KEVOS® MAKEOS · Mechanics
Rotary Index Table Drive Sizing
What torque and motor does this rotary index table need to index in time, and what holding torque during machining?
Sizing of a servo or geared index table: table and fixture inertia, index angle from the number of stations, peak speed and acceleration for a cycloidal or trapezoidal move, table and motor torque through the reducer, motor speed, dwell time in the cycle, and the holding torque the clamp or brake must provide against machining forces.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Table plate mass | kg | Mass of the round table plate. |
| Table plate radius | mm | Radius of the table plate. |
| Stations | Number of stations (indexes per revolution). | |
| Mass of each fixture and part | kg | Mass of one fixture with its part. |
| Radius of fixture centres | mm | Radius at which fixtures sit. |
| Index time | s | Time allowed for each index move. |
| Total cycle time | s | Total time per station including the index. |
| Motion profile | choice | Motion profile of the index. |
| Bearing and seal friction torque | N·m | Friction torque at the table. |
| Reducer ratio | Speed reduction between motor and table. | |
| Reducer efficiency | % | Reducer efficiency. |
| Motor inertia | kg·m² | Motor rotor inertia. |
| Machining force at the fixture (tangential) | N | Tangential machining force at the fixture radius during dwell. |
| Safety factor on holding | Factor on the holding torque. |
Method and formulas
- J = ½ M R² + stations × m_f r_f² (fixtures as point masses).
- Index angle θ = 360° ÷ stations; cycloidal: ω_max = 2θ ÷ t, α_max = 2π θ ÷ t²; trapezoidal (⅓ each): ω_max = 1.5 θ ÷ t, α = 4.5 θ ÷ t².
- Table torque = J α + friction; motor torque = table torque ÷ (i η) + J_m α i; motor speed = ω_max i.
- Holding torque = SF × F_m × r_f.
- Example: a 6-station table indexing in 0.6 s needs 139.34 N·m at the table and 3.7354 N·m at the motor.
Limitations
- Rigid table; reducer backlash and stiffness affect settling time.
- Unbalanced fixtures add gravity torque on tilted tables.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Choose a motor and reducer for a dial table
- Check whether an index time is achievable
- Specify the table clamp or brake for machining loads
Who it is for
- Machine designers
- Automation engineers
- Design engineers
What you get
- Table inertia and index motion
- Table and motor torque and motor speed
- Dwell time and holding torque
Interpreting the result
- Cycloidal motion needs more peak torque than trapezoidal but settles more smoothly.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 171, 2284–2290. Topic reference; no source tables or recommended settings are reproduced.
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