Grinding Conditions
Wet
Dry
Balls
Cylpebs
F80 (µm)
F80 is the feed size in microns such that 80% of the feed material passes through this size (i.e., 80% passing size of the feed).
Wi (kWh/t)
Wi is the Bond Work Index: the specific energy (kWh per ton) required to reduce the material from infinite size down to 100 µm. It measures the grindability of the ore—the higher the Wi, the harder the material.
Bulk density S (g/cc)
S is the bulk density of the grinding material in grams per cubic centimeter. Higher density means heavier material load, which affects energy transfer and grinding efficiency.
Speed C (% of Nc)
C is the mill speed expressed as a percentage of the critical speed (Nc). Typical operating range is 60–80% of Nc. Going faster or slower significantly changes grinding dynamics.
Mill diameter D (m)
Result
Constants: A = 2.00, K = 350 (wet)
41.1 mm
Calculated top size
Recommended standard top size:
40 mm
Suggested make-up blend (heuristic):
50% of 40 mm
30% of 30 mm
20% of 25 mm
Assumptions & Notes
Use for
top-up ball size
selection; it does not design the full size distribution.
Valid for conventional ball mills running 60–80% critical speed with typical liners and classification.
Check against plant performance; adjust for very coarse feeds (>4 mm), very small/large mills, or unusual liner/speed setups.
Typical ranges: F80 2–50 mm (2000–50000 µm), Wi 6–25 kWh/t, S 2.6–7.8 g/cc, C 60–80% Nc, D 0.9–7 m.
© 2025 — Calculator logic based on Bond/Azzaroni-style correlation with unit-consistent constants (A≈2.0 for balls; K≈350–355). Use at your own discretion.