Goal:
Demonstrate the surface finish and form accuracy achievable when grinding glass with a Levicron® ultra precision spindle
Process:
Freeform XZC spiral glass grinding on a Nanoform® 250 ultragrind specifically designed for flood coolant applications. Starting with a flat blank removed 183 µm at the clear aperture.
Part Details:
Material: BK7 glass
Diameter: 40.0 mm
Clear aperture: 26.3 mm x 22.29 mm (oversized blank used for convenience)
Freeform surface: defined by Zernike polynomials
Process Details:
Grinding wheel:
Roughing: 12.05 mm diameter/metal bond wheel Semi-finish & finish – 15.84 mm diameter/ #1800 Resin bond wheel
Grinding spindle speed (finish pass): 30000 rpm (24.9 m/min wheel OD speed)
Grinding surface speed (constant surface speed grinding): 1400 mm/min (11 rpm @ edge to 125 rpm @ center
Depth of cut: Roughing – 2 passes at 5 µm Semi finish – 10 passes at 2 µm Finishing – 1 pass at 0.5 µm Total time: 267 min
Set up
Grinding in Process
Results:
Surface finish: 25.0 nm rms
Subsurface damage: 4 µm
Form accuracy: 6.34 µm PV (spec < 8 µm)
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