Patent Publication Number: US-2023136313-A1

Title: 3d printing system

Description:
FIELD OF THE INVENTION 
     The present invention relates to additive manufacturing systems in which a photo-sensitive resin within a tank is cured through exposure to radiation when fabricating an object, and in particular to a spill tray for containing resin that leaks from a bottom of the tank and a replaceable mask that can be installed without the use of cables or ribbons. 
     BACKGROUND 
     While many advancements have been made in the field of 3D printing, certain challenges have not been sufficiently addressed. These challenges include resin that inadvertently leaks out from the bottom of the tank, as well as the cumbersome nature of installing a liquid crystal display (LCD) mask which typically involves the connection of cables or ribbons. Solutions to such challenges are described herein. 
     SUMMARY OF THE INVENTION 
     In accordance with one embodiment of the invention, a 3D printing system may include a tank in which a bottom of the tank is formed by a radiation-transparent flexible membrane, a spill tray with an outer wall configured to contain photo-curable liquid resin that leaks out from the bottom of the tank, and a light source configured to project radiation towards the bottom of the tank. The spill tray may contain an inner opening that allows the radiation from the light source to pass through the spill tray to the tank. An elevation of a bottom surface of the spill tray may be lower than an elevation of the radiation-transparent flexible membrane so that resin that leaks from the tank flows downwards into the spill tray. 
     In accordance with another embodiment of the invention, a 3D printing system may include a tank in which a bottom of the tank is formed by a radiation-transparent flexible membrane, a light source configured to project radiation towards the bottom of the tank, a mask assembly (disposed between the tank and the light source) that comprises a mask with pixels configurable to be individually transparent or opaque to portions of the radiation projected from the light source, and a mask assembly receiving member configured to receive the mask assembly. The mask assembly may also include a rigid guide portion that is insertable into a slot of the mask assembly receiving member. An end of the rigid guide portion may comprise an electrical connector with a male coupling that is paired with an electrical connector (mounted on a housing of the light source) with a female coupling. Conveniently, the mating of the male and female couplings of the electrical connectors may be performed simultaneously with the insertion of the rigid guide portion of the mask assembly into the slot of the mask assembly receiving member without the need to manually manipulate cables and/or ribbons. 
     These and other embodiments of the invention are more fully described in association with the drawings below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    depicts a schematic cross-section of a 3D printing system in which an object undergoes fabrication in a tank containing a photo-curable liquid resin, in accordance with one embodiment of the invention. 
         FIG.  2    depicts a perspective view of certain components of the 3D printing system including a tank for containing resin, a spill tray surrounding the tank, the housing of a light source and a gravity-assisted resin dispenser, in accordance with one embodiment of the invention. 
         FIG.  3    depicts a perspective view of certain components of the 3D printing system, in which the tank is shown spaced apart from the 3D printing system so as to show the mask assembly disposed underneath the tank, in accordance with one embodiment of the invention. 
         FIGS.  4 A- 4 C  depict a series of perspective views in which the mask assembly is progressively separated from the 3D printing system so as to show the mask assembly receiving member, central opening of the spill tray, and light source disposed underneath the mask assembly, in accordance with one embodiment of the invention. 
         FIGS.  5 A- 5 C  depict perspective views showing the alignment and mating of two electrical connectors, in accordance with one embodiment of the invention. 
         FIGS.  6 A- 6 B  depict perspective views showing the insertion of a resin cartridge into the gravity-assisted resin dispenser through an opening in the housing of the 3D printing system, in accordance with one embodiment of the invention. 
         FIG.  7    depicts an enlarged perspective view of certain components of the 3D printing system, including the extraction plate, height adjustment mechanism, gravity-assisted resin dispenser, and level detector, in accordance with one embodiment of the invention. 
         FIG.  8    depicts an enlarged perspective view of the resin receptacle that is mounted on the tank, in accordance with one embodiment of the invention. 
         FIG.  9    depicts an enlarged perspective view of the level detector of the tank, in accordance with one embodiment of the invention. 
         FIG.  10    depicts components of a computer system in which computer readable instructions instantiating the methods of the present invention may be stored and executed. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration specific embodiments in which the invention may be practiced. It is understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention. Descriptions associated with any one of the figures may be applied to different figures containing like or similar components/steps. 
       FIG.  1    depicts a cross-section of a three-dimensional (3D) printing system  100  (also called a vat polymerization printer), in which electromagnetic radiation  56  (e.g., ultra-violet light) is used to cure photo-curable liquid resin  94  in order to fabricate an object  98  (e.g., a 3D object). The object  98  may be fabricated layer by layer; that is, a new layer of the object  98  may be formed by photo-curing a layer  96  of liquid resin  94  adjacent to the bottom surface of the object  98  (also called the build area), the object  98  may be raised by an extractor plate  72 , allowing a new layer of liquid resin  96  to be drawn under the newly formed layer; and the process repeated to form additional layers. 
     The 3D printing system  100  includes a tank  10  for containing the liquid resin  94 . The sides of the tank  10  may be formed by tank sidewalls  14 , and the bottom of the tank  10  may be formed by a radiation-transparent flexible membrane  12  that allows radiation  56  from a light source  54  to enter into the tank  10 . The light source  54  may comprise a light emitting diode (LED) array or another light source such as a digital light processor (DLP) light projector. A mask  22  may be disposed between the bottom of the tank  10  and the light source  54  to spatially filter the radiation  56  that is incident on layer  96 , so that specific regions of the liquid resin  94 , that correspond to the cross section of the object  98  being printed, are cured. Mask  22  may be a transmissive spatial light modulator, such as a liquid crystal display (LCD) with a two-dimensional array of addressable pixels. More specifically, the LCD may be a high resolution  4   k  monochrome 9.3 inch LCD with a pixel size of 53 microns. Certain ones of the pixels may be controlled to be transparent, while others may be controlled to be opaque. Transparent pixels allow radiation  56  to pass through the mask  22  at certain spatial locations of the mask  22  and into the tank  10 , consequently curing portions of the liquid resin  94 , while opaque pixels prevent radiation  56  from passing through certain spatial locations of mask  22 . In addition to an LCD, mask  22  may include other optical elements, such as optical diffusers, collimation films, polarizers, etc. In an embodiment where the light source  54  is a DLP light projector, mask  22  is optional (since the image may be formed by the DLP light projector instead of the LCD), in which case, mask  22  may be replaced by a plane of glass (not depicted). 
     One challenge faced by 3D printing systems of the present kind is that in addition to adhering to the object  98 , newly formed layers tend to adhere to the bottom of the tank  10 . Consequently, when the extraction plate  72  to which the object  98  is attached is raised by the height adjustor  74 , the newly formed layer could tear and/or become dissociated from the object  98 . To address this issue, a flexible membrane  12  may be used to form the bottom of the tank  10 . Flexible membrane  12  may be formed of silicone or another material, and optionally, coated with a non-stick material such as polytetrafluoroethylene (PTFE) to reduce the likelihood for the newly formed layer to adhere to the bottom of tank  10 . The flexible membrane  14  is transparent (or nearly so) to the wavelength of radiation emitted by the light source  54  so as to allow the radiation  56  to enter into the tank  10  and cure the liquid resin  94 . 
     The printing operations may be automated by a controller  90 , which may be communicatively coupled to the light source  54 , the mask  22 , and the height adjustor  74  via control signal paths  92   a ,  92   b  and  92   c , respectively (e.g., electrical signal paths). The controller  90  may control the addressable pixels of the mask  22  such that the transparent pixels of the mask  22  correspond to a cross section of an object to be printed. The controller  90  may control the light source  54  to turn on only when the resin  94  needs to be cured so as to minimize the heating of the mask  22  (which in turn minimizes the heating of the resin  94 ). Further, the controller  50  may control the height adjustor  74  to control the vertical position of the height extractor  72 , and consequently of the object (or partially formed object)  98  that is affixed to the height extractor  72 . Using the height extractor  74 , the position of the object  98  may be translated in a direction perpendicular to an extent of the flexible membrane  12 . 
       FIG.  2    depicts a perspective view of certain components of the 3D printing system  100  including the tank  10  for containing resin (the resin not depicted in  FIG.  2    for clarity), a spill tray  40  surrounding the tank  10  for containing any resin that leaks out from the bottom of the tank  10 , the housing  50  of the light source (the light source not visible in  FIG.  2   ) and a gravity-assisted resin dispenser for replenishing the resin in the tank  10  and maintaining a constant level of the resin. The gravity-assisted resin dispenser may include a resin cartridge  60  for supplying resin to the tank  10 , and a cartridge holder  64  that positions an opening of the resin cartridge  60  within a resin receptacle  16 . The resin receptacle  16  receives resin that is dispensed from the resin cartridge  60  and transfers that resin into the tank  10 . In principle, the gravity-assisted resin dispenser operates similarly to a pet water dispenser. Resin that is dispensed from the resin cartridge  60  fills the tank  10 , and keeps filling the tank  10  until the resin in the tank  10  reaches a certain predetermined fill level. At that fill level, the vacuum that has built up inside of the resin cartridge  60  is sufficient to prevent any additional resin from being released from the resin cartridge  60 . When the resin in the tank  10  is depleted below this fill level (i.e., as a result of printing operations), air flows into the resin cartridge  60  through an air conduit  17  (depicted in  FIG.  8   ). Such air reduces the vacuum inside of the resin cartridge  60 , allowing an additional volume of resin to be dispensed from the resin cartridge  60  until the resin in the tank  10  again reaches the predetermined fill level. As shown in  FIG.  2   , the resin cartridge  60  may include a handle  62  for a human operator to easily grasp the top of the resin cartridge  60  (e.g., to carry the resin cartridge  60 , pull the resin cartridge  60  out of the cartridge holder  64 , etc.). 
     One problem occasionally encountered in 3D printing systems is resin leaking out from the bottom of the tank  10 . For example, a tear or perforation in radiation-transparent flexible membrane  12  may cause resin to leak out from the bottom of the tank  10 . In prior system, such leak may occur during a time the 3D printing system is in use and not being monitored by a human operator (e.g., middle of the night), resulting in a messy cleanup situation for the operator. In one embodiment of the present invention, a spill tray  40  is provided to contain any resin that leaks out from the bottom of the tank  10 . In a preferred embodiment, the volume of the spill tray  40  may be equal or greater than the volume of the resin cartridge  60  such that in the worst case that the resin from a full resin cartridge  60  leaks out from the bottom of the tank  10 , all of the leaked resin would be safely contained within the spill tray  40 . While cleanup of the leaked resin in the spill tray  40  would still be necessary (e.g., using a suction apparatus), at least the leaked resin is contained in an easily accessible and easy to clean location, rather than being leaked into other areas of the printer (e.g., light source, floor of printer housing) that could result in damage to the printer or outside of the printer (e.g., onto the floor, carpet, etc.). As shown, the spill tray  40  may be disposed on top of a housing  50  that encloses the light source (the light source not visible in  FIG.  2   ). It is also possible for the spill tray  40  to be removable, so that the spilled resin can be cleaned up by removing the spill tray  40  from the 3D printing system  100  and pouring the spilled resin from the spill tray  40  into a container. Additional features of the spill tray  40  will be described in connection with the subsequent figures. 
     The tank  10  may include four (rigid) sidewalls  14  that surround the inner cavity of the tank  10 , and a radiation-transparent flexible membrane  12  that forms the bottom of the tank  10 . The sidewalls  14  of the tank may form a rectangular frame that stretches the radiation-transparent flexible membrane  12  in a direction perpendicular to an extent of the radiation-transparent flexible membrane  12  so as to create tension in the transparent flexible membrane  12 . The tank  10  may include a cove  18  that is fluidly connected to the inner cavity of the tank  10 . As will be further described in connection with  FIG.  6 A , the level of resin in cove  18  may be monitored by a level detector  86  so as to monitor the level of resin within the tank  10 . As will also be more clearly depicted in the figures to follow, the tank  10  may rest on a mask assembly  20 , which in turn may be secured to a mask assembly receiving member  30 . A mount  70  is used to secure a height adjustment mechanism (not depicted in  FIG.  2   , but is depicted in  FIGS.  6 A-B  and  7 ). 
       FIG.  3    shows how the tank  10  can be conveniently removed and attached to the 3D printing system using a magnetic attachment mechanism. Four magnets ( 19   a ,  19   b ,  19   c ,  19   d ) disposed on a bottom surface of the tank  10  may be attracted to four magnetic posts ( 32   a ,  32   b ,  32   c ,  32   d ) disposed on the surface of the spill tray  40 , allowing the tank  10  to be clamped to the 3D printing system (during the installation of the tank), and subsequently removed from the 3D printing system. Further, due to the automatic alignment of the four magnets ( 19   a ,  19   b ,  19   c ,  19   d ) to the four magnetic posts ( 32   a ,  32   b ,  32   c ,  32   d ), the tank  10  and the mask  22  (e.g., LCD) of the mask assembly  20  are automatically aligned with respect to one another. It is understood that in other embodiments (not depicted), a different number of magnets may be employed. Further, it is understood that some of the elements referred to herein as “magnets” may instead be composed of ferromagnetic materials such as iron, nickel and cobalt. 
     As is more clearly visible in  FIG.  3   , the spill tray  40  may comprise an outer wall  42  and an inner wall that is formed by a stacked arrangement of the mask assembly  20  and the mask assembly receiving member  30 . The outer wall  42  and the inner wall may be oriented in a direction that is substantially perpendicular to the bottom surface  44  of the spill tray  40 . Further, the elevation of the bottom surface  44  of the spill tray  40  may be lower than the elevation of the bottom of the tank  10  (i.e., the flexible membrane  12 ), allowing any resin that leaks out from the tank  10  to flow downwards into the spill tray  40 . In another embodiment (not depicted), the bottom surface  44  of the spill tray  40  may be a non-planar (e.g., curved) surface, causing the spilled resin (at least initially) to flow towards one or more depressions disposed on the bottom of the spill tray  40 . In another embodiment (not depicted), the bottom surface of the spill tray  40  may include a drain that is fluidly connected to a container (i.e., that is distinct from the resin cartridge  60 ), such that the spilled resin flows out of the spill tray  40  into the container. In such an embodiment, the spill tray  40  may be more appropriately called a funnel, as the function of the spill tray  40  would be to funnel the spilled resin into the container that is connected to the drain of the spill tray  40 . The mask assembly  20  is also more clearly visible in  FIG.  3   , and includes a mask  22  that is secured within a frame  24 . 
       FIGS.  4 A- 4 C  show how the mask assembly  20  can be conveniently removed from the mask assembly receiving member  30  of the 3D printing system. First, four screws ( 25   a ,  25   b ,  25   c ,  25   d ) may be unscrewed from the surface of the mask assembly  20 . Then, the mask assembly  20  may be pulled apart from the mask assembly receiving member  30  by separating the four ring members ( 26   a ,  26   b ,  26   c  and  26   d ) from the four magnetic posts ( 32   a ,  32   b ,  32   c ,  32   d ) of the mask assembly receiving member  30 . For clarity, it is noted that the four ring members ( 26   a ,  26   b ,  26   c  and  26   d ) and frame  24  of the mask assembly  20  may be made from a material that is neither attracted to nor repelled by the four magnetic posts ( 32   a ,  32   b ,  32   c ,  32   d ), such as plastic or fiber glass. 
     The reverse process may be performed to install the mask assembly  20 . First, the four ring members ( 26   a ,  26   b ,  26   c  and  26   d ) of the mask assembly  20  may be inserted over the four magnetic posts ( 32   a ,  32   b ,  32   c ,  32   d ) of the mask assembly receiving member  30 . At the same time, a rigid guide member  27  of the mask assembly  20  may be inserted into a slot  34  of the mask assembly receiving member  30 . The alignment of the rigid guide member  27  with respect to the slot  34  and the alignment of the four ring members ( 26   a ,  26   b ,  26   c  and  26   d ) with respect to the four magnetic posts ( 32   a ,  32   b ,  32   c ,  32   d ) may automatically align four screw holes ( 29   a ,  29   b ,  29   c ,  29   d ) of the mask assembly  20  with four screw holes ( 35   a ,  35   b ,  35   c ,  35   d ) of the mask assembly receiving member  30 . Finally, four screws ( 25   a ,  25   b ,  25   c ,  25   d ) may be used to secure the mask assembly  20  to the mask assembly receiving member  30 . While four screws have been described, it is understood that other embodiment may utilize a greater or fewer number of screws, or no screws at all. For example, the screws could be replaced with pegs and/or the mask assembly  20  could have a tongue on its bottom surface that fits into a groove on the top surface of the mask assembly receiving member  30 . The cable- (ribbon-) free electrical connection between the mask assembly  20  and the mask assembly receiving member  30  will be explained below in connection with  FIGS.  5 A- 5 C . 
     In one embodiment, the mask assembly  20  may be regarded as a “replaceable modular LCD.” That is, when the mask assembly  20  reaches the end of its lifetime or fails for some reason, a new mask assembly  20  may be ordered, the old mask assembly  20  may be removed and the new mask assembly  20  may be installed, in accordance with the above description. In another embodiment, the frame  24  of the mask assembly  20  may be reused and only the mask  22  may be replaced. 
     As shown in  FIG.  4 C , removal of the mask assembly  20  exposes the light source  54  that is located within the light source housing  50 . More specifically, what is visible in  FIG.  4 C  is an array of lenses of a light emitting diode (LED) array. In other embodiments, the light source  54  may instead be a digital light projector (DLP) light source or other light source. A fan  52  secured to the housing  50  may be used cool the light source  54  (as needed). Also visible in  FIG.  4 C  is the central opening  46  of the spill tray  40  through which radiation from the light source  54  passes through to reach the tank  10 . It is noted that the seal between the mask assembly receiving member  30  and the spill tray  40  is fluid tight so as to prevent any of the spilled resin from leaking into the light housing  50  through the central opening  46  of the spill tray  40 . It is further noted that the light source  54  may be serviced and maintained through the central opening  46  of the spill tray  40 . 
       FIGS.  5 A- 5 C  depict the cable- (ribbon-) free electrical connection mechanism between the mask assembly  20  and the mask assembly receiving member  30  in greater detail. An electrical connector  28  (e.g., a high-definition multimedia interface (HDMI) connector, a mobile industry processor interface (MIPI) connector, a digital visual interface (DVI) connector, a DisplayPort (DP) connector, a low-voltage differential signalling (LVDS) connector, etc.) of the mask assembly  20  may be disposed on an end of the rigid guide member  27  of the mask assembly  20 , and be paired with a matching electrical connector  36  that is mounted on a support bracket  38 . For clarity, the support bracket  38  is depicted in a standalone form, but it is understood that such support bracket  38  is fixedly mounted within (or partially within) the light source housing  50 . Importantly, installing the mask assembly  20  on the mask assembly receiving member  30  (in accordance with the above-described process) automatically causes the electrical connector  28  to be mated with the electrical connector  36  without the need to manually manipulate electrical cables or ribbons (as commonly takes place in prior solutions). Likewise, the removal of the mask assembly  20  from the mask assembly receiving member  30  (in accordance with the above-described process) automatically causes the electrical connector  28  to be disconnected from the electrical connector  36  without the need to manually manipulate electrical cables or ribbons (as commonly takes place in prior solutions). In the particular embodiment depicted in  FIGS.  5 A- 5 C , electrical connector  28  is a male coupling and electrical connector  36  is a female coupling, but it is understood that the reverse may be true in other embodiments (i.e., electrical connector  28  may be a female coupling and electrical connector  36  may be a male coupling). 
       FIGS.  6 A- 6 B  depict the above-described printer components and other components being disposed within a printer housing  80 . Such components are depicted in an enlarged view in  FIG.  7    (without the printer housing  80 ) for clarity. The inside of the printer housing  80  may be accessible through a door  84  that is mounted on a side panel of the printer housing  80  by way of a pair of hinges. While the tank  10 , mask assembly  20  (not clearly visible in  FIG.  6 A ) and the final printed object (not depicted in  FIG.  6 A ) may be accessed through the door opening, a separate opening  82  may be used to insert (and remove) of the resin cartridge  60  into (from) the cartridge holder  64 . Also visible in  FIG.  6 A  is the above-described extractor plate  72  and the height adjustment mechanism  74 . 
     A resin level detector  86  may be disposed above cove  18  to monitor the level of resin in the tank  10 . In one embodiment, the resin level detector  86  may transmit a pulse of energy (e.g., laser pulse, ultrasonic pulse) that is reflected off of the surface of the resin in cove  18 , and such reflected pulse of energy is then detected by resin level detector  86 . The round trip time of the energy pulse may be measured and converted into a distance using the speed at which the energy pulse travels. Finally, such distance may be used to estimate the level of the resin in the cove  18 , and accordingly the level of resin in the tank  10 . For increased clarity, the level detector  86  and cove  18  are depicted in a magnified view in  FIG.  9    below. Using the level detector  86 , the 3D printer system  100  may track the resin level in the tank  10  and start a printing job automatically once the resin level reaches a predetermined level. Accordingly, the user can start his/her print job and walk away knowing that the printing job is being monitored. 
       FIG.  8    depicts an enlarged view of the resin receptacle  16  that is mounted on a side of the tank  10 . The resin receptacle  16  may contain an air conduit  17  that is inserted into the (bottom) opening of the resin cartridge  60  (shown decoupled from the resin receptacle  16  in  FIG.  8   ). As described above, the buildup of vacuum within the resin cartridge  60  may cause air to flow into the resin cartridge  60  through air conduit  17 . Resin that flows out of the resin cartridge  60  may flow into the cavity of tank  10  through one or more holes  15  disposed on a bottom surface of the resin receptacle  16 . 
     As is apparent from the foregoing discussion, aspects of the present invention involve the use of various computer systems and computer readable storage media having computer-readable instructions stored thereon.  FIG.  10    provides an example of a system  200  that may be representative of any of the computing systems (e.g., controller  90 ) discussed herein. Examples of system  200  may include a smartphone, a desktop, a laptop, a mainframe computer, an embedded system, etc. Note, not all of the various computer systems have all of the features of system  200 . For example, certain ones of the computer systems discussed above may not include a display inasmuch as the display function may be provided by a client computer communicatively coupled to the computer system or a display function may be unnecessary. Such details are not critical to the present invention. 
     System  200  includes a bus  202  or other communication mechanism for communicating information, and a processor  204  coupled with the bus  202  for processing information. Computer system  200  also includes a main memory  206 , such as a random access memory (RAM) or other dynamic storage device, coupled to the bus  202  for storing information and instructions to be executed by processor  204 . Main memory  206  also may be used for storing temporary variables or other intermediate information during execution of instructions to be executed by processor  204 . Computer system  200  further includes a read only memory (ROM)  208  or other static storage device coupled to the bus  202  for storing static information and instructions for the processor  204 . A storage device  210 , for example a hard disk, flash memory-based storage medium, or other storage medium from which processor  204  can read, is provided and coupled to the bus  202  for storing information and instructions (e.g., operating systems, applications programs and the like). 
     Computer system  200  may be coupled via the bus  202  to a display  212 , such as a flat panel display, for displaying information to a computer user. An input device  214 , such as a keyboard including alphanumeric and other keys, may be coupled to the bus  202  for communicating information and command selections to the processor  204 . Another type of user input device is cursor control device  216 , such as a mouse, a trackpad, or similar input device for communicating direction information and command selections to processor  204  and for controlling cursor movement on the display  212 . Other user interface devices, such as microphones, speakers, etc. are not shown in detail but may be involved with the receipt of user input and/or presentation of output. 
     The processes referred to herein may be implemented by processor  204  executing appropriate sequences of computer-readable instructions contained in main memory  206 . Such instructions may be read into main memory  206  from another computer-readable medium, such as storage device  210 , and execution of the sequences of instructions contained in the main memory  206  causes the processor  204  to perform the associated actions. In alternative embodiments, hard-wired circuitry or firmware-controlled processing units may be used in place of or in combination with processor  204  and its associated computer software instructions to implement the invention. The computer-readable instructions may be rendered in any computer language. 
     In general, all of the above process descriptions are meant to encompass any series of logical steps performed in a sequence to accomplish a given purpose, which is the hallmark of any computer-executable application. Unless specifically stated otherwise, it should be appreciated that throughout the description of the present invention, use of terms such as “processing”, “computing”, “calculating”, “determining”, “displaying”, “receiving”, “transmitting” or the like, refer to the action and processes of an appropriately programmed computer system, such as computer system  200  or similar electronic computing device, that manipulates and transforms data represented as physical (electronic) quantities within its registers and memories into other data similarly represented as physical quantities within its memories or registers or other such information storage, transmission or display devices. 
     Computer system  200  also includes a communication interface  218  coupled to the bus  202 . Communication interface  218  may provide a two-way data communication channel with a computer network, which provides connectivity to and among the various computer systems discussed above. For example, communication interface  218  may be a local area network (LAN) card to provide a data communication connection to a compatible LAN, which itself is communicatively coupled to the Internet through one or more Internet service provider networks. The precise details of such communication paths are not critical to the present invention. What is important is that computer system  200  can send and receive messages and data through the communication interface  218  and in that way communicate with hosts accessible via the Internet. It is noted that the components of system  200  may be located in a single device or located in a plurality of physically and/or geographically distributed devices. 
     Thus, a 3D printing system has been described. It is to be understood that the above-description is intended to be illustrative, and not restrictive. Many other embodiments will be apparent to those of skill in the art upon reviewing the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. 
     LIST OF REFERENCE NUMERALS 
     
         
           10  Tank (or vat) 
           12  Radiation-transparent flexible membrane 
           14  Tank sidewall 
           15  Holes 
           16  Resin receptacle 
           17  Air conduit 
           18  Cove 
           19   a,b,c,d  Magnets 
           20  Mask assembly 
           22  Mask 
           24  Frame 
           25   a,b,c,d  Screws 
           26   a,b,c,d  Ring members 
           27  Guide member 
           28  Electrical connector 
           29   a,b,c,d  Screw holes 
           30  Mask assembly receiving member 
           32   a,b,c,d  Magnetic posts 
           34  Slot 
           35   a,b,c,d  Screw holes 
           36  Electrical connector 
           38  Support bracket 
           40  Spill tray 
           42  Outerwall of spill tray 
           44  Bottom surface of spill tray 
           46  Central opening of spill tray 
           50  Light source housing 
           52  Light source fan 
           54  Light source 
           56  Electromagnetic radiation 
           60  Resin cartridge 
           62  Cartridge handle 
           64  Cartridge holder 
           70  Mount (height adjustment mechanism mount) 
           72  Extractor plate 
           74  Height adjustment mechanism 
           80  Printer housing 
           82  Opening (resin cartridge insertion hole) 
           84  Printer door 
           86  Resin level detector 
           90  Controller 
           92   a,b,c  Control signal paths 
           94  Resin 
           96  Build Area 
           98  Object 
           100  3D printing system 
           200  Computing system 
           202  Bus 
           204  Processor 
           206  Memory 
           208  ROM 
           210  Storage device 
           212  Display 
           214  Keyboard 
           216  Mouse 
           218  Communication interface