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THREE DIMENSIONAL PRINTING
MATERIAL SYSTEM AND METHOD
This application is a continuation-in-part of U.S. patent application Ser. No. 09/832,309 filed Apr. 10, 2001, now 5 U.S. Pat. No 6,610,429, which is a continuation of U.S. patent application Ser. No. 09/182,295, filed Oct. 29, 1998 and now abandoned, which is a continuation-in-part of U.S. patent Ser. No. 08/707,693, filed Sep. 4, 1996, now U.S. Pat. No. 5,902,441, all of which are incorporated be reference in 10 their entirety for all purposes.
FIELD OF THE INVENTION
This invention relates generally to rapid prototyping tech- 15 niques, and more particularly to Three Dimensional Printing materials and methods.
BACKGROUND
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The field of rapid prototyping involves the production of prototype articles and functional parts, as well as ceramic shell molds for metal casting, directly from computergenerated design data.
Two well-known methods for rapid prototyping include a 25 selective laser sintering process and a liquid binder Three Dimensional Printing process (3DPTM, trademark of Massachusetts Institute of Technology, Cambridge, Mass.). The techniques are similar to the extent that they both use layering techniques to build three-dimensional articles. Both 30 methods form successive thin cross sections of the desired article. The individual cross sections are formed by bonding together grains of a granular material on a flat surface of a bed of the granular material. Each layer is bonded to a previously formed layer to form the desired three-dimen- 35 sional article at the same time as the grains of each layer are bonded together. The laser-sintering and liquid binder techniques are advantageous because they create parts directly from computer-generated design data and can produce parts having complex geometries. Moreover, 3DPTM methods can 40 be quicker and less expensive than conventional machining of prototype parts or production of cast or molded parts by conventional "hard" or "soft" tooling techniques which can take from a few weeks to several months, depending on the complexity of the item. 45
3DPTM methods have been used to make ceramic molds for investment casting, thereby generating fully-functional metal parts. Additional uses have been contemplated for 3DPTM methods.
For example, 3DPTM methods may be useful in design- 50 related fields where the articles may be used for visualization, demonstration and mechanical prototyping. It may also be useful for making patterns for molding processes. 3DPTM methods may be further useful, for example, in the fields of medicine and dentistry, where expected outcomes may be 55 modeled prior to performing procedures. Other businesses that could benefit from rapid prototyping technology include architectural firms, as well as others in which visualization of a design is useful.
A selective laser sintering process is described in U.S. Pat. 60 No. 4,863,538, which is incorporated herein by reference. The selective laser sintering process was commercialized by DTM Corporation. The selective laser sintering process involves spreading a thin layer of powder onto a flat surface. The powder is spread using a tool developed for use with the 65 selective laser sintering process, known in the art as a counter-rolling mechanism (hereinafter "counter-roller").
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Using the counter-roller allows thin layers of material to be spread evenly, without disturbing previous layers. After the layer of powder is spread onto the surface, a laser is used to direct laser energy onto the powder in a predetermined two-dimensional pattern. The laser sinters or fuses the powder together in the areas struck by its energy. The powder can be plastic, metal, polymer, ceramic or a composite. Successive layers of powder are spread over previous layers using the counter-roller, followed by sintering or fusing with the laser. The process is essentially thermal, requiring delivery by the laser of a sufficient amount of energy to sinter the powder together, and to previous layers, to form the final article.
The selective laser sintering process is expensive due to the high cost of the laser and the complexity of the equipment used. In addition, only one laser is used at a time, making it a slow method. In addition, depending on the application, materials are sometimes used in the selective laser sintering method that require special handling or processing facilities.
U.S. Pat. No. 5,204,055, incorporated herein by reference, describes an early 3DPTM method which involves the use of an inkjet printing head to deliver a liquid or colloidal binder material to layers of powdered material. The technique (hereafter "liquid binder method") involves applying a layer of a powdered material to a surface using a counter-roller. After the powdered material is applied to the surface, the ink-jet printhead delivers a liquid binder to the layer of powder. The binder infiltrates into gaps in the powder material, hardening to bond the powder material into a solidified layer. The hardened binder also bonds each layer to the previous layer. After the first cross-sectional portion is formed, the previous steps are repeated, building successive cross-sectional portions until the final article is formed. Optionally, the binder can be suspended in a carrier which evaporates, leaving the hardened binder behind. The powdered material can be ceramic, metal, plastic or a composite material, and can also include fiber. The liquid binder material can be organic or inorganic. Typical organic binder materials are polymeric resins, or ceramic precursors such as polycarbosilazone. Inorganic binders are used where the binder is incorporated into the final articles; silica is typically used in such an application.
One advantage of using an ink-jet print head rather than a laser is that inexpensive printheads are commercially available that have a plurality of spray nozzles used to deliver binder to the powder that are arranged side-by-side in a single print head. In selective laser sintering machines, only one laser, which delivers energy to the powder, is conventionally used. The combination of several spray nozzles increases the speed of liquid binder printing compared to laser-sintering by allowing a wider area to be printed at one time. In addition, the liquid binder printing equipment is much less expensive than the laser equipment due to the high cost of the laser and the high cost of the related beam deflection optics and controls.
However, the liquid binder printing technique has a serious reliability problem associated with the spray nozzles becoming clogged with the binder and/or powder material. Clogging occurs when binders having high levels of suspended solids are used. The problem with clogging requires frequent interruptions of the build in order to clean the spray nozzle. The clogging problem increases the time and labor required to build parts and to maintain the equipment. Therefore, although the liquid binder printing technique represents an advance in speed and cost over the selective laser sintering process, it suffers from reliability problems
that slow down the build rate, increasing labor and equipment maintenance costs. This problem interferes with the potential speed advantage of increased printing capability presented by the plurality of spray nozzles.
In addition to the above-mentioned disadvantages, the 5 powders, especially metallic powders, used in both selective laser sintering and liquid binder techniques present safety issues that render them undesirable for use in an office environment. These safety issues may require special clothing and processing facilities to prevent, for example, skin 10 contact or inhalation of toxic materials. In addition, more expense may be incurred through complying with regulations for the disposal of toxic materials. For these reasons, these techniques do not lend themselves to being used in typical office environments, such as architectural and design 15 firms, or doctors' offices.
U.S. Pat. No. 5,490,962 to Cima discloses solid free-form techniques for making medical devices for controlled release of bioactive agents.
U.S. Pat. No. 5,639,402, to Barlow discloses a method for 20 selectively fusing calcium phosphate particles that are coated, or alternatively mixed with, a polymeric binder material.
SUMMARY 25
The present invention is directed to a three dimensional printing composition having about 10% to about 50% by weight of an adhesive material, 0% to about 20% by weight of a first fibrous component; and 0% to about 80% by weight 30 of a filler.
Another embodiment of the invention is directed to a three dimensional printing composition comprising a particulate material having a mean particle size of about 10 microns and about 300 microns and a soluble adhesive, 35 wherein the adhesive material is up to about 50 percent by weight of the composition.
In another embodiment, a method of three dimensional printing is provided. The method includes providing a three dimensional printing composition comprising a particulate 40 material having about 10%-about 50% by weight of an adhesive material, 0% to about 20% by weight of a first fibrous component, and 0% to about 80% by weight of a filler, and providing instructions for using the three dimensional printing composition. 45
Another embodiment of the present invention is directed to a three dimensional printing composition including a particulate material including plaster, a first adhesive, a second adhesive, and an accelerator.
In yet another embodiment of the invention, a kit for three 50 dimensional printing is provided. The kit includes a three dimensional printing composition and an aqueous fluid, wherein the three dimensional printing composition comprises a particulate material including plaster and a first adhesive. 55
Other advantages, novel features, and objects of the invention will become apparent from the following detailed description of non-limiting embodiments of the invention when considered in conjunction with the accompanying drawings, which are schematic and which are not intended 60 to be drawn to scale. In the figures, each identical or nearly identical component that is illustrated in various figures typically is represented by a single numeral. For purposes of clarity, not every component is labeled in every figure, nor is every component of each embodiment of the invention 65 shown where illustration is not necessary to allow those of ordinary skill in the art to understand the invention. In cases
where the present specification and a document incorporated by reference include conflicting disclosure, the present specification shall control.
BRIEF DESCRIPTION OF THE DRAWINGS
Preferred non-limiting embodiments of the present invention will be described by way of example with reference to the accompanying drawings, in which:
FIG. 1 is a graph of the relationship between plaster strength and water content of a plaster;
FIG. 2 illustrates schematically a first layer of a mixture of particulate material of the invention deposited onto a downwardly movable surface on which an article is to be built, before any fluid has been delivered;
FIG. 3 illustrates schematically an ink-jet nozzle delivering an activating fluid to a portion of the layer of particulate material of FIG. 2 in a predetermined pattern;
FIG. 4 illustrates schematically a view of a final article made from a series of steps illustrated in FIG. 3 enclosed in the container while it is still immersed in the loose unactivated particles; and
FIG. 5 illustrates schematically a view of the final article from FIG. 4.
DETAILED DESCRIPTION
The present invention relates to a 3DPTM material system comprising a mixture of an aqueous fluid and a particulate material that includes plaster. The aqueous fluid contains water that hydrates the plaster contained in the particulate material, to form an essentially solid article. Various processing aids may be added to either the particulate material, the aqueous fluid, or both, including, but not limited to, accelerators, adhesives, flowrate enhancers, humectants, and visible dyes. The present invention also relates to a method of using such a materials system, and to an article made by the method of the invention. The material system and method of the invention may be used to manufacture both appearance models and small numbers of functional parts in an office environment, including prototype articles, but is not limited to the formation of prototype articles. "Prototype article," as used herein, is meant to define a relatively easily produced model, such as a bone, or a representation of a production part, such as a gear, bearing, shaft, etc., made of material completely different from that which the production part is made, for purposes of simplicity, speed, and economy. Rapid prototyping, generally, is known in the art.
Plaster is frequently called "Plaster of Paris," a name derived from the earths of Paris and its surrounding regions, which contain an abundance of the mineral gypsum, from which Plaster of Paris is manufactured. Plaster is also referred to by many other names, including, but not limited to, sulphate of lime, semihydrate of calcium sulfate, casting plaster, gypsum plaster, hydrated sulphate of lime, hydrated calcium sulphate, and dental plaster, as well as a variety of trade names. The term "plaster," as used herein, is meant to define any variety of material including a substantial amount of CaS04.%H20 that is in powder form prior to the application of an aqueous fluid. The terms "hydrated plaster" and "set plaster" are used interchangeably herein, and are meant to include any variety of plaster that includes a substantial amount of CaS04.2H20 after setting, or rehydration. Many varieties of plaster are commercially available, varying, for example, in structural strength, the time required for setting, and in volume changes that occur during the setting. Typically, commercially available plasters include other ingre
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