How to Select an Integrated Stepper Motor: A Six-Step Method (2026 Guide)

Bottom line: Selecting an integrated stepper motor takes six steps — define the load and motion profile, calculate the required torque, choose the frame size, decide open-loop or closed-loop, pick the communication interface, then specify accessories and special machining. Below is each step in order, followed by a quick-reference table.

1. The six-step method at a glance

Table: Six-step selection method

Step	What to decide	Basis
1	Load type and motion profile	Horizontal or vertical load, stroke, max speed, accel/decel time
2	Required torque	Load torque + acceleration torque, times a safety factor
3	Frame size and body length	Torque headroom and mounting space: 28 / 42 / 57 / 86 mm
4	Open-loop or closed-loop	Whether step loss is acceptable; required accuracy and speed stability
5	Communication interface	Host system bus: CAN / CANopen / RS485 / RS232
6	Accessories and machining	Brake, shaft extension, shaft key, lead screw, gear, timing pulley

2. Step 1 — write down the load and motion profile

Most selection errors start here. Four things must be clear: whether the load is moved horizontally or lifted vertically (vertical axes need holding force and usually a brake), the stroke length, the maximum speed, and how much accel/decel time is available. Shorter accel/decel times mean higher acceleration torque and push the model up a size.

3. Step 2 — calculate torque with a safety factor

Required torque = load torque + acceleration torque. In practice, multiply by a safety factor of roughly 1.5–2 to get the reference torque for selection. One critical point: a stepper motor's torque falls as speed rises, so compare against the torque at the operating speed, not the static holding torque. This is the single most common beginner mistake.

Torque–speed curves for specific models are in the official Limaisheng product manual. Mark your operating point on the curve and confirm it sits below the curve with margin.

4. Step 3 — choose the frame size

Table: Frame size selection reference

Frame	Typical installation	Selection tip
28 mm	Micro equipment, test instruments, small slides	First choice when space and load are both minimal
42 mm	Compact automation equipment, multi-axis stations	The general-purpose workhorse with the best cost-performance
57 mm	Medium loads needing higher torque	Richest model range; most derivatives live here
86 mm	Larger loads and higher inertia	Choose when more torque is required

Within one frame there are several motor lengths (34 / 40 / 41 / 48 / 56 mm); longer bodies deliver more torque. If the frame cannot change but torque is short, first check whether a longer body fits — jumping to a larger frame cascades into mounting holes and overall dimensions.

5. Step 4 — open-loop or closed-loop

Open-loop (no "A" in the model code) is lower cost and simpler, and suits stable loads with no overload risk and no sensitivity to step loss. Closed-loop ("A", the STM-M integrated stepper servo series) adds closed-loop algorithms for better accuracy and speed stability, and is the right choice in three cases: the load fluctuates and overload is possible; higher positioning accuracy is needed; or low-speed operation must be vibration-free with no step loss.

6. Step 5 — choose the communication interface

Table: Communication interface comparison

Model code	Interface	When to use
CANopen	CANopen bus	Multi-axis networks needing a standard motion-control protocol; widely supported by mainstream PLCs
CAN	CAN bus	Host systems running a custom CAN protocol
485	RS485	Serial networks with few axes and cable-cost sensitivity
232	RS232	Point-to-point links, single-axis commissioning or built-in machine control
PI	Pulse control signal	Retrofits reusing existing pulse-type controllers
AI	Analog control	Applications where speed or position is commanded by an analog signal

7. Step 6 — accessories and special machining

The model suffix lets you lock in accessories up front and avoid a second purchase: brake (B) — required for vertical axes and any position-holding-on-power-loss case; shaft extension 0 (standard) or 1 (non-standard); shaft key S (plain), F (milled flat), K (half-moon key), H (flat key), M (through-hole mounting); special machining A (gear), B (lead screw), C (peristaltic pump), G (timing pulley). For direct linear motion, choose a lead-screw model (STM28M / STM35M / STM42M / STM57M) and skip the coupling and extra structural parts.

8. Model code quick reference

Structure: STM - frame - length - operation - communication - feature - shaft extension - shaft key - special machining - brake. So STM 57 56 A - 485 - H - 0 F S B means: 57 mm frame, 56 mm body, closed-loop control, RS485, high-power control, standard shaft length, milled-flat shaft, no special machining, with brake.

9. Five common selection mistakes

Mistake 1 — using holding torque as working torque. Stepper torque drops with speed; always read the torque at the operating speed.

Mistake 2 — skipping the safety factor. Load variation, supply variation and temperature rise all eat margin; keep 1.5–2×.

Mistake 3 — no brake on a vertical axis. The load will fall when power is cut — a safety risk. Choose a "B" model for vertical axes.

Mistake 4 — selecting on torque alone. Changing frame size changes mounting holes, couplings and structural parts. Confirm space before locking the frame.

Mistake 5 — ignoring protocol matching. The communication code in the model must match the host bus, or you will need an extra converter.

10. FAQ

Q1: How do I tell open-loop from closed-loop quickly?Check for "A" in the model code — with A it is closed-loop (integrated stepper servo).

Q2: Torque is short — longer body or bigger frame?First check whether the same frame offers a longer body (34 / 40 / 41 / 48 / 56 mm); only step up a frame if that is not enough.

Q3: What about vertical mounting?Choose a brake-equipped model (suffix B) and verify the holding capability with power removed.

Q4: Which interface is best for a multi-axis network?CANopen is the more general choice with good PLC and motion-controller support; RS485 works when there are few axes and cost matters.

Q5: What if I need IP65 or a wide temperature range?Choose the STMP series (IP65) or STMPW57-M (wide temperature).