Rotary Cutting Insert Geometry to Prevent Workpiece Warpage

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Solution Overview

Problem

Rotary cutting of plate-shaped workpieces, such as aircraft wing surface members, often results in warpage due to uneven residual stress distribution, requiring time-consuming corrective measures.

Innovation Solution

A cutting insert and rotary cutting tool with a negative rake surface and positive flank surface design that applies compressive residual stress during cutting, preventing warpage by pressing the workpiece between the cutting insert and the machine tool base.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional rotary cutting is performed on plate-shaped workpieces, then cutting operation can be completed, but warpage occurs due to uneven residual stress distribution

Engineering Contradiction:

Improveflatness of workpieceVSAvoidwarpage

Core Design Contradiction:

Manufacturing precisionVSObject-generated harmful factors

Solution Approach 1:

The patent changes the geometric parameters of the cutting insert surfaces. The rake surface is configured with a negative inclination angle relative to the cutting edge, while the flank surface has a positive inclination angle. This parameter change modifies the stress distribution during cutting, applying compressive residual stress to the workpiece which counteracts the uneven tensile residual stress that causes warpage, thereby improving flatness without requiring additional corrective measures.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent applies different surface inclination characteristics to different parts of the cutting insert. The rake surface and flank surface have opposite inclination directions, creating localized stress application zones. This local quality differentiation allows the cutting insert to apply compressive stress specifically to the cut surface and surrounding areas, directly addressing the warpage problem at its source rather than treating the entire workpiece uniformly.

Inventive Principle:

Principle #3Local quality

2Manufacturing precision

If time-consuming corrective measures are applied to fix warpage, then manufacturing precision can be improved, but productivity decreases

Engineering Contradiction:

Improveflatness of workpieceVSAvoidmanufacturing cycle time

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The patent implements preliminary action by configuring the cutting insert with specific rake and flank surface inclinations before the cutting operation begins. This pre-configured geometry ensures that compressive residual stress is applied during the cutting process itself, preventing warpage from occurring in the first place. As a result, no post-cutting corrective measures are needed, and productivity is maintained while achieving high manufacturing precision.

Inventive Principle:

Principle #10Preliminary action

3Strength

If positive rake angle and positive flank angle are used, then cutting edge strength is improved, but compressive residual stress cannot be applied to prevent warpage

Engineering Contradiction:

Improvecutting edge strengthVSAvoidflatness of workpiece

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

The patent inverts the conventional approach by using a negative inclination angle for the rake surface instead of a positive angle. This inversion allows the cutting insert to apply compressive residual stress to the workpiece during cutting, which prevents warpage. The flank surface maintains a positive inclination to preserve cutting edge strength, so the inversion is selectively applied only where needed to achieve the stress control function.

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS11786981B2Cutting insert, cutting edge-replaceable rotary cutting tool and rotary cutting method

Publication Date: 2023.10.17 SUBARU CORP

AI summary

A cutting insert has a plate shape centered on an insert center axis. The cutting insert includes a front surface and a back surface facing an insert axial direction, an outer peripheral surface facing outward in an insert radial direction, and a cutting edge at an intersecting ridge line between the front surface and the outer peripheral surface. The back surface has a flat shape perpendicular to the insert center axis. The outer peripheral surface includes a flank surface coupled. The flank surface is inclined inward in the insert radial direction as extending in the insert axial direction from the front surface side to the back surface side. The front surface includes a rake surface. The rake surface is inclined from a back surface side to a front surface side in the insert axial direction as extending inward in the insert radial direction from the cutting edge.