NEMA 17 Planetary Gear Motor – High Precision Stepper with 5:1 to 70:1 Gear Ratios

This industrial-grade planetary gear motor combines a 2-phase 4-wire NEMA 17 stepper motor with a compact planetary gearbox, delivering high output torque, low backlash, and excellent positioning accuracy.
Engineered for automation equipment, dispensing machines, surveillance systems, textile machinery, and robotic actuators, this gearbox motor provides reliable performance across a wide range of reduction ratios, including 5:1, 10:1, 20:1, 50:1, and 70:1.

The motor integrates seamlessly into OEM designs and is frequently used by professional planetary gearbox suppliers for precision assemblies.
Its gearbox design is also similar in architecture to 2 stage planetary gearbox generator 20:1 and compact 28mm planetary gearbox 27:1 / 29:1 mechanisms, offering proven reliability in limited-space environments.

Key Features

• High-precision steel planetary gear system
• Low noise and long service life
• 2-phase hybrid stepper with smooth microstepping response
• Multiple exact reduction ratios: 5 / 7 / 10 / 12 / 16 / 20 / 25 / 28 / 35 / 40 / 50 / 70
• Suitable for robotics, automation equipment, instrument drives, and compact industrial machinery

Technical Parameters

Item	Value
Step Angle	1.8° ±5%
Phase	2 phase
Voltage	3.5 VDC
Phase Current	1.0 A
Phase Resistance	3.5 Ω ±10%
Phase Inductance	4.5 mH ±20%
Static Torque	0.14 N·m
Insulation Class	Class B
Insulation Resistance	100MΩ (500V DC)
Ambient Temperature	-20°C ~ +50°C
Ambient Humidity	15%–95%
Motor Weight	Approx. 0.35kg
Recommended Driver	2D4020A

Dimensions

Dimension Item	Value
Motor Body Length	35 mm
Gearbox Length	46 mm
Mounting Hole	31 mm
Shaft Diameter	φ12 mm
Shaft Length	11.2 mm
Flange Size	42 mm

Gear Ratio Levels

Class A (Exact Ratios)	Level 2 Ratios
4, 5, 7, 10, 12, 16, 20, 25, 28, 35	28, 35, 40, 50, 70

Noise & Efficiency

Item	Value
Efficiency	96% (Class A) / 94% (Level 2)
Noise	<55 dB
Backlash	<20 arcmin

FAQ

Open Loop vs Closed Loop?

Open-loop stepper motors operate without feedback, relying on predefined pulse commands.
They are cost-effective and ideal for low to medium-load applications. However, they may lose steps under heavy load or high acceleration.

Closed Loop vs Open Loop Control?

Closed-loop stepper systems use an encoder to monitor rotor position in real time, automatically correcting any deviation.
They provide higher torque at high speed, zero step loss, and smoother motion, similar to servo performance.
Open-loop is simpler; closed-loop is more accurate and stable.

For in-depth engineering analysis, read our related blog:
Why Some High Torque NEMA Gearbox Designs Are Not Achievable

Download Datasheet

Download the full specification sheet for detailed parameters, wiring guide, and performance curves.

📄 Download PDF Datasheet