Patent Application
20070063366
1. Field of the Invention
The invention relates in general to a system and a method for reliably collecting for removal the by-product waste stream generated from a solid deposition modeling process. In addition, the system can be integrated with a sealed waste removal system wherein reactive materials can be employed without special handling procedures.
2. Description of the Prior Art
Recently, several new technologies have been developed for the rapid creation of models, prototypes, and parts for limited run manufacturing. These new technologies can generally be described as solid freeform fabrication, herein referred to as “SFF”. Some SFF techniques include stereolithography, selective deposition modeling, laminated object manufacturing, selective phase area deposition, multi-phase jet solidification, ballistic particle manufacturing, fused deposition modeling, particle deposition, laser sintering, and the like. In SFF, complex parts are produced from a modeling material in an additive fashion as opposed to conventional fabrication techniques, which are generally subtractive in nature. For example, in conventional fabrication techniques material is removed by machining operations or shaped in a die or mold to near net shape and then trimmed. In contrast, additive fabrication techniques incrementally add portions of a build material to targeted locations, typically layer by layer, in order to build a complex part.
SFF technologies typically utilize a computer graphic representation of a part and a supply of a build material to fabricate the part in successive layers. SFF technologies have many advantages over the prior conventional manufacturing methods. For instance, SFF technologies dramatically shorten the time to develop prototype parts and can quickly produce limited numbers of parts in rapid manufacturing processes. They also eliminate the need for complex tooling and machining associated with the prior conventional manufacturing methods, particularly when creating molds for casting operations. In addition, SFF technologies are advantageous because customized objects can be produced quickly by processing computer graphic data.
There are a wide variety of build materials that are used in various SFF techniques. These materials are typically applied in the form of a powder, liquid, gas, paste, foam, or gel. Recently, there has developed an interest in utilizing highly viscous paste materials in SFF processes to achieve greater mechanical properties. In addition, an interest has recently developed in reproducing visual features such as color on the three-dimensional objects produced by SFF processes. This has produced a need to develop special additives for the build materials along with new dispensing systems to enable the production of these visual features when building the three-dimensional objects.
One category of SFF that has emerged is selective deposition modeling, herein referred to as “SDM”. In SDM, a build material is physically deposited in a layerwise fashion while in a flowable state and is allowed to solidify to form an object. In one type of SDM technology the modeling material is extruded as a continuous filament through a resistively heated nozzle. In yet another type of SDM technology the modeling material is jetted or dropped in discrete droplets in order to build up a part. In one particular SDM apparatus, a thermoplastic material having a low-melting point is used as the solid modeling material, which is delivered through a jetting system such as those used in ink jet printers. One type of SDM process utilizing ink jet print heads is described, for example, in U.S. Pat. No. 5,555,176 to Menhenneft, et al.
Because ink jet print heads are designed for use in two-dimensional printing, special modifications must be made in order to use them in building three-dimensional objects by SFF techniques. This is generally because there are substantial differences between the two processes, thus requiring different solutions to different problems. For example, in two-dimensional printing a relatively small amount of an ink is jetted and allowed to dry or solidify with a significant interest being given to print resolution. Because only a small amount of material is jetted in two-dimensional printing, the material reservoir for the liquid material can reside directly in the ink jet print head while providing the ability to print numerous pages before needing to be refilled or replaced. In contrast, in SDM utilizing an ink jet printhead, a large amount of normally solid material, such as a thermoplastic or wax material, must be heated to a flowable state, jetted, and then allowed to solidify. Furthermore, in SDM dispensing resolution is not as critical as it is in two-dimensional printing. This is generally because, for each targeted pixel location, the amount of material to be jetted in SDM techniques is substantially greater than the amount to be jetted in two-dimensional printing techniques. For example, it may be required to deposit six droplets on a particular pixel location in SDM compared to just one or two droplets in two-dimensional printing. Although the targeting accuracy may be the same, the actual resolution achieved in SDM techniques is generally somewhat less than in two-dimensional printing because the six droplets dispensed may droop or slide towards adjacent pixel locations.
The differences mentioned above are significant and create a number of problems to be resolved. For instance, the amount of material deposited in ink jet based SDM techniques, both in volume and in mass, can be so substantial that it is generally considered impractical to mount a reservoir directly on the ink jet print head to hold all of the material. Thus, it is typical in most SDM systems to provide a large reservoir at a location remote from the print head that is in communication with the ink print head via a material delivery system having a flexible umbilical tube. However, the large container and umbilical tube must be heated to cause at least some of the build material to become or remain flowable so that the material can flow to the dispensing device. Start up times are longer for SDM techniques using ink jet print heads than in two-dimensional printing with ink jet print heads due to the length of time necessary to initially heat the solidified material in the large remote reservoir to its flowable state. In addition, a significant amount of energy is required to maintain the large quantity of material in the flowable state in the reservoir and in the delivery system during the build process. This generates a significant amount of heat in the build environment.
Another problem that is unique to SDM techniques is that the layers being formed must be shaped or smoothed during the build process to establish a uniform layer thickness. Normalizing the layers is commonly accomplished with a planarizer that removes a portion of the material dispensed in the layers. One such planarizer is disclosed in U.S. Pat. No. 6,270,335 to Leyden et al. However, the planarizer produces waste material during the build process that must be handled. This is less of a concern when working with non-reactive materials; however, it is a greater concern when reactive materials are used. For example, most photopolymers are reactive, and excessive contact to human skin may result in sensitivity reactions. Thus, most SFF processes that utilize photopolymer materials require some additional handling procedures in order to minimize or eliminate excessive physical contact with the materials. For example, in stereolithography, operators typically wear gloves when handling the liquid resin and when removing finished parts from the build platform. However, SDM operators who normally handle even non-reactive materials consider additional handling procedures inconvenient and, if possible, would prefer they be eliminated. For reactive materials in SDM systems the issue is compounded and rises above mere inconvenience. Thus, there is a need to provide a material feed and waste system for SDM that can handle reactive materials without requiring the implementation of special handling procedures.
A by-product waste handling system for dealing with the aforementioned waste stream from an SDM process is described in US patent application publication 2005/0017393 A1, entitled “Accumulation, control, and accounting of fluid by-product from a solid deposition modeling process” and assigned to the assignee of the present invention. In that system excess build and support material is removed during the build as a by-product waste and the removal system accumulates, measures, and releases the by-product waste material into a waste receptacle for disposal. Although workable, that system is significantly simplified by the instant invention.
These and other difficulties of the prior art are overcome according to the present invention by providing a new and simpler by-product waste removal system for a solid deposition modeling system.
The instant invention provides its benefits across any SFF process that requires removal of excess build and/or support material during a build. This is done by providing a reliable and lower cost system for removing by-product waste material from a SFF device for forming three-dimensional objects.
It is one aspect of the instant invention to provide an improved by-product waste removal system for SFF systems that overcomes the earlier mentioned disadvantages of prior art systems.
It is another aspect of the instant invention to provide an improved by-product waste removal system for SFF systems that does not require a mechanical transfer system.
It is an advantage that the by-product waste removal system of the present invention is lower in cost, simpler and more effective than prior by-product waste removal systems.
These and other aspects, features and advantages are provided by a method for delivering at least one material and removing waste material in a solid freeform fabrication apparatus to form a three-dimensional object, the method including at least the steps of: delivering material to a dispensing device; dispensing the removed material from the dispensing device in a layerwise fashion to form the three-dimensional object; producing waste material from the dispensed material and depositing the waste material in a waste receptacle, wherein the depositing step comprises flowing the waste material through a heated line to a heated nozzle; releasing the waste material from the heated nozzle to the waste receptacle; and heating the waste material in the receptacle until the three-dimensional object is formed.
The invention also includes a material feed and waste system for a solid freeform fabrication apparatus, the system including at least a means for delivering at least one material to at least one dispensing device; a means for dispensing the discrete amount of material by the dispensing device in a layerwise fashion to form via a plurality of layers a three-dimensional object; a means for normalizing the layers of the three-dimensional object wherein waste material is produced; means for depositing the waste material in a waste receptacle; wherein the means for depositing the waste material comprises: means for flowing the waste material through a heated line to a heated nozzle; means for releasing the waste material from the heated nozzle to the waste receptacle; and means for heating the waste material in the receptacle until the three-dimensional object is formed.
These and other aspects, features, and advantages are achieved according to the method and apparatus of the present invention that employs a unique fluid by-product removal system that automatically and reliably transfers measured amounts of fluid by-product waste material to a final collection container.
These and other aspects, features and advantages of the present invention method and apparatus will become apparent upon consideration of the following detailed disclosure of the invention, especially when it is taken in conjunction with the accompanying drawings wherein:
The present invention provides its benefits across a broad spectrum of SFF processes. While the description which follows hereinafter is meant to be representative of a number of such applications, it is not exhaustive. As will be understood, the basic apparatus and methods taught herein can be readily adapted to many uses. It is intended that this specification and the claims appended hereto be accorded a breadth in keeping with the scope and spirit of the invention being disclosed despite what might appear to be limiting language imposed by the requirements of referring to the specific examples disclosed.
While the present invention can be applicable to other SFF techniques and objects made therefrom, the invention will be described with respect to solid deposition modeling (SDM) utilizing a build material dispensed in a flowable state. However it is to be appreciated that the present invention can be implemented with any SFF technique that requires the continuous or intermittent removal of by-product waste during a build. For example, the build material can be a photocurable or sinterable liquid or powder material that is heated to a flowable state but when solidified may form a high viscosity liquid, a semi-solid, a gel, a paste, or a solid. In addition, the build material may be a composite mixture of components, such as a mixture of photocurable liquid resin and powder material such as metallic, ceramic, or mineral, if desired.
As used herein, the term “a flowable state” of a build material is a state wherein the material is unable to resist shear stresses that are induced by a dispensing device, such as those induced by an ink jet print head when dispensing the material, causing the material to move or flow. Preferably the flowable state of the build material is a liquid state, however the flowable state of the build material may also exhibit thixotropic properties. The term “solidified” and “solidifiable” as used herein refer to the phase change characteristics of a material where the material transitions from the flowable state to a non-flowable state. A “non-flowable state” of a build material, as used herein, is a state wherein the material is sufficiently self-supportive under its own weight so as to hold its own shape. Build materials existing in a solid state, a gel state, a paste state, or a thixotropic state are examples of a non-flowable state of a build material for the purposes of discussion herein. Further, the term “cured” or “curable” refers to any polymerization reaction. Preferably the polymerization reaction is triggered by exposure to radiation or thermal energy.
Most preferably the polymerization reaction involves the cross-linking of monomers and oligomers initiated by exposure to actinic radiation in the ultraviolet or infrared wavelength band. Further, the term “cured state” refers to a material, or portion of a material, in which the polymerization reaction has substantially completed. It is to be appreciated that as a general matter the material can easily transition between the flowable and non-flowable state prior to being cured. However, once cured, the material cannot transition back to a flowable state and be dispensed by the apparatus.
Additionally, the term “support material” refers to any material that is intended to be dispensed to form a support structure for the three-dimensional objects as they are being formed, and the term “build material” refers to any material that is intended to be dispensed to form the three-dimensional objects. The build material and the support material may be similar materials having similar formulations but, for purposes herein, they are to be distinguished only by their intended use.
A preferred method for dispensing a curable phase change material to form a three-dimensional object and for dispensing a non-curable phase change material to form supports for the object is disclosed in U.S. Pat. No. 6,841,116 entitled “Selective Deposition Modeling with Curable Phase Change Materials”, assigned to the assignee of the present invention. A preferred curable phase change material and non-curable phase change support material are disclosed in U.S. Pat. No. 6,841,589 entitled “Ultra-Violet Light Curable Hot Melt Composition”, also assigned to the assignee of the present invention. An SDM system and method using powder is disclosed in U.S. Pat. No. 6,416,850 and a method of using an ink jet printhead to deliver a binder to layers of powdered material is described in U.S. Pat. No. 5,204,055.
Referring particularly to
In the build environment illustrated generally by numeral 13 in
Preferably the materials 23A and 23B of
The dispensing trolley 21 in the embodiment shown in
Beginning with the waste umbilical tube or line 56 in
After vessel 162 empties actuator 164 is activated to move central rod 174 up, closing the bottom seal 172 and opening top vent 176 to vent to the atmosphere to thereby allow vessel 162 to begin refilling for the next cycle.
In the prior art system of
In the prior art system shown in
In conjunction with the curable build material 23A, a non-curable phase change material is used for the support material 23B. Since the support material 23B cannot be cured, it can be removed from the object and build platform, for example, by being dissolved in a solvent. Alternatively the support material 23B can be removed by application of heat to return the material to a flowable state, if desired.
In this prior art system the by-product waste material 58 comprises both materials 23A and 23B as they accumulate during planarizing.
Now referring to
Turning to
In
Beginning with the waste umbilical tube or line 56 in
Waste material receptacle 200, in a preferred embodiment, is a disposable polypropylene bag with a zipper closure that can be easily removed for disposal. It should be recognized that the use of a polypropylene bag is only one embodiment and that other bags or bottles may be employed in the instant invention.
In another embodiment (not shown) a source of actinic radiation could be mounted near waste receptacle 200 to cure the by-product waste material in waste receptacle 200.
In operation the instant invention operates as follows. Referring to
To avoid freezing material collecting on the top of waste receptacle 200 or forming an uneven mound of solidified material in a “stalagmite” or mound-like fashion in the receptacle 200, a heater 194 is positioned either adjacent to or around heated nozzle 198. Heated nozzle 198 and heater 194 are positioned directly above waste receptacle 200. A preferred heater 194 is a ceramic infrared radiant heater. It has also been found that reliable operation with lower energy consumption can be achieved if radiant heater 194 is operated periodically or intermittently rather than full time during a build. Radiant heater ensures the waste material 204 accumulates in a generally flat or even fashion in waste receptacle 200. When waste receptacle 200 is full, or at any desired time prior to commencing a build, the waste material 204 is allowed to solidify or gel and the receptacle 200 is removed from the device 30, discarded and replaced with an empty receptacle.
The resulting waste collection system described above has been found to be fully reliable, simpler in operation, and lower in cost than prior art solutions.
While the invention has been described above with references to specific embodiments thereof, it is apparent that many changes, modifications and variations in the materials, arrangements of parts and steps can be made without departing form the inventive concept disclosed herein. Accordingly, the spirit and broad scope of the appended claims is intended to embrace all such changes, modifications and variations that may occur to one of skill in the art upon a reading of the disclosure. All patent applications, patents and other publications cited herein are incorporated by reference in their entirety.
