High precision 20mm pm stepper motor with circular gearbox

Short Description:


Model No.: SM20-13GR

Motor type Bipolar 20mm gear stepper motor
Step angle 18 degree
No. of phases 2 phases
Lead screw type Φ3D2.5
Coil resistance 9.2Ω/phase
Minimum order quantity 1unit



Product Detail

Product Tags


This is a circular gearbox with a 20mm PM stepper motor.

The resistance of the motor is selectable from 10Ω, 20Ω, and 31Ω.

The gear ratios of the circular gearbox, the gear ratios are 10:1,16:1,20:1,30:1,35:1,39:1,50:1,66:1,87:1,102:1,153:1,169:1,210:1,243:1,297:1,350:1,
The efficiency of circular gearbox is 58%-80%.
The larger its ratio, the slower the output shaft rotation speed and the higher the torque.
The customer evaluates the gear ratio according to the torque required.

If you are interested in purchasing some samples for testing, please feel free to contact us.


Model No. SM20-13GR
Motor diameter 20mm
Gearbox type 13GR Cylinder gearbox
Drive voltage 6V DC
Coil resistance 10Ωor31Ω/phase
Number of phase 2 phases(4 wires)
Step angle 18°/gear ratio
Output shaft 3mm D2.5 shaft
Gear ratio 10:1~350:1


Design Drawing


Round Gear Box Gear Ratio Specifications

Gear ratio 10:1 16:1 20:1 30:1 35:1 39:1 50:1 66:1
Precise ratio 9.952 15.955 20.622 29.806 35.337 38.889 49.778 66.311
Tooth mumber 14 20 18 14 18 18 15 18
Gear levels 2 4 4 3 4 4 4 4
Efficiency 80% 64% 64% 71% 64% 64% 64% 64%
Gear ratio 87:1 102:1 153:1 169:1 210:1 243:1 297:1 350:1
Precise ratio 87.303 101.821 153.125 169.383 209.402 243.158 297.071 347.972
Tooth mumber 15 14 16 15 19 15 15 14
Gear levels 4 4 5 5 5 5 5 5
Efficiency 64% 64% 58% 58% 58% 58% 58% 58%


About circular gear type

1. The gear box has high precision and high efficiency.
2. Round gear box output shaft is generally φ3mmD2.5mm shaft, and the length of output shaft can be customized.
3.The output speed and torque are different for different gear ratios Customers evaluate the gear ratio according to the required torque.
4. The round gear box can also be paired with 15mm stepper motor.
The following chart shows a 15mm stepper motor with a circular gearbox:



Geared stepper motors, widely used in Smart home, personal care, home appliance equipment, smart medical equipment, smart robot, smart logistics, smart cars, communication equipment, smart wearable devices, consumer electronics, camera equipment, and other industries.


Customization service


1. Coil resistance/rated voltage: The coil resistance is adjustable, the higher the resistance, the higher the rated voltage of the motor.
2. Bracket design/slider length: If customers want longer or shorter bracket, there are special design, such as mounting holes, it is adjustable.
3. Slider design: the current slider is brass, it can be replaced with plastic to save cost
4. PCB+cable+connector: PCB design, cable length, connector pitch are adjustable, can be replaced with FPC according to customer's need.

Lead Time and Packaging Information

Lead time for samples:
Standard motors in stock: within 3 days
Standard motors not in stock: within 15 days
Customized products: About 25~30 days (based on complexity of customization)

Lead time for building a new mold: generally about 45 days

Lead time for mass production: based on order quantity

Samples are packed in foam sponge with a paper box, shipped by express
Mass production, motors are packed in corrugated cartons with transparent film outside. (shipping by air)
If shipped by sea, product will be packed on pallets


Shipping Method

On samples and air shipping, we use Fedex/TNT/UPS/DHL. (5~12 days for express service)
For sea shipping, we use our shipping agent, and ship from Shanghai port. (45~70 days for sea shipping)


1.Are you a manufacturer?
Yes, we are a manufacture, and we produces mainly stepper motors.

2.Where is your factory location? Can we visit your factory?
Our factory is located in Changzhou, Jiangsu. Yes, you are very welcome to visit us.

3.Can you provide free samples?
No, we don’t provide free samples. Customers won’t treat free samples fairly.

4.Who pays for shipping cost? Can I use my shipping account?
Customers pay for shipping cost. We will quote you shipping cost.
If you think you have cheaper/more convenient shipping method, we can use you shipping account.

5.What’s you MOQ? Can I order one motor?
We don’t have MOQ, and you can order only one piece sample.
But we recommend you to order a little bit more, just in case the motor is damaged during your testing, and you can have a back-up.

6.We are developing a new project, do you provide customization service? Can we sign a NDA contract?
We have over 20 years of experience in stepper motor industry.
We have developed many projects,  we can provide full set customization from design drawing to production.
We are confident we can give you few advice/suggestions for your stepper motor project.
If you are worrying about confidential issues, yes, we can sign a NDA contract.

7.Do you sell drivers? Do you produce them?
Yes, we do sell drivers. They are only suitable for temporary sample test, not suitable for mass production.
We do not produce drivers, we only produce stepper motors

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