Meaning
Ultra precision machining positioned at the final tooling phase generates optical quality mould inserts without requiring secondary polishing steps. Single point diamond turning uses single crystal diamond cutting tools on high stiffness lathes to produce nanometer surface finishes on non ferrous mould cavities. The process governs shape accuracy and surface finish on optical moulds used for injection moulding polymer lenses.
Application of this technique is limited to non ferrous metals like nickel or copper, as ferrous steels cause rapid chemical wear of the diamond edge.
Substrate Machinability
Direct machining of steel with diamond tools causes rapid carbon diffusion, destroying the cutting edge within seconds of contact. Toolmakers overcome this physical boundary by electrodeless nickel plating the tool cavity before precision turning. Electroless nickel phosphorus alloys provide an amorphous structure that cuts cleanly without inducing tool vibration or micro chipping.
Precision control of the nickel plating thickness ensures adequate stock removal during diamond turning without exposing the underlying steel substrate. Optical inserts machined in nickel yield surface roughness values below five nanometers root mean square. Resins moulded against diamond turned inserts mirror these sub nanometer details, producing high clarity lenses without post moulding surface operations.
Optical Form Accuracy
Form errors on lens cavities directly distort light transmission in injection moulded optical components. Submicron contour accuracy achieved through diamond turning eliminates manual hand polishing, which typically degrades surface figure. Machine tool stiffness and environmental temperature control prevent thermal expansion drift during long cutting passes.
Tool Edge Wear
Edge radius decay on diamond cutters alters surface micro geometry and increases cutting forces over time. Microscopic edge chipping creates periodic feed marks across the mould cavity, which replicate as diffraction grating defects on moulded acrylic parts. Regular tool inspection ensures optical mould surfaces maintain specified reflectance standards.
