Data processing: structural design – modeling – simulation – and em – Simulating nonelectrical device or system
Reexamination Certificate
2001-05-03
2004-11-02
Thomson, W. D. (Department: 2123)
Data processing: structural design, modeling, simulation, and em
Simulating nonelectrical device or system
C703S001000, C703S002000, C700S120000, C700S119000, C264S401000, C264S040100, C118S620000
Reexamination Certificate
active
06813594
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates in general to algorithms for use in forming three-dimensional objects by solid freeform fabrication techniques such as stereolithography. In particular, the present invention relates to an improved algorithm capable of automatically detecting geometrical configurations of an object that require special build parameters and automatically selecting those parameters for a range of Z-values without intervention by the operator.
2. Description of the Prior Art
Many algorithms have been proposed previously to control the forming of a three-dimensional object in a layer by layer manner by solid freeform fabrication techniques. Some solid freeform fabrication techniques, herein referred to as SFF, include stereolithography, laminated object manufacturing, selective phase area deposition, multi-phase jet solidification, ballistic particle manufacturing, fused deposition modeling, particle deposition, laser sintering, and the like. One recent algorithm is disclosed in U.S. Pat. No. 6,159,411 to Kulkarni et al. wherein a style wizard determines a general build style for a three-dimensional object to be formed in response to answers to a series of questions by an operator. The objective of the algorithm is to simplify the selection process as much as possible in order to prevent or eliminate operator error in deriving build parameters for the three-dimensional object.
A three-dimensional object formed according to improperly selected build parameters often results in an unacceptable part. In stereolithography, sometimes the object collapses on itself during the build process or the recoater blade tears up sections of the object creating a plurality of strings of solidified material in the resin vat. Such failures not only waste operation time, but also create additional maintenance time, as the solidified material floating in the resin vat must be removed. Eliminating object collapses and failures is highly desirable.
Build failures not only occur due to the improper selection of a general build style for the three-dimensional object, but also due to failure to identify special geometric features on the object that may require unique parametric treatment prior to building. Generally, these special geometric features cannot be built successfully by the default values of general build style parameters and require special build parameters to be assigned. Undesirably, the operator must identify these special geometric features before the object is formed to assign the special build parameters, and if missed, build failure typically occurs.
There are currently four categories of special geometric features, or special build types that, when present, need to be identified on an object to be formed by stereolithography. These special build types are 1) Trapped Volumes, (2) Large Flat Up-facing Surfaces, (3) Near Flat Down-facing Surfaces, and (4) Delicate Features. Trapped Volumes and Large Flat Up-facing Surfaces cause problems that are generally solved by adjusting re-coating parameters as discussed in U.S. Pat. No. 5,945,058 to Manners et al. Near Flat Down-facing Surfaces sometimes cause border delamination and layer delamination problems when these features are built by default values of the general build style parameters. These problems can be solved by adjusting build parameters such as those related to support spacing, fill scanning, and border scanning, and the like. Delicate Features can cause problems because the re-coating parameters associated with most general build styles operate too vigorously, often knocking off the delicate feature as it is being built. Slowing down the re-coating parameters, or the like, can solve this problem. Extensive work has been done to develop different parameter sets for each of the special geometric conditions in order to solve their associated problems.
However, in order to properly form objects having any of these geometric configurations present, the operator must manually identify them. These special build types cannot be selected until the data representing the three-dimensional object to be built is imported into the platform and a Z-axis established for building the object prior to slicing. Undesirably, the special geometric features must then be visually identified by the operator who must manually assign one of the special build types to the range of Z-values in which the special feature resides. If the operator is inexperienced or inattentive, the assignment of a necessary special build type can be overlooked, which typically results in build part failure and the generation of long strands of solidified spaghetti-like material in the resin vat.
Although a special build type can be manually assigned to a range of Z-values of an object to be formed, problems can arise when two or more special build types are present within the same range of Z-values. For example, if a trapped volume and a delicate feature are located within the same range of Z-values, only the parameters associated with the last build style assigned will be used. Often, these parameters may not be appropriate in forming the object in the areas where the other special build type exists and can result in part failure. Currently, the only method to overcome this situation is for the operator to manually select each individual build and/or re-coating parameter. Only experienced and skilled operators are able to successfully recognize these conditions and select appropriate parameters. Thus, novice operators cannot successfully build many sophisticated geometric configurations without some trial and error. This is undesirable.
Thus, there is a need to increase the probability of a successful build by reducing the number of manual decisions by the operator to select the build parameters for an object. There is also a need to more fully automate the process of determining all the build parameters necessary to build any three-dimensional object desired.
These and other difficulties of the prior art have been overcome according to the present invention.
BRIEF SUMMARY OF THE INVENTION
The present invention provides its benefits across a broad spectrum of solid freeform fabrication (SFF) techniques. 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 pertaining to stereolithography 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.
It is one aspect of the present invention to eliminate operator error as much as possible when build parameters are selected for forming a three-dimensional object layer by layer by a SFF process such as stereolithography.
It is another aspect of the present invention to automatically identify special build types within a given three-dimensional object to be formed.
It is still yet another aspect of the present invention to automatically assign a set of alternate parameters for each special build type identified in a given three-dimensional object to be formed.
It is a feature of the present invention to identify special build types within a range of Z-values of an object by processing the data descriptive of the object by a computer control system after orienting the object in accordance with a Z-axis.
It is another feature of the present invention to identify more than one special build type within a particular range of Z-values of an object by processing the data descriptive of the object after orienting the object in accordance with a Z-axis.
It is still another feature of the present invention to automatically select alternative parameters within a range of Z-values having more than one special build type identified within the range.
It is an advantage of the pre
Guertin Michelle D.
Manners Chris R.
3-D Systems, Inc.
Curry James E.
D'Alessandro Ralph
Thomson W. D.
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