(B-axis) fly-cut adapter main spindle (C-axis)

LFM 

Universität Bremen 

Prof. Brinksmeier 

Möglichkeiten und Grenzen 

der Ultrapräzisionsbearbeitung 

im optischen Formenbau 

Werner Preuß 

LFM Labor für Mikrozerspanung 

Universität Bremen

LFM 



University of Bremen and Technology Park 

Schie 0018a-e

Diamond machining Precision grinding 

• Development of diamond 

cutting processes 

• Multi-axis machining 

• Generation of microstructures 

Modeling and simulation 

• Computer simulation of cutting 

processes 

• Molecular dynamics simulation 

• Finite element analysis 

LFM 



• Deterministic micro grinding 

• Ductile grinding of glass 

• Precision grinding of steel and 

ceramics 

Measuring and testing 

• Figure evaluation 

• Investigation of surface topography 

• Assessment of subsurface damage 

Polishing 

• Development of CNC-polishing 

techniques 

• Polishing of aspheric and 

freeform surfaces 

• Polishing of micro-structured 

surfaces 

Science and Technology at the 

Laboratory for Precision Machining

1 Mikrozerspanung 

2 Rotationssymmetrische Flächen 

3 Freiformflächen 

4 Strukturierte Oberflächen 

LFM 


Prof. Brinksmeier

form deviation 

[mm] 

1 

0,1 

0,01 

0,001 

UP 

LFM 


Prof. Prof. Brinksmeier 

P 

F 

R 

fine machining 

precision machining 

ultraprecision machining 

0,01 0,1 1 10 

rough machining 

average surface 

roughness [µm] 

OR 677e 

(Br 1401e) 

Classification of mechanical machining processes

LFM 



controlled axes: 

X, Z, B 

bearing: 

main spindle: aerostatic 

x,z: double V-grooves with cylinder rollers 

drives: 

DC-motors with ball bearings 

positioning systems: 

interferometer and / or decoder 

vibration isolation: 

granite base + passive air-cushions 

control: 

Fanuc-3-axes control 

resolution: 10 nm 

working volume: 

range ∆ x = 405 mm, ∆ z = 230 mm 

max. turning diameter: 780 mm 

accuracy: 

contour accuracy: < 0,5 µm 

Moore M18 Aspheric Generator 

LA 0569e

Nanotech Nanotech 500 500 FG FG 

linear linear axes: axes: 3 3 (hydrostatic) (hydrostatic) 

rotary rotary axes: axes: 2 2 (air (airbearing) bearing) 

grinding grinding spindle: spindle: 1 1 (hydrostatic) (hydrostatic) 

machining machining volume: volume: 300 300 x x 200 200 x x 300 300 mm³ mm³ 

load load capacity: capacity: 90 90 kg kg 

accuracy accuracyof of linear linear motion: motion: < 0.3 0.3 µm µm 

Ref.: Nanotechnology 

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Radial, Radial, axial axial run-out: run-out: 

B-, B-, C-axis:< C-axis:< 50 50 nm nm 

A-axis: A-axis: < 100 100 nm nm 

angular angular resolution: resolution: 

B-, B-, C-axis:0.65“ C-axis:0.65“ 

resolution resolutionof of CNC: CNC: 10 10 nm nm 

diamond turning precision grinding 

Nanotech 500 Freeform Generator 

OR 1026

complete machine tool 

(covers removed) 

Ref.: Precitech 

LFM 



4 axes axes • • 3 linear linear 

• • 1 rotary rotary 

processes: processes: • • fly-cutting fly-cutting 

• • raster raster milling milling 

• • ball-end ball-end milling milling 

Precitech Freeform 3000 

ball-end milling 

OR 1025

straight straight knife: knife: 

b > 3 mm; mm; ε ε = 135°; 135°; 

α = 6 °; °; γ γ = 0° 0° 

radius radius tool: tool: 

rε r = 

ε = 6000 6000 µm; µm; 

α = 6 °; °; γ γ = 0° 0° 

LFM 



5 mm 


rε r = 

ε = 50 50 µm; µm; 

α = 6 °; °; γ γ = 0° 0° 


rε r = 

ε = 760 760 µm; µm; 

α = 6 °; °; γ γ = 0° 0° 

Monocrystalline diamond tools 

- straight knife and radius tools - 

OR 190e

Pointed tool: monocrystalline diamond tool 

nose angle ε = 70°30’ 

rake angle γ = 0° 

clearance angle α = 7° 

cutting edge radius r ß < 50 nm 

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50 µm 

Pointed tool for machining of V-shaped grooves 

La 0660e

cutting edge 

clearance face 

1 µm 

1 µm 

r β 

LFM 



rake face 

diamond tool: 

tool nose radius: r ε = ε = 760 µm 

cutting edge radius: r β < β < 0.1 µm 

rake angle: γ = 0° 

clearance angel: α = 6° 

-1.0 

µm 

0.0 

section 

Cutting edge of a diamond tool 

determining the 

cutting edge radius 

envelope 

circle: 

d = 0.2 µm 

-1.0 

0 1,0 2,0 3,0 mm 4,0 

OR 194e

Chip area true to scale 

r ε = 760 µm 

f = 5 µm 

a p = 5 µm 

LFM 



diamond tool 

r ε 

Chip area in diamond turning 

f 

a p 

OR 047e

electroless nickel OFHC copper 

LFM 



process: plunge cut 

cutting speed: tool nose radius: v c = c = 100 mm/min 

r ε = ε = 5 µm 

Material response 

OR 139e

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cutting direction 

process 

face turning 

spindle speed: n = 500 min 

feed: f = 4,8 µm 

lubricant: mineral oil (spray mist) 

tool 

monocrystalline diamond 

tool nose radius: r ε = 0,76 mm 

cutting edge radius: r β < 0,05 µm 

clearance angle: α = 6° 

rake angle: γ = 0° 

workpiece 

material:electroless deposited nickel 

(amorphous NiP with 

approx. 11% Phosphorous) 

roughness 

R a = 3,4 nm 

R q = 4,1 nm 

R = 27,4 nm 

max 

Diamond turned electroless nickel 

-1 

OR 0916





LFM 


Prof. Brinksmeier

LFM 


Prof. Brinksmeier

LFM 


Prof. Brinksmeier

LFM 


Prof. Brinksmeier

LFM 


Prof. Brinksmeier





LFM 


Prof. Brinksmeier

LFM 



Kinematics of SPDT with fast tool servo 

Gri 0405

LFM 



Kinematics of raster fly-cutting 

Gri 0421a

LFM 



Spiral milling

SPFC surfaces are 

composed of tiny “scallops”: 

W f 

W c 

LFM 



feed direction 

rc : radius of fly-cutter 

rd : radius of diamond 

depth in cutting direction: w 2 

c / (8rc ) 

depth in feed direction: w 2 

f / (8rd ) 

Topography of SPFC-surfaces 

cutting direction 

OR 885 

(JS 0318e)

LFM 



Chip geometry and surface topography for 

Single-point Fly-cutting (SPFC) 

OR 884 

(JS 0279)

LFM 



area: 

1.23mm x 0.98mm 

Ra = 7.56nm 

Rq = 11.97nm 

spacing of raster lines: 

50µm 

tool nose radius: 

10mm 

down milling mode 

Gri 0423 

White-light interferometric image of raster fly-cut 

bi-conic mirror for IRMOS

LFM 



Down-milling versus up-milling 

LA 1002

LFM 



NC-programming for raster fly-cutting 

OR 883

Quelle: MEOS 

LFM 



F-Theta lens system 

OR 873

Quelle: Corning 

LFM 



F-Theta lenses and molding insert 

OR 876

Aspherical Mirror 

Quelle: Siemens VDO Automotive 

LFM 



Windshield 

Driver 

Head-up Display 

TFT (Thin-Film-Transistor) 

Display 

Lightsource with Dimmer 

OR 347

X 

y 

workpiece: 

• Ø 50 mm, AlMg3 

• roughness calculated 

Rt,kin = 10 nm (fc ) 

Rt,kin = 5.6 nm (fr ) 

• roughness measured 

(WLI, 1300µm x 980 µm) 

Ra = 4.8 nm 

• inclination in xy-plane: ϕ = 10° 

LFM 



z 

diamond tool: 

•r ε = 5 mm (half arc) 

process (spiral ball-end-milling): 

•ap = 20 µm 

•fc = 20 µm 

fr = 15 µm 

• n = 5000 rpm 

x 

Y � 

Spiral ball-end-milling 

of a free-form reflector 

z 

f r 

f c 

OR 1010





LFM 


Prof. Brinksmeier

LFM 



Types and generation of Fresnel lenses

LFM 



Injection mold for bifocal intraocular lenses

LFM 



PMMA-Linse 

1µm-Stufe

Hybrid lens with total internal reflection (TIR) 

– 4 cm x 4 cm 

– 625 elements per square meter 

LFM 



hybrid lens 

heat sink solar cell 

aspherical lens 

Realization of novel optical design concepts- 

Solar cell concentrator (hybrid PMMA lens)

LFM 



Mould for primary TIR-R lenses (left) and 

mould for dioptric secondary lenses (right)

LFM 



Photo of the individual parts of the mould 

for primary TIR-R lenses

LFM 



Prototype of the photovoltic system 

Ges 299

front view 

n 

n 

a p 

LFM 



top view 

spindle 

workpiece 

counter-weight 

tool 

rotary-table 

x-slide 

z-slide 

100µm 

15.3 µm 

0.0 µm 

0.0 mm 

Fly-cutting of microprisms 

0.5 mm 

0.0 mm 

0.5 mm 

OR 0674e

LFM 



Conventional and new open ring light system

LFM 



Mold design for the new open ring light system

Nanotech 500 Freeform Generator 

z-slide 

y-slide 

main spindle 

(C-axis) 

fly-cut 

adapter 

LFM 



siedeview 

diamond 

tool 

mold 

rotary table 

(B-axis) 

x-slide 

Raster-milling of spherical cavities 

on a 60° conical mold

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Aluminium test mold with 3 microstructured 10° areas

LFM 



60° microstructured conical mold 

And injection molded replica

LFM 



Advertisement for 2003 movie

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Geometrische Formen 

möglich nicht möglich 

Asphären Hinterschneidungen 

diffraktive Strukturen Strukturen < ca. 10µm 

Freiformflächen Aspektverhältnisse > ca. 2:1 

Polygone Übergangsradien < ca. 10µm 

prismatischen Flächen lokale Krümmungsradien 

facettierte Flächen < ca. 10mm (Zeilenfräsen) 

u.v.a.m. < ca. 10µm (Kugelkopffräsen)

LFM 



Oberflächenqualität 


Formtreue: lokale Tangentenfehler: 

ca. 0.1µm PV - 2µm PV < ca. 1‘ (z.B. 30nm auf 0.1mm) 

Rauheit: 

ca. 5nm Ra - 10nm Ra

LFM 



Werkstoffspektrum 


NiP (chemisch Nickel) Nickel 

Neusilber (CuNiZn) Stahl 

Messing 

Aluminium 

Umweg über galvanische Abformung

(B-axis) fly-cut adapter main spindle (C-axis)

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