CAD Trim Surface Shell Generation for Closed Volume Selection
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Solution Overview
Problem
In CAD systems, identifying and selecting desired surfaces among numerous small, potentially overlapping surfaces during trim operations can be confusing and time-consuming, especially when multiple surfaces intersect, leading to tedious and error-prone manual processes.
Innovation Solution
A method for automatic volume generation in CAD systems that involves computing intersecting curves, splitting faces along these curves, merging manifold edges to create expanded shells, and pruning shells with non-boundary edges, while identifying and indicating minimum volumes on a graphical user interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If manual trim surface operation is used, then user can selectively keep or remove surfaces, but the process becomes tedious and error-prone when there are many faces to select or remove
Solution Approach 1:
The system automatically performs volume generation and shell identification without requiring manual user intervention. The CAD system itself identifies and organizes the trimmed surfaces into shells that define volumes, eliminating the need for users to manually select and organize each surface piece.
Solution Approach 2:
The patent replaces the manual mechanical process of selecting and organizing surfaces with an automated computational algorithm. The system uses computer-based geometry processing to automatically identify shells and volumes from trimmed surfaces, substituting human manual operations with automated software processing.
2Manufacturing precision
If many small surfaces are created from intersections, then complete geometric partitioning is achieved, but user confusion increases due to overlap previews in displayed depiction
Solution Approach 1:
The patent segments the complex set of trimmed surfaces into organized shells, where each shell represents a complete closed surface that can form a volume. This hierarchical segmentation groups individual surface pieces into meaningful units, making it easier to understand and manipulate the geometry.
Solution Approach 2:
The patent introduces shells as an intermediary concept between raw trimmed surfaces and final volumes. Shells serve as intermediate structures that organize and connect surface pieces, providing a clear representation that bridges the gap between complex partitioned geometry and usable volumetric data.
3Reliability
If multiple iterations are performed to find all surfaces, then complete volume definition is achieved, but the process becomes time-consuming
Solution Approach 1:
The patent performs preliminary organization of trimmed surfaces into shells immediately after the trim operation, before the user needs to define volumes. This preliminary structuring prepares the data in advance, eliminating the need for multiple iterative attempts to find and organize all surfaces.
Solution Approach 2:
The system provides feedback to the user by displaying the identified shells and their corresponding volumes, allowing the user to verify the automatic identification results. This feedback mechanism ensures completeness while reducing the need for manual iteration, as users can quickly review and confirm the generated structure.
Data Source
Figure 1A~1D
Figure 2A~3C
Figure 4
AI summary
An automatic volume generation method during trim setting of a modeled object receives geometric data for intersecting faces, computes intersecting curves, splits the faces along the curves, and merges manifold edges to create expanded shells. Shells with non-boundary edges are pruned, and minimum volumes formed by the pruned shells are identified and indicated on a graphical user display.