten the mesh so that the next layer of photopolymer material may be accurately added. The plate, which may be warm, pushes and flattens the mesh material  13  into the layer, as well as warming it so that it further adheres to the layer of photopolymer material. 
     Additionally or alternatively, the imperfections in the top layer of the applied photopolymer can be addressed by using a leveler to remove imperfections. Thus, the process continues by determining whether the applied layer should be leveled (block  236 ), and if it is, the controller  18  operates a leveler to remove portions of the applied layer of uncured photopolymer (block  240 ). The operation of the leveler  32  removes any portion of the top surface of the applied layer of photopolymer material that is protruding or otherwise affecting the flatness of the top surface of the layer. Once the optional leveling is complete, the controller  18  then determines from the image data whether to add additional layers of photopolymer material and possibly mesh material to the part  11  (block  244 ). If the controller  18  determines to continue adding layers, the method continues (block  204 ). If the controller  18  determines no additional layers are to be added to the part  11 , the method is complete (block  248 ). At any point during the process of method  200 , other than the ones noted above, the layers of photopolymer material may be optionally cured by a source of UV radiation  36 . If it is determined by the controller  18  that the layer of photopolymer material needs to be cured, the controller  18  operates the source of UV radiation  36  to cure the last applied layer of photopolymer material. 
     In another alternative embodiment of the system shown in  FIG.  3   , the robotic arm  34  and cutting device  14  are replaced by a fiber dispenser  504  shown in  FIG.  5   . The dispenser  504  is operatively connected to the actuator  16  so the controller  18  can operate the actuator  16  to position the dispenser  504  in different X, Y positions in various planes above the part  11 . The dispenser  504  includes a body  508  that tapers to a nozzle  512 . A plurality of bins  516  are configured for selective communication with the interior of the body  508  and nozzle  512 . When a bin  516  is moved to a position that enables the bin to communicate with the interior of the body  508  and the nozzle  512 , short individual fibers stored within the bin pass through the body  508  and exit through the nozzle  512 . Thus, by operating the actuator  16  to position the nozzle  512  above a position over a cured photopolymer layer where fibers are to be positioned and then moving a bin  516  to a position that enables the fibers to be discharged through the nozzle  512 , fibers can be deposited on the part  11 . Additional layer(s) can then be applied to the fibers and adjusted for imperfections in the top surface with a roller or leveler as explained above. 
     It will be appreciated that variants of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems, applications or methods. Various presently unforeseen or unanticipated alternatives, modifications, variations or improvements may be subsequently made by those skilled in the art that are also intended to be encompassed by the following claims.