AFM Cycle Planner
UniversalEstimate the number of Abrasive Flow Machining cycles, total processing time, and Ra reduction curve for LPBF and DED internal channels. Based on published Ra-decay models — the first public AFM planning calculator for additive manufacturing.
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Ra decay model
Ra(n) = Ra_f + (Ra₀ − Ra_f) · e^(−k · n)
k = k_base · f_grit · f_media · f_mat · f_pressure · f_diameter- Ra(n)
- Surface roughness after n cycles[µm]
- Ra₀
- Initial as-built roughness[µm]
- Ra_f
- Achievable floor roughness (material-dependent)[µm]
- k
- Decay constant — product of correction factors[1/cycle]
- n
- Number of AFM passes[cycles]
Logarithmic Ra decay model (Tzeng & Chen, 2005) adapted for AM internal channels. Material and media correction factors calibrated against published LPBF AFM data.
Application notes
Hydraulic diameter drives abrasive velocity. Channels below 2 mm may require higher pressure or finer grit to achieve target Ra.
Ti-6Al-4V has a hard oxide layer that resists early cycles. Boron carbide media or finer grit reduces surface damage to the oxide-free substrate below.
Ra cannot fall below Ra_f (typically 0.3–0.8 µm for standard media). For sub-0.4 µm targets, follow AFM with electropolishing.
Run 3–5 test cycles on a coupon first. Actual k depends on media batch age, fixture geometry, and machine calibration — this is a planning estimate, not a manufacturing spec.
Sources
- [1]Tzeng, Y-F. & Chen, F-C. (2005) — Robust optimisation of surface quality in AFM — Int. J. Machine Tools & Manufacture 45, 105-116
- [2]Abate, K.M. et al. (2022) — AFM of LPBF IN718 internal channels — Empirical Ra-reduction data for AM passages
- [3]Extrude Hone (Kennametal) — AFM application data — Parameter ranges (manufacturer tier)