What is rated torque versus peak torque?
Rated torque is what a joint can deliver continuously without overheating; peak torque is what it survives for a short time. Size the axis on rated torque and reserve peak for transients.
Every joint datasheet carries at least two torque numbers, and picking the wrong one is the most common sizing error. Rated torque is the continuous limit — the load the joint can hold or cycle against indefinitely at a stated ambient temperature, set by how much heat the motor and the gear can shed. Peak torque is the mechanical limit the gearbox and structure survive for a short time, usually seconds, often quoted at stall.
Two joints with identical rated torque can differ by 30% in what they actually deliver over a shift, because the number that decides it is the duty cycle the rating was measured at. A figure quoted at 20% duty and a figure quoted at 60% are not the same joint, whatever the row says.
Put these in writing before you buy
- Rated torque, at your duty cycle and ambient temperature — not "typical".
- Peak torque and how long it may be held — plus what happens thermally afterwards.
- Allowed moment load and axial load — the bearing and the gear, not just the torque path.
- Thermal behaviour — whether the joint derates, and whether there is a temperature sensor you can read.
Work through it with how to size joint modules, or send us the axis and the trajectory.
FAQ
Can I run a joint at peak torque if the duty cycle is low?
Briefly, yes — that is what peak is for. But repeated peak events at a low duty cycle still deposit heat, and the limit that eventually bites is thermal. Ask for the allowable peak duration and the recovery time.
Why do two joints with the same rated torque behave differently?
Usually because the ratings were measured under different duty cycles, different ambient temperatures, or with different thermal paths into the structure. The torque number is the same; the continuous capability is not.