Ophthalmic Surface Machining With Discontinuity-Skipping Tool Paths
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Solution Overview
Problem
Existing machining methods for ophthalmic devices with discontinuities face instability and overshoot issues due to insufficient smoothing of the machining kinematic, leading to inaccuracies and surface irregularities when cutting discontinuities.
Innovation Solution
A method involving a determined kinematic for the machining tool with distinct tool path portions, where the cutting edge cuts and jumps over discontinuities at a single feed rate, avoiding material removal before machining the discontinuity, and utilizing a 'air cutting' technique to limit acceleration and prevent overshoots.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the machining tool cuts the discontinuity directly during machining, then the discontinuity is removed, but overshoot phenomena and surface instability occur
Solution Approach 1:
The method applies preliminary action by performing material removal before the machining operation. The discontinuity is removed in a preliminary step, and then the machining tool follows a tool path that jumps over the discontinuity location during the actual machining process, preventing overshoot and surface instability
Solution Approach 2:
The method implements skipping by designing a tool path where the cutting edge jumps over the discontinuity location during machining motions. The tool skips the discontinuity area and does not cut there, avoiding the instability and overshoot phenomena that would occur if the tool attempted to cut through the discontinuity directly
2Ease of manufacture
If the machining kinematic is not smoothed enough, then the machining process is simpler, but overshoots occur on the machined surface
Solution Approach 1:
Instead of smoothing the kinematic to prevent overshoots, the method uses skipping by designing a tool path that jumps over the discontinuity location. This avoids the need for complex kinematic smoothing while preventing surface overshoots, maintaining process simplicity while improving surface quality
Solution Approach 2:
The method extracts the discontinuity from the machining process by removing it in a preliminary material removal step. This separates the discontinuity handling from the main machining operation, allowing the tool path to skip over the discontinuity location without requiring complex kinematic smoothing
3Manufacturing precision
If the cutting edge jumps over the discontinuity during machining, then overshoot is avoided, but the tool path becomes more complex
Solution Approach 1:
The method implements skipping with a relatively simple tool path design. The tool path includes motions that jump over the discontinuity location and a final motion that returns to continue machining. This skipping approach achieves high surface accuracy without requiring excessively complex tool path planning
Data Source
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AI summary
The disclosure provides a method for manufacturing an ophthalmic device, comprising a machining step (110) to provide a predetermined surface (50) on a part and which corresponds to an initial ophthalmic surface having at least one discontinuity (55, 55a-c), the machining step being carried out according to a determined kinematic of a machining tool (27) which is function of the initial ophthalmic surface, wherein the kinematic comprises at least a first tool path portion in which a cutting edge of a machining tool cuts at least a portion of the discontinuity during a first motion on the predetermined surface, and at least a second tool path portion in which the cutting edge of the machining tool jumps over and is remote to the discontinuity during a second motion on the predetermined surface, and the kinematic is carried out with a single feed rate during both first and second motions.