Vivekananda Kovvuri and Wayne Hung Texas A&M University Contact: hung@tamu.edu Present at 4 TH HTEC Texas Educators Machining Conference Grand Prairie, Texas March 29, 2014 HTEC Grand Prairie_27mar14.pptx
AGENDA 1) Introduction 2) Surface measurement Theory Comparison Profilometry Interferometry Scanning probe microscopy 3) Machined surface models 4) Summary 2
Surface finish: introduction www.nih.gov www.cssfirm.com 3
304 1A 400s 316L 1.25A 400s 316L as milled 316L 1.25A 400s 4
Maximum valley depth R v R v = min y i Maximum peak height R p R p = max y i Average roughness R a R a = 1 n y n i=1 i Root mean squared roughness R RMS or R q R rrr = 1 n (y n i=1 i) 2 Total roughness R t from the highest peak to the lowest valley points. It is also referred to as R tm or R max. R t = R p R v Average consecutive peak-valley roughness R z. This is the average of 5 largest consecutive peak-valley distances R z = 1 5 R 5 pp R vv i=1 Surface finish: Theory 5
Measurement: comparison Estimate surface finish by comparing with standards Inexpensive Portable Subjective Qualitative bbs.homeshopmachinist.net 6
Measurement: Profilometry www.worldoftest.com store.gaging.com Contact stylus with different head/force Inexpensive Portable Not accurate due to stylus size Scratch soft surface 7
Measurement: Interferometry www.activeopticalsystems.com http://en.wikipedia.org/wiki/interferometry 8
Measurement: Interferometry Non-contact Measure line and area surface finish Non-portable Expensive www.zygo.com 9
ECM+ ECP, sample A12 11
Measurement: Tunneling microscopy Tunneling current between 2 parts: I~e 2KK 13
Measurement: Atomic force microscopy store.nanoscience.com 14
Measurement: scanning probe microscopy STM/AFM imaging modes STM/AFM system 15
STM/AFM system education.mrsec.wisc.edu Tapping/scanning modes Atomic resolution Expensive Very slow Non-portable http://mcf.tamu.edu/instruments/new-afm 16
AFM
Machined surface measurement www.zygo.com 18
Ball-end milling: model R t = D D 2 f t 2 Effect of tool geometry and chip load D*Ra (µm.µm) 1.E+4 1.E+3 Theory Empirical R a = 0.2423 (f t) 2 D 1.E+2 1.E+1 1.E-2 1.E-1 1.E+0 1.E+1 1.E+2 1.E+3 Chip load (µm/tooth) R a = theoretical average surface finish (in, mm) R t = theoretical peak-valley surface finish (in, mm) f t = chip load (in/tooth, mm/tooth) 20
Flat-end milling: model Effect of tool geometry and chip load R t = f t ttt R a = 5 18 f tttt http://www.globalspec.com/reference/68253/203279/milling-cutters R a = theoretical average surface finish (in, mm) R t = theoretical peak-valley surface finish (in, mm) f t = chip load (in/tooth, mm/tooth) 21
2.2 Milling Al6061, Φ3.175mm, flat end, 2 flute, 30m/min and 60m/min, Dry cutting, Interferometry 2 1.8 Surface roughness, Ra, µm 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0 10 20 30 40 50 60 70 80 90 100 Chip load, µm/tooth R a = 5 18 * f t * tan α α = end cutting edge angle = 3.49 o high Low Average High Low Average Trend Linear (Trend)
Milling Al6061, Φ3.175mm, flat end, 2 flute, 30m/min, 60m/min, Dry cutting, Profilometry Surface Roughness, Ra, µm 2.2 2 1.8 1.6 1.4 1.2 1 0.8 0.6 0.4 0.2 0 10 20 30 40 50 60 70 80 90 100 Chip Load, µm/tooth High Low Average High Low Average Trend Linear (Trend) R a = 5 * 18 α f t = * end tan α cutting edge angle =3.49 o
Modelling issues Effect of workpiece material Built-up edge of ductile material Tearing of surface when machining ductile materials Cracks in surface when machining brittle materials Use correction factor to calculate theoretical surface finish 26
µecm: Electrode forming on CP Titanium Rolling fracture Rolling mark Embedded inclusion As received CP titanium sheet 27
µecm: Electrode forming on CP Titanium Ti Salt Fe Ti Br 10 khz, stainless steel electrode, NaNO 3 + KBr electrolyte, 3 mm gap, 168 ma/mm 2 current density, 62 µm/s feed. 28 Ti
µecm: Electrode forming on CP Titanium ECM of CP Ti ECM: Sample A2,50kHz,25-0V, 202mA,485 ma/mm 2, 200um, 90s, (50g KBr+15g NaNO 3 +500g H 2 O). 29
µecm: Electrode forming on CP Titanium Ti Ti ECM: Sample A11,100kHz,25-0V, 205mA,490 ma/mm 2,100um, 90s, (50g KBr+15g NaNO 3 +500g H 2 O). ECP: (60 g/l, 99%, AlCl 3 +280 g/l, 98+%, ZnCl 2 + 300 ml/l, C 3 H 8 O +700 ml/l, USP-200 proof, C 2 H 5 OH) at 25v DC, 10 mm gap,120 ma/cm 2, 35 C, 20 min, 1mg/cm 2 /min MRR. ECM+ECP of CP Ti 30
µecm: Electrode forming on CP Titanium ECM+ECP of CP Ti ECM: Sample A12,50kHz,25-0V, 211mA,504 ma/mm 2,50um, 90s, (50g KBr+15g NaNO 3 +500g H 2 O). ECP: (60 g/l, 99%, AlCl 3 +280 g/l, 98+%, ZnCl 2 + 300 ml/l, C 3 H 8 O +700 ml/l, USP-200 proof, C 2 H 5 OH) at 25v DC, 10 mm gap,120 ma/cm 2, 35 C, 20 min, 1mg/cm 2 /min MRR. 31
µecm: Polishing of CP Titanium Polishing of as-received CP Ti ECP: (60 g/l, 99%, AlCl 3 +280 g/l, 98+%, ZnCl 2 + 300 ml/l, C 3 H 8 O +700 ml/l, USP-200 proof, C 2 H 5 OH) at 25v DC, 10 mm gap,120 ma/cm 2, 35 C, 20 min, 1mg/cm 2 /min MRR. 32
µecm: CP Titanium After µecm, Area RMS=340 nm After µecm+ecp Area RMS=42 nm ECM: Sample A12,50kHz,25-0V, 211mA,504 ma/mm 2,50um, 90s, (50g KBr+15g NaNO 3 +500g H 2 O). ECP: (60 g/l, 99%, AlCl 3 +280 g/l, 98+%, ZnCl 2 + 300 ml/l, C 3 H 8 O +700 ml/l, USP-200 proof, C 2 H 5 OH) at 25v DC, 10 mm gap,120 ma/cm 2, 35 C, 20 min, 1mg/cm 2 /min MRR. 33
µecm+ecp: CP Titanium After µecm, Area RMS= 340 nm After µecm+ecp Area RMS= 42 nm ECM: Sample A12,50kHz,25-0V, 211mA,504 ma/mm 2,50um, 90s, (50g KBr+15g NaNO 3 +500g H 2 O). ECP: (60 g/l, 99%, AlCl 3 +280 g/l, 98+%, ZnCl 2 + 300 ml/l, C 3 H 8 O +700 ml/l, USP-200 proof, C 2 H 5 OH) at 25v DC, 10 mm gap,120 ma/cm 2, 35 C, 20 min, 1mg/cm 2 /min MRR. 34
µecm+ecp: CP Titanium Zoom in After µecm+ecp, Area RMS= 42 nm After µecm+ecp Area RMS= 20 nm ECM: Sample A12,50kHz,25-0V, 211mA,504 ma/mm 2,50um, 90s, (50g KBr+15g NaNO 3 +500g H 2 O). ECP: (60 g/l, 99%, AlCl 3 +280 g/l, 98+%, ZnCl 2 + 300 ml/l, C 3 H 8 O +700 ml/l, USP-200 proof, C 2 H 5 OH) at 25v DC, 10 mm gap,120 ma/cm 2, 35 C, 20 min, 1mg/cm 2 /min MRR. 35
µecp: CP Titanium Zoom in After ECP of as-received material. Area RMS= 10 nm After ECP of as-received material. Zoom-in area RMS= 3.4 nm Area RMS within a grain = 2 nm ECP: (60 g/l, 99%, AlCl 3 +280 g/l, 98+%, ZnCl 2 + 300 ml/l, C 3 H 8 O +700 ml/l, USP-200 proof, C 2 H 5 OH) at 25v DC, 10 mm gap,120 ma/cm 2, 35 C, 20 min, 1mg/cm 2 /min MRR.
SUMMARY 1) Measurement of machined surface finish Comparison Profilometry Interferometry Scanning probe microscopy (STM and AFM) 2) Modeling of machined surface Turning Ball-end and flat-end milling Macro vs micro machining 37