A comparative study of the cutting forces in high speed machining of Ti–6Al–4V and Inconel 718 with a

round cutting edge tool.

Andrew Orme5 October 2009

N. Fang, Q. Wua

Purpose• Ti-6Al-4V• Inconel 718• Same set-up• Measure cutting forces

Importance• Tool wear• Machined surface integrity (aerospace)• Tool life• Economics

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Relation to course• Normal, Thrust, Cutting Force• Equations

Fc = Fs cos ( - )/[b a cos ( + - )] f b a

Ft = Fs sin ( - )/[b a cos ( + - )]f b a

Design• Good comparison

• Minimize variation • High Strength to weight ratio• Low thermal conductivity• Heat •Chip formation• Cutting Forces• Cutting Power• Cutting Energy• Material Removal Rate• Tool geometry

Design of Experiment•Small feed rates 0.075, 0.09, 0.105, 0.12mm/r • Work material (tube) Ti–6Al–4V and Inconel 718• Tube outer diameter 50mm• Tube wall thickness 1.4mm for Ti–6Al–4V

1. 2mm for Inconel 718• Tool insert TPG 432 (Kennametal Inc.)• Tool material Cemented carbide (KC 8050) with TiC/TiN/TiCN coating• Tool working rake angle 5◦• Tool edge radius 0.06mm (.002in)• Cutting speed 58, 87, 116, 144, 174m/min

.05*π=.157m

174m/min * 1rev/.157m

=

1107rpm.

Equipment• CNC Turning Lathe• Finish Machining• Five Cutting Speeds• Four feed rates• No cutting fluid or coolant• Tool radius measured after each cycle• Kistler Dynamometer• Kistler Amplifier• Data Acquisition System(Labview)• 20 Cutting Tests for each material• Most tests repeated 3 times

Design

Tables(a)Ti(b)Incone

l

Tables(a)Ti(b) Inconel

Force Ratio• Determines direction of resultant force

Empirical Regression•Cutting Force

Fc_Ti64=103.52Vc−0.155f0.784w

Fc_In718=103.81Vc−0.153f0.894w

• Thrust ForceFt_Ti64=103.02Vc

−0.257f0.127w

Ft_In718=103.41Vc−0.216f0.495w

• Resultant ForceRTi64=103.44Vc

−0.202f0.483w

RIn718=103.80Vc−0.175f0.746w

•Force RatioFc_Ti64/Ft_Ti64=100.508Vc

0.101f0.657

Fc_In718/Ft_In718=100.394Vc0.0635f0.400

Conclusions1. Increased cutting speed means lower cutting forces

but higher force ratio.2. Increased feed rate means increased cutting forces

and increased force ratio.3. Cutting force and thrust are higher for Inconel than

for Titanium.4. As feed rate changes, thrust force varies more in

Inconel than Titanium.

Industrial Use• Jet Engines• Aerospace• High strength to low weight ratio • High Speed Machining?

Develop new tools• Equations can be used to estimate cutting forces.