The development trials used 50.8 mm × 3 mm CaF₂ blanks (Crystran) on a Lapmaster 12 polishing system. Multiple pad types were evaluated – MHS15S, SUBA IV, and POLITEX – each offering distinct compressibility and hardness profiles. Surface roughness was measured with a ZeGage Pro HR Coherence Scanning Interferometer, providing precise 3D topography data at multiple surface locations (center, mid-radius, and edge).

The Results

• Speed and consistency: Increasing pressure from 0.3 psi to 1.6 psi produced a 3.5× faster material removal rate with no loss in surface quality.
• Process stability: Even under higher pressures, the polished surfaces exhibited uniform, low roughness values.
• Diamond makes a difference: Formulations containing diamond abrasives achieved faster removal rates while maintaining the same level of surface finish as those without diamond.
• The optimized two-step process:
• 3 µm AlumaGem® on MHS pad at 1.6 psi
• 0.25 µm AlumaGem® on POLITEX pad at 0.3 psi

Based on literature, low pressures have traditionally been recommended for processing CaF₂ to avoid subsurface damage and surface defects. However, Pureon’s findings challenge that assumption: higher pressures not only preserved the surface quality but also delivered significantly improved removal rates. Likewise, AlumaGem suspensions containing diamond proved markedly faster than identical formulations without diamond, yet achieved equivalent low surface roughness – demonstrating that higher efficiency no longer requires compromise.

This combination effectively removes grinding damage and yields a smooth, defect-free surface, proving that higher pressures – once considered unsuitable for CaF₂ – can in fact enhance both efficiency and consistency.