The Benefits of Gearboxes —
and When to Pick Integrated Gearmotors
Incorporating a gearhead into your application vs. a servo motor alone can offer several advantages related to performance and cost.
By Jeff Nazzaro, Product Manager, Parker Hannifin
Only about one-third of motor-driven motion systems use gearing, even though gearheads benefit size-constrained applications and those running at 1,000 rpm or less. Other advantages of using a gearhead with a servomotor abound.
Torque multiplication: Gearheads provide a mechanical advantage when mounted to the motor output shaft. The number of gears, and the number of teeth on each, create a mechanical advantage defined by a ratio. If a motor generates 100 lb-in. of torque, attaching a 5:1 gearhead generates output torque approaching 500lb-in. depending on gearhead efficiency.
Speed reduction: Gearheads are often called gear reducers because most increase output torque while decreasing output speed. A motor running at 1,000 rpm fitted with a 5:1 ratio gearhead outputs 200 rpm. This speed reduction improves system performance because many motors do not operate efficiently at low rpm.
Consider a stone-grinding mechanism that must run at 15rpm. At this speed, motor cogging makes grindingwheel rotation inconsistent. The variable resistance of the stone being ground also renders wheel rotation unpredictable. In contrast, fitting a 100:1 gearhead to the motor lets the latter run at 1,500 rpm. The motor-gear-head combination provides more-consistent output force and smooth wheel rotation despite friction and load variations.
Inertia matching: Over the past 20 years, servomotor manufacturers have introduced lightweight materials, dense copper windings, and high-energy magnets for motors that generate more torque for a given frame size. While beneficial, this trend has increased the risk of inertial mismatches between servomotors and the loads they control.
