Adaptive CNC Tool Paths for Actual Workpiece Shape Variation
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Solution Overview
Problem
CNC machines face challenges in accurately adapting tool paths to actual workpiece shapes, which can lead to inconsistent machining results due to variations between nominal and actual shapes, especially in applications requiring precise depth control on complex surfaces.
Innovation Solution
A method involving the definition of a grid of feature points on the nominal workpiece shape, measurement of these points on the actual workpiece using a probe, and the computation of a space mapping function to transform the CNC machine tool path, ensuring accurate adaptation to the actual workpiece shape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a CNC machine uses a nominal workpiece shape for tool path generation, then the machining process is simple and rapid, but the machining precision deteriorates when actual workpiece shape varies from nominal
Solution Approach 1:
The system performs preliminary measurement of the actual workpiece shape using a probe before generating the tool path. This advance characterization of the workpiece geometry allows the system to pre-compute the appropriate tool path adjustments, eliminating the need for trial-and-error machining and ensuring depth control accuracy from the first pass while maintaining efficient machining speeds
Solution Approach 2:
The system dynamically adjusts tool path parameters based on the measured actual workpiece shape. By computing a transformed tool path that accounts for deviations from the nominal shape, the system modifies cutting depths, positions, and trajectories to maintain consistent machining quality across workpieces with shape variations
2Loss of time
If a probe measures only curves or outlines of the workpiece, then the measurement process is simple and fast, but the manufacturing precision deteriorates due to insufficient shape characterization
Solution Approach 1:
The system segments the workpiece surface into a grid of measurement points, systematically sampling both contour and interior regions. This segmented approach ensures comprehensive shape characterization without requiring exhaustive measurement of every surface point, achieving accurate 3D geometry capture in reasonable time
Solution Approach 2:
The system transitions from 2D contour measurement to 3D surface measurement by incorporating depth information at multiple grid points. This dimensional expansion captures the full three-dimensional shape characteristics, enabling accurate tool path adaptation for complex curved surfaces while maintaining measurement efficiency
3Device complexity
If the tool path is not adapted to the actual workpiece shape, then the device complexity remains low, but the reliability of machining results deteriorates due to shape variations
Solution Approach 1:
The system implements a feedback loop where the probe measures the actual workpiece shape, the control system computes the deviation from nominal geometry, and the tool path is automatically adjusted based on this feedback. This closed-loop approach ensures consistent machining results across workpieces with shape variations without requiring complex manual intervention
Solution Approach 2:
The system creates a digital copy or model of the actual workpiece shape based on probe measurements. This digital replica is then used to generate the adapted tool path, eliminating the need for complex physical fixtures or manual programming while ensuring reliable and repeatable machining results
Data Source
AI summary
A method and system for adapting a CNC machine tool path from a nominal workpiece shape to an actual workpiece shape. The method includes defining a grid of feature points on a nominal workpiece shape, where the feature points encompass an area around the machine tool path but do not necessarily include points on the machine tool path. A probe is used to detect locations of the feature points on an actual workpiece. A space mapping function is computed as a transformation from the nominal feature points to the actual feature points, and the function is applied to the nominal tool path to compute a new tool path. The new tool path is used by the CNC machine to operate on the actual workpiece. The feature points are used to characterize the three dimensional shape of the working surface of the actual workpiece, not just a curve or outline.