Editable B-Rep Conversion for 2.5-Axis CNC Geometry
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Solution Overview
Problem
Current CAD software limitations in generating 3D geometry for 2.5-axis subtractive manufacturing, as they often require manual intervention and are inefficient in handling discrete height layers and milling directions, leading to increased CAM programming time and potential manufacturing issues like undercuts and thin shelves.
Innovation Solution
A boundary-based generative design process that uses level-set methods to produce 3D models with discrete height layers aligned with 2.5-axis manufacturing constraints, allowing for automatic detection of milling directions and height layers, and conversion of models into editable boundary representation formats for efficient CNC machining.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If current CAD software is used to generate 3D geometry for 2.5-axis subtractive manufacturing, then manual intervention is required and CAM programming time increases, but the software can handle basic modeling operations
Solution Approach 1:
The system performs preliminary detection of milling directions and automatic generation of discrete height layers during the design phase, preparing the geometry in advance for 2.5-axis manufacturing. This preliminary action eliminates the need for manual CAM programming adjustments and reduces programming time by having the geometry ready in the correct format before manufacturing begins.
Solution Approach 2:
The generative design process automatically detects milling directions and generates appropriate height layers without requiring manual intervention. The system serves itself by integrating the manufacturing constraints directly into the geometry generation process, eliminating the need for separate manual CAM programming steps.
2Manufacturing precision
If manual intervention is used to adjust geometry for discrete height layers, then manufacturing precision can be maintained, but productivity decreases and CAM programming time increases
Solution Approach 1:
The system automatically detects milling directions and generates discrete height layers during the generative design process itself, rather than requiring post-processing adjustments. This preliminary action ensures geometry alignment with manufacturing constraints is built-in from the start, maintaining precision while eliminating time-consuming manual CAM programming steps.
Solution Approach 2:
The system changes the parameter representation from continuous surfaces to discrete height layers automatically during geometry generation. By modifying how the geometry is parameterized at the design stage, the system maintains manufacturing precision while improving productivity through automation.
3Adaptability or versatility
If continuous surfaces are used in generative design, then design flexibility is maximized, but compatibility with 2.5-axis subtractive manufacturing processes decreases
Solution Approach 1:
The system automatically transforms the parameter representation from continuous surfaces to discrete height layers during the generative design process. This parameter change maintains design flexibility by allowing exploration of various geometries while ensuring the output is compatible with 2.5-axis manufacturing processes that require discrete height layers.
Solution Approach 2:
The system performs preliminary conversion of continuous surfaces to discrete height layers during geometry generation, preparing the design for manufacturing before the modeling process completes. This preliminary action ensures manufacturing compatibility is built-in while preserving design flexibility throughout the generative process.
4Productivity
If B-Reps are sampled and replaced with volumetric representations for generative design, then computational efficiency improves, but ease of editing in CAD programs decreases
Solution Approach 1:
The system performs preliminary conversion of volumetric representations back to boundary representation format during or after the generative design process. This preliminary action ensures the final geometry is in a CAD-editable format, maintaining computational efficiency during generation while restoring ease of editing for subsequent modifications.
Solution Approach 2:
The system uses an intermediary conversion process that translates between volumetric representations (for computational efficiency) and boundary representations (for CAD editing). This intermediary step allows the system to benefit from computational efficiency during generative design while maintaining full CAD editing capability when needed.
Data Source
AI summary
Methods, systems, and apparatus, including medium-encoded computer program products, for computer aided design of physical structures using data format conversion (e.g., of output(s) from generative design processes) and user interface techniques that facilitate the production of 3D models of physical structures that are readily usable with 2.5-axis subtractive manufacturing, include: modifying smooth curves, which have been fit to contours representing discrete height layers of an object, to facilitate the 2.5-axis subtractive manufacturing; preparing an editable model of the object using a parametric feature history, which includes a sketch feature, to combine extruded versions of the smooth curves to form a 3D model of the object in a boundary representation format; reshaping a subset of the smooth curves responsive to user input with respect to the sketch feature; and replaying the parametric feature history to reconstruct the 3D model of the object, as changed by the user input.