Abstract:
A 3D printer for building 3-dimensional object using DLP technique, comprising a solidifiable material container, an irradiation component, a supporting component, a surface regulation component, and a control system. The 3D printer realizes large dimension and high speed printing by applying a flexible film over the surface of the photopolymer resin. The flexible film is separated from the solidified resin by peeling force.

Description:
BACKGROUND 
     1. Field of the Invention 
       [0001]    The present invention relates to a 3D printer. More particularly, the 3D printer is based on Digital Light Processing, and the photopolymer resin is cured at the top surface which is regulated by a plane film. 
       2. Discussion of the Related Art 
       [0002]    Three dimensional (3D) printing is a process to form a three-dimension object. Different from traditional processes such as casting and cutting, 3D printing utilizes adding instead of removing materials to form the solid object which could have complex shape or geometry. This process is also known as additive manufacturing (AM), rapid prototyping or solid freeform fabrication. The machine to perform the process is called 3D printer. 
         [0003]    Basically, 3D printing is achieved by building an object layer by layer from a particular material such as powered metal, droplets of plastic or any other appropriate material. Each of these layers is a thin slice cross-section of the eventual object which is generated by process similar to regular 2D printing in x and y dimensions. All layers are laid over successively in z dimension. With the thickness of these layers accumulated, a 3D object is formed. 
         [0004]    There are number of different technologies developed based on different materials and the ways to form the layers, for example, Fused Deposition Modeling (FDM), Stereolithography (SLA), 3D Inkjet Powder (3DP), Selective Laser Sintering (SLS). 
         [0005]    Digital Light Processing (DLP) is one of the well developed technologies recognized by its relatively high resolution and high speed. In this process, liquid solidifiable material (e.g., photopolymer resin) contained in a vat is exposed to visible light or UV light generated by DLP projector. The DLP projector displays the image of the 3D model onto the surface of the liquid solidifiable material. The exposed solidifiable material is solidified (or cured) to form a solid layer with desired pattern according to the image. Then the object is drawn away from the surface to let the liquid solidifiable material to fill in for next layer. By repeating the process a new layer is formed over previous layer until the 3D object is complete. Compare with SLA which uses a UV laser beam to cure the photopolymer resin spot by spot, DLP generates irradiation over its display area simultaneously to tremendously increase the curing speed. At the same time, benefiting from the projector technology, high resolution is available. 
         [0006]    There are two ways to cure solidifiable material in DLP. One is called “top-down” in which new layers are formed at the top surface of the growing object. In this method, after each irradiation step the object under construction is submerged into the liquid solidifiable material, a new layer of solidifiable material is coated on top, and a new irradiation step takes place. During this process, it is necessary to reconstitute a layer of solidifiable material accurately because the thickness of the layer defined the resolution in z dimension. Obviously, this increases the processing time and complexity of the system. At the same time, the surface of each solidified layer must be smooth and planar in order to apply new irradiation step. Some techniques utilize of a paddle or a blade to sweep across the surface of the solidified layer to remove irregularities in the surface profile thereof. One of the reasons of the irregularities is surface tension because the top surface of the material is exposed to air. Again, this technique introduces additional processing time and mechanical complexity. 
         [0007]    The other technique is called “bottom-up” in which new layers are formed at the bottom surface of the growing object. After each irradiation step the object under construction must be separated from the bottom plate of the vat. One big issue with such “bottom-up” techniques is that an accurately controlled force must be applied when separating the solidified layer from the bottom plate caused physical and chemical adhesive effect. Sometimes the required separation force is so great that it can deform or break the object. 
         [0008]    Although DLP is already widely used and is available for desk-top printing, the application in commercial level is still limited. There are two disadvantages preventing DLP from involving in more area. First, the size of the object is limited; second, the process is still not fast enough. 
         [0009]    Since the light source is DLP projector, the size of the object in x and y dimension is limited by the display area of the projector. But based on current projector performance, the display area can&#39;t be enlarged without sacrificing the resolution. 
         [0010]    In bottom-up technique, larger size in x and y dimension means larger contact area between solidified material and the bottom of the vat, this will request larger separation force. However solidified material can only afford limited separation force to avoid deformation and which also restricts the size of the object. 
         [0011]    Regarding processing speed, the operations of the surface of the object, such as sweeping the surface with a paddle, or separating the object form the bottom of the vat, consume a large amount of time. 
         [0012]    Considering all these disadvantages mentioned above, it would be desirable to provide an apparatus and method in 3D printing to enlarge the object dimension, reduce the processing time, and simplify the mechanism. 
       BRIEF SUMMARY OF THE INVENTION 
       [0013]    The primary objective of the present invention is to develop a 3D printing apparatus and method applicable in commercial applications. 
         [0014]    Another objective of the present invention is to develop a 3D printing apparatus and method to fabricate objects with large dimensions. 
         [0015]    Another objective of the present invention is to develop a 3D printing apparatus and method to fabricate objects with high speed. 
         [0016]    Another objective of the present invention is to develop a 3D printing apparatus with simplified mechanism. 
         [0017]    The invention comprises the following, in whole or part: 
         [0018]    An irradiation component, a solidifiable material container, a supporting component, a surface regulation component, and a control system. 
         [0019]    The irradiation component comprises a projector to generate irritation over designated area on the top surface of the solidifiable material. 
         [0020]    The solidifiable material container contains the liquid solidifiable material. 
         [0021]    The supporting component provides a substrate for the solidifiable material to be solidified over it to form the object, and levels the solidified lay of the object at a desired position. 
         [0022]    The surface regulation component comprises a regulation plane which provides a flat and smooth surface. This regulation plane is placed over the liquid solidifiable material therefore the top surface of the liquid solidifiable material is covered by the surface of the regulation plane. In this way a portion of the surface of the liquid solidifiable material is regulated in flat, the surface tension effect is eliminated. The surface regulation component also comprises a mechanism to peel the regulation plane from the solidified layer of the under building object. 
         [0023]    The control system provides data to the projector for generating desired patterns, and controls the irradiation component, the supporting component, and the surface regulation plane to cooperate together. 
         [0024]    For a more complete understanding of the present invention with its objectives and distinctive features and advantages, reference is now made to the following specification and to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING(S) 
         [0025]      FIG. 1  is a schematic view of a 3D printer according to the present embodiment of the invention. 
           [0026]      FIG. 2  is a schematic view of the 3D printer according to the present embodiment of the invention. 
           [0027]      FIG. 3  is a schematic view of the surface regulation component illustrating the peeling process according to the present embodiment of the invention. 
           [0028]      FIG. 4  is a schematic view of the surface regulation component illustrating the peeling process according to an alternative embodiment of the invention. 
           [0029]      FIGS. 5A and 5B  illustrate a process for the projector to irradiate the working area. 
           [0030]      FIGS. 6A and 6B  illustrate an alternative process for the projector to irradiate the working area. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0031]    In accordance with a preferred embodiment,  FIGS. 1 to 4  depict the machine as a presently embodiment, wherein machine comprises an irradiation component  10 , a solidifiable material container  20 , a supporting component  30 , a surface regulation component  40 , and a control system  50 . A 3D object  60  is under building. 
         [0032]    The irradiation component  10  comprises an irradiation source  11  which generates desired irradiation. In a preferred embodiment, the irradiation source  11  is a DLP projector  11  which generates visible light, UV light, or other forms of light. The irradiation component  10  also comprises a positioning mechanism  12 . The positioning mechanism  12  is controlled by the control system  50  to move the projector  11  vertically (in z direction), and position the projector  11  with a predetermined height over the surface of the liquid solidifiable material  21 . By adjusting the height, the resolution and display area of the projector  11  can be accurately controlled if the projector  11  is focused. 
         [0033]    In a preferred embodiment of the present invention, the positioning mechanism  12  also moves the projector  11  horizontally (in x and y directions). In this manner, the irradiation area of a single projector can be extended, which means the size of the cross section of the object  60  will not be limited by the display area of the projector  11 . 
         [0034]    The solidifiable material container  20  is a vat with an opening at the top. The vat  20  contains solidifiable material  21  which can be solidified by the irradiation generated by the projector  11 . In a preferred embodiment, the solidifiable material  21  is a liquid photopolymer resin. The solidifiable material container  20  has a predetermined size in x, y and z dimensions which is enough to merge the whole 3D object  60  within. 
         [0035]    The supporting component  30  comprises an object platform  31  providing a substrate for the object  60  to be laid upon and supporting the under building object  60 . The object platform  30  also comprises a supporting mechanism  32  which is mechanically coupled with the object platform  31 . The supporting mechanism  32  moves the object platform  31  in z direction and can submerge the object  60  in the resin  21  and let a layer of liquid resin  21  with predetermined thickness fill over the top surface of the under building object  60 . 
         [0036]    The surface regulation component  40  comprises a regulation plane  41  which is transparent to the irradiation, and a supporting frame  42  which retains the regulation plane  41 . The regulation plane  41  has a smooth and planar surface facing the resin  21  and is leveled in parallel with the surface of the resin  21 . The supporting frame  42  places the regulation plane  41  on the surface of the resin  21  with no gap in between, therefore the regulation plane  41  is fully contacted with the surface of the resin  21 . In this manner, the contact area of the resin  21  under the regulation plane  41  is regulated into a smooth plane. This eliminates the irregularities caused by surface tension effect, etc. 
         [0037]    The object platform  31  of the supporting component  30  is under the regulation plane  41 . Through the operation of the supporting mechanism  32 , the top surface of the under building object  60  is placed beneath the regulation plane  41  with a predetermined distance so a thin layer of liquid resin is filled in between. The projector  11  of the irradiation component  10  is positioned above the regulation plane  41  by the positioning mechanism  12  and projects irradiation over the thin layer of the resin  21  through the regulation plane  41 . This thin layer of liquid resin  21  will be cured by the irradiation on the top surface of the under building object  60  to form a new solidified layer. 
         [0038]    Referring to  FIG. 1  and  FIG. 3 , in one embodiment of the present invention, the regulation plane  41  just covers the display area of the projector  11 . The supporting frame  42  of the surface regulation component  40  is coupled with the positioning mechanism  12  of the irradiation component  10  in a manner that the projector  11  and the regulation plane  41  are retained together. In this way once the projector  11  is moved to a new position, the regulation plane  41  will be moved together to regulate the new surface area of the resin  21 . The area of the regulation plane  41  may be smaller than the cross section of the object  60 . 
         [0039]    Referring to  FIG. 2  and  FIG. 4 , in an alternative embodiment of the present invention, the regulation plane  41  covers the whole area of the cross-section of the object  60 . This area is larger than the display area of the projector  11 . In this way, during solidification, the regulation plane  41  remains still on the surface of the resin  21  while the projector  11  is moved over the regulation plane  41  to irradiate different area. 
         [0040]    In a preferred embodiment of the present invention, the regulation plane  41  is formed by a transparent flexible film  43  which is shaped by the supporting frame  42 . Preferably, the film  43  is an elongated band with the two ends rolled. Referring to  FIGS. 1 to 4 , the supporting frame  42  comprises a first holder  421  holding the first end of the film  43 , and a second holder  422  holding the second end of the film  43 . Both holders  421 ,  422  coupled with the two ends of the film band  43  by rolling the ends, and maintain a tension through the film  43 . The supporting frame  42  also comprises a first shaft  423  and a second shaft  424  under the holders  421 ,  422 . Both shafts  423 ,  424  are at the same level and are parallel to the surface of the liquid resin  21 . The middle portion of the film  43  is pushed by the two shafts  423 ,  424  to form a flat plane as the regulation plane  41 . In an embodiment of the present invention, the each holder comprises a motor  425  to rotate the film band  43 . The motor  425  is controlled by the control system  50 . 
         [0041]    Once the liquid resin  21  is cured under the regulation plane  41 , the new solidified layer may be adhered to the regulation plane  41  due to physical and chemical interaction. Therefore the regulation plane  41  needs to be lifted away from the solidified layer. 
         [0042]    Referring to  FIG. 4 , during the lifting process, in one embodiment of the present invention, the position of the second holder  422  and the second shaft  424  are fixed with the vat  20 , the first holder  421  and the first shaft  423  are moving horizontally towards the second holder  422  and the second shaft  424 . At the same time, the first holder  421  is rolling the film  43  to maintain the tension of the film  43  and to apply peeling force. 
         [0043]    Once the first and second shaft  423 ,  424  are closed together, the film  43  is totally separated from the solidified layer of the object  60 . Then the object  60  will be lowered by the supporting component  30  to fill a new layer of resin  21 . To regulate the new layer of resin  21 , the first holder  421  and the first shaft  423  are moved away from the second holder  422  and second shaft  424 . If the first holder  421  releases the rolled film  43 , the old area of the film  43  will be reused as the regulation plane  41 . If the second holder  422  releases the rolled film  43 , new area of the film  43  will be used as the regulation plane  41 . 
         [0044]    In prior art of bottom-up technique, the object needs to be pulled from the bottom of the vat which is a rigid surface. Therefore the tensile force applied should overcome the adhesive force from the whole area of the solidified layer. But in the present invention, the flexible film  43  is peeled from the solidified layer. Therefore, only adhesive force from the edge of the film  43  under the shaft needs to be overcome. Compare with the whole area of the solidified layer, the area of the edge under the shaft is much less. Consequently, the required peeling force is much less. 
         [0045]    In an alternative embodiment of the present invention, the supporting frame  42  moves the two holders  421 ,  422  and the two shafts  423 ,  424  together in x direction. During the movement, the two holders  421 ,  422  roll and unroll the film  43  respectively to maintain the tension, and remain the regulation plane  41  relatively still with the resin  21 . For example, referring to  FIG. 3 , when the supporting frame  42  moves from left to right, the first holder  421  rolls the film  43  and peel the film  43  from the first shaft  423 ; the second holder  422  unrolls the film  43  and the second shaft  424  paves the film  43  over the new area of the resin  21  in right. 
         [0046]    It is worth mentioning, once the film  43  is peeled, the same area of the film  43  can be reused. Or alternatively, used area will be rolled in by the first holder  421 , and new area will be rolled out by the second holder  422 , new area of the film  43  can be applied to form the regulation plan  41  for next layer of solidification. 
         [0047]    The control system  50  is electrically connected with the irradiation component  10 , the supporting component  30 , and the surface regulation component  40 . The control system  50  provides data to the irradiation component  10  for generating required display, at the same time controls the movement of the other components to perform 3D printing. 
         [0048]    In one embodiment of the present invention, the dimension of the cross section of the object  60  is larger than the display area of the projector  11 . In order to irradiate the entire area of the cross section of the object  60 , the projector  11  is moved by the positioning mechanism  12  horizontally to irradiate different area. Referring to  FIGS. 5A and 5B , the whole cross section of the object  60  is divided into multiple sections. Each section can be covered by the display of the projector  11 . The projector  11  is moved over these sections individually and displays the relative images on the sections to cure the resin  21 . 
         [0049]    Referring to  FIGS. 6A and 6B , in an alternative embodiment, the projector  11  is moved over the cross section of the projector  11  continuously like scanning the whole area. The positioning mechanism  12  utilizes step motor to make the movement. After each step of movement, the image displayed by the projector  11  will be shifted to make sure same image is displayed on the same area of the resin  21 . 
         [0050]    While the embodiments and alternatives of the invention have been shown and described, it will be apparent to one skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention.