Abstract:
A programmed material consolidation method includes use of an object release element for facilitate removal of an object from a platen of programmed material consolation equipment while leaving substantially no residue on the platen or a fabricated object, and without requiring substantial post-release modification of the fabricated object. The object release element may be adhesively secured to a non-stick surface of the platen, with a material that adheres to the platen before being cured and that may be removed from the platen upon curing, or by application of a negative pressure through the platen to the object release element. The object release element may be formed from a material or include coating of a material, such as polyethylene, polyethyleneteraphthalate, or polyethylene ethyl ketone, that adheres to a fabricated object, but may be readily released from the fabricated object (e.g., by peeling).

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application is a divisional of application Ser. No. 10/663,402, filed Sep. 16, 2003, pending. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates generally to processes for facilitating the removal of stereolithographically fabricated objects from platens on or over which they are formed and, more specifically, to processes that facilitate the removal of stereolithographically fabricated objects without requiring the use of the material or materials used in fabricating such objects. In particular, the present invention relates to processes which employ an object release element upon which an object may be stereolithographically fabricated and which may subsequently be readily removed from a platen of stereolithographic fabrication equipment and from the stereolithographically fabricated object.  
         [0004]     2. Background of Related Art  
         [0005]     “Stereolithography” is a manufacturing process that is employed in many industries. Stereolithography, which is also known as “layered manufacturing,” essentially involves the use of a computer to generate a three-dimensional (3-D) mathematical simulation or model of an object to be fabricated. Such a simulation or model is usually generated and manipulated with 3-D computer-aided design (CAD) software. The simulation or model is mathematically separated or “sliced” into a large number of relatively thin, parallel, usually vertically superimposed layers, each layer having defined boundaries and other features associated with the simulation or model and, thus, the actual object to be fabricated at the level of that layer within the exterior boundaries of the object. A complete assembly or stack of all of the layers defines the entire object, and surface resolution of the object is, in part, dependent upon the thicknesses of the layers.  
         [0006]     The simulation or model is then employed to generate an actual object by building the object, layer by superimposed layer. A wide variety of approaches to stereolithography by different companies has resulted in techniques for fabrication of objects from a variety of materials. As shown in  FIG. 1 , many stereolithographic fabrication techniques involve the disposition of a layer  4 ′ of unconsolidated or unfixed material  3  corresponding to each layer of the simulation or model and, thus, of an object  5  to be fabricated. Next, unconsolidated or unfixed material  3  at and within at least portions of the boundaries of that layer  4 ′ of object  5  is selectively consolidated or fixed to an at least a partially consolidated, or semisolid, state. At the same time, material  3  of a layer  4 ′ under fabrication may be adhered or bonded to a next-lower layer  4  of object  5 .  
         [0007]     Depending upon the type of stereolithographic technique being employed, as well as the stereolithographic fabrication equipment used to effect the technique, the unconsolidated or unfixed material  3  employed to build object  5  may be supplied in particulate or liquid form, and unconsolidated or unfixed material  3  may itself be consolidated or fixed, or a separate binder material may be employed to bond material particles to one another and to those of a previously formed layer.  
         [0008]     When particulate materials are employed, resolution of object surfaces is highly dependent upon particle size, whereas when a liquid is employed, surface resolution is highly dependent upon the minimum surface area of the liquid which can be fixed and the minimum thickness of a layer that can be generated. Of course, in either case, resolution and accuracy of object reproduction from the CAD file is also dependent upon the ability of the apparatus used to fix the material to precisely track the mathematical instructions indicating solid areas and boundaries for each layer of material. Toward that end, and depending upon the layer being fixed, various fixation approaches have been employed, including particle bombardment (electron beams), disposing a binder or other fixative (such as by ink-jet printing techniques), or irradiation using heat or specific wavelength ranges.  
         [0009]     The latter irradiation approach may be effected with the SLA-250/50HR, SLA-5000, and SLA-7000 stereolithography systems that are offered by 3D Systems, Inc., of Valencia, Calif., using ultraviolet-curable polymers, or “photopolymers,” such as CIBATOOL SL 5170 and SL 5210 resins (for the SLA-250/50HR system), CIBATOOL SL 5530 resin (for the SLA-5000 and SLA-7000 systems), and CIBATOOL SL 7510 resin (for the SLA-7000 system), each of which is available from Ciba Specialty Chemicals Company. Examples of the processes that may be used in performing these techniques are described in various United States Patents that have been assigned to 3D Systems, including, without limitation, U.S. Pat. Nos. 4,575,330; 4,929,402; 4,996,010; 4,999,143; 5,015,424; 5,058,988; 5,059,021; 5,059,359; 5,071,337; 5,076,974; 5,096,530; 5,104,592; 5,123,734; 5,130,064; 5,133,987; 5,141,680; 5,143,663; 5,164,128; 5,174,931; 5,174,943; 5,182,055; 5,182,056; 5,182,715; 5,184,307; 5,192,469; 5,192,559; 5,209,878; 5,234,636; 5,236,637; 5,238,639; 5,248,456; 5,256,340; 5,258,146; 5,267,013; 5,273,691; 5,321,622; 5,344,298; 5,345,391; 5,358,673; 5,447,822; 5,481,470; 5,495,328; 5,501,824; 5,554,336; 5,556,590; 5,569,349; 5,569,431; 5,571,471; 5,573,722; 5,609,812; 5,609,813; 5,610,824; 5,630,981; 5,637,169; 5,651,934; 5,667,820; 5,672,312; 5,676,904; 5,688,464; 5,693,144; 5,695,707; 5,711,911; 5,776,409; 5,779,967; 5,814,265; 5,850,239; 5,854,748; 5,855,718; 5,855,836; 5,885,511; 5,897,825; 5,902,537; 5,902,538; 5,904,889; 5,943,235; and 5,945,058. The disclosure of each of the foregoing patents is hereby incorporated herein in its entirety by this reference.  
         [0010]     When ultraviolet-curing stereolithographic techniques are used to fabricate objects, the objects are formed directly on a support surface of a platen, or tray, of a stereolithographic fabrication apparatus. When cured, the ultraviolet-curable materials that are usually used in such processes typically adhere to the platen. Thus, an object which has been stereolithographically fabricated from ultraviolet-curable materials is typically removed from the platen on which it was formed by way of mechanical removal processes.  
         [0011]     In order to facilitate removal of a stereolithographically fabricated object from a platen  112  and reduce damage to a stereolithographically fabricated object  5  during the removal process, and as shown in  FIG. 2 , substructures, such as extremely fine columns, or “hairs”  6 , may be stereolithographically fabricated on a support surface  114  of platen  112  prior to stereolithographic fabrication of object  5  thereon. After hairs  6  have been fabricated to a desired height, a mesa-like structure  7  is formed thereover. The desired object  5  is then formed, layer by superimposed layer, in accordance with programming of a stereolithographic system controller, such as a computer. The system controller controls the depth the platen is lowered into a bath of ultraviolet-curable polymer, as well as the locations of a layer of such polymer that are to be exposed to ultraviolet radiation, which is typically embodied as a laser beam.  
         [0012]     Once the desired object has been fabricated, the hairs may be cut. The portions of hairs  6  that remain on the fabricated object  5  may also be removed therefrom, such as by sanding, as may the mesa-like structure  7 .  
         [0013]     Although this practice has found widespread use in ultraviolet-curing stereolithography techniques, it remains somewhat undesirable due to the amount of expensive, ultraviolet-curable polymer that is required just for forming the hairs. Also, the amount of equipment time that is needed to fabricate the hairs is significant and could be put to better use in fabricating the finished product. Further, a significant amount of time is required to finish the bottom surface of each fabricated object by removing the remainders of any hairs therefrom and, possibly, the mesa-like structures that were formed above the hairs.  
         [0014]     Accordingly, there is a need for a process and element to facilitate the release of objects from the platens of stereolithographic fabrication equipment without consuming excess stereolithographic fabrication material and without requiring additional finishing of the stereolithographically fabricated object.  
       SUMMARY OF THE INVENTION  
       [0015]     The present invention, in one embodiment, includes a process for facilitating the removal of stereolithographically fabricated objects from the platens on or over which they are formed. Processes for forming object release elements in accordance with teachings of the present invention do not require the use of the same material or materials that are to be used to stereolithographically fabricate one or more objects that will have to be removed from the platen of a stereolithographic fabrication apparatus.  
         [0016]     As an example of a process according to the present invention, an object release element that may subsequently be readily removed from a platen of stereolithographic fabrication equipment and from the stereolithographically fabricated object may be used. Initially, the object release element is secured to a platen of stereolithographic fabrication equipment. An object is then fabricated, using stereolithographic fabrication techniques, directly on the object release element. Once the object has been fabricated, the object release element may be removed from both the platen and the stereolithographically fabricated object.  
         [0017]     An object release element that is useful in a process according to the present invention and, thus, which incorporates teachings of the present invention, comprises a substrate which includes an upper surface and a lower surface. The upper surface of the substrate, which is configured to have one or more objects stereolithographically fabricated thereon, may remain exposed when the object release element is secured to a platen. The material from which the substrate is formed, or from which a layer on the upper surface of the substrate is formed, may temporarily adhere to a stereolithographically fabricated object thereon, but readily release, or peel, from the stereolithographically fabricated structure when such removal is desired, such as when the object release element is pulled away from a fabricated object with sufficient force.  
         [0018]     The lower surface of the substrate may be coated with a material, such as a suitable adhesive, which facilitates adhesion of the object release element to a platen of stereolithographic fabrication equipment, as well as removal of the object release element from the platen. By way of example only, a polymer, such as an ultraviolet-curable adhesive, that adheres to the material (e.g., stainless steel, quartz, etc.) of the platen when in an uncured state, but has reduced adhesion to the material of the platen when in a cured state, may be used. Alternatively, the lower surface of the substrate of the object release element may be coated with a suitable pressure sensitive adhesive. As yet another example, the lower surface of the substrate of an object release element incorporating teachings of the present invention may be configured to seal against a platen of a stereolithographic fabrication apparatus when a negative pressure (e.g., a vacuum) is applied thereto through the platen (e.g., lower surface may be substantially planar, comprise a somewhat conformable material, etc.).  
         [0019]     Thus, the present invention also includes stereolithographic fabrication apparatus with platens that are configured to communicate a negative pressure to support surfaces thereof.  
         [0020]     Object release elements and processes that incorporate teachings of the present invention may be used to stereolithographically fabricate any type of object, including, but not limited to, so-called “rapid prototypes” and mass-produced structures, such as components that are to be used with semiconductor devices, or “semiconductor device components.” By way of example only, stereolithographic processes may be used to fabricate test sockets and burn-in sockets of various configurations, as well as other semiconductor device components that are currently made by use of molding processes.  
         [0021]     The present invention also includes stereolithographic systems that include the object release elements on the platens thereof, methods for stereolithographically fabricating objects by using the object release elements, and the objects that are produced when object release elements that incorporate teachings of the present invention are used in stereolithographic fabrication processes.  
         [0022]     Other features and advantages of the present invention will become apparent to those of ordinary skill in the art through consideration of the ensuing description, the accompanying drawings, and the appended claims. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0023]     In the drawings, which depict exemplary embodiments of various aspects of the present invention:  
         [0024]      FIG. 1  schematically depicts an example of a conventional stereolithography process;  
         [0025]      FIG. 2  is a side view illustrating the result of a conventional process for facilitating the removal of a stereolithographically fabricated object from the platen on or over which it has been fabricated;  
         [0026]      FIG. 3  is a cross-sectional representation of an exemplary object release element that embodies teachings of the present invention and which includes a substantially planar substrate that is formed from a material which is removable from a stereolithographically fabricated object;  
         [0027]      FIG. 3A  is a cross-sectional representation of an exemplary object release element of the present invention and which includes a lower surface which is configured to be secured to a platen by way of a negative pressure communicated to a support surface of the platen;  
         [0028]      FIG. 4  is a cross-sectional representation of another exemplary embodiment of object release element according to the present invention, which includes an object release coating on a substantially planar substrate thereof, the object release coating being formed from a material that is removable from a stereolithographically fabricated object;  
         [0029]      FIG. 5  is a cross-sectional representation of an exemplary embodiment of an object release element that includes a nonplanar fabrication surface;  
         [0030]      FIG. 6  is a cross-sectional representation of still another exemplary embodiment of object release element, which is configured for use in forming objects that include regions that overhang the object release element and, thus, which protrude from a lower surface an object formed thereon;  
         [0031]      FIG. 7  is a schematic representation depicting placement of an object release element of the present invention on a platen of stereolithographic fabrication equipment;  
         [0032]      FIGS. 8 through 10  are schematic representations that show stereolithographic fabrication of an object over an object release element that has been secured to the platen of stereolithographic fabrication equipment;  
         [0033]      FIGS. 11 and 12  are schematic representations that illustrate exemplary acts that may be effected to remove the object release element from the platen; and  
         [0034]      FIGS. 13 and 14  schematically depict removal of the object release element from the object that has been stereolithographically fabricated thereon. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0035]     An exemplary embodiment of object release element  10  that incorporates teachings of the present invention is shown in  FIG. 3 . Object release element  10  includes a substantially planar substrate  12  which has a shape and dimensions that are suitable for placement over at least a portion of a platen  112  of stereolithographic fabrication equipment  110  ( FIG. 8 ) by which one or more objects  50  ( FIG. 10 ) will be formed. In addition, object release element  10  includes an adhesive coating  18  on a lower surface  16  of substantially planar substrate  12 , while an upper surface  14  of substantially planar substrate  12  remains exposed.  
         [0036]     Substantially planar substrate  12  comprises a material to which selectively consolidated regions of a lowermost layer of an object  50  ( FIG. 10 ) under fabrication will adhere, but which is readily removable therefrom, such as by peeling (i.e., pulling on substantially planar substrate  12  with sufficient force to remove the same from object  50 ), by etching, as known in the art and as suitable for removing the material of substantially planar substrate  12  without substantially removing or otherwise adversely affecting the material of object  50 , or by any other suitable technique.  
         [0037]     Examples of materials from which substantially planar substrate  12  may be formed include, but are not limited to, polyethylene (“PE”), polyethyleneteraphthalate (“PET”), and polyethylene ethyl ketone (“PEK”).  
         [0038]     Adhesive coating  18  comprises a material which will adhere to a surface of platen  112  of stereolithographic fabrication equipment  110  ( FIG. 8 ) while an object  50  ( FIG. 10 ) is being stereolithographically fabricated thereon, but which may be readily removed from platen  112  once the stereolithographic fabrication of object  50  is complete. By way of example only, a material that is tacky and, thus, adheres to a support surface  114  of platen  112  when in an uncured or partially cured state, but which releases from platen when cured, or cross-linked (e.g., by exposure to a sufficient dosage of ultraviolet (UV) radiation, heat, etc.), may be used as adhesive coating  18 . UV-curable materials that have these properties include, without limitation, light-curable adhesives available from 3M Company of St. Paul, Minn., and the adhesives that are currently used on the ICROS® tapes of Mitsui Chemicals America, Inc., of Purchase, N.Y.  
         [0039]      FIG. 3A  shows an embodiment of object release element  11  that includes a substrate  12  with a lower surface  16  which is configured to be secured to a support surface  114 ′ of a platen  112 ′ of a stereolithographic fabrication apparatus (e.g., stereolithographic fabrication apparatus  110  of  FIGS. 8 through 12 ) by way of a negative pressure V (e.g., a vacuum). Thus, object release element  11  may lack the adhesive coating ( FIG. 3 ) of object release element  10 . Negative pressure V may be communicated to support surface  114 ′ from a negative pressure source S through one or more conduits  113 ′ within or otherwise associated with platen  112 ′ and ports  115 ′ that communicate with both conduit  113 ′ and support surface  114 ′. Lower surface  16  may merely comprise a substantially planar surface, or substrate  12  may be formed from a material (e.g., a somewhat conformable material) which seals against support surface  114 ′ as a negative pressure is applied through platen  112 ′ to lower surface  16 .  
         [0040]     Another exemplary embodiment of object release element  10 ′ according to the present invention is shown in  FIG. 4 . In addition to a substantially planar substrate  12 ′ and an adhesive coating  18  on a lower surface  16 ′ of substantially planar substrate  12 ′, object release element  10 ′ includes an object release coating  20  on an upper surface  14 ′ of substantially planar substrate  12 ′. Object release coating  20  may be formed from a material, such as PE, PET, or PEK, that will adhere to, but is readily removable from, a stereolithographically fabricated object  50  ( FIG. 10 ). As such, substantially planar substrate  12 ′ may be formed from any suitable material to which an object release coating  20  will adhere, at least until removal of object release element  10 ′ from an object  50  is desired.  
         [0041]     Turning now to  FIG. 5 , another embodiment of object release element  10 ″ according to the present invention is depicted. Object release element  10 ″ includes a substrate  12 ″, which includes substantially planar, parallel, opposite upper and lower surfaces  14 ″ and  16 ″, respectively, and which has a thickness T that is greater than those of substrates  12  and  12 ′ of object release elements  10  and  10 ′, respectively ( FIGS. 3 and 4 , respectively). Accordingly, upper surface  14 ″ of substrate  12 ″ of object release element  10 ″ is elevated above a support surface  114  of a platen  112  upon which object release element  10 ″ is placed by a distance E which is at least as great as thickness T. As such, object release element  10 ″ is useful for fabricating one or more objects  50 ″ that include features  51 ″ that protrude from a fabrication surface  54 ″ thereof located over upper surface  14 ″, or which intersect a plane on which fabrication surface  54 ″ resides. Accordingly, thickness T of substrate  12 ″ is about the same dimension as or larger than a distance P that feature  51 ″ extends beyond lowermost fabrication surface  54 ″ of object  50 ″.  
         [0042]     Of course, the material from which substrate  12 ″ is formed may adhere to, but be readily removable from, a stereolithographically fabricated object  50 ″, or substrate  12 ″ may include a coating (not shown) of such a material on an upper surface  14 ″ thereof, as described with respect to object release element  10 ′, which is depicted in  FIG. 4 .  
         [0043]     In order to facilitate adhesion of object release element  10 ″ to support surface  114  of platen  112  of stereolithographic fabrication equipment  110  ( FIG. 8 ), an adhesive coating  18 , such as that described above in reference to object release elements  10  and  10 ′ depicted in  FIGS. 3 and 4 , respectively, may be located on at least a portion of lower surface  16 ″ of substrate  12 ″ of object release element  10 ″.  
         [0044]      FIG. 6  illustrates an object release element  10 ′″ which includes a three-dimensional substrate  12 ′″. Substrate  12 ′″ may be formed from a material that will adhere to, but is readily removable from, a stereolithographically fabricated object  50 ′″, or it may include a coating (not shown) of such material on an upper surface  14 ′″ thereof, as described with respect to object release element  10 ′, which is depicted in  FIG. 4 .  
         [0045]     With continued reference to  FIG. 6 , as lower surface  16 ′″ of substrate  12 ′″ is configured to be placed against a support surface  114  of a platen  112  of stereolithographic fabrication equipment  110  ( FIG. 8 ), lower surface  16 ′″ is substantially planar. Like object release elements  10  and  10 ′, object release element  10 ′″ includes an adhesive coating  18  on at least a portion of lower surface  16 ′″ thereof so that object release element  10 ′″ may be secured to support surface  114  of platen  112  during stereolithographic fabrication of one or more objects  50 ′″ thereon and to facilitate ready removal of each object  50 ′″ from support surface  114  of platen  112  once stereolithographic fabrication processes have been completed.  
         [0046]     Upper surface  14 ′″ of substrate  12 ′″, against which an object  50 ′″ is to be fabricated, is, however, nonplanar. The contour of upper surface  14 ″ may correspond to (i.e., act as a “negative” for) a corresponding bottom surface of each object  50 ′″ that is to be stereolithographically fabricated on object release element  10 ′″. As shown in  FIG. 6 , upper surface  14 ′″ of substrate  12 ′″ includes a concave recess  15 ′″, within which a complementary convex surface  53 ′″ of an object  50 ″ may be formed during the stereolithographic fabrication of object  50 ′″. Of course, upper surfaces  14 ′″ having other nonplanar configurations, including other configurations of recesses, are also within the scope of the present invention.  
         [0047]     Turning now to  FIG. 7 , placement of an object release element  10 ,  10 ′,  10 ″,  10 ′″ that incorporates teachings of the present invention onto a platen  112  of stereolithographic fabrication equipment  110  ( FIG. 8 ) is depicted.  
         [0048]     Initially, to facilitate removal of object release element  10 ,  10 ′,  10 ″,  10 ′″ from a support surface  114  of platen  112 , support surface  114  may be at least partially formed from a material from which cured adhesive coating  18  may be readily removed, or a “nonstick material.” By way of example only, a nonstick material such as a TEFLON® fluorine-containing polymer available from E.I. du Pont de Nemours &amp; Company of Wilmington, Del., or a fluorine-containing polymer available from another source may be used, employing known processes, to form at least a portion of support surface  114  or a lining or coating thereon.  
         [0049]     If support surface  114  does not include a material from which adhesive coating  18  may be readily removed, at least a portion of a support surface  114  of platen  112  may be lined or coated with a layer  116  of nonstick material. By way of example only, layer  116  may be formed on an upper surface  114  of a platen  112  (e.g., a platen that includes stainless steel, quartz, etc.) by using known techniques to vapor deposit a fluorine-containing polymer, such as TEFLON®.  
         [0050]     Object release element  10 ,  10 ′,  10 ″,  10 ′″ is oriented over support surface  114  of platen  112  with lower surface  16  thereof and adhesive coating  18  facing support surface  114 . Once object release element  10 ,  10 ′,  10 ″,  10 ′″ has been positioned over support surface  114  as desired, object release element  10 ,  10 ′,  10 ″,  10 ′″ may be temporarily secured in position relative to support surface  114  by way of the tackiness of adhesive coating  18 . The tackiness of adhesive coating  18  provides sufficient adhesion to support surface  114  or a layer  116  thereon so that object release element  10 ,  10 ′,  10 ″,  10 ′″ will maintain a stationary position relative to platen  112  as an object  50  ( FIG. 10 ) is being stereolithographically fabricated on object release element  10 ,  10 ′,  10 ″,  10 ′″.  
         [0051]     With returned reference to  FIG. 3A , object release element  11  may be secured to platen  112 ′ by placing object release element  11  on support surface  114 ′ of platen  112 ′ and actuating source S such that negative pressure V is applied through conduit  113 ′ and ports  115 ′ to lower surface  16  of substrate  12  of object release element  11 .  
         [0052]     Once object release element  10 ,  10 ′,  10 ″,  10 ′″ has been secured to support surface  114  of platen  112  or, as shown in  FIG. 3A , once object release element  11  has been secured to support surface  114 ′ of platen  112 ′, stereolithographic fabrication of one or more objects  50 ,  50 ″,  50 ′″ ( FIG. 10 ) on object release element  10 ,  10 ′,  10 ″,  10 ′″, or  11  may commence, as known in the art, without the need for conventional preliminary fabrication of hairs or mesas.  FIGS. 8 through 10  depict an exemplary process for fabricating an object  50 ,  50 ″,  50 ′″ on an object release element  10 ,  10 ′,  10 ″,  10 ′″ according to the present invention. Although  FIGS. 8 through 10  do not depict the fabrication of an object  50 ,  50 ″,  50 ′″ on object release element  11 , the same object fabrication processes described hereinafter may be employed when object release element  11  is used.  
         [0053]     As shown in  FIG. 8 , platen  112 , with object release element  10 ,  10 ′,  10 ″,  10 ′″ secured to upper surface  114  thereof, is lowered into a tank  120  of stereolithographic fabrication equipment  110 . Tank  120  is partially filled to a predetermined level L with unconsolidated material  210 , such as a photopolymer (e.g., a UV-curable polymer, such as CIBATOOL SL 5170 and SL 5210 resins (for the SLA-250/50HR system), CIBATOOL SL 5530 resin (for the SLA-5000 and SLA-7000 systems), and CIBATOOL SL 7510 resin (for the SLA-7000 system) each of which is available from Ciba Specialty Chemicals Company)). Initially, platen  112  is lowered into unconsolidated material  210  a sufficient distance that a layer  212  of unconsolidated material  210  of desired thickness T 1  is formed over object release element  10 ,  10 ′,  10 ″,  10 ′″. Focused consolidating energy  130 , such as a beam (e.g., a laser beam) of a wavelength or range of wavelengths (e.g., UV radiation) suitable for at least partially consolidating unconsolidated material  210 , is then directed onto selected regions  214  of layer  212  to at least partially cure unconsolidated material  210  located in selected regions  214 . Of course, the movement of focused consolidating energy  130  may be controlled, such as by way of a controller that operates in accordance with programming for fabricating a first layer  52   a  of an object  50 ,  50 ″,  50 ′″ ( FIG. 10 ), as known in the art of stereolithography. When first layer  52   a  is completely formed, platen  112  may again be lowered a sufficient distance to form another layer  52   n  of unconsolidated material  210  of a corresponding thickness T n  over first layer  52   a , and the selective consolidation of unconsolidated material within specified regions of that layer effected, over and over again, as shown in  FIG. 9 , until the stereolithographic fabrication of each object  50 ,  50 ″,  50 ′″ on object release element  10 ,  10 ′,  10 ″,  10 ′″ is complete, as shown in  FIG. 10 .  
         [0054]     Turning now to  FIG. 11 , once object  50 ,  50 ″,  50 ′″ is complete, platen  112  may be raised above level L so that unconsolidated material  210  that remains on object  50 ,  50 ″,  50 ′″ and platen  112  may be recovered within tank  120 , as known in the art. In this manner, unused unconsolidated material  210  may be preserved for subsequent use.  
         [0055]     In addition, either prior to, during, or after the removal of object  50 ,  50 ″,  50 ′″ from tank  120 , adhesive coating  18  ( FIGS. 3 through 6 ) of object release element  10 ,  10 ′,  10 ″,  10 ′″ may be exposed to conditions that will facilitate the removal of object release element  10 ,  10 ′,  10 ″,  10 ′″ and, thus, object  50 ,  50 ″,  50 ′″ from platen  112 .  
         [0056]     By way of example only, when a UV-curable material or light-curable material is employed as adhesive coating  18 , adhesive coating  18  may be exposed to a sufficient dosage of radiation of one or more appropriate wavelengths to initiate cross-linking, or curing, of the material of adhesive coating  18 . Such exposure may be effected until the material of adhesive coating  18  is substantially cross-linked, or cured, or followed with exposure of adhesive coating  18  to other conditions, such as increased temperature, that will facilitate further cross-linking, or curing, thereof.  
         [0057]     Alternatively, if a heat-curable material is employed as adhesive coating  18 , adhesive coating  18  may heated to a sufficient temperature to cross-link, or cure, the same.  
         [0058]     When the material of adhesive coating  18  has been substantially cured, it will no longer adhere to the nonstick material of upper surface  114  of platen  112  or of a nonstick layer  116  thereon. As a result, object release element  10 ,  10 ′,  10 ″,  10 ′″ and each object  50 ,  50 ″,  50 ′″ carried thereby may be readily removed from upper surface  114  of platen  112 , as illustrated in  FIG. 12 . Additionally, by substantially curing the material of adhesive coating  18 , substantially no residual adhesive material will remain on upper surface  114  of platen  112 , eliminating the need to clean the same and, thus, the associated potential for damaging upper surface  114 .  
         [0059]     Referring now to  FIGS. 13 and 14 , exemplary methods for removing object release element  10 ,  10 ′,  10 ″,  10 ′″ from one or more fabricated objects  50 ,  50 ″,  50 ′″ are depicted.  
         [0060]     As shown in  FIG. 13 , object release element  10 ,  10 ′,  10 ″,  10 ′″ may be peeled from each object  50 ,  50 ″,  50 ′″ that has been stereolithographically fabricated thereon. As is well known, peeling may be effected by pulling one or both of object release element  10 ,  10 ′,  10 ″,  10 ′″ and an object  50 ,  50 ″,  50 ′″ thereon away from the other. Such peeling may be effected manually or mechanically. By way of example only, object release element  10 ,  10 ′,  10 ″,  10 ′″ may be pulled away from one or more objects  50 ,  50 ″,  50 ′″ by placing an edge of object release element  10 ,  10 ′,  10 ″,  10 ′″ on one side  312  of a separating edge  310  with the majority of each object  50 ,  50 ″,  50 ′″ being located on the opposite side  314  of separating edge  310 . A pulling force, exerted substantially along the plane of object release element  10 ,  10 ′,  10 ″,  10 ′″, as shown by arrow A, is then applied to force object release element  10 ,  10 ′,  10 ″,  10 ′″ and each object  50 ,  50 ″,  50 ′″ carried thereby onto opposite sides  312  and  314 , respectively, of separating edge  310 . This process continues until object release element  10 ,  10 ′,  10 ″,  10 ′″ has been completely removed from each object  50 ,  50 ″,  50 ′″ that was stereolithographically fabricated thereon.  
         [0061]      FIG. 14  depicts another exemplary method for removing objects  50 ,  50 ″,  50 ′″ from object release elements  10 ,  10 ′,  10 ″,  10 ′″. The method depicted in  FIG. 14 , which employs equipment similar to that described in U.S. Pat. No. 6,202,292, issued to Farnworth et al. on Mar. 20, 2001, the entire disclosure of which is hereby incorporated herein by this reference, includes reducing the adhesion of regions of object release element  10 ,  10 ′,  10 ″,  10 ′″ to one or more objects  50 ,  50 ″,  50 ′″ thereon by applying negative pressure (e.g., vacuum), shown as arrows V, to regions of at least a portion  10 R thereof while an object  50 ,  50 ″,  50 ′″ located opposite that portion of object release element  10 ,  10 ′,  10 ″,  10 ′″ is maintained in a substantially stationary position. Each object  50 ,  50 ″,  50 ′″ over a region  10 R of reduced adhesion may then be removed (e.g., by pulling the same) from object release element  10 ,  10 ′,  10 ″,  10 ′″ with relative ease, such as by use of a vacuum pick-up head, mechanically, or manually.  
         [0062]     Of course, other techniques for removing object release element  10 ,  10 ′,  10 ″,  10 ′″ from one or more stereolithographically fabricated objects may also be used without departing from the scope of the present invention.  
         [0063]     It is currently preferred that the technique that is employed leave substantially no pieces of object release element  10 ,  10 ′,  10 ″,  10 ′″ or residue therefrom on object  50 ,  50 ″,  50 ′″. It is also currently preferred that little or no additional finishing of the surface  54  of object  50 ,  50 ″,  50 ′″ that was located adjacent to object release element  10 ,  10 ′,  10 ″,  10 ′″ prior to removing the same from object  50 ,  50 ″,  50 ′″ be required.  
         [0064]     Although the foregoing description contains many specifics, these should not be construed as limiting the scope of the present invention, but merely as providing illustrations of some of the presently preferred embodiments. Similarly, other embodiments of the invention may be devised which do not depart from the spirit or scope of the present invention. Moreover, features from different embodiments of the invention may be employed in combination. The scope of the invention is, therefore, indicated and limited only by the appended claims and their legal equivalents, rather than by the foregoing description. All additions, deletions, and modifications to the invention, as disclosed herein, which fall within the meaning and scope of the claims are to be embraced thereby.