Should I use a servo or a geared motor with a brake for indexing?

It depends on required accuracy and how often the profile changes. A geared motor with a brake is lower cost and simpler to maintain, but stop position varies with brake response, motor coast-down and backlash — fine for coarse, fixed-station indexing. A servo with a matched reducer gives closed-loop accuracy and programmable positions and profiles, which is what you need when positions change often or the stop has to be tightly repeatable.

Why does a servo axis need a reducer if the motor already has enough torque?

Because of inertia, not torque. A reducer divides the load's inertia, as reflected back to the motor shaft, by the square of the ratio, so a 10:1 reducer cuts reflected inertia by a factor of 100. Servo drives tune cleanly only when the reflected load inertia sits within a defined range relative to the motor's own rotor inertia — leave the reducer out, or under-size the ratio, and the axis can hunt or oscillate around the target position even with adequate torque available.

How do I stop a servo axis from dropping a vertical load if power is lost?

Either add a brake motor or a brake module to hold the load when torque is removed, or use a worm-stage reducer at a self-locking ratio — roughly 5:1 and above — which cannot be back-driven by the load. The worm option removes the dependency on a separate brake at the cost of lower efficiency and lower attainable speed than a planetary stage, so it suits gravity axes rather than fast horizontal indexing.

Drive Selection July 11, 2026 • 6 min read

Servo or Geared Motor? Choosing a Drive for Indexing and Positioning

Move to a position, stop, dwell, repeat — indexing looks like a simple job description, but it covers everything from a two-station transfer table to a multi-axis pick-and-place cell. The right drive for it depends less on the machine's size than on how precisely it has to stop, how often the sequence changes, and how fast it has to cycle. Here is how we work through that choice.

The Indexing Problem

Indexing is the class of motion where a load moves from one defined position to the next, stops, dwells long enough for a process step — a fill, a weld, a pick, an inspection — and repeats. Turntables, rotary index tables, transfer conveyors, and pick-and-place slides all fall into this category. Whatever the machine looks like, the drive choice comes down to three questions: how accurately does it have to stop, how often does the number or spacing of positions change, and how many cycles per minute does it need to hold.

Option A: Geared Motor + Brake

The simplest indexing drive is a three-phase motor, a reducer, and an electromechanical brake, switched by contactors or a basic sequencer, with position sensed by a limit switch, a proximity sensor, or a mechanical stop. It is low cost, has few components, and any electrician on site can maintain it without special training.

The trade-off is repeatability. Stop position is set by brake response time, motor coast-down, gear-train backlash, and exactly where the sensor happens to trigger — all of which vary slightly cycle to cycle, so the result is positional scatter measured in degrees or millimetres, not fine fractions of either. The motion profile is essentially fixed too: whatever speed and deceleration the motor and brake deliver is what you get, with no programmable ramps or S-curves. None of this is a problem for coarse, fixed-station indexing — mechanical hard stops, a small number of stations, general material handling — where "close enough, every time" is genuinely close enough. See our geared motors page for the ranges we supply.

Option B: Servo + Reducer

Where positions or profiles need to change, or where the stop has to be accurate, a servo drive earns its keep. A servo motor with encoder feedback and a closed-loop drive lets a motion controller or PLC command any number of positions, speeds, and acceleration/deceleration profiles in software — change the recipe, and you change a number, not the mechanical stops. Because the drive continuously compares commanded position against actual encoder position and corrects the error, repeatability is set by encoder resolution and mechanical stiffness, not by how consistently a brake happens to grab.

Almost every servo axis carries a reducer between motor and load, and the reason is inertia, not just torque or speed. A reducer divides the load's inertia, as seen from the motor shaft, by the square of the ratio — a 10:1 reducer cuts reflected load inertia by a factor of 100. Servo motors are tuned to control a load whose reflected inertia sits within a defined multiple of the motor's own rotor inertia; get that ratio into the drive's stable range and the axis accelerates, stops, and holds cleanly. Get it wrong — usually by leaving the reducer out, or picking a ratio that is too low — and the axis hunts or oscillates around the target position no matter how the drive is tuned. This is why inertia matching, not just torque sizing, decides how well a servo axis actually performs; see our servo drives and planetary gearboxes pages for how we size the two together. Anand Gears works with Delta's ASDA servo platforms; we are an independent supplier, not an authorised distributor or OEM for Delta, and we confirm exact model specifications against the manufacturer's datasheet at the time of quotation.

Hybrid Option: Servo With a Self-Locking Worm Stage

Planetary and helical reducers are efficient and low-backlash, which is exactly what most servo axes want — but they are generally back-drivable: if servo torque is lost to an e-stop or a power failure, a vertical or overhung load will fall unless something else holds it, which usually means adding a brake motor or a separate brake module.

For gravity axes — lift stations, tilt tables, anything the load would backdrive under its own weight — pairing the servo with a worm-stage reducer at a self-locking ratio removes that dependency. Anand Gears' worm gearboxes are self-locking at ratios of roughly 5:1 and above, meaning the worm cannot be back-driven by the load, so the axis holds position with no power and no brake. The trade-off is the worm stage's lower efficiency and generally lower attainable speed compared with a planetary stage, so it is a choice for safety and simplicity on a gravity axis, not for a fast horizontal index. See our worm gearboxes page for ratio ranges.

Which One — the Decision Factors

Factor	Geared Motor + Brake	Servo + Reducer
Accuracy required	Coarse, sensor- or stop-limited	Tight, repeatable, closed-loop
Cycle rate	Slow to moderate starts per minute	High cycle rates, tight dwell control
Profile changes	Fixed, rarely changes	Positions and speeds change often
Duty	Light to moderate starts/stops	Continuous, high-frequency indexing
Gravity or overhung load	Self-locking worm stage or brake	Self-locking worm stage or brake
Budget and complexity	Fewer components, simpler commissioning	Higher component count, needs motion tuning

Most machines we quote are not purely one or the other — a line might run brake motors on its transfer stations and a servo on the one axis that actually needs programmable positioning. Tell Anand Gears the load, the required accuracy, and the cycle rate, and we will size the motor, reducer, and drive as one matched package rather than three separate purchases. Call +91 98203 83719 or write to anandgears@gmail.com.