Abstract:
In sterile, additive manufacturing wherein one lamella is successively built upon an underlying lamella until an object is completed, a sterile manufacturing environment is provided. A major chamber large enough to accommodate the manufactured object has sterile accordion pleated sidewalls and a sterile top closed with flap valves. A minor chamber for supporting the nozzles positioned above the major chamber has similar valves in corresponding positions. Nozzles for material deposition penetrate the pair of valves to block air and particles from entry into the major chamber where the nozzles make layer by layer deposition of the object using XY areawise nozzle motion relative to the object as well as Z nozzle vertical motion with the major chamber expanding as the object is formed.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority from provisional application Ser. No. 61/935,844, filed Feb. 5, 2014 for an invention entitled APPLICATIONS AND CONFIGURATION OF DISPOSABLE, STERILE-ENVIRONMENT, ADDITIVE MANUFACTURING CHAMBER AND METHODS OF USAGE by Nathan Maier. 
     
    
     TECHNICAL FIELD 
       [0002]    The invention relates to sterile 3-D manufacturing using layering of 2-D lamellas. 
       BACKGROUND 
       [0003]    Due to increasing popularity and significant technological developments in the field of additive manufacturing, it has become critical to develop an efficient, sterile, and disposable chamber for 3D printing. As physicians, manufacturing professionals, and individuals make more common use of 3D printing systems, there will be a need to print many different types of materials, including tissue, in a sterile chamber which can simply and rapidly be exchanged to allow for printing of diverse materials. An article in New York Times, Jan. 27, 2015 entitled “The Operation Before the Operation”, p. D6, describes a need for anatomical models for medicine and the use of 3D printed models. 
         [0004]    The need for making anatomical models and actual body parts by additive manufacturing was realized many years ago. The state of the art in this field several years ago was summarized in an article entitled “Rapid prototyping techniques for anatomical modeling in medicine” by M. McGurk et al. in Ann. R. Coll. Surg. Engl. 1997; 79; 169-174 wherein 3-D printing of models was described. Models were created by spraying liquid through ink jet printer nozzles on a layer of precursor powder, creating a solid thin slice. The printing process was repeated for each subsequent slice until the object was completed as a “green-state” part that was then fired in a furnace to sinter it. The resulting object was then further treated to make a full density part. 
         [0005]    In recent years the development of software for computer controlled robotic X-Y motion systems used in the semiconductor and optics industries has made 3D printing of large objects easier than in former years. Software programs such as SolidWorks, AutoCad 360, and similar software programs make layered construction of 3D objects a relatively low cost and fast task for 3D printing equipment. 
         [0006]    To achieve 3D printing of larger objects, print nozzles are directed in the X-Y plane either by placing the object to be made on an X-Y table wherein motion is provided below the nozzles, or mounting rails above the nozzles for X-Y motion directed from above the nozzles. An example of an X-Y table for motion below the nozzles is shown in U.S. Pat. No. 5,760,500 to T. Kondo et al. wherein linear actuators or stepper motors provide independent motion to a table over the X-Y plane. Highly accurate stepper motors for this purpose are described in U.S. Pat. No. 7,518,270 to R. Badgerow and T. Lin. A 3-D printer with overhead control of nozzles is described in U.S. Pat. No. 5,740,051 to R. Sanders et al. 
         [0007]    In either motion situation, the nozzles move in the X-Y plane relative to the printed object and also move up in the Z plane starting from a lower level and proceeding upwardly. A layer or lamella is first printed at a low level and then the next layer up is printed and so on until the model or object is completed. Sometimes two nozzles are used, including a first nozzle to spray or extrude a manufacturing material, such as a polymer, and a second nozzle to spray a support fluid for the manufacturing material, which may be soft or viscous. An example of a support fluid may be an ink jet sprayed, ultra violet light cured resin. When the manufacturing material hardens, the faster drying support fluid is dissolved out. The use of chamber or accordion pleated sleeves in glovebox environments is known from U.S. Pat. No. 3,456,812 to J. Gandolfo et al. 
         [0008]    Currently, many researchers, industry professionals, and individuals are looking to additive manufacturing by 3D printing as the future of custom manufacturing of everything from organs to food products. Additive manufacturing provides the flexibility to produce diverse items very rapidly and at much lower cost than many previous manufacturing methodologies. In particular, additive manufacturing technology by 3D printing techniques for patient-specific and potentially patient-derived tissue and bone using tissue and stem cells. An object of the invention was to develop a sterile manufacturing environment compatible for 3D printing equipment that could be used for biological object manufacturing, as well as the validation of effective post-manufacturing sterilization of the manufacturing equipment. 
       SUMMARY 
       [0009]    The above object has been achieved with a disposable, sterile environment additive manufacturing chamber that includes a rigid baseplate with suction or self-adhesive bottom to adhere to the 3D printer base. Relative motion of the printheads with respect to the baseplate is provided during manufacturing, with deflection without dimensional variations. The sterile environment is provided by flexible, accordion-type sides in a major chamber which is sterile on the inside and sealed to the baseplate. The sidewall construction resembles a pleated Chinese lantern. The sidewall construction involves some portion that has qualities of tough filter paper, such as Tyvek, and the rest of which could optionally be transparent or opaque Mylar or nylon or other plastic or paper combination. Tyvek is a registered trademark of the DuPont Company for non-directional, non-woven, high density polyethylene or olefin fibers of diameter in the range of 0.5 to 10 micrometers, bonded together by heat and pressure without binders. The resultant major chamber structure is attached to the baseplate and can be stretched in the x, y, z coordinates as the printing heads move during printing. A flexible, stretchable lid is sealed to the sides to close the chamber. 
         [0010]    A minor chamber is removably fastened to the lid of the major chamber. The minor chamber provides support for the printheads. The minor chamber encloses a printhead support block and need not be much larger than needed for the support block. Both chambers have spatially separated flap valves that are openable at a central print nozzle entry. The set of flap valves are openable one at a time when nozzles penetrate an opening so that air or particles cannot directly enter the major chamber where 3D printing will occur, similar to double doors in a building blocking wind from entry or airlocks on a ship. The lid has 3 or more removable attachment tabs that join the major and minor chambers. The major chamber has sidewall guide straps to keep the lid and sidewall of the major chamber from touching or dragging over the object being manufactured as well as a central attachment port for the manufacturing head to be attached. Quick-detachable and disposable manufacturing head subassemblies and nozzles attach to the non-disposable manufacturing heads of the 3D printer. The heads may include an extrusion head, nozzle and feeders or a sputter/spray jet and nozzle which may contact the material being printed. These parts are disposed after each use. 
         [0011]    In summary, a pair of chambers provides a sterile environment for 3D printing of lamellas. A first major chamber has a sterile interior that provides the manufacturing environment with sealed entry of droplet nozzles while a second minor chamber, atop the first chamber, provides for another sealed entry of the nozzles in a manner so that both entries cannot be open at the same time, blocking air and particles from entry into the major chamber. The nozzles deposit layers of structures under computer control from software models of the structures while the major chamber allows for independent X-Y motion and Z motion of the nozzles. Some examples include chambers for printing tissue, living or dead; tissue substrates such as hydroxyapatite, collagen fibers, proteoglycan, and elastin fibers or biological organs or models of organs within a sterile yet disposable chamber. Similar examples to those described above could be employed with alternative additive manufacturing head types such as sputter manufacturing, plasma deposition, fused deposition modeling (FOM), electron-beam freeform fabrication (EBF3), direct metal laser sintering (OMLS), electron-beam melting (EBM), selective laser melting (SLM), selective heat sintering (SHS), laminated object manufacturing (LOM), stereolithography (SLA), digital light processing (OLP), multi-jet modeling (MJM), etc. Similar examples to those described above could be employed with combinations of material supply heads to combine extruded materials with sputtered/sprayed materials in one chamber. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a front perspective view of a sterile environment for additive manufacturing in accordance with the invention wherein a plurality of nozzles is disposed for entry into the environment. 
           [0013]      FIG. 2  shows the apparatus of  FIG. 1  with the plurality of nozzles entrant into the environment. 
           [0014]      FIG. 3  is a front partial cut-away view of the apparatus of  FIG. 2  showing an X-Y motion table connected thereto. 
           [0015]      FIGS. 4-6  are front plan views showing successive views of nozzle entry into valve sealable entry ports of the apparatus of  FIG. 1 . 
           [0016]      FIG. 7  is a front elevational view of the apparatus of  FIG. 3  in an additive manufacturing start position. 
           [0017]      FIG. 8  is a front plan view of an enlarged portion of an alternate embodiment of the apparatus of  FIG. 3 . 
           [0018]      FIG. 9  is a plan view of another alternate embodiment of the apparatus of  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    With reference to  FIG. 1 , a sterile manufacturing environment  11  is used for additive manufacturing. A principal component is a major chamber  15  that is closed at its bottom by being attached to the work table  17  that is fixedly attached to rails  19 . The major chamber  15  has a sterile interior that is closed at its top by top closure  21 . Chamber  15  is sufficiently large for accommodating a three dimensional object such as a model of a human skull but is sufficiently small to fit within a 3D printer printing chamber. The inside of chamber  15  is sterilized prior to use by any conventional means. The outside of chamber  15  is exposed to the ambient environment and is not sterile. Side straps  23 ,  25 ,  27  and  29  provide lateral X-Y guiding motion to flexible sidewalls of the chamber  15  to track XY motion of printheads  31  and  33 . Note that one or both of the printheads may operate by extrusion of material. For purposes of this patent application, extrusion through a nozzle is considered to be printing. Nozzles  41  and  43 , associated with printheads  31  and  33 , respectively, move in the Z direction, shown by arrows Z, under control of a robotic arm, not shown. Nozzles  41  and  43  move through a nozzle support fixture  53 , particularly nozzle holders  53  and  57 , in the minor chamber  51  atop the top closure of major chamber  15 . The minor chamber  51  is significantly smaller than the major chamber  15 . The major chamber must be able to filter air passing through sidewalls of the chamber for expansion and contraction. 
         [0020]    The work table  17  is mounted to an XY table in the base of manufacturing equipment in a fixed manner in the orientation best applicable to the item being printed. Of critical importance is that the baseplate be restricted from independent X, Y motion, apart from the XY table on which it rests, as well as independent deflection in the Z orientation apart from the previously mentioned Z motion in a robot arm during the printing process to maintain dimensional integrity of the item being printed. Alternatively, the XY motion is provided by overhead rails moving the printheads and no XY table is needed. 
         [0021]    Flexible, accordion-style pleated sides of major chamber  15  resemble a Chinese lantern or an upside-down origami cone with the lantern or cone attached and sealed to the work table to maintain the sterile barrier. The work table  17  is attached to rails that are part of an XY table that provides relative XY motion to the printheads during 3D manufacturing. Sidewalls of the major chamber are moved via clips or elastic straps  23 ,  25 ,  27  and  29  by coordination with the XY table to keep the sides of the major chamber  15  from contacting the printed object during the manufacturing process. To facilitate changes in volume of the chamber, a panel or portion of the side or top would be constructed of accordion pleated Tyvek or equivalent breathable sterile barrier. The entire accordion-style sidewall structure could be constructed of Tyvek or equivalent to provide sufficient breathability. Portions of the sidewall structure could also be constructed of Mylar or nylon to facilitate visual inspection of the item being manufactured during processing. The sidewall structure could be provided with a peelable portion to allow easy access to the printed item once the sterile barrier can be broken for use. 
         [0022]    Additionally, quick-detachable and disposable printheads or disposable material extrusion heads, described below in  FIG. 8 , both called “printheads”  41  and  43  are supplied by supply lines  35  and  37 , whether the supply is liquid to be extruded into the printer or ink-like material to be used for supporting the structure under construction. Electronic control lines  45  and  47  provide signals and power to the printheads in the usual manner. The printheads are joined and sealed to the top of the minor chamber  51  so that a sealable entry of nozzles into the major chamber  15  is aligned with a corresponding position for nozzle sealable entry into the minor chamber  51  as explained below. 
         [0023]    With reference to  FIG. 2 , the printheads  31  and  33  are shown to be engaged with nozzle support  53  in minor chamber  51 . The nozzles, not shown, have passed through the minor chamber  51  and have entered the major chamber  15  prior to printing. Engagement of the printheads  31  and  33  with the nozzle support is in an airtight manner, for example, by use of a gasket. 
         [0024]    In  FIG. 3 , XY motion to the work table  17  is provided by rails  19  sliding in X rail support  39  and driven by a stepper motor or linear actuator. In turn, the X rail support  39  moves in a Y rail support  49  in a manner typical for XY tables. Relative XY motion need not be provided by an XY table below the nozzles but could be provided from above the nozzles, with the work table fixed to a permanent surface. XY table motion is coordinated with the XY strap control guide  59  that pulls on side straps  23 ,  25 ,  27  and  29  to keep sidewalls of the major chamber out of the way of the printheads moving in the Z direction. 
         [0025]    A key feature of the invention is the sequential valving of entry ports for nozzles moving into the major chamber. With reference to  FIG. 4 , a first set of flap valves  61  and  63 , associated with the nozzle support  53  of minor chamber  51  corresponds to expected positions of the nozzles  41  and  43  of the respective printheads  31  and  33 . Flap valve  61  has side pivoting flexing flaps  62  and  64  that are center opening and made of elastomeric material, such as rubber. A downwardly extending nozzle can readily open a flex flap with the flap material adhering to the side of nozzle by its elastomeric property, maintaining a partial seal by friction contact with the nozzle. This partial seal prevents any significant amount of air or particle entry past the flap valve. However, a second set of similar valves  71  and  73  associated with the top closure of major chamber  15  further presents air and particle entry into the major chamber  15  as the valves move down into the major chamber. In  FIG. 5 , the nozzles  41  and  43  are shown to have penetrated through the flap valves  61  and  63  with the flaps  62  and  64  adhering to sidewalls of the nozzles with sliding friction contact. The nozzles are seen approaching the second sealable entry port formed by flap valves  71  and  73 . In  FIG. 6 , the nozzles  41  and  43  are shown to have penetrated through both sets of flap valves including the first set  61  and  63  that form a second valve sealable entry port and the second set  71  and  73  that form a first valve sealable entry port for the major chamber  15 . While two nozzles are shown, it is possible the fewer or more nozzles could be used. 
         [0026]    With reference to  FIG. 7 , the nozzles  41  and  43  are seen to be fully entrant through the first and second valve sealable entry ports and extending through the nozzle support  53  into the minor chamber  51  and the major chamber  15 , shown in a collapsed position. Note that when the entry port of the minor chamber is open as in  FIG. 5  to allow nozzle entry, the entry port of the major chamber is closed. Then as the nozzles enter, the entry port of the minor chamber closes by the flap valve sliding against the entrant nozzles. Then the nozzles push open the entry port of the major valves which is momentarily open until the flaps of the flap valves close by sliding against the entrant nozzles. At no time can both nozzles simultaneously move past both sets of flap valves since entry past the valves is sequential. 
         [0027]    Printing by the nozzles is controlled by a computer, not shown, having software that guides layer-by-layer formation of biological or other lamellas. Material used is supplied through supply lines  35  and  37 . Ultraviolet or infrared lamps, not shown, may be placed on the underside of the top closure of the major chamber for accelerating curing of the lamellas. The material dispensed by the nozzles may be material for forming the desired object or one of the nozzles may carry structural support material. Software guides relative X, Y and Z motion of the nozzles from the shown starting position for printing at coordinates 0, 0, 0. As each XY layer is printed or otherwise formed, Z motion is incrementally increased and straps  23  and  27  are appropriately pulled by strap guide control  59  that is coordinated with the XY table to keep sides of the major chamber out of the way of the nozzles  41  and  43 . As straps are pulled up, sidewalls of the major chamber filter air passing through the sidewalls to equalize pressure inside of the major chamber. Chamber material is selected for the desired quality of filtration. Tyvek material removes most particles yet allows air entry. 
         [0028]    With reference to  FIG. 8 , the major chamber  15  has a top closure  21  with tabs  76 ,  77  and  78  that allow removable joinder of the minor chamber  51  to the major chamber  15 . The minor chamber  51  encloses the nozzle support  53  with nozzle holders  55  and  57  providing mechanical support for nozzles  41  and  43 . Nozzle  43  is connected to printhead  81 . Nozzle  41  is connected to heat sink  89  that serves to dissipate heat from extrusion material tube  85 . Extrusion material tube  85  has an internal filament  87  with an insulative sleeve surrounding the material tube  85  carrying the filament that heats material to be extruded through the extrusion printhead  83 . The extrusion material tube  85  is fed from sterile material supply bin  82 . Filament  87  is fed from a sterile filament supply  84  into the material tube  85 . Both the sterile material and the sterile filament are joined at a union  86  that is Y-shaped. Alternatively, the material tube  85  could be manufactured with an internal filament with the tube extending from the sterile material supply bin to the extrusion printhead. 
         [0029]    The insulative sleeve surrounding the material tube  85  is external to the union  86 . The union supports the outside of the sleeve while the material tube feeds directly into the union. The extrusion printhead  83  contains a motor driven gear  93  that presses against extrusion material tube  85  which, in turn, bears against fixed roller  91 . Gear  93  maintains heated extruded material in a well  95  that forces material into the nozzle  41 . Heat sink  89  rejects excess heat by convection to the atmosphere. Printhead  81  is a conventional inkjet printhead.  FIG. 8  shows dual printheads for dispensing ink and a biological extrudeable material in a side-by-side manner. 
         [0030]    The filament is a resistive heating element, such as a nichrome wire that has a thin insulative coating so that when the wire is coiled, adjacent turns will not short. Only a few turns are stored on the sterile filament supply so that a significant amount of heat is not lost in the supply reel  84  that is energized by a DC voltage from power supply  94 . Most of the filament wraps around the material tube  85  to cause sterile material from the material supply bin  82  to flow. The distal end of the filament contacts well  95  which has a ground contact  96  to complete the heating circuit. 
         [0031]    The material tube  85  and the surrounding sleeve, as well as the extrusion printhead  83 , but not a connected gear driving servomotor, not shown, as well as heat sink  89  with a material well, and nozzle  41  are all disposable. Disposing of the material contacting members maintains the compositional integrity of objects being formed by excluding old material. 
         [0032]    In the alternate embodiment of  FIG. 9 , XY motion to the nozzles  41  and  43  is provided by an X-Y table  66  situated above the nozzles. At the same time, Z motion is provided by Z motion control  68  situated below the work table  17 . Nozzles  41  and  43  are associated with twin material extruders  92  and  94 . The nozzles are shown penetrating a first set of flap valves  71  and  73  in the major chamber  15 . The nozzles also penetrate a second set of flap valves  61  and  63  in the minor chamber  51 . The nozzles are depositing material to form an object O on work table  17  in a layer-by-layer manner. The object O is within a sterile environment protected by the accordion pleated sidewalls of major chamber  15  and the double set of entry valves protecting the entry zone for nozzles  41  and  43  into major chamber  15 . Use of twin extrusion nozzles improves deposition times. 
         [0033]    When an object is completed, nozzles are withdrawn and discarded. The major chamber may removed in a sealed room to protect the manufactured object and then may also be discarded. Before discarding the major chamber, the inside sidewalls of the major chamber may be tested for bacterial or other contamination in order to certify the integrity of the manufactured object. When withdrawing the nozzles, the minor chamber may become contaminated with printing residue. The minor chamber is preferably replaced, together with the nozzle support, at the same time as the major chamber.