PCD End Milling of Brittle Materials Below the Ductile-Brittle Threshold

Solution Overview

Problem

Milling brittle materials like glass and sapphire with existing diamond electroplated tools often results in subsurface damage and limited tool life, leading to increased production costs and risk of cracking in mobile phone handset shells.

Innovation Solution

A method using an end milling tool with a superhard material tool head, such as polycrystalline diamond (PCD), where the Undeformed Chip Thickness is controlled to be below the Ductile-Brittle Transition Undeformed Chip Thickness of the material, minimizing subsurface damage and extending tool life by optimizing the tool design and milling parameters.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If diamond electroplated tools are used to mill brittle materials, then cutting capability is improved, but subsurface damage increases and tool life decreases

Engineering Contradiction:

Improvecutting capabilityVSAvoidsubsurface damage

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent changes the fundamental material parameter from electroplated diamond to sintered polycrystalline diamond (PCD), which fundamentally alters the tool's mechanical properties. PCD provides superior toughness and resistance to subsurface damage while maintaining high cutting capability, directly resolving the contradiction between productivity and reliability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses composite material structure where diamond particles are sintered together to form PCD tool heads. This composite structure combines the hardness of diamond with the toughness of the sintered matrix, enabling both high cutting capability and resistance to subsurface damage and tool chipping

Inventive Principle:

Principle #40Composite materials

2Productivity

If diamond electroplated tools are used to mill brittle materials, then cutting capability is improved, but tool life decreases

Engineering Contradiction:

Improvecutting capabilityVSAvoidtool life

Core Design Contradiction:

ProductivityVSDuration of action of moving object

Solution Approach 1:

The patent changes the fundamental material parameter from electroplated diamond to sintered polycrystalline diamond (PCD), which fundamentally alters the tool's mechanical properties. PCD provides superior toughness and resistance to subsurface damage while maintaining high cutting capability, directly resolving the contradiction between productivity and reliability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses composite material structure where diamond particles are sintered together to form PCD tool heads. This composite structure combines the hardness of diamond with the toughness of the sintered matrix, enabling both high cutting capability and resistance to subsurface damage and tool chipping

Inventive Principle:

Principle #40Composite materials

3Speed

If conventional milling parameters are used on brittle materials, then machining speed is maintained, but subsurface damage increases

Engineering Contradiction:

Improvemachining speedVSAvoidsubsurface damage

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The patent identifies and controls the undeformed chip thickness parameter to remain below the ductile-brittle transition threshold. This parameter control enables conventional machining speeds to be maintained while the material removes in a ductile manner, preventing subsurface damage

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent establishes preliminary control measures by setting the undeformed chip thickness below the ductile-brittle transition value before machining begins. This pre-established parameter control ensures that the material is always removed in a ductile manner, preventing subsurface damage from occurring in the first place

Inventive Principle:

Principle #10Preliminary action

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 reduces subsurface damage and extends tool life, enabling efficient machining of brittle materials while avoiding the limitations of diamond electroplated tools, such as premature wear and environmental impact.

Implementation Method 1

Milling is a cutting process whereby a tool with multiple cutting surfaces is rotated to remove material from the surface of a work piece

Methodology Applied

Scientific EffectAbrasion: Abrasion

Implementation Method 2

By controlling the undeformed chip thickness to be below the DBT value, the material is removed in a ductile manner, preventing subsurface damage

Methodology Applied

Scientific EffectDuctile mode deformation: Deformation

Data Source

PatentUS20250100185A1Method of milling brittle materials using a polycrystalline diamond end milling tool

Publication Date: 2025.03.27 ELEMENT SIX (UK) LTD

AI summary

Herein is provided a method of milling a brittle workpiece (46) using a milling tool (10), •—the workpiece (46) comprising a material, the material having a Ductile-Brittle Transition Undeformed Chip Thickness, DBhrn, •—the milling tool (10) comprising a tool shank (12) having an axis of rotation (14), and further comprising a tool head (16) comprising superhard material at one end thereof, the tool head (16) having a diameter (42), and •—operating the milling tool (10) such that an Undeformed Chip Thickness, hm, of the workpiece (46) is less than said Ductile-Brittle Transition Undeformed Chip Thickness, DBhm of the material.