Plastic and nonmetallic article shaping or treating: processes – Disparate treatment of article subsequent to working,... – Effecting temperature change
Reexamination Certificate
2000-10-26
2003-06-03
Tentoni, Leo B. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Disparate treatment of article subsequent to working,...
Effecting temperature change
C264S308000, C264S334000
Reexamination Certificate
active
06572807
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates in general to solid freeform fabrication and, in particular, to a method of producing an improved downward facing surface condition on parts produced by selective deposition modeling techniques.
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”. In SFF, complex parts are produced from a modeling material in an additive fashion as opposed to traditional fabrication techniques, which are generally subtractive in nature. For example, in traditional 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, layer by layer, in order to build a complex part. Generally, SFF technologies such as stereolithography and the like utilize a computer graphic representation of a part and a supply of a building material to fabricate a part in successive layers. The building material is typically a powder, liquid, or gas. SFF technologies have many advantageous over conventional manufacturing methods. For instance, SFF technologies dramatically shorten the time to develop prototype parts. They also eliminate the need for complex tooling and machining associated with conventional manufacturing methods. In addition, SFF technologies substantially eliminate the production of waste material compared to conventional manufacturing methods.
One category of SFF that has recently emerged is Selective Deposition Modeling, herein referred to as “SDM”. In SDM, which is also referred to as solid object imaging, a solid modeling material is physically deposited in successive fashion to form an object. In one type of SDM technology the solid modeling material is extruded as a continuous filament through a resistively heated nozzle. In yet another type of SDM technology the solid modeling material is jetted or dropped in discrete droplets in order to build up a part. Often, 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 the ink jet printers. One type of SDM process utilizing ink jet print heads is described in, for example, U.S. Pat. No. 5,555,176 to Menhennett, et al.
Although all SFF methods have many advantages compared to conventional fabrication methods, they also have inherent problems routed in the layer by layer building process. One of the most fundamental problems associated with SFF processes is the adverse effects resulting from gravitational forces that undesirably act on a part during the build process. All SFF processes must deal with gravitational forces. For example, most downward facing surfaces built by SFF processes need to be supported in order to stabilize the part during the building process. There have been many attempts to counter the undesirable effects of gravity on SFF methods, however, with less than optimal results.
One method of countering the gravity problem is to utilize dissimilar materials in the building process. In one approach a dissimilar material is utilized to produce the support structures that support the part during the build process. For example, two different solidifying materials can be selectively deposited in a layer by layer process, one material for building the part and the other material for building the support structure. Ideally, the materials are carefully selected to order to establish a weak bond joint at their juncture such that the application of an applied force separates the support structure from the part along the joint. For example, this approach is described in U.S. Pat. No. 5,617,911 to Sterett et al. Objet Geometries Ltd., in Rehovot, Israel, is currently developing this approach in conjunction with photopolymer build materials. In another approach the materials are selected such that the material comprising the support structure has a lower melting point than that of the part, and after forming, the temperature of the composite is raised in order to melt out the support structure. This type of approach is described in, for example, U.S. Pat. No. 5,141,680 to Almquist et al. Undesirably, however, the complexity of the material delivery systems is doubled in these approaches in order to account for the delivery of two dissimilar materials.
In yet another approach, a removable support material is deposited in particulate form, such as a powder, that is energized so as to fuse to form the part, with the un-fused powder acting as the support structure. This type of approach is described in, for example, U.S. Pat. No. 5,252,264 to Forderhase et al. Undesirably, however, this approach is limited for use with sintered powder materials and is generally unsuitable in applications utilizing flowable solid modeling materials to build parts.
Another attempt to solve the gravity problem is to provide for the rotation of the part about any axis while the build material is being deposited. This approach is described in, for example, U.S. Pat. No. 6,080,343 to Kaufman et al. Under this approach, the part can be theoretically positioned for optimal alignment with gravity whenever the build material is deposited. Although this approach can eliminate the need to provide a substantial amount of support structures, it cannot eliminate them all, particularly when producing highly complex structures. In addition, integrating a rotational system into an SDM process requires sophisticated equipment, sophisticated controls, and highly trained operators. Thus, rotational SDM systems are often impractical for use in most industries because of their complexity and cost.
Another group of solutions to the gravity problem is to produce structural supports at the same time, and from the same material, as that used to produce the part. The supports are then physically removed after the deposition building process is completed. One such approach produces thin needle like support columns or webs to provide support for downward facing surfaces of the part. For example, this approach is described in U.S. Pat. No. 5,141,680 to Almquist et al. In another approach, break surfaces are established by providing perforations or voids along the locations where downward facing surfaces are to be established. This approach is described in, for example, European Patent Application No. 0655317A1published May 5, 1995. In either approach, it is necessary to forcibly remove the support structures after the SDM building steps are completed. Although these solutions only require the deposition of a single build material, they produce undesirable downward facing surfaces that are rough and jagged. Attempts to improve the appearance of these surfaces have proven problematic because the support structures are strongly fused with the underlying part at their juncture with the downward facing surfaces. Currently, there is no known way to precisely control the surface condition at these junctures during or after severance. After separation, manual cleanup such as scraping, filing, and the like, is often needed in order to improve the appearance of the downward facing surfaces. Undesirably, however, such rework does not achieve the same smoothness and detail as is achieved in forming the upward facing surfaces. As a consequence of the poor surface quality of downward facing surfaces, the parts must be oriented with their most important surfaces facing up prior to being formed by the SDM process. This has proven to be a significant drawback in producing objects under conventional SDM processes.
Thus, there is a need to provide an SDM process capable of establishing downward facing surfaces that have the same surface quality and detail as upward facing surfaces. There is also a need to provide an SDM process t
3-D Systems, Inc.
Curry James E.
D'Alessandro Ralph
Tentoni Leo B.
LandOfFree
Method of improving surfaces in selective deposition modeling does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of improving surfaces in selective deposition modeling, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of improving surfaces in selective deposition modeling will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3158035