The Evaluation of Cutting-Force Coefficients Using Surface Error Measurements Journal of Materials Processing Technology 196 (2008) 42-51 Mariana Dotcheva, Huw Millward, Alan Lewis Presenter: Andrew Gerla 07 October 2009 1

To provide a new approach for the determination of cutting forces. Purpose To provide a new approach for the determination of cutting forces. 2

References

Cutting Force Affects... Required machine power rating Tool wear Tolerances Surface finish Required lubrication and cooling Economy of prototyping and small batches 4

Old Methods Use mechanistic models with empirical coefficients Require expensive instrumentation to gather empirical data Require skilled technicians to record and process data Applicable only to the conditions under which test was performed Not easily implemented for prototyping or small batch work 5

The Proposed Method Cutting force is proportional to tool deflection Tool deflection is related to surface finish Empirical relationship may apply to operations with different cutting conditions Find equations like these: Tangential force KT(tc) = Ct1(tc)−kt1 Radial force KR(tc) = Ct2(tc)−kt2 6

Method

Method Discretize cutting tool by: Flute Angle of rotation Discs normal to axis of rotation

Analytical Models Cutting Forces: FX(θ(i, k, j)) = KT(EX1 + KREX2) FZ(θ(i, k, j)) = KT(EZ1 + KREZ2) FY(θ(i, k, j)) = KT(EY1 + KREY2)

Analytical Models Tool Deflection: δ(h) = δs + θs(h) + δt(h)

Experimental Procedure

Experimental Procedure Cutting Test Cut two strips with the same cutting conditions Vary axial depth by ∆a Calculate difference in surface finish Difference in surface finish mainly due to additional forces from elemental disc ∆a 12 different feed rates

Experimental Procedure Cutting Test End milling operation HSS 3-flute 16mm cutter Aluminum alloy 6082 Down-milling (climb-milling) Radial depth 3 mm, axial depths 8 and 9mm ∆a = 1mm

Experimental Procedure Data Acquisition CNC operated profilometer Maximum error 3.2% Straight measuring tool paths, 0.1mm increment

Analysis

Results MATLAB curve fit:

Conclusions Analytical model accurately predicts experimental data in similar cutting conditions Uncut chip thickness can be calculated Study needs more verification of accuracy for different cutting conditions Different materials require different coefficients