Undergraduate Research ExperienceDeformation Machining

Dylan SylvesterDr. Bethany Woody

Dr. Scott Smith

What is deformation machining?

Single Point Incremental Forming

No expensive tooling Simple 3-axis Machine

Simple 3-axis Machine

Sheet metal is ‘pushed’ to shape

Sheet metal is ‘pushed’ to shape

Thin Structure Machining

Monolithic PiecesMonolithic Pieces Reduced Assembly costReduced Assembly cost

Deformation Machining Advantages

Create geometries otherwise impossibleCreate geometries otherwise impossible

Extra material in the radius = added weight

Potential for weight and cost reductionPotential for weight and cost reduction

Eliminate the need for expensive 5 axis machinesEliminate the need for expensive 5 axis machines

Deformation Machining Advantages

Create geometries otherwise impossibleCreate geometries otherwise impossible

Potential for weight and cost reductionPotential for weight and cost reduction

Eliminate the need for expensive 5 axis machinesEliminate the need for expensive 5 axis machines

Deformation Modes

Bending•Walls•Forces are perpendicular to forming axis

Bending•Walls•Forces are perpendicular to forming axis

Stretching•Floors•Forces are parallel to forming axis

Stretching•Floors•Forces are parallel to forming axis

Deformation Modes

Process Requirements

Previous Research

Process Parameters

Grain directionGrain direction

Tool path•Depth of Cut•Step Size•Arc vs. no arc

Tool path•Depth of Cut•Step Size•Arc vs. no arc

Forming Speed•Linear feed rate•Spindle speed

Forming Speed•Linear feed rate•Spindle speed

Surface Finish, Final Geometry, and Cracking

Surface Finish, Final Geometry, and Cracking

Tool Path : Wall Forming

Tool Path : Floor Forming

Current Research

Changing parameters and their effects•Forming Speed•Spindle Speed•Tool Path

Changing parameters and their effects•Forming Speed•Spindle Speed•Tool Path

SEM Analysis of CrackingSEM Analysis of Cracking

Forming forces•Effects of forming direction•Effects of wall thickness

Forming forces•Effects of forming direction•Effects of wall thickness

Alternate Materials•Copper•Stainless Steel

Alternate Materials•Copper•Stainless Steel

Forming Speed and Spindle Speed

1. Use similar walls, tool path, and grain direction2. Change only linear feed rate3. Measure spring back – when metal returns to its original

shape after undergoing stretching

Part Number

Wall Number Material Bending

Axis

Wall Thickness

(in)

Wall Height

(in)

Wall Length

(in)

Feedrate (ipm)

Max Horiz Step Size

(in)

Tool Size Diam. (in)

Desired Angle

Bending Angle

achieved Angle

Spring back

Percent

Percent off

Desired

Visible Cracks

Mastercam File Name

Spindle Speed (rpm)

Lube

W5 A AL7050-T7451 ST 0.04 0.85 1.5 30 0.04 0.5 - 45 43.561 3.20% - N W5 0 Lithium

W5 B AL7050-T7451 ST 0.04 0.85 1.5 40 0.04 0.5 - 45 44.447 1.23% - N W5 0 Lithium

W5 C AL7050-T7451 ST 0.04 0.85 1.5 50 0.04 0.5 - 45 42.959 4.54% - N W5 0 Lithium

W5 D AL7050-T7451 ST 0.04 0.85 1.5 60 0.04 0.5 - 45 44.192 1.80% - N W5 0 Lithium

W5 E AL7050-T7451 ST 0.04 0.85 1.5 70 0.04 0.5 - 45 43.846 2.56% - N W5 0 Lithium

W5 F AL7050-T7451 ST 0.04 0.85 1.5 80 0.04 0.5 - 45 44.169 1.85% - N W5 0 Lithium

W7 A AL7050-T7451 ST 0.04 0.85 1.5 30 0.04 0.5 - 35 32.532 7.05% - N W7 0 Lithium

W7 B AL7050-T7451 ST 0.04 0.85 1.5 40 0.04 0.5 - 35 33.354 4.70% - N W7 0 Lithium

W7 C AL7050-T7451 ST 0.04 0.85 1.5 50 0.04 0.5 - 35 33.099 5.43% - N W7 0 Lithium

W7 D AL7050-T7451 ST 0.04 0.85 1.5 60 0.04 0.5 - 35 33.095 5.44% - N W7 0 Lithium

W7 E AL7050-T7451 ST 0.04 0.85 1.5 70 0.04 0.5 - 35 33.624 3.93% - N W7 0 Lithium

W7 F AL7050-T7451 ST 0.04 0.85 1.5 80 0.04 0.5 - 35 33.747 3.58% - N W7 0 Lithium

Forming Speed and Spindle Speed

•Forming Speed only effects small angles•In ST and LT directions, no cracking was visible on the surface•Minimal increase in forming forces compared to slow form rates

•Forming Speed only effects small angles•In ST and LT directions, no cracking was visible on the surface•Minimal increase in forming forces compared to slow form rates

Forming Speed and Spindle Speed

•Cause spindle to rotate based on linear travel direction•RPM depends on linear feed rate and radius of tool

•Cause spindle to rotate based on linear travel direction•RPM depends on linear feed rate and radius of tool

•Contact point changes over time•Constantly changing spindle speed•Smudged or scaly appearance

•Contact point changes over time•Constantly changing spindle speed•Smudged or scaly appearance

Forming Forces

Using dynamometer (left) forces were measured while forming

•Calibration using known weights and measuring the output along with impact hammer•Pieces securely attached to dynamometer•LT, ST, and longitudinal directions measured for .04” thick walls in aluminum

Using dynamometer (left) forces were measured while forming

•Calibration using known weights and measuring the output along with impact hammer•Pieces securely attached to dynamometer•LT, ST, and longitudinal directions measured for .04” thick walls in aluminum

YX

Z

Forming Forces – Long Transverse

•Largest force in Y direction – about 400 N•Cracking around 175 seconds – dramatic loss in force•Changing X direction caused alternating positive and negative force

•Largest force in Y direction – about 400 N•Cracking around 175 seconds – dramatic loss in force•Changing X direction caused alternating positive and negative force

Forming Forces – Short Transverse

•Largest force in Y direction – about 380 N•High Z forces near end of form•Changing X direction caused alternating positive and negative force

•Largest force in Y direction – about 380 N•High Z forces near end of form•Changing X direction caused alternating positive and negative force

Forming Forces - Longitudinal

•Largest force in Y direction – about 380 N•Cracked halfway during form•Largest force in Y direction – about 380 N•Cracked halfway during form

•.02” Thick Wall•LT Forming direction•A few visible surface defects, however no noticeable cracks

•.02” Thick Wall•LT Forming direction•A few visible surface defects, however no noticeable cracks

SEM Analysis

•Many smalls cracks aren’t visible without magnification•A relatively large crack is often surrounded by many smaller cracks•Many small voids created along bend path

•Many smalls cracks aren’t visible without magnification•A relatively large crack is often surrounded by many smaller cracks•Many small voids created along bend path

SEM Analysis

Alternate Materials

CopperCopper

•Same tool path as aluminum yields visibly curved wall•Spring back results differ from aluminum

•Same tool path as aluminum yields visibly curved wall•Spring back results differ from aluminum

Part Number

Wall Number Material Bending

Axis

Wall Thickness

(in)

Wall Height

(in)

Wall Length

(in)

Feedrate (ipm)

Max Horiz

Step Size (in)

Tool Size Diam.

(in)

Desired Angle

Bending Angle

achieved Angle

Spring back

Percent

Percent off

Desired

Visible Cracks

Mastercam File Name

Spindle Speed (rpm)

Lube

W11 A Copper - 0.04 0.85 1.5 10 0.04 0.5 - 20 19.92 0.40% - N Copper Wall 0 LithiumW11 B Copper - 0.04 0.85 1.5 10 0.04 0.5 - 25 24.538 1.85% - N Copper Wall 0 LithiumW11 C Copper - 0.04 0.85 1.5 10 0.04 0.5 - 30 29.527 1.58% - N Copper Wall 0 LithiumW11 D Copper - 0.04 0.85 1.5 10 0.04 0.5 - 35 34.7 0.86% - N Copper Wall 0 LithiumW11 E Copper - 0.04 0.85 1.5 10 0.04 0.5 - 40 39.513 1.22% - N Copper Wall 0 LithiumW11 F Copper - 0.04 0.85 1.5 10 0.04 0.5 - 45 44.617 0.85% - N Copper Wall 0 Lithium

Alternate Materials

Stainless Steel

Stainless Steel

•Same tool path as aluminum yields visibly curved wall•Higher feed rate has little effect on spring back

•Same tool path as aluminum yields visibly curved wall•Higher feed rate has little effect on spring back

Ongoing Research

•Residual stress measurements at NIST and correlation with cracking•Further analysis of forming parameter in regards to cracking•Refinement of tool path to create straight walls regardless of material•Continue alternate material testing along including complex shapes•Further SEM and stereo microscope analysis

•Residual stress measurements at NIST and correlation with cracking•Further analysis of forming parameter in regards to cracking•Refinement of tool path to create straight walls regardless of material•Continue alternate material testing along including complex shapes•Further SEM and stereo microscope analysis