Offset Surface Toolpaths for Wrinkle-Free CNC Sheet Forming
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Solution Overview
Problem
Conventional CNC toolpaths generated for certain part geometries, such as those with flat surfaces or saddle shapes, often result in defects like wrinkling and quality control issues during incremental sheet forming (ISF), rendering the 3D parts unusable.
Innovation Solution
The method involves transforming the offset surface of a digital 3D part model from a first topological space to a second embedded space, intersecting it with Z-level planes to generate new contours, and then transforming these contours back to the original space to create a CNC toolpath that avoids initial defects, such as wrinkling, by altering the starting point and sequence of tool movements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional CNC toolpaths are used for parts with flat surfaces or saddle shapes, then the manufacturing process is simple and fast, but the resulting parts contain defects like wrinkling and are of poor quality
Solution Approach 1:
The patent transforms the offset surface from the original 3D Euclidean space to a 4D manifold space by introducing an additional dimensional parameter. This allows the toolpath to navigate complex geometries (flat surfaces and saddle shapes) without self-intersection and wrinkling, as the extra dimension provides additional degrees of freedom for tool movement. The transformation maps the problematic 3D surface into a higher-dimensional space where valid toolpaths can be generated, then projects back to 3D for execution.
Solution Approach 2:
The patent changes the mathematical parameters and coordinate system used to represent the toolpath. By transforming coordinates from standard 3D Cartesian space to a 4D manifold parameterization, the toolpath generation avoids singularities and self-intersections that occur with conventional approaches. This parameter transformation enables the generation of defect-free toolpaths for geometries that are problematic in traditional coordinate systems.
2Reliability
If conventional toolpath generation methods are used, then the process is straightforward, but the toolpaths produce defects such as wrinkling on the manufactured parts
Solution Approach 1:
The patent performs preliminary transformation of the offset surface into a 4D manifold space before generating the toolpath. This pre-transformation step prepares the geometric data in a form that guarantees defect-free toolpath generation, eliminating the need for post-processing or correction of wrinkling and self-intersection defects. The computational complexity is shifted to the preprocessing stage, ensuring reliable manufacturing execution.
Solution Approach 2:
The 4D manifold space acts as an intermediary representation between the original 3D part geometry and the final 3D toolpath. By working in this intermediate 4D space during toolpath generation, the system avoids direct computation in the problematic 3D space, thereby preventing defects. The intermediary space provides a computationally favorable environment for path planning.
Data Source
AI summary
A method for CNC manufacturing is provided. The method includes computer-reading a digital model of a 3D part within a first topological space. An offset surface for the digital model in the first topological space is computer-generated. The offset surface in the first topological space is computer-transformed to a transformed offset surface in a second topological space embedded in the first topological space. A plurality of contours are computer-identified, at which a corresponding plurality of embedded parallel planes intersect the transformed offset surface in the second topological space. The plurality of contours in the second topological space are computer-transformed into a corresponding plurality of transformed contours in the first topological space. A CNC toolpath is computer-generated that traces each of the plurality of transformed contours in the first topological space, the CNC toolpath useable by a CNC machine to manufacture the 3D part.