Stepper Motor Selection Guide: Types & How to Choose | Apexwell - Changzhou Apexwell Motor Technology Co., Ltd

Picking the right stepper motor comes down to matching motor type, torque, and control architecture to the actual application — not just choosing a NEMA frame size that looks about right.

MOTOR ENGINEERING KNOWLEDGE Published September 22, 2026 · 7 min read · By Apexwell Engineering Team

A stepper motor is a brushless motor that converts electrical pulses into controlled, incremental rotation, and choosing the right one is more a systems decision than a single spec lookup — it involves motor type, torque margin, driving mode, and open loop or closed loop control together, not a NEMA size picked in isolation. This guide assumes you're already familiar with the basics of how a stepper motor works; if not, start with our beginner's guide first.

What are the main types of stepper motors?

Stepper motors fall into three structural categories. Permanent magnet (PM) motors use a magnetized rotor and are simple and low-cost, at the expense of coarser step angles. Variable reluctance (VR) motors use a toothed, unmagnetized rotor that moves toward the position of lowest magnetic reluctance, offering fast response but lower holding torque with no power applied. Hybrid motors combine both principles in a magnetized, toothed rotor, delivering fine step resolution with useful holding torque — which is why nearly every industrial and OEM stepper motor in use today, including Apexwell's full range, is a hybrid design.

Apexwell's current lineup spans this range by frame size rather than by type, since all of it is hybrid construction: the compact AW20HS (NEMA 8) for space-constrained mechanisms, the mid-range AW57HS (NEMA 23) available across eight body lengths, and the larger AW86HS (NEMA 34) for higher-torque industrial applications — see our full NEMA size chart for the complete lineup.

What are the benefits of using a stepper motor?

● Predictable positioning. Each command pulse corresponds to a defined motor step, so the control system can command a target position simply by counting pulses.

● Simple control architecture. Most open loop applications don't require encoder feedback, which keeps the control system simpler than a servo setup.

● Repeatable motion. For predictable loads within the motor's torque margin, stepper motors deliver consistent, repeatable incremental movement.

● Flexible resolution. Full-step, half-step, and microstepping modes let engineers tune motion smoothness and vibration to the application.

● Wide range of frame sizes. From compact NEMA 8 motors to NEMA 34 and larger, stepper motors scale to fit very different torque and space requirements within a common control approach.

How do you choose the right stepper motor?

Selecting a stepper motor should start with the application's actual requirements, not the frame size:

1. Determine the required torque

Estimate the load torque required during the actual operating cycle, and add a safety margin for acceleration, friction, and load variation — see our guide on how to calculate holding torque for the full method and a worked example.

2. Determine the operating speed

Stepper motor torque falls off as speed increases, so the required operating speed needs to be checked against the motor's torque-speed curve, not just its zero-speed holding torque rating.

3. Select the motor frame size

NEMA frame size sets the mounting footprint, but it isn't a reliable stand-in for capability — two motors with the same NEMA size can have very different body lengths, current ratings, and holding torque. See our NEMA stepper motor size chart for typical torque ranges by frame size.

4. Check the driver

A stepper motor requires a dedicated driver matched to its current and voltage rating. See our guide on how to choose a stepper motor driver for the specs that matter most.

5. Consider open loop or closed loop control

If the load is predictable and occasional step loss is acceptable, open loop control is usually sufficient. Apexwell offers closed loop configurations across most of the range — the AW57HS series, for example, is available with selectable encoder resolutions from 500 to 2000 PPR across eight body lengths and holding torque from 0.55 to 2.5 N·m. For the full open loop vs. closed loop trade-off, see our beginner's guide and our piece on why closed loop steppers are replacing traditional steppers.

6. Check the mechanical interface

Before finalizing a motor, confirm mounting dimensions, bolt pattern, shaft diameter and length, connector or lead-wire type, and available installation space. For OEM projects, these mechanical details can matter as much as the torque rating.

Where are stepper motors used?

Stepper motors are commonly specified wherever equipment needs controlled positioning, repeatable movement, or incremental motion:

● CNC equipment. The AW57HS NEMA 23 closed loop series is specified for CNC routers and mills, and industrial X-Y positioning stages.

● Robotics. The compact AW20HS NEMA 8 series is specified for small robotic grippers and other space-constrained precision mechanisms.

● Medical instruments. Compact stepper motors provide controlled positioning within limited installation space, which is why the AW20HS series is also common in medical instrument positioning.

● Packaging equipment. Indexing and positioning operations often use stepper motors, with closed loop configurations worth considering where undetected step loss would affect production consistency.

● Camera and lens mechanisms, laboratory equipment, and valve actuators. Any application where frame size, torque, speed, and control characteristics need to match a compact, precise motion requirement.

Stepper motor or servo motor?

The right choice depends on the actual torque, speed, load variation, and feedback requirements of the complete motion system, not motor type alone. See our full stepper motor vs. servo motor comparison for a side-by-side breakdown and a decision checklist.

Frequently Asked Questions

What is a hybrid stepper motor?

A hybrid stepper motor combines permanent-magnet and variable-reluctance operating principles in a single toothed, magnetized rotor, providing fine step resolution together with useful holding torque. It's the design behind nearly all industrial and OEM stepper motors in use today.

When should I choose a closed loop stepper motor?

Closed loop is worth considering when an application is more sensitive to step loss, load variation, or undetected position errors — common examples include robotics, packaging, CNC positioning, and precision instruments.

Does a larger NEMA size always mean more torque?

Not reliably. NEMA size only defines the mounting faceplate dimensions. Two motors sharing the same NEMA size can differ substantially in body length, current rating, and holding torque, so the actual torque specification should always be checked directly rather than assumed from frame size.

What information do I need to get a motor recommendation?

Required torque, operating speed, supply voltage, preferred frame size or space constraints, and whether open loop or closed loop control is needed are enough for our engineers to recommend a starting configuration.