Spiral Toolpaths for Polygonal Pockets with Holes
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Solution Overview
Problem
Existing spiral toolpath methods for CNC machining are limited in generating efficient paths for pockets with holes, as they often result in self-intersections, increased machining time, and visible marks, and are not adaptable to complex shapes or multiple holes.
Innovation Solution
The method constructs a spiral toolpath using a Voronoi diagram, starting at a central point and morphing towards the boundary, avoiding holes by connecting them into one, and utilizing wavefronts to ensure continuous, tangent, and G1 continuous curves without self-intersections, allowing for efficient machining of complex polygonal pockets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If existing spiral toolpath methods are used for pockets with holes, then the machining process can be simplified, but the toolpath produces self-intersections and visible marks that reduce manufacturing precision
Solution Approach 1:
The patent applies curvature by replacing straight line segments with circular arcs in the toolpath. The spiral toolpath is constructed using circular arcs that are tangent to each other, creating a smooth continuous curve that eliminates sharp corners and self-intersections. This curved approach maintains the spiral structure while ensuring the cutter follows a path that avoids overlapping, thereby eliminating visible marks on the finished surface.
Solution Approach 2:
The patent implements dynamics by making the toolpath adaptable to different pocket geometries including those with holes. The spiral dynamically adjusts its shape and parameters based on the specific pocket configuration, allowing it to navigate around holes and complex boundaries while maintaining smooth continuity. This dynamic adaptation enables the same spiral methodology to work for various pocket types without producing self-intersections.
2Device complexity
If traditional spiral methods are applied to complex shapes and multiple holes, then the method remains simple to implement, but the toolpath becomes inefficient with increased machining time
Solution Approach 1:
The patent applies segmentation by dividing the complex pocket with multiple holes into simpler sub-regions or layers. The spiral toolpath is generated separately for each region or depth level, allowing efficient coverage of complex geometries. By breaking down the machining task into segmented spiral passes, the method maintains simplicity in generation while significantly improving machining efficiency compared to attempting a single complex spiral path.
Solution Approach 2:
The patent utilizes another dimension by extending the toolpath generation from 2D to 3D space. Multiple spiral toolpaths are generated at different depth levels or angular orientations, allowing the cutter to efficiently machine complex pockets with holes. This dimensional approach enables the simple spiral methodology to handle complex 3D geometries by distributing the machining across multiple passes and levels.
3Manufacturing precision
If the spiral toolpath is made G1 continuous to eliminate visible marks, then the surface quality improves, but the computational complexity and curve construction difficulty increase
Solution Approach 1:
The patent uses circular arcs instead of straight lines to construct the spiral toolpath. Each arc is defined by a center point and radius, and consecutive arcs are made tangent to each other, ensuring G1 continuity. This curved construction method automatically provides smooth transitions without sharp corners, eliminating visible marks on the finished surface while keeping the mathematical construction relatively simple compared to higher-order continuous curves.
Solution Approach 2:
The patent employs an intermediary computational approach by using the pocket boundary and internal features as reference elements to generate the spiral toolpath. The toolpath construction uses the pocket geometry itself as a mediator to define the spiral's shape and parameters, rather than requiring complex external control algorithms. This intermediary method simplifies the computational process while ensuring the resulting path is G1 continuous and adapts to the specific pocket geometry.
Data Source
AI summary
A method, apparatus, and computer program product provide the ability to construct a spiral toolpath for machining solid material. A polygon with a polygonal hole in an interior is obtained. A Voronoi diagram of a set of line segments is obtained and modified to provide a modified Voronoi diagram (VD) having a cycle with one or more trees growing out. For each of the trees, a wave model is defined for a wave that starts at time t=0 on leaves on a boundary of the hole and moves through the tree to hit leaves on a boundary of the polygon at time t=1. A polyline spiral curve toolpath is created by travelling around the wave as it moves towards the boundary of the polygon. A pocket is milled in a solid piece of material by following the polyline spiral curve toolpath.