Simulation and Evaluation of Different Process Strategies in a 5-Axis Re-contouring Process Machining Innovations Conference Berend Denkena, Volker Böß, Dennis Nespor, Felix Rust Garbsen, November 18 th, 2015

Dipl.-Ing. Felix Rust | Machining Innovations Conference 2015 | November 18 th | © IFW 2015 Page 2 Outline 1.Motivation 2.Analogue Workpiece and Simulation Model 3.Evaluation of Process Strategies 4.Conclusion and Outlook

Dipl.-Ing. Felix Rust | Machining Innovations Conference 2015 | November 18 th | © IFW 2015 Page 3 a) Foreign Object Damage (FOD) b) FOD and Erosion Causes for Turbine Component Damage Microstructural ChangesOxidationCracksAbrasionBreakagesDeformation

Dipl.-Ing. Felix Rust | Machining Innovations Conference 2015 | November 18 th | © IFW 2015 Page 4 Repair Cases in Regeneration of Engine Blades Post- treatment Re- contouring Material Deposit Pre- treatment Tip-repair Material cladding with laser welding technique – low heat input into material Patch-repair Patch joint through plasma arc welding without additive Crack-repair through brazing or welding depending on crack size

Dipl.-Ing. Felix Rust | Machining Innovations Conference 2015 | November 18 th | © IFW 2015 Page 5 Challenges in Re-contouring of Engine Blades Post- treatment Re- contouring Material Deposit Pre- treatment Process Design Shape of excess material Varying material properties Machine Properties Individually formed surface Individual blade roots Machining Workpiece and tool vibrations Varying tool engagement Induced residual stresses Final surface topography

Dipl.-Ing. Felix Rust | Machining Innovations Conference 2015 | November 18 th | © IFW 2015 Page 6 Outline 1.Motivation 2.Analogue Workpiece and Simulation Model 3.Evaluation of Process Strategies 4.Conclusion and Outlook

Dipl.-Ing. Felix Rust | Machining Innovations Conference 2015 | November 18 th | © IFW 2015 Page 7 Design of the Analogue Workpiece Requirements -Simulation of a complex weld shape -Minimization of workpiece deflection and vibration by using increased blade thickness -Milled from a single blank -Re-contouring in same clamping position Tip-repair Patch-repair 5 mm 36 mm 31 mm 13 mm

Dipl.-Ing. Felix Rust | Machining Innovations Conference 2015 | November 18 th | © IFW 2015 Page 8 Verification of the Dexelgrid Resolution Multi-Dexelgrid (resolution 256) Z-Direction X-Direction Y-Direction ms mm² Res. 512 Res. 256 Res. 128 Process Time t Cross Section A z x y Z-Dexelgrid (resolution 256) Res. 512 Res. 256 Res. 128 z x y ms mm² Process Time t Cross Section A The complex weld shape needs a resolution of 512 at least for good results

Dipl.-Ing. Felix Rust | Machining Innovations Conference 2015 | November 18 th | © IFW 2015 Page 9 Verification of the Angle Step Resolution Angle Step φ = 4° Angle Step φ = 2° Angle Step φ = 0.5° mm Feed Direction Step Over Direction mm 0 3 µm Inaccuracies in Surface Topography -Surface topography shows inaccuracies for large angle steps -A correct kinematic topography is attained by a reduction of the angle step -Angle step of 0.5 °is best compromise between accuracy and computation time Height

Dipl.-Ing. Felix Rust | Machining Innovations Conference 2015 | November 18 th | © IFW 2015 Page 10 Outline 1.Motivation 2.Analogue Workpiece and Simulation Model 3.Evaluation of Process Strategies 4.Conclusion and Outlook

Dipl.-Ing. Felix Rust | Machining Innovations Conference 2015 | November 18 th | © IFW 2015 Page 11 Approach for Prediction of Surface Integrity ExperimentsSimulation Forces Topography Residual stress measurement x-ray diffractometry Topography measurement whitelight confocal microscope Hybrid Model Residual Stresses Prediction Material Coefficient Ploughing Forces A Sp -Process force model validated in another work -Topography is determined through the dexelgrid -The ploughing forces refer to the surface generating forces Non-Surface Generating Surface Generating

Dipl.-Ing. Felix Rust | Machining Innovations Conference 2015 | November 18 th | © IFW 2015 Page 12 Strategy 1 Strategy 2 Strategy 3 Tool-path (schematically) Analog weld Nominal tip contour Ball end mill without roughing Finishing with ball end mill Roughing with end Mill Discretized depth of cut Re-contouring Strategies Feed speed

Dipl.-Ing. Felix Rust | Machining Innovations Conference 2015 | November 18 th | © IFW 2015 Page 13 Simulation of Process Forces Cutting Speedvcvc = 120 m/minDepth of Cutapap = var. Feed per Toothfzfz = 0.2 mmStep Overbrbr = 0.3 mm Lead Angle λ = var.Tilt Angle τ = var. Process Parameters 0 N 200 Process Forces F i N N s Process Time t Strategy 1 Strategy 2 Strategy 3 Passive force F p Feed force F f Feed normal force F fN

Dipl.-Ing. Felix Rust | Machining Innovations Conference 2015 | November 18 th | © IFW 2015 Page 14 Surface Integrity: Topography mm 2.5 Step Over Direction mm Feed Direction mm mm 0 20 µm Height Strategy 1 (Roughing) Strategy 3 (Roughing/Finishing) Kinematic Topography (Simulation) Cutting Speedvcvc = 120 m/minDepth of Cutapap = var. Feed per Toothfzfz = 0.2 mmStep Overbrbr = 0.3 mm Lead Angle λ = 30 °Tilt Angle τ = 0 ° Process Parameters Measured deflectionSimulated deflection Strategy 1250 µm222 µm Strategy 330 µm24 µm Transition Measured Topographie

Dipl.-Ing. Felix Rust | Machining Innovations Conference 2015 | November 18 th | © IFW 2015 Page 15 Surface Integrity: Residual Stresses Measurement directions Confidence interval of measurements ( ξ = 90 %) Step Over Direction σ MPa Strategy 1 (r β = 5 µm) Strategy 2 (r β = 5 µm) Strategy 3 (r β = 30 µm) σ 0° σ 90° σ 0° σ 90° σ 0° σ 90° S1S1 S2S2 S1S1 S2S2 S1S1 S2S2 Parameter S/K MPa mm³ Cutting Speedvcvc = 120 m/minDepth of Cutapap = var. Feed per Toothfzfz = 0.2 mmStep Overbrbr = 0.3 mm Lead Angle λ = 30 °Tilt Angle τ = 0 ° Process Parameters Simulations

Dipl.-Ing. Felix Rust | Machining Innovations Conference 2015 | November 18 th | © IFW 2015 Page 16 Outline 1.Motivation 2.Analogue Workpiece and Simulation Model 3.Evaluation of Process Strategies 4.Conclusion and Outlook

Dipl.-Ing. Felix Rust | Machining Innovations Conference 2015 | November 18 th | © IFW 2015 Page 17 Conclusion  Simulation is applicable to predict surface integrity regarding surface topography and residual stresses  Strategy 1 shows highest tool deflection, to be seen in final topography  Strategy 2 and 3 lead to homogeneous removal rate – less force amplitude and less variation  Strategy 3 is recommended for industrial application due to sufficient workpiece quality and only slight increase in process time

Dipl.-Ing. Felix Rust | Machining Innovations Conference 2015 | November 18 th | © IFW 2015 Page 18 Outlook  Workpiece and tool vibration has influence on exp. results and need to be considered in future work  Computation time is still very long for a whole re-contouring process and has to be reduced  Therefore a method for selective simulation and analysis of the process is needed for a practical approach  For further processing of simulation results a link between tool path planning and the NC-simulation is needed

Dipl.-Ing. Felix Rust | Machining Innovations Conference 2015 | November 18 th | © IFW 2015 Page 19 Thank you for your Attention!