5/1/2013 1 Center For Precision Metrology Surface Finishing Processes Brigid Mullany Associate Professor Department of Mechanical Engineering Center for Precision Metrology UNC Charlotte North Carolina, USA Center For Precision Metrology Finishing Processes- High value added Lithography Imaging Metrology Telescopes http://images.businessweek.com/ss/08/07/0717_idea_winners/23.htm http://www.asml.com/asml/show.do?ctx=6720&rid=36951 http://www.zygo.com/?/met/interferometers/&gclid=CM7VvYDRl6gCFSRe7AodDVp1EA http://www.eso.org/sci/facilities/eelt/telescope/dome/ http://www.worldoforthopedics.com/tag/partial-knee-replacement/ www.hiwtc.com/photo/products/37/03/76/376 37.jpg Optics Medical Energy/Aerospace o Challenging geometries o Difficult to machine materials o Tight form and finish specifications Abrasive finishing Image sources
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Finishing Processes- High value added UK Day, B.Mullany.pdf · Loose Abrasive Processes Lapping Polishing Magnetic Assisted Finishing Abrasive Flow Machining (AFM) Drag Finishing
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5/1/2013
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Center For
Precision Metrology
Surface Finishing Processes
Brigid Mullany
Associate ProfessorDepartment of Mechanical Engineering
o Challenging geometrieso Difficult to machine materialso Tight form and finish specifications
Abrasive finishing
Image sources
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Center For
Precision Metrology
Loose Abrasive Processes
Lapping
Polishing
Magnetic Assisted Finishing
Abrasive Flow Machining (AFM)
Drag Finishing
Elastic Emission Machining (EEM)
Vortex Machining (under development at UNCC)
Typical surface finishes, Rq10-7 m 10-8 m 10-9 m 10-10 m
Tumbling
Centrifugal
Turbo Abrasive Machining (TAM)
Common process perceptionso Operator skill dependento Trial and error approacho Expensive
o Process instrumentationo Surface metrologyo Fluid dynamicso Contact mechanics
Collaborators: Mainuddin, Keanini, Williams
Center For
Precision Metrology
Traditional Optics Polishing Process
Applications:o Laser and Lithography opticso Larger one off opticso High throughput of higher quality optics
WorkpieceSlurrydispenser
Polishing tool(Ø 30 cm)
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Center For
Precision Metrology
Polishing Tool Material - Optical PitchPolishing Pitch: o Tree or petroleum based resins o Synthetic versions availableo Shore D: 70 – 80o Highly viscoelastic
Day 239 Day 261 Day 267Day 1
History in Polishing: o First use accredited to Newton in 1700so Synthetic versions available since 2000so Dynamic properties evaluated in 2010*
* B. Mullany, S. Turner, Applied Optics, Vol. 49, No. 3, pp. 442,449, 2010
Center For
Precision Metrology
Tool fabricationo Heat pitch (T < 100 °C)o Pour onto substrateo Cut grooveso Condition: embed abrasives in surfaceo Life span: months →years
Tool: Ø 300 mm
Synthetic pitch : Acculap™ soft
Embedded Ceria particles
Workpiece
Pitch tool
do≈ 3Rq
Pitch tool construction
1 µmThe abrasives embedded in the tool are responisble for material removal 1 mm
SEM of Tool surface
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Center For
Precision Metrology
Pitch Polishing and VibrationsMachine 1 Machine 2
1 10 100 1000 10k0
0.005
0.01
0.015
0.02
Frequency, Hz
g,m
/s2
New MachineOld MachineAccelerometer Noise
Machine 1Machine 2
Machine 1: 6nmMachine 2: 0.6nm
Machine 1: 2 ÅMachine 2: 0.2 Å
Spindle: 20 rpmOverarm: 5rpmLoad: 10N
Mainuddin
Center For
Precision Metrology
Do vibrations affect process metrics?Fused silica samples (Ø 25.4 mm) were polished on both machinesPolishing conditions: Platen speed: 20rpm, Load: 20 kPa, Slurry: 1 mm (250nm) Ceria + H2O
SummarySystem vibrations investigatedo Process variations explainable by vibration signatureso While not shown here – MRRs can be varied by passive damping
or addition of vibrations
Within certain limits the MRR is proportional to input power
Analytical model presented: MRR = MRRcm + MRRflowo Good fit between experimental and theory for wide range of
conditions
Financial Support:o NSF/CMMI/MCME 0747637. Any opinions, findings and conclusions or recommendations
expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation).
Selected papers:o B. Mullany, M. Mainuddin, Annals of the CIRP, 61/1/2012, 555-558, 2012.o B. Mullany, S. Turner, Applied Optics, Vol. 49, No. 3, pp. 442,449, 2010o Mullany, Mainuddin, Williams, Keanini, planned submission to JAP, April 2013