Assembly example: vertical Z-axis lift
A combined example for a vertical Z axis: a gravity load flows through four selection steps, highlighting lift torque, a self-locking check and sizing a brake to hold the load on power loss.
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
N=v·60/Ph; T_up=F·Ph/(2π·η)/N, F=m·g; η'=2−1/η; T_bd=F·Ph·η'/(2π)/N; T_brake≥T_bd·Kb
Example using default values
m=15 kg, Ph=10, Ø16, v=200 mm/s → T_up≈0.26 N·m, η'≈0.89 (not self-locking), brake≥0.31 N·m, T≈0.67 N·m @1200 rpm
Source: THK/HIWIN (ball screw, back-driving, LM guide); Oriental Motor Sizing (vertical); Euler column; KTR/NBK (coupling).
Frequently asked questions
Does a ball screw self-lock to hold the load on power loss?
No. A ball screw is highly efficient (η~0.9) and back-drives easily: reverse efficiency η'=2−1/η > 0 means gravity spins the screw and lowers the load. A vertical axis must use a fail-safe (power-off) brake motor or an external brake.
How much brake torque is needed?
At least the gravity back-driving torque T_bd=F·Ph·η'/(2π)/N times a brake safety factor Kb (typically 1.5–2). Prefer a brake that engages on power loss for fail-safe holding.
How does sizing a vertical axis differ from a horizontal one?
Vertical: the load is gravity (F=m·g, always present, independent of friction), so lift torque is much larger; you must check buckling under weight, holding torque at standstill, and a brake. A horizontal axis only overcomes friction, so load torque is small.
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