Retroreflective Mold Finishing With Oscillating Blade Motion
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Solution Overview
Problem
Existing methods for manufacturing molds for retroreflective elements, such as corner cubes, face challenges in achieving high accuracy and efficiency, especially when segment sizes are smaller than 1 millimeter, leading to increased machining costs and deteriorated optical performance.
Innovation Solution
A method involving multi-axis machine tools with a blade portion that moves towards the vertex of a polygonal face while oscillating, with specific cutting parameters to ensure high accuracy and efficiency, including oscillation angles and displacements of 0.1 to 25 micrometers, and using cutting tools like single crystal diamond.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If pins are used to manufacture mold for small segment corner cubes, then manufacturing precision can be maintained, but the number of pins increases dramatically and machining costs increase
Solution Approach 1:
The invention divides the mold manufacturing process into two distinct stages: roughing (removing most material) and finishing (achieving final precision). This segmentation allows each stage to use optimized tools - ball end mills for roughing and precision pins for finishing - thereby maintaining precision while dramatically improving efficiency for small segment corner cubes
Solution Approach 2:
The roughing process performs preliminary material removal using ball end mills before the finishing process. This preliminary action removes the bulk of material that would otherwise require numerous precision pins, reducing the total number of pins needed and thereby lowering costs while maintaining final precision
2Productivity
If ball end mill is used for milling mold, then manufacturing efficiency is improved, but the radius of curvature of corners cannot be made smaller than the minimum radius of curvature of the ball end mill
Solution Approach 1:
The manufacturing process is segmented into roughing with ball end mills (for efficiency) and finishing with precision pins (for corner accuracy). This allows the use of ball end mills for bulk material removal while precision pins create the sharp corners with radii smaller than the ball end mill's minimum radius
Solution Approach 2:
Different tooling is applied to different regions of the mold: ball end mills are used for general surface machining where efficiency is paramount, while precision pins are used specifically for corner regions where sharp radii are critical for optical performance
3Volume of moving object
If segment size is reduced to downsize corner cube, then application performance is improved, but the number of pins required increases in direct ratio to the inverse of the square of segment size
Solution Approach 1:
The roughing process performs preliminary material removal using ball end mills before the finishing process. This preliminary action removes the bulk of material that would otherwise require numerous precision pins, reducing the total number of pins needed and thereby lowering costs while maintaining final precision
Solution Approach 2:
The invention changes the machining parameters by introducing a two-stage process with different depth of cut values: roughing uses larger depth of cut (5-50 μm) for efficiency, while finishing uses smaller depth of cut (0.1-5 μm) for precision. This parameter optimization reduces the number of pins required for small segment corner cubes
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 allows for the production of molds with reduced random height changes and improved accuracy, enabling the manufacturing of retroreflective elements with precise dimensions and optical performance.
Implementation Method 1
a blade portion having two cutting edges, an angle formed by the two cutting edges being substantially identical with an interior angle of the polygonal face at the vertex
Implementation Method 2
the movement of the blade portion is a combination of a motion towards the vertex and an oscillation that causes at least one of a displacement in the direction of the motion and a displacement in the direction perpendicular to the direction of the motion
Data Source
AI summary
A method for manufacturing a mold for a retroreflective element, the mold having plural polygonal faces having a common vertex, the method including the steps of: roughing of a polygonal face in which cutting is carried out such that a predetermined cutting amount in a finishing process is left with respect to a desired shape; and finishing of the polygonal face in which a blade portion is made to move relatively towards the vertex while an angle of relief of the blade portion is kept within 1 degree so as to carry out cutting of the predetermined cutting amount, wherein a depth of cut for each one-time cutting operation is 2 micrometers or smaller, and the movement of the blade portion is a combination of a motion towards the vertex and an oscillation.