Abstract:
A system, apparatus, and method that increases the throughput and output fidelity of a three-dimensional printer by providing a temperature controlled build platform that binds to viscous materials which the three-dimensional printer deposits on the build platform during the fabrication process and subsequently releases the finished product when the build platform is sufficiently cooled. The system provides computer controlled electronic means to modify the temperature gradient of the build platform variably during the build process to assure the quality and fidelity of a printed part produced by the three dimensional printer. The temperature control apparatus includes a set of thermoelectric cells that heat and cool portions of the build plate under software control. The temperature control apparatus also provides conductive materials including a plurality of heat pipes and a plurality of radiative devices that efficiently conduct heat to and from the build plate.

Description:
FIELD OF THE INVENTION 
       [0001]    A system that increases the throughput and output fidelity of a three-dimensional printer by providing a temperature controlled multifunctional build platform. 
       BACKGROUND OF THE INVENTION 
       [0002]    There are a wide variety of three-dimensional printers that rely on a variety of technologies to fabricate products that may include plastic parts, food products, and living tissue. The range of available technologies that three-dimensional printers use include: fused deposition modeling, stereo-lithography, selective laser sintering, selective laser melting, electronic beam melting, laminated object manufacturing as well as other technologies that may come into existence. Three-dimensional printers often include build plates that are used to support a work-in-process while the three-dimensional printer fabricates a desired object. 
         [0003]    As an example: A variety of three-dimensional printers produce three-dimensional objects by extruding certain viscous materials. The materials may include thermoplastics; thermoplastic compositions; compounds that are embedded into thermoplastics; amalgams of thermoplastics and embedded compounds; thermoplastics that are doped with powders, dyes, and other substances; along with other materials that may exist or come into existence. 
         [0004]    Another example of the technology includes three-dimensional printers that produce processed products from food-stuffs that may be suitable for human consumption. Three-dimensional printers may also be adapted to produce living tissue that may be used to replace living body parts. 
         [0005]    Many types of three-dimensional printers rely on build plates to support a work-in-process during the fabrication process of the three-dimensional printer. Build-plates are often passive elements that do not actively contribute to the build process and may create obstacles to efficient utilization of a three-dimensional printer. 
         [0006]    As an example of the issues related to the build plate: A three-dimensional printer may produce three-dimensional objects by extruding molten thermoplastic and depositing successive layers of the molten thermoplastic sequentially and orthogonally up from the build plate. The initial layers of molten thermoplastic exiting from the printer&#39;s extruder or print head that are applied directly onto the build plate may not adhere to the build plate, and the work-in-process may remain attached to the moving extruder tip of the printer and slide the work-in-process around the build plate causing misalignment of the successive layers of molten thermoplastic resulting in failure of the finished product. 
         [0007]    During the build process, a work-in-process object may also warp, curl, or creep due to non-uniform cooling of the molten thermoplastic of the object being printed. As the extruded molten thermoplastic cools and hardens, it shrinks slightly. When a the thermoplastic printed object does not shrink uniformly as it cools and sets, the resulting finished printed part may be warped and unusable. Damage to the finished part is commonly evidenced by corners of the printed part lifting off of the build plate or platform. 
         [0008]    Upon completion of the build cycle, another problem may arise when removing the finished object from the build plate. It may be difficult to efficiently remove the finished object from the build plate of the 3-D printer because the printed object may remain adhered to the build plate often requiring the use of a knife or scraper to remove the printed object, which is both time consuming and hazardous to the finished product, the build plate, and the printer operator. 
         [0009]    Three-dimensional printers may also provide multiple print heads utilizing multiple materials that result in more complex printed objects having thermal properties that vary throughout the finished object. In some instances, the fine temperature gradient management of the build plate is insufficient resulting in nonconforming products. 
         [0010]    Build plates are typically composed of metal, plastic or glass that are not usually an effective build surface for a printed object and require enhancements to function efficiently. Modifications to enhance the performance of metal build surfaces include the application of polymide tape, blue painter&#39;s tape or other manually applied materials that the molten thermoplastic will adhere to but still permit manual removal of the finished product. Glass build plates may be enhanced in the same manner as metal build plates by the use of diluted polyvinyl acetate glue or certain hair sprays that may be dissolved when the printed product is completed. Applying enhancemens to the build plate is a manual process that requires time consuming effort and often prevents the use of three dimensional printers in automated processes. Eliminating the need for enhancements would significantly improve the efficiency of a three-dimensional printer and expand its utility to more automated processes. 
         [0011]    Controlling the build plate temperature aids in addressing product warping. A heated build platform improves printing quality by helping to prevent warping that may occur as the molten thermoplastic cools during the build process. A heated build plate keeps the printed object warm during the printing process and permits more uniform shrinking of the thermoplastic product as it cools below its melting point. Heated beds usually yield higher quality finished builds with materials such as ABS and PLA. A heated build plate may also allow 3-D printer operators to print objects without rafts. Existing build plates, however, are designed to achieve a uniform temperature across the surface of the build plate, which may not produce the optimum quality build possible. The composition and geometry of a work in process may require a varying temperature gradient across the build plate. 
         [0012]    Heating a build plate may also cause the build plate itself to warp damaging or reducing the quality of the completed part. 
         [0013]    Flexible synthetic build plates have also been developed that provide a medium that adheres to molten thermoplastic. The synthetic build plate is manually inserted onto the standard build plate of a three-dimensional printer before the print process is started. After the printing process is finished, the thermoplastic part is completed and passively cools to an appropriate temperature. The synthetic build plate with the completed part attached is removed from the printer. The printer operator manually bends, twists, or manipulates the synthetic build plate releasing the thermoplastic part from the surface of the synthetic build plate. Manual intervention in the process is time consuming and prevents full automation of part fabrication. 
         [0014]    For food production, the build plate temperature may need to be substantially reduced below the ambient temperature along with other build plate temperature adjustments to aid in efficiently forming the completed product. In the case of living tissue, the build pate may need to remain within a very specific range of temperatures throughout the build process. In other instances, the build plate temperature may need to remain within certain ranges in order for a product to properly set. 
         [0015]    The examples above are only for illustrative purposes and are not intended to be limiting. These and other situations that exist and may come into existence show how the build plate is an obstacle to increasing the throughput and output fidelity of three-dimensional printers. 
         [0016]    The present invention overcomes the limitations of existing build plates by providing a system that controls the temperature of an included multifunctional build plate during and after the fabrication process of a three-dimensional printer. 
       SUMMARY 
       [0017]    A system, apparatus, and method for controlling the temperature of a build platform to enhance the throughput and output fidelity of a three-dimensional printer. One aspect of the invention provides a multifunctional build platform having a first planar surface and a second planar surface on the opposite side of the first surface of the build platform; a plurality of thermoelectric cell attached to the second surface of the build platform and in electronic communication with a temperature controller; a plurality of temperature sensors connected to the build platform and in electronic communication with a temperature controller; a thermal conduction apparatus ; and a temperature controller having means for accepting electronic temperature signals from the temperature sensors, processing the temperature signals and transmitting signals to the thermoelectric cells to control the temperature of the build platform. The mutifunctional build platform adheres to extruded viscous raw materials that a three-dimensional printer applies to the build platform to fabricate finished products. After the build is completed, the system reduces the temperature of the build platform at a controlled rate. Upon reaching the appropriate temperature, the completed object releases itself from the build platform. In other aspects of the invention, the system provides point by point control of the build platform temperature throughout the build process to fulfill the heating and cooling requirements that are specific to the type of product being produced by the three-dimensional printer. 
         [0018]    The system is installed in a three-dimensional printer and replaces the standard build plate of a three-dimensional printer. When an operator initiates a build process in the printer, the electronic controllers of the invention heat or cool the build platform to a predetermined temperature and controls the thermal gradient of the build platform surface during the build process. Upon completion of the build, the electronic controls of the system, modify the temperature of the build platform in accordance with a computer algorithm releasing the finished part. 
         [0019]    To further enhance the throughput and overall safe efficient operation of three-dimensional printers, the system may include routines for preemptive detection and diagnosis of thermoelectric cell performance variances and build platform temperatures that could cause failure of the build process or the finished part. The routines may include a built in self-test that is completed before the three-dimensional printer initiates fabrication of the product. Once fabrication starts, another routine may dynamically monitor thermoelectric cell performance within the scope of external environmental factors, the performance limits of the thermoelectric cells, and the thermal properties of the raw materials that the three-dimensional printer uses to fabricate products. Upon detection of variances that exceed the performance parameters of a specific fabrication job, the system notifies the operator and initiates prophylactic action to protect the three-dimensional printer, the work-in-process, and the printer operator from physical and chemical dangers arising from improper thermal gradients. The electronics and computer controls of the system also compensate for variations in individual thermoelectric cell performance that may arise due to pre-existing variances caused during manufacturing of the thermoelectric cells or resulting from aging or use of the cells in the system for heating and cooling. 
         [0020]    The system provides a plurality of thermoelectric cells that heat and cool the build platform in response to electronic power and signals provided by thermal controllers. Each thermoelectric cell may be controlled separately and independently from the other thermoelectric cells to permit the temperature of each predefined section of the build platform to be determined by a corresponding thermoelectric device. By providing control of the temperature of each zone or section of the build platform, the printer operator has greater control over the quality and fidelity of the finished part produced by the printer. 
         [0021]    Heat transfer to and from the build plate is facilitated by a thermal conduction apparatus that connects to a lower side of the thermoelectric cells and the exterior of the three-dimensional printer. The apparatus provides a base plate that has a first planar surface that securely attaches to the thermoelectric devices on a side of the thermoelectric devices that is on the opposite side of the thermoelectric device to where the thermoelectric devices attach to the build plate. The element is made of metal such as copper or aluminum or another rigid material that provides sufficient thermal conductivity to efficiently transfer heat to and from the thermoelectric devices. There may be at least one water block cooler that uses water or other liquid or a plurality of heat pipes securely attached to a second side of the element on the side opposite to where the thermoelectric devices are attached. The heat pipes connect the base plate to a plurality of radiative elements coupled with the external structure of the three-dimensional printer. The heat pipes may extend out horizontally in a radial pattern or other appropriate geometric pattern from the conductive element to the periphery of the three-dimensional printer. 
         [0022]    The radiative elements are semi-tubular and extend vertically upward from the periphery of the base plate a predefined distance. The radiative elements are made of metal such as copper or aluminum or another rigid material that provides sufficient thermal conductivity to efficiently transfer heat to and from the conductive element. The radiative elements provide a means to efficiently transfer heat to and from the base plate of the invention to the external environment surrounding the three-dimensional printer. The system provides electronic devices and computer software means to monitor the temperature of the build plate and to provide power to the thermoelectric devices that are used to heat and cool the build plate. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]    These and other objects, features, and advantages of the present invention will become apparent from the following detailed description and the appended drawings in which: 
           [0024]      FIG. 1  illustrates a side perspective view of an embodiment of the present invention 
           [0025]      FIG. 2  illustrates the prior art, which is a side view of the three-dimensional printer without the physical components of the present invention. 
           [0026]      FIG. 3  illustrates a side view of a three-dimensional printer with an embodiment of the present invention shown in  FIG. 1  installed in the three dimensional printer. 
           [0027]      FIG. 4  illustrates a side view of an embodiment of the present invention shown in  FIG. 1 . 
           [0028]      FIG. 5  illustrates an exploded side perspective view of the physical components of an aspect of the invention shown in  FIG. 1  showing a build platform, thermoelectric cells, a base plate, heat pipes, and radiative elements that are components of an aspect of the invention as shown in  FIG. 1 . 
           [0029]      FIG. 6  illustrates an inverted exploded side perspective view of the physical components of an aspect of the invention shown in  FIG. 1  showing a heat pipes, radiative elements, a base plate, thermoelectric cells, and a build platform that are components of an aspect of the invention as shown in  FIG. 1 . 
           [0030]      FIG. 7  illustrates a top view of a build platform, which is a component of an embodiment of the invention shown in  FIG. 1 . 
           [0031]      FIG. 8 . illustrates a top view of an alternative build platform, which is a component of an alternate embodiment of the invention shown in  FIG. 1 . 
           [0032]      FIG. 9  illustrates a bottom view of a build platform for an embodiment of the invention shown in  FIG. 1  showing a possible electric circuit bonded to or etched on the bottom surface of the build plate and adapted for installation of thermoelectric cells that are a component of the invention. 
           [0033]      FIG. 10  illustrates a bottom view of the build plate shown in  FIG. 9  coupled with thermoelectric cells that are connected to the electric circuit on the bottom surface of the build plate and are a component of the invention shown in  FIG. 1 . 
           [0034]      FIG. 11  illustrates a schematic representation of an aspect of the invention shown in  FIG. 1 . 
           [0035]      FIG. 12  illustrates a flowchart representation for an aspect of the invention shown in  FIG. 1  showing the system process for controlling a uniform thermal gradient across the surface of the build plate component of the invention. 
           [0036]      FIG. 13  illustrates a bottom view of an alternative build plate coupled with thermoelectric cells connected to an alternative circuit for an alternative embodiment of the invention shown in  FIG. 1  that are a component of the invention. 
           [0037]      FIG. 14  illustrates a bottom view of an alternative build plate for an alternative embodiment of the invention shown in  FIG. 1  showing a possible electric circuit adapted to be coupled with thermoelectric cells that are a component of the invention. 
           [0038]      FIG. 15  illustrates is a bottom view of an alternative build plate for an alternative embodiment of the invention shown in  FIG. 1  showing the alternative build plate coupled with thermoelectric devices that are a component of the invention. 
           [0039]      FIG. 16  illustrates a schematic representation of an alternative aspect of the invention shown in  FIG. 1 . 
           [0040]      FIG. 17  illustrates a flowchart representation for an aspect of an alternative embodiment of the invention shown in  FIG. 1  made in conformance with the schematic diagram of  FIG. 16  showing the system process for controlling a variable thermal gradient of the surface of a build plate component of the system. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0041]    The embodiments of the invention disclosed in this description are merely exemplary of the invention that may be embodied in various and alternative forms. The drawings and figures included with this description are not necessarily to scale, and features may be exaggerated or minimized to illustrate details of particular components. Specific structural and functional details disclosed should be interpreted merely as a representative basis to variously employ the present invention and should not to be interpreted as limiting the invention. 
         [0042]    The embodiments of the present disclosure generally provide for a plurality of circuits and/or electrical devices. All references to the circuits or electrical devices and the functionality provided by each, are not intended to be limited to encompassing only what is illustrated and described herein. While particular labels may be assigned to the various circuits or other electrical devices disclosed, such labels are not intended to limit the scope of operation for the circuits and/or the other electrical devices. Such circuits and/or other electrical devices may be combined with each other and/or separated in any manner based on the particular type of electrical implementation that is desired. It is recognized that any circuit and/or other electrical device disclosed herein may include any number of microprocessors, integrated circuits, memory devices (e.g., FLASH, RAM, ROM, EPROM, EEPROM, or other suitable variants thereof) and software which co-act with one another to perform operation(s) disclosed herein. 
         [0043]    As shown in  FIG. 1  and  FIG. 3 , an aspect of the invention provides a system  8  for controlling the temperature of a build plate to enhance the throughput and output fidelity of a three-dimensional printer  200 . As shown in  FIG. 5 , the system provides a multifunctional build platform  10 , a plurality of thermoelectric cells  12 , a plurality of temperature sensors, a thermal conduction apparatus  16 , a printed circuit board  18  shown schematically in  FIG. 11  having electronic components, and a computer that executes algorithms to control the temperature of the build platform. 
         [0044]    The system may produce a uniform or variable thermal gradient across the build platform  10  that ranges in variability from a substantially uniform temperature gradient across the build platform to a temperature gradient that varies point wise from point to point across the surface plane of the build platform . The variability of the temperature gradient is dependent on the number of jointly or independently computer controlled thermoelectric cells  12  shown in  FIG. 5  coupled between the build platform  10  and a thermal conduction apparatus  16 . The thermoelectric cells  12  are under joint or independent control of the computer algorithms that and electronic control devices on the printed circuit board  18  shown schematically in  FIG. 11 . 
         [0045]    The multifunctional build platform  10  is multifunctional in that the build platform as shown in  FIG. 7  or  FIG. 8  provides a build plate  20 ,  21  to support a work-in-process during the production cycle of a three dimensional printer; provides a substrate for a printed circuit  22  as shown in  FIG. 9  that supplies electrical power as show in  FIG. 10  to the thermoelectric cells  12  and electronic signals to temperature controllers; and provides a thermal path that conducts heat to and from the work-in-process in accordance with a thermal gradient or thermal profile that extends across the build platform under system provided software control. 
         [0046]    As shown in  FIG. 7  and  FIG. 9 , the build platform  10  is a substantially rigid planar material that may have any appropriate geometric dimensions adapted to fit horizontally across the bottom of the build chamber of a three-dimensional printer. The build platform  10  may be made from compositions of ceramic compounds that may include high thermal conductivity compounds such as aluminum nitride, aluminum oxide, or boron nitride; or any other rigid material that remains dimensionally stable without warping or other significant dimensional alteration over the temperature range that a work-in-process may experience while being fabricated by a three-dimensional printer and of sufficient thickness to endure substantial thermal stress resulting from a variable thermal gradient imposed on the build platform by the print head of a three dimensional printer, the molten heat of a work-in process objects, and the heating and cooling effect of the thermoelectric cells or other temperature modification devices . The material comprising the build platform  10  is thermally conductive while providing sufficient electronic isolation of the various electronic components attached to the electric circuits  24  printed on the second surface of the build platform as shown in  FIG. 9  to allow each attached electronic component to properly function in response to electronic signals communicated through the printed circuits and the electric current supplied through the electric circuits. 
         [0047]    In one aspect of the invention, the build platform  10  is planar and of an appropriate geometric configuration adapted to fit horizontally across the bottom of a build chamber of a three-dimensional printer  200 . As shown in  FIG. 3  the build platform  10  provides a first surface that functions as a build plate  20  for the printer and provides a second surface  22  on the opposite side the build plate from the first surface that provides additional functioning as described below. The first surface or build plate  20  is adapted to accept extruded viscous raw materials exiting from the print head of a three-dimensional printer  200 . The print head applies the extruded viscous raw materials in a predefined pattern creating a work-in-process by building up a part in a vertical direction orthogonal to the build plate  20 , which is adapted to adhere to the viscous raw materials that are extruded from the print head and to subsequently release the adhered materials when the work-in-process is fabricated into a finished products and the temperature of the build platform and the finished product is sufficiently modified, which may occur at a predefined rate. . 
         [0048]    As shown in  FIG. 9 , the second surface  22  of the build platform  10  is substantially planar and may have a printed circuit bonded to the second surface or etched directly unto the second surface , The electric circuit  24  transmits electric power to the thermoelectric cells and transmits and communicates electrical signals from temperature sensors  14  to the circuit board under the control of the computer algorithms. The temperature sensors  14  may be thermistors, thermocouples or other electronic sensors adapted to communicate temperatures electronically to the electronic controls on the printed circuit board  18  that monitor the temperature of the build plate  20  and provides power to the thermoelectric cells  12  through the conductive traces of the electric circuit  24  on the second surface  22  of the build plate  20  in response to the specific requirements for a particular product being fabricated by the three-dimensional printer. The temperature sensors  14  are coupled to the second surface of the build platform by solder or other appropriate means and are connected to the thermal controller on the printed-circuit-board-A by wires or other appropriate means to permit electronic communication between the temperature sensors and the thermal controller. The system may provide a sufficient number of temperature sensors to provide redundancy. 
         [0049]    As shown in  FIG. 10 , each thermoelectric cell  12  is securely coupled with to and appropriately oriented to the electric circuit  24  provided on the second surface  22  of the build platform  10  to permit each thermoelectric cell  12  to heat or cool the build plate  20  as directed by the thermal controllers associated with the printed circuit board  18 . Each thermoelectric cell  12  is attached to the electric circuit  24  associated with the second surface of the build platform by solder or other appropriate means for the system to provide sufficient electric current to power the thermoelectric cells as necessary to maintain or modify the predetermined thermal gradient of the build plate. 
         [0050]    The thermoelectric cells  12  may be Peltier devices or other thermoelectric devices that use appropriately biased and powered electric current to heat and cool the build platform  20 . The thermoelectric cells  12  are rigidly attached to the electric circuit  24  associated with the second surface  22  of the build plate and the electric leads of the thermoelectric cells  12  are soldered or otherwise connected to the printed circuit associated with the second surface of the build platform to provide electric current to the thermoelectric cells  12  under system control. 
         [0051]    In one aspect of the invention, as shown in  FIG. 3 , the thermal conduction apparatus  16  transfers heat to and from the environment surrounding the exterior of the three dimensional printer and the thermoelectric cells  12  connected to the build plate  20 . As shown in  FIG. 5  and  FIG. 6 , the thermal conduction apparatus  16  may provide a base plate  28  that is a substantially rigid planar element, at least one heat pipe  30  that transfer heat to and from the base plate  28 , and at least one radiative element  32  that conducts heat to and from the heat pipes  30  to the exterior environment surrounding the three-dimensional printer  200 . 
         [0052]    The base plate  28  of the thermal conduction apparatus  16  may be a suitable thermal conductor that may be metal such as copper or aluminum or any other substantially rigid thermally conductive material that will aid in efficiently transferring heat between the thermoelectric cells  12  and the heat pipes  30 . As shown in  FIG. 1 , the base plate  28  is a substantially planar element having appropriate geometric dimensions that may exceed the dimensions of the build plate but not exceed the horizontal limits of the build cavity  204  of the printer. As shown in  FIG. 5  and  FIG. 6 , the base plate  28  provides a first surface  34  and a second surface  36  and is located in the build chamber  202  of the printer below the build platform  10 , and as shown in  FIG. 3 , oriented horizontally with respect to the upright position of the printer  200 . The first surface  34  of the base plate is a substantially planar element rigidly attached to the thermoelectric cells on the lower side of the thermoelectric cells opposite to the side where the thermoelectric devices attach to the circuit  24  on build platform  10 . The second surface  36  of the base plate is substantially planar and may provide impressions or elongated indentations that extend radially out from the center of the second surface to the periphery of the base plate that are adapted to be coupled with the heat pipes  30 . 
         [0053]    As shown in  FIG. 5  and  FIG. 6 , the heat pipes  30  may be L shaped or any appropriate geometric configuration of appropriate dimensions and having a first linear tubular element  40  and a second linear tubular element  42  connected to and having an appropriate geometrical orientation that may be orthogonal to the first element  40  or oriented at any appropriate angle to accommodate the various structural characteristics of three dimensional printers. The first linear tubular element  40  of each heat pipe  30  is securely coupled to the second surface  36  within the impressions or elongated impressions of the base plate of the thermal conduction apparatus. The first linear tubular elements  40  of the heat pipes  30  may arranged in a substantially radial or other suitable pattern on the second surface  36  of the base plate  28  and extend outward from the geometric center of the second surface  36  a predefined distance past the horizontal periphery of the base plate  28 . The second linear tubular element  42  of each heat pipe extends from the first linear tubular element in an appropriate geometrical relationship to the first tubular element beyond the periphery of the base plate and may extend vertically upward and orthogonally away from the base plate  28  or otherwise extend in an appropriate geometric relationship to the base plate. The second linear tubular element  42  of each heat pipe  30  is securely attached to a radiative element  32  that may be securely attached to the exterior frame  206  as shown in  FIG. 2 , of the three-dimensional printer. 
         [0054]    Each radiative element  32  may be an extended semi-tubular rigid element composed of thermally conductive material having a predefined diameter and securely attached to the exterior peripheral structural frame  206  of the three-dimensional printer, as shown in  FIG. 3 , orthogonally oriented to the build plate  20  and extending vertically upward from the bottom of the three dimensional printer a predefined distance from the first surface of the base plate  28 . 
         [0055]    In another aspect of the invention, the thermal conduction apparatus may provide at least one water block cooler that uses water or other liquids for heat transfer attached to the second surface of the base plate to provide cooling for the thermoelectric cells. 
         [0056]    As shown schematically in  FIG. 11 , the system provides a printed-circuit-board-A  18  comprised of various electronic components. The electronic components may include a thermal controller  50  and an H-bridge  52 , which may be a transistor or H bridge circuit connected to and controlled by appropriate electronic circuitry on the printed circuit board.  18 . The printed circuit board  18  receives sufficient electric current from an electronic power supply  54  to power the electronic devices and the thermoelectric cells  12  coupled with the build plate  20 . The thermal controller  50  may be comprised of appropriate electronic components and is in electronic communication with a computer  210 , the temperature sensors  14  coupled to the build plate  20 , and the H-bridge  52 . The thermal controller  50  accepts control signals from the computer  210  and accepts electronic temperature reading signals from the temperature sensors  14 . The thermal controller  26  transmits electronic temperature signals to the computer  210  and communicates electronically with the H-bridge  52  to provide appropriately biased current to the thermoelectric cells  12  coupled to the build platform  10 . 
         [0057]    A plurality of temperature sensors  14  are positioned proximate to the thermoelectric cells  12  and electronically communicate the temperature of the build plate  20  to the thermal controller  50  on the printed-circuit-board-A  18 . Each temperature sensor  14  transmits a signal to the thermal controller  26  that indicates the temperature of the build plate  20  proximate to the immediate location of the temperature sensor  14 . The thermal controller  50  determines whether the temperature of build plate  20  at the location of each temperature sensor  14  is greater or less than a predetermined temperature threshold provided by a computer algorithm. 
         [0058]    In one aspect of the invention, during the build phase If the temperature of the build plate  20  at a location proximate to a particular temperature sensor  14  is less than the temperature threshold, then the controller determines that it may be necessary to energize the thermoelectric cells  12  associated with the respective temperature sensors  14  to heat the location on the build plate  20  proximate to the associated temperature sensor. 
         [0059]    After the build phase, the system cools the build plate  20  by energizing the thermoelectric components at a current that is biased at a reverse polarity of the current applied to heat the build plate during the build phase. Each temperature sensor  14  transmits a signal to the thermal controller  26  indicating the temperature proximate to the respective temperature sensor  14 . The thermal controller  26  determines If the temperature of the build plate  20  at a location proximate to a particular temperature sensor  14  is greater than a temperature threshold associated with the particular temperature sensor, then the thermal controller  26  determines that it may be necessary to energize the thermoelectric cells  12  associated with the respective temperature sensors to cool the location on the build plate  20  proximate to the associated temperature sensor  14 . 
         [0060]    In some aspects of the invention, the system algorithm relies of differences between the thermal coefficient of expansion for the work-in-process in comparison to the thermal coefficient of expansion of the materials comprising the build plate. The system uses the differences in the expansion rates of the various materials as compared to the thermal expansion rate of the build plate  20  to cause the build plate to release the finished product resulting from the build cycle of a three dimensional printer at the appropriate temperature gradient. 
         [0061]    In one aspect of the invention as shown in  FIG. 12 , flowchart-A  100  schematically illustrates how the system uses a uniform temperature profile to control the temperature of the build plate and how the present system is integrated into the build process of a three-dimensional printer. Before initiation of the build, the system performs a self test  102  to determine if the electronic components and the thermoelectric cells of the system function according to a set of predetermined standards. Upon successful completion of the self test, a file having the temperature profile for the build process and the cooling cycle is input into a computer controlling the three-dimensional printer  104 . The computer uses data from the file and an appropriate algorithm based on the physical and chemical properties of the raw materials and environmental factors that may include the ambient temperature and humidity to create a thermal profile or gradient for the build plate  104 . The system reads the temperatures of the designated locations on the build plate and compares the respective temperatures to the desired thermal gradient  106 . If a variation exists  108 , the computer algorithm determines the electric power bias and level of current needed to achieve the desired temperature for each corresponding location on the build plate, and the system electronically communicates the polarity bias and current to the controller for each thermoelectric cell. When the correct temperature gradient is achieved, printing is initiated  110 . The system monitors the temperature of the build plate as each layer of printing is completed and electronically communicates the polarity bias and current level needed to the controller for each thermoelectric cell to adjust the temperature as needed to maintain the temperature profile of the build plate during the build process  112 . 
         [0062]    During the build process, the system dynamically monitors the electronic and thermal performance of the system and compares the performance data to a set of predetermined parameters  114 , and communicates electronically to the printer and printer operator  116  if the build process should halt or if any remedial action may be taken to prevent a process failure and to protect the safety of the operator, the printer, and the surrounding environment. 
         [0063]    When the three dimensional printer  200  has completed fabricating the work-in-process to produce the intended finished product  118 , the system initiates a cooling process  120 . The thermal controller compares the temperature at each polling location on the build plate and compares the temperatures to the target values in the file corresponding to each temperature sensor location on the build plate. An algorithm calculates the polarity bias and level of current needed for each thermoelectric cell to cool the build plate in accordance with the cool down temperature gradient of the build plate  122 . The system communicates the polarity bias and the current values to the thermal controllers for each thermoelectric cell  124 . The system sequentially polls each mapped location of the build plate. The system repeats the procedure until the temperature of the build plate equals a calculated value and the finished part releases from the build plate and the process ends  126 . 
         [0064]    In an alternative embodiment, as shown schematically in  FIG. 16 , the system provides a printed-circuit-board-B  60  comprised of various electronic components. The electronic components may include a plurality of thermal controllers  50  and a plurality of H-bridges  52 , which may be transistors or H bridge circuits. The printed-circuit-board-B  60  receives sufficient electric current  64  from a provided power supply  66  to power the thermal controllers  50  and the H-bridges  52  attached to the printed-circuit-board-B  60  along with the thermoelectric cells  12  coupled with the second surface  22  of the build platform  10 . Each thermal controller  50  is comprised of appropriate electronic circuitry and is in electronic communication with a computer  210 , one or more temperature sensors  14  coupled to the build platform  10 , and an associated H-bridge  52 . Each thermal controller  50  accepts control signals  68  from the computer and accepts temperature readings from associated temperature sensors  14 . Each thermal controller  50  sends temperature signals to the computer  210  and signals an associated H-bridge  52  to provide appropriately biased current to the associated thermoelectric cells  12  coupled to the build platform  10 . 
         [0065]    One or more temperature sensors  14  are positioned on the second surface  22  of the build platform  10  proximate to the thermoelectric cells  12  and electronically communicates  70  the temperature of the build platform to the thermal controller  50  associated with the respective H-bridge  52  coupled with printed-circuit-board-B  60 . Each temperature sensor  14  transmits a signal  70  to an associated thermal controller  50  that indicates the temperature of the build platform  10  proximate to the immediate location of the respective temperature sensor  14 . The thermal controller  50  determines whether the temperature of build platform at the location of each temperature sensor  14  is greater or less than a temperature threshold. 
         [0066]    During the build phase of the three dimensional printer, if the temperature of the build plate at a location proximate to a particular temperature sensor  14  is not within the range of a predetermined temperature threshold, then the respective thermal controller determines that it may be necessary to energize the thermoelectric cells  12  associated with the respective temperature sensor  14  with the appropriately biased electric current to heat or cool the location on the build build platform  10  proximate to the associated temperature sensor  14 . 
         [0067]    After the build phase, the system modifies the temperature of the build platform  10  by energizing the thermoelectric cells  12  at a current that is at reverse polarity of the current applied to heat the build platform  10  during the build phase. Each temperature sensor  14  transmits a signal to an associated thermal controller  50  indicating the temperature proximate to the respective temperature sensor  14 . The thermal controller  50  determines If the temperature of the build platform  10  at a location proximate to a particular temperature sensor  14  is greater than than a temperature threshold associated with the particular temperature sensor  14 , then the thermal controller  50  determines that it may be necessary to energize the thermoelectric cells  12  associated with the respective temperature sensors  14  to cool the location on the build build platform  10  proximate to the associated temperature sensor  14 . 
         [0068]    In some aspects of the invention, the system relies of differences between the thermal coefficient of expansion for the work-in-process in comparison to the thermal coefficient of expansion of the materials comprising the build platform  10 . The system uses the differences in the expansion rates of the various materials to cause the build plate  20  to release the work-in-process at the appropriate temperature gradient. 
         [0069]    In one aspect of the invention, as shown in  FIG. 17 , flowchart-B  80  illustrates how the system controls the build plate temperature and illustrates how the temperature control of the the invented system is integrated into the build process of a three-dimensional printer. Before initiation of the build, the system performs a self test  150  to determine if the electronic components and the thermoelectric cells of the system function according to a set of predetermined standards. Upon successful completion of the self-test, a file having the temperature profile for the build process and the cooling cycle is input into a computer controlling the three-dimensional printer  152 . The computer uses data from the file and an appropriate algorithm based on the physical and chemical properties of the raw materials and environmental factors that may include the ambient temperature and humidity to create a thermal profile or gradient for the build plate  154 . The system reads the temperatures from the temperature sensors at designated locations on the build plate and compares the respective temperatures to the desired thermal gradient  156 . If a temperature variation exists  158 , a computer algorithm determines the electric power bias and level of current needed to achieve the desired temperature for each corresponding location on the build plate and the system electronically communicates the polarity bias and current to the controller for each thermoelectric cell associated with the corresponding location. When the correct temperature gradient is achieved, printing is initiated  160 . The system monitors the temperature of the build plate as each layer of printing is completed and electronically communicates the polarity bias and current level needed to the thermal controller for each thermoelectric cell to adjust the temperature to maintain the temperature profile of the build plate  162 . 
         [0070]    During the build process, the system dynamically monitors the electronic and thermal performance of the system and compares the performance data to a set of predetermined parameters  164 , and communicates electronically to the printer and printer operator  166  if the build process should halt or if any remedial action may be taken to prevent a process failure and to protect the safety of the operator, the printer, and the surrounding environment. 
         [0071]    During the build phase, if the temperature of the build plate at a location proximate to a particular temperature sensor  14  is not within the range of a predetermined temperature threshold, then the respective thermal controller determines that it may be necessary to energize the thermoelectric cells  12  associated with the respective temperature sensor  14  with the appropriately biased electric current to heat or cool the location on the build platform  10  proximate to the associated temperature sensor  14 . 
         [0072]    When the printer has completed building the intended part, the system initiates the cooling process. The compares the temperature at each polling location on the build plate and compares the temperatures to the target values in the file corresponding to each polled location on the build plate  170 . An algorithm calculates the polarity bias and level of current needed for each thermoelectric cell to cool the build plate in accordance with the cool down temperature gradient of the build plate. The system communicates the polarity bias and the current values to the controllers for each thermoelectric cell.  172  The system sequentially polls each mapped location of the build platform corresponding to each respective thermoelectric cell  174 . The system repeats the procedure for the entire surface of the build plate and may compare the thermal gradient at each point to the thermal profile for the specific build process  174 . The system continues to loop through the cooling process until the temperature of the build plate matches the thermal gradient calculated at the start of the cooling process and until the finished part releases from the build plate and the process ends  176 .