BACKGROUND OF THE INVENTION imaging member such as a photoconductor by applying light as a graphic pattern thereon.

This invention relates generally to the building of Thereafter, the latent electrostatic image is developed three-dimensional objects, and, more particularly, by depositing a part compositional powder and a concerns an improved process for building three- support powder onto the surface of the imaging dimensional objects based on electrophotograhic member whereon the part compositional powder printing, wherein deformations found, in completed adheres to the image portions of the latent image and three-dimensional objects caused by spillover effects the support powder adheres to the non-image portions of the building process are minimized. of the latent image. The developed image is then

The production of three-dimensional objects in transferred from the imaging member to a substrate. an additive manner without the need for any tooling Subsequent layers are also formed in the same by numerous methods is well known. In such manner and deposited directly onto the previously systems, a three-dimensional object is built layer-by- deposited layer. The process is repeated until the layer with each layer representing selected cross- three-dimensional object is fully formed.

sections thereof. Successive, adjacent layers A method is described in U.S. Pat. No. 6,376,148 representing corresponding successive, adjacent which operates in substantially the same manner as cross-sections of the object being built are formed described herein with reference to U.S. Pat. No. and bonded together to produced the object involved. 6,066,285. In one preferred embodiment, a first layer

One such system is described in U.S. Pat. No. of primary body-building powder material is 4,575,330. The system generates a three-dimensional deposited on a support platform and an object layer-by-layer in a process called electrophotographic printing means is operated to stereolithography wherein a beam of UV laser is create a transferable binder powder image in guided across the surface of a liquid UV-curable accordance with the three-dimensional object. The photopolymer according to a selected cross-section of transferable binder image, containing heat fusible that object. Areas exposed to the UV laser are materials, is then transferred to the layer of bodypolymerized and solidified to form a layer of solid building material, melted, and allowed to permeate plastic at or just below the surface. The completed therethrough. Thereafter, the molten binder is layer is then lowered into the liquid UV-curable hardened by cooling it to a temperature below its photopolymer and covered with a new layer of said melting point. As the molten binder material liquid polymer and the laser shining step repeated for solidifies, it bonds body-building material around it the generation of the next layer and, so on, until all together to form a first cross-section of the three- the layers that make up the desired object is obtained. dimensional object. Areas free of the binder material

Another alternative approach is described in U.S. remain unbonded and stay as support material for Pat. No. 5,204,055. Powdered base material, such as a subsequent layers. After that, a second layer of bodypowdered ceramic or a powdered plastic is deposited building powder material is deposited on the first in sequential layers one on top of the other. Liquid layer and the step of generating and transferring a binder material is then selectively supplied to the binder powder image is repeated to form a second layer of powdered base material using an ink-jet layer of the three-dimensional object. Subsequent printing technique to bond the powdered base layers are formed in the same manner to produce the material together in accordance with a computer three-dimensional object.

model of the three-dimensional object being formed. The method and apparatus disclosed in U.S. Pat. When all the layers composing the object are formed, No. 6,376, 148 has several advantages. For one, the unbounded powder is removed, resulting in the method builds three-dimensional objects more formation of the desired three-dimensional object. quickly than prior art systems as each layer of the

The examples described hitherto, as well as object is built wholly whereas most prior art systems many other systems that are in commercial use, are build objects in a point-by-point fashion. Also, the essentially point-to-point processes whereby three- method has the advantage of being able to use a board dimensional objects are formed bit by bit, therefore array of materials, including both organic and the speed at which layers are formed is slower than if inorganic substances as well as their mixtures, as the the layers are formed layer-by-layer. In view of this primary body-building powder. In contrast, some problem, there is considerable effort directed to prior art systems like the one described hereinbefore designing systems which form three-dimensional with reference to U.S. Pat. No. 4,575,330, can use objects layer-by-layer instead of bit by bit. U.S. Pat. only one type of build material - photo-curable liquid No. 6,066,285, for example, discloses a method of resins. Further, numerous prior art solid freeform fabrication of a three-dimensional electrophotographic printing based systems, such as object using layer-by-layer deposition of at least one the one described herein with reference to U.S. Pat. type of powder by electrophotographic printing. In an No. 6,066,285, shape each body-building layer via electrostatic attraction of the body-building powder not provide a process or apparatus which allows material to the imaging member in an image-wise conductive materials, including all types of metals, to manner responsive to the electrostatic latent image be used as the binder. Thus, the selection of binder thereon. The amount of material that can be deposited material is limited to non-conductive ones, such as on the imaging member is dependent on the strength polymeric materials which, relative to metals and of the attractive force exerted by the imaging member ceramics, have lower strength. Also, the service on the body-building powder material which is temperatures of polymeric materials are limited to a dependent on the charge potential of the surface of few hundred degree Celsius beyond which, softening the imaging member. Therefore, should adjustment to of thermoplastic polymers or degradation of the thickness of the body-building material layer be thermosetting polymers will occur. Accordingly, the desired, the imaging member must be charged to a mechanical strength, heat resistance and other different level than usual. However, electrical properties of said objects are dependent on those of discharge from the imaging member, in the form of the binder regardless of the body-building material sparks, may occur if the voltage potential of said used as the binder is solely responsible for holding imaging member is increased to the point of air the three-dimensional objects together.

breakdown or ionization of air. Accordingly, the While improvements have been made in the amount of body-building material that can be process, apparatus and materials for the development deposited in each layer forming step is limited. By of three-dimensional objects, there continues to be a contrast, the method and apparatus disclosed in U.S. need for processes and apparatus which will improve Pat. No. 6,376, 148 does not have this shortcoming as the quality of the completed objects, are easy to use, it performs the layer forming step, in two separate simple in design, and cheap to purchase and run. In steps, wherein the first is the deposition of the bodyparticular, there is a need for a process, where three- building powder material by conventional powder dimensional objects are formed layer-by-layer. Also, dispensing means and the second is the deposition of there is a need for a process, which is able to use a the binder material by electrophotographic printing. board array of materials, including both organic and As such, thicker layers can be produced since a big inorganic substances as well as their mixtures, as the portion of the materials needed in each layer is base material. Further, there is a need for the deposited in the first step, with the remaining coming provision of a process for forming three-dimensional from the second. objects based on electrophotographic printing, where

Another advantage associated with this method deformations found in completed three-dimensional and apparatus is that the step of generating support objects caused by spillover effects of the building structures for objects with features that are not self- process are minimized by implementing a holistic supporting, like undercuts or overhangs, is approach in process planning. Additionally, there is a unnecessary, as unbonded body-building powder need for a process for forming three-dimensional material adjacent those that are bonded to form the objects based on electrophotographic printing, where three-dimensional objects, is retained in their original either conductive or non-conductive materials are position throughout the build process and forms a used as the filler material, so that the selected filler natural support system for the objects that are being has physical and chemical properties that are built. Lastly, the invention provides an apparatus that, compatible with the base material, and there is through the use of mature technologies, including that obtained three-dimensional objects possessing of electrophotographic printing, is simple in design, attributes that are comparable to those produced by efficient, and economical. conventional manufacturing techniques, such as die-

However, problems with the invention of U.S. casting or CNC machining. Also, there is a need for a Pat. No. 6,376,148 do exist. In order to bond loose process, where the base powder is dispensed in such a body-building powder material to form three- manner that those not bonded during the build dimensional objects, heat is applied to a binder process, remain in the work space and serves as a material containing heat fusible materials by heat support structure for ensuing layers.

sources positioned near the object building zone to

melt the binder, and cause it to permeate the bodySUMMARY OF THE INVENTION building powder layer. The step of applying the heat

must be carefully modulated so that the heat applied It is therefore a feature of the present invention to to one layer of powder is not transmitted to other provide a process of building three-dimensional layers beneath, otherwise the binder material that had objects based on electrophotographic printing which solidified in preceding layers may re-melt and flow in overcomes the above-noted disadvantages.

a random manner into surrounding regions, including It is a further feature of the present invention to layers below. Consequently, layers adversely affected provide a process, wherein layers that constitute the by the heat will lose their definition and result in three-dimensional objects are formed layer-by-layer defonned objects. and not point-by-point.

Another disadvantage associated with the An additional feature of the present invention is invention of U.S. Pat. No. 6,376,148 is that it does the provision of a process, which allows the use of a board array of materials, including both organic and FIG. 2A - 2F are schematic views of different inorganic substances as well as their mixtures, as the stages of forming a three-dimensional object in base material. accordance with the present invention.

Another feature of the present invention is the FIG. 3 is a schematic view of another provision of a process with the flexibility to form embodiment of the process of the present invention. layers constituting the three-dimensional objects with FIG. 4 is a schematic view of a further different thickness, so that the most appropriate embodiment of the process of the present invention. configuration is selected for a given requirement. In these Figures, like components are indicated

Another feature of the present invention is the by identical reference numerals.

provision of a process, which allows the formation of Illustrated in FIG. 1 is an exemplary embodiment objects with features that are not self-supporting, of the present invention which depicts an apparatus without the need of additionally generating a support for forming three-dimensional objects, while FIG. 2A structure. - 2F show views of different stages of the forming

An additional feature of the present invention is process in accordance with the present invention. As the provision of a process, where either conductive or shown in FIG. 2A - 2D, the substrate 43, supporting non-conductive materials are used as the filler the three-dimensional object 42, is moved beneath a material, so that the selected filler has physical and powder dispensing means 53 to receive a layer of chemical properties that are compatible with the base powdered base material therefrom. The substrate 43, material. surrounded by the walls 48 of the build chamber, is

A further additional feature of the present lowered into a new position to create space 201 at the invention is the provision of an improved process, top of the build chamber to receive said layer of where deformations found in completed three- powdered base material. Surplus powdered base dimensional objects caused by spillover effects of the material 202 is deposited to ensure that the entire building process are minimized. preceding layer is completely and adequately covered

The present invention in one aspect is thus with the powdered base material. The newly directed to a process for building three-dimensional deposited layer of powdered base material is then objects, comprising the steps of depositing a layer of vibrated by a vibrating means, such as a vibrator (not powdered base material onto a substrate; operating an shown), to promote settling thereof. It is preferred imaging device to generate a electrostatic latent that the powdered base material is vibrated to the image on an imaging member having a surface point its volume becomes constant, so that further capable of supporting and transporting filler material, settling and unwanted movement of the powder layer wherein the electrostatic latent image corresponds to is minimized and a stable platform for the deposition data derived from a selected cross-section of the of subsequent layers is provided by the newly three-dimensional object to be built; delivering a deposited layer of powdered base material. Excess filler material to the surface of the imaging member powder is scrapped off by a doctor blade 47.

to form a layer of filler material adjacent the The exemplary apparatus further includes an electrostatic latent image thereon; heating the layer of imaging member 20, which forms a path around a filler material in a heating zone to a pre-determined drive roller 22 and an idler roller 23. The imaging temperature; transferring the layer of heated filler member 20 is rotated in a process direction as material from the surface of the imaging member to indicated by arrow 21, so as to transport the surface the layer of powdered base material to cause said 25 thereof around said path for implementing a series layer of powdered base material to become bonded in of image forming steps in a manner similar to typical regions corresponding to the electrostatic latent electrophotographic printing processes. Imaging image; repeating all the above steps for as many member 20 includes an imaging surface 25 of any times as required to form successive layers that type capable of having an electrostatic latent image constitute the three-dimensional object, said filler formed thereon. An exemplary imaging member 20 material further causing adjacent layers to be bonded may include a typical photoreceptor or other with one another; and removing unbonded material to photoreceptive component of the type known to those cause the three-dimensional object to appear. in the art of electrophotography, that comprises an inner layer composed of an electrically conductive

DESCRIPTION OF THE PREFERRED material with an outer photoconductive layer

EMBODIMENT thereupon. The inner layer of the photoreceptor may be impervious to light, or wholly or partially

These and other aspects of the present invention transparent. Mylar, with an overcoat of indium tin will become apparent from the following description oxide, for example, is suitable as a transparent inner in conjunction with the accompanying drawings in layer for the photoreceptor. Likewise, the which photoconductive layer may be impervious to light, or

FIG. 1 is a schematic view of an embodiment of wholly or partially transparent. Polyvinyl carbazole, the process of the present invention. which is light-transmissive and possesses high dark- resistivity, is suitable as a transparent photoconductive layer, for example. Alternative energy 33 where the filler material thereon is heated embodiments for the imaging member 20 are also thereby. The energy source 33 may include a resistive contemplated by the present invention, including, for heating element, which is exemplified herein, or any example, but not limited to, non-photosensitive other devices capable of suitably heating the filler imaging members such as a dielectric charge material transported on the imaging member. retaining member of the type common in ionographic Examples of devices capable of suitably heating the printing apparatuses or electrode substructures filler material, which is composed of either capable of generating electrostatic latent images. conductive or non-conductive substances, include

Referring to the exemplary embodiment of FIG. cavity magnetrons, which cause heating of dielectric 1, the photoconductive surface 25 of the imaging substances by exciting the molecules thereof with member 20 is advanced to a charging device 15, microwave radiation, and induction coils, which which may include a corona generating device, or any cause heating of conductive substances by inducing other charging apparatus capable of applying an eddy currents in the conductive substances, among electrostatic charge on the surface 25 of the imaging other devices, which are known in the art.

member 20. At the corona generating device, the Once the filler material deposited on the photoconductive surface 25 is charged to a relatively electrostatic latent image formed on the imaging high, substantially uniform potential. Thereafter, the member 20 is heated to a pre-determined temperature, charged surface 25 of the imagmg member is it is transported directly overhead the present layer of advanced to an image generating device 10, which the three-dimensional object 42 being formed. projects a light image corresponding to input data Generally, the spacing between the newly deposited onto the charged photoconductive surface 25 to layer of powdered base material in the build chamber selectively dissipate the charge thereon. An and the imaging member ranges from about 100 μιτι electrostatic latent image is thus formed on the to several millimeters. A discharge lamp 35 floods photoconductive surface 25. The image generating the photoconductive surface 25 of imaging member device 10 may include various optical image 20 from its reverse side with light to dissipate all the formation and projection devices as are known in the electrostatic charge held thereon (FIG. 2E). While art, such as laser 11, which is exemplified herein. discharge lamp 35 is illustrated as shining on the

After the electrostatic latent image is formed on interior of the imaging member 20, it will be the photoconductive surface 25 of the imaging understood that in the case where the imaging member 20, the image is advanced to an image member 20 is impervious to light, the discharge lamp developing device 30 and developed into a visible 35 will be positioned to shine on the exterior of the image by delivering charged filler powdered material imaging member 20. As a large number of closely thereon and allowing the electric fields emanating adjacent filler particles having the same charge from both charged filler powder and electrostatic polarity are originally held on the surface of the latent image to interact and causing said charged filler imaging member 20, an unstable condition thereon is powder to image-wise deposit on the imaging thus created. Owing to the mutual repulsion of these member 20. Generally, any of the large number of particles, a large portion of said particles is ejected imaging developing devices known in the art is from the surface of the imaging member 20 and suitable for delivering and depositing filler material deposits in an image-wise manner on the current layer to the photoconductive surface 25 of the imaging of the three-dimensional object 42 being formed, member 20. Illustrative examples of the imaging thereby causing the powdered base material at such developing devices include magnetic brush systems, regions to become bonded (FIG. 2F). The filler which deposit developing material on the imaging material also causes adjacent layers of the base member 20 by contacting a brush-like mass powder to be bonded with one another.

composed of ferromagnetic material formed by the The repulsion of the charged filler particles from effects of magnetism, and loaded with charged the surface of the imaging member 20 may be developing material, with the imaging member, improved by connecting the inner layer of the powder cloud systems, which deposit developing imaging member 20 to a voltage source 34 equal in material on the imaging member 20 by delivering the polarity to that of the filler particles rather than developing material to the imaging member 20 as a merely grounding the conductive layer. In this spray, so that charged developing material therein are manner, the repulsive force emanating from the attracted to the electrostatic latent image on the conductive inner layer is added to the force of mutual photoconductive surface 25, and cascade systems, repulsion between the filler particles, thereby which transport developing material to the imaging propelling them into the newly deposited layer of member 20 by causing the developing material to base powder with greater velocity and uniformity. traverse the surface 25 of the imaging member 20 in a This may be accomplished by operating a cascading manner. controllable voltage source.

After filler material is deposited on the According to the exemplary embodiment of FIG. photoconductive surface 25 of the imaging member 1, the filler material is heated by a source of energy 20, the imaging member 20 advances to a source of 33 after it is deposited on the photoconductive surface of the imaging member 20 to the energy source, the transfer of the layer of filler material from the imaging member 20 is also exposed to the energy imaging member 20 to the donor platen 54 is carried source during the heating process and heats up. In the out by connecting the donor platen 54 to a voltage case where the imaging member's 20 operating source 34, illustrated herein as a controllable voltage temperature is exceeded, the imaging member 20 may source, opposite in polarity to that of the filler lose its insulating characteristic and become particles, and charging the donor platen 54 to a inoperable. Thus, the present invention contemplates magnitude at least sufficient to overcome the an alternative embodiment to the process of heating attractive electrostatic forces existing between the the filler material whilst it is being transported on the latent electrostatic image and the filler particles. imaging member 20, wherein the effects of the Once the filler material transferred to the donor energy source 33 on the imaging member 20 is platen is heated to a pre-determined temperature, it is minimized. transported directly overhead the present layer of the

Illustrated in FIGS. 3 and 4 are other three-dimensional object 42 being formed. Generally, embodiments of the process of the present invention the spacing between the newly deposited layer of which minimize the effects of the energy source 33 powdered base material in the build chamber and the on the imaging member 20. The operation of the donor platen ranges from about 100 μπι to several process as illustrated in FIG. 3 is substantially millimeters. The controllable voltage source then identical to the operation of the process as illustrated switches to the same polarity as the filler particles. As in FIG. 4. The key difference between the a result of mutual repulsion between the donor platen embodiments as illustrated in FIG. 3 and FIG. 4 being 54 and the filler particles, the filler particles are that a flexible imaging member is provided in the propelled from the surface of the donor platen 54, and former whereas a rigid one is provided in the later. In deposit in an image-wise manner on the current layer these versions of the process of the present invention, of the three-dimensional object 42 being formed, in summary, a first layer of powdered base material is thereby causing the powdered base material at such deposited on a substrate. An imaging member 20 is regions to become bonded. The filler material also operated so as to transport the photoconductive causes adjacent layers of the base powder to be surface 25 thereon for implementing a series of bonded with one another.

imaging forming steps. A charging device 15 charges The heated filler material may cause bonding of the photoconductive surface 25 to a relatively high, the newly deposited layer of powdered base material substantially uniform potential. The imaging member in several ways. In one exemplary embodiment, the 20 then advances to the image generating device 10, filler material is heated until it is partially or where the charges on the conductive surface 25 are completely molten. Also, the base material is selected selectively dissipated to form a latent electrostatic so that its melting point is the same as or less than the image thereon. An image developing device is, in boiling point of the filler material. Accordingly, once turn, operated to develop the latent electrostatic the filler material comes into contact with the layer of image into a visible image by depositing powdered powdered base material, it permeates into the gaps filler material on the imaging member in an image- existing in between the particles thereof. As the wise manner. As contrasted to FIG. 1, the imaging temperature of the molten filler material is the same member 20 is not used to transport the newly as or higher than the melting point of the base developed layer of filler material thereon to the material, the outermost layer of the particles of the energy source 33. Instead, a heat-resistant donor base material melts, and upon solidification, member 54, illustrated herein as a platen, is used to coalesces at their contacting surfaces. The filler transport the layer of filler material to the source of material is incorporated into the final component. energy 33, where the layer of filler material is heated In the above-described process, the image-wise to a pre-determined temperature, after receiving the bonding of the newly deposited layer of powdered layer of filler material from the imaging member 20. base material is accomplished by the melting and While the donor member 54 is illustrated herein as a subsequent coalescence of the base material. Thus, platen, other configurations, such as a roll, or a the selection of base materials is limited to those with continuous flexible belt, is also contemplated by the a melting point that is less than or the same as the present invention. Additionally, the donor member is boiling point of the filler material. To expand the comprised of any material, or combination of range of materials that can be selected as the base materials, which allow(s) the donor member to be material, the present invention contemplates an charged to a desired polarity, either positive, or alternative embodiment to the bonding process via negative, and magnitude. Preferably, the donor coalescence of the base material described member comprises a conductive inner layer with an hereinabove, wherein no melting of the base material overcoat of an insulating material. This particular is required. In this alternative embodiment, the configuration is useful in preventing charges from image-wise bonding of the newly deposited layer of flowing between the filler particles and the donor powdered base material is carried out using only the member ^" 54, so that the filler particles will remain filler material. This embodiment operates in a manner similar to the above-described embodiment, wherein electrostatic latent image on the imaging member 20, the filler material is either partially or completely so that the filler particles are electrostatically melted and allowed to permeate the newly deposited propelled to the newly deposited layer of base layer of powdered base material. However, the base powder. After the filler particles are transferred to the material is not melted and the bonding thereof is newly deposited layer of base powder, the imaging provided by the solidification of the filler material. member 20 is flooded with light to dissipate the latent

After the filler material is transferred from the electrostatic image thereon to prevent the image from photoconductive surface of the imaging member 20 interfering with the newly formed layer of base and to the newly deposited layer of base powder, some filler powders.

residual particles inevitably remain adhering thereto. Materials suitable for the base material may These residual particles are removed from the include, for example, but not limited to, metals, photoconductive surface at cleaning station 50. The ceramics, polymers and composites. Examples of particles are cleaned from the photoconductive metals include ferrous metals, non-ferrous metals, surface by the rotation of brush 51 and 52 in contact their alloys and superalloys such as carbon steels, therewith. Subsequent to cleaning, a discharge lamp stainless steels, aluminum alloys, titanium alloys and (not shown) floods the photoconductive surface of the the like. Examples of ceramics include oxide imaging member 20 with light to dissipate any ceramics, carbides, and nitrides such as alumina, residual electrostatic charge remaining thereon prior silicon carbide, titanium nitride and the like. to the charging thereof for the next successive Examples of polymers include thermoplastic imaging cycle. polymers and thermosetting polymers such as

All the above steps are repeated for as many acrylics, ABS, polyamides, polyethylene and the like. times as required to form successive layers that Materials suitable for the filler material included constitute the three-dimensional object. After the metals with low-melting point and thermoplastic three-dimensional object is completed, unbonded polymers. Metals with low-melting point include material is removed to cause the three-dimensional alloys of tin and lead.

object to appear. Many possible combinations of base and filler

The present invention contemplates the use of materials can be selected according to the present either conductive or non-conductive materials as the invention. For example, metal powders can be filler material. Generally, the various known image bonded with either thermoplastic polymers or metals; developing systems that are extensively used in ceramic powders can be bonded with thermoplastic electrophotographic devices, including those polymers; and thermoplastic polymeric powders can described hereinabove, employs non-conductive be bonded with thermoplastic polymers.

developing material, which is normally charged by Other modifications of the present invention will triboelectric charging. When it is desired to utilize occur to those skilled in the art upon reading of the conductive filler material, the filler material may be present disclosure. These are intended to be included charged by, for example, induction, using the within the scope of the present invention.

development methods as described in U.S. Pat. No.

3, 166,432. To transfer conductive filler material from

the surface of the imaging member 20 to the newly

deposited layer of base powder, the method described

hereinabove, wherein the transfer is carried out by

flooding the photoconductive surface 25 with light to

dissipate the electrostatic charge found thereon, so

that charged filler particles eject from the surface of

the imaging member 20 as a result of mutual

repulsion, cannot be followed. The photoconductive

surface 25 becomes conductive when exposed to

light, which causes the charged conductive filler

particles thereon to lose their charge. Once the

conductive filler particles are neutralized, the

repulsive force existing between the filler particles is

also lost, and the filler particles may continue

adhering to the surface of the imaging member 20

due to van der Waals forces. Thus, to transfer

conductive filler material from the surface of the

imaging member to the newly deposited layer of base

powder, the imaging member 20 is electrically biased

by a voltage source 34 to the same polarity as that of

the filler material, and to a magnitude greater than

that of both the image and non-image areas of the