Assembly example: rotary index table
A combined example for a gearbox-driven rotary index table: the same problem flows through four selection steps using standard inertia and torque formulas.
How to use
- Enter the calculation conditions
Enter the dimensions, loads, speeds or operating conditions requested by the form.
- Run the calculation
The tool applies the formulas shown on this page to the entered values.
- Review the result
Review the resulting specification and checks, then verify them against the cited source, current standard and real operating conditions before use.
Core formula
J=(1/8)mD²+Σmr²; α=ω/t₁; T_table=J·α+T_fric; T_motor=T_table/(N·ηg); T=T_motor·Sf
Example using default values
disc 15 kg/Ø300 + 6×2 kg@r120, n=30 rpm, N=10 → J≈0.342, T_table≈8.15 N·m, T_motor≈1.81 N·m @300 rpm
Source: Oriental Motor Sizing (rotary/gearbox mechanism); KTR/NBK (coupling service factor).
Frequently asked questions
How are disc and workpiece inertia computed?
The disc uses J=(1/8)·m·D² (solid disc about its center). Workpieces are treated as point masses at radius r, so J=Σ m·r² — a conservative approach; for large workpieces, add their own inertia about their center.
Why is the acceleration torque J·α?
Newton's second law for rotation: T = J·α, with α = ω/t₁ the angular acceleration. This is the equivalent of Ta = J·n/(9.55·t₁), since 9.55 = 60/2π.
Why does an index table need a low-backlash gearbox?
Backlash (gear lash) shifts the stop angle each index, directly affecting station positioning accuracy. For precise indexing, use a low-backlash planetary gearbox or an index-cam mechanism.
MINATA — minatavn.com