Abstract:
Devices, systems and methods are disclosed which facilitate reduction of separation forces in additive manufacturing devices, thereby enabling creation of higher resolution parts. In an aspect, an additive manufacturing device utilizing a photopolymer comprises a vat holding photocurable resin, a build platform movable in a vertical direction and an image source which selectively projects part cross sections into the vat in order to polymerize the resin and form a part in a layer-wise fashion. The image area of the vat is formed by a transparent film, such as Teflon FEP film, stretched under tension. A horizontally slideable shutter is slideable between the film and the imager, providing support for the film when needed.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/974,366 filed Apr. 2, 2014, and entitled “Additive Manufacturing Device with Sliding Plate and Peeling Film,” the entire contents of which are incorporated herein by reference, 
     
    
     FIELD OF THE DISCLOSURE 
       [0002]    The present disclosure generally relates to additive manufacturing devices and more particularly to improvements in separating cured layers from the build area. 
       BACKGROUND 
       [0003]    The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
         [0004]    Additive manufacturing devices produce three-dimensional parts by sequentially adding materials in a pattern. Some classes of additive manufacturing devices produce polymer parts solidified from a photopolymer resin which has been exposed in a layer-wise fashion to electromagnetic radiation generated by a light source such as a projector. The light source projects a cross sectional image into a build area, solidifying a layer of photopolymer resin into a hardened layer, thereby adding another layer to the object being formed. In order to create parts with a high degree of detail and accuracy, removing the hardened layer from the build area without deforming, destroying, or otherwise damaging the layer or other portions of the part is essential. 
         [0005]    When the layer is formed, the newly-formed layer often adheres to an image surface found in the build area. Two types of forces prevent separation at the interface between the image surface and the newly-formed layer: (1) the adhesion force between the image surface and the newly-formed layer; and (2) a vacuum force present between planar objects in a fluid. The adhesion force is comprised of chemical bonding forces between the image surface and the newly-forced layer. In some embodiments, the adhesion force also comprises mechanical adhesion forces between the image surface and the newly-formed layer. In order to separate the part from the image surface and continue assembling it, a separation force must be applied in order to overcome the adhesion and vacuum forces present. Application of the separation force stretches and strains the part being formed in non-uniform, undesirable ways. In some cases, the separation force is strong enough to distort or destroy fragile portions of a part because the fragile portion is stretched, strained, and even completely separated from the part as the part is repositioned to form the next layer of the part. Because this separation force destroys or damages fine detailing in a desired part design, resolution has been limited. Parts containing, for example, very thin segments or intricate detailing (e.g. channels, tubing, etc.) cannot be produced, are produced with an extremely high failure rate, or must be produced at a very slow rate using different photopolymers in order to produce a part containing fragile sections that will not deform when exposed to the separation forces. 
         [0006]    Some additive manufacturing devices utilize a thin film as the build surface or image surface. Such films include Teflon® films (available from Du Pont Co. of Wilmington, Del.) or other non-stick materials. The film may also be a flexible polyurethane or other material. Such devices struggle to ensure a uniform distribution of material to create subsequent layers during the build process. 
         [0007]    Given the foregoing, what is needed are devices, systems and methods which facilitate creating a part via additive manufacturing wherein separation forces are reduced. Furthermore, providing a constant, uniform layer of photopolymer resin to form subsequent layers from is desired. 
       SUMMARY 
       [0008]    This Summary is provided to introduce a selection of concepts. These concepts are further described below in the Detailed Description section. This Summary is not intended to identify key features or essential features of this disclosure&#39;s subject matter, nor is this Summary intended as an aid in determining the scope of the disclosed subject matter. 
         [0009]    In an aspect, an additive manufacturing device comprises a vat holding photocurable resin, a build platform movable in a vertical direction and an image source which selectively projects part cross sections into the vat in order to polymerize the resin and form a part in a layer-wise fashion. The image area of the vat is formed by a transparent film, such as Teflon FEP film, stretched under tension. A first layer is produced by projecting a cross section onto the image area, hardening a layer of photopolymer between the film and the build platform. The build platform is raised a distance greater than one layer height, thereby removing the first layer from the film via peeling away. After the first layer is elevated, liquid resin flows in, providing a new quantity of uncured resin for subsequent layer formation. A horizontally movable shutter slides between the film and the imager, providing a support for the film. The build platform is then lowered into a position one layer height away from the film, expelling any excess liquid resin while providing sufficient material to for the subsequent layer to be cured. The shutter is then retracted and a cross section of the subsequent layer is projected onto the image area, hardening the subsequent layer. This process is repeated until the part is completed. 
         [0010]    This method eliminates the undesirable “vacuum” effect during the lifting process that is inherent when supporting a film with a transparent plate. To do this, the shutter is slideable under the film to support it when the part is lowered into position. After the lowering, the shutter slides away, allowing the next exposure. Additionally, the shutter may be used to block exposure while the imager is being prepared for the subsequent exposure. A rigid transparent member may be positioned between the film and the shutter in order to provide additional support for the film. 
         [0011]    Devices, systems and methods in accordance with the present disclosure enable reduced separation force and therefore enable higher resolution additive manufacturing devices by eliminating the vacuum effect between the, film and the support plate. If the support plate is present during imaging, the support plate is slidably moved from underneath the film after a layer is exposed, leaving no surface for the film to adhere to on one side. 
         [0012]    Further features and advantages of the present disclosure, as well as the structure and operation of various aspects of the present disclosure, are described in detail below with reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The features and advantages of the present disclosure will become more apparent from the Detailed Description set forth below when taken in conjunction with the drawings in which like reference numbers indicate identical or functionally similar elements. 
           [0014]      FIG. 1  is a schematic side view of an additive manufacturing device having an opaque sliding shutter, the shutter being in a supported position, according to an aspect of the present disclosure. 
           [0015]      FIG. 2  is a schematic side view of the additive manufacturing device of  FIG. 1 , the shutter being in the unsupported position, according to an aspect of the present disclosure. 
           [0016]      FIG. 3  is a schematic side view of an additive manufacturing device having a sliding shutter with a cutout area, the shutter being in an exposure position, according to an aspect of the present disclosure. 
           [0017]      FIG. 4  is a schematic side view of the additive manufacturing device of  FIG. 3 , the shutter being in the unsupported position, according to an aspect of the present disclosure. 
           [0018]      FIG. 5  is a flowchart illustrating an exemplary process for forming a part layer using the additive manufacturing device of  FIG. 1 , according to an aspect of the present disclosure. 
           [0019]      FIG. 6  is a flowchart illustrating an exemplary process for forming a part layer using the additive manufacturing device of  FIG. 3 , according to an aspect of the present disclosure. 
           [0020]      FIG. 7  is a flowchart illustrating an exemplary process for forming a part layer  106  using additive manufacturing device  100  of  FIG. 3 ; and. 
           [0021]      FIG. 8  is a block diagram of an exemplary computing system useful for implementing aspects of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    The present disclosure is directed to devices, systems, methods, and computer program products which facilitate consistent curing across a part layer of a part being constructed via an additive manufacturing device. 
         [0023]    In an aspect, each element of the part layer is exposed to light from a light source until the element receives sufficient energy to cure. The amount of received energy is calculated based on both the light received directly from the light source and light received from surrounding elements due to dispersion and other effects. 
         [0024]    Referring now to  FIG. 1 , a schematic side view of an additive manufacturing device  100 , according to an aspect of the present disclosure, is shown. 
         [0025]    Additive manufacturing device  100  constructs a part  102  by curing photopolymer resin  108  via exposure to electromagnetic radiation  118 , or curing energy, from a light source  114 . Light source  114  projects light  118  into a build area in a pattern which causes a photopolymer layer  106  to harden into a new portion of part  102 , thereby constructing part  102  in a layer-wise fashion. During construction, part  102  is attached to build table  104  or build platform. Build table  104  is configured to support part  102  as part  102  is being constructed. Build table  106  may comprise a planar, movable surface attached to a z-axis actuator  120 . Z-axis actuator  120  is configured to raise part  102  in a step-wise fashion during construction such that additional layers may be added to part  102 . 
         [0026]    Additive manufacturing device  100  may comprise basin  110  or vat. Basin  110  is configured to house resin  108  and is static. A build area or imaging area where light  118  is projected forms a portion of basin bottom. In an aspect, a bottom portion of basin  110  corresponding with the build area is a transparent, tensioned film  124 . Film  124  may be Teflon FEP film. In another aspect, film  124  is a polyurethane film, a flexible transparent material, a flexible translucent material, or another material apparent to those skilled in the relevant art(s) after reading the description herein. Basin  110  may comprise tensioners, clamps, or other portions which set and hold film  124  in place. In some aspects, a sealer is applied around the edges of film in order to form a watertight seal between basin walls and film  124 . 
         [0027]    A shutter  112  is positioned adjacent to film  124 . Shutter  112  is slideable between multiple positions such as an unsupported position, as shown in  FIG. 1  and  FIG. 4  and an unsupported position, as shown in  FIG. 2 . Shutter  122  is moved by Y-actuator  122 . Shutter  112  may be a rigid member which contacts the underside of film  124  when in the unsupported position. Shutter  112  may be a transparent material, including materials through which light  118  may be transmitted in order to form layer  106  (e.g., glass, acrylic). Shutter  112  may also be an opaque material. Shutter  112  is configured to support film  124  and resin  108  contained in basin  110  when part is lowered or otherwise moved relative to basin  110 . Additive manufacturing device  100  may further comprise a lock, receiver, or other stabilizing portion (not shown) which receives an end or side portion of shutter  112  when shutter  112  is placed in the unsupported position shown in  FIG. 1  in order to stabilize and support shutter  112 . The stabilizing portion may be integrated into basin  110 . 
         [0028]    In some aspects, a friction reducing element  590 , as disclosed further in  FIG. 5 , may be positioned between film  124  and shutter  112 . The friction reducing element may be a felt liner covering all of the cross section of shutter  112  which contacts film  112  when shutter  112  is in a supporting position. In another aspect, the friction reducing element is a strip of material (e.g., a felt liner, a lubricating element, polytetrafluoroethylene tapes, slick surface tape, glide tape and the like) placed along at least a portion of the perimeter of shutter (e.g., two sides, all four sides, and the like). Friction reducing element may be a lubricant such as graphite lubricant, oil-based lubricant, or the like. These lubricants may be periodically applied. 
         [0029]    Referring now to  FIG. 2 , a schematic side view of additive manufacturing device  100  of  FIG. 1 , shutter  112  being in the unsupported position, according to an aspect of the present disclosure, is shown. 
         [0030]    Shutter  112  may be retracted or otherwise moved in a variety of directions in order to expose resin  108  for solidification by image  114 , In an aspect where shutter  112  is opaque, shutter  112  may be retracted, leaving film  124  unsupported by shutter and enabling imager to solidify layer  106  via exposing resin  108  to light  118 . When shutter  112  is retracted into an unsupported position, film  124  is free to deflect up or down and is not held in place by vacuum forces between shutter  112  and film  124 . 
         [0031]    When shutter  112  is in the closed position, part  102  may be pushed against resin  108  and film  124  in order to ensure that only a chosen depth of uncured resin exists between film  124  and part  102 . Where shutter is transparent, layer  106  may be formed when shutter is in the closed position ( FIG. 1 ) or in the unsupported position ( FIG. 2 ). 
         [0032]    Referring now to  FIGS. 3 and 4 , schematic side views of additive manufacturing device  100  having a sliding shutter  112  with a cutout area  304 , according to an aspect of the present disclosure, is shown. 
         [0033]    Shutter  112  may be an assembly comprising a transparent window  302  and a cutout area  304  or recess. Transparent window  302  is slidably positionable adjacent to film  124 . Device  100  may image a new layer  106  through transparent window  302  when window  302  is in the position shown in  FIG. 3 . 
         [0034]    Cutout area  304  is a recess in shutter  112 . In some aspects, cutout area  304  is sufficiently deep to allow film  124  to deflect downwardly freely. Cutout area  304  may have a cross section equal to the cross section of the build area. In other aspects, the cross section of cutout area  304  is smaller or larger than the build area. When cutout area  304  is moved under film  124 , the vacuum force holding film  124  to shutter  112  is released, facilitating removable of part  102  from film  124  with a smaller separation force. 
         [0035]      FIG. 5  shows an embodiment of a friction reducing element disclosed above. The a friction reducing element  590  may be a protective or sacrificial film, such as, but not limited to Teflon, a cloth or some other material that will have a low coefficient of friction between the friction reducing element  590  and the shutter  112 . Thus, friction may occur between the friction reducing element  590  and the slideable shutter  112  wherein only the friction reducing element  590  may be damaged, such as, but not limited to being scratched. The shutter  112  applies the friction reducing element  590  to the underside of film  124  without sliding the friction reducing element  590  against film  124 , thereby eliminating the possibility of scratching film  124  via relative movement with friction reducing element  590  or shutter  112 . As further illustrated, an optional weight  595  or another approach to ensure that the friction reducing element  590  remains out of a path of the illuminated curing energy when the shutter  112  slides to an open for exposure position. The shutter  112  may have a transitional edge  593  to assist the friction reducing element  590  from moving when acted upon by the weight  595 . Those skilled in the art will readily recognize that other approaches may be implemented to provide for removing the friction reducing element  590  from within a field of the curing energy. Therefore, the embodiment disclosed herein is not meant to be considered limiting. Since there is no sliding motion between the friction reducing element  590  and the film  124 , the film  125  is not damaged. 
         [0036]    Referring now to  FIG. 6 , a flowchart illustrating an exemplary process for forming a part layer using the additive manufacturing device of  FIG. 1 , according to an aspect of the present disclosure, is shown. 
         [0037]    In an aspect, light, electromagnetic radiation, or other curing energy is projected onto a material such as liquid photopolymer resin in order to cure layer  106 . Each portion of layer  106  being formed requires a given amount of energy to cure properly. Each layer  106  is cured to a specified cure depth and the amount of uncured resin  108  between part  102  and film  124  before exposure has a depth equal to or based on the desired cure depth. 
         [0038]    Process  600 , at least a portion of which may execute within computing functionality  800 , utilizes device  100  to produce part  102  via layer-wise manufacturing. Each layer is cured from a photopolyermizable resin  108  after exposure to light  118  during process  600 . Process  600  begins at step  602  with control passing immediately to step  604 . 
         [0039]    At step  604 , shutter  112  is slidably positioned under film  124 . If shutter  112  is already in this position, step  504  is omitted. Positioning of shutter  112  in this step supports film  124  and resin  108  during step  506  and assists in ensuring that a uniform layer of resin  108  is present between part  102  or build platform  104  which will be cured into newly formed layer  106  in step  610 . 
         [0040]    At step  606 , build platform  104  is lowered. In an aspect, build platform  104  is lowered into vat  110  until excess resin  108  is squeezed out from between build platform  104  or attached part  102  and film  124 . Film  124  is supported by shutter  112  during this step, enabling creation of a uniform layer of uncured resin  108 . 
         [0041]    At step  608 , shutter  112  is moved to an exposure position, such as the position shown in  FIG. 2 . In step  608 , the light path between build area and image  114  is cleared. If shutter  112  is transparent, this step may be omitted. 
         [0042]    At step  610 , a cross section of layer  106  to be cured is projected into build area by imager  114 , curing a newly-formed layer  106 . 
         [0043]    At step  612 , part  102  including newly-formed layer  106  is removed from film  124 . Build platform  104  is lifted, causing film  124  to peel away from layer  106 . If shutter  112  is still adjacent to film  124  at the beginning of step  612 , shutter  112  is first slidably moved away from film  124 , thereby eliminating any vacuum forces between film  124  and shutter  112 . 
         [0044]    Process  600  then terminates at step  614 . 
         [0045]    Referring now to  FIG. 7 , a flowchart illustrating an exemplary process for forming a part layer  106  using additive manufacturing device  100  of  FIG. 3 , according to an aspect of the present disclosure, is shown. 
         [0046]    Process  700 , at least a portion of which may execute within computing functionality  700 , utilizes device  100  as configured in  FIGS. 3 &amp; 4  to produce part  102  via layer-wise manufacturing. Each layer is cured from a photopolyermizable resin  108  after exposure to light  118  during process  700 . Process  700  begins at step  702  with control passing immediately to step  704 . 
         [0047]    At step  704 , transparent window  302  is slidably placed adjacent to film  124 , providing support for film  124 . 
         [0048]    At step  706 , build platform  104  is lowered. In an aspect, build platform  104  is lowered into vat  110  until excess resin  108  is squeezed out from between build platform  104  or attached part  102  and film  124 . Film  124  is supported by shutter  112  during this step, enabling creation of a uniform layer of uncured resin  108 . 
         [0049]    At step  708 , a cross section of layer  106  to be cured is projected into build area by imager  114 , curing a newly-formed layer  106 . 
         [0050]    At step  710 , shutter  112  is slidably moved, positioning cutout area  304  below film  124 , thereby eliminating vacuum forces between film  124  and window  302 . 
         [0051]    At step  712 , part  102  is removed from film  124  via lifting build platform  104 . 
         [0052]    Process  700  then terminates at step  714 . 
         [0053]    Referring now to  FIG. 8 , a block diagram of an exemplary computer system useful for implementing various aspects the processes disclosed herein, in accordance with one or more aspects of the present disclosure, is shown. 
         [0054]    That is,  FIG. 8  sets forth illustrative computing functionality  800  that may be used within device  100 , to implement processes  600  or  700 , or any other component utilized herein. In all cases, computing functionality  800  represents one or more physical and tangible processing mechanisms. 
         [0055]    Computing functionality  800  may comprise volatile and non-volatile memory, such as RAM  802  and ROM  804 , as well as one or more processing devices  806  (e.g., one or more central processing units (CPUs), one or more graphical processing units (GPUs), and the like). Computing functionality  800  also optionally comprises various media devices  808 , such as a hard disk module, an optical disk module, and so forth. Computing functionality  800  may perform various operations identified above when the processing device(s)  806  execute(s) instructions that are maintained by memory (e.g., RAM  802 , ROM  804 , and the like). 
         [0056]    Instructions and other information may be stored on any computer readable medium  810 , including, but not limited to, static memory storage devices, magnetic storage devices, and optical storage devices. The term “computer readable medium” also encompasses plural storage devices. In all cases, computer readable medium  810  represents some form of physical and tangible entity. By way of example, and not limitation, computer readable medium  810  may comprise “computer storage media” and “communications media.” 
         [0057]    “Computer storage media” comprises volatile and non-volatile, removable and non-removable media implemented in any method or technology for storage of information, such as computer readable instructions, data structures, program modules, or other data. Computer storage media may be, for example, and not limitation, RAM  802 , ROM  804 , EEPROM, Flash memory, or other memory technology, CD-ROM, digital versatile disks (DVD), or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage, or other magnetic storage devices, or any other medium which can be used to store the desired information and which can be accessed by a computer. 
         [0058]    “Communication media” typically comprise computer readable instructions, data structures, program modules, or other data in a modulated data signal, such as carrier wave or other transport mechanism. Communication media may also comprise any information delivery media. The term “modulated data signal” means a signal that has one or more of its characteristics set or changed in such a manner as to encode information in the signal. By way of example, and not limitation, communication media comprises wired media such as a wired network or direct-wired connection, and wireless media such as acoustic, RF, infrared, and other wireless media. Combinations of any of the above are also included within the scope of computer readable medium. 
         [0059]    Computing functionality  800  may also comprise an input/output module  812  for receiving various inputs (via input modules  814 ), and for providing various outputs (via one or more output modules). One particular output module mechanism may be a presentation module  816  and an associated GUI  818 . Computing functionality  800  may also include one or more network interfaces  820  for exchanging data with other devices via one or more communication conduits  822 . In some embodiments, one or more communication buses  824  communicatively couple the above-described components together. 
         [0060]    Communication conduit(s)  822  may be implemented in any manner (e.g., by a local area network, a wide area network (e.g., the Internet), and the like, or any combination thereof). Communication conduit(s)  822  may include any combination of hardwired links, wireless links, routers, gateway functionality, name servers, and the like, governed by any protocol or combination of protocols. 
         [0061]    Alternatively, or in addition, any of the functions described herein may be performed, at least in part, by one or more hardware logic components. For example, without limitation, illustrative types of hardware logic components that may be used include Field-programmable Gate Arrays (FPGAs), Application-specific Integrated Circuits (ASICs), Application-specific Standard Products (ASSPs), System-on-a-chip systems (SOCs), Complex Programmable Logic Devices (CPLDs), and the like. 
         [0062]    The terms “module” and “component” as used herein generally represent software, firmware, hardware, or combinations thereof. In the case of a software implementation, the module or component represents program code that performs specified tasks when executed on a processor. The program code may be stored in one or more computer readable memory devices. The features of the present disclosure described herein are platform-independent, meaning that the techniques can be implemented on a variety of commercial computing platforms having a variety of processors (e.g., set-top box, desktop, laptop, notebook, tablet computer, personal digital assistant (PDA), mobile telephone, smart telephone, gaming console, and the like). 
         [0063]    While various aspects of the present disclosure have been described above, it should be understood that they have been presented by way of example and not limitation. It will be apparent to persons skilled in the relevant art(s) that various changes in form and detail can be made therein without departing from the spirit and scope of the present disclosure. Thus, the present disclosure should not be limited by any of the above described exemplary aspects, but should be defined only in accordance with the following claims and their equivalents. 
         [0064]    In addition, it should be understood that the figures in the attachments, which highlight the structure, methodology, functionality and advantages of the present disclosure, are presented for example purposes only. The present disclosure is sufficiently flexible and configurable, such that it may be implemented in ways other than that shown in the accompanying figures (e.g., implementation within computing devices and environments other than those mentioned herein, implementation utilizing other additive manufacturing devices). As will be appreciated by those skilled in the relevant art(s) after reading the description herein, certain features from different aspects of the systems, methods and computer program products of the present disclosure may be combined to form yet new aspects of the present disclosure. 
         [0065]    Further, the purpose of the foregoing Abstract is to enable the U.S. Patent and Trademark Office and the public generally and especially the scientists, engineers and practitioners in the relevant art(s) who are not familiar with patent or legal terms or phraseology, to determine quickly from a cursory inspection the nature and essence of this technical disclosure. The Abstract is not intended to be limiting as to the scope of the present disclosure in any way.