Large-Diameter Aspheric Lens Milling With Annular Ring Toolpaths
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Solution Overview
Problem
Current methods for machining large-diameter aspheric lenses face challenges such as low efficiency, tool wear, and accuracy issues due to excessively long tool paths and complex error compensation, especially when machining meter-scale surfaces.
Innovation Solution
The method involves discretizing the aspheric surface into a series of equally spaced annular rings with different radii, using an annular grinding wheel tool with a diameter greater than the semi-diameter of the aspheric surface, and machining these rings sequentially, which reduces the number of rings and the increment in the tool path, thereby minimizing residual errors within the machine tool's positioning accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the screw pitch of the tool path is reduced to improve surface quality, then surface roughness is improved, but machining time increases significantly
Solution Approach 1:
The aspheric surface is segmented into multiple zones along the optical axis, with each zone processed by a dedicated tool path segment. This allows the tool to focus on localized areas rather than traversing the entire large-diameter surface, reducing total tool path length while maintaining fine pitch requirements for surface quality in each zone
Solution Approach 2:
The machining approach transitions from a single-plane tool path to a multi-level zonal structure along the optical axis. By adding the axial dimension as a segmentation criterion, the tool path is organized into discrete zones that can be processed independently, reducing the cumulative tool path length required to achieve the entire surface
2Productivity
If the tool path length is reduced to improve machining efficiency, then productivity increases, but tool wear becomes severe
Solution Approach 1:
The tool path is segmented into multiple independent zone segments along the optical axis. Each segment processes a specific axial range with optimized tool motion, preventing excessive cumulative tool wear that would occur in a single continuous tool path while maintaining high machining efficiency through parallelizable zone processing
Solution Approach 2:
The tool path parameters are dynamically optimized for each zonal segment based on local surface characteristics and tool position. This allows adaptive adjustment of cutting parameters within each zone to minimize tool wear while maintaining productivity, rather than using fixed parameters for the entire large-diameter surface
3Device complexity
If conventional small tools are used for machining, then tool path complexity is manageable, but the number of tool changes increases and accuracy decreases
Solution Approach 1:
A single large-diameter ball-end mill tool is designed to process multiple zonal segments of the aspheric surface through programmed motion along the optical axis. This multi-functional tool eliminates the need for multiple tool changes while maintaining positioning accuracy through zonal segmentation, and reduces tool path complexity by using one tool rather than many specialized tools
4Productivity
If the aspheric surface is processed in a single finishing operation, then productivity increases, but surface quality deteriorates due to excessive screw pitch
Solution Approach 1:
The single finishing operation is segmented into multiple zonal finishing passes along the optical axis. Each zone is processed with optimized local tool paths that maintain appropriate screw pitch for surface quality, while the overall process remains efficient by processing zones sequentially rather than requiring multiple complete surface passes
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly improves machining efficiency and accuracy by reducing the number of rings and the distance between them, extending tool life, and simplifying the movement requirements of the machine tool, while maintaining high surface quality.
Implementation Method 1
an annular grinding wheel tool... and machining these rings sequentially
Data Source
AI summary
A method for numerical control milling, forming and polishing of a large-diameter aspheric lens to solve the problems of long time-consuming and severe tool wear in the machining of a meter-scale large-diameter aspheric surface is disclosed. An aspheric surface is discretized into a series of rings with different radii, and the rings are sequentially machined through generating cutting by using an annular grinding wheel tool; the rings are equally spaced, there are a total of N rings, and the width of any ring is jointly determined by the Nth ring, the (N−1)th ring, positioning accuracy, and a generatrix equation of the aspheric lens, and the nth ring has a curvature radius of Rn=sqrt(R02−k*(n*dx)2); and the aspheric surface is enveloped by a large number of rings.