Lesson 6 – Surface Roughness & Subsurface Damage

What You Will Learn

• List variables that influence roughness: pad, slurry, forces, speeds, material
• Explain why a shiny surface can hide pits, holes, and subsurface damage
• Relate removal rate to texture and wavefront outcomes
• Use speed averaging concepts to stabilize finish
• Set inspection practices that catch hidden defects early

Roughness Drivers

Surface roughness is influenced by pad durometer, slurry type/particle size, pH, concentration, applied forces, speeds/ratios, part preparation, and material. Optimize these holistically for both cosmetics and wavefront quality.

Beware the Shiny Trap

A shiny surface is not necessarily finished. Look for pits, holes, and subsurface damage—the defects beneath the surface that compromise performance. Confirm via appropriate microscopy and scatter/roughness instrumentation.

Process Stability

Use speed averaging and controlled hydrodynamics to maintain consistent texture. Track temperature and slurry renewal to prevent intermittent micro‑scratching.