End-Milled Non-Orthogonal Cube Corner Arrays for Small-Scale Optics

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Solution Overview

Problem

Existing methods for manufacturing cube corner elements, such as pin bundling and direct machining, face limitations in producing small elements and offer reduced design flexibility, while lamina-based techniques restrict microstructured element arrangements.

Innovation Solution

An end milling technique is developed to create cube corner elements with dihedral angles deviating from orthogonality by small but significant amounts, allowing for diverse geometries and increased design flexibility, including arrays with varied cube corner elements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If pin bundling techniques are used to manufacture cube corner elements, then a wide variety of cube corner geometries can be produced, but the technique becomes impractical for making small cube corner elements (cube height less than about 1 millimeter)

Engineering Contradiction:

Improvevariety of cube corner geometriesVSAvoidsmall cube corner element size

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The master mold is segmented into multiple laminae (thin sheets), each containing a portion of the cube corner elements. This allows the mold to be manufactured with high precision using direct machining techniques while maintaining the ability to produce various cube corner geometries. The laminae are then assembled to form the complete mold structure.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention transitions from working with three-dimensional pins to working with two-dimensional laminae. By machining cube corner elements directly into flat sheets, the technique enables precise manufacturing of small elements while simplifying the overall manufacturing process and allowing for easier assembly and replication.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Manufacturing precision

If direct machining techniques are used to manufacture master molds, then very small cube corner elements can be accurately machined, but design flexibility is reduced due to reliance on grooves of constant depth

Engineering Contradiction:

Improvesmall cube corner element accuracyVSAvoiddesign flexibility of cube corner geometries

Core Design Contradiction:

Manufacturing precisionVSAdaptability or versatility

Solution Approach 1:

By dividing the master mold into multiple laminae, the invention enables the use of direct machining techniques to achieve high precision while overcoming the limitation of constant depth grooves. Each lamina can be independently machined with varying depths and geometries, allowing for diverse cube corner designs while maintaining manufacturing precision.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention changes the depth parameter of the machined grooves by using multiple laminae with different thicknesses and machining depths. This allows cube corner elements with varying geometries and optical characteristics to be produced, thereby increasing design flexibility while maintaining the precision benefits of direct machining.

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If lamina-based techniques are used to manufacture master molds, then labor intensity is reduced compared to pin bundling, but design flexibility is reduced due to linear or stacked arrangement of laminae

Engineering Contradiction:

Improvelabor intensityVSAvoidmicrostructured element arrangement flexibility

Core Design Contradiction:

Ease of manufactureVSAdaptability or versatility

Solution Approach 1:

The lamina-based technique is enhanced to serve multiple functions: it maintains the low labor intensity advantage while also enabling diverse microstructured element arrangements. By allowing laminae to be arranged in various configurations (not just linear or stacked) and by enabling different cube corner geometries on each lamina, the system achieves both ease of manufacture and design flexibility.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 technique enables the production of cube corner elements with enhanced light return patterns and design flexibility, suitable for various applications, including retroreflective materials, without compromising their retroreflective functionality.

Implementation Method 1

cutting the substrate with a rotating end mill to form a recess in the substrate

Methodology Applied

Scientific EffectMechanical cutting: Abrasion

Implementation Method 2

causing the rotating end mill to move along a cutting path relative to the substrate, the cutting path including a path portion that is inclined relative to the reference plane

Methodology Applied

Scientific EffectMaterial removal through rotation: Abrasion

Data Source

PatentUS11253933B2Non-orthogonal cube corner elements and arrays thereof made by end milling

Publication Date: 2022.02.22 3M INNOVATIVE PROPERTIES CO

AI summary

A new technique for making cube corner elements that involves end milling is used in the fabrication of cube corner elements having non-orthogonal dihedral angles and dihedral angle errors, and arrays of such cube corner elements. A given optical face of a cube corner element may be a compound face with two constituent faces. In some cases, the constituent faces may be parallel and coplanar such that a given dihedral angle error pertains to the entire optical face, while in other cases, the two constituent faces may not be parallel, and may be associated with different dihedral angle errors.