improving performance in milling of titanium structures

October 4th, 2010

T.J. Long, Paul Prichard, Francois Gau, and

Tom Muller

Kennametal Technology Center

Latrobe, PA

Improving Performance in Milling

of Titanium Structures

© 2008 Kennametal Inc. l All rights reserved. l Proprietary and Confidential l 1

Agenda

• Customer Driven Productivity Improvement

• Challenges in machining Titanium

• Thermal Management

• Taking Costs Out


40

60

80

100

1960's 1970's 1980's 1990's 2000 2010

Aluminium Titanium

Drive to Reduce Ti

Machining Cost by 50%2X increase Ti in Airframe

$ p

er

IN3

Ma

ch

ine

d

• Double productivity

• Increase tool life

• Increase reliability

• Milling compatible

Customer

Requirements

Customer Driven Productivity Improvement

One large aerospace customer

points out that MRR for Aluminum

went down over the years. Not so

for Titanium.


Challenges in Machining Titanium

90% of work from metal

cutting is converted into

heat

X (mm)

Y(m

m)

4.8 4.9 5 5.1 5.2 5.3

1.8

2

Temperature (C)

1000

950

900

850

800

750

700

650

600

550

500

450

400

350

300

250

200

150

100

Third Wave AdvantEdgeThird Wave AdvantEdge• Good high temperature strength

increases the work needed to cut

Titanium.

• High work hardening and strain rate

sensitivity exacerbate thermal issues

in cutting Ti alloys.

• Titanium reacts with all materials at

high temperatures to chemically wear

tools.

• Poor thermal conductivity of Ti

causes heat to partition to the tool

instead of the chip.

Titanium Characteristics


Time (s)

Fo

rce

-X(N

),F

orc

e-Y

(N)

Te

mp

era

ture

(C)

0 0.001 0.002 0.0030

100

200

300

400

500

600

700

0

200

400

600

800

1000Force-X (N)

Force-Y (N)

Temperature (C)

Time (s)

Fo

rce

-X(N

),F

orc

e-Y

(N)

Te

mp

era

ture

(C)

0 0.0005 0.001 0.00150

200

400

600

800

1000

0

200

400

600

800

1000Force-X (N)

Force-Y (N)

Temperature (C)

50 m/min at 0.15 mm chip 100 m/min at 0.15 mm chip

Effect of Cutting Speed on Temperature

Increase Tool Temp +250oC

Current Ti cutting conditions Double Cutting Speed

FEM predicts a 250°C increase in cutting temperature to

double speed


Failure Mechanism Map

Safe Zone

Cutting Speed = Temperature

Ch

ip T

hic

kn

ess =

Str

ess

Chipping

Thermal

deformation

Crater Wear

Milling of TitaniumTurning of Steel

Safe Zone

Cutting Speed = Temperature

Ch

ip T

hic

kn

ess =

Str

ess

Edge

ChippingThermal

cracking

Rake Face

Chipping


Coolant Application Effects

• Thermal

– 90% of work converted to heat

– Low conductivity workpieces retain heat

– Coolant systems flush chip backside

• Lubrication

– Tool/chip friction generates heat

– Tool/chip friction increase shear stress

– Good lubrication reduces both

• Chip Evacuation

– External coolant pushes chip into cut

– Recutting chips accelerates failure

– Internal coolant assists evacuation

Lubricated frictionCoolant composition, delivery pressure, volume flow rate and

impingement location affects the metal cutting performance.

http://upload.wikimedia.org/wikipedia/commons/1/16/Makino-S33-MachiningCenter-example.jpg


0.00

0.50

1.00

1.50

2.00

2.50

Rela

tive T

oo

l L

ife

Std Coolant Beyond Blast

T124755 KSSM 45° Lead Angle

Beyond Blast vs. Standard Through Coolant

KSSM45 Milling Tool Development

KSSM45 Beyond BlastTM provided over 2 times better tool life than

standard through spindle coolant delivery.

Cutting Conditions

Workpiece: Ti6Al4v

Hardness: 42 – 46 HRC

Length of Pass: 254mm (10 in)

Cutting Fluid: Water based Synth.

Coolant Pressure: 300 psi.

Cutting Parameters

Cutting Speed: 58 m/min (187 SFM)

Chip load (fz): 0.25mm/tooth(0.010 ipt)

Axial Depth of Cut = 2 mm (0.08 inch)

Radial Depth of Cut = 81 mm (3.2 inch)

Baseline


0.00

0.50

1.00

1.50

2.00

2.50

3.00

Re

lati

ve

To

ol L

ife

Std Coolant

150 SFM

Beyond Blast

150 SFM

Std Coolant

187 SFM

Beyond Blast

187 SFM

T114526 & T117470 Daisy Round Inserts

Beyond Blast vs. Standard Through Spindle Coolant

Std Coolant

Beyond Blast

Daisy Milling Tool Development

DAISY Beyond BlastTM provided over 2.5 times better tool life than

standard through spindle coolant delivery @ 150 SFM.

Cutting Parameters

Cutting Speed: 46 m/min (150 SFM)

& 58 m/min (187 SFM)

Chip load (fz): 0.25mm/tooth(0.010 ipt)

Axial Depth of Cut = 3.8 mm (0.15 inch)

Radial Depth of Cut = 51 mm (2.0 inch)

Cutting Conditions

Workpiece: Ti6Al4v

Hardness: 42 – 46 HRC

Length of Pass: 254mm (10 in)

Cutting Fluid: Water based Synth.

Coolant Pressure: 1000 psi.

Baseline


Integrated Thermal Management

Coolant application has a large effect on tool performance


It’s Not Just About the Tools:

It Is About Partnerships, Digitization and Integration

Design Part

with CAD

Select

MachineSelect Tools

Write & Optimize

ProgramProduce Part Inspection

That Can be Optimized

A Complex Iterative Process

0 10 20 30 40 50 60 70 80 90 100

Optimized

Baseline

Forging/Casting Machine Tool Cutting Tools Machining Other

The Opportunity

http://images.google.com/imgres?imgurl=http://upload.wikimedia.org/wikipedia/commons/8/8c/Micrometer_(PSF).png&imgrefurl=http://commons.wikimedia.org/wiki/Image:Micrometer_(PSF).png&usg=__DLqHXp6sGtaEtwTRU6Y0NvDEgkI=&h=2200&w=2344&sz=438&hl=en&start=18&tbnid=6T1zv2BJ1l4tlM:&tbnh=141&tbnw=150&prev=/images%3Fq%3DMicrometer%26gbv%3D2%26hl%3Den%26sa%3DG

http://en.wikipedia.org/wiki/Image:Ugs-nx5-mold-tooling.jpg

http://en.wikipedia.org/wiki/Image:Ugs-nx5-mold-tooling.jpg


An Aerospace Example of Partnerships

Total Solution Set

Rough Milling

Finish Milling

Hole Making

Digitization and Integration of Best Practices


AttributeCurrent

ProcessNew Process

Batch Size 5 1

Number of Machines

& Spindles4 & 20 3 & 3

Maximum Production

Rate1 part per day 2.5 parts per day

Total Flow Time 15.5 days 2 days

Work in Process 100 parts 7 parts

Maintenance Specialized General

Return on Assets Low High

Safety / Ergonomics High Risks Low Risks

Floor Space / Machine

FootprintHigh Low

The Bottom Line: Productivity!


“Tunable” Boring Bar

Boeing 777 Landing Gear - 300M Steel

Overcoming Chatter

“Tunable” HARVI Cutters™

MH-53 Rotor - Ti 6Al4V

Wavy edge tools

Differential Pitch

Plunge Mills


Conclusion – Integrated Performance

• Machining of Ti alloys present many unique challenges due to the high strength, chemical reactivity and poor thermal conductivity.

• The optimum machining productivity combines metalcutting application knowledge, materials science expertise and advanced manufacturing technology.

• Thermal management has a large role in overall performance

Rela

tive T

ool Life I

mpro

vem

ent

Geo

me

try T

herm

al M

gm

t

Co

ati

ng

Inte

gra

ted

Perf

orm

an

ce

Su

bs

tra

te

Beyond Imagination!

improving performance in milling of titanium structures

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