Physics / mechanism
Single-point diamond turning (SPDT) uses a precisely positioned monocrystalline diamond tool mounted on an ultra-stiff, air-bearing spindle to cut optical-quality surfaces directly — no polishing required. The diamond’s edge radius (~50–100 nm) and the controlled chip-load (depths of cut down to ~10 nm) produce surfaces with roughness Ra < 1 nm and form accuracy to λ/10 or better. CNC tool-path control enables aspheres, free-forms, and diffractive micro-structures in a single setup. Materials: aluminium alloys, copper, PMMA, germanium, ZnSe, CaF₂, silicon — anything ductile enough not to fracture the tool. Hard-brittle materials (glass, SiC) require ductile-regime grinding or hybrid approaches. State-of-the-art machines (Precitech Freeform, Moore Nanotech) hold sub-micron form error across 300 mm apertures.
Competitive landscape
Competing and adjacent routes depend on material and geometry. Conventional polishing (CCP, MRF) handles glass but struggles with free-forms. Precision glass moulding replicates at volume but requires expensive moulds and is aperture-limited. Slow-tool-servo and fast-tool-servo are SPDT sub-variants that push non-rotationally-symmetric surfaces. Ion-beam figuring corrects residual errors post-SPDT but adds cost.
Companies using
Connected ideas
Sources
Frontier (open questions)
- To be added.