Winder / Unwinder Torque Calculator
Compute the required torque-speed envelope from tension, roll diameters and line speed — scanned across the whole diameter range from core to full roll.
This calculation carries no empirical coefficient: torque = tension × radius. The tool reports required torque and speed; it does not select a motor. The rotor inertia of the motor to be selected is not included.
Machine role
Drive arrangement
Tension control
Web and tension
MaterialUsed to compute the extra torque term from the growing diameter. Without it that term cannot be computed; negligible for thin film, possibly significant for thick rubber/textile.
Tension per metre of web width — enter it here if your recipe/HMI uses this unit.
If your HMI shows a total force, enter it here; we divide by the width.
Roll dimensions and masses
The figure your plant weighs. This input firms up the dynamic (acceleration/stopping) torque; the continuous tension torque does not depend on it.
The core is treated as its own inertia at its own diameter — near the core it dominates the dynamic torque.
Enter it if known. If not, accelerate the empty system in a controlled way and report the measured torque — we back-calculate it.
Motion and friction
Time from standstill to line speed. If empty, 10 s is assumed and stated in the result.
A fast stop with the drive active. A power-loss emergency stop is out of scope here (mechanical brake).
Enter if measured — friction is an absolute load, not a percentage of tension, and it can dominate at low tension.
If you know your existing drive (optional, for comparison)
We show the installed continuous torque next to the calculated need.
Required Torque-Speed Envelope
Envelope across the diameter
Torque is scanned from core to full diameter. Full roll is NOT assumed to be worst: fixed-inertia torque grows as the radius shrinks, so the worst point can be at the core.
| Diameter (mm) | Speed | Tension torque | Continuous | Acceleration | Braking |
|---|
Assumptions and scope
Request a quote for this torque and speed
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